Abstract
In order to examine whether the correlation among the growth, meat production trais and halothane sensitivities will vary or not with feeding systems, phenotypic correlation among these traits of pigs were compared between the pigs reared under ad-libitum feeding and those under restricted feeding. Also, the variance on these traits was analyzed to investigate whether or not there are interactions between genotype and feeding conditions.
Ninety-four male Landrace piglets from the basic (23 litters) and the first (24 litters) generations of the closed herd in Miyagi Prefectural Livestock Experiment Station which were obtained by mating of 11 boars (of the basic and the first generations) with 2-6 sows were divided into two groups of the ad-libitum and the restricted feedings.
The analysis with the feeding methods and the boars used as the factors revealed that pigs reared under the ad-libitum feeding condition were superior in terms of mean daily weight gain, feed consumption and feed efficiency to those reared under the restricted feeding condition, but no significant difference was seen in backfat thickness and loin-eye area between the two feeding conditions. Nor was there any significant genotype feeding interaction noted in any of the traits. The restricted feeding group proved significantly closer correlation between the mean daily weight gain and the feed efficiency (r=-0.883) and between the mean daily weight gain and the feed consumption (r=-0.754) than the ad-libitum group (r=-0.452 and -0.426, respectively), whereas the correlation between the mean daily weight gain and the daily feed consumption was significantly closer in the ad-libitum feeding group (r=0.751) than in the restricted feeding group (r=0.504). Although the correlation between the mean daily weight gain and the backfat thickness was not significant, it was positive (r=0.074) under the ad-libitum feeding and negative (r=-0.149) under the restricted feeding.
In the first generation, the halothane positive pigs showed significantly less feed intake and better feed efficiency than the halothane negative pigs under the ad-libitum feeding, but these differences were not found under the restricted feeding condition. The above-mentioned results suggested that the effects of halogene sensitive genes on the traits were influenced by the difference in the feeding system. In the next generation, however, there were no differences in these traits between the halothane positive and the halothane negative pigs in either of the two feeding groups.
