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 g ilts were assigned at farrowing to one of the three following experime ntal groups. Control sows (CTRL) were fed on a plane of nutrition clos e to ad libitum and received 6 kg food day(-1). Restricted saline-trea ted (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 onc e 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 collect ed 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 a nd 32 kg, respectively, vs. 10 kg) and more fat (5.3 mm and 4.7 mm, re spectively, 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, concent rations of FSH and oestradiol-17 beta did not differ significantly bet ween 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 conclude d 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. (C) 1998 Elsevier Science B.V.