Özkan, S., Faculty of Agriculture, Department of Animal Science, Ege University, Izmir 35100, Turkey
Takma, Ç., Faculty of Agriculture, Department of Animal Science, Ege University, Izmir 35100, Turkey
Yahav, S., Agricultural Research Organization, The Volcani Center, Institute of Animal Science, PO Box 6, Bet Dagan 50250, Israel
Söǧüt, B., Faculty of Agriculture, Department of Animal Science, Yüzüncü Yil University, Van 65080, Turkey
Türkmut, L., Faculty of Agriculture, Department of Animal Science, Ege University, Izmir 35100, Turkey
Erturun, H., Veterinary Research Institute, Izmir 35100, Turkey
Cahaner, A., Faculty of Agriculture, Food and Environment, Hebrew University, Rehovot 76100, Israel

The development of ascites was investigated in broilers at low versus high altitudes, cold versus normal ambient temperatures (AT), and 3 feeding regimens. One-day-old chicks obtained at sea level were reared at high altitude (highA; 1,720 m; n = 576) with 2 AT treatments, low AT from 3 wk onward at highA (highA/cold) and normal AT from 3 wk onward at highA (highA/norm), or at sea level (normal AT from 3 wk onward at low altitude, lowA/norm; n = 540). Under highA/cold, AT ranged between 16 to 17°C in the fourth week, 17 to 19°C in the fifth week, and 19 to 21°C thereafter. Under highA/norm and lowA/ norm, AT was 24°C in the fourth week and ranged between 22 to 24°C thereafter. Broilers in each condition were divided into 3 groups: feed restriction (FR) from 7 to 14 d, FR from 7 to 21 d, and ad libitum (AL). Ascites mortality and related parameters were recorded. Low mortality (0.4%) occurred under lowA/norm conditions. Under highA/norm, mortality was lower in females (8.6%) than in males (13.8%) and was not affected by the feeding regimen. The highA/cold treatment resulted in higher mortality but only in males; it was 44.2% among highA/cold AL-fed males and only about 26% under the FR regimens, suggesting that FR helped some males to better acclimatize to the highA/ cold environment and avoid ascites. However, mortality was only 13.3% in AL-fed males at highA/norm and FR did not further reduce the incidence of ascites under these conditions. Thus, avoiding low AT in the poultry house by slight heating was more effective than FR in reducing ascites mortality at highA. Compared with FR from 7 to 14 d, FR from 7 to 21 d did not further reduce mortality and reduced growth. At 47 d, the majority of surviving broilers at highA had high levels of hematocrit and right ventricle:total ventricle weight ratio (>0.29), but they were healthy and reached approximately the same BW as their counterparts at low altitude. This finding may suggest that in broilers reared at highA from day of hatch, the elevation in hematocrit and in right ventricle:total ventricle weight ratio happens gradually and therefore is not necessarily indicative of ascites development. © 2010 Poultry Science Association Inc.