Animal Nutrition Group, Wageningen University and Research, PO Box 338, 6700 AH Wageningen, the Netherlands; Wageningen Livestock Research, Wageningen University and Research, PO Box 338, 6700 AH Wageningen, the Netherlands.
Wageningen Livestock Research, Wageningen University and Research, PO Box 338, 6700 AH Wageningen, the Netherlands.
J Dairy Sci. 2018 Sep;101(9):7857-7870. doi: 10.3168/jds.2017-14276. Epub 2018 Jul 13.
Fifty-six Holstein-Friesian cows were used in a randomized complete block design to test the effects of supplemental energy from protein (PT) and fat (FT) on lactation performance and nutrient digestibility in a 2 × 2 factorial arrangement. During the control period, cows were adapted for 28 d to a basal total mixed ration consisting of 34% grass silage, 33% corn silage, 5% grass hay, and 28% concentrate on a dry matter (DM) basis. Experimental rations were fed for 28 d immediately following the control period and consisted of (1) low protein, low fat (LP/LF), (2) high protein, low fat (HP/LF), (3) low protein, high fat (LP/HF), or (4) high protein and high fat (HP/HF). To obtain the HP and HF diets, intake of the basal ration was restricted and supplemented isoenergetically (net energy basis) with 2.0 kg/d of rumen-protected protein (soybean + rapeseed, 50:50 mixture on DM basis) and 0.68 kg/d of hydrogenated palm fatty acids (FA) on a DM basis. Milk production and composition, nutrient intake, and apparent digestibility were measured during the final 7 d of the control and experimental periods. No interaction was found between PT and FT on milk production and composition. Yields of milk, fat- and protein-corrected milk, and lactose increased in response to PT and FT and lactose concentration was unaffected by treatment. Milk protein concentration and yield increased in response to PT, and protein yield tended to increase in response to FT. Milk fat concentration and yield increased in response to FT and were unaffected by PT. Milk urea concentration increased and nitrogen efficiency decreased in response to PT. Feed and nitrogen efficiency were highest on the LP/HF diet and both parameters increased in response to FT, whereas milk urea concentration was not affected by FT. Energy from fat increased the concentration and yield of ≥16-carbon FA in milk and decreased the concentration of FA synthesized de novo, but had no effect on their yield. Concentration and yield of de novo-synthesized FA increased in response to PT. Concentration and yield of polyunsaturated FA increased and decreased in response to PT and FT, respectively. Apparent total-tract digestibility of crude fat decreased in response to PT, and FT increased crude protein digestibility. Energy supplementation through rumen-inert hydrogenated palm FA appears to be an efficient feeding strategy to stimulate milk production with regard to feed and nitrogen efficiency compared with supplementing an isoenergetic level of rumen-protected protein.
采用完全随机分组设计，选择 56 头荷斯坦弗里生奶牛，研究饲粮中添加蛋白（PT）和脂肪（FT）对泌乳性能和养分消化率的影响，采用 2×2 因子设计。在基础日粮中，奶牛适应期 28d，基础日粮由 34%的青贮苜蓿、33%的青贮玉米、5%的干草和 28%的精料组成，干物质（DM）基础。对照组持续 28d，试验组立即开始试验，试验组饲粮分为 4 种：（1）低蛋白低脂肪（LP/LF），（2）高蛋白低脂肪（HP/LF），（3）低蛋白高脂肪（LP/HF），（4）高蛋白高脂肪（HP/HF）。为获得高蛋白高脂肪饲粮，限制奶牛采食基础日粮，额外补充 2.0kg/d 的瘤胃保护性蛋白（大豆+菜籽，按 DM 基础 50:50 混合）和 0.68kg/d 的氢化棕榈脂肪酸（FA），按 DM 基础。在对照组和试验组的最后 7d 中，分别测量产奶量、组成、养分摄入量和表观消化率。PT 和 FT 对产奶量和组成没有互作影响。产奶量、脂肪校正奶和蛋白校正奶产量以及乳糖浓度随 PT 和 FT 的增加而增加，处理对乳糖浓度没有影响。PT 增加了乳蛋白浓度和产量，FT 增加了蛋白产量。FT 增加了乳脂浓度和产量，而 PT 没有影响。PT 增加了乳尿素浓度，降低了氮效率。LP/HF 饲粮的饲料和氮效率最高，FT 增加了这两个参数，而 FT 对乳尿素浓度没有影响。饲粮脂肪能量增加了乳中≥16 碳 FA 的浓度和产量，降低了从头合成 FA 的浓度，但对其产量没有影响。PT 增加了从头合成 FA 的浓度和产量。PT 和 FT 分别增加了乳中合成多不饱和 FA 的浓度和产量，降低了产量。PT 降低了粗脂肪的全肠道表观消化率，FT 增加了粗蛋白消化率。与补充等能水平的瘤胃保护性蛋白相比，添加氢化棕榈惰性脂肪似乎是一种有效的饲养策略，可提高产奶量和饲料及氮效率。
