Influence of maternal frame size and nutritional restriction on growth and development of the postnatal lamb

Pregnant ewes (large frame [LF] and small frame [SF]) were nutritionally stressed in early gestation (EGS), late gestation (LGS) or fed 100% of NRC requirements (unstressed, US) throughout gestation. Lambs (128) from these ewes were slaughtered at birth, weaning (18 kg), 41 kg or 55 kg. Sixty-four lambs received a 13% protein diet from weaning to either 41 or 55 kg. Lambs from SF ewes were fatter at 55 kg, had a higher numerical yield grade and a lower percentage of carcass protein. Lambs from US ewes were youngest at slaughter and had the most carcass weight and protein per day of age at 55 kg. The LGS lambs had the lowest percentage of lean and carcass protein at 41 and 55 kg. However, at birth these lambs had the highest concentration of RNA and DNA in muscle. The EGS lambs had the lowest quality grade, carcass weight per day of age and fat percentage. Muscle DNA and RNA at birth was lowest in EGS lambs. However, EGS lambs produced the highest lean percentage and highest percentage carcass protein at 41 and 55 kg. Shortest metacarpals and metatarsals were also found in these lambs at weaning and 41 kg. Although frame size had little effect on carcass characteristics, the effects of nutritional stress in the first 80 d of gestation were apparent in lambs slaughtered at 31 kg. Stress in the last 50 d of gestation had more effect on lambs slaughtered at 55 kg.