Effects of age at first breeding and dietary energy levels during the rearing period of replacement gilts on reproductive performance

Abstract

Context The occurrence of second parity syndrome is a major reason for culling sows depending on the bodyweight and energy level balance during the first lactation. Equally, the nutrition of gilts during the rearing period influences the age of first oestrus, longevity and reproductive performance. Aims The experiment investigated: (1) the influence of gilt mating age (early [EL], middle [MD] and late [LT]) at the first parity on reproductive performance, and (2) the interaction between dietary energy levels (high, 3320 kcal/kg; low, 3120 kcal/kg) and mating age. Methods A total of 120 crossbred (Duroc × Landrace × Yorkshire) gilts were allotted to six treatments according to a 3 × 2 factorial arrangement based on mating age (EL [222 days], MD [244 days] and LT [264 days]) at the first parity and dietary energy levels (high, 3320 kcal/kg; low, 3120 kcal/kg). The average weight of gilts were 141 ± 3, 153 ± 3 and 164 ± 3 for the EL, MD and LT groups, respectively. Results High-energy diets tended to increase the growth rate of gilts (P = 0.083). At insemination, bodyweight and back-fat thickness were higher (P < 0.05) in the LT group. Back-fat thickness at farrowing was lower (P < 0.05) in the EL group. The back-fat thickness loss during lactation was highest in the LT group (P < 0.05) during parity one and two. Feed intake during lactation was significantly reduced (P < 0.05) in the LT gilts in parity one. Insemination age and dietary energy levels had no significant effects on, litter size, litter weight and weaning to oestrus interval. A higher blood insulin-like growth factor (P < 0.05) was observed in the EL gilts during the first service and weaning. Conclusion Based on these findings, early inseminated gilts had a lower bodyweight loss during lactation without affecting litter size or growth, which in the long term may positively impact culling age. Implication This information may guide swine farmers on the most appropriate age to breed gilts at first service for increased reproductive life. The provision of high-energy feeds did not translate into any meaningful interaction towards improving reproductive performance in gilts.