Mahmoudi Vahid, Kazemi-Bonchenari Mehdi, Yazdi Mehdi Hossein, Mirzaei Mehdi
Department of Animal Science, Faculty of Agriculture and Natural Resources, Arak University, Arak, Iran.
J Anim Physiol Anim Nutr (Berl). 2025 Mar;109(2):467-476. doi: 10.1111/jpn.14061. Epub 2024 Nov 4.
We hypothesized that nitrogen (N) and phosphorus (P), as two pivotal nutrients that contributed to the growth of growing animals, may have interactive effect on growth performance and microbial development in young calves. For this purpose, feeding two starter protein contents (20% [20CP] vs. 24% [24CP], DM basis) and two phosphorus supplementation levels (0.35% [0.35P] and 0.70% [0.7P], DM basis) was evaluated on growth performance, health indicators, digestibility of nutrients and microbial protein synthesis (MPS), the latter estimated from urinary purine derivatives (PDs). Forty-eight female Holstein calves (3 days of age) were assigned randomly to the following treatments: 20CP-0.35P, 20CP-0.7P, 24CP-0.35P and 24CP-0.7P (n = 12, each). Milk feeding schedule was identical among treatments until weaning (d 59), but study lasted until d 73. Feeding 24CP compared to 20CP diet tended to improve starter intake, increased average daily gain (ADG) during pre-weaning period (p < 0.05), and final body weight (p = 0.01). Higher P supplementation has marginal effect on starter intake but improved ADG (pre-weaning; p = 0.02) and microbial activity by greater MPS (p = 0.02) compared to 0.35P. The greatest starter intake, the most favourable general appearance score, the highest withers height, the highest hip height, the greatest organic matter and neutral detergent digestibility, and the greatest MPS were found when calves fed diets contained 24CP along with 0.7P in starter. Based on the current study results, N and P have separate effects on the growth performance of young calves; however, their positive interaction can be attributable to growth performance and microbial development, especially during the pre-weaning period.
我们假设，氮（N）和磷（P）作为促进生长中动物生长的两种关键营养素，可能对犊牛的生长性能和微生物发育具有交互作用。为此，研究评估了两种起始蛋白质含量（20%[20CP]与24%[24CP]，干物质基础）和两种磷添加水平（0.35%[0.35P]和0.70%[0.7P]，干物质基础）对生长性能、健康指标、养分消化率和微生物蛋白质合成（MPS，根据尿嘌呤衍生物[PDs]估算）的影响。48头3日龄的荷斯坦雌性犊牛被随机分配到以下处理组：20CP - 0.35P、20CP - 0.7P、24CP - 0.35P和24CP - 0.7P（每组n = 12）。各处理组的喂奶计划在断奶前（第59天）相同，但研究持续到第73天。与20CP日粮相比，饲喂24CP日粮倾向于提高起始料采食量，增加断奶前期的平均日增重（ADG）（p < 0.05）和最终体重（p = 0.01）。与0.35P相比，较高的磷添加量对起始料采食量有边际效应，但通过更高的MPS提高了ADG（断奶前；p = 0.02）和微生物活性（p = 0.02）。当犊牛饲喂的日粮在起始料中含有24CP和0.7P时，起始料采食量最大、总体外观评分最有利、肩高最高、臀高最高、有机物和中性洗涤纤维消化率最高以及MPS最大。基于当前的研究结果，氮和磷对犊牛的生长性能有单独的影响；然而，它们的积极交互作用可归因于生长性能和微生物发育，尤其是在断奶前期。
