Expression and nutritional regulation of lipogenic genes in the ruminant lactating mammary gland

Effects of nanoselenium supplementation on lactation performance, nutrient digestion and mammary gland development in dairy cows

The objective of this experiment was to evaluate the influence of nanoselenium (NANO-Se) addition on milk production, milk fatty acid synthesis, the development and metabolism regulation of mammary gland in dairy cows. Forty-eight Holstein dairy cows averaging 720 ± 16.8 kg of body weight, 66.9 ± 3.84 d in milk (dry matter intake [DIM]) and 35.2 ± 1.66 kg/d of milk production were divided into four treatments blocked by DIM and milk yields. Treatments were control group, low-Se (LSe), medium-Se (MSe) and high-Se (HSe) with 0, 0.1, 0.2 and 0.3 mg Se, respectively, from NANO-Se per kg dietary dry matter (DM). Production of energy- and fat-corrected milk (FCM) and milk fat quadratically increased (p < 0.05), while milk lactose yields linearly increased (p < 0.05) with increasing NANO-Se addition. The proportion of saturated fatty acids (SFAs) linearly decreased (p < 0.05), while proportions of monounsaturated fatty acids (MUFAs) linearly increased and polyunsaturated fatty acids (PUFAs) quadratically increased. The digestibility of dietary DM, organic matter (OM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) quadratically increased (p < 0.05). Ruminal pH quadratically decreased (p < 0.01), while total VFA linearly increased (p < 0.05) with increasing NANO-Se addition. The acetic to propionic ratio decreased (p < 0.05) linearly due to the unaltered acetic molar percentage and a quadratical increase in propionic molar percentage. The activity of CMCase, xylanase, cellobiase and pectinase increased linearly (p < 0.05) following NANO-Se addition. The activity of α-amylase increased linearly (p < 0.01) with an increase in NANO-Se dosage. Blood glucose, total protein, estradiol, prolactin, IGF-1 and Se linearly increased (p < 0.05), while urea nitrogen concentration quadratically decreased (p = 0.04). Moreover, the addition of Se at 0.3 mg/kg from NANO-Se promoted (p < 0.05) mRNA and protein expression of PPARγ, SREBP1, ACACA, FASN, SCD, CCNA2, CCND1, PCNA, Bcl-2 and the ratios of p-ACACA/ACACA and BCL2/BAX4, but decreased (p < 0.05) mRNA and protein expressions of Bax, Caspase-3 and Caspase-9. The results suggest that milk production and milk fat synthesis increased by NANO-Se addition by stimulating rumen fermentation, nutrients digestion, gene and protein expressions concerned with milk fat synthesis and mammary gland development.

Effect of Dietary Eicosapentaenoic and Docosahexaenoic Fatty Acid Supplementation during the Last Month of Gestation on Fatty Acid Metabolism and Oxidative Status in Charolais Cows and Calves

Fatty acids (FAs) are of utmost importance in the peripartal period for the development of the central nervous and immune systems of the newborn. The transport of polyunsaturated fatty acids (PUFAs) through the placenta is considered to be minimal in ruminants. Nevertheless, the cow's FAs are the main source of FAs for the calf during gestation. This research aimed to investigate the influence of low-dose eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation during late gestation on the FA metabolism of cows and their calves. A total of 20 Charolais cows during the last month of their gestation were included in the feeding trial and were divided into a control group (CON) and an experimental group (EPA + DHA). The latter received a supplement in the amount of 100 g/day (9.1 and 7.8 g/cow/day of EPA and DHA, respectively). Supplementation of low-dose EPA and DHA alters colostrum and milk fatty acid composition through the elevation of n-3 long-chain polyunsaturated fatty acids (LC-PUFAs) without affecting milk fat and protein concentrations and oxidative status. Plasma composition in cows was significantly altered, while the same effect was not detected in calf plasma. No significant change in mRNA expression was detected for the genes fatty acid synthase (FASN) and acetyl-CoA carboxylase alpha (ACACA).

MicroRNA-19a regulates milk fat metabolism by targeting SYT1 in bovine mammary epithelial cells

MicroRNAs (miRNAs) are important post-transcriptional factors involved in the regulation of gene expression and play crucial roles in biological processes related to milk fat metabolism. Our previous study revealed that miR-19a expression was significantly higher in the mammary epithelial cells of high-milk fat cows than in those of low-milk fat cows. However, the precise molecular mechanisms underlying these differences remain unclear. In this study, we found a high expression of miR-19a in the mammary tissues of dairy cows. The regulatory effects of miR-19a on bovine mammary epithelial cells (BMECs) were analyzed using cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays, which demonstrated that miR-19a significantly inhibited BMEC proliferation. Transfection of the miR-19a mimic into BMECs significantly upregulated the expression of milk fat marker genes LPL, SCAP, and SREBP1, promoting triglyceride (TG) synthesis and lipid droplet formation, whereas the miR-19a inhibitor exhibited the opposite function. TargetScan and miRWalk predictions revealed that synaptotagmin 1 (SYT1) is a target gene of miR-19a. A dual luciferase reporter gene assay, RT-qPCR, and western blot analyses revealed that miR-19a directly targets the 3'-untranslated region (UTR) of SYT1 and negatively regulates SYT1 expression. Functional validation revealed that overexpression of SYT1 in BMECs significantly downregulated the expression of LPL, SCAP, and SREBP1, and inhibited TG synthesis and lipid droplet formation. Conversely, the knockdown of SYT1 had the opposite effect. Altogether, miR-19a plays a crucial role in regulating the proliferation and differentiation of BMECs and regulates biological processes related to TG synthesis and lipid droplet formation by suppressing SYT1 expression. These findings provide a strong foundation for further research on the functional mechanisms underlying milk fat metabolism in dairy cows.

Dietary supplementation of sodium butyrate enhances lactation performance by promoting nutrient digestion and mammary gland development in dairy cows

This experiment was to evaluate the influence of sodium butyrate (SB) addition on milk production, ruminal fermentation, nutrient digestion, and the development and metabolism regulation of the mammary gland in dairy cows. Forty Holstein dairy cows averaging 710 ± 18.5 kg body weight, 72.8 ± 3.66 d in milk (DIM), and 41.4 ± 1.42 kg/d milk production were divided into four treatments blocked by DIM and milk production. Treatments were control group, low SB, medium SB, and high SB with 0, 100, 200 and 300 g/d of SB addition per cow, respectively. The study lasted for 105 d. Production of milk, milk protein and lactose quadratically increased (P < 0.05), while fat-corrected milk, energy-corrected milk and milk fat yields linearly increased (P < 0.05) with increasing SB addition. The digestibility of dietary dry matter, organic matter, and crude protein linearly increased (P < 0.05), whereas the digestibility of ether extract, neutral detergent fibre, and acid detergent fibre quadratically increased (P < 0.05). Ruminal pH quadratically decreased (P = 0.04), while total volatile fatty acids (VFA) quadratically increased (P = 0.03) with increasing SB addition. The acetic acid to propionic acid ratio increased (P = 0.03) linearly due to the unaltered acetic acid molar percentage and a linear decrease in propionic acid molar percentage. Ruminal enzymatic activity of carboxymethyl-cellulase and α-amylase, populations of total bacteria, total anaerobic fungi, total protozoa, Ruminococcus albus, R. flavefaciens, Butyrivibrio fibrisolvens, Fibrobacter succinogenes, and Ruminobacter amylophilus linearly increased (P < 0.05). Blood glucose, urea nitrogen, and non-esterified fatty acids linearly decreased (P < 0.05), while total protein concentration linearly increased (P = 0.04). Moreover, the addition of SB at 200 g/d promoted (P < 0.05) mRNA and protein expression of PPARγ, SREBF1, ACACA, FASN, SCD, CCNA2, CCND1, PCNA, Bcl-2, GPR41, and the ratios of p-Akt/Akt and p-mTOR/mTOR, but decreased (P < 0.05) mRNA and protein expressions of Bax, caspase-3, and caspase-9. The results suggest that milk production and milk fat synthesis increased with SB addition by stimulating rumen fermentation, nutrient digestion, gene and protein expressions concerned with milk fat synthesis and mammary gland development.

Review: genetic background of milk fatty acid synthesis in bovines

Milk fat composition is an important trait for the dairy industry as it directly influences the nutritional and technological properties of milk and other dairy products. The synthesis of milk fat is a complex process regulated by a network of genes. Thus, understanding the genetic variation and molecular mechanisms regulating milk fat synthesis will help to improve the nutritional quality of dairy products. In this review, we provide an overview of milk fat synthesis in bovines along with the candidate genes involved in the pathway. We also discuss de novo synthesis of fatty acids (ACSS, ACACA, FASN), uptake of FAs (FATP, FAT, LPL), intracellular activation and channelling of FAs (ACSL, FABP), elongation (EVOLV6), desaturation (SCD, FADS), formation of triglycerides (GPAM, AGPAT, LIPIN, DGAT), and milk lipid secretion (BTN1A1, XDH, PLIN2). The genetic variability of individual fatty acids will help to develop selection strategies for obtaining a healthier milk fat profile in bovines. Thus, this review will offer a potential understanding of the molecular mechanisms that regulate milk fat synthesis in bovines.

Milk Yields and Milk Fat Composition Promoted by Pantothenate and Thiamine via Stimulating Nutrient Digestion and Fatty Acid Synthesis in Dairy Cows

Considering the synergistic effect of pantothenate and thiamine on the regulation of energy metabolism, this study investigated the influences of coated calcium pantothenate (CCP) and coated thiamine (CT) on milk production and composition, nutrients digestion, and expressions of genes involved in fatty acids synthesis in mammary glands. Forty-four multiparous Chinese Holstein cows (2.8 ± 0.19 of parity, 772 ± 12.3 kg of body weight [BW], 65.8 ± 8.6 days in milk [DIM] and 35.3 ± 1.9 kg/d of milk production, mean ± SD) were blocked by parity, BW, DIM, and milk production, and they were allocated into one of four treatments in a 2 × 2 factorial block design. Additional CCP (0 mg/kg [CCP-] or 55 mg/kg dry matter [DM] of calcium pantothenate from CCP [CCP+]) and CT (0 g/kg [CT-] or 5.3 mg/kg DM of thiamine from CT [CT+]) were hand-mixed into the top one-third of total mixed ration. Both CCP and CT additives increased milk production, fat content, true protein, and lactose by promoting nutrient digestibility. The CCP or/and CT supplementation induced the elevation of C11:0, C12:0, C13:0, C14:0, C14:1, C15:0, C15:1, C16:00, C16:1, C24:00, C24:1 fatty acids, saturated fatty acid, and C4-16 fatty acid contents in milk fat; but it decreased C17-22 fatty acid content. Ruminal total VFA content was increased, but pH was decreased by both additives. The ruminal fermentation pattern was altered, and a tendency of acetate formation was implied by the increased acetate-to-propionate ratio after both additives' supplementation. The expressions of PPARγ, SREBPF1, ACACA, FASN, SCD, and FABP3 mRNAs were enhanced by CCP or CT addition, but the relative expression of LPL mRNA was upregulated by CT addition only. Additionally, blood glucose, triglyceride, insulin-like growth factor-1, and total antioxidant capacity were promoted by both additives. The combination of CCP and CT more effectively increased the ruminal total VFA concentration, the acetate to propionate ratio, and blood glucose level, and decreased ammoniacal nitrogen concentration than that achieved by CCP or CT alone. The results suggested that CCP and CT supplementation stimulated lactation performance by promoting nutrient digestion and fatty acid synthesis in the mammary glands.

