Department of Animal and Poultry Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
J Anim Sci. 2013 Oct;91(10):4817-25. doi: 10.2527/jas.2013-6290. Epub 2013 Aug 29.
Immunization against GnRH reduces the occurrence of boar-taint-causing compounds in entire male pigs and is likely to alter growth performance, including whole-body protein deposition (PD; N retention × 6.25). Thirty-six male pigs were used to determine the effects of immunization against GnRH with GnRH analog on N retention and plasma urea nitrogen (PUN; a measure of AA catabolism). Four treatments were used: 1) conventional, early castrates (EC), 2) entire male pigs (EM), 3) entire male pigs immunized with GnRH analog (IM), and 4) entire male pigs surgically castrated after 6 wk of age (between 25 and 40 kg BW; late castrates; LC). The GnRH analog was injected at 30 and 70 kg BW. Within each of 9 litters, 4 males were randomly assigned to the 4 treatments. Pigs were fed corn- and soybean-meal-based diets that were not limiting in essential nutrients for high PD. Five consecutive N balances were conducted between d -9 and -4, 1 and 7, 9 and 16, 20 and 26, and 30 and 36, relative to administration of the booster dose of GnRH analog at d 0. Blood was sampled on d -4, -1, 2, 5, 8, 11, 14, 19, 28, and 37. There was an interactive effect of treatment and time on N retention (P < 0.001). Across periods, N retention for EC and LC were similar (32.7 vs. 33.6 g/d) and lower than EM (39.2 g/d, P < 0.001). The N retention in EM and IM were similar up to d 7 (37.8 vs. 38.5 g/d), tended to be greater for EM than IM between d 9 and 16 (38.4 vs. 34.9 g/d, P = 0.07) and was greater for EM than IM after d 20 (40.9 vs. 34.9 g/d, P < 0.05). Between d 9 and 36, N retention in IM was similar to EC and LC. The PUN concentrations were similar in EC and LC across sampling times (15.50 vs. 15.86 mg/dL) and greater than EM (9.33 mg/dL, P < 0.05). The PUN concentrations were similar in EM and IM up to d 5 (9.88 vs. 9.59 mg/dL), tended to be less in EM than IM on d 8 (9.08 vs. 11.85 mg/dL, P < 0.10), and were lower in EM than IM from d 11 to 37 (8.94 vs. 14.80 mg/dL, P < 0.05). After d 8, PUN concentrations were similar for IM, EC, and LC (14.31, 15.13, and 15.55 mg/dL, respectively). In conclusion, the results of the current study show that N retention and PUN patterns in EC and LC are very similar and lower than those in EM. Between d 7 and 16 after administration of the booster dose of GnRH analog, N retention and PUN in IM changed gradually from EM levels to approach levels in EC and LC, which should be considered when developing feeding programs for IM.
免疫 GnRH 可减少整个公猪中引起公猪异味的化合物的发生，并且可能改变生长性能，包括全身蛋白质沉积（N 保留×6.25）。使用 36 头公猪确定用 GnRH 类似物免疫 GnRH 对 N 保留和血浆尿素氮（PUN；AA 分解代谢的衡量标准）的影响。使用了 4 种处理方法：1）常规，早期去势（EC），2）整个公猪（EM），3）用 GnRH 类似物免疫的整个公猪（IM）和 4）6 周龄后（25 至 40kgBW；晚期去势；LC）手术去势的整个公猪。在 30kg 和 70kgBW 时注射 GnRH 类似物。在 9 个窝中，每个窝中的 4 个公猪随机分配到 4 种处理方法中。猪饲喂基于玉米和大豆的日粮，这些日粮在高 PD 方面不受必需营养素的限制。在 GnRH 类似物的助推剂量施用后的第-9 天至-4 天、第 1 天至 7 天、第 9 天至 16 天、第 20 天至 26 天和第 30 天至 36 天之间，连续进行了 5 次氮平衡。在第-4 天、-1 天、2 天、5 天、8 天、11 天、14 天、19 天、28 天和 37 天采集血液。处理和时间对 N 保留有交互作用（P<0.001）。在各时期，EC 和 LC 的 N 保留相似（32.7 和 33.6g/d），低于 EM（39.2g/d，P<0.001）。EM 和 IM 的 N 保留在第 7 天之前相似（37.8 和 38.5g/d），在第 9 天至 16 天之间，EM 比 IM 趋于更高（38.4 和 34.9g/d，P=0.07），在第 20 天之后，EM 比 IM 更高（40.9 和 34.9g/d，P<0.05）。在第 9 天至 36 天之间，IM 的 N 保留与 EC 和 LC 相似。在整个采样时间内，EC 和 LC 的 PUN 浓度相似（15.50 和 15.86mg/dL），并且高于 EM（9.33mg/dL，P<0.05）。在第 5 天之前，EM 和 IM 的 PUN 浓度相似（9.88 和 9.59mg/dL），在第 8 天，EM 比 IM 有下降趋势（9.08 和 11.85mg/dL，P<0.10），从第 11 天到第 37 天，EM 比 IM 更低（8.94 和 14.80mg/dL，P<0.05）。第 8 天后，IM、EC 和 LC 的 PUN 浓度相似（14.31、15.13 和 15.55mg/dL）。总之，当前研究的结果表明，EC 和 LC 的 N 保留和 PUN 模式非常相似且低于 EM。在 GnRH 类似物助推剂量给药后的第 7 天至 16 天之间，IM 的 N 保留和 PUN 逐渐从 EM 水平变化，接近 EC 和 LC 的水平，在为 IM 制定饲养计划时应考虑这一点。
