Expression of genes related to energy metabolism and the unfolded protein response in dairy cow mammary cells is affected differently during dietary supplementation with energy from protein and fat

Non-Synonymous Variants in Fat QTL Genes among High- and Low-Milk-Yielding Indigenous Breeds

The effect of breed on milk components-fat, protein, lactose, and water-has been observed to be significant. As fat is one of the major price-determining factors for milk, exploring the variations in fat QTLs across breeds would shed light on the variable fat content in their milk. Here, on whole-genome sequencing, 25 differentially expressed hub or bottleneck fat QTLs were explored for variations across indigenous breeds. Out of these, 20 genes were identified as having nonsynonymous substitutions. A fixed SNP pattern in high-milk-yielding breeds in comparison to low-milk-yielding breeds was identified in the genes GHR, TLR4, LPIN1, CACNA1C, ZBTB16, ITGA1, ANK1, and NTG5E and, vice versa, in the genes MFGE8, FGF2, TLR4, LPIN1, NUP98, PTK2, ZTB16, DDIT3, and NT5E. The identified SNPs were ratified by pyrosequencing to prove that key differences exist in fat QTLs between the high- and low-milk-yielding breeds.

Immune and metabolic effects of rumen-protected methionine during a heat stress challenge in lactating Holstein cows

Multiparous, lactating Holstein cows (n = 32) were randomly assigned to one of two dietary treatments [TMR with rumen-protected Met (RPM) or TMR without RPM (CON)], and within each dietary treatment group cows were randomly assigned to one of two environmental treatment groups in a split-plot crossover design. In phase 1 (9 d), all cows were fed ad libitum and in thermoneutral conditions (TN). In phase 2 (9 d), group 1 (n = 16) was exposed to a heat stress (HS) challenge (HSC). Group 2 cows (n = 16) were pair-fed (PFTN) to HSC counterparts and remained in TN. After a 21-d washout period, the study was repeated (period 2) and the environmental treatments were inverted relative to treatments from phase 2 of period 1, while dietary treatments remained the same for each cow. During phase 1, cows in RPM had greater plasma Met concentration compared with cows in CON (59 and 30 µM, respectively; P < 0.001). Cows in PFTN had a greater decrease (P < 0.05) in plasma insulin than cows in HSC at 4 h (-2.7 µIU/mL vs. -0.7 µIU/mL) and 8 h (-7.7 µIU/mL vs. -0.4 µIU/mL) during phase 2. Compared with cows in PFTN, cows in HSC had an increase (P < 0.05) in plasma serum amyloid A (-59 µg/mL vs. +58 µg/mL), serum haptoglobin (-3 µg/mL vs. +33 µg/mL), plasma lipopolysaccharide binding protein (-0.27 and +0.11 µg/mL), and plasma interleukin-1β (-1.9 and +3.9 pg/mL) during phase 2. In conclusion, HSC elicited immunometabolic alterations; however, there were limited effects of RPM on cows in HSC.

Effects of Paper Mulberry Silage on the Growth Performance, Rumen Microbiota and Muscle Fatty Acid Composition in Hu Lambs

Paper mulberry (Broussonetia papyrifera) is widely ensiled to feed sheep in southwestern China, as unconventional woody forage. Feeding lambs with paper mulberry silage (PMS) may improve certain feeding characteristics, thereby affecting the growth performance and meat quality. The aim of this study is to investigate the effects of four diets of PMS on growth performance, rumen microbial composition, and muscle fatty acids profile in Hu lambs. The results showed that 30% and 40% PMS increased the dry matter intake and average daily gain of Hu lambs compared to the control group. PMS30 and PMS40 increased the content of C24:1, and PMS40 increased the content of C20:5n-3. The content of microbial protein (MCP) was higher in PMS40 than in others, but PMS30 and PMS40 reduced the total volatile fatty acid in rumen. PMS30 significantly increased the ratio of acetic acid to propionic acid. The abundance of ruminal Christensenellaceae_R-7_group and norank_f_Eubacterium_coprostanoligenes_group was significantly higher in PMS30 and PMS40 groups. Moreover, Christensenellaceae_R-7_group had a significant positive correlation with n3-polyunsaturated fatty acid. PMS40 might lead to a relatively high content of unsaturated fatty acids in longissimus dorsi muscle by increasing the relative abundance of Christensenellaceae_R-7_group in rumen.