Nutritional Quality of Milk Fat from Cows Fed Full-Fat Corn Germ in Diets Containing Cactus Opuntia and Sugarcane Bagasse as Forage Sources

We evaluated the performance, milk composition, and milk fatty acid profile of cows fed diets composed of cactus cladodes (Opuntia stricta [Haw.] Haw), sugarcane bagasse and increasing levels of full-fat corn germ (FFCG). We hypothesized that ground corn can be effectively replaced by FFCG when cactus cladodes and sugarcane bagasse are used as forage sources. The cows were randomly distributed into two 5 × 5 Latin Squares and fed five diets in which ground corn was progressively replaced with full-fat corn germ (FFCG; 0%, 25%, 50%, 75%, or 100% of substitution). Adding FFCG to the diet increased milk production and milk fat content and reduced milk protein content. Overall, FFCG reduced the proportion of saturated FAs and increased mono- and polyunsaturated FAs in milk, including CLA isomers. In addition, activity indices of stearoyl-CoA desaturase were reduced by increasing levels of FFCG. We conclude that the substitution of corn for FFCG in diets based on cactus cladodes and sugarcane bagasse positively modifies the FA profile of milk and could add commercial value to milk products (e.g., CLA-enriched milk). In addition, the milk fat response indicates that the basal diet was favorable to the rumen environment, preventing the trans-10 shift commonly associated with milk fat depression.

The Effect of γ-Aminobutyric Acid Addition on In Vitro Ruminal Fermentation Characteristics and Methane Production of Diets Differing in Forage-to-Concentrate Ratio

Gamma-aminobutyric acid (GABA), known as the most abundant inhibitory neurotransmitter in the mammalian brain, can permeate ruminal epithelia by passive diffusion and enrich in the rumen environment. To explore whether the addition of GABA can regulate rumen fermentation characteristics as well as methane production, a 2 × 6 factorial in vitro rumen batch culture was conducted to determine the supplemental effect of GABA at inclusion levels of 0 (Control), 10, 20, 30, 40 and 50 mg in culture fluids on rumen fermentation of two total mixed rations (HF—a high-fiber ration consisted of 70% corn silage and 30% concentrate; and LF—a low-fiber ration consisted of 30% corn silage and 70% concentrate). After 72 h in vitro incubation of two rations with mixed rumen microoganisms obtained from five rumen-cannulated lactating Holstein dairy cows, increasing GABA addition linearly increased cumulative gas production in the LF group, though in vitro dry matter digestibility was not affected in either the LF or HF group. Kinetic gas production analysis noted that increasing GABA addition mostly decreased the gas production rate (i.e., RmaxG), as well as the ration digestion rate (RmaxS) to reach maximum fermentation. The GABA addition did not affect pH or microbial growth (i.e., MCP). However, total volatile fatty acid production in both LF and HF groups all linearly increased with the increase in GABA addition. Along with the increase in GABA addition in both LF and HF groups, the ratio of non-glucogenic to glucogenic volatile fatty acids both increased, while the molar proportions of propionate and valerate were significantly decreased, and the acetate and butyrate proportions were increased after 72 h in vitro rumen fermentation. The time-course change of fermentation end-products generally showed that carbon dioxide declined from approximately 89% to 74%, and methane increased from approximately 11% to 26%. After 72 h in vitro fermentation, molar methane proportion was greater in the LF than in the HF group, and increasing GABA addition quadratically increased methane production in the LF group while a slight increase occurred in the HF group.

Effects of PUFA-Rich Dietary Strategies on Ruminants' Mammary Gland Gene Network: A Nutrigenomics Review

Although the inclusion of polyunsaturated fatty acids (PUFAs) in ruminants' diets appears to be a well-documented strategy to enrich milk with PUFAs, several gene networks that regulate milk synthesis and mammary gland homeostasis could be impaired. The objective of this literature review is to assess the effects of nutritional strategies focused on enriching milk with PUFAs on gene networks regulating mammary gland function and lipogenesis, as well as the impact of feed additives and bioactive compounds with prominent antioxidant potential on immune-oxidative transcriptional profiling, as a part of mammary gland homeostasis and health. The findings support the conclusion that PUFAs' inclusion in ruminants' diets more strongly downregulate the stearoyl-CoA desaturase (SCD) gene compared to other key genes involved in de novo fatty acid synthesis in the mammary gland. Additionally, it was revealed that seed oils rich in linoleic and linolenic acids have no such strong impact on networks that regulate lipogenic homeostasis compared to marine oils rich in eicosapentaenoic and docosahexaenoic acids. Furthermore, ample evidence supports that cows and sheep are more prone to the suppression of lipogenesis pathways compared to goats under the impact of dietary marine PUFAs. On the other hand, the inclusion of feed additives and bioactive compounds with prominent antioxidant potential in ruminants' diets can strengthen mammary gland immune-oxidative status. Considering that PUFA's high propensity to oxidation can induce a cascade of pro-oxidant incidences, the simultaneous supplementation of antioxidant compounds and especially polyphenols may alleviate any side effects caused by PUFA overload in the mammary gland. In conclusion, future studies should deeply investigate the effects of PUFAs on mammary gland gene networks in an effort to holistically understand their impact on both milk fat depression syndrome and homeostatic disturbance.

Herbage utilisation method affects rumen fluid and milk fatty acid profile in Holstein and Montbéliarde cows

Compared with maize silage- and concentrate-based diets, herbage-based diets were repeatedly shown to favourably influence the milk fatty acid (FA) profile. However, it is unclear how the herbage feeding mode (grazing vs indoor green-feeding) and conservation (fresh herbage vs hay vs silage) modify the milk FA profile. Therefore, the aim of the present experiment was to investigate the effect of different herbage utilisation methods (including herbage feeding mode and herbage conservation method) on the ruminal biohydrogenation of dietary FA and the consequences on the milk FA composition in cows of two breeds (Holstein and Montbéliarde). Concomitant effects of botanical composition and phenological stage of the herbage on milk FA profile were controlled for by harvesting barn-dried hay and silage simultaneously as first cut from the same ryegrass-dominated grassland in a semi-mountainous region. Seven weeks later, the first regrowth of the same plot was used as fresh herbage, either grazed or fed indoor (indoor green-feeding). Twenty-four Montbéliarde and 24 Holstein cows were randomly allocated to four groups of 12 cows balanced by breed, parity, and milk yield. In a free-stall barn, three groups were given ad libitum access to hay, silage, or fresh herbage, respectively. The fourth group was strip-grazing. All cows were supplemented with 3 kg DM/day of the same energy-rich concentrate. After 2 weeks of adaptation to the forage, samples of forage, concentrate, milk, blood, and rumen fluid were collected. Fatty acid composition of forages, rumen fluid, and milk was analysed by gas chromatography. Haymaking reduced total FA content of the herbage, in particular that of linoleic acid (LA) and α-linolenic acid (ALA). Still, rumen fluid lipids of hay-fed cows had the highest proportion of rumenic acid, LA, ALA, and total polyunsaturated fatty acids (PUFAs). Milk fat from hay-fed cows had the highest proportion of LA, and the apparent transfer rates from feed to milk of LA and ALA were higher in hay-fed cows than in silage-fed cows. The proportion of PUFAs was highest in milk fat from grazing and indoor green-fed Montbéliarde cows and lowest in silage-fed cows of both breeds. In conclusion, the herbage utilisation method affects the ruminal biohydrogenation of LA and ALA, whereby herbage drying particularly increases their transfer from herbage to milk.

Milk fat globule membrane proteins are involved in controlling the size of milk fat globules during conjugated linoleic acid-induced milk fat depression

Milk fat globule membrane (MFGM) proteins surround the triacylglycerol core comprising milk fat globules (MFG). We previously detected a decrease in the size of fat globules during conjugated linoleic acid (CLA)-induced milk fat depression (MFD), and other studies have reported that some MFGM proteins play a central role in regulating mammary cellular lipid droplet size. However, little is known about the relationship between MFD, MFG size, and MFGM proteins in bovine milk. The aim of this study was to investigate the profile of MFGM proteins during MFD induced by CLA. Sixteen mid-lactating Holstein cows (145 ± 24 d in milk) with similar body condition and parity were divided into control and CLA groups over a 10-d period. Cows were fed a basal diet (control, n = 8) or control plus 15 g/kg of dry matter (DM) CLA (n = 8) to induce MFD. Cow performance, milk composition, and MFG size were measured daily. On d 10, MFGM proteins were extracted and identified by quantitative proteomic analysis, and western blotting was used to verify a subset of the identified MFGM proteins. Compared with controls, supplemental CLA did not affect milk production, DM intake, or milk protein and lactose contents. However, CLA reduced milk fat content (3.73 g/100 mL vs. 2.47 g/100 mL) and the size parameters volume-related diameter D_[4,3] (3.72 μm vs. 3.35 μm) and surface area-related diameter D_[3,2] (3.13 μm vs. 2.80 μm), but increased specific surface area of MFG (1,905 m²/kg vs. 2,188 m²/kg). In total, 177 differentially expressed proteins were detected in milk from cows with CLA-induced MFD, 60 of which were upregulated and 117 downregulated. Correlation analysis showed that MFG size was negatively correlated with various proteins, including XDH and FABP3, and positively correlated with MFG-E8, RAB19, and APOA1. The results provide evidence for an important role of MFGM proteins in regulating MFG diameter, and they facilitate a mechanistic understanding of diet-induced MFD.

