Ascites and venous carbon dioxide tensions in juvenile chickens of highly selected genotypes and native strains

Abstract

A previous study by this group demonstrated that a high carbon dioxide tension in venous blood (pvCO 2 ) of juvenile broiler chickens is a reliable predictor for ascites susceptibility. In a new experiment with five highly selected genetic stocks and two ascites resistant old breeds we studied levels and variability of pvCO 2 within each stock at an early age. Effects of different selection traits (principally growth rate) between fast growing sire lines and slower growing dam lines and a commercial hybrid on blood gas (pCO 2 , pO 2 ) tensions, pH and haematocrit in venous and arterial blood were examined at different ages and compared to values found in ascites resistant breeds. All birds were housed in floor pens in a climate controlled room and subjected to an ascites-predisposing cold environment. From each stock, 16 birds with the highest (high risk: HRc) and 16 birds with the lowest (low risk: LRc) pvCO 2 values were selected at 12 days of age. These birds were marked for future blood sampling to determine changes in haematological characteristics with age and to relate these values to ascites susceptibility. At day 14, eight non-selected birds from each stock were randomly chosen for dissection to determine initial pulmonary arterial pressure index (API) values. Subsequently, all birds were allotted to 8 floor pens (13 birds per pen including two HRc and two LRc birds) per stock. Production performances from 104 birds per stock were measured from 16 to 33 days of age (feed intake (FI); feed conversion ratio (FCR); body weight (BW) at day 33). Mortality was recorded during the complete experimental period. At 5 wk of age, all HRc and LRc birds were necropsied and API values were recorded, which was used to classify the severity of the ascites syndrome. A convincing effect of pvCO 2 values in juvenile chickens on API at 5 wk of age in modern lines confirmed results obtained in the previous study. At an early age, pvO 2 values were much less predictive for high pulmonary pressure induced ascites at wk 5 than pvCO 2 values. Hypercapnia combined with low blood pH values and followed by hypoxemia (inducing high haematocrit values) provoked a marked high incidence of ascites and high API values in modern breeds. Ascites and venous carbon dioxide tensions: C.W. Scheele et al.A total absence of ascitic symptoms within native breeds corresponded with unchanged low API values during ageing from 12 to 33 days of age and with lower pCO 2 values in venous and arterial blood compared to modern breeds at all ages. The pvCO 2 difference (mean values) between HRc and LRc groups were similar for all modern lines irrespective of age and showed no relationship to growth rate. API, as a reliable indicator for ascites susceptibility, of modern breed chickens correlated with pvCO 2 values, but not with growth rate. The high correlation between pvCO 2 in juvenile chickens and API values at 5 wk of age indicated that a strong genetic selection pressure on low pvCO 2 values at an early age will be an effective method to reduce dec...

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

“…Mild hypoxia was found to elicit an increase in heart rate [169,170], which suggests that the AS-S birds in that study experienced O2 shortage already at the time of hatch, even when kept under optimal conditions. A higher mean partial pressure of CO2 in broilers' venous blood (a marker for lung ventilation rate) on d 11 was found to be associated with increased ascites susceptibility [171,172]. Those results indicate that ASsusceptible birds suffer O2 shortage at an early age.…”

Ascites Syndrome in Broiler Chickens: A Review on the Aspect of Endogenous and Exogenous Factors Interactions

“…Insufficient thyroid hormone activity to regulate metabolism, related to genetic background, will therefore become especially apparent at low ambient temperature (Scheele et al, 1992). Recent results (Buys et al, 1999;Decuypere et al, 2000;Scheele et al, 1992Scheele et al, , 2005Luger et al, 2001;Hassanzadeh et al, 2010) confirmed those of the Scheele et al (1992) and indicated that hypothyroidism, observed in lines combining a favourable FCR and fast growth, plays an important part in the reduction of oxygen consumption that lead to anoxia, heart failure and ascites.…”

“…Although ascites is conventionally associated with the rapid growth rate of broilers, high metabolic rates and high oxygen requirements (Hassanzadeh, 1997;Hassanzadeh et al, 1997a, b, Julian, 1993, 2005Balog, 2003), recent data indicated that ascites is not always caused by an increased oxygen requirement of fast growth rate per se at low altitude, but by an impaired oxygen supply to sustain the fast growth rate Scheele et al, 2005;Malan et al, 2003;Hassanzadeh et al, 2010). mentioned that thyroid function is an important regulatory mechanism of the metabolic rate, it is plausible that early selection for feed conversion (FCR) could have resulted in functional of hypothyroidism, as ascites sensitive birds are believed to be limited in their thyroxin (T 4 ) production (Scheele et al, 1992;Scheele, 1996).…”

“…Ascites syndrome is no longer restricted to birds that are kept at high altitudes, as was initially reported by Cueva et al (1974). However, it is now found in flocks that are kept at sea level as well Hassanzadeh et al, 1997aHassanzadeh et al, , b, 2000Hassanzadeh et al, , 2001Hassanzadeh et al, , 2012Balog, 2003;Scheele et al, 2005;Al-Mesri and Hassanzadeh, 2010).…”

Effect of oxygen supplementation in a hatchery at high altitude and growth performance of broilers reared at low altitude

“…In the present study, during the growing period at low altitude, the highest blood glucose level was found in the HA-OX group at 7 and 21 days old and the lowest plasma T 3 and T 4 levels and highest PCV values were found in the LA-NOX group at 42 days old. However, some researchers have suggested that there is not always an association between ascites syndrome and the haematocrit values (Shlosberg et al, 1998;Hassanzadeh et al, 2000;Scheele et al, 2005). As reported by Zhang et al (2007), significant increase in the haematocrit and Hb values were obtained in the birds reared at high altitude compared with those birds reared at low altitude.…”