Modeling the Response to Paylean and Dietary Lysine Requirements

Purdue University 2001 Swine Research Report. Pork producers have the goal to efficiently produce lean, quality pork to compete with alternative animal products. The implementation of lean value carcass pricing systems has led to the selection of pigs with increased lean growth rates, increased carcass lean percentages and improved lean feed conversion. Health, nutrition, and facility management strategies have been implemented to increase commercially achievable lean growth rates. Paylean is a feed additive that further increases the rate and efficiency of muscle tissue growth. Paylean contains ractopamine hydrochloride, a small molecule that increases muscle protein growth and improves feed efficiency. Paylean has been approved to be fed at levels of 4.5 to 18 grams per ton (5 to 20 ppm) from 150 to 240 lbs live weight (last 90 lbs of live weight gain prior to slaughter). Because of increased muscle growth and protein accretion, pigs fed Paylean have increased dietary essential amino acid requirements. The objective of this research was to utilize recent Paylean research and develop a model of dietary lysine requirements for Paylean-fed pigs. The majority of past research trials evaluated the use of ractopamine at 4.5 to 18 gram/ton levels in 16% crude protein diets for the last 90 lbs of live weight gain before marketing. The lean growth response to ractopamine is not constant over the entire 90 lb gain feeding period. Research has been recently conducted with high lean gain terminal cross pigs fed high lysine diets. These trials indicate that the response to Paylean is immediate and substantial the first week of Paylean feeding and then decreases.