Abstract
AbstractThree trials were conducted to determine the optimum dietary lysine concentration for maximum growth rate (ADG) or minimum food conversion ratio (FCR) of boars and gilts from 60 to 90 kg (in pairs) and 80 to 100 kg (in pairs or groups). Ninety pairs of pigs and six treatments (dietary lysine concentrations) were used in experiment 1 (60 to 90 kg), 144 pairs and eight treatments in experiment 2 (80 to 100 kg) and groups of 13 pigs (no.=42 groups) and six treatments in experiment 3 (80 to 100 kg). Experiments were arranged as randomized-block designs, blocked on the basis of sex and start weight. Isoenergetic diets (13·8 MJ digestible energy per kg) were based on barley, wheat, soya-bean meal, with added vitamins, minerals and amino acids. Dietary lysine concentrations were: 7·9, 8·8, 9·7, 10·7, 11·7 and 12·5 g/kg in experiment 1; 7·0, 7·9, 8·8, 9·7, 10·7, 11·7, 12·5 and 13·5 g/kg in experiment 2; and 7·0, 7·9, 8·8, 9·7, 10·7 and 11·7 g/kg in experiment 3. In experiment 1 (60 to 90 kg pairs), ADG increased (quadratic, P<0·01) and FCR improved (quadratic, P<0·001) with increased lysine concentration. Although boars grew faster (P<0·001) and were more efficient (P<0·001) than gilts, maximum ADG was predicted at 10·8 g lysine per kg and minimum FCR at 10·9 g lysine per kg for all pigs. In experiment 2 (80 to 100 kg pairs), a treatment×sex interaction for ADG (P<0·01) and FCR (P<0·05) indicated that boars grew faster and had better FCR than gilts at dietary lysine concentrations above 10·7 and 9·7 g/kg respectively, with no difference between the sexes below these lysine levels. Maximum ADG was predicted at 11·8 and 9·9 g lysine per kg and minimum FCR was predicted at 11·9 and 10·0 g lysine per kg for boars and gilts, respectively. In experiment 3 (80 to 100 kg groups) ADG increased (quadratic, P<0·01) and FCR improved (quadratic, P<0·001) as dietary lysine concentration increased. Boars had higher ADG (P<0·001) and better FCR (P<0·001) than gilts. Maximum ADG and minimum FCR were predicted at 9·3 and 9·6 g lysine per kg for all pigs. In conclusion, boars grew faster and more efficiently than gilts, with interactions in experiment 2 indicating a greater difference in performance at higher dietary lysine concentrations.
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