Growth performance, duodenal morphology and the caecal microbial population in female broiler chickens fed glycine-fortified low protein diets under heat stress conditions

Abstract

1. This study was undertaken to examine the effect of feeding glycine (Gly)-fortified low protein (LP) diets on the growth performance, duodenal morphology and caecal microbial populations of broiler chickens raised under unheated, cyclic or constant heat stress environmental conditions. 2. From d 1 to 21 (starter phase), an equivalent number of birds were fed either a normal protein (NP) diet or a LP diet fortified with Gly. From d 22 to 42 (grower phase), an equivalent number of birds from each starter diet were distributed to one of the following dietary groups: (i) an NP diet during the starter and grower phases (NPNP), (ii) an NP diet during the starter phase and a LP diet during the grower phase (NPLP), (iii) an LP diet during the starter phase and an NP diet during the grower phase (LPNP) or (iv) LP diets during both phases (LPLP). 3. Commencing from d 22, an equivalent number of birds from each dietary group were exposed to (i) 23 ± 1°C throughout (unheated), (ii) 34 ± 1°C for 7 h each day from 10:00 to 17:00 (cyclic heat) or (iii) 34 ± 1°C throughout (constant heat). 4. Feeding the LP diet during the starter phase resulted in feed intake (FI), weight gain (WG), feed conversion ratios (FCR) and energy efficiency ratios (EER) similar to those for the NP diet. The birds fed the LP diet had a significantly higher protein efficiency ratio (PER) compared with the birds fed the NP diet. 5. During the grower phase, there were significant diet × temperature interactions for F, WG, FCR, PER, EER, villus height, crypt depth and caecal Clostridia. The birds fed the NPLP and LPLP diets had lower FI, WG and EER, higher FCR, shorter villus height and crypt depth and higher caecal Clostridia compared with the birds fed LPNP and NPNP diets under constant heat stress. However, feeding birds the NPLP and LPLP diets resulted in FI, WG, EER, FCR, morphology parameters and caecal Clostridia equivalent to the birds fed LPNP and NPNP diets, as well as improved PER, under unheated and cyclic heat stress conditions. 6. In conclusion, our results indicate that Gly-fortified LP diets can be fed to broilers under normal and acute heat stress environmental conditions without any adverse effects on performance. However, the use of such LP diets can be detrimental to broilers under chronic heat stress conditions.

Effects of heat stress on growth performance, selected physiological and immunological parameters, caecal microflora, and meat quality in two broiler strains

“…This brings about alterations in biochemical variables (such as glucose) aimed at maintaining homeostasis = 24); Temp, temperature. 1) The heat stressed birds were exposed to 34°C for 6 h daily. 1) The heat stressed birds were exposed to 34oC for 6 h daily.…”

“…1) The heat stressed birds were exposed to 34°C for 6 h daily. 1) The heat stressed birds were exposed to 34oC for 6 h daily. a,b Means within a row-subgroup with no common superscripts are significantly different at p < 0.05.…”

“…However, strain significantly (p<0.05) affected the shear force value as Ross 308 broilers showed higher meat shear force than Cobb Ig, immunoglobulin; SEM, standard error of the mean for main effects (n = 24); Temp, temperature. 1) The heat stressed birds were exposed to 34°C for 6 h daily.…”

“…The activities of com mensal intestinal bacterial populations, also has a notable impact on the physiological and pathological conditions of the host. The adverse effects of heat stress on the intestinal mucosa and microbiota of broiler chickens and pigs have been verified through several investigations [1,15,16].…”

“…However, heat stress remains a significant environmental challenge that can be financially costly for the poultry industry. The harmful consequences of heat stress stretch from a decreased body weight gain (BWG), feed intake (FI), and increased feed conversion ratio (FCR) of live birds [1], to substandard meat quality [2]. Furthermore, adverse effects on caecal microflora have been detected in heatstressed broilers [3].…”