Effects of fat sources in sow on the fatty acid profiles and fat globule size of milk and immunoglobulins of sows and piglets

Impact of dietary fat levels and fatty acid composition on milk fat synthesis in sows at peak lactation

BACKGROUND

Dietary fat is important for energy provision and immune function of lactating sows and their progeny. However, knowledge on the impact of fat on mammary transcription of lipogenic genes, de novo fat synthesis, and milk fatty acid (FA) output is sparse in sows. This study aimed to evaluate impacts of dietary fat levels and FA composition on these traits in sows. Forty second-parity sows (Danish Landrace × Yorkshire) were assigned to 1 of 5 dietary treatments from d 108 of gestation until weaning (d 28 of lactation): low-fat control diet (3% added animal fat); or 1 of 4 high-fat diets with 8% added fat: coconut oil (CO), fish oil (FO), sunflower oil (SO), or 4% octanoic acid plus 4% FO (OFO). Three approaches were taken to estimate de novo milk fat synthesis from glucose and body fat.

RESULTS

Daily intake of FA was lowest in low-fat sows within fat levels (P < 0.01) and in OFO and FO sows within high-fat diets (P < 0.01). Daily milk outputs of fat, FA, energy, and FA-derived carbon reflected to a large extent the intake of those. On average, estimates for de novo fat synthesis were 82 or 194 g/d from glucose according to method 1 or 2 and 255 g de novo + mobilized FA/d according to method 3. The low-fat diet increased mammary FAS expression (P < 0.05) and de novo fat synthesis (method 1; P = 0.13) within fat levels. The OFO diet increased de novo fat synthesis (method 1; P < 0.05) and numerically upregulated mammary FAS expression compared to the other high-fat diets. Across diets, a daily intake of 440 g digestible FA minimized milk fat originating from glucose and mobilized body fat.

CONCLUSIONS

Sows fed diets with low-fat or octanoic acid, through upregulating FAS expression, increased mammary de novo fat synthesis whereas the milk FA output remained low in sows fed the low-fat diet or high-fat OFO or FO diets, indicating that dietary FA intake, dietary fat level, and body fat mobilization in concert determine de novo fat synthesis, amount and profiles of FA in milk.

Role of functional fatty acids in modulation of reproductive potential in livestock

Fatty acids are not only widely known as energy sources, but also play important roles in many metabolic pathways. The significance of fatty acids in modulating the reproductive potential of livestock has received greater recognition in recent years. Functional fatty acids and their metabolites improve follicular development, oocyte maturation and embryo development, as well as endometrial receptivity and placental vascular development, through enhancing energy supply and precursors for the synthesis of their productive hormones, such as steroid hormones and prostaglandins. However, many studies are focused on the impacts of individual functional fatty acids in the reproductive cycle, lacking studies involved in deeper mechanisms and optimal fatty acid requirements for specific physiological stages. Therefore, an overall consideration of the combination and synergy of functional fatty acids and the establishment of optimal fatty acid requirement for specific stages is needed to improve reproductive potential in livestock.

Dynamics of fatty acid and non-volatile polar metabolite profiles in colostrum and milk depending on the lactation stage and parity number of sows

The objective of this study was to investigate the impact of lactation stage and parity number on fatty acid and non-volatile polar metabolite profiles in sow colostrum and milk using a metabolomics approach. A total number of 63 colostrum, transient and mature milk were collected from primiparous and multiparous Landrace × Yorkshire crossbred sows. Macrochemical, fatty acid and non-volatile polar metabolite compositions of samples were analyzed using infrared spectrometry, gas chromatography coupled with mass-spectrometry and proton nuclear magnetic resonance spectroscopy, respectively. Univariate and multivariate statistical analysis demonstrated significant impacts of lactation stage and parity number on colostrum and milk compositions. Chemometric analysis revealed significant influences of sow parity on the distinction in fatty acid profiles of mature milk while the distinction in non-volatile polar metabolite profiles was more evident in colostrum. Alterations in the concentration of linoleic (C18:2n6), lignoceric (C24:0), behenic (C22:0), caprylic (C8:0) and myristoleic (C14:1) acid together with those of creatine, creatinine phosphate, glutamate and glycolate were statistically suggested to be mainly affected by sow parity number. Variations in the concentration of these compounds reflected the physiological function of sow mammary gland influenced. This information could be applied for feed and feeding strategies in lactating sows and improving lactating performances.