Feeding of palm oil fatty acids or rapeseed oil throughout lactation: Effects on mammary gene expression and milk production in Norwegian dairy goats

Lipid added as rapeseed or palm oil to the diet of dairy goats over 8 mo of one lactation alters fat secretion and milk fatty acid (FA) and protein composition. In this study, we examined the contribution of mammary gene expression to these changes and included 30 multiparous goats of Norwegian dairy goat breed for a 230-d experimental period, with indoor feeding from 1 to 120 d in milk (DIM), mountain grazing from 120 to 200 DIM, and indoor feeding from 200 to 230 DIM. After an initial period (1-60 DIM) when the control diet was given to all goats, the animals were subdivided into 3 groups of 10 goats. Treatments (60-230 DIM) were basal concentrate (control) alone or supplemented with either 8% (by weight) hydrogenated palm oil enriched with palmitic acid (POFA) or 8% (by weight) rapeseed oil (RSO). Milk was sampled individually from all animals throughout lactation, at 60, 120, 190, and 230 DIM for milk yield and composition. On d 60, 120, 190, and 230, mammary tissue was collected by biopsy to measure mRNA abundance of 19 key genes. None of the 19 genes involved in milk protein, apoptosis, lipid metabolism, transcription factors, and protein of the milk fat globule membrane, as measured by mRNA abundance, were affected by the lipid supplements, although POFA increased milk fat content, and POFA and RSO affected milk FA composition. Over the experimental period (120-230 DIM), the mRNA abundance of 13 of the 19 studied genes was affected by lactation stage. For some genes, expression either gradually increased from 120 to 230 DIM (CSN2,CASP8,CD36,GLUT4) or increased from 120 to 200 and then remained stable (XDH), or decreased (CSN3,G6PD,SREBF1,PPARG1) or increased only at 230 DIM (SCD1,SCD5,ELF3). For a second group of genes (CSN1, LALBA, FABP3, FASN, LPL, MFGE8), expression was stable over the lactation period. Our results suggest that factors other than gene expression, such as substrate availability or posttranscriptional regulation of these genes, could play an important role in the milk fat and FA responses to dietary fat composition in the goat. In conclusion, mammary gene expression in goats was more regulated by stage of lactation than by the dietary treatments applied.

CRISPR/Cas9-Induced Knockout of miR-24 Reduces Cholesterol and Monounsaturated Fatty Acid Content in Primary Goat Mammary Epithelial Cells

In nonruminants, microRNA (miRNA)-24 plays an important role in lipid metabolism in adipose tissue and the liver. Although the abundance of miR-24 in ruminant mammary glands is the highest during peak lactation, its potential role in regulating the synthesis and secretion of fat into milk is unclear. This study aimed to identify the function of miR-24 in these processes using CRISPR/Cas9 technology in primary goat mammary epithelial cells (GMEC). A single clone containing a 66-nucleotide deletion between two sgRNAs mediating double-strand break (DSB) sites was obtained. The abundance of miR-24-3p and miR-24-5p encoded by the deleted sequence was decreased, whereas the target genes INSIG1 and FASN increased. In addition, miR-24 knockout reduced the gene abundance of genes associated with fatty acid and TAG synthesis and transcription regulator. Similarly, the content of cholesterol and monounsaturated fatty acid (MUFA) C18:1 decreased, whereas that of polyunsaturated fatty acids (PUFA) C18:2, C20:3, C20:4 and C20:5 increased. Subsequently, knocking down of INSIG1 but not FASN reversed the effect of miR-24 knockout, indicating that miR-24 modulated cholesterol and fatty acid synthesis mainly by targeting INSIG1. Overall, the present in vitro data demonstrated a critical role for miR-24 in regulating lipid and fatty acid synthesis and highlighted the possibility of manipulating milk components in dairy goats.

Knockout of Stearoyl-CoA Desaturase 1 Decreased Milk Fat and Unsaturated Fatty Acid Contents of the Goat Model Generated by CRISPR/Cas9

Goat milk contains a rich source of nutrients, especially unsaturated fatty acids. However, the regulatory mechanism of milk fat and fatty acid synthesis remains unclear. Stearoyl-CoA desaturase 1 (SCD1) is the key enzyme catalyzing monounsaturated fatty acid synthesis and is essential for milk lipid metabolism. To explore milk lipid synthesis mechanism in vivo, SCD1-knockout goats were generated through CRISPR/Cas9 technology for the first time. SCD1 deficiency did not influence goat growth or serum biochemistry. Plasma phosphatidylcholines increased by lipidomics after SCD1 knockout in goats. Whole-blood RNA-seq indicated alterations in biosynthesis of unsaturated fatty acid synthesis, cAMP, ATPase activity, and Wnt signaling pathways. In SCD1-knockout goats, milk fat percentage and unsaturated fatty acid levels were reduced but other milk components were unchanged. Milk lipidomics revealed decreased triacylglycerols and diacylglycerols levels, and the differential abundance of lipids were enriched in glycerolipid, glycerophospholipids, and thermogenesis metabolism pathways. In milk fat globules, the expression levels of genes related to fatty acid and TAG synthesis including SREBP1 were reduced. ATP content and AMPK activity were promoted, and p-p70S6K protein level was suppressed in SCD1-knockout goat mammary epithelial cells, suggesting that SCD1 affected milk lipid metabolism by influencing AMPK-mTORC1/p70S6K-SREBP1 pathway. The integrative analysis of gene expression levels and lipidomics of milk revealed a crucial role of SCD1 in glycerolipids and glycerophospholipids metabolism pathways. Our observations indicated that SCD1 regulated the synthesis of milk fat and unsaturated fatty acid in goat by affecting lipid metabolism gene expression and lipid metabolic pathways. These findings would be essential for improving goat milk nutritional value which is beneficial to human health.

Regulation of Key Genes for Milk Fat Synthesis in Ruminants

Milk fat is the most important and energy-rich substance in milk and plays an important role in the metabolism of nutrients during human growth and development. It is mainly used in the production of butter and yogurt. Milk fat not only affects the flavor and nutritional value of milk, but also is the main target trait of ruminant breeding. There are many key genes involve in ruminant milk fat synthesis, including ACSS2, FASN, ACACA, CD36, ACSL, SLC27A, FABP3, SCD, GPAM, AGPAT, LPIN, DGAT1, PLIN2, XDH, and BTN1A1. Taking the de novo synthesis of fatty acids (FA) and intaking of long-chain fatty acids (LCFA) in blood to the end of lipid droplet secretion as the mainline, this manuscript elucidates the complex regulation model of key genes in mammary epithelial cells (MECs) in ruminant milk fat synthesis, and constructs the whole regulatory network of milk fat synthesis, to provide valuable theoretical basis and research ideas for the study of milk fat regulation mechanism of ruminants.

The Role of microRNAs in the Mammary Gland Development, Health, and Function of Cattle, Goats, and Sheep

Milk is an integral and therefore complex structural element of mammalian nutrition. Therefore, it is simple to conclude that lactation, the process of producing milk, is as complex as the mammary gland, the organ responsible for this biochemical activity. Nutrition, genetics, epigenetics, disease pathogens, climatic conditions, and other environmental variables all impact breast productivity. In the last decade, the number of studies devoted to epigenetics has increased dramatically. Reports are increasingly describing the direct participation of microRNAs (miRNAs), small noncoding RNAs that regulate gene expression post-transcriptionally, in the regulation of mammary gland development and function. This paper presents a summary of the current state of knowledge about the roles of miRNAs in mammary gland development, health, and functions, particularly during lactation. The significance of miRNAs in signaling pathways, cellular proliferation, and the lipid metabolism in agricultural ruminants, which are crucial in light of their role in the nutrition of humans as consumers of dairy products, is discussed.

MicroRNA-432 inhibits milk fat synthesis by targeting SCD and LPL in ovine mammary epithelial cells

The microRNA (miR)-432 is differentially expressed in the mammary gland of two breeds of lactating sheep with different milk production traits, and between the non-lactating and peak-lactation periods, but there have been no reports describing the molecular mechanisms involved. In this study, the effect of miR-432 on the proliferation of ovine mammary epithelial cells (OMECs) and the target genes of miR-432 were investigated. The effects of miR-432 on the expression of the target genes and the content of triglycerides in the OMECs were also analyzed. Transfection with a miR-432 mimic was found using CCK8 and Edu assays, to inhibit the viability of OMECs and reduce the number of proliferated OMECs. In contrast, a miR-432 inhibitor had the opposite effect to the miR-432 mimic, and together these results suggest that miR-432 inhibits the proliferation of OMECs. A dual luciferase assay revealed that the genes for stearoyl-CoA desaturase (SCD) and lipoprotein lipase (LPL) are targeted by miR-432. The transfection of miR-432 mimic into OMECs resulted in decreases in the expression of SCD and LPL, and three other milk fat synthesis marker genes; FABP4, LPIN1 and ACACA. The mimic also decreased the content of triglycerides. The miR-432 inhibitor had the opposite effect to the mimic on the expression of these genes and the level of triglycerides. This is the first study to reveal the biological mechanisms by which miR-432 inhibits milk fat synthesis in sheep.

A Narrative Review on the Unexplored Potential of Colostrum as a Preventative Treatment and Therapy for Diarrhea in Neonatal Dairy Calves

Diarrhea is the leading cause of morbidity and mortality in pre-weaned dairy calves and, as such, represents a significant animal health and welfare concern. Furthermore, digestive disease early in life is associated with several long-term consequences such as reduced growth rate and decreased milk yield during the first lactation, thus generating severe economic losses. The majority of diarrheic cases in young calves are treated with antimicrobials; however, it is necessary to develop alternative treatments, as excessive antimicrobial usage can lead to antimicrobial resistance and can negatively impact the gut microflora of a calf. Bovine colostrum is abundant in immune and bioactive factors that improve immune function and development. This rich and natural combination of immunoglobulins, natural antimicrobial factors, growth factors, anti-inflammatories and nutrients may be an attractive alternative to antimicrobials in the treatment of diarrhea in young dairy calves. There is evidence that supports the use of colostrum as an early treatment for diarrhea in young calves. Future research should investigate its therapeutic and economic effectiveness.

