Variation in rate of body weight gain during pregnancy in beef heifers: association with early life health events and influence on progeny performance

Abstract Nutrient status during pregnancy can impact fetal development and progeny performance in beef females. Many experimental models have examined the impact of reduced nutrient status during late gestation because 75% of fetal growth occurs after 200 days of gestation. More recently, experimental models evaluated the impacts of nutritional status during the first trimester on organ development and progeny performance. The current study examined the variation in ADG during the first trimester (ADG1) in combination with variation in ADG during the last two trimesters (ADG23) of pregnancy and their relationship to progeny performance in beef heifers (n = 2,305) bred by bulls during the breeding season with no form of synchronization of estrus. We further examined the association between early life health events and rate of body weight (BW) gain of heifers during pregnancy. We hypothesized that there would be inherent variation in rate of BW gain during pregnancy among heifers, that this variation would influence progeny performance even when estrus was spread across the breeding season, and that heifers with reduced rates of BW gain during gestation would have an increased number of health events that coincided with the reduced rates of BW gain. Patterns of BW gain were classified as low (L, < median) or high (H, > median) for the first trimester (ADG1) and for the last two trimesters (ADG23), resulting in four patterns of gain for the dams (LL, LH, HL, or HH). Heifers in the LL group produced offspring with the lightest weights at birth and weaning, while heifers in the HH group produced offspring with greatest weights at birth and weaning (P