title: Effect of intermittent periods of high environmental temperature on broiler performance responses to sources of methionine activity.
abstract: The objective of these experiments was to study the effect of intermittent high temperature (IHT) on performance of broilers fed different sources of methionine activity. Two 20-d experiments were conducted in which individually caged 28-d-old cockerels were exposed to a 5-d period of constant high temperature (HT, 30 to 32 C) followed by an equal period of thermoneutral (TN) temperatures (22 C) with the 10-d temperature cycle repeated twice. Birds held at 22 C were TN controls. Grower diets contained 3,275 kcal/kg ME and 20% CP and were supplemented with either 2-hydroxy-4-(methylthio)butanoic acid (HMB, Alimet Feed Supplement) or DL-Met up to a maximum of .88 to .90% total sulfur amino acids (TSAA). In Experiment 1, gain:feed but not average daily gain was greater (P < .05) for HMB than DL-Met birds subjected to IHT (.451 vs .413, respectively), but no treatment differences were observed for TN birds. Results of Experiment 2 demonstrated a linear response to HMB and DL-Met dose in TN (P < .01); however, only HMB-supplemented birds responded similarly in IHT (P < .01). These results are consistent with lower availability of DL-Met as a result of IHT. In vitro experiments indicated that capacity for uptake of DL-Met into intestinal epithelial cells was reduced in heat-stressed birds. Uptake of D-Met was more severely affected than was L-Met. Consequently, a third performance experiment compared the ability of D-Met and L-Met to support growth under conditions of HT. The results indicated that the effect of HT on broiler performance was mediated through reduced utilization of D-Met.
authors.affiliation: Novus International, Inc., St. Charles, Missouri 63304.
authors.forename: C D
authors.initials: CD
authors.lastname: Knight
authors.forename: C W
authors.initials: CW
authors.lastname: Wuelling
authors.forename: C A
authors.initials: CA
authors.lastname: Atwell
authors.forename: J J
authors.initials: JJ
authors.lastname: Dibner
mesh_terms: D000818:Animals; D002645:Chickens / Q000502:physiology*; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D005527:Food, Fortified; D006358:Hot Temperature / Q000009:adverse effects*; D008297:Male; D008715:Methionine / Q000008:administration & dosage*; D015430:Weight Gain / Q000187:drug effects
chemical_list: D008715:Methionine