Consequences of herbal mixture supplementation on milk performance, ruminal fermentation, and bacterial diversity in water buffaloes

This study was aimed to evaluate the potential of a herbal mixture (HM) to improve production performance, rumen fermentation, and milk fatty acid profile in water buffaloes. Sixteen Murrah buffaloes (in four groups) were fed for 10 weeks with the same basal diet supplemented with 0 (control); 20 (HM20), 30 (HM30), and 40 (HM40) g/buffalo per day. The herbal mixture contained an equal quantity of black pepper (fruit), ginger (tubers), cinnamon (bark), peppermint (leaves), ajwain (seeds) and garlic (bulbs). After two weeks of adaptation, daily milk yield, and weekly milk composition were recorded. On the last day of the experiment, rumen contents were collected to determine rumen fermentation parameters and bacterial diversity through 16S rRNA sequencing. Results revealed no effect of treatment on dry matter intake (DMI), rumen fermentation parameters, and daily milk yield. However, milk fat (%) showed a tendency to increase (p = 0.07) in HM20 as compared with the control group. A significant increase in mono and polyunsaturated fatty acids (C14:1, C16:1, C18:2n6 and C18:3) whereas a decrease in saturated fatty acids (C18:0) in milk was observed in HM20 as compared with the control group. No significant change in bacterial diversity parameters (alpha and beta diversity) was observed in response to the treatment. Despite the substantial variation observed in the relative abundance of bacteria among treatment groups, no significant effect of treatment was observed when compared with the control group. Correlation analysis revealed several positive and negative correlations of rumen bacteria with rumen volatile fatty acids (VFA) and milk yield traits. Bacterial genera including Succinivibrionaceae, Butyrivibrio, Pseudobutyrivibrio, and Lachnospiraceae showed a positive correlation with VFA and milk yield traits. Overall, we observed 52 positive and 10 negative correlations of rumen bacteria with milk fatty acid contents. Our study revealed the potential of the herbal mixture at a lower supplemental level (20 g/day) to increase milk fat (%) and unsaturated fatty acid content in buffalo.

Effects of the circadian rhythm on milk composition in dairy cows: Does day milk differ from night milk?

Metabolism in most organisms can show variations between the day and night. These variations may also affect the composition of products derived from livestock. The aim of the present study was to investigate the difference in composition between the day milk and night milk of dairy cows. Ten multiparous Holstein cows (milk yield = 25.2 ± 5.00 kg/d) were randomly selected during mid lactation. Milk samples were collected at 0500 h ("night milk") and 1500 h ("day milk") and analyzed to determine their composition. Mid-infrared spectroscopy was used to analyze macronutrient content of milk. Metabolomics and lipidomics were used to detect and analyze small molecules and fatty acids, respectively. An automatic biochemical analyzer and ELISA kits were used to determine biochemical indicators, as well as antioxidant and immune parameters in the milk. Though milk fat, protein, lactose, and total milk solids were not different between day milk and night milk, small molecules, metabolites and lipids, and hormones and cytokines differed between day milk and night milk. Regarding biochemical and immune-related indicators, the concentrations of malondialdehyde, HSP70, and HSP90 in night milk were lower than that in day milk. However, interferon-γ levels were higher in night milk. Additionally, night milk was naturally rich in melatonin. Lipidomics analyses showed that the levels of some lipids in night milk were higher than those in day milk. Metabolomics analyses identified 36 different metabolites between day milk and night milk. Higher concentrations of N-acetyl-d-glucosamine, cis-aconitate, and d-sorbitol were observed in day milk. However, the other 33 metabolites analyzed, including carbohydrates, lipids, AA, and aromatic compounds, showed lower concentrations in day milk than in night milk. The present findings show that the composition of night milk differs considerably from that of day milk. Notable changes in the circadian rhythm also altered milk composition. These results provide evidence to support the strategic use and classification of day milk and night milk.

Effects of the Inclusion of Different Levels of Dietary Sunflower Hulls on the Colostrum Compositions of Ewes

Simple Summary

Increasing the cost of roughages, as a result of high demand by livestock producers, leads to a search for alternative sources. Plant by-products such as sunflower hulls can be used as an alternative source of fiber. This manuscript is a part of ongoing research to identify the best levels to be used without negative effects on ruminant animals’ performances.

Abstract

This study investigated the effects of supplementing different levels of sunflower hulls (SFH) to the complete feed of late-gestation pregnant ewes on the nutritive and fatty acids profile of colostrum at three and 48 h postpartum. In this study, 24 primiparous lactating Naemi ewes were randomly selected at parturition from four dietary groups as follows: (1) C (control), total mixed ration (TMR; 0% SFH), (2) S12, TMR1 with 12% SFH (level 1), (3) S20, TMR2 with 20% SFH (level 2), and (4) S28, TMR3 with 28% SFH (level 3). The body condition scores were estimated 30 days prepartum. Colostrum samples were collected at three and 48 h postpartum to measure the nutritive values and fatty acids profiles. Data were analyzed as a complete randomized design with repeated measures and via Pearson’s correlation and regression analyses. The results indicated a numerical correlation (R² = 0.42; p < 0.09) between the body condition score and both colostrum fat and total solids. SFH increased the colostrum fat % (p < 0.05), especially for S12 and S20, following a cubic trend. Additionally, the colostrum from S12 and S20 ewes had a higher proportion of unsaturated fatty acids (USFAs), omega3 and lower levels of saturated fatty acids (SFAs), other than margaric acid (C17) and stearic acid (C18), SFA/USFA, and omega 6/omega 3. Furthermore, the regression analysis of the fatty acid classes and indices indicated a quadratic relationship between the parameters and SFH levels. The results confirm that the inclusion of SFH at levels greater than 20% may have a negative effect on some fatty acid parameters as a result of the high lignin intake. In conclusion, up to 20% SFH can be used in a complete feed for pregnant ewes without negative effects on the colostrum fat content and fatty acids profiles.

LC-MS/MS Based Metabolomics Reveal Candidate Biomarkers and Metabolic Changes in Different Buffalo Species

Consumers have shown more and more interest in high-quality and healthy dairy products and buffalo milk is commercially more viable than other milks in producing superior dairy products due to its higher contents of fat, crude protein, and total solids. Metabolomics is one of the most powerful strategies in molecular mechanism research however, little study has been focused on the milk metabolites in different buffalo species. Therefore, the aim of this study was to explore the underlying molecular mechanism of the fatty synthesis and candidate biomarkers by analyzing the metabolomic profiles. Milk of three groups of buffaloes, including 10 Mediterranean, 12 Murrah, and 10 crossbred buffaloes (Murrah × local swamp buffalo), were collected and UPLC-Q-Orbitrap HRMS was used to obtain the metabolomic profiles. Results showed that milk fatty acid in Mediterranean buffalo was significantly higher than Murrah buffalo and crossbred buffalo. A total of 1837/726 metabolites was identified in both positive and negative electrospray ionization (ESI±) mode, including 19 significantly different metabolites between Mediterranean and Murrah buffalo, and 18 different metabolites between Mediterranean and crossbred buffalo. We found 11 of the different metabolites were both significantly different between Mediterranean vs. Murrah group and Mediterranean vs crossbred group, indicating that they can be used as candidate biomarkers of Mediterranean buffalo milk. Further analysis found that the different metabolites were mainly enriched in fat synthesis related pathways such as fatty acid biosynthesis, unsaturated fatty acid biosynthesis, and linoleic acid metabolism, indicating that the priority of different pathways affected the milk fat content in different buffalo species. These specific metabolites may be used as biomarkers in the identification of milk quality and molecular breeding of high milk fat buffalo.

Effect of Soybean Oil Supplementation on Milk Production, Digestibility, and Metabolism in Dairy Goats under Thermoneutral and Heat Stress Conditions

Simple Summary

Heat stress (HS) not only reduces milk yield but also depresses its contents of fat and protein, which might negatively impact cheese making. Dietary supplementation with soybean oil (SBO) could increase milk fat and improve milk fatty acid (FA) profiles in dairy goats. In the present study dairy goats were exposed to thermoneutral (TN; 15 to 20 °C) or HS (12 h/d at 37 °C and 12 h/d at 30 °C) conditions. In each ambient temperature, goats were fed a control diet (CON) or the same diet supplemented with SBO. Goats in HS suffered depressed feed intake and milk production, but they had greater digestibility coefficients compared to TN goats. Regardless of the HS treatment, goats supplemented with SBO produced milk with greater contents of fat, monounsaturated FA, and conjugated linoleic acid, without any negative effects on milk protein content. In conclusion, dietary supplementation with soybean oil was a useful strategy to increase milk fat and improve its fatty acid profile. Both TN and HS goats responded to soybean oil supplementation similarly since the interaction between soybean oil supplementation and temperature treatment was not significant.

Abstract

In a previous work, we observed that heat-stressed goats suffer reductions in milk yield and its contents of fat and protein. Supplementation with soybean oil (SBO) may be a useful strategy to enhance milk quality. In total, eight multiparous Murciano–Granadina dairy goats (42.8 ± 1.3 kg body weight; 99 ± 1 days of lactation) were used in a replicated 4 × 4 Latin square design with four periods; 21 d each (14 d adaptation, 5 d for measurements and 2 d transition between periods). Goats were allocated to one of four treatments in a 2 × 2 factorial arrangement. Factors were no oil (CON) or 4% of soybean oil (SBO), and controlled thermal neutral (TN; 15 to 20 °C) or heat stress (HS; 12 h/d at 37 °C and 12 h/d at 30 °C) conditions. This resulted in four treatment combinations: TN-CON, TN-SBO, HS-CON, and HS-SBO. Compared to TN, HS goats experienced lower (p < 0.05) feed intake, body weight, N retention, milk yield, and milk protein and lactose contents. However, goats in HS conditions had greater (p < 0.05) digestibility coefficients (+5.1, +5.2, +4.6, +7.0, and +8.9 points for dry matter, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber, respectively) than TN goats. The response to SBO had the same magnitude in TN and HS conditions. Supplementation with SBO had no effects on feed intake, milk yield, or milk protein content. However, SBO supplementation increased (p < 0.05) blood non-esterified fatty acids by 50%, milk fat by 29%, and conjugated linoleic acid by 360%. In conclusion, feeding 4% SBO to dairy goats was a useful strategy to increase milk fat and conjugated linoleic acid without any negative effects on intake, milk yield, or milk protein content. These beneficial effects were obtained regardless goats were in TN or HS conditions.

Metabolic and behavior changings during the transition period as predictors of calving proximity and welfare of dairy goats

This Research aimed to evaluate the metabolic status and behavior changes during the transition period in dairy goats from three breeds, under tropical conditions. Thirty multiparous female goats were kept in pens, distributed randomly by breeds. Infrared cameras were fitted in the pens to monitor the animals, and its activities were recorded. Goats displayed varied idle, standing, walking, and feeding behaviors at kidding day (P < 0.10) when compared with the days after and before. Agnostic interactions prevailed between 3.33 and 7.98% of the time on the day of kidding. There was a day effect for the exploratory activities (P < 0.10), where the most exploratory activities were observed on the day of kidding. The milk production and fat content differed according to breed and lactation week. Collective pens for lactating goats, kept in a tropical environment, do not compromise the social behavior and welfare.

