Effect of maternal nutrient restriction in early to mid gestation and thyrotrophin-releasing hormone on lamb survival following Caesarean section delivery near to term

We investigated the influence of restricted maternal nutrition between 28 a nd 77 days gestation on survival and thermoregulatory adaptation following Caesarean section delivery near to term. This study was designed to examine the hypothesis that adaptation after birth would be compromised in those l ambs born to nutrient restricted ewes. We further hypothesised that this wo uld be due in part to inadequate hypothalamic-pituitary-thyroidal function. Lambs born to nutrient restricted ewes were untreated (RU) or treated with thyrotrophin-releasing hormone (TRH; RT) immediately prior to umbilical co rd clamping. Single bearing ewes consumed either 6.60 MJ.day(-1) (controls, n = 4) or 3.00 MJ.day(-1) (nutrient restricted, n = 15) from 28-77 days ge station, after which all ewes consumed 7.20 MJ.day(-1). All lambs born to c ontrol ewes commenced continuous breathing and began to shiver following Ca esarean section delivery and survived to 6 h after birth. Only 4 out of 9 R U lambs established continuous breathing and survived to 6 h after birth co mpared with all RT lambs. Six hours after birth, RT lambs possessed periren al brown adipose tissue with a higher thermogenic activity than 6 h old RU or control lambs. Lamb birth weight was similar in all groups. In conclusio n, near-term lambs born to ewes nutrient restricted in early to mid gestati on are at increased risk of death following Caesarean section delivery. Sur vival after birth can be significantly enhanced if TRH is administered to t he lambs immediately before delivery.