Smith D E, Hixon D L, Moore D W, Van Kirk E A, Alexander B M, Anthony R V, Moss G E
Department of Animal Science, University of Wyoming, Laramie 82071, USA.
Domest Anim Endocrinol. 1996 Nov;13(6):469-76. doi: 10.1016/s0739-7240(96)00089-6.
Two-year-old crossbred beef heifers were used to test the effects of porcine relaxin (pRelaxin) alone, or in combination with dexamethasone, on the induction of parturition, the incidence of dystocia, and retained placentas. Effects of treatment on pelvic area, postpartum interval, milk production, colostrum quality, calf birth weight, calf vigor, and calf performance were also evaluated. On Day 275 of gestation, heifers from two fetal-sire groups were randomly assigned to one of four groups in a 2 x 2 factorial design and received; no treatment (controls, n = 19), 20 mg of dexamethasone intramuscularly (im) (n = 22), 5 mg of pRelaxin (3,000 U/mg) im (n = 19), or 20 mg of dexamethasone plus 5 mg of pRelaxin (n = 17). Length of gestation (in days) was less (P < 0.05) in heifers treated with dexamethasone (279.8 +/- 1.0) than in controls (286.6 +/- 0.9), but was not influenced (P > 0.05) by treatment with pRelaxin. The incidence of retained placentas in heifers treated only with dexamethasone (27.3%) was not reduced by concomitant treatment with pRelaxin (35.3%). Retained placentas were not observed in any control heifers and in only one heifer (5.2%) treated solely with pRelaxin. Ease of calving (1 = unassisted, 5 = abnormal presentation) was not influenced by treatment (P > 0.05), even though birth weights (in kilograms) of calves from heifers treated with dexamethasone (36.4 +/- 0.8) were less (P < .01) than those of calves from nondexa-methasone-treated heifers (39.2 +/- 0.8). Dexamethasone tended to reduce (P < 0.07) calf vigor (1 = healthy and strong, 5 = dead on arrival; 1.48 +/- 0.11 vs. 1.18 +/- 0.11), but was not (P > 0.05) influenced by pRelaxin. The duration of the postpartum anestrous interval (73.1 +/- 1.8 d across groups) and pelvic areas following treatment and parturition were not influenced (P > 0.05) by dexamethasone or pRelaxin. Although determinants of colostrum quality (P < 0.01) and quantity (P < 0.08) of milk produced were influenced by dexamethasone, adjusted 205-d weights of calves did not differ (P > 0.05) among groups. In conclusion, treatment with pRelaxin alone failed to induce parturition or, when combined with dexamethasone, to reduce the incidence of retained placentas.
选用两岁的杂交肉用小母牛来测试单独使用猪松弛素（pRelaxin）或其与地塞米松联合使用对引产、难产发生率和胎盘滞留的影响。还评估了治疗对骨盆面积、产后间隔、产奶量、初乳质量、犊牛出生体重、犊牛活力和犊牛性能的影响。在妊娠第275天，将来自两个父系胎儿组的小母牛按照2×2析因设计随机分为四组并接受以下处理：不治疗（对照组，n = 19）、肌肉注射（im）20 mg地塞米松（n = 22）、肌肉注射5 mg pRelaxin（3,000 U/mg）（n = 19）或20 mg地塞米松加5 mg pRelaxin（n = 17）。用地塞米松治疗的小母牛的妊娠期（天数）（279.8±1.0）比对照组（286.6±0.9）短（P < 0.05），但pRelaxin治疗对此无影响（P > 0.05）。仅用地塞米松治疗的小母牛中胎盘滞留的发生率（27.3%）并未因同时使用pRelaxin（35.3%）而降低。在任何对照组小母牛以及仅用pRelaxin治疗的小母牛中均未观察到胎盘滞留（仅1头小母牛，5.2%）。产犊难易程度（1 = 无需协助，5 = 胎位异常）不受治疗影响（P > 0.05），尽管用地塞米松治疗的小母牛所产犊牛的出生体重（千克）（36.4±0.8）比未用地塞米松治疗的小母牛所产犊牛的出生体重（39.2±0.8）轻（P < 0.01）。地塞米松倾向于降低（P < 0.07）犊牛活力（1 = 健康强壮，5 = 出生即死亡；1.48±0.11对1.18±0.11），但不受pRelaxin影响（P > 0.05）。产后乏情期的持续时间（各组平均为73.1±1.8天）以及治疗和分娩后的骨盆面积不受地塞米松或pRelaxin影响（P > 0.05）。尽管产奶的初乳质量（P < 0.01）和产量（P < 0.08）的决定因素受地塞米松影响，但各组犊牛调整后的205天体重并无差异（P > 0.05）。总之，单独使用pRelaxin未能引产，与地塞米松联合使用时也未能降低胎盘滞留的发生率。
