Ascites is a major cause of mortality and morbidity in modern broiler production. Reduction of early growth, followed subsequent compensatory gain, seems a practical and viable method to minimize losses caused by ascites An experiment was conducted to determine if the early feed restriction can reduce the incidence of ascites in broilers exposed to cool temperatures. Ross 308 cockerels (n=180) were assigned to 5 diet treatments and 2 temperature regimes, with 3 replicate pens of 6 birds per treatment and temperature. A standard grower diet was diluted by adding rice hulls at 0, 15, 30, 45 and 60 percent by weight from 7 to14 days of age. On days 21 through 42 the temperature was maintained at 20 to 25 °C (thermoneutral), or at 11 to 15 °C (cool). Broilers exposed to cool temperatures developed higher right ventricle to total ventricle ratios and right ventricle to body weight ratios, increased plasma triiodothyronine (T3) and thyroxine (T4) concentrations, and elevated blood values for hemoglobin concentration, mean cell volume and hematocrit (P<0.05), but did not develop clinical ascites. Diluting the feed with rice hulls on d 7 to d 14 resulted in proportional reductions in body weight on d 14 (P < 0.001) that tended to persist through d 28 (P = 0.005), after which compensatory growth eliminated all differences in body weight between diet treatment groups on d 35 (P = 0.099) and d 42 (P = 0.202). Exposure to cool temperatures increased key indices of ascites susceptibility, and these pre-ascitic changes were partially prevented by diluting the feed to reduce growth performance.
کلید واژگان :Ascites, broiler, cold temperature, feed dilution, rice hull
ارزش ریالی : 1200000 ریال
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