title: Performance and carcass composition of large white toms as affected by dietary crude protein and threonine supplements.
abstract: This experiment evaluates the effect of decreasing dietary CP, in addition to the effects of dietary supplements of L-Thr to low CP diets, in Large White Nicholas toms from 0 to 18 wk of age. Toms were fed dietary treatments consisting of four levels of dietary CP as a percentage of NRC (1994) recommendations (100, 92, 84, and 76% of NRC recommendations). Additional treatments consisted of supplements of L-Thr (0.1 and 0.2% of diet) added to the 92 and 84% NRC CP treatments. All eight dietary treatments were formulated to meet a minimum of 105% of NRC (1994) recommendations for Met, TSAA, Lys, Thr, and Trp. Body weight, feed conversion, mortality, and carcass composition responses were measured. Decreasing CP to 84% of NRC resulted in 18-wk BW lower than that (P < or = 0.001) of toms fed diets containing 100 or 92% of NRC CP; however, toms fed 84% of NRC CP diet supplemented with 0.1% L-Thr had 18-wk BW equal to (P < or = 0.001) that of the 100 and 92% NRC CP treatments. Toms fed diets containing 76% of NRC CP had depressed BW and feed:gain in comparison to all other treatments. No adverse effects in cumulative feed:gain (0 to 18 wk) were noted by decreasing CP from 100 to 84% of the NRC recommendations. Mortality did not differ among treatments. Treatments had no effect on carcass fat expressed as a percentage of hot carcass weight. Breast meat yield (deboned Pectoralis major and Pectoralis minor) was highest (P < or = 0.001) in toms fed the 100 and 92% NRC CP treatments. The 84 and 76% NRC CP treatments resulted in decreased breast meat yield regardless of L-Thr supplements. These results indicate that diets containing Met, TSAA, Lys, Thr, and Trp at a minimum of 105% NRC recommendations may support favorable breast meat yield when CP is decreased to 92% of the NRC (1994) recommendation. If growth and feed conversion are the desirable traits, rather than breast meat yield, CP levels below 92% of the NRC (1994) recommendation may support favorable responses.
authors.affiliation: Nutri-Quest, Inc., Chesterfield, Missouri 63017, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Kidd
authors.forename: B J
authors.initials: BJ
authors.lastname: Kerr
authors.forename: J A
authors.initials: JA
authors.lastname: England
authors.forename: P W
authors.initials: PW
authors.lastname: Waldroup
mesh_terms: D000818:Animals; D001823:Body Composition / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000494:pharmacology*; D019587:Dietary Supplements; D008239:Lysine / Q000494:pharmacology; D008297:Male; D008715:Methionine / Q000494:pharmacology; D011897:Random Allocation; D013912:Threonine / Q000494:pharmacology*; D014364:Tryptophan / Q000494:pharmacology; D014422:Turkeys / Q000254:growth & development* / Q000502:physiology*; D015430:Weight Gain / Q000502:physiology
chemical_list: D004044:Dietary Proteins; D013912:Threonine; D014364:Tryptophan; D008715:Methionine; D008239:Lysine