Negative effects of long-term feeding of high-grain diets to lactating goats on milk fat production and composition by regulating gene expression and DNA methylation in the mammary gland

Background： It is well known that feeding a high concentrate（HC） diet to lactating ruminants likely induces subacute ruminal acidosis（SARA） and leads to a decrease in milk fat production. However, the effects of feeding a HC diet for long periods on milk fatty acids composition and the mechanism behind the decline of milk fat still remains poorly understood. The aim of this study was to investigate the impact of feeding a HC diet to lactating dairy goats on milk fat yield and fatty acids composition with an emphasis on the mechanisms underlying the milk fat depression. Seventeen mid-lactating dairy goats were randomly allocated to three groups. The control treatment was fed a low-concentrate diet（35% concentrate, n = 5, LC） and there were two high-concentrate treatments（65% concentrate, HC）, one fed a high concentrate diet for a long period（19 wks, n = 7, HL）; one fed a high concentrate diet for a short period of time（4 wk, n = 5, HS）. Milk fat production and fatty acids profiles were measured. In order to investigate the mechanisms underlying the changes in milk fat production and composition,the gene expression involved in lipid metabolism and DNA methylation in the mammary gland were also analyzed.Results： Milk production was increased by feeding the HC diet in the HS and HL groups compared with the LC diet（P 〈 0.01）, while the percentage of milk fat was lower in the HL（P 〈 0.05） but not in the HS group. The total amount of saturated fatty acids（SFA） in the milk was not changed by feeding the HC diet, whereas the levels of unsaturated fatty acids（UFA） and monounsaturated fatty acids（MUFA） were markedly decreased in the HL group compared with the LC group（P 〈 0.05）. Among these fatty acids, the concentrations of C15：0（P 〈 0.01）, C17：0（P 〈 0.01）, C17：1（P 〈 0.01）, C18：1 n-9 c（P 〈 0.05）, C18：3 n-3 r（P 〈 0.01） and C20：0（P 〈 0.01） were markedly lower in the HL group, and the concentrations of C20：0（P 〈 0.05） and C18：3 n-3 r（P 〈 0.01） were lower in the HS group compared with the LC group. However, the concentrations of C18：2 n-6 c（P 〈 0.05） and C20：4 n-6（P 〈 0.05） in the milk fat were higher in the HS group. Real-time PCR results showed that the m RNA expression of the genes involved in milk fat production in the mammary gland was generally decreased in the HL and HS groups compared with the LC group. Among these genes, ACSL1, ACSS1 ＆ 2, ACACA, FAS, SCD, FADS2, and SREBP1 were downregulated in the mammary gland of the HL group（P 〈 0.05）, and the expressions of ACSS2, ACACA, and FADS2 m RNA were markedly decreased in the HS goats compared with the LC group（P 〈 0.05）. In contrast to the gene expression, the level of DNA methylation in the promoter regions of the ACACA and SCD genes was increased in the HL group compared with the LC group（P 〈 0.05）. The levels of ACSL1 protein expression and FAS enzyme activity were also decreased in the mammary gland of the HL compared with the LC group（P 〈 0.05）.Conclusions： Long-term feeding of a HC diet to lactating goats induced milk fat depression and FAs profile shift with lower MUFAs but higher SFAs. A general down-regulation of the gene expression involved in the milk fat production and a higher DNA methylation in the mammary gland may contribute to the decrease in milk fat production in goats fed a HC diet for long time periods.

Concentration Changes of Medroxyprogesterone Acetate in Serum and Milk in Lactating Woman Who Used Depo Geston~

Objective To determine the concentration changes of medroxyprogesterone acetate （MPA） in serum and milk in the Chinese lactating women who used Depo Geston Methods Ten postpartum and breastfeeding women received an injectable contraceptive of Depo Geston （depo medroxyprogesterone acetate, DMPA, 150 mg/ampoule）. Serum and milk samples were collected in the 1^st, 2^st, 4^th, 6^th, 8^th 10^th and 12^th week after contraceptive injection. The concentrations of medroxyprogesterone acetate （MPA） in serum and milk were determined by radioimmunoassay. Results The highest MPA concentration in serum was observed at the 1^st week and then the level of serum MPA decreased obviously at the 2^na and 4^th week. After the 4^th week, the decline of serum MPA level slowed down. The concentration of milk MPA reached the highest level at 1^th week. But at the 2^nd week the average level of MPA in milk dropped by half The MPA concentration in the milk was changed in the range of 5.2-8.3 ng/mL in the following 10 weeks. During observation, the average ratios of concentration and area under curve （AUC） in milk/serum were both 0.55. There was a wide variation in MPA concentrations and ratios of milk/serum between subjects. Conclusion MPA concentrations maintained a certaim level at the 12^th week after DMPA injection. However, whether mather＇s intake of DMPA during feeding period has effect on children＇s growth, espcially pubertal growth, deserves further studies.

Lactation mastitis: Promising alternative indicators for early diagnosis

Although lactation mastitis(LM)has been extensively researched,the incidence rate of LM remains a salient clinical problem.To reduce this incidence rate and achieve a better prognosis,early and specific quantitative indicators are particularly important.It has been found that milk electrolyte concentrations(chloride,potassium,and sodium)and electrical conductivity(EC)significantly change in the early stages of LM in an animal model.Several studies have evaluated EC for the detection of subclinical mastitis in cows.EC,chloride,and sodium content of milk were more accurate for predicting infection status than were other variables.In the early stages of LM,lactic sodium,chloride,and EC increase,but potassium decreases.However,these indicators have not been reported in the diagnosis of LM in humans.This review summarizes the pathogenesis and the mechanism of LM in terms of milk electrolyte concentration and EC,and aim to provide new ideas for the detection of sub-clinical mastitis in humans.

Milk protein concentrate and reduced-calcium milk protein concentrate as natural emulsifiers in clean label high-protein ice cream manufacture

Clean label food is a rising consumer trend in the food industry.Milk protein concentrate(MPC)and reduced-calcium milk protein concentrate(RCMPC)could serve as natural emulsifiers and increase the total protein content of ice cream products.The objectives of this study were to determine and compare the effects of MPC and RCMPC on ice cream composition,mix viscosity,storage stability,meltdown rate,and texture.A base formulation with 3%non-fat dry milk(NFDM)and no added emulsifiers was set as the control.Three levels of MPC or RCMPC(each powder containing 85%protein)at 1%,2%,and 3%were incorporated by replacing equivalent amounts of NFDM and keeping other ingredients unchanged.All ice cream treatments were processed with a target overrun of 70%and hardened at−25℃in a blast freezer.Additions of MPC or RCMPC at 1%,2%,and 3%corresponded to increases in protein content of ice cream by 15%,30%,and 45%,respectively.The viscosity of the ice-cream mix increased with increasing levels of MPC or RCMPC.In general,higher protein samples had slower meltdown rate and higher values of hardness and adhesiveness,but the trends were inconsistent.No shrinkage in volume was observed in any ice cream stored at−25℃after 180 days.However,an additional storage stability study revealed that the control showed significant shrinkage after 60 days(−6.5%±1.5%),90 days(−7.1%±1.8%),and 180 days(−7.9%±1.1%)in a typical household-style freezer at−13℃.MPC at 1%also showed significant shrinkage after 180 days,while samples with RCMPC at any levels showed no shrinkage at all.Ice cream manufacturers may consider MPC and RCMPC natural alternatives to synthetic emulsifiers,with RCMPC being more effective than MPC in terms of ice cream storage stability.