Department of Animal Biosciences, University of Guelph, Guelph, ON N1G 2W1, Canada.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae094.
Fifty-two multiparous sows (average parity 3.1 ± 0.9 and initial BW 245.6 ± 32.5 kg) were used to evaluate the effects of dietary standardized ileal digestible (SID) Lys-to-net energy (NE) ratios on nitrogen (N) utilization throughout a 24-d lactation period. Sows were randomly assigned to one of five isoenergetic feeding programs that provided equally spaced and increasing SID Lys-to-NE ratios between 2.79 and 5.50 g SID Lys/Mcal NE. The feeding programs were generated by blending the two extreme diets in varying proportions and were provided to sows immediately after farrowing (day 1) and until weaning at day 24 ± 1. Nitrogen balances were conducted between days 4 and 7, 12 and 15, and 20 and 23 ± 1 of lactation to represent weeks 1, 2, and 3, respectively, using total urine collection and fecal grab sampling. Contrast statements were used to determine the linear and quadratic effects of increasing Lys-to-NE ratios. Linear and quadratic broken-line and polynomial quadratic (QPM) models were used to determine the optimum dietary Lys-to-NE ratios for N retention in milk. The Bayesian information criterion was used to assess the best fit. Feeding program did not influence sow average daily feed intake (5.8 ± 0.1 kg), BW change (-8.2 ± 3.1 kg), or change in back fat thickness (-2.6 ± 0.7 mm) over the 24-d lactation period, but piglet average daily gain increased with dietary SID Lys-to-NE ratio (linear; P < 0.05). Sow N intake increased with increasing dietary Lys-to-NE ratio in weeks 2 and 3 (linear; P < 0.001). Whole-body N retention (N intake - N output in urine and feces) increased with increasing dietary Lys-to-NE ratio in all weeks (linear; P < 0.05). The N retention in milk tended to increase then decrease with increasing dietary Lys-to-NE ratio in weeks 1 and 2 (quadratic; P = 0.051 and P = 0.081) and the QPM showed optimal milk N retention at 4.28, 4.42, and 4.67 g Lys/Mcal NE for weeks 1, 2, and 3, respectively. Maternal N retention (N intake - N output in urine, feces, and milk) decreased and then increased in week 1 (quadratic; P < 0.01) and increased in weeks 2 and 3 (linear; P < 0.01) with increasing dietary Lys-to-NE ratio. Therefore, the SID Lys-to-NE ratio necessary to optimize milk N output is dynamic throughout lactation. A two-diet feeding program could be created to match optimal weekly or daily SID Lys-to-NE ratios, which could lead to improved piglet ADG and body weights at weaning.
52 头经产母猪（平均胎次 3.1±0.9，初始 BW 245.6±32.5kg）用于评估日粮可消化真蛋白（SID）赖氨酸与净能（NE）比值对整个 24d 泌乳期氮（N）利用的影响。母猪随机分配到 5 种等能量的饲养方案中，这些方案提供了 2.79 至 5.50g SID 赖氨酸/Mcal NE 之间的等间距和逐渐增加的 SID 赖氨酸与 NE 比值。这些饲养方案通过混合两种极端饲料以不同比例生成，并在分娩后（第 1 天）立即提供给母猪，直到第 24±1 天断奶。在泌乳的第 4-7、12-15 和 20-23±1 天进行氮平衡，以分别代表第 1、2 和 3 周，使用全尿收集和粪便抓取采样。使用对比陈述来确定赖氨酸与 NE 比值增加的线性和二次效应。使用折线和二次多项式（QPM）模型来确定泌乳期牛奶中氮保留的最佳日粮赖氨酸与 NE 比值。贝叶斯信息准则用于评估最佳拟合。在 24d 的泌乳期间，饲养方案不影响母猪的平均日采食量（5.8±0.1kg）、BW 变化（-8.2±3.1kg）或背脂厚度变化（-2.6±0.7mm），但仔猪的平均日增重随日粮 SID 赖氨酸与 NE 比值增加（线性；P<0.05）。母猪的氮摄入量随日粮赖氨酸与 NE 比值的增加在第 2 和第 3 周呈线性增加（P<0.001）。在所有周，全身氮保留（氮摄入量-尿和粪便中的氮排泄量）随日粮赖氨酸与 NE 比值的增加而线性增加（P<0.05）。第 1 和第 2 周，随着日粮赖氨酸与 NE 比值的增加，牛奶中的氮保留量呈先增加后减少的趋势（二次；P=0.051 和 P=0.081），QPM 显示第 1、2 和 3 周牛奶中氮保留的最佳值分别为 4.28、4.42 和 4.67g 赖氨酸/Mcal NE。第 1 周，母体氮保留（氮摄入量-尿、粪和奶中的氮排泄量）先减少后增加（二次；P<0.01），第 2 和第 3 周呈线性增加（P<0.01），随日粮赖氨酸与 NE 比值的增加而增加。因此，优化牛奶氮输出所需的 SID 赖氨酸与 NE 比值在整个泌乳期是动态的。可以创建一个两餐制的饲养方案来匹配最佳的每周或每日 SID 赖氨酸与 NE 比值，这可以提高仔猪的 ADG 和断奶体重。
