The Lysine Requirement of the Growing Boar versus Barrow

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Abstract
Five experiments were conducted to determine if boars and barrows differ in the level of dietary lysine required to maximize growth rate, efficiency of feed utilization, carcass leanness and N retention. In Exp. 1, 48 boars and 48 barrows were fed fortified corn-soybean meal diets calculated to contain 14 (grower) and 12% protein (finisher) and supplemented with 0, .15 or .30% lysine from 27 to 105 kg body weight. The basal diets analyzed .60 and .47% lysine, respectively. Linear improvements in feed/gain (P<.01),backfat thickness (P<.10), longissimus muscle area (P<.01), and ham-loin (P<.05) and lean cuts percentage (P<.1) were observed in boars as dietary lysine increased. In barrows, however, growth rate, feed:gain ratio and carcass characteristics (except longissimus muscle area) were not significantly affected by dietary lysine level. In Exp. 2, 18 boars and 18 barrows initially averaging 64 kg body weight were fed a 12% protein diet (.47% lysine) supplemented with 0, .15 or .30% lysine. Linear (P<.05) increases in N retention occurred in boars, but not barrows, as dietary lysine was increased. In Exp. 3 and 4, 140 boars (34 to 103 kg) were fed a 14-12% protein sequence (analyzed .61 and .48% lysine) supplemented with 0, .1, .2, .3 or .4% lysine. In Exp. 5, 60 boars (23 to 103 kg) were fed a 16- 14% protein sequence (analyzed .83 and .68% lysine) supplemented with 0, .075, .15 or .225% lysine. Rate and efficiency of gain and carcass characteristics tended to maximize when boars were fed approximately .86% lysine from 25 to 55 kg body weight and approximately .74% lysine from 55 to 105 kg body weight. The results indicate that developing boars require from .15 to .25% more dietary lysine than barrows of similar weight. Copyright © 1984. American Society of Animal Science . Copyright 1984 by American Society of Animal Science.