Effect of acetate, β-hydroxybutyrate and their interaction on lipogenic gene expression, triglyceride contents and lipid droplet formation in dairy cow mammary epithelial cells

The purpose of this study was to assess the effects of acetate and β-hydroxybutyrate alone or in combination on lipogenic genes and their associated regulatory proteins in dairy cow mammary epithelial cells (DCMEC) using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blotting, lipid droplet staining and a triglyceride content detection kit, to determine whether SCFA are related to milk fat synthesis regulation in DCMEC. Our experiment shows that addition of different concentrations of acetate, β-hydroxybutyrate and their combinations to DCMEC increase in relative mRNA abundance of lipogenic genes and key transcription factors suggest an increase in lipogenic capacity, which is supported by an increased in cytosolic triglyceride content. Similarly, the protein expression level of acetyl-coenzyme A carboxylase (ACACA), fatty acid synthase (FASN) and sterol-coenzyme desaturase-1 (SCD1) genes and the transcription factor sterol regulatory element-binding protein-1 (SREBP1) were found to be increased by addition of acetate, β-hydroxybutyrate and their combinations. The expression pattern of fat-related genes and proteins showed similar trends in almost all treatments, suggesting that common transcription factor are regulating these genes. These results show that acetate and β-hydroxybutyrate regulate fat synthesis, further confirming that SCFAs work by targeting genes to activate the SREBP1 and insulin-induced gene 1 protein (INSIG1) signalling pathways in DCMEC.

Uterine, vaginal and placental blood flows increase with dynamic changes in serum metabolic parameters and oxidative stress across gestation in buffaloes

The aims of the present study were to determine uterine, vaginal and placental blood flows by Doppler ultrasound cross-buffalo gestation and to evaluate the relationships among reproductive Doppler parameters and serum metabolic parameters as well as oxidative stress. Uterine (UA) and vaginal (VA) arteries were scanned every month, and placentome was scanned from month 4 till 8 in gestation. Time-averaged maximum velocity (TAMV), pulsatility index (PI), resistance index (RI), systolic/diastolic ratio (SD) and arterial diameter (AD) were used for accessing UA and VA hemodynamics. Time-averaged maximum velocity positively correlated with and AD, and both negatively correlated with their PI, RI and SD in UA and VA. TAMV and AD increased constantly in pregnancy, with maximum increase in months 4 and 9. Pulsatility index, RI and AD of UA decreased between months 4 and 9, while PI, RI and AD of VA decreased between months 5 and 9 and then increased in month 10 in pregnancy. Time-averaged maximum velocity of placentome blood flow increased exponentially from months 4 to 8, but decreased at the last two months in pregnancy. Serum lipids were significantly higher in the first month compared to all other months, while glucose was significantly lower in months 9 and 10. Malondialdehyde increased from month 3 till term, but peaked in month 5 and 10. Glutathione and catalase were highest in the first month and remained after. Time-averaged maximum velocity and AD for both UA and VA negatively correlated with serum lipids, glucose, catalase and glutathione, while positively correlated with malondialdehyde and total protein. Thus, increases in uterine blood flow (UtBF), vaginal blood flow (VaBF) and placental blood flow (PaBF) are associated with increased metabolism and oxidative stress in buffalo pregnancy.

Phytogenic Additives Can Modulate Rumen Microbiome to Mediate Fermentation Kinetics and Methanogenesis Through Exploiting Diet-Microbe Interaction

Ruminants inhabit the consortia of gut microbes that play a critical functional role in their maintenance and nourishment by enabling them to use cellulosic and non-cellulosic feed material. These gut microbes perform major physiological activities, including digestion and metabolism of dietary components, to derive energy to meet major protein (65-85%) and energy (ca 80%) requirements of the host. Owing to their contribution to digestive physiology, rumen microbes are considered one of the crucial factors affecting feed conversion efficiency in ruminants. Any change in the rumen microbiome has an imperative effect on animal physiology. Ruminal microbes are fundamentally anaerobic and produce various compounds during rumen fermentation, which are directly used by the host or other microbes. Methane (CH4) is produced by methanogens through utilizing metabolic hydrogen during rumen fermentation. Maximizing the flow of metabolic hydrogen in the rumen away from CH4 and toward volatile fatty acids (VFA) would increase the efficiency of ruminant production and decrease its environmental impact. Understanding of microbial diversity and rumen dynamics is not only crucial for the optimization of host efficiency but also required to mediate emission of greenhouse gases (GHGs) from ruminants. There are various strategies to modulate the rumen microbiome, mainly including dietary interventions and the use of different feed additives. Phytogenic feed additives, mainly plant secondary compounds, have been shown to modulate rumen microflora and change rumen fermentation dynamics leading to enhanced animal performance. Many in vitro and in vivo studies aimed to evaluate the use of plant secondary metabolites in ruminants have been conducted using different plants or their extract or essential oils. This review specifically aims to provide insights into dietary interactions of rumen microbes and their subsequent consequences on rumen fermentation. Moreover, a comprehensive overview of the modulation of rumen microbiome by using phytogenic compounds (essential oils, saponins, and tannins) for manipulating rumen dynamics to mediate CH4 emanation from livestock is presented. We have also discussed the pros and cons of each strategy along with future prospective of dietary modulation of rumen microbiome to improve the performance of ruminants while decreasing GHG emissions.

Variation in the stearoyl-CoA desaturase gene (SCD) and its influence on milk fatty acid composition in late-lactation dairy cattle grazed on pasture

Gene markers have become useful tools for improving animal genetics and breeding since they improve the accuracy of selection for superior breeding stock. In this study, the stearoyl-CoA desaturase (Δ-9-desaturase) gene (SCD) was investigated in New Zealand pasture-grazed Holstein–Friesian × Jersey cows. Three nucleotide substitutions were identified in exon 5 of the gene (c.702A/G, c.762T/C and c.878C/T), and a single nucleotide substitution was identified in intron 5 (c.880+105A/G). The c.878C/T substitution would, if expressed, result in the amino acid substitution p.A293V. Four nucleotide substitutions (c.*1783A/G, c.*1883C/T, c.*1984G/A and c.*2066T/C/G) were identified in the 3′-untranslated region (3′-UTR), and these resulted in three nucleotide sequence variants (named a, b and c). The sequence that would encode valine (V) at position 293 of SCD was linked to 3′-UTR variant a, and the sequence that would encode alanine (A) was linked to variants b and c. The frequency of the genotypes was as follows: VV (equivalent to aa: 15.1 %), VA (equivalent to ab+ac: 50.0 %) and AA (equivalent to bb+cc+bc: 34.9 %). The cows with the V variant produced less C10:1, C12:1 and C14:1 fatty acid (FA) but more C10:0, C11:0, C14:0, C16:1 and C18:2 FA than the A variant cows (P<0.001). Effects of c.*1783A/G and c.*2066T/C/G on milk fat composition were also found for the AA cows. The presence of c was associated with decreased levels of C16:1 (P<0.001), C17:1 (P=0.001), C18:2 cis-9, trans-13 (P=0.045), C18:2 cis-9, trans-12 (P=0.018) FA and C16:1 FA index (P<0.001). The presence of b was associated with increased levels of C13:0 iso FAs (P<0.001), monounsaturated FA (MUFA; P=0.002) and C12:1 (P<0.001).

Effects of exogenous C18 unsaturated fatty acids on milk lipid synthesis in bovine mammary epithelial cells

We determined the effects of a combination of C18 unsaturated fatty acids (C18-UFAs) consisting of oleic, linoleic, and linolenic acids on milk lipogenesis in bovine mammary epithelial cells (BMECs). By orthogonal experiments to determine cellular triacylglycerol (TAG) accumulation, a combination of 200 μmol/l C18 : 1, 50 μmol/l C18 : 2, and 2 μmol/l C18 : 3 was selected as C18-UFAs combination treatment, and culture in medium containing fatty acid-free bovine serum albumin was used as the control. The expression of genes related to milk lipid synthesis and intracellular FA composition was measured. The results showed that cytosolic TAG formation was higher under C18-UFAs treatment than under control treatment. The mRNA expression of acetyl-CoA carboxylase-α (ACACA), fatty acid synthase (FASN), and peroxisome proliferator-activated receptor gamma (PPARG) did not differ between treatments. The abundance of stearoyl-CoA desaturase (SCD) and acyl-CoA synthetase long-chain family member 1 (ACSL1) was higher, whereas that of sterol regulatory element binding transcription factor 1 (SREBF-1) was lower after C18-UFAs treatment compared to control treatment. The C16 : 0 and SFA content was decreased following C18-UFAs treatment compared to control treatment, while the cis-9 C18 : 1 and UFA content was increased. In conclusion, C18-UFAs could stimulate triglyceride accumulation, increase the cellular UFA concentration, and regulate lipogenic genes in BMECs.

The protective effect of selenium on the lipopolysaccharide-induced oxidative stress and depressed gene expression related to milk protein synthesis in bovine mammary epithelial cells

The objective of this study was to determine the effects of selenium (Se) on antioxidative function and the synthesis of milk protein in bovine mammary epithelial cells (BMECs). Two experiments were conducted using a single-factor completely randomized design study. In part I, BMECs were randomly divided into seven groups: control (without Se) and six Se treatments (10, 20, 50, 100, 150, and 200 nmol/L). In part II, based on the results of part I, we used lipopolysaccharide (LPS) as the induced stress source to analyze the protective effect of Se on LPS-induced oxidative damage and the influence on milk protein synthesis of BMECs. BMECs were randomly divided into eight groups: control (without Se and LPS), LPS treatment (only LPS), and six Se treatments with LPS (LS10 to LS200). Treatment of BMECs with Se was found to significantly improve cell proliferation and antioxidant function. LPS could induce oxidative damage which significantly inhibited cell proliferation and antioxidant function in BMECs. Se had a protective effect on the oxidative damage of BMECs induced by LPS. Additionally, our results indicated that LPS damage downregulated the gene expression of milk protein synthesis. Se effectively relieved the inhibition due to LPS-induced oxidative damage on the synthesis of milk protein, and Se concentrations of 50 to 200 nmol/L showed the best effect. In conclusion, Se at concentrations of 50 to 100 nmol/L is better for antioxidant function but had no effect on milk protein synthesis in healthy BMECs. Se ameliorated the damage caused by LPS-induced by improving levels of antioxidant markers and upregulating milk protein synthesis and the expression of genes associated with milk protein in BMECs.

