Effects of low-protein diets on acute phase proteins and heat shock protein 70 responses, and growth performance in broiler chickens under heat stress condition

Abstract

A study with a 4 × 2 factorial arrangement was conducted to investigate the effects of 4 dietary protein levels and 2 environmental conditions on acute phase proteins (APP), brain heat shock protein (HSP) 70 density, and growth performance of broiler chickens. Day-old broiler chicks (Cobb 500) were fed isocaloric diets but with various levels of crude protein (CP), namely, (1) 21.0 and 19.0% CP in starter and finisher diets, respectively (control), (2) 19.5 and 17.5% CP in starter and finisher diets, respectively (Diet A), (3) 18.0 and 16.0% CP in starter and finisher diets, respectively (Diet B), and (4) 16.5 and 14.5% CP in starter and finisher diets, respectively (Diet C). Equal numbers of birds from each diet were subjected to either 23±1°C throughout or 33±1°C for 6 h per d from 22 to 35 d of age. From d 1 to 21, feed intake (FI) and weight gain (WG) decreased linearly (P = 0.021 and P = 0.009, respectively), as CP level was reduced. During the heat treatment period (d 22 to 35), there were significant (P = 0.04) diet × heat treatment interactions for FCR. Diet had no effect on FCR among the unheated birds, but the ratio increased linearly (P = 0.007) as dietary CP level decreased. Irrespective of ambient temperature, there was a significant linear decrease in FI (P = 0.032) and WG (P < 0.001) as dietary CP level decreased. Low-CP diets improved the survivability of heat-stressed broilers when compared to those fed control diets. Low-CP diets linearly decreased (P < 0.01) APP (ovotransferrin and alpha-acid glycoprotein) responses. Both APP and HSP 70 reactions were elevated following heat treatment. In conclusion, feeding broilers with low-CP diets adversely affect the growth performance of broilers under heat stress condition. However, low-CP diets were beneficial in improving the survivability. Because APP are involved in the restoration of homeostasis, the adverse effect of low-CP diet on the synthesis of these proteins could be of concern.

Effects of protease supplementation of low protein and/or energy diets on growth performance and blood parameters in broiler chickens under heat stress condition

“…However, feeding LPRE, LPREP, RPLE or RPLEP diet had no detrimental effects on the bird's performance under both normal and heat stress conditions. Zaman et al (2008) reported a beneficial effect of feeding low-CP at recommended ME diet under HS, outcomes which disagree with many other works when low-CP (Alleman and Leclercq 1997;Zulkifli et al 2018) or low-CP and low-ME diets (Attia and Hassan 2017) were fed to broilers under the same conditions. These inconsistencies could be associated with differences in the levels of dietary CP, supplemented AA and/or the severity of heat challenge involved.…”

“…The current study demonstrated that HS elevated CORT and APPs (CPN, OVT and AGP) in broilers. It is well documented that heat exposure can elevate CORT (Mahmoud et al 2004;Soleimani et al 2011;Najafi et al 2015), APPs (Najafi et al 2015;Zulkifli et al 2018) and HSP 70 expression (Mahmoud et al 2004;Najafi et al 2015;Zulkifli et al 2018) in broilers. In the present study, reducing dietary CP and ME did not affect CORT level.…”

“…Little information is available on the effect of low-CP diet on APPs. Recently, Zulkifli et al (2018) reported that AGP and OVT levels were reduced in broilers fed diets with more than 3% reduction in CP. On the contrary, the present findings suggest that diet had a negligible effect on APPs.…”

“…Heat-stressed birds are characterised by a number of behavioural, metabolic and physiological changes to maintain body homeostasis (Gonzalez-Esquerra and Leeson 2006;Mack et al 2013). Physiologically, HS may elevate the production of heat shock protein 70 (HSP70), serum levels of corticosterone (CORT) and certain acute phase proteins (APPs) such as alpha-1 acid glycoprotein (AGP), ovotransferrin (OVT) and ceruloplasmin (CPN) (Najafi et al 2015;Olubodun et al 2015;Zulkifli et al 2018). For birds under HS condition, dietary CP reduction was reported to be beneficial as protein metabolism was associated with higher heat increment than carbohydrate or lipid metabolisms (Musharaf and Latshaw 1999;Ojano-Dirain and Waldroup 2002).…”

“…However, reduction of CP and or ME beyond certain levels may exert a negative effect on feed intake (FI) and growth rate (Zaman et al 2008;Dairo et al 2010;Awad et al 2015Awad et al , 2017 broiler chickens may adapt to diet of low-CP or ME content by eating more feed in an attempt to meet their nutrient requirements (Payne 1967;Leeson et al 1996), reduction below a certain level may not be compensated (Attia et al 2011). Moreover, for birds under HS condition, feeding low-CP diets could be detrimental to their feed conversion ratio (FCR) (Zulkifli et al 2018). Therefore, optimising broilers performance under HS condition is one of the major challenges encountered by poultry producers and nutritionists (Sandercock et al 2001;de Souza et al 2016).…”