Department of Animal Science, South Dakota State University, Brookings, SD.
ADM Animal Nutrition, Quincy, IL.
J Anim Sci. 2019 Jul 2;97(7):3016-3026. doi: 10.1093/jas/skz169.
Two experiments were conducted to determine the efficiency of utilizing SID Lys and Thr for whole-body protein retention (kSIDLys and kSIDThr) in pregnant gilts. In Exp. 1, 45 gilts (158.0 ± 8.0 kg at day 39.4 ± 1 of gestation) in 2 groups were used in a 3-period nitrogen (N)-balance study. Gilts were assigned to 1 of 4 diets set to provide 60, 70, 80, and 90% of predicted daily SID Lys requirement for protein retention (NRC, 2012) in each of early (day 41 to 52, 10.44 g/d), mid- (day 68 to 79, 9.60 g/d), and late gestation (day 96 to 107, 16.04 g/d). Diets contained 3,300 kcal ME/kg and 11.6% CP; given at a rate of 2.13 kg/d in early and mid-gestation and at 2.53 kg/d during late gestation. The 12-d balance period (7-d adaptation; 5-d urine and fecal collection) was based on total urine collection using urinary catheters and determination of fecal N digestibility using indigestible marker. The SID Lys required for whole-body protein retention was estimated using the NRC (2012) model and the predicted Lys content of each gestation pool. Lysine efficiency at each diet Lys level was calculated as the ratio of daily Lys retention and SID Lys intake. The linear and quadratic response in whole-body N and Lys retention and Lys efficiency for each balance period was determined. The kSIDLys was determined from the slope generated by regressing whole-body Lys retention vs. SID Lys intake, with y-intercept set to 0. In Exp. 2, 45 gilts (165.7 ± 13.6 kg at day 39.1 ± 2 of gestation) were assigned to 1 of 4 diets set to provide 60, 70, 80, and 90% of the predicted daily SID Thr requirement for protein retention in each of early (6.46 g/d), mid- (6.05 g/d), and late gestation (9.75 g/d). Animal management, N-balance procedure, data collection and calculation, and statistical analyses were patterned from Exp. 1. In early and mid-gestation, whole-body N retention, as well as Lys and Thr retention, was not affected by the dietary SID Lys and Thr. In late gestation, there was a linear increase (P < 0.001) in whole-body N, Lys and Thr retention. The kSIDLys and kSIDThr in late gestation were determined to be 0.54. The lack of response in whole-body protein retention in early and mid-gestation may in partly reflect excess Lys and Thr intake. Lysine and Thr efficiency calculated at the lowest dietary Lys and Thr was 0.49 and 0.32 in early gestation and 0.61 and 0.52 in mid-gestation, respectively. Based on the available evidence, kSIDLys and kSIDThr do not appear to be constant throughout gestation.
进行了两项实验,以确定利用母猪的可利用色氨酸和苏氨酸(SID Lys 和 SID Thr)进行全身蛋白质保留的效率(kSIDLys 和 kSIDThr)。在实验 1 中,45 头母猪(妊娠 39.4 ± 1 天,体重 158.0 ± 8.0kg)在 3 个氮(N)平衡研究期内分为 2 组。母猪被分配到 4 种饮食中的 1 种,以提供蛋白质保留(NRC,2012)的每日预测可利用色氨酸需求的 60%、70%、80%和 90%,分别在早期(第 41 天至 52 天,10.44g/d)、中期(第 68 天至 79 天,9.60g/d)和后期妊娠(第 96 天至 107 天,16.04g/d)。饮食含有 3300kcal ME/kg 和 11.6%CP;在早期和中期以 2.13kg/d 的速度给予,在后期妊娠以 2.53kg/d 的速度给予。12 天的平衡期(7 天适应期;5 天尿液和粪便收集)基于使用导尿管进行的总尿液收集和使用不消化标记物测定粪便 N 消化率。使用 NRC(2012)模型和每个妊娠池的预测赖氨酸含量估计全身蛋白质保留所需的可利用赖氨酸。在每个饮食赖氨酸水平下,赖氨酸效率的计算方法是赖氨酸保留量与可利用赖氨酸摄入量的比值。确定了每个平衡期全身 N 和赖氨酸保留量以及赖氨酸效率的线性和二次反应。kSIDLys 是通过回归全身赖氨酸保留量与可利用赖氨酸摄入量确定的,y 截距设置为 0。在实验 2 中,45 头母猪(妊娠 39.1 ± 2 天,体重 165.7 ± 13.6kg)被分配到 4 种饮食中的 1 种,以提供蛋白质保留的每日预测可利用苏氨酸需求的 60%、70%、80%和 90%,分别在早期(6.46g/d)、中期(6.05g/d)和后期妊娠(9.75g/d)。动物管理、N 平衡程序、数据收集和计算以及统计分析均来自实验 1。在早期和中期,饮食中的可利用色氨酸和苏氨酸对全身 N 保留以及赖氨酸和苏氨酸保留没有影响。在后期妊娠时,全身 N、赖氨酸和苏氨酸保留量呈线性增加(P<0.001)。后期妊娠时 kSIDLys 和 kSIDThr 分别确定为 0.54。早期和中期全身蛋白质保留无反应可能部分反映了赖氨酸和苏氨酸摄入过多。在最低饮食赖氨酸和苏氨酸下计算的赖氨酸和苏氨酸效率分别为早期妊娠的 0.49 和 0.32,中期妊娠的 0.61 和 0.52。基于现有证据,SIDLys 和 SIDThr 在整个妊娠期间似乎并非恒定不变。