• Asian-Australasian Journal of Animal Sciences
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• v.14 no.11
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• pp.1610-1615
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• 2001

Three studies were conducted to determine the effect of sex on pre- and post-weaning performance of pigs. These studies were conducted in response to observations that female pigs appear to grow faster than male pigs after weaning. In addition, female pigs have been found to grow faster than male pigs when supplied with supplemental milk before weaning. The aims of the present work were to further characterise the ontogeny of sex differences growth of nursing and growing pigs. In the first study, piglets sucking 32 sows were crossfostered to produce litters of 10 boars (n=9), 10 gilts (n=l 1) or 5 boars and 5 gilts (n=12). Liveweight of the sucking pigs was then measured weekly until weaning at 4 weeks of age. In the second study, 80 boars and 80 gilts were weaned at 26 days of age and growth performance measured until 21 days post-weaning. In the third experiment, 40 boars and 40 gilts were weaned into groups of 5 pigs at either 17 or 25 days of age and pigs were weighed until they were approximately 90 kg liveweight. All-boar litters grew more slowly than the all-gilt and mixed litters such that by 14 days of age the all-boar litters were 10% lighter than the all-gilt or mixed litters (39 vs. 43.8 kg, p=0.050). The proportional difference in litter weight appeared to be maintained at 21 days of age (53.9 vs. 59.4 kg, p=0.063) but was diminished by 28 days of age (66.5 vs. 70.8 kg, p=0.28). In the second study, gilts grew more quickly than boars over the first 7 and 21 days post-weaning and as a consequence were 10% heavier than boars at 21 days after weaning (13.7 vs 12.48 kg, p=0.001). In the third study, gilts grew more quickly than boars in the immediate 7 days post-weaning (40 vs. 5 g/day, p=0.014) whereas from 7 until 35 days post-weaning there was no significant difference in growth rate (381 vs. 360 g/day, p=0.19). Gilts also grew more quickly than boars over the 14 days after being moved into the grower (631 vs. 570 g/day, p=0.013) and finisher (749 vs. 688 g/day, p=0.038) sheds. However, these differences were not maintained over the entire period in each shed. These data support the hypotheses that gilts handle the stresses of weaning and other transitions better than boars.

• Journal of Animal Science and Technology
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• v.45 no.1
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• pp.33-40
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• 2003

The present study was undertaken to find relationships of plasma insulin-like growth factor (IGF)-I and IGF-II concentrations to litter size and lactation performance. Sixty pure-bred Landrace and Yorkshire pigs having similar farrowing weeks which had been selected from a large number of pregnant gilts and sows were divided into low- (<${\mu}$－0.5SD) and high-litter size (>${\mu}$+0.5 SD) lines under a 2 (breed)${\times}$2 (line) factorial arrange of treatments. After adjusting the litter size to nine piglets per sow at farrowing, total litter weight was measured at three weeks postpartum at weaning as an index of milk yield. Blood samples were obtained from the jugular vein at day (d)-90 pregnancy (Px) and at d-15 postpartum. The litter size or the number of piglets born during the present experiment and the average litter size during the entire parities up to the present one were greater in the high-line than in the low-line by 3.7 and 2.4 piglets, respectively (P<0.01); effect of the breed on litter size was not significant. Plasma IGF-II concentration at d-90 Px was greater in the high-line than in the low-line. Litter size and d-90 Px IGF-I concentration were negatively correlated in Landrace (r=－0.46; P<0.05) and tended to be negatively correlated in Yorkshire (r=－0.31; P=0.09), which resulted in a significant negative correlation between these two variables in total animals (r=－0.35; P<0.01). Litter weight at weaning was not different between the two breeds or lines. Relationships between the litter weight and IGF concentration were not consistent across the breed ${\times}$ physiological stage combinations. Results suggest that d-90 Px IGF concentrations may be indicative of the litter size at impending farrowing.