Effects of metabolizable protein concentration, amino acid profile, and fiber source on the messenger RNA expression of skeletal muscle in peripartum dairy cows

After parturition, dairy cows mobilize AA from skeletal muscle to meet metabolizable protein (MP) requirements. High mobilization may compromise cow health and longer-term milk production. Postpartum diets with higher MP concentrations, improved AA profiles, or MP increased at the expense of forages rather than nonforage fiber sources may attenuate muscle catabolism; however, the molecular mechanisms responsible need investigation. We evaluated mRNA expression in the longissimus dorsi of cows fed postpartum diets differing in MP concentration, AA profile, and fiber source. From 0 to 25 d after parturition, 40 multiparous cows received the following diets: (1) 13% deficient in MP (D-MP), (2) adequate in MP using primarily soy protein (A-MP), (3) adequate in MP using blends of proteins and individual AA to improve the AA profile (Blend), or (4) similar to Blend except additional protein replaced forage (Blend-fNDF). Biopsies were taken approximately -5, 7, and 25 d relative to parturition. Greater dietary MP concentration (D-MP vs. A-MP and Blend) decreased expression of genes related to protein synthesis (MTOR, RPS6KB1) and degradation (FOXO1), inflammation (IFNG, TLR4), and endoplasmic reticulum (ER) stress (HSPA5, DDIT) and increased genes associated with lipogenesis (PPARG) and glucose oxidation (LDH, MB). In Blend versus A-MP (i.e., effect of AA profile), expression related to apoptosis (CASP8) and inflammation (TNFA) decreased and genes associated with cell cycle progression (E2F1) and fast-twitch glycolytic muscle fiber type (MYH4) increased. Less forage (Blend-fNDF vs. Blend) decreased genes associated with lipogenesis (PPARG, ACACA) and ER stress (BCL2, DDIT3, EIF2AK3, PPP1R15A) and increased genes associated with inflammation (TNF), inhibition of myogenesis (MSTN), and autophagy (PEBP1). In summary and based on mRNA expression, increasing MP supply may attenuate muscle turnover and ER stress. However, an unbalanced AA supply reduced cell cycle progression and protein synthesis. Lower energy supplies may reduce cell growth and cause autophagy.

Comparison of Metabolic Alterations in Serum and Milk Whey Between Inactive Ovaries and Estrus Dairy Cows

Inactive ovaries (IOs) affect the estrus cycle and timed artificial insemination (TAI) efficiency in dairy cows during early lactation. The objective of the experiment was to determine metabolic changes in the serum and milk whey of dairy cows with IO and estrus. Twenty-eight healthy postpartum Holstein cows in similar age, milk production, and body condition were selected at 30 days postpartum for tracking to 70 days postpartum, and estrus performance was recorded through Afi Farm® software. The ovarian status and follicular diameter of dairy cows were examined by an experienced breeder through B-ultrasound and rectal examination. Fourteen normal estrus cows were allocated to control group A and 14 cows with IO to group B, all at 30–70 days postpartum. The serum and milk whey in the two groups of cows at 70 days postpartum were used for non-targeted nuclear magnetic resonance (¹H-NMR) analysis to measure the different metabolites of cows with IO. In group B compared with group A at 70 days postpartum, there was an increase in the milk whey of six different metabolites including succinate, creatine phosphate, glycine, myo-inositol, glycolate, and orotate and a decrease in the milk whey of seven metabolites, including alanine, creatinine, o-phosphorylcholine, lactose, taurine, galactose, and glucose-1-phosphate. There was an increase in the serum of group B cows of four differential metabolites, including 3-hydroxybutyrate, acetate, glutamine, and glycine and a decrease in the serum of nine differential metabolites, including alanine, succinate, citrate, creatinine, o-phosphocholine, glucose, myo-inositol, tyrosine, and histidine compared with group A. Group B cows with IO had decreased glucose metabolism and impaired tricarboxylic acid cycle, increased lipid mobilization, and abnormal amino acid metabolism. The study provides a potential prevention strategy for IO in dairy cows in future.

