Growth-hormone-releasing factor given to early-pregnant Genex-Meishan and Large White gilts: Effects on growth, carcass, meat quality and histochemical traits of the progeny

Abstract

The objective of this study was to determine the effects of growth hormone-releasing factor (GRF) given in early gestation on post-weaning performance, carcass and meat quality and histochemical properties of two pig genotypes. Large White (LW, n = 10) and Genex Meishan-derived dam line (GM, with 50% Meishan genes, n = 10) gilts were treated during gestation with either saline injections (control, n = 5 LW and 5 GM), or 6.6 µg kg-1 of a GRF analog (n = 5 LW and 5 GM), given thrice daily from days 18 to 33 of gestation. After birth, at 56 d of age, four piglets (two barrows and two gilts) each from 20 litters were selected, allotted into individual pens and grown to slaughter weight (108.2 ± 2.3 kg). Feed intake was measured daily and pigs were weighed weekly. Prenatal GRF treatment had a detrimental effect (P < 0.05) on daily gain in both genotypes, but did not affect carcass quality. Significant interactions between GRF, genotype and sex (P < 0.01) for colour traits of the longissimus (L) and semimembranosus (SM) muscles and between GRF and genotype (P < 0.01) for shear force of the L muscle were found. GM pigs had lower growth rate (P < 0.01), higher feed intake (P < 0.05), fatter and shorter carcass (P < 0.001) than LW. L and SM muscles from GM pigs were less exudative (P < 0.05) than LW. L muscle from LW had higher percentages of slow oxidative (SO) (P < 0.001) and fast oxidative glycolytic (FOG) (P < 0.01) fibres but lower percentage of fast glycolytic (FG) fibres (P < 0.001) than that of GM. The results suggest that GRF given in early lactation reduces post-weaning growth of pigs from either breed, but does not affect carcass quality. GM pigs have poorer carcass quality than LW. Key words: Gestating gilts, growth hormone releasing factor, growth, carcass characteristics, meat quality traits, muscle fibre, pig