Jiraporn Marayat, Somruthai Lertpimonpan, Choawit Rakangthong, Panwadee Sopannarath, Chaiyapoom Bunchasak, and Wiriya Loongyai

DOI: 10.14456/sjst-psu.2019.152

pp. 1211 - 1218

Abstract

We investigated the effects of low-protein diets supplemented with methionine on the growth performance of Betong
chickens (KU-Line) from 4 to 18 weeks. A total of 192 four-week-old male Betong chickens were divided into three groups:
high-protein diet group (high crude protein [CP]), low protein diet group (low CP), and low-protein diet group supplemented
with methionine (low CP+Met). We found no significant effect of protein levels on the body weight gain and average daily gain.
Betong chickens fed a low-CP diet showed the highest feed intake (P<0.01) and protein intake (P<0.05), while birds fed the low
CP+Met diet had the highest methionine intake (P<0.05). The addition of methionine to the low CP diet resulted in a significantly
improved feed conversion ratio compared to the low CP and the high CP diet groups (P<0.01). Moreover, the feed cost was
reduced in the low CP+Met diet compared to the high CP diet (P>0.05). At the end of the experiment, two birds per replicate
were randomly selected and slaughtered. The carcass weights were not significantly different between the treatments. The
abdominal fat yield decreased in the treatment with methionine supplementation (P<0.05) at 12 weeks. Breast muscle samples
were collected for total RNA extraction. The cDNA was amplified using primers specific for ANT and UCP gene expression and
analyzed using real-time PCR. At 12 weeks, mRNA ANT expression was significantly higher in the muscle of birds fed diets
supplemented with methionine. The highest UCP expression was obtained from the low CP diet group, which also resulted in the
worst feed conversion ratio at 18 weeks. Our results indicated that methionine supplementation in low CP diets improved growth
performance, reduced feed costs, and influenced the expression of ANT and UCP in the muscle.