Abstract
Abstract. A total of 984 primiparous and multiparous crossbred sows (Swedish Landrace × Large White) housed on a commercial pig farm were used to study the effect of the decrease in backfat thickness during lactation and the level of backfat at weaning on weaning-to-oestrus interval and conception rate of sows. Primiparous sows (n=213) received a single injection of 400 IU eCG + 200 IU hCG (PG600®, Intervet) at weaning and approximately 30 % of sows did not respond to the first treatment. First-farrowing sows produced significantly fewer live-born piglets, had markedly thinner backfat in late gestation, showed significant loss of backfat thickness during lactation and showed thinner backfat at weaning than sows with a greater number of parities. Primiparous sows with backfat thinner than 18 mm at weaning lost an average of 21 % of backfat during lactation and had a significantly longer weaning-to-oestrus interval (31.75 ± 2.22 days), even after a second treatment with PG600®, than both primiparous sows which responded to the first treatment (5.95 ± 0.16 days) and multiparous sows which were not treated (5.19 ± 0.12 days). The primiparous and multiparous sows with thicker backfat at farrowing also had thicker backfat at weaning (r=0.874 and r=0.938 for primiparous and multiparous sows, respectively). Sows with thicker backfat at weaning showed a shorter weaning-to-oestrus interval and this correlation was higher for primiparous than for multiparous sows (r=−0.192 and r=−0.100, respectively). Thicker backfat of the sows at weaning was moderately but significantly correlated with lower loss of backfat during lactation (r=−0.179 and r=−0.273 for primiparous and multiparous sows, respectively). The present study showed that monitoring of backfat thickness and loss of backfat during lactation represents a useful tool to decrease non-productive days and improve the efficiency of high-producing pig herds.
Highlights
The weaning-to-oestrus interval corresponds to the period between the day of weaning and the first day the sow is showing standing heat
Together with the limited body fat reserves of contemporary pig breeds, the extensive catabolism of body reserves can have a negative influence on the duration of the weaning-to-oestrus period (YANG et al, 1989; STERNING et al, 1990; PRUNIER et al, 1993; TANTASUPARUK et al, 2001a; THAKER and BILKEI, 2005)
Data from several studies have shown that backfat levels lower than 14 mm (YOUNG et al, 1991; HUGHES, 1993; TANTASUPARUK et al, 2001b) and thicker than 25 mm affect subsequent reproductive performance of sows (WHITTEMORE, 1996; WÄHNER et al, 2001a)
Summary
The weaning-to-oestrus interval corresponds to the period between the day of weaning and the first day the sow is showing standing heat It is influenced by lactation length (POLEZE et al, 2006) and lactation weight loss (THAKER and BILKEI, 2005), parity number (HEIDLER and HENNE, 1989), litter size (for review see, EISSEN et al, 2000), season (PRUNIER, 1996), nutrition (WHITTEMORE, 1996), genetics (for review see RYDHMER, 2000), disease status and management (DIAL et al, 1992). Sows that end the lactation period with excess weight loss or decreased backfat thickness can be expected to have a longer weaning-to-oestrus interval in the cycle of reproduction, as well as a decreased level of conception at the following mating (EISSEN et al, 2000). All first-farrowing sows had been stimulated with PG600® on the day following weaning
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