Adipose Tissue Modification through Feeding Strategies and Their Implication on Adipogenesis and Adipose Tissue Metabolism in Ruminants

Dietary recommendations by health authorities have been advising of the importance of diminishing saturated fatty acids (SFA) consumption and replacing them by polyunsaturated fatty acids (PUFA), particularly omega-3. Therefore, there have been efforts to enhance food fatty acid profiles, helping them to meet human nutritional recommendations. Ruminant meat is the major dietary conjugated linoleic acid (CLA) source, but it also contains SFA at relatively high proportions, deriving from ruminal biohydrogenation of PUFA. Additionally, lipid metabolism in ruminants may differ from other species. Recent research has aimed to modify the fatty acid profile of meat, and other animal products. This review summarizes dietary strategies based on the n-3 PUFA supplementation of ruminant diets and their effects on meat fatty acid composition. Additionally, the role of n-3 PUFA in adipose tissue (AT) development and in the expression of key genes involved in adipogenesis and lipid metabolism is discussed. It has been demonstrated that linseed supplementation leads to an increase in α-linolenic acid (ALA) and eicosapentaenoic acid (EPA), but not in docosahexaenoic acid (DHA), whilst fish oil and algae increase DHA content. Dietary PUFA can alter AT adiposity and modulate lipid metabolism genes expression, although further research is required to clarify the underlying mechanism.

Fatty acid biosynthesis and transcriptional regulation of Stearoyl-CoA Desaturase 1 (SCD1) in buffalo milk

Background

Buffalo milk is considered as a highly nutritious food owing to its higher contents of fatty acids (FA) and rich nutrient profile. Higher fat contents of buffalo milk make it suitable for processing to develop various healthy and nutritious products. Moreover, buffalo milk contains more unsaturated FAs (UFA) such as oleic and linolenic acid, which are important from the human health point of view owing to their desirable physiological effects. However, inadequate information is available about the chemical composition and mechanism of FA synthesis in buffalo milk. In this study, we hypothesized that expression of SCD1 gene could alter the biosynthesis of FA in epithelial cells of mammary gland and subsequently affect the FA contents in buffalo milk. We investigated the transcriptional and biological role of Stearoyl-CoA Desaturase 1 (SCD1) in the buffalo mammary epithelial cells (BMECs) during FA and triacylglycerol (TAG) synthesis.

Results

Results revealed that unsaturated fatty acid contents were much higher in concentration in buffalo milk as compared to Holstein cow. Significant increase in the expression level of FAS, ACACA, SREBP1, PPARG, GPAT, and AGPAT genes was observed in response to altered expression of SCD1 in buffalo milk. Moreover, change in SCD1 gene in BMECs also mediated the expression of genes related to FA biosynthesis subsequently leading to alter the FA composition. Overexpression of SCD1 significantly increased the expression of genes associated with FA and TAG synthesis leading to enhance FA and unsaturated FA contents in BMECs. However, down-regulation of SCD1 exhibited opposite consequences.

Conclusion

Our study provides mechanistic insights on transcriptional regulation of SCD1 to alter FA and TAG synthesis through directly or indirectly mediating biosynthesis and metabolic pathways in BMECs. We provide preliminary findings regarding engineering of FA contents in buffalo milk through SCD1 signaling.

Effect of all-trans retinoic acid on casein and fatty acid synthesis in MAC-T cells

Objective

Caseins and fatty acids of milk are synthesized and secreted by the epithelial cells of the mammary gland. All-trans retinoic acid (ATRA), an active metabolite of vitamin A, has been shown to promote mammary development. This study was conducted to determine the effect of ATRA on casein synthesis and fatty acid composition in MAC-T cells.

Methods

MAC-T cells were allowed to differentiate for 4 d, treated with ATRA (0, 1.0, 1.5, and 2.0 μM), and incubated for 3 d. We analyzed the fatty acid composition, the mRNA expression of casein and fatty acid synthesis-related genes, and the phosphorylation of casein synthesis-related proteins of MAC-T cells by gas chromatography, quantitative polymerase chain reaction, and western blotting, respectively.

Results

In MAC-T cells, ATRA increased the mRNA levels of α_S1-casein and β-casein, janus kinase 2 (JAK2) and E74-like factor 5 of the signal transducer and activator of transcription 5 β (STAT5-β) pathway, ribosomal protein S6 kinase beta-1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1 of the mammalian target of rapamycin (mTOR) pathway, inhibited the mRNA expression of phosphoinositide 3-kinase and eukaryotic initiation factor 4E of the mTOR pathway, and promoted the phosphorylation of STAT5-β and S6K1 proteins. Additionally, ATRA increased the de novo synthesis of fatty acids, reduced the content of long-chain fatty acids, the ratio of monounsaturated fatty acids to saturated fatty acids (SFA), the ratio of polyunsaturated fatty acids (PUFA) to SFA, and the ratio of ω-6 to ω-3 PUFA. The mRNA levels of acetyl-CoA carboxylase 1, fatty acid synthase, lipoprotein lipase, stearoyl-CoA desaturase, peroxisome proliferator-activated receptor gamma, and sterol regulatory element-binding protein 1 (SREBP1) were enhanced by ATRA.

Conclusion

ATRA promotes the synthesis of casein by regulating JAK2/STAT5 pathway and downstream mTOR signaling pathway, and it improves the fatty acid composition of MAC-T cells by regulating SREBP1-related genes.

Effects of Free Fatty Acids with Different Chain Lengths and Degrees of Saturability on the Milk Fat Synthesis in Primary Cultured Bovine Mammary Epithelial Cells

How short-chain fatty acids (FAs) affect cell membrane morphology and milk fat biosynthesis in mammary epithelial cells (MECs) is yet unclear. This study investigated the primary bovine MEC response to different FAs. We observed that the cell surface ultrastructures were influenced by chain length and degree of saturability of FAs. The CD36, FATP1, and FABP3 gene expression was affected independent of the type of FA. FASN, LPIN1, PPARα, and PPARγ transcripts were more sensitive to the short-chain FAs (acetic and β-hydroxybutyric acids). Furthermore, short-chain FAs inclined to regulate FA degradation-, elongation-, and metabolism-associated pathways, while long-chain FAs (stearic and trans-10,cis-12 conjugated linolenic acids) modulated extracellular matrix-receptor interaction-, transcriptional misregulation-, microRNA-, and ribosome biogenesis-related pathways. However, triacylglycerol accumulation in the cytoplasm was not changed by all of the FAs. Overall, FAs with different chain lengths and degrees of saturability could differentially alter primary bovine MEC cell morphology and influence protein profiles involved in milk fat synthesis pathways.

Lysine Enhances the Stimulation of Fatty Acids on Milk Fat Synthesis via the GPRC6A-PI3K-FABP5 Signaling in Bovine Mammary Epithelial Cells

Amino acids can enhance milk fat synthesis in bovine mammary epithelial cells (BMECs), but the molecular mechanism is not well-known. In this study, we explored the regulatory role and molecular mechanism of lysine (Lys) on milk fat synthesis induced by fatty acids (FAs). We show that Lys dose-dependently affects number of cells and milk fat synthesis, and has more stimulatory effects in the presence of FAs. Lys enhances FA-induced sterol regulatory element binding protein 1c (SREBP-1c) expression and maturation in a fatty-acid-binding protein 5 (FABP5)-dependent manner. We further show that the Lys stimulates FABP5 expression via the GPRC6A (GPCR, class C, group 6, subtype A)-PI3K (phosphatidylinositol 3-kinase) signaling. Lys dose-dependently affects GPRC6A expression and localization at the plasma membrane. In summary, our data reveals that Lys enhances FAs-stimulated SREBP-1c expression and maturation leading to milk fat synthesis via the GPRC6A-PI3K-FABP5 signaling in BMECs.

Effect of Breed on Transcriptional and Protein Expression of Lipogenic Enzymes in Tail and Subcutaneous Adipose Tissue from Two Grazing Breeds of Lambs

Simple Summary

An experiment to determine the effect of sheep breed on subcutaneous fatty acid composition was carried out at the Butalcura Research Station, Chiloé, Chile. To this end, two breeds of lambs were challenged to graze a typical, naturalized pasture of the Chiloé Archipelago, Chile, from 60 d to 120 d after birth. The animals were sacrificed to collect samples from subcutaneous fat (SCF) from the back, and tail fat (TF) to determine the effect of breed on transcriptional expression of lipogenic enzymes and fatty acid profile in these two fat depots. The results showed that although mRNA expression of enzymes was similar in both breeds, there were differences in certain protein levels in the SCF, partially related with the fatty acid profiles, thus affecting the selection of lamb breed either for human consumption or experimental purposes.

Abstract

This experiment was carried out to determine the effect of breed on mRNA and protein expression levels of lipogenic enzymes acetyl-CoA carboxylase α (ACC), fatty acid synthase (FAS), stearoyl-CoA desaturase 1 (SCD1) plus sterol regulatory element binding transcription factor 1c (SREBP1c) in the subcutaneous fat (SCF) from the back of the animal, and tail fat (TF) of both Chilota and Suffolk Down lambs grazing Calafatal. Eight Chilota and six Suffolk Down 2-month-old male lambs were allocated to graze a “Calafatal”, a typical secondary succession of Chiloé Archipelago, Chile. After 62 d, lambs were slaughtered according to Chile’s meat industry standards. Fatty acid profile, RT-qPCR, and Western blot analyses from SCF and TF samples were performed. Although the mRNA expression levels of ACC, FAS, SCD1 and SREBP1c in SCF did not differ significantly between breeds (p > 0.05), a trend to higher mRNA expression of FAS and SREBP1c in TF from Chilota lambs was observed (p = 0.06). On the other hand, FAS levels in SCF were higher in Chilota than in Suffolk Down lambs (p < 0.02), although Suffolk Down showed higher fat contents and saturated fatty acid (SFA) proportions than Chilota lambs (p < 0.01). The FAS protein expression in TF was similar in both breeds (p > 0.05). Although the fat content was higher in Suffolk Down than in Chilota lambs (p < 0.01), the SFA proportions were similar in both breeds. Finally, it can be concluded that although mRNA expression of enzymes was similar in both breeds, there were differences in some protein levels in the SCF, partially related with the fatty acid profiles, thus affecting the selection of lamb breed either for human consumption or experimental purposes.