Evaluation of Fatty Acid Distributions and Triacylglycerol Species in Sow Milk and Commercial Piglet Formulas: A Comparative Study Based on Fat Sources and Lactation Stages

Total fatty acid and sn-2 fatty acid compositions, and triacylglycerol (TAG) species in 130 sow colostrum, 100 sow milk, and 22 piglet formula samples were analyzed in the present study. Significant differences were found in concentrations of medium chain-saturated fatty acids (MC-SFAs) and distributions of palmitic acid (P) and oleic (O)/linoleic (L) acid. The levels of MC-SFAs in sow colostrum and sow milk fats (2.4-3.1%) were significantly lower than those in piglet formulas (7.9-27.2%). Approximately 63% of palmitic acid was located at the sn-2 position in both sow colostrum and milk fats, which was significantly higher than in piglet formula fats (21.1-39.1%). Correspondingly, only 17.8-28.3% of oleic and linoleic acids were at the sn-2 position in sow milk fats, contributing to their typical triacylglycerol structure in sow colostrum and milk, whose palmitic acid connected to the sn-2 position and unsaturated fatty acids located at the sn-1,3 positions. Sow colostrum, milk, and piglet formulas were notably distinguished into three groups based on their fatty acids and TAGs, among which triacylglycerols were the most differentiated index. A total of 51 TAG species (including their isomers) differed significantly between sow colostrum and milk and piglet formulas. OPL and OPO were the most important differentiating TAGs. The large amount of sn-2 esterified palmitic acid plays a key role in improving the absorption of fat and calcium. The results provide suggestions for design of sow milk fat equivalents.

Triacylglycerol fingerprint of sow milks during different lactation stages and from different breeds

Sow milk fats not only provide energy but also essential nutrients for piglets. Thus, feeding strategies must be aligned with fat composition, especially triacylglycerols (TAGs) and their isomers. The triacylglycerol (TAG) profiles of sow milk fats from five typical breeds (Landrace × Large White, Landrace, Large White, Duroc, Pietrain) and two lactation stages (colostrum and milk) were systematically studied. A total of 45 major TAG species were identified using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. The most abundant TAG was oleic acid-palmitic acid-linoleic acid (O-P-L) (13.92% and 12.03% in colostrum and milk, respectively), which was not significantly different in colostrum among all breeds. TAG composition of sow milk was affected mainly by the lactation stage rather than sow breed. Furthermore, TAG compositions of sow milk fats were similar to those of human milk fats, but significant differences were observed between commercial piglet formulas and sow milk. Therefore, the results will contribute to the optimization of piglet formulas to improve the growth and wellness of piglets, as well as potentially providing a basis for food usage as a new source of nutrients for human infants in future.

Importance of Breed, Parity and Sow Colostrum Components on Litter Performance and Health

The aims of this study were to investigate the effect of breed and parity on colostrum components, and to associate sow breed, parity, and colostrum components with survival, growth, and the occurrence of diarrhoea of their litters. In Experiment 1, 64 sows (Duroc = 13; Landrace = 17 and Large White = 34) were included. In Experiment 2, 71 sows with different parities (1 = 10; 2 = 16; 3 = 13; 4 = 12; ≥5 = 20) were included. The number (N) of live piglets, litter body weight (Experiment 1), and the occurrence of diarrhoea (Experiment 1) were recorded at farrowing, at 2−3 days of age, and at weaning. Colostrum was analysed for proximate composition, immunoglobulins (Igs), and somatic cell count (SCC). Stepwise regressions and ANOVA models were used to associate breed, parity, and colostrum components with litter performance. The Duroc breed had the highest IgG and IgA (p < 0.005). Gilts had a higher fat% and SCC (p< 0.0001); these compounds were positively correlated (r = 0.45). Increased IgA tended to increase the N of weaned piglets (p = 0.058) and reduce litter diarrhoea (p = 0.021). The SCC increased the N of weaned piglets (p = 0.031). Overall, this study confirmed that breed and parity can influence the colostrum composition and highlighted the key role of Igs and somatic cells in piglet health.

