Effects of arginine infusion through jugular vein on the milk performance and casein synthesis in mid-lactation cows

Abstract Text:

Previous studies show that, milk protein yield increase with arginine infusion (Doepel and Lapierre 2011); Our previous in vitro work by Chen et al. (2013) demonstrates that arginine increases casein protein synthesis in bovine mammary epithelial cells, and arginine plays an important role in the transcriptional regulation of casein genes and mTOR-related genes in bovine mammary epithelial cells (Wang et al. 2014). Subsequently, our Wistar rats feeding trail found that 2× Arg group had significant effects on the mammary gland development and its casein protein synthesis (Hu et al. 2015). But whether arginine promotes the growth of the cow mammary tissue and casein expression is unknown. Therefore, this study was carried out to investigate the responses of milk yield and milk composition for arginine infusion by mid-lactating Holstein cows.

Six healthy lactating cows at similar lactation stages with similar weights, parities, milk yields, and body conditions were divided into 3 groups (2 for each group), casein model group (control group), arginine infusion group (37.66 g arginine contenting 12.10 g N per day) and alanine iso-nitrogen group (77.24 g alanine contenting N 12.13 g N per day) respectively in the 3 × 3 Latin square trail with 7-day infusion plus 15-day interval per period. The milk performance, casein content, and casein gene expression were detected. The results showed that, at day 5, arginine infusion group was higher than casein model group in the contents of milk protein and non-fat milk solids (P<0.05); while at day 6, arginine infusion group was higher in milk fat content compared to alanine iso-nitrogen group (P<0.05). As for the milk casein contents, α-Casein in casein model group was lower than these in the other 2 groups (P<0.05); β-Casein had no difference between groups (P>0.05); κ-Casein of arginine infusion group was the highest among groups (P<0.05). In addition, arginine infusion group had significantly higher expression in genes CSN1S1 and CSN1S2 (P<0.05), and numerically higher expression in gene CSN3 compared to the other 2 groups.

We therefore concluded that for the first time, arginine infusion increases the contents of α-Casein and κ-Casein in milk as well as their gene expressions in mammary tissue from dairy cows, which is contributed to the improvements of milk protein content and milk quality.

Keywords:  jugular infusion; arginine; milk performance; casein