Miller D R, Jackson R B, Blache D, Roche J R
Tasmanian Institute of Agricultural Research, Mt. Pleasant, Tasmania, 7250, Australia.
J Anim Sci. 2009 Oct;87(10):3167-78. doi: 10.2527/jas.2009-1825. Epub 2009 Jun 19.
Perinatal mortality is a major contributing factor to reproductive wastage in grazing sheep industries. Enhanced metabolic and endocrine maturity at birth may improve the behavioral competency and thermoregulatory ability of neonates, potentially improving lamb survival over the first 72 h of life. Maternal glucocorticoid treatment in late gestation was investigated as a mechanism for manipulating metabolic and endocrine maturity in the ovine neonate. Multiparous, fine-wool Merino ewes (n = 150) were divided into 3 groups to lamb on pasture. Within each group, 5 single-lamb and 5 twin-lamb bearing ewes were randomly allocated to 1 of 5 treatments. Treatments included a saline control (1 mL), or dexamethasone (2 mg/mL as the sodium phosphate) injected intramuscularly at 1 of 2 dose rates (1.5 or 3.0 mg) at d 130 or 141 of gestation. One-half of the control ewes were injected at d 130 and the remainder at d 141. Dexamethasone treatment had no effect on lamb survival to 72 h after birth, although there tended (P = 0.09) to be a smaller proportion of lambs dying due to dystocia than for control lambs. Heart girth at birth in singleton and twin lambs was reduced (P < 0.01) at the greater dose rate. Further, treatment also reduced birth weight (by about 5%) and presuckling rectal temperatures in twin lambs, but not in singleton lambs. These reductions were also dependent on the sex of the lamb. Dexamethasone treatment did not alter gestation length or lamb presuckling plasma glucose, NEFA, urea, or leptin concentrations, but treatment at d 141 increased (P < 0.05) ghrelin concentrations in singleton and male lambs. Behavioral interactions between ewes and neonatal lambs were generally unaffected, although treatment at d 130 produced lambs that took longer to bleat than lambs of untreated ewes (P < 0.05). Treatment did not affect the concentration of measured blood metabolites or hormones at weaning. Although there were interactions between litter size, lamb sex, and the dose rate and time of treatment on weaning weight, BW recorded 73 d after weaning was unaffected by treatment. Despite changes in birth weight, rectal temperature, lamb behavior, and presuckling plasma ghrelin concentrations, survival in the first 72 h of life, and lamb growth performance were unaffected by periparturient maternal glucocorticoid treatment.
围产期死亡率是放牧绵羊产业繁殖损耗的一个主要促成因素。出生时增强的代谢和内分泌成熟度可能会提高新生儿的行为能力和体温调节能力,从而有可能提高羔羊出生后前72小时的存活率。研究了妊娠后期母体糖皮质激素治疗作为一种调节绵羊新生儿代谢和内分泌成熟度的机制。将150只经产细毛美利奴母羊分为3组在牧场产羔。在每组中,将5只单羔母羊和5只双羔母羊随机分配到5种处理中的1种。处理包括生理盐水对照(1毫升),或在妊娠第130天或141天以两种剂量率(1.5或3.0毫克)之一肌肉注射地塞米松(2毫克/毫升,以磷酸钠形式)。一半的对照母羊在第130天注射,其余的在第141天注射。地塞米松处理对出生后72小时内羔羊的存活率没有影响,尽管由于难产死亡的羔羊比例往往(P = 0.09)比对照羔羊小。单羔和双羔出生时的胸围在较高剂量率下降低(P < 0.01)。此外,处理还降低了双羔羔羊的出生体重(约5%)和吮乳前直肠温度,但单羔羔羊不受影响。这些降低也取决于羔羊的性别。地塞米松处理没有改变妊娠期长度或羔羊吮乳前血浆葡萄糖、非酯化脂肪酸、尿素或瘦素浓度,但在第141天处理使单羔和雄性羔羊的胃饥饿素浓度升高(P < 0.05)。母羊与新生羔羊之间的行为互动一般不受影响,尽管在第130天处理的羔羊比未处理母羊的羔羊叫出声的时间更长(P < 0.05)。处理对断奶时测量的血液代谢物或激素浓度没有影响。尽管在断奶体重上,产仔数、羔羊性别、处理剂量率和时间之间存在相互作用,但断奶后73天记录的体重不受处理影响。尽管出生体重、直肠温度、羔羊行为和吮乳前血浆胃饥饿素浓度发生了变化,但围产期母体糖皮质激素处理对出生后前72小时的存活率和羔羊生长性能没有影响。