The Role of Dietary and Microbial Fatty Acids in the Control of Inflammation in Neonatal Piglets

Simple Summary

The maturation of the gut is a specific and very dynamic process in new-born piglets. Consequently, piglet’s gut is very susceptible to disturbances, especially in stressful periods of life, such as weaning, when the gut lining often becomes inflamed and leaky. Dietary fatty acids (FA) do not only serve as source of energy and essential FA, but they are important precursors for bioactive lipid mediators, which modulate inflammatory signalling in the body. The current review summarizes results on dietary sources of FA for piglets, the signalling cascades, bioactivities, the necessity to consider the autoxidation potential of polyunsaturated FA and the area of microbially produced long-chain FA. That said, porcine milk is high in fat, whereby the milk FA composition partly depends on the dietary FA composition of the sow. Therefore, manipulation of the sow diet is an efficient tool to increase the piglet’s intake of specific FA, e.g., n-3 polyunsaturated FA which show anti-inflammatory activity and may support intestinal integrity and functioning in the growing animal.

Abstract

Excessive inflammation and a reduced gut mucosal barrier are major causes for gut dysfunction in piglets. The fatty acid (FA) composition of the membrane lipids is crucial for mediating inflammatory signalling and is largely determined by their dietary intake. Porcine colostrum and milk are the major sources of fat in neonatal piglets. Both are rich in fat, demonstrating the dependence of the young metabolism from fat and providing the young organism with the optimum profile of lipids for growth and development. The manipulation of sow’s dietary polyunsaturated FA (PUFA) intake has been shown to be an efficient strategy to increase the transfer of specific FAs to the piglet for incorporation in enteric tissues and cell membranes. n-3 PUFAs, especially seems to be beneficial for the immune response and gut epithelial barrier function, supporting the piglet’s enteric defences in situations of increased stress such as weaning. Little is known about microbial lipid mediators and their role in gut barrier function and inhibition of inflammation in neonatal piglets. The present review summarizes the current knowledge of lipid nutrition in new-born piglets, comparing the FA ingestion from milk and plant-based lipid sources and touching the areas of host lipid signalling, inflammatory signalling and microbially derived FAs.

Serum metabolome and gut microbiome alterations in broiler chickens supplemented with lauric acid

Antibiotic overuse in poultry husbandry poses a potential threat to meat safety and human health. Lauric acid (LA) is a primary medium-chain fatty acid (MCFA) with a strong antibacterial capacity. The goal of this study was to evaluate the beneficial effects of LA on the growth performance, immune responses, serum metabolism, and cecal microbiota of broiler chickens. One-day-old male Ross 308 broilers were randomly divided into 4 groups: CON, fed a basal diet; ANT, a basal diet supplemented with 75 mg/kg antibiotic; LA500, a basal diet supplemented with 500 mg/kg LA; LA1000, a basal diet supplemented with 1000 mg/kg LA. The feeding period was 42 d. The results showed that LA significantly improved broiler growth and immune functions, as evidenced by increased body weight (BW) and average daily gain (ADG), enhanced intestinal mucosal barrier, upregulated immunoglobulins (IgA, IgM, and IgY), and downregulated inflammatory cytokines (IL-1β, IL-6, TNF-α, IL-4, and IL-10) (P < 0.05). HPLC/MS-based metabolome analysis revealed that the serum metabolites in the LA group differed from those of CON and ANT groups. LA markedly decreased the abundance of phosphatidylcholines (PCs), increased lysophosphatidylcholines (LysoPCs), and inhibited the sphingolipid metabolism pathway, indicating its capacity to modulate lipid metabolism. 16S rRNA sequencing indicated that LA significantly altered cecal microbiota composition by reducing Phascolarctobacterium, Christensenellaceae_R-7_group, and Bacteroides, and increasing Faecalibacterium and Ruminococcaceae_UCG-014 (P < 0.05). Furthermore, Spearman correlation analysis revealed that changes in metabolism and microbiota were highly correlated with the growth and immune indices; strong links were also found between lipid metabolism and microbial composition. Taken together, LA promotes broiler growth and immune functions by regulating lipid metabolism and gut microbiota. The above findings highlight the substantial potential of LA as a supplement in poultry diets and provide a new strategy to reduce antibiotic usage and improve food safety.

