HIGH LEVELS OF ASCORBIC ACID IN LAYER DIETS UN- DER HOT CLIMATE

An experiment using Gimmizah sp. hens was conducted to study the effect of high levels of Ascorbic Acid (AA) on layer productive per‌formance and egg traits under hot climate. Four experimental diets were involved in the experiment : Basal layer diet (B), B + 500, 1000 or 2000 ppm AA. The experiment used forty-eight hens (60 weeks of age) for three 4-week interval (June, July and August). Hens were fed on the ex‌perimental treatments in triplicate, four hens each. At the end of each interval, the productive performance and egg traits parameters were measured. The multi-layer structure of the egg shell was studied using electron-micrography. Results of the overall period (the average of the three intervals) showed significant effect of AA supplementation on the productive per‌formance. The level of 500 ppm increased egg number (EN), egg mass (EM) and feed efficiency (FE) 7.02, 10.87 and 10.10% relative to the basal (without supplementation), respectively. Further increase was ob‌tained at higher levels. The level of 1000 ppm gave 14.04, 13.94 and 30.60% further increase as compared to the level of 500 ppm, whereas, 2000 ppm of AA showed 12.70, 2.07, 15.70 and 1 5.89% additional in‌crease in EN, EW, EM and FE, respectively as compared to 1000 ppm lev‌el. As regard to egg traits, 500 and 1000 ppm AA increased signifi-cantly yolk weight (YW) %, whereas, no significant effect could be found at 2000 ppm in all egg traits parameters. However, the results of the fi‌rst interval (June) revealed significant increase in shell thickness at 2000 ppm. Electronmicrography confirmed also greater strength of the egg shell due to such treatment. The economic evaluation of AA supplementation demonstrated 3.11, 14.3 and 17.5% decrease in feed cost/kg eggs at 500, 1000 and 2000 ppm AA, respectively.