Große Liesner, Bernd Benedikt:
Comparative investigations on the performance and the appearance (incidence and manner) of primarily non-infectious health problems in male fattening turkeys of five different strains
In Germany heavy strains are predominantly used in the turkey production. Since its launch in 1982 the strain Big 6, developed by the breeding company BUT, is commonly used in Germany. During recent years other heavy turkey strains were also developed and launched in the European market. Up to now only very few comparative trials with heavy turkey strains were conducted under European husbandry and feeding conditions.
Increased performance and environmental conditions are thought to be associated with health disturbance in fattening turkeys. Many authors subsume these changes of health status – including changes of the musculoskeletal system, cardiovascular diseases and behavioral problems – under the term “husbandry and breeding related diseases”. These problems cause harm to animal welfare as well as to the profitability of turkey husbandry.
In fattening turkeys there are prevalent inflammatory changes of the foot pad called foot pad dermatitis.
The aim of this study was to compare toms of five heavy turkey strains in regard to their performance and livability as well as to the rate and distribution of the causes of loss. A matter of particular interest was whether the strains differ in the incidence and grade of changes of the foot pads.
The trial was conducted with tom turkeys of five different heavy strains (864 animals each) that were reared for 20 and 21 weeks under commercial husbandry and feeding conditions. During the trial, all animals that died or had to be culled were examined post mortem, with particular regard to the incidence and grade of changes of the musculoskeletal system. For the evaluation of changes related to foot pad dermatitis, animals that died or were culled or collected for other investigations as well as animals that were signed individually as indicators were examined during the trial. In addition, all animals were examined for changes of the foot pad at slaughter. Beside the study described here, investigations on the development of the skeleton system and on calcium
and phosphorus metabolism were conducted during the trial and will be published by GÖTTING (2007).
All strains showed good results concerning their performance. Birds were slaughtered with an average bodyweight of 20.1 kg and 21.3 kg with a corrected cumulative feed conversion rate of 2.51 kg/kg and 2.61 kg/kg at 141 and 148 days of age respectively. The hot carcass yield (74,6 % and 75,1 %) and the breast meat yield (27,5 % and 28,0%) increased in all strains from 141 to 148 days of age. The mortality rate accounted to 9.77 % at 20 weeks of age. There were no distinct differences between the turkey stains in terms of mortality and in the distribution of causes of loss. The most frequent causes of loss were changes of the locomotor system (3,08 % of the placed chicks), diseases of the cardiovascular system (1,40 %) and pecking and scratching injuries (1,12 %). Significant differences in the livability appeared only during the first week (0.694 % in strain A to 2.43
% in strain E). It was noticeable that strains which were relatively fast growing in the rearing period had a lower livability than strains with a posterior weight gain at the end of the fattening period.
The appearance of foot pad lesions increased in terms of incidence and degree of damage during the trial. At the end of the fattening period scarring healings were observed in some affected animals. At slaughter only 2.80 % of the animals showed no lesions. During the trial significant differences in the condition of foot pad changes were detected repeatedly between the strains. It seemed that also developing of the foot pad dermatitis and its healing varied between the strains.
Scratching injuries were observed especially at the back and the thighs of animals of which it can be assumed that they were affected in their locomotion ability. Pecking injuries appeared almost exclusively at the head and cervix of animals. Birds that showed an inflammatory affection of the viscera (pneumonia, aerosacculits, pericarditis, serositis and perihepatitis) were cumulatively affected by injurious pecking.
A concluding weighing of the investigated strains is not feasible because the rating of the strains differs according to the tested parameters and the age at slaughter. The ranking for some of the tested parameters is listed below (first position = most favorable value):
- positon 1st 2nd 3rd 4th 5th
- liveweight (at 141 days of age): B > E > D > C > A
- liveweigth (at 148 days of age): D = B > E > C > A
- cumulative feed conversion rate (at 141 days of age): C > B > A = D = E - cumulative feed conversion rate (at 148 days of age): A > E > C > B = D - breast meat yield (at 141 days of age): A > B > E > C > D - breast meat yield (at 148 days of age): A > C > D > B > E
- livability (at 141 days of age): C > B > D > A > E
- foot pad disease (at 104 days of age): C > A > E > B = D
- foot pad disease (at 141 days of age): E > A > B > C > D - foot pad disease (at 148 days of age): C > E > D > A > B It has to be considered that the people in different stages of the turkey production also have differing interests regarding the turkey strains. Livestock owners will favor a bird with high daily weight gain and low feed conversion rate, whereas a slaughter company is interested in a bird with high hot carcass and breast meat yield.
Furthermore, the appraisal of strains has to include health and animal welfare aspects, whereas weighing is not possible for these parameters as well.