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.

Methionine sources do not affect performance and carcass yield of broilers fed vegetable diets and aubmitted to cyclic heat stress

“…In vitro experiments have shown that HS influenced D-Met absorption as compared to L-Met absorption (Knight et al, 1994). This fact would be disadvantageous to DLM-fed birds in comparison to HMB-fed birds, when they enter into the thermoneutral period.…”

Effect of arginine:lysine and methionine source on amino acid digestibility and response to dietary electrolytes in chronically or acutely heat-stressed broilers

“…While differences in absorption, metabolism, organ distribution and/or clearance between HMB and DLM (Saunderson 1985(Saunderson , 1987Dibner 2003) may also play a role, changes in the efficacy of either source of Met to fulfill the birds' requirements for total sulfur amino acids during HS cannot be discounted. Dibner et al (1992) and Knight et al (1994) measured the absorption of DLM in vitro as affected by HS in broilers. These authors concluded that the intestinal uptake of the D isomer of methionine was negatively impaired during HS mainly due to a significant reduction in the energy-and Na-dependent pathway.…”

“…In a subsequent experiment, these authors observed even greater growth depression in heat-stressed birds fed diets supplemented with D-methionine vs. those with L-Met suggesting that the impaired absorption for D-methionine mediated the lower performance of broilers fed DLM under tropical environments. However, the effects of HS on the in vitro uptake of these Met sources found by Dibner et al (1992) and Knight et al (1994) correspond to situations of short exposures to high temperatures and these effects have not been evaluated in vivo or in birds subjected to prolonged HS ( > 2 wk).…”

“…Better performance in birds fed 2-hydroxy-4-(methylthio) butanoic acid (HMB) compared with those fed DL-methionine (DLM) has frequently been reported in such birds (Swick and Pierson, 1988;Balnave and Oliva 1991;Swick et al 1990;Knight et al 1994). More recently, found that the source of synthetic Met determined the response of hyperthermic birds to Arg:Lys.…”

“…Using in vitro studies, Knight et al (1994) showed that the energy-and sodium-dependent pathway for D-methionine is severely compromised under conditions of hyperthermia resulting in a lower total intestinal D-methionine uptake. The intestinal energy and sodium-dependent pathway for Lmethionine (L-Met) uptake was also negatively affected by HS, while the energy and sodium-independent pathways were augmented, resulting in a total Met uptake similar to that of birds at thermoneutral conditions.…”