The market for amino acids: understanding supply and demand of substrate for more efficient milk protein synthesis

For dairy production systems, nitrogen is an expensive nutrient and potentially harmful waste product. With three quarters of fed nitrogen ending up in the manure, significant research efforts have focused on understanding and mitigating lactating dairy cows’ nitrogen losses. Recent changes proposed to the Nutrient Requirement System for Dairy Cattle in the US include variable efficiencies of absorbed essential AA for milk protein production. This first separation from a purely substrate-based system, standing on the old limiting AA theory, recognizes the ability of the cow to alter the metabolism of AA. In this review we summarize a compelling amount of evidence suggesting that AA requirements for milk protein synthesis are based on a demand-driven system. Milk protein synthesis is governed at mammary level by a set of transduction pathways, including the mechanistic target of rapamycin complex 1 (mTORC1), the integrated stress response (ISR), and the unfolded protein response (UPR). In tight coordination, these pathways not only control the rate of milk protein synthesis, setting the demand for AA, but also manipulate cellular AA transport and even blood flow to the mammary glands, securing the supply of those needed nutrients. These transduction pathways, specifically mTORC1, sense specific AA, as well as other physiological signals, including insulin, the canonical indicator of energy status. Insulin plays a key role on mTORC1 signaling, controlling its activation, once AA have determined mTORC1 localization to the lysosomal membrane. Based on this molecular model, AA and insulin signals need to be tightly coordinated to maximize milk protein synthesis rate. The evidence in lactating dairy cows supports this model, in which insulin and glucogenic energy potentiate the effect of AA on milk protein synthesis. Incorporating the effect of specific signaling AA and the differential role of energy sources on utilization of absorbed AA for milk protein synthesis seems like the evident following step in nutrient requirement systems to further improve N efficiency in lactating dairy cow rations.

Effects of 25-hydroxycholecalciferol supplementation in maternal diets on reproductive performance and the expression of genes that regulate lactation in sows

One hundred Yorkshire × Landrace sows were randomly assigned to one of two dietary treatments (diet ND: 6,000 IU vitamin D₃ /d feed; diet 25-D: 200 μg/day 25OHD₃ feed). The experiment began on d 90 of gestation and continued until weaning on day 21 of lactation. In sows that received 25OHD₃ , the growth rate of the piglets before weaning was significantly accelerated (0.266 kg/day, p < .05). Sow serum was collected after weaning, and those in the 25OHD₃ group were found to have significantly higher serum calcium (CA) and phosphorus (PI) levels (p < .05). Interestingly, the oestrus cycle of sows fed 25OHD₃ was significantly shortened (p < .05), the oestrus time was concentrated on the fifth day after weaning, and the piglets were born with a higher degree of uniformity (p < .05). Colostrum was collected on the day of delivery, and the colostrum of sows fed 25OHD₃ contained higher milk fat content than the control group (p < .05). 25OHD₃ supplementation increased the mRNA and protein expression of INSIG1 and SREBP1, which regulate milk fat synthesis, in the mammary gland of lactating sows (p < .05). In conclusion, 25OHD₃ supplementation in maternal diets improved reproductive performance, milk fat content and the mRNA and protein levels of genes regulating milk fat synthesis in lactating sows.

Effects of fatty acids on inducing endoplasmic reticulum stress in bovine mammary epithelial cells