Milk saturated fatty acids, odd- and branched-chain fatty acids, and isomers of C18:1, C18:2, and C18:3n-3 according to their duodenal flows in dairy cows: A meta-analysis approach

We sought to establish predictive response models of milk fatty acid (FA) yields or concentrations from their respective duodenal flow, rumen digestive parameters, or diet characteristics in dairy cows, with a special focus on cis and trans isomers of C18:1, C18:2, odd- and branched FA, and mammary de novo synthesized FA. This meta-analysis was carried out using data from trials with nature of forage, percentage of concentrate, supplementation of diets with vegetable oils or seeds, and marine products' animal fats as experimental factors. The data set included 34 published papers representing 50 experiments with 142 treatments. Increasing duodenal C18 FA flow induced a quadratic increase in milk total C18 yield and a linear decrease in milk C4:0 to C14:0 concentration. Intra-experimental predictive response models of individual milk cis C18:1 isomers (Δ 11 to 15 position) from their respective duodenal flows had coefficients of determination (R²) ranging from 0.74 to 0.99, with root mean square error varying from 0.19 to 0.96 g/d, 0.02 to 0.10% of total FA, and 0.03 to 0.29% of C18 FA. Models predicting milk trans C18:1 isomer yields or concentrations had R² greater than 0.90 (except for trans-4 and trans-10 C18:1) with root mean square error varying from less than 0.1 to 5.2 g/d. Linear regressions for C18:2n-6, trans-10,cis-12 CLA, and trans-11,trans-13 CLA were calculated according to their respective duodenal flows. Quadratic models of milk C18:3n-3 yield or concentration from its duodenal flow had R² values above 0.97. Models of amounts desaturated from C18:0 into cis-9 C18:1 and trans-11 C18:1 into cis-9,trans-11 CLA indicated that the contribution of C18:0 and trans-11 C18:1 desaturation to respective cis-9 C18:1 and cis-9,trans-11 CLA yields in milk fat was 83.8% (±0.75) and 86.8% (±2.8). Furthermore, when cows were fed marine products, our results could indicate a lower mammary uptake of C18:0 and trans-11 C18:1 in proportion to their respective duodenal flow, with no associated change in mammary Δ⁹-desaturase activity. Yields or concentrations of C15:0, C17:0, iso-C15:0, iso-C17:0, anteiso-C15:0, and anteiso-C17:0 were dependent on their respective duodenal flow or concentration at duodenum, but synthesis of these FA from C3 units for linear-chain odd FA, and from C2 units for branched-chain FA was suggested, respectively. Several milk C18 FA concentrations were closely related to their duodenal concentrations with slopes of the linear models close to the bisector; this could reflect a priority for the use of these duodenal C18 FA by the mammary gland to favor their high concentration in plasma triglycerides and nonesterified FA, which are preferentially taken up by the mammary gland.

Regulation of Stearoyl-Coenzyme A Desaturase 1 by trans-10, cis-12 Conjugated Linoleic Acid via SREBP1 in Primary Goat Mammary Epithelial Cells

trans-10, cis-12 Conjugated linoleic acid (t10c12-CLA) is a biohydrogenation intermediate in the rumen that inhibits mammary fatty acid de novo synthesis in lactating dairy goats. However, the underlying molecular pathways in milk-lipid metabolism affected by t10c12-CLA are not completely understood. The present study investigated the lipid-regulation mechanisms in goat mammary epithelial cells (GMECs) in response to t10c12-CLA. Gene-expression analysis indicated sterol-regulatory-element-binding transcription factor1 ( SREBF1) and its putative target gene stearoyl-CoA desaturase ( SCD1) were down-regulated (fold changes of 0.33 ± 0.04, P < 0.05, and 0.19 ± 0.01, P < 0.01, respectively). Concentrations of cellular palmitoleic acid (C16:1) and oleic acid (C18:1) were decreased (1.12 ± 0.05 vs 1.69 ± 0.11% and 15.70 ± 0.44 vs 24.97 ± 0.82%, respectively, P < 0.01), whereas those of linoleic acid (C18:2) were increased (5.00 ± 0.14 vs 3.81 ± 0.25%, P < 0.05); the desaturation indices of C16 and C18 were decreased in response to t10c12-CLA treatment (6.90 ± 0.05 vs 8.00 ± 0.30% and 61.41 ± 0.65 vs 67.73 ± 1.33%, respectively, P < 0.05). A luciferase-activity assay indicated that deletion of the sterol-response-element (SRE) site and the nuclear-factor (NF-Y) site in the SCD1-promoter region (-511/+65 bp) suppressed the regulatory effect of t10c12-CLA. Overexpression of SREBF1 partly counteracted the inhibitory effect of t10c12-CLA on de novo fatty acid synthesis. Overall, t10c12-CLA causes an inhibition of fatty acid synthesis and desaturation and regulates SCD1 expression by affecting the binding of SREBP1 protein to the SRE and NF-Y sites.

Prepartum fatty acid supplementation in sheep. II. Supplementation of eicosapentaenoic acid and docosahexaenoic acid during late gestation alters the fatty acid profile of plasma, colostrum, milk and adipose tissue, and increases lipogenic gene expression of adipose tissue

The objectives of this study were as follows: 1) to establish whether feeding a source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to ewes during late gestation changes the fatty acid profile of colostrum, milk, ewe adipose tissue, and plasma and subsequently lamb plasma and red blood cells (RBC), and 2) to investigate the effects of EPA and DHA on mRNA expression in ewe adipose tissue. Eighty-four gestating ewes (28 pens, three per pen) were blocked by lambing day and assigned to a diet with an addition of fat at 0.39% of the DM during the last 50 d of gestation using Ca salts of a palm fatty acid distillate (PFAD) high in palmitic and oleic acids or EPA + DHA. Blood samples were taken from ewes on days 20, 1 (parturition), and 30 and from lambs on days 1 and 30 for plasma fatty acid analysis. Fatty analysis of lamb RBC was performed on day 1. Colostrum samples were taken at lambing and milk samples on day 30 for fatty acid analysis. Subcutaneous adipose tissue biopsies were taken from one ewe per pen on day 20 for fatty acid analysis and gene expression analysis of 27 genes. Treatment × day interactions (P < 0.10) were observed for several isomers of C18:1, with concentrations that were greater in plasma of EPA + DHA ewes on day 20, but were not different on day 1 or 30. Plasma concentrations of EPA tended to be greater (P = 0.07), whereas DHA was greater (P < 0.001) in EPA + DHA ewes compared with PFAD ewes. There was no difference in EPA or DHA in adipose tissue with EPA + DHA vs. PFAD supplementation (P > 0.10). Concentrations of fatty acids with 6 to 10 carbons were significantly increased (P < 0.05) in colostrum and milk of EPA + DHA ewes. There was a treatment × day interaction with EPA + DHA ewes yielding greater EPA (P = 0.03) and DHA (P = 0.04) concentrations than PFAD in colostrum, but not in milk. Treatment × day interactions (P < 0.05) were observed for several C18:1 isomers with concentrations that were greater in EPA + DHA ewe colostrum, but were not different between treatments in milk. In lamb plasma and RBC, EPA and DHA were not different between treatments (P > 0.10). The expression of fatty acid synthase and leptin was significantly increased (P < 0.05), whereas the expression of diacylglycerol acyltransferase 2 tended to be increased (P = 0.08) by supplementation of EPA + DHA vs. PFAD. These results suggest that supplementation with EPA and DHA to ewes during late gestation alters the fatty acid profile of plasma, colostrum, and milk and may increase lipogenesis.

Multi-criteria evaluation of dairy cattle feed resources and animal characteristics for nutritive and environmental impacts

On-farm nutrition and management interventions to reduce enteric CH4 (eCH4) emission, the most abundant greenhouse gas from cattle, may also affect volatile solids and N excretion. The objective was to jointly quantify eCH4 emissions, digestible volatile solids (dVS) excretion and N excretion from dairy cattle, based on dietary variables and animal characteristics, and to evaluate relationships between these emissions and excreta. Univariate and Bayesian multivariate mixed-effects models fitted to 520 individual North American dairy cow records indicated dry matter (DM) intake and dietary ADF and CP to be the main predictors for production of eCH4 emissions and dVS and N excreta (g/day). Yields (g/kg DM intake) of eCH4 emissions and dVS and N excreta were best predicted by dietary ADF, dietary CP, milk yield and milk fat content. Intensities (g/kg fat- and protein-corrected milk) of eCH4, dVS and N excreta were best predicted by dietary ADF, dietary CP, days in milk and BW. A K-fold cross-validation indicated that eCH4 and urinary N variables had larger root mean square prediction error (RMSPE; % of observed mean) than dVS, fecal N and total N production (on average 24.3% and 26.5% v. 16.7%, 15.5% and 16.2%, respectively), whereas intensity variables had larger RMSPE than production and yields (29.4%, 14.7% and 14.6%, respectively). Univariate and multivariate equations performed relatively similar (18.8% v. 19.3% RMSPE). Mutual correlations indicated a trade-off for eCH4 v. dVS yield. The multivariate model indicated a trade-off between eCH4 and dVS v. total N production, yield and intensity induced by dietary CP content.

Review: Modulating ruminal lipid metabolism to improve the fatty acid composition of meat and milk. Challenges and opportunities

Growth in demand for foods with potentially beneficial effects on consumer health has motivated increased interest in developing strategies for improving the nutritional quality of ruminant-derived products. Manipulation of the rumen environment offers the opportunity to modify the lipid composition of milk and meat by changing the availability of fatty acids (FA) for mammary and intramuscular lipid uptake. Dietary supplementation with marine lipids, plant secondary compounds and direct-fed microbials has shown promising results. In this review, we have compiled information about their effects on the concentration of putative desirable FA (e.g. c9t11-CLA and vaccenic, oleic, linoleic and linolenic acids) in ruminal digesta, milk and intramuscular fat. Marine lipids rich in very long-chain n-3 polyunsaturated fatty acids (PUFA) efficiently inhibit the last step of C18 FA biohydrogenation (BH) in the bovine, ovine and caprine, increasing the outflow of t11-18:1 from the rumen and improving the concentration of c9t11-CLA in the final products, but increments in t10-18:1 are also often found due to shifts toward alternative BH pathways. Direct-fed microbials appear to favourably modify rumen lipid metabolism but information is still very limited, whereas a wide variety of plant secondary compounds, including tannins, polyphenol oxidase, essential oils, oxygenated FA and saponins, has been examined with varying success. For example, the effectiveness of tannins and essential oils is as yet controversial, with some studies showing no effects and others a positive impact on inhibiting the first step of BH of PUFA or, less commonly, the final step. Further investigation is required to unravel the causes of inconsistent results, which may be due to the diversity in active components, ruminant species, dosage, basal diet composition and time on treatments. Likewise, research must continue to address ways to mitigate negative side-effects of some supplements on animal performance (particularly, milk fat depression) and product quality (e.g. altered oxidative stability and shelf-life).