Metabolic Transition of Milk Triacylglycerol Synthesis in Response to Varying Levels of Three 18-Carbon Fatty Acids in Porcine Mammary Epithelial Cells

This study aimed to examine the effects of increasing levels of three 18-carbon fatty acids (stearate, oleate and linoleate) on mammary lipogenesis, and to evaluate their effects on the milk lipogenic pathway in porcine mammary epithelial cells (pMECs). We found that increasing the three of 18-carbon fatty acids enhanced the cellular lipid synthesis in a dose-dependent manner, as reflected by the increased (triacylglycerol) TAG content and cytosolic lipid droplets in pMECs. The increased lipid synthesis by the three 18-carbon fatty acids was probably caused by the up-regulated expression of major genes associated with milk fat biosynthesis, including CD36 (long chain fatty acid uptake); GPAM, AGPAT6, DGAT1 (TAG synthesis); PLIN2 (lipid droplet formation); and PPARγ (regulation of transcription). Western blot analysis of CD36, DGAT1 and PPARγ proteins confirmed this increase with the increasing incubation of 18-carbon fatty acids. Interestingly, the mRNA expressions of ACSL3 and FABP3 (fatty acids intracellular activation and transport) were differentially affected by the three 18-carbon fatty acids. The cellular mRNA expressions of ACSL3 and FABP3 were increased by stearate, but were decreased by oleate or linoleate. However, the genes involved in fatty acid de novo synthesis (ACACA and FASN) and the regulation of transcription (SREBP1) were decreased by incubation with increasing concentrations of 18-carbon fatty acids. In conclusion, our findings provided evidence that 18-carbon fatty acids (stearate, oleate and linoleate) significantly increased cytosolic TAG accumulation in a dose-dependent manner, probably by promoting lipogenic genes and proteins that regulate the channeling of fatty acids towards milk TAG synthesis in pMECs.

Effects of Dietary Fat Sources during Late Gestation on Colostrum Quality and Mammary Gland Inflammation in Lipopolysaccharide-Challenged Sows

Simple Summary

In the present study, late gestating sows were challenged with lipopolysaccharide (LPS) endotoxin, which can impair the immune system of mammary gland cells and result in an inflammatory response. Additionally, the LPS-treated sows were fed 3% soybean oil (SO), 3% coconut oil (CO) or 3% fish oil (FO) diets and were used to study the effect of fat sources on the colostrum quality and mammary gland inflammation of sows exposed to immune challenge. The results show that FO inclusion exerted anti-inflammatory effects in mammary glands and counteracted the LPS-induced damaged colostrum synthesis and pro-inflammatory response when compared to CO diets. These findings suggest that fatty acid profiles of different oil types in late gestation differentially affect metabolic health in sows, but a longer period of FO supplementation to sows is needed to determine a positive effect on piglets.

