EFFECTS OF CROSSBREEDING AND SEX ON ENERGY REQUIREMENTS AND UTILIZATION BY YOUNG PIGS

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Abstract
The influence of crossbreeding and sex on digestible (DE) and metabolizable (ME) energy values, fasting heat production (FHP), energy requirement for maintenance and growth, and on the efficiency of utilization of metabolizable energy in young weanling pigs, was investigated by employing a comparative slaughter technique. The pigs obtained by insemination of Yorkshire sows with pooled semen (equal number of sperms) from purebred Yorkshire and Hampshire boars, were identified for genotype by blood-group typing. A total of 37 pigs was used in this study, of which 9 pigs selected at random were killed to provide the initial body composition and energy status of pigs in the feeding experiment. The remaining 28 pigs (16 purebred: 8 male and 8 female; and 12 crossbred: 6 male and 6 female) were allotted at random to a feeding experiment of a randomized complete block design involving a 2 × 2 × 2 factorial arrangement (purebred vs. crossbred, male vs. female, and level of dietary energy input: 130 and 330 kcal ME/Wkg0.75 daily). One metabolism trial with each pig individually kept in a crate was conducted during the 4th week of the 40-day feeding period. The coefficients of DE and ME were 89.2 and 84.2%, respectively, and were not influenced by sex or genotype. An interaction was observed in the estimates of the fasting heat production and energy requirement for maintenance. Purebred Yorkshire males had a greater fasting heat production than Hampshire × Yorkshire males, whereas females of the two breeding groups had similar values. The apparent efficiency of utilization of ME was 76% and the net efficiency of utilization of ME available above maintenance was 66%. The energetic efficiency and the net energy value of the diet were similar for both breeding groups and sex. The mechanism of rapid gains due to crossbreeding was investigated.

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