Influence of dietary lysine on growth performance and tissue accretion rates of high-lean growth gilts fed from 80 to 160 lb

One-hundred eight high-lean growth gilts (75.5 lb initial weight) were used to determine the dietary lysine requirement to maximize growth performance and protein accretion from 80 to 160 lb. The experiment was designed as a randomized complete block, with initial weight serving as the blocking factor. Six dietary treatments were included, ranging from .54 to 1.04% digestible lysine (.69 to 1.25% total dietary lysine). Pigs were housed in pens of three, with six replicate pens/treatment. Pig weights and feed disappearance were collected weekly to calculate average daily gain (ADG), average daily feed intake ADFI, and feed efficiency (F/G). Initially, six pigs were slaughtered to determine baseline carcass composition. When the mean weight for pigs in a pen reached 120 and 160 lb, one pig per pen was randomly selected and slaughtered for carcass analyses. The right side of each carcass was ground twice and sampled to determine carcass composition and lean tissue (crude protein) accretion rate. Average daily gains were greater for gilts fed increased dietary lysine from 80 to 120 lb, from 120 to 160 lb, and from 80 to 160 lb. Average daily feed intakes from 80 to 120 and from 120 to 160 lb were not influenced by dietary lysine. However, ADFI for the entire experiment tended to decrease as digestible lysine increased. Increased dietary lysine resulted in improved F/G from 80 to 120 lb and from 120 to 160 and 80 to 160 lb. Gilts fed increased digestible lysine had greater CP accretion from 80 to 120 lb, 120 to 160 lb, and 80 to 160 lb . Based on the feed intake observed in this study, the highlean growth gilt requires at least 18 to 19 and 22 g/d lysine intakes from 80 to 120 lb and from 120 to 160 lb, respectively, to maximize ADG, F/G, and lean accretion.