Diets supplemented with starch and corn oil, marine algae, or hydrogenated palm oil differentially modulate milk fat secretion and composition in cows and goats: A comparative study

A direct comparative study of dairy cows and goats was performed to characterize the animal performance and milk fatty acid (FA) responses to 2 types of diets that induce milk fat depression in cows as well as a diet that increases milk fat content in cows but for which the effects in goats are either absent or unknown. Twelve Holstein cows and 12 Alpine goats, all multiparous, nonpregnant, and at 86 ± 24.9 and 61 ± 1.8 DIM, respectively, were allocated to 1 of 4 groups and fed diets containing no additional lipid (CTL) or diets supplemented with corn oil [5% dry matter intake (DMI)] and wheat starch (COS), marine algae powder (MAP; 1.5% DMI), or hydrogenated palm oil (HPO; 3% DMI), according to a 4 × 4 Latin square design with 28-d experimental periods. Dietary treatments had no significant effects on milk yield and DMI in both species, except for COS in cows, which decreased DMI by 17%. In cows, milk fat content was lowered by COS (-45%) and MAP (-22%) and increased by HPO (13%) compared with CTL, and in goats only MAP had an effect compared with CTL by decreasing milk fat content by 15%. In both species, COS and MAP lowered the yields (mmol/d per kg of BW) of <C16 and C16 FA. With COS, this decrease was compensated by an increase of >C16 FA in goats, but not in cows, and the >C16 FA yield decreased with MAP in both species. HPO supplementation increased the milk yield of C16 FA in cows. Compared with CTL, COS induced an increase of trans-10,cis-12 conjugated linoleic acid by 18 fold in cows and 7 fold in goats and of trans-10 18:1 by 13 fold in cows and 3 fold in goats. Moreover, other conjugated linoleic acid isomers, such as trans-10,trans-12 and trans-7,cis-9, were increased to a greater extent in cows (8 and 4 fold, respectively) compared with goats (4 and 2 fold, respectively) on the COS treatment. In both species, the responses to MAP were characterized by a decrease in the milk concentration of 18:0 (3 fold, on average) and cis-9 18:1 (2 fold, on average) combined with a 3-fold increase in the total trans 18:1, with an increase in trans-10 18:1 only observed in cows. Compared with CTL, the response to HPO was distinguished by an increase in 16:0 (10%) in cows. This comparative study clearly demonstrated that each ruminant species responds differently to COS and HPO treatments, whereas MAP caused similar effects, and that goats are less sensitive than cows to diets that induce a shift from the trans-11 toward the trans-10 ruminal pathways.

Transcriptional regulation of milk lipid synthesis by exogenous C16:0 and C18 fatty acids in bovine mammary epithelial cells

The objective of this study was to examine the effects of removing one fatty acid from a combination of long-chain fatty acids (LCFA) on milk lipogenesis in bovine mammary epithelial cells. The incubation concentration of LCFA was determined, and 100 μmol L−1 of C16:0, 5 μmol L−1 of C18:0, 100 μmol L−1 of cis-9 C18:1, 25 μmol L−1 of n-6 C18:2, and 1.2 μmol L−1 of n-3 C18:3 were used in the study. Treatments were C16:0, C18:0, C18:1, C18:2, and C18:3 combinations as control; control absent of C16:0 as A-C16:0; control absent of C18:0 as A-C18:0; control absent of C18:1 as A-C18:1; control absent of C18:2 as A-C18:2; control absent of C18:3 as A-C18:3. Results showed that compared with control, fatty acid synthetase expression was reduced by A-C18:0 and A-C18:1. Palmitic acid decreased expression of lipoprotein lipase. Compared with control, the expression of stearoyl-coenzyme A desaturase-1 and cluster of differentiation 36 was reduced by all treatments. Peroxisome proliferator-activated receptor-α expression was down-regulated by A-C16:0, A-C18:0, A-C18:1, and A-C18:2. Sterol regulatory element binding factor-1 was decreased when treated with A-C18:0, A-C18:1, and A-C18:2. Cells lack of 18-carbon fatty acid synthesized lower amount of intracellular triglyceride compared with control.

Characterisation of gene expression related to milk fat synthesis in the mammary tissue of lactating yaks

This research communication describes the profile of gene expression related to the synthesis of yak milk as determined via quantitative reverse transcription polymerase chain reaction (RT-qPCR). Significant up-regulation during lactation were observed in genes related to fatty acid (FA) uptake from blood (LPL, CD36), intracellular FA transport (FABP3), intracellular FA activation of long- and short-chain FAs (ACSS1, ACSS2, ACSL1), de novo synthesis (ACACA), desaturation (SCD), triacyglycerol (TAG) synthesis (AGPAT6, GPAM, LPIN1), lipid droplet formation (PLIN2, BTN1A1, XDH), ketone body utilisation (BDH1, OXCT1), and transcription regulation (THRSP, PPARGC1A). In particular, intracellular de novo FA synthesis (ACSS2, ACACA, and FABP3) and TAG synthesis (GPAM, AGPAT6, and LPIN1), whose regulation might be orchestrated as part of the gene network under the control of SERBF1 in the milk fat synthesis process, were more activated compared to levels in dairy cows. However, the genes involved in lipid droplet formation (PLIN2, XDH, and BTN1A1) were expressed at lower levels compared to those in dairy cows, where these genes are mainly controlled by the PPARG regulator.

Effects of branched-chain volatile fatty acids on lactation performance and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows

Branched-chain volatile fatty acids (BCVFA) supplements could promote lactation performance and milk quality by improving ruminal fermentation and milk fatty acid synthesis. This study was conducted to evaluate the effects of BCVFA supplementation on milk performance, ruminal fermentation, nutrient digestibility and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows. A total of 36 multiparous Chinese Holstein cows averaging 606±4.7 kg of BW, 65±5.2 day in milk (DIM) with daily milk production of 30.6±0.72 kg were assigned to one of four groups blocked by lactation number, milk yield and DIM. The treatments were control, low-BCVFA (LBCVFA), medium-BCVFA (MBCVFA) and high-BCVFA (HBCVFA) with 0, 30, 60 and 90 g BCVFA per cow per day, respectively. Experimental periods were 105 days with 15 days of adaptation and 90 days of data collection. Dry matter (DM) intake tended to increase, but BW changes were similar among treatments. Yields of actual milk, 4% fat corrected milk, milk fat and true protein linearly increased, but feed conversion ratio (FCR) linearly decreased with increasing BCVFA supplementation. Milk fat content linearly increased, but true protein content tended to increase. Contents of C4:0, C6:0, C8:0, C10:0, C12:0, C14:0 and C15:0 fatty acids in milk fat linearly increased, whereas other fatty acids were not affected with increasing BCVFA supplementation. Ruminal pH, ammonia N concentration and propionate molar proportion linearly decreased, but total VFA production and molar proportions of acetate and butyrate linearly increased with increasing BCVFA supplementation. Consequently, acetate to propionate ratios linearly increased. Digestibilities of DM, organic matter, CP, NDF and ADF also linearly increased. In addition, mRNA expressions of peroxisome proliferator-activated receptor γ, sterol regulatory element-binding factor 1 and fatty acid-binding protein 3 linearly increased, mRNA expressions of acetyl-coenzyme A carboxylase-α, fatty acid synthase and stearoyl-CoA desaturase quadratically increased. However, lipoprotein lipase mRNA expression was not affected by treatments. The results indicated that lactation performance and milk fat synthesis increased with BCVFA supplementation by improving ruminal fermentation, nutrient digestibility and mRNA expressions of genes related to milk fat synthesis.

Sunflower oil supplementation affects the expression of miR-20a-5p and miR-142-5p in the lactating bovine mammary gland

Oil supplementation in dairy cattle diets is used to modulate milk fat composition, as well as the expression of mammary lipogenic genes, whose regulation remains unclear. MiRNAs are small non-coding RNA considered as crucial regulators of gene expression, offering clues to explain the mechanism underlying gene nutriregulation. The present study was designed to identify miRNAs whose expression in the cow mammary gland is modulated by sunflower oil supplementation. MiRNomes were obtained using RNAseq technology from the mammary gland of lactating cows receiving a low forage diet, supplemented or not with 4% sunflower oil. Among the 272 miRNAs characterized, eight were selected for RT-qPCR validations, showing the significant down-regulation of miR-142-5p and miR-20a-5p by sunflower supplementation. These two miRNAs are predicted to target genes whose expression was reported as differentially expressed by sunflower supplementation. Among their putative targets, ELOVL6 gene involved in lipid metabolism has been studied. However, a first analysis did not show its significant down-regulation, in response to the over-expression of miR-142-5p, of miR-20a-5p, or both, in a bovine mammary epithelial cell line. However, a clearer understanding of the miRNA expression by lipid supplementation would help to decipher the regulation of lactating cow mammary gland in response to nutrition.

Dairy system, parity, and lactation stage affect enteric methane production, yield, and intensity per kilogram of milk and cheese predicted from gas chromatography fatty acids

Ruminants (and milk production) contribute to global climate change through enteric methane emissions (EME), and any attempt to reduce them is complicated by the fact that they are difficult and expensive to measure directly. In the case of dairy cows, a promising indirect method of estimating EME is to use the milk fatty acid profile as a proxy, as a relationship exists between microbial activity in the rumen and the molecules available for milk synthesis in the mammary gland. In the present study, we analyzed the detailed fatty acid profiles (through gas chromatography) of a large number of milk samples from 1,158 Brown Swiss cows reared on 85 farms with the aim of testing in the field 2 equations for estimating EME taken from a published meta-analysis. The average estimated methane yield (CH₄ emission per kg of dry matter intake, 21.34 ± 1.60 g/kg) and methane intensity (per kg of corrected milk, 14.17 ± 1.78 g/kg), and the derived methane production (CH₄ emissions per day per cow, 357 ± 109 g/d) were similar to those previously published. Using data from model cheese makings from individual cows, we also calculated estimated methane intensity per kilogram of fresh cheese (99.7 ± 16.4 g/kg) and cheese solids (207.5 ± 30.9 g/kg). Dairy system affected all EME estimates. Traditional dairy farms, and modern farms including corn silage in the TMR exhibited greater estimated methane intensities. We found very wide variability in estimated EME traits among different farms within dairy system (0.33 to 0.61 of total variance), suggesting the need to modify the farms' feeding regimens and management practices to mitigate emissions. Among the individual factors, parity order affected all estimated EME traits excepted methane yield, with an increase from first lactation to the following ones. Lactation stage exhibited more favorable estimated EME traits during early lactation, concomitant with the availability of nutrients from body tissue mobilization for mammary synthesis of milk. Our results showed a coherence between the EME traits estimated from the analysis of milk fatty acids and the expectations according to current knowledge. Further research is needed to validate the results obtained in this study in other breeds and populations, to assess the magnitude of the genetic variation and the potential of these phenotypes to be exploited in breeding programs with the aim to mitigate emissions.