Fatty acids play important roles in the regulation of endoplasmic reticulum (ER) stress-induced apoptosis in different cells. Currently, the effects of fatty acids on bovine mammary epithelial cells (MEC) remain unknown. Our study examined bovine MEC viability and measured unfolded protein response (UPR)-related gene and protein expressions following fatty acid treatments. To evaluate the role of fatty acids, we treated MAC-T cells (a line of MEC) with 100 to 400 μM of saturated (palmitic and stearic acid) and unsaturated (palmitoleic, oleic, linoleic, and linolenic acid) fatty acids and 1 to 5 mM of short- and medium-chain fatty acids (acetic, propionic, butyric, and octanoic acid). Thereafter, we determined UPR-related gene expression using quantitative real-time PCR. Palmitic acid stimulated expression of XBP1s, ATF4, ATF6A, and C/EBP homologous protein (CHOP). Stearic acid increased expression of XBP1s and CHOP and decreased expression of ATF4 and ATF6A. Results of Western blot analysis and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed that palmitic and stearic acid reduced MAC-T cell viability and induced extreme ER stress by increasing the protein expression of ER stress markers, such as phospho-PKR-like endoplasmic reticulum kinase, phospho-eIF2α, cleaved CASP-3, and CHOP. Among unsaturated long-chain fatty acids, palmitoleic acid increased expression of ATF4 and ATF6A. Oleic acid increased expression of XBP1s, ATF4, and ATF6A. Linoleic and linolenic acids increased expression of XBP1s, ATF4, and ATF6A but decreased expression of XBP1s and ATF6A at the highest dose. Although palmitoleic, oleic, and linoleic acid decreased CHOP expression, only palmitoleic acid increased MAC-T cell viability. Therefore, unsaturated long-chain fatty acids did not induce severe ER stress. Acetic, propionic, and butyric acids decreased expression of ATF4, ATF6A, and CHOP and increased XBP1s expression. Although only octanoic acid increased ATF4 and ATF6A expressions, it lowered expression of XBP1s and CHOP. Although fatty acid treatment did not increase the levels of ER stress proteins, butyric and octanoic acids reduced cell viability, possibly because of early differentiation. These results suggest that saturated fatty acids play important roles in MEC viability by inducing severe ER stress compared with unsaturated fatty acids. In addition, acetic and propionic acids (short- and medium-chain fatty acids) reduced ER stress. Therefore, the present study reflects the new insight that serum fatty acid concentration plays an important role in maintaining the lactation physiology of dairy cows.

Impact of post-ruminally infused macronutrients on bovine mammary gland expression of genes involved in fatty acid synthesis, energy metabolism, and protein synthesis measured in RNA isolated from milk fat

Background

Characterising the regulation of milk component synthesis in response to macronutrient supply is critical for understanding the implications of nutritional interventions on milk production. Gene expression in mammary gland secretory cells was measured using RNA isolated from milk fat globules from 6 Holstein-Friesian cows receiving 5-d abomasal infusions of saline, essential amino acids (AA), or glucose (GG) or palm olein (LG) without (LAA) or with (HAA) essential AA, according to a 6 × 6 Latin square design. RNA was isolated from milk fat samples collected on d 5 of infusion and subjected to real-time quantitative PCR. We hypothesised that mRNA expression of genes involved in de novo milk fatty acid (FA) synthesis would be differently affected by GG and LG, and that expression of genes regulating transfer of tricarboxylic acid cycle intermediates would increase at the HAA level. We also hypothesised that the HAA level would affect genes regulating endoplasmic reticulum (ER) homeostasis but would not affect genes related to the mechanistic target of rapamycin complex 1 (mTORC1) or the integrated stress response (ISR) network.

Results

Infusion of GG did not affect de novo milk FA yield but decreased expression of FA synthase (FASN). Infusion of LG decreased de novo FA yield and tended to decrease expression of acetyl-CoA carboxylase 1 (ACC1). The HAA level increased both de novo FA yield and expression of ACC1, and tended to decrease expression of mitochondrial phosphoenolpyruvate carboxykinase (PCK2). mRNA expression of mTORC1 signaling participants was not affected by GG, LG, or AA level. Expression of the ε subunit of the ISR constituent eukaryotic translation initiation factor 2B (EIF2B5) tended to increase at the HAA level, but only in the presence of LG. X-box binding protein 1 (XBP1) mRNA was activated in response to LG and the HAA level.

Conclusions

Results show that expression of genes involved in de novo FA synthesis responded to glucogenic, lipogenic, and aminogenic substrates, whereas genes regulating intermediate flux through the tricarboxylic acid cycle were not majorly affected. Results also suggest that after 5 d of AA supplementation, milk protein synthesis is supported by enhanced ER biogenesis instead of signaling through the mTORC1 or ISR networks.