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 highfat 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.

Sodium acetate promotes fat synthesis by suppressing TATA element modulatory factor 1 in bovine mammary epithelial cells

Short-chain fatty acids are important nutrients that regulate milk fat synthesis.They regulate milk syn-thesis via the sterol regulatory element binding protein 1(SREBP1)pathway;however,the details are still unknown.Here,the regulation and mechanism of sodium acetate(SA)in milk fat synthesis in bovine mammary epithelial cells(BMECs)were assessed.BMECs were treated with SA supplementation(SAþ)or without SA supplementation(SA-),and milk fat synthesis and activation of the SREBP1 pathway were increased(P=0.0045;P=0.0042)by SAþand decreased(P=0.0068;P=0.0031)by SA-,respectively.Overexpression or inhibition of SREBP1 demonstrated that SA promoted milk fat synthesis(P=0.0045)via the SREBP1 pathway.Overexpression or inhibition of TATA element modulatory factor 1(TMF1)demon-strated that TMF1 suppressed activation of the SREBP1 pathway(P=0.0001)and milk fat synthesis(P=0.0022)activated by SAþ.Overexpression or inhibition of TMF1 and SREBP1 showed that TMF1 suppressed milk fat synthesis(P=0.0073)through the SREBP1 pathway.Coimmunoprecipitation analysis revealed that TMF1 interacted with SREBP1 in the cytoplasm and suppressed the nuclear localization of SREBP1(P=0.0066).The absence or presence of SA demonstrated that SA inhibited the expression of TMF1(P=0.0002)and the interaction between TMF1 and SREBP1(P=0.0001).Collectively,our research sug-gested that TMF1 was a new negative regulator of milk fat synthesis.In BMECs,SA promoted the SREBP1 pathway and milk fat synthesis by suppressing TMF1.This study enhances the current understanding of the regulation of milk fat synthesis and provides new scientific data for the regulation of milk fat synthesis.

Essential amino acid ratios and mTOR affect lipogenic gene networks and miRNA expression in bovine mammary epithelial cells

Background： The objective of this study was to study how changing the ratio of Lys to Thr, Lys to His, and Lys to Val affects the expression of lipogenic genes and microRNA （miRNA） in bovine mammary epithelial cells. Results： Triplicate cultures with the respective ＂optimal＂ amino acid （AA） ratio （OPAA = Lys：Met 2.9：1; Thr：Phe 1.05：1; Lys：Thr 1.8：1; Lys：His 2.38：1; Lys：Val 1.23：1） plus rapamycin （OPAARMC; positive control）, OPAA, Lys：Thr 2.1：1 （LT2.1）, Lys：Thr 1.3：1 （LT1.3）, Lys：His 3.05：1 （LH3.0）, or Lys：Val 1.62：1 （LV1.6） were incubated in lactogenic medium for 12 h. The expression of 15 lipogenic genes and 7 miRNA were evaluated. Responses to LT2.1, LT1.3, LH3.0, and LV1.6 relative to the control （OPAARMC） included up-regulated expression ofACSS2, FABP3, ACACA, FASN, SCD, LPIN1, INSIG1, SREBF1, PPARD, and NR1H3 （commonly known as LXR-a）. Furthermore, LV1.6 up-regulated expression of ACSL1, DGAT1, and RXRA and down-regulated PPARG expression. Although no effect of OPAA on expression of PPARG was observed, compared with the control, OPAA up-regulated expression of the PPAR targets ACSS2, FABP3, ACACA, FASN, SCD, LPIN1, INSIG1, and SREBF1. Compared with the control, the expression of the anti-lipogenic MIR27AB was down-regulated by OPAA, LT2.1, LT1.3 and LH3.0. In contrast, compared with the control, the expression of the pro-lipogenic MIR21 was up-regulated by LT2.1, LT1.3, LH3.0, and LV1.6. Conclusions： The observed up-regulation of lipogenic gene networks and the changes in expression of key miRNA involved in the control of lipogenic balance are indicative of a potentially important role of EAA ratios and mTOR signaling in the regulation of milk fat synthesis.

Biological Function Research Progress of FABP5

The intracellular Fatty Acid Binding Proteins （FABPs） are a well-conserved family which functions as lipid chaperones. Recent findings also reveal that they are crucial mediators of lipid metabolism, cell growth and differentiation, cellular signaling and gene transcription. Ongoing studies are identifying the mechanistic complexity and vast biological diversity of different isoforms of FABPs. This paper introduced the biological function of FABP5 in inflammatory, metabolic diseases and milk fat synthesis.

Influences of lauric acid addition on performance,nutrient digestibility and proteins related to mammary gland development in dairy cows

Lauric acid(LA)has the possibility to improve milk production in dairy cows by improving mammary gland development,however,the mechanism by which it might regulate mammary gland development is unclear.The influence of LA on milk production,nutrient digestibility and the expression of proteins related to mammary gland development in dairy cows were evaluated.Forty primiparous Holstein dairy cows were divided into 4 groups in a randomized block design.Four treatments included the control(0 g/d LA per cow),low-LA(100 g/d LA per cow),medium-LA(200 g/d LA per cow),and high-LA(300 g/d LA per cow).Yields of milk,fat-corrected milk,and energy-corrected milk quadratically increased(P<0.05),and yield and content of milk fat linearly increased(P<0.05)with LA supplementation.Percentages of C12:0,C18:1 and C20:1 fatty acids in milk fat linearly increased(P<0.05),but that of C16:0 fatty acid linearly decreased(P=0.046).Supplementation of LA led to a linear and quadratical increase(P<0.05)in digestibility of dry matter,organic matter,neutral detergent fibre and acid detergent fibre,and ruminal total volatile fatty acid concentration but a linear reduction(P=0.018)in the ratio of acetate to propionate.The enzymatic activities of ruminal pectinase,xylanase,andα-amylase,and populations of total bacteria and anaerobic fungi increased linearly(P<0.05),while populations of total protozoa and methanogens decreased linearly(P<0.05)with increased LA addition.Following LA addition,blood glucose,triglyceride,estradiol,prolactin,and insulin-like growth factor 1 concentrations increased linearly(P<0.05)and albumin and total protein concentrations increased quadratically(P<0.05).Moreover,addition of 200 g/d LA promoted(P<0.05)the expression of protein involved in mammary gland development and fatty acids synthesis.These results suggested that LA addition enhanced milk production and fatty acids synthesis by stimulating nutrient digestion,the expression of proteins associated with milk fat synthesis and mammary gland development.

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,energycorrected 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 a-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.