Gerrits W J, Tolman G H, Schrama J W, Tamminga S, Bosch M W, Verstegen M W
Wageningen Institute of Animal Sciences, Wageningen Agricultural University, The Netherlands.
J Anim Sci. 1996 Sep;74(9):2129-39. doi: 10.2527/1996.7492129x.
Two experiments were conducted to quantify the effects of protein intake on protein and fat deposition rates at two protein-free, energy intake levels in 90 preruminant Holstein Friesian x Dutch Friesian calves. The two experiments were similar in design, but were performed in two different weight ranges: 80 to 160 kg BW and 160 to 240 kg BW in Exp. 1 and 2, respectively. In each experiment, calves were allocated to either an initial slaughter group or to one of 12 treatments (three calves per treatment), which consisted of six protein intake levels at each of two protein-free energy intake levels. Calves were slaughtered and analyzed for body composition when they had reached the target weight. A balance study was conducted when calves reached 120 and 200 kg BW in Exp. 1 and 2, respectively. Protein digestibility increased with increasing protein intake in both experiments (P < .001). Average daily gain of the empty body varied between 640 and 1,340 g/d and between 420 and 1,370 g/d in Exp. 1 and 2, respectively, and was affected by protein (P < .001) and protein-free energy intake (P < .001). The calves responded to increased protein intake by increasing their protein (P < .001) and fat (P < .01) deposition rates. Maximum protein deposition was reached in the second experiment at 244 g/d. Extra protein-free energy intake resulted mainly in extra fat deposition (P < .001), but also increased the protein deposition (P < .01), even at low protein intake levels. In both experiments, the response of protein deposition rate to increased protein intakes was low: about 30% of the extra ingested protein was deposited. These results clearly demonstrate a low priority for partitioning dietary protein into protein gain in these calves.
开展了两项试验，以量化蛋白质摄入量对90头反刍前荷斯坦弗里生×荷兰弗里生犊牛在两种无蛋白能量摄入水平下蛋白质和脂肪沉积率的影响。两项试验设计相似，但在两个不同体重范围内进行：试验1和试验2的体重范围分别为80至160千克体重和160至240千克体重。在每项试验中，犊牛被分配到初始屠宰组或12种处理之一（每种处理三头犊牛），这12种处理由两种无蛋白能量摄入水平下的六种蛋白质摄入量组成。当犊牛达到目标体重时，将其屠宰并分析体成分。试验1和试验2中，犊牛分别达到120和200千克体重时进行了平衡研究。在两项试验中，蛋白质消化率均随蛋白质摄入量的增加而提高（P <.001）。试验1和试验2中，空体平均日增重分别在640至1340克/天和420至1370克/天之间，且受蛋白质（P <.001）和无蛋白能量摄入量（P <.001）的影响。犊牛通过提高蛋白质（P <.001）和脂肪（P <.01）沉积率来应对蛋白质摄入量的增加。在第二项试验中，最大蛋白质沉积量达到244克/天。额外的无蛋白能量摄入主要导致额外的脂肪沉积（P <.001），但即使在低蛋白质摄入水平下，也会增加蛋白质沉积（P <.01）。在两项试验中，蛋白质沉积率对蛋白质摄入量增加的反应都很低：摄入的额外蛋白质约30%被沉积。这些结果清楚地表明，在这些犊牛中，将日粮蛋白质分配用于蛋白质增加的优先级较低。
