| This study used two test animals to observe different diets model affect on milk composition, the concentration of fatty acids in the milk and arterial or venous blood and milk fatty acid metabolism of mammary gland in lactating dairy goats and cows. The main findings are as follows:1. The objective of this study was to determine the effects of two diets with different roughage profiles on milk composition and on the expression of key genes associated with fatty acid synthesis in the mammary gland of lactating dairy goats. Eight multiparous lactating goats (BW=45.6±2.5kg, DIM=90±12d) fitted with external pudic artery (EPA) and subcutaneous abdominal vein (SAV) catheters were assigned to two treatments in a crossover design. The goats were fed with different roughage profiles diets with similar concentrate-roughage ratio. The diets were:1) a high quality roughage treatment (MF) containing28.5%Chinese wildrye hay,19%corn silage,9.5%alfalfa and43%concentrate;2) a low quality roughage treatment (CS) containing28%Chinese wildrye hay,28%corn stover and44%concentrate, on dry matter (DM) basis. Each period lasted for21d. The first14d served as an adaptation period, and the last7d served as a sample collection period. Dry matter intake (DMI), milk yield and milk composition were measured. Milk and blood samples from EPA and SAV were collected for fatty acid (FA) analysis. Mammary gland biopsies were performed after milking on the last day of each period and the tissues were analyzed for the mRNA expression of acetyl-coenzyme A carboxylase-a (ACACA), fatty acid synthase (FASN), stearoyl CoA desaturase (SCD), and lipoprotein lipase (LPL). The DMI and milk yield were not affected by the treatments. Milk fat (3.16%vs.2.96%) and protein (2.99%vs.2.89%) content were higher in MF goats than in CS goats. Milk fat yield tended to be higher in MF goats compared with CS goats (16.7vs.15.1g/d). Milk fatty acid composition was not different between treatments except for C18:3n3(0.27vs.0.15g/100g). Compared with CS goats, MF goats had higher in rectificative subcutaneous abdominal venous (RSAV) plasma concentration of total FA(0.55vs.0.38 mg/mL), mammary balance of total FA was also increased in MF goats (11.17vs.5.51g/d). No differences were found in mammary blood flow, EPA plasma concentration, mammary uptake and extraction of fatty acids between the two treatments. Compared with CS, the expression of FASN and ACACA tended to be increased by20%and18%, and LPL and SCD were increased by39%and50%in MF, respectively. The results demonstrated that diets with MF can increase milk fat content, milk fat yield, and the expression of LPL and SCD in mammary gland of dairy goats.2. The objectives of this study were to determine the effects of roughage quality on fatty acid metabolism in mammary gland and their transfer into milk fat in lactating dairy cows. Nine multiparous Holstein cows (BW=617±21; DIM=120±20) were used in a replicated3×3Latin square design with21d of diet adaptation and7d of data collection. Blood was collected from external pudendal artery and subskin abdominal vein. Treatments (DM basis) were:1)40%corn straw plus60%commercial concentrate supplement A (CSA; CP:16.55%, NDF:37.06%, NEL:1.50Mcal/Kg);2)40%corn straw plus60%commercial concentrate B (CSB; CP:15.57%, NDF:41.84%, NEL1.46Meal/Kg);3)3.7%hay,26.7%corn silage,28.4%alfalfa plus41.2%concentrate (Mixed Forage as MF; CP:15.50%, NDF:41.39%, NEL:1.44Mcal/Kg). Fatty ACIDs were analyzed by Gas Chromatography and data were analyzed by the PROC MIXED procedure of SAS9.0. Results showed that DMI were lower for animals in MF group (13.69Kg/d) when compared to those in CSA and CSB groups (15.66&15.24Kg/d, P=0.004). No differences in milk yield and composition were observed among treatments, the MF group significantly increased the dairy efficiency (1.43) compared to the CSA (1.26) and CSB (1.26,P=0.05) groups. The concentrations of most LCFAs (C16to C18) and total FA in plasma of both artery and vein from animals in the MF group were higher than CSA and CSB groups. Particularly, plasma concentration of linolenic acid (C18:3n3) was significantly higher (P<0.0001) in the MF group compared to CSA and CSB groups, and the plasma FA profiles were reflected in milk. Animals in the MF group had the highest milk concentration of linolenic acid (0.38g/100g vs.0.26&0.20g/100g, P=0.04). The MF group tended to increase the mammary extraction rate of total LCFAs than CSA and CSB (P=0.17), however no significant difference was found on the uptake ratio of mammary gland between treatments. We refered that the different roughages sources could not change the FAs extraction rate in mammary gland, high quality roughages tended to adjust the composing of milk fat to be better for human health. |
PDF Full Text Request