Effects of plane of nutrition of ewes in early and mid-pregnancy on performance of the offspring: Female reproduction and male carcass characteristics

This study investigated the effects of different planes of nutrition in early pregnancy (EP) and mid-pregnancy (MP) of crossbred ewes on carcass characteristics of male offspring and reproductive performance of female offspring. During EP (d 1 to 39 after synchronized mating) ewes were allocated 60% (low, L-EP), 100% (medium, M-EP), or 200% (high, H-EP) of their energy requirements for maintenance. Between d 40 and 90 (MP), ewes were then allocated 80% (M-MP) or 140% (H-MP) of their maintenance energy requirement. After d 90, all ewes were fed to fully meet energy requirements for late pregnancy. Male offspring (n = 83) were reared on a grass-based system and slaughtered at 42, 46, or 50 kg of BW. Female offspring (n = 60) were reared on a grass-based system, mated at 8 mo, and performance recorded until weaning of their first lamb crop. Concentrations of leptin, an adiposity indicator, in female offspring varied with the plane of maternal nutrition in early pregnancy. The L-EP off-spring had greater leptin concentrations than H-EP offspring (P = 0.04), with M-EP offspring showing intermediate concentrations. Reproductive performance of female offspring was not affected by maternal plane of nutrition (P > 0.16). Female H-EP offspring gave birth to heavier lambs (generation 2 offspring) than M-EP (P = 0.006) with L-EP offspring intermediate. Male offspring of L-EP dams showed a trend toward poorer carcass conformation (P = 0.06) and increased fat classification (P = 0.07), consistent with increased fat depths over the loin (P = 0.02). There was a significant interaction between plane of nutrition in early pregnancy and mid-pregnancy for female offspring BW at 2 mo postmating and 16 wk postlambing (P ≤ 0.04), and for male offspring perinephric and retroperitoneal fat and tissue depth (P < 0.02). For dams offered diet L-EP during early pregnancy, diet H-MP gave heavier offspring with more perinephric and retroperitoneal fat. In contrast, for dams offered diet H-EP during EP, diet M-MP gave offspring that were heavier or fatter or both. Maintenance level of nutrition in EP followed by M-MP or H-MP treatments resulted in offspring intermediate in fatness and BW. The data indicate that adaptations in EP and MP to compensate for nutritional deprivation or nutritional excess can alter the BW, adiposity, conformation, and leptin concentrations of offspring. Such changes have potential to alter health and lifetime productive performance.