Milk production, plasma metabolite profiles and mammary arterial‐venous differences of milk precursors in early lactation cows milked at different frequencies by an automatic milking system

Abstract

The objective of this study was to clarify the effect of different milking frequencies under an automatic milking system (AMS) on milk yield, plasma metabolite profiles and mammary arterial-venous (A-V) differences of milk precursors by mammary tissues in early lactation cows. Twelve Holstein cows were divided into two and four times milking frequency treatments by AMS after calving to 50 days postpartum. Cows were given a partial mixed ration ad libitum and a concentrate diet at every milking. Dry matter intake increased similarly in both treatments with advancing postpartum days. Milk yield was greater (P < 0.001) by 25% with four times milking, but milk composition was not affected by milking frequency. Body weight change was also not affected by milking frequency. Arterial concentrations of glucose and glutamate were lower (P < 0.05) for four times milking frequency. However, arterial concentration of nonesterified fatty acids did not differ between treatments. Although mammary A-V differences of plasma concentration for most milk precursors did not differ between treatments, estimated plasma flow was higher (P < 0.05) for four times milking frequency. These results indicate that higher milking frequency may increase mammary uptake of milk precursors, whereas may not affect the extent of fat mobilization of early lactating cows from day 20 postpartum onward.

Changes in the expression of α-tocopherol-related genes in liver and mammary gland biopsy specimens of peripartum dairy cows

“…In the present study, the content of milk fat in colostrum was also higher than that in mature milk in dairy cows; however, the α-Toc concentrations in colostrum, which were normalized by the milk fat value (μg of α-Toc/g of milk fat), were about 5 to 8 fold greater than those in mature milk. Therefore, we attempted to confirm the active α-Toc transfer from blood into colostrum by the AVD method (Thivierge et al, 1998;Astuti et al, 2015), but the changes in the extraction ratio of α-Toc around the time of calving were masked due to a high variability (SEM range ±0.8%). Previous reports have estimated the efficiency of α-Toc transfer from blood to milk at 400 L of plasma/kg of milk produced from the blood flow through the mammary gland (Linzell, 1974;Delamaire and Guinard-Flament, 2006).…”

“…2; we did not measure the α-Toc content and chemical composition of TMR nor did we record daily individual voluntary feed intake. Blood samples from the coccygeal artery and milk vein of 5 out of 10 cows were collected to calculate the mammary arterial-venous differences (AVD) and extraction ratio of α-Toc as previously described (Thivierge et al, 1998;Astuti et al, 2015) at wk −8 (−57 to −46 d), −4 (−34 to −25 d), −1 (−15 to −5 d), 0 (within 12 h from calving), 3 (23 to 25 d), and 6 (38 to 43 d) relative to parturition. We also obtained blood samples from the cows by jugular venipuncture to compare with the data of blood α-Toc and metabolites concentrations in Exp.…”