Effect of insulin administration before weaning on reproductive performance in feed-restricted primiparous sows

The objective of this study was to determine whether exogenous insulin administration in late lactation can improve reproductive performance of feed-restricted primiparous sows. A total of 24 pure Large White gilts were assigned at farrowing to one of the three following experimental groups. Control sows (CTRL) were fed on a plane of nutrition close to ad libitum and received 6 kg food day−1. Restricted saline-treated (RS) and insulin-treated (RI) sows received only 4 kg food day−1. Sows from RI group received 0.4 IU insulin per kg of live weight once daily during the 5-day pre-weaning period, whereas CTRL and RS sows received saline injections as a sham treatment. Litters (8–10 piglets) were weaned at 23.5±1 days post-partum. Blood samples were collected 2 days before (Day W−2) and after weaning (Day W+2). Restricted sows RS and RI lost significantly more weight than CTRL sows (25 kg and 32 kg, respectively, vs. 10 kg) and more fat (5.3 mm and 4.7 mm, respectively, vs. 2.2 mm). During insulin treatment, daily litter weight gain was lower in RI than in RS and CTRL groups (P<0.05). On Day W−2, insulin concentration was higher, while that of glucose was lower in RI than in RS and CTRL sows (P<0.05). Concentrations of NEFA and IGF-I were similar in the three groups of sows. On Day W+2, concentrations of FSH and oestradiol-17β did not differ significantly between females of the different groups. Weaning-to-oestrus interval and ovulation rate were similar in CTRL, RS and RI females (5.7, 5.9 and 5.6 days; 19.2, 20.7 and 22.1 corpora lutea, respectively). We concluded that insulin administration during late lactation to feed-restricted primiparous sows did not improve weaning-to-oestrus interval and post-weaning ovulation rate, but was likely to decrease milk production.