Effects Of Oil Infusion Into Jugular Vein On Amino Acids Uptake By Mammary Glands In Lactating Dairy Cows

In this experiment, jugular vein catheterization technique was applied to investigate the effects of jugular vein infusion of different combinations of oils providing long chain unsaturated fatty acids into lactating dairy cows on the arterial blood concentrations of amino acids and their uptake pattern in mammary glands, to clarify the influence of infusing milk fat precursors on the synthesis of milk protein, and provide theoretical basis for further study of the interaction between the synthesis of milk fat and milk protein in dairy cows. This paper is divided into three experiments.The effect of different combinations of oils on the contents and proportions of amino acids in tail arterial blood was studied in experiment 1. Eight Holstein cows with good body conditions, early lactation, similar body weight and milk yield (about 25 kg/d) were randomly assigned in 4 groups with 2 cows each, and 4×4 Latin square experimental design was used. The prefeeding period lasted for 14 days, and the test period was 12 days, each experimental period contained 5d infusion period and 7d recovery period. Infusion treatments were designed as follows:Group OS for olive oil and safflower oil,60.89g/ (d-cow)C18:1+60.16g/(d-cow)C18:2; OF for olive oil and flaxseed oil,61.49g/(d·cow) C18:1+42.13g/(d-cow) C18:3; SF for safflower oil and flaxseed oil,61.17g/(d-cow) C18:2+41.72g/(d-cow) C18:3; and OSF for olive oil, safflower oil and flaxseed oil, 58.30g/(d-cow)C18:1+58.17g/(d-cow) C18:2+39.96g/(d-cow) C 18:3. milk samples, caudal artery blood’and mammary vein blood were collected at the last day of each infusion period, milk samples were used to determine milk composition and amino acid content in milk; blood samples were collected for determination of amino acids in the blood, and to estimate blood flow to calculate the amino acid uptake efficiency in the mammary gland. In experiment 1, amino acids in the caudal artery blood were determined. The results showed that:after lactating dairy cows intravenous infusion of four different groups of oil, the contents of a single amino acid Cys, Val between four treatment groups were significantly different (P< 0.05), changes in the contents of single amino acids Arg arid branched chain amino acid among four treatment groups tended to be significant (P= 0.12, P= 0.08), the differences in the content of other amino acids were not significant (P > 0.05). Proportions of Ser in four treatment groups were significantly different (P< 0.05), the proportions of ala, Val and Pro in four treatment groups showed a trend for significant difference (P= 0.14; P= 0.07; P=0.07), the differences in the others were not significant (P> 0.05). These results suggested that:intravenous infusion of grease in lactating dairy cows influences caudal artery composition of amino acids to some extent, but there were no significant differences between the four treatment groups to most of the amino acids, group OF containing olive oil and sesame oil showed a more obvious effect on arterial concentration of amino acid when compared with the other three treatments.Experiment 2, by the arterial contents of amino acids tested, the application of Fick’s law to estimate blood flow and the related formula to calculate amino acid dynamic venous, mammary amino acid uptake efficiency, mammary uptake of amino acids and amino acids in mammary transformation efficiency, this experiment further investigated the effect of jugular vein infusion of grease containing different long chain unsaturated fatty acids on the lactating bovine mammary amino acid uptake efficiency. The test results showed that in the dynamic venous, mammary of amino acid uptake and uptake of amino acids and amino acids in mammary transformation efficiency, single amino acids, total amino acid, essential amino acids, non essential amino acids, branched chain amino acids, and limiting amino acids among four treatment groups showed no significant difference (P> 0.05); in group OF, amino acids of venous、amino acids in mammary uptake efficiency and mammary gland uptake of amino acids were higher than the other treatments, while mammary uptake of amino acid conversion efficiency did not follow this pattern. These results suggested that, providing long chain unsaturated fatty acids to lactating dairy cows by jugular vein infusion of oil have certain effect on the four indicators, but overall treatment group OF on mammary amino acid synthesis has a certain role in promoting.In experiment three, the effects of jugular vein infusion of different oil combinations of lactation dairy cows on milk yield, milk protein content and milk protein yield were studied based on above experiments. The experiment results showed that the milk yield and milk protein content was significantly different between four groups (P< 0.05), milk protein yield in each treatment groups showed no significant difference (P> 0.05). It can be seen that milk yield and milk protein yield were decreased, but milk protein content was increased in each treatment group.