Divergent Selection for Ascites Incidence in Chickens

Abstract

Chicken lines that were either resistant or susceptible to ascites syndrome were developed by using a hypobaric chamber to induce the disease. Birds were reared in a hypobaric chamber that simulated high altitude by operating under a partial vacuum, which thereby lowered the partial pressure of oxygen. Ascites mortality data from birds reared under hypobaric chamber conditions were used to select siblings to be used for breeding. The response to selection for the susceptible (SUS) and resistant (RES) lines of chickens was very rapid from the base population, which exhibited an incidence of ascites of 75.3%. Extremes in the incidence of ascites were observed in generation 8, with line SUS exhibited an average incidence of ascites of 95.1%, and in generation 9, with line RES exhibited an average incidence of ascites of 7.1%. The incidence of ascites in the relaxed line remained relatively stable and currently has a general incidence of ascites of 60%. The heritability estimates +/- SE for ascites were estimated to be 0.30 +/- 0.05 and 0.55 +/- 0.05 for lines SUS and RES, respectively. Changes in the incidence of ascites appeared to be associated with livability. By generation 10, selection for ascites in line RES increased livability by 11.5 d, whereas in line SUS, livability was decreased by 8 d. Although divergent selection for ascites resulted in a reduction in d 42 BW for both the SUS and RES lines, the SUS line was approximately 163 g heavier than the RES line. Negative genetic correlations between ascites and the right ventricle:total ventricle (RV:TV) ratio were observed in both the SUS and RES lines; however, no significant change in the RV:TV ratio was observed for birds reared under normal conditions in either line. The current data raise questions about the validity of using the RV:TV ratio as an indicator trait in a selection program designed to reduce the incidence of ascites. Overall, direct selection for resistance to ascites by using sire family performance appeared to be an effective means of reducing the incidence of ascites. However, simultaneous selection for BW should be applied to counterbalance the losses in correlated BW.

Ascites Syndrome in Broiler Chickens - A Physiological Syndrome Affected by Red Blood Cell

“…Most broilers that remained healthy under the high-challenge AICs exhibited the same early GR and BW as those that later developed AS. These results, and the relatively high incidence of AS in the slow-growing line, indicated that there is very little, if any, direct genetic association between AS and genetic differences in potential GR, which suggests that AS-resistant broilers can be selected for higher GR These results, supported by several previous studies [68,[70][71][72][73][74][75][76][77][78], suggest that there is no "true" genetic correlation between the potential GR of broilers and their propensity to develop AS. It seems that AS is not caused by the increased O2 requirement of a fast growth rate, but by an impairment of the O2 supply needed to sustain the fast growth rate.…”

“…That study demonstrated the feasibility of selection based on mortality of AS-susceptible individuals under a protocol of high-challenge AIC. Divergent selection for AS mortality was conducted by Anthony et al [78]: the AS was induced in a hypobaric chamber where oxygen content was reduced to the level equivalent to 2,900 m above sea level. After 10 generations of divergent sire-family selection, %AS increased to about 90% in the AS-susceptible line and decreased to about 20% in the ASresistant line, thus reaching a divergence of about 70% [78].…”

“…Divergent selection for AS mortality was conducted by Anthony et al [78]: the AS was induced in a hypobaric chamber where oxygen content was reduced to the level equivalent to 2,900 m above sea level. After 10 generations of divergent sire-family selection, %AS increased to about 90% in the AS-susceptible line and decreased to about 20% in the ASresistant line, thus reaching a divergence of about 70% [78]. Similarly successful divergent selection was applied by Druyan et al [70]: the 1st selection cycle was based on progeny testing for AS mortality under low-challenge AIC, and two further cycles of full-pedigree progeny testing were conducted under a high-challenge AIC protocol [70,72].…”

The Effects of Different Eggshell Temperatures Between Embryonic Day 10 and 18 on Broiler Performance and Susceptibility to Ascites

“…Ascites has become a major cause of mortality in modern broiler production worldwide (Wideman & French, 2000;Balog, 2003;Pakdel et al, 2005;Pavlidis et al, 2007;Arce-Menocal et al, 2009;Hassanzadeh et al, 2010). Many difficulties in broiler production, such as ascites, are related with cardiovascular development and function problems (Leksrisompong et al, 2007).…”

Hypoxic Pulmonary Arterial Hypertension in the Chicken Model

“…Pulmonary hypertension (PH) in modern genetic strains of chicken broilers is a world wide distributed entity, which has a recognized economical impact (Maxwell et al, 1997;Pavlidis et al, 2007). Also, the commercial chicken has been a model to study PH in man, because encountered pathological changes in that animal closely resemble the human condition.…”