The response of entire male and female pigs from 20 to 100-kg liveweight to dietary available lysine

Abstract

Two experiments were conducted to determine the responses of entire male and female pigs of the Australian Pig Improvement Co. genotype to dietary lysine. In Experiment 1, a total of 350 [Large White × (Landrace × Duroc)] entire male and female pigs weighing 22.3 ± 0.16 kg (mean ± s.e.m.) were used in a 2 by 5 factorial design with the main treatments being sex (entire males and females) and five levels of standardised ileal digestible (SID) lysine to digestible energy ratio (0.6, 0.7, 0.8, 0.9 and 1.0 g SID lysine/MJ DE). In Experiment 2, a total of 420 [Large White × (Landrace × Duroc)] entire male and female pigs weighing 49.6 ± 0.34 kg (mean ± s.e.m.) were used in a 2 by 5 factorial design with the main treatments being sex (entire males and females) and five levels of SID lysine to MJ DE ratio (0.4, 0.5, 0.6, 0.7 and 0.8 g). From 20 to 50 kg liveweight (LW), entire males had a similar average daily gain (ADG), lower feed intake (FI, P < 0.001) and better feed to gain ratio (F : G, P < 0.001) compared with females. From 50 to 100 kg LW, entire males had a higher ADG (P < 0.001), similar FI and improved F : G ratio (P < 0.001) compared with females. Data were subjected to the quadratic response model to determine optimum SID lysine requirement for maximum ADG and minimum F : G for the weight ranges 20–35, 35–50, 50–65, 65–80, and 80 to 95 kg LW. For male pigs, maximum ADG was achieved at SID lysine levels of 1.00, 0.87, 0.72, 0.67 and 0.63 g/MJ DE, respectively. Minimum F : G was achieved at SID lysine levels of 1.00, 0.87, 0.80, 0.69 and 0.63 g/MJ DE for the respective weight ranges. For female pigs, maximum ADG was achieved at SID lysine levels of 0.90, 0.84, 0.67, 0.63 and 0.58 g/MJ DE. Minimum F : G for females was achieved at SID lysine levels of 0.86, 0.85, 0.64, 0.66 and 0.40 g/MJ DE for the respective weight ranges. The results suggest that this Australian genotype requires greater dietary SID lysine in the growing and finishing phase than the levels currently used by the Australian industry.