Abstract

This study aimed to investigate the effects of maternal lipopolysaccharide (LPS) challenge and dietary fat sources on colostrum quality and inflammatory response in sows. Sixty Landrace × Yorkshire sows were randomly assigned to three dietary treatments supplemented with 3% soybean oil (SO), 3% coconut oil (CO) or 3% fish oil (FO), respectively, from Day 90 of gestation until parturition. On Day 112 of gestation, half the sows from each dietary treatment were challenged with LPS (10 μg/kg BW) or saline. The results showed that maternal LPS challenge decreased colostrum yield and dry matter content. A similar pattern of changes was observed for body weight gain and colostrum intake in piglets from LPS-challenged sows. Maternal LPS challenge increased the levels of tumor necrosis factor α (TNFα), interleukin 1β (IL1β) and IL6 in colostum, and the mRNA abundance of IL6, IL1β and TNFα and the phosphorylation level of p65 in mammary glands. However, the responses of these variables to LPS treatment were lower in sows fed a FO diet. In conclusion, maternal immune challenge reduced the growth performance of piglets by decreasing colostrum yield and intake by piglets, and dietary supplementation with FO in sows attenuates the LPS-induced inflammatory response in mammary glands.

Review: nutritional and endocrine control of colostrogenesis in swine

Colostrum plays an essential role in ensuring the survival, growth and health of piglets by providing energy, nutrients, immunoglobulins, growth factors and many other bioactive components and cells. Both colostrum yield and composition are highly variable among sows, yet mechanisms and factors that regulate colostrogenesis are not fully known. Unlike sow milk yield, sow colostrum yield is not highly determined by litter size and suckling intensity but is largely driven by sow-related factors. Colostrum synthesis is under hormonal control, with prolactin and progesterone concentrations prepartum having, respectively, positive and negative influences on colostrum yield. Less is known about the endocrine control of the end of colostrogenesis in swine, which is characterized by the closure of tight junctions in the mammary epithelium and the cessation of transfer of immunoglobulin G (IgG) into lacteal secretions. Recent studies indicate that exogenous hormones may influence colostrogenesis. Inducing parturition by injecting prostaglandin F2α on day 114 of gestation in combination with an oxytocin-like molecule reduced colostrum yield, and injection of prostaglandin F2α alone either reduced colostrum yield or had no effect. Injecting a supraphysiological dose of oxytocin to sows in the early postpartum period delayed the tightening of mammary tight junctions, thereby prolonging the colostral phase and increasing concentrations of IGF-I and IgG and IgA in early milk. The development of strategies to improve colostrum composition in swine through maternal feeding has been largely explored but very few attempts were made to increase colostrum yield. This is most likely because of the difficulty in measuring colostrum yield in swine. The fatty acid content of colostrum greatly depends on the amount of lipids provided in the sow diet during late gestation, whereas the fatty acid profile is largely influenced by the type of lipid being fed to the pregnant sow. Moreover, various ingredients that presumably have immuno-modulating effects (such as fish oil, prebiotics and probiotics) increased concentrations of IgG, IgA and/or IgM in sow colostrum when they were provided during the last weeks of gestation. Finally, there is some evidence that sow nutrition during late gestation may influence colostrum yield but this clearly warrants more research. This review emphasizes that although progress has been made in understanding the control of colostrogenesis in swine, and that strategies exist to manipulate fat and immunoglobulin contents of colostrum, ways to increase colostrum yield are still lacking.

Evaluation of Breed and Parity Order Effects on the Lipid Composition of Porcine Colostrum

Porcine colostrum lipid classes and fatty acids (FA) were characterized in 6 pools (from 69 samples) from 3 sow breeds (Italian Large White, Italian Landrace, and Italian Duroc) and different parity orders (only Large White). Triacylglycerols (TAG; 94.44 expressed as g/100 g of fat) were the most abundant lipid class, followed by diacylglycerols (DAG; 3.36 g/100 g of fat), free fatty acids (FFA; 0.98 g/100 g of fat), and cholesterol (0.84 g/100 g of fat). The main FAs found in swine colostrum were palmitic (27.29%, expressed as g/100 g of total FA), oleic (28.81%), and linoleic (23.39%) acids. Both the breed of sow and parity order affected the FA and lipid composition. The results suggest that the FA composition of swine colostrum is similar to that of human colostrum and could represent a new source of nutrients for human infants, after further assessment of hygienic and quality aspects. The swine model could be an opportunity for a better understanding of colostrum effects on newborns.

