Nutritional modification of body composition and the consequences for reproductive performance and longevity in genetically lean sows

Abstract

The selection for reduction in carcass fat content has resulted in the development of genetically lean sows that can experience reproductive problems. This experiment investigated the production consequences of applying a nutritional regime designed to promote and conserve body fat reserves in such animals. Fat accretion before and during pregnancy was encouraged by the use of a low-protein diet to restrict lean tissue growth, while fat loss in lactation was minimised by provision of a high-nutrient density diet. Two hundred and forty purebred Landrace and Large White gilts were allocated either to this fat-promoting regime or to a single, medium-density diet regime, most common in UK commercial practice at the time, at six months of age. Growth and performance parameters were monitored over three parities. Animals subject to the experimental regime achieved greater backfat thickness at first farrowing (19.5 vs. 18.3 sed 0.49 mm), had reduced liveweight loss (Parity 1: 11.4 vs. 22.5 sed 1.51 kg; Parity 2: 11.3 vs. 22.3 sed 1.53 kg, Parity 3: 13.6 vs. 18.8 sed 1.87 kg) and backfat loss (Parity 1: 4.1 vs. 5.5 sed 0.38 mm; Parity 2: 3.1 vs. 4.3 sed 0.33 mm; Parity 3: 2.8 vs. 3.9 sed 0.37 mm) in each lactation, and required less feed in each gestation to attain acceptable body condition for farrowing (Parity 1: 2.30 vs. 2.50 sed 0.004 kg; Parity 2: 2.52 vs. 3.07 sed 0.031 kg; Parity 3: 2.59 vs. 3.12 sed 0.039 kg day −1). Litter size and piglet performance were not affected, but experimental sows had shorter weaning-to-conception intervals (Parity 1: 0.77 vs. 0.61 conceived within 7 days; Parity 2: 0.82 vs. 0.71 within 5 days). The experimental regime also had a lower proportion of animals failing to produce three litters (0.17 vs. 0.30) and culled for reproductive failure (0.03 vs. 0.11). The results indicate that the use of nutritional strategies to increase body fat reserves can improve fertility and longevity in genetically lean, young breeding sows.