Amino acid needs of lactating dairy cows: Impact of feeding lysine in a ruminally protected form on productivity of lactating dairy cows

摘要: Abstract Increased milk production requires high intakes of crude protein in the diet, and/or improved supply and ratios amino acids (AAs) delivered to duodenum order meet animal needs for synthesis. The objective this study was estimate rumen escape potential a ruminally protected lysine product (RPL) determine effects feeding on feed intake digestibility, as well composition, producing dairy cows. experiment designed double ( i.e. , early mid lactation cows) 2 × 2 factorial with 28 d experimental periods. All cows were fed same total mixed ration (TMR), calculated be first limiting lysine, treatment pens receiving 17 kg/pen/d RPL (to deliver 41 g lysine/cow/d) into TMR. Evaluation our suggested that level between 9 10 g/d intestinally absorbable lysine. Feeding did not influence dry matter or milk, true lactose yields. However fat yield concentration decreased, while urea N levels increased when fed. Blood plasma most AA, except decreased fed, suggesting its supplementation led absorption utilization other AA. lack response synthesis, decrease 3-methylhistidine concentrations, suggests muscle synthesis may have been stimulated, degradation reduced, supplementation. It is possible had an effect, either directly indirectly, turnover energy metabolism impacted intakes, production, these However, based upon results, use advisable practice at time due negative outcomes predictability needs.