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Effect of lactation feed intake and gonadotropin releasing hormone on the reproductive performance of sows



Effect of lactation feed intake and gonadotropin releasing hormone on the reproductive performance of sows



Canadian Journal of Animal Science 67(3): 715-720



Twenty-four first parity and 48 multiparity crossbred sows (Yorkshire .times. Landrace) were used in a 2 .times. 2 factorial design involving high (H) or low (L) lactation feed intakes and the intramuscular injection, or not, of 50 .mu.g of gonadotrophin-releasing hormone (GnRH) at the onset of the first postweaning estrus. All sows were weighed at farrowing and weaning. The H feed intake entailed feeding sows at levels of 10, 13, and 14% of each sow's immediate postfarrowing metabolic weight during weeks 1, 2, and 3-4 of lactation, respectively. Low-fed sows received 50% of the H feed level. The diet contained 12.5 MJ DE kg-1 and 16% crude protein. Between weaning and mating, and following mating, all sows were fed 2.25 kg daily of the lactation diet. After weaning, sows were exposed to a boar twice daily to facilitate estrus detection. GnRH was administered at the onset of standing heat. All sows were slaughtered 25 d after mating at which time the reproductive tracts were removed and examined to determine the number of ovulations and the number of viable embryos. Low-level feeding resulted in an extension of the remating interval (5.9 .+-. 0.3 vs. 4.5 .+-. 0.2 d; P < 0.05), an increased incidence of anestrus (16.7 vs. 3.6%; P > 0.1) and a reduction in pregnancy rates (69.7 vs. 81.6%; P > 0.1). Interactions were noted between lactation feeding level and GnRH injection (P < 0.05) and between parity and GnRH injection (P < 0.05) for number of viable embryos. The data obtained suggest that both low level of feeding during lactation and a young age are associated with decreased embryo numbers, but this situation is alleviated by the administration of GnRH.

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Accession: 005249775

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