Comparison of halothane-sensitive and halothane-resistant litter-mate pigs for growth, carcass composition, hormonal status and energy balance

Abstract

In three experiments with a total of 116 Belgian Landrace pigs, the differences between halothane-sensitive (HS) and halothane-resistant (HR) litter-mates were investigated with respect to growth performance, carcass composition, serum level of insulin and thyroid hormones and energy balance. In ad libitum feeding conditions (Experiment 1), HR pigs ate 9% more than HS pigs, and had a higher growth rate but a fatter carcass. By diluting the ration for the HR pigs, with cellulose (Experiment 2), the differences disappeared, since the HR pigs did not compensate by a higher intake on this bulky ration. In Experiment 3, the pigs were hand-fed on two restricted scales (80 and 90% of the ad libitum feeding intake of the previous experiments) in order to obtain by regression an estimation of the maintenance requirements of HS and HR pigs. Total metabolizable energy (ME) intake and total energy retention (from empty body analyses) were measured. In the HS pigs, only 34% of the ME intake was retained compared to 38% for the HR pigs. The possibility cannot be excluded that this difference, besides the less efficient energetic conversion of the ME for production in the HS pigs, is partly due to a higher metabolic rate in these pigs at maintenance energy level. In the three experiments, no consistent differences were noted between HS and HR pigs with regard to serum levels of thyroid hormones, but there was a significantly higher response to serum insulin after a meal in the HR pigs than in the HS pigs.