THE EFFECTS OF FOOD-INTAKE DURING LACTATION AND POST-WEANING ON THE REPRODUCTIVE-PERFORMANCE AND HORMONE AND METABOLITE CONCENTRATIONS OF PRIMIPAROUS SOWS

The objective of this study was to investigate the effect of low food intake on post-weaning fertility and hormone concentrations in primipa rous sows. One hundred and forty primiparous sows (Landrace x Large Wh ite) were randomly assigned to one of four treatment groups: (A) restr icted to 3 kg food per day during lactation and 2 kg food per day post weaning (no. = 36); (B) restricted to 3 kg food per day during lactat ion and ad libitum feeding post weaning (no. = 33); (C) ad libitum fee ding throughout with a mean voluntary food intake of 3.7 kg/day during lactation (no. = 36); and (D) ad libitum feeding throughout with a me an voluntary food intake of 4.9 kg/day during lactation (mo. = 35). Li tters were standardized at eight to 10 pigs at 2 days post partum and were weaned at 27.2 (s.e. 0.5) days post partum. After weaning, sows w ere observed twice daily for signs of oestrus and were mated on the da y(s) of standing oestrus. Six sows from each group were fitted with in dwelling jugular cannulae 2 days before weaning. Blood samples were co llected 1 day before weaning (W-1), 1 clay after weaning (W+1) and 4 d ays after weaning (W+4), and these sows were slaughtered on W+4. Ovari es wee recovered,follicles and corpora lutea were counted, and follicu lar fluid collected. Sows given food at a restricted level groups A an d B) lost more backfat during lactation than sows given food ad libitu m (groups C and D) (P < 0.01). Piglet weaning weights, weaning to conc eption intervals and the proportion of sows ovulating by W+4 were not significantly different among groups. In sows that did not ovulate, nu mbers of large follicles were not significantly different among groups but the low food intake (groups A, B and C) sows had more medium-size d follicles than high food intake (group D) sows (P < 0.01). Follicula r fluid concentrations of oestradiol, progesterone and insulin-like gr owth factor-1 (IGF-1) did not differ among groups (P > 0.05). Plasma n on-esterified fatty acids concentrations were ter in groups C and D th an in groups A and B on W-1, W+1 and W+4. Serum insulin and plasma glu cose concentrations were lower in groups C and D than in groups A and B on W-1 and W+1, but were similar among groups on W+4. Serum growth h ormone concentrations were lower in group D than group A and B on W-l and W+1 but not W+4. Concentrations of IGF-1 in serum were greater in groups C and D than groups A and B on W-l and W+1 but not W+4. It is c oncluded that low food intakes during lactation and post weaning affec ted body condition, serum hormones and metabolites and ovarian functio n of primiparous sows without dramatically affecting ovarian hormones or reproductive performance.