Response of laying hens to vitamin C supplementation through drinking water under sub-tropical conditions

Vitamin C (L-ascorbic acid) was evaluated for its effects on production performance, and plasma ascorbic acid, blood glucose and serum cholesterol levels in heat-stressed laying hens. One hundred and fifty, 72-week-old single comb white Leghorn hens in their second laying year cycle were kept at high ambient environmental temperature (average of 34.5 degrees C; range 28-42 degrees C) throughout the experimental period of 12 weeks. Three levels of vitamin C, 0, 1,000, or 1,200 ppm, were supplemented through drinking water to the treatment groups A (control), B and C, respectively. Hen-housed egg production, efficiency for feed conversion, egg weight and egg mass were improved (P<0.01) in birds receiving vitamin C supplementation when compared to the control birds. Shell thickness was higher (P<0.01) in birds receiving 1,000 ppm vitamin C supplementation compared to those of other groups. However, feed intake, water consumption and rectal temperature of hens were not influenced (P>0.05) by vitamin C supplementation. The birds without vitamin C supplementation showed a higher mortality (P<0.05) among them. The birds receiving vitamin C supplementation had significantly (P<0.01) increased plasma ascorbic acid while decreased blood glucose and serum cholesterol levels when compared to the birds of control group.