Recent progress of porcine milk components and mammary gland function

As the only nutritional source for newborn piglets, porcine colostrum and milk contain critical nutritional and immunological components including carbohydrates, lipids, and proteins (immunoglobulins). However, porcine milk composition is more complex than these three components. Recently, scientists identified additional and novel components of sow colostrum and milk, including exosomes, oligosaccharides, and bacteria, which possibly act as biological signals and modulate the intestinal environment and immune status in piglets and later in life. Evaluation of these nutritional and non-nutritional components in porcine milk will help better understand the nutritional and biological function of porcine colostrum and milk. Furthermore, some important functions of the porcine mammary gland have been reported in recent published literature. These preliminary studies hypothesized how glucose, amino acids, and fatty acids are transported from maternal blood to the porcine mammary gland for milk synthesis. Therefore, we summarized recent reports on sow milk composition and porcine mammary gland function in this review, with particular emphasis on macronutrient transfer and synthesis mechanisms, which might offer a possible approach for regulation of milk synthesis in the future.

Metabolic transition of milk triacylglycerol synthesis in response to varying levels of palmitate in porcine mammary epithelial cells

BACKGROUND

Milk in mammals is a key source of lipids for offspring, providing both critical energy and essential fatty acids. For lactating sows, palmitic acid is one of the most abundant fatty acids in milk, providing 10~12% of the suckling pig total dietary energy supply. However, the effects of exogenous palmitic acid on milk fat synthesis in sow mammary glands are not well-known. In this study, we investigated the effects of palmitic acid on lipogenic genes in porcine mammary epithelial cells (pMECs) to explore the role of exogenous palmitic acid in mediating milk triacylglycerols (TAG) synthesis.

METHODS

Porcine mammary epithelial cells were cultured for 24 h in the presence of different concentrations of palmitate (0, 25, 50, 100, 200, 400, and 600 μM). The effect of palmitate on cell viability was tested via MTT assay. Intracellular lipid accumulation was measured through Oil Red O staining, and TAG levels were quantified by enzymatic colorimetric methods. Expression of genes and proteins involved in milk fat biosynthesis were assayed with quantitative real-time polymerase chain reaction (qPCR) and Western blotting, respectively.

RESULTS

Incubation with palmitate promoted cellular lipid synthesis in a dose-dependent manner, as reflected by the increased TAG content and enhanced formation of cytosolic lipid droplets. The increased lipid synthesis by palmitate was probably attributable to the upregulated mRNA expression of genes associated with milk fat biosynthesis, including long-chain fatty acid uptake (LPL, CD36), intracellular activation and transport (ACSL3, FABP3), TAG synthesis (GPAM, AGPAT6, DGAT1), lipid droplet formation (PLIN2), and regulation of transcription (PPARγ). Western blot analysis of CD36 and DGAT1 proteins confirmed the increased lipid synthesis with increasing incubation of palmitate. However, the genes involved in fatty acid de novo synthesis (ACACA, FASN), fatty acid desaturation (SCD), and regulation of transcription (SREBP1, INSIG1) were inversely affected by incubation with increasing concentrations of palmitate. Western blot analysis of ACACA protein confirmed this decrease associated with increasing levels of palmitate.

CONCLUSIONS

Results from this study suggest that palmitate stimulated the cytosolic TAG accumulation in pMECs, probably by promoting lipogenic genes and proteins that are involved in lipid synthesis. However, addition of palmitate decreased the fatty acid de novo synthesis in pMECs.