Effect of Temperature-Humidity Index (THI) and Increased Heat Load on Rectal Temperature and Performance of Layer Hens Treated with Ascorbic and Folic Acids

Abstract

This experiment was conducted to evaluate the effect of ascorbic acid and folic acid on the management of heat load in a hot humid environment. Specifically, the investigation was to determine the interactional effect of temperature-humidity-index (THI) and increased heat load on the rectal temperature and performance of layer hens using ascorbic and folic acids as ameliorative agents. A total of 72 laying hens at 31 weeks of age were randomly divided into four (4) treatment groups of 18 birds per group and indicated as T1, T2, T3 and T4. All the treatment groups were subjected to 3 hours of additional heat generated with a kerosene stove for 4-consecutive days of each week for 12 weeks. This additional heat was sufficient to induce intermittent panting and postural changes such as holding the wings out from the sides of the body. Diets for birds on T2, T3 and T4 were a layer’s ration containing crude protein 16.5%, min. fat 5%, and maximum fiber 6%, max. calcium 3.50%, min. available phosphorus 0.41% and energy 2500kcal/kg supplemented with 250mg of ascorbic acid, 250mg of ascorbic acid+1mg of folic acid and 300mg ascorbic acid+1mg of folic acid respectively per Kg of feed. T1 served as the control group without supplementation. Records on THI, rectal temperature, daily egg production, daily feed intake, daily water consumption and body weight gain were examined. The results obtained showed that the control group recorded the highest significant (P<0.05) value of rectal temperature between treatment groups. The daily feed intake did not differ significantly (P>0.05) between treatments. The water consumption differed significantly (P<0.05) with the T1 consuming the highest volume of water per day. It was also observed that the Temperature-Humidity Index (THI) increased from 72.99 (week 2) to 73.14 (week 12). These results suggest that combined supplementation of layer’s diet with ascorbic acid (at 300mg/kg feed) and folic acid (at 1mg/kg feed) could be a nutritional management strategy in minimizing the negative impact of increased heat load coupled with very high relative humidity on rectal temperature and performance and hence is recommended for use in laying hens during the hot periods of the year.