RESPONSE TO DIETARY LYSINE SUPPLY DURING THE FINISHING PERIOD IN PIGS

An experiment involving 110 crossbred pigs (Pietrain x Large White) wa s conducted in order to evaluate the requirement for digestible lysine during the finishing period. Two periods were considered: 50 to 80 kg live weight and 80 to 110 kg live weight, with 50 pigs (25 castrated males and 25 females) in each of them. Ten additional pigs were slaugh tered and dissected at 50 kg live weight in order to estimate the init ial body composition of experimental animals. Five increasing levels o f lysine supply were tested for each period and gender. From 50 to 80 kg, average daily gain (ADG) increased linearly with lysine supply whe reas a linear-plateau response was measured from 80 to 110 kg, up to a maximum response of 930 g/d for a supply of 17.2 g digestible lysine per day. For a same daily supply of lysine, ADG and feed conversion ra tio (FCR) were 50 g/d and 0.5 kg/kg higher during the second than duri ng the first period, respectively. ADG increased by 37.9 g/d, FCR decr eased by 0.16 kg/kg and average daily muscle gain increased by 29 g pe r g of supplementary digestible lysine, For the genotype involved and the feeding level achieved in our experiment, it was concluded that th e requirement for digestible lysine decreased from about 0.80 g/MJ net energy at 50 kg to 0.63 g/MJ at 100 kg live weight. The marginal effi ciency of digestible lysine was around 65-70%. This value can be used for a factorial estimation of the requirement, based on daily protein deposition. More empirical predictive equations, based on ADG or muscl e gain, are also proposed.