English abstract
ABSTRACT
A study was conducted to investigate the effects of season, housing type and ascorbic acid supplementation on performance, carcass and meat quality characteristics of commercial broiler chickens under Omani conditions. Two houses (closed and open-sided houses) and four levels of ascorbic acid (000, 100, 200 and 300-ppm) were used in the cool and hot season experiments whereas one house (open-sided house) and four levels of ascorbic acid (000, 100, 200 and 300-ppm) were used in the mild season experiment. Four-hundred
and thirty two day-old Cobb-500 broiler chickens were randomly and equally divided into open-sided house and closed house. Within each house, birds were randomly allocated into four treatments with six replicates each containing nine birds. In the mild season experiment, 216 birds were randomly allocated into four treatments with six replicates each containing nine birds. Daily minimum and maximum temperatures for outside and inside houses and relative humidity readings were recorded. Weekly rectal temperatures, rnortality rate, feed intake, weight gain and feed conversion ratio in broiler chickens were measured. At the end of the experimental period (42 days), two birds from each pen were
randomly selected and slaughtered to evaluate the effect of housing type and ascorbic acid supplementation on carcass and meat quality characteristics. There were large differences in the range of ambient temperatures between hot, cool and mild season experiments; (32-45°C), (22-28°C) and (25-35°C), respectively. Temperature inside the closed house was not affected by these seasonal changes because of the efficient cooling system. On the other hand, the open-sided house was much affected by the ambient temperature and relative humidity outside the house especially during hot season. This resulted in. appearance of heat stress classical signs in birds such as panting and wing lifting during the hot season.
Rectal temperatures in control birds in the open-sided house during hot season (40.3-42.5°C) were significantly (p<0.05) higher than those in cool season (40.1 41.5°C) and mild season (40.7-41.4°C). Control birds significantly (p<0.05) consumed 12.8 and 12.2% less feed in the hot season than their counterparts in the cool and the mild seasons, respectively. Similarly, body weight gain was 15.7 and 17.0% less in the hot season than in the cool and the mild season, respectively. Ascorbic acid supplementation improved broiler performance,
carcass and meat quality characteristics with the effect been more pronounced in the hot season. Feed intake was improved by 6.6, 28.7 and 3.6% with 300 ppm ascorbic acid supplementation in the cool, hot and mild seasons, respectively. Body weight gain was also improved by 7.0, 29.0 and 7.3% with 300-ppm ascorbic acid supplementation added in the cool, hot and mild seasons, respectively. On the other hand, mortality rate was reduced; carcass and meat quality characteristics were improved by supplementing ascorbic acid during hot season. This study indicated that supplementing ascorbic acid will be beneficial to small-scale farmers in the open-sided house type under Omani conditions during the hot season of the year.
