科研之友
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摘要
Early lactation dairy cows are frequently in negative energy balance and susceptible to ketosis, fatty liver and metritis. Because of its anti-lipolytic properties, the B-vitamin niacin could reduce negative energy balance by reducing non-esterified fatty acids for ketogenesis, thereby reducing hyperketonemia. We determined effects of feeding ruminally protected niacin (RPNi) on lipolysis during the fresh period using blood non-esterified fatty acids concentrations as a ketosis indicator, blood beta-hydroxybutyrate concentrations as an indicator of lipid mobilisation, as well as dry matter (DM) intake, milk and milk component yields, in 906 multi-parity Holstein cows from similar to 14 days before calving through the immediate fresh period. Prior to calving, cows were co-mingled in one pen and fed the same total mixed ration without RPNi. Between 24 and 36 h postpartum, cows were assigned to fresh pens and fed the same fresh cow total mixed ration, except for RPNi at 0, 3.5, 7 or 14 g niacin/cow. day. During the close-up and fresh periods, cows were sampled for tail vein blood. Milk yield and composition was measured twice at a 140-days interval in the fresh pens postpartum. The 3.5 g/day RPNi feeding tended to decrease ketosis prevalence (% of cows with beta-hydroxybutyrate >= 1.44 mg/dL) from 36% to 20% (P = 0.06) and also tended (P = 0.07) to increase DM intake from 19.3 to 21.5 kg DM/day versus Control. The RPNi effect tended to increase with duration of RPNi feeding, with no effects at 7 +/- 3.9 days in milk, but milk (P = 0.10), milk fat (P = 0.11) and milk energy (P = 0.07) yields tending to be higher at 21 +/- 3.9 days in milk. Conversely, 14 g/day RPNi had no effect on ketosis prevalence or DM intake. However, milk (P = 0.10), milk fat (P = 0.11) and milk energy (P = 0.07) yields tended to decrease versus Control. Overall, low level RPNi feeding was judged to improve health and production in fresh cows, but higher feeding levels had clear negative impacts.
- 出版日期2017
