Laying performance, digestibility and plasma hormones in laying hens exposed to chronic heat stress as affected by betaine, vitamin C, and/or vitamin E supplementation

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Table 2 Effects of dietary betaine (Bet), vitamin C (Vit. C), vitamin E (Vit. E), and their combined supplementation on some productive performance of dual-purpose hens reared under heat stress condition

Parameters	Control (+)	Heat stress treatments								SEM	P value
Parameters	Control (+)	Control (−)	Control + Bet	Control + Vit. C	Control + Vit. E	Control + Bet + Vit. C	Control + Bet + Vit. E	Control + Vit. C + Vit. E	Control + Bet + Vit. C + Vit. E	SEM	P value
Initial body weight, g	1573	1572	1571	1573	1574	1572	1571	1582	1569	2.393	1.00
Body weight change	198^a	149^b	206^a	190^a	206^a	205^a	198^a	203^a	197^a	1.604	0.001
Survival rate	100^a	98.5^b	100^a	100^a	99.2^ab	100^b	100^b	100^b	100^b	0.395	0.097
Laying rate, %	68.0^a	60.5^f	65.5^bc	65.8^b	63.6^e	63.9^e	65.4^bc	64.8^cd	64.2^de	0.239	0.001
Egg weight, g	50.5	49.4	50.9	50.5	49.4	49.6	49.4	49.8	49.6	0.334	0.325
Egg mass, g/d/hen	34.3^a	29.9^d	33.3^b	33.2^b	31.4^c	31.7^c	32.3^c	32.3^c	31.9^c	0.256	0.001
Feed intake, g/d	135^a	127^h	133^b	131^de	130^ef	132^cd	129^fg	132^cd	129^fg	0.302	0.001
Feed conversion ratio	3.95^d	4.29^a	3.99^cd	3.94^d	4.16^b	4.16^b	4.00^cd	4.10^bc	4.07^bcd	0.095	0.001

Means with at least one common superscript in a row do not differ significantly (P > 0.05)