The effects of food intake during lactation and post weaning on the reproductive performance and hormone and metabolite concentrations of primiparous sows

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Abstract
The objective of this study was to investigate the effect of low food intake on post-weaning fertility and hormone concentrations in primiparous sows. One hundred and forty primiparous sows (Landrace × Large White) were randomly assigned to one of four treatment groups: (A) restricted 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 lactation andad libitumfeeding post weaning (no. = 33); (C)ad libitumfeeding throughout with a mean voluntary food intake of 3·7 kg/day during lactation (no. = 36); and (D)ad libitumfeeding throughout with a mean voluntary food intake of 4·9 kg/ day during lactation (no. = 35). Litters 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 were observed twice daily for signs of oestrus and were mated on the day(s) of standing oestrus. Six sows from each group were fitted with indwelling jugular cannulae 2 days before weaning. Blood samples were collected 1 day before weaning (W−l), 1 day after weaning (W+l) and 4 days after weaning (W+4), and these sows were slaughtered on W+4. Ovaries were recovered, follicles and corpora lutea were counted, and folUcular fluid collected. Sows given food at a restricted level (groups A and B) lost more backfat during lactation than sows given foodad libitum(groups C and D) (P < 0·01). Piglet weaning weights, weaning to conception intervals and the proportion of sows ovulating by W+4 were not significantly different among groups. In sows that did not ovulate, numbers of large follicles were not significantly different among groups but the low food intake (groups A, B and C) sows had more medium-sized follicles than high food intake (group D) sows (P < 0·01). FolUcular fluid concentrations of oestradiol, progesterone and insulin-like growth factor-1 (IGF-1) did not differ among groups (P > 0·05). Plasma non-esterified fatty acids concentrations were greater in groups C and D than in groups A and B on W−l, W+l and W+4. Serum insulin and plasma glucose concentrations were lower in groups C and D than in groups A and B on W−l and W+l, but were similar among groups on W+4. Serum growth hormone concentrations were lower in group D than group A and B on W−l and W+l 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+l but not W+4. It is concluded that low food intakes during lactation and post weaning affected body condition, serum hormones and metabolites and ovarian function of primiparous sows without dramatically affecting ovarian hormones or reproductive performance.

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