Zusammenhang zwischen Bestands-, Gruppengröße und Indikatoren des Tierwohls in der konventionellen Schweinemast

Animal welfare became a significant issue in the society throughout the past decades. Many consumers tend to combine modern agricultural livestock farming primarily with a high number of animals on a confined space and consequently shortcomings when it comes to animal welfare. The term “intensive livestock farming” became a synonym for less animal-friendly husbandry and is discussed in the media under a rather negative light. In addition to the herd size, it is the size of the group that stands particularly under pressure. At the same time, the knowledge about the causal relationships between animal welfare and conventional livestock farming or the size of a herd or group is low, on a theoretical level as well as on the empirical one. Moreover, studies based on available literature do only include partial aspects of animal welfare and only certain animal species in their analyses. The current debate also focusses on fattening pig farms but only a few scientific studies cover the influence of herd- and group sizes on animal welfare. Therefore, the present study should derive a reliable statement about the connection of animal welfare indicators and the herd- and group size. The herd size was defined as the total number of animals of one field of usage at one location. The group size describes the number of pigs per pen at constant space supply per animal. Furthermore, animal welfare in conventional fattening pig farms need to be considered. This may lead to a general objectification throughout discussions in the society. Overall, 60 pig fattening farms were evaluated with the support of the Welfare Quality® Protocol for pigs. In due consideration of the development of farms in the German pig production and in accordance with the classification of pig farms by the German Federal Pollution Protection Act (2013), the assessed farms were categorized in the three farms size categories (20 farms/category): small = 30 pigs/pen, n = 136. The average pen size capacity covers 0.83 m2 per pig (range 0.31 to 2.5 m2per pig). The Welfare Quality® Protocol is an animal orientated indicator system that serves the comprehensive evaluation of animal welfare on livestock on the farm level. It includes four different steps that form out of the original 34 indicators, in a hierarchical aggregation process 12 criteria, 4 principles and finally one single overall assessment. The farms were classified on this fundament as “excellent”, “enhanced”, “acceptable” or “not classified”. The tree herd size-categories as well as group size- categories were compared to each other with reference to the averages in animal welfare evaluation from the protocol. The farm served as random effect. Almost 80% of the evaluated farms were classified as “enhanced”, all others as “acceptable”. Generally speaking, the overall welfare level of the evaluated farms hast to be considered as low. The herd size had no significant effect on the characteristics of the overall assessment. Principle- and criteria level could not prove significant differences between the herd size categories. The principle „ good feeding“ reached by far the highest score, even though the appropriate criteria “absence of thirst”, due to partly deficiencies in water supply, did not reach the highest achievable points. The criteria “comfort around resting” of the principle “good housing” was assessed with the help of the indicators manure on the body and bursitis. On average, 34.7% of the pigs on 60 farms, independent of the herd size, were affected with moderate bursitis. Thereby bursitis was the most common measure on the farms. The prevalence of manure on the pigs increased according the herd size (P < 0.05): the proportion of moderate soiled animals came up to 10.7% at smaller farms, in the middle 14.7% and in larger farms 20.6%. Moreover, the feeding system can be discussed as a potential factor of influence. The criteria “ease of movement” reached a score of 72 out of 100 possible points in average. Considering the German Farm Animal Welfare Regulations (2006), 40% of the pens were overcrowded. Among all principles, “good health” was scored worst with an average of 29.1 of 100 points. The associated criteria “absence of injuries” included among others the indicator wounds on the body. With an average of 11% wounded pigs on all 60 farms, the proportion is comparable high. The results of the slaughterhouse belong to the criteria “absence of diseases”. The incidence of pneumonia was in tendency lower in small herds (4.2%) than in medium (11.6%) and large herds (10.7%). Tail-docking and castration of the piglets no anaesthetic was used. Thus the criteria “absence of pain” was scored worse. The principle “appropriate behaviour” reached also a low score with 30 out of 100 points. This was mainly due to deficits for exploratory behaviour (criteria “expression of other behaviours”) and the worse evaluation of the emotional state of the animals. Intensive systems are often criticised with respect to species-specific behaviour. The results confirm that the herd size is not adequate as an indicator for insufficient well-being. A high number of pigs per farm are not correlated to a worse assessment of animal welfare. Regarding the relationship between the group size-categories and selected indicators of the Welfare Quality® Protocol, it was determined, that the group size has a significant effect on the indicator soiled pigs (P < 0.05). In the largest group size-category (15.8%) more pigs were significantly soiled as in the smallest group size-category (10.4%). The prevalence of moderate wounded pigs also increased significantly with a growing group size. In the largest group size-category (16.3%) the proportion was significantly higher than in the middle (11.3%) and in the smallest group size-category (8.5%). The indicator manure on the body as well as the indicator wounded pigs represent important indicators concerning animal-friendly husbandry systems. The prevalence of bursitis was not affected by the group size (P < 0.05). On the contrary, in large group sizes a better human-animal relationship was more often observed. In conclusion, none of the evaluated group sizes with respect to the indicators of the Welfare Quality® Protocol proved to be superior to others. It is more appropriate that the importance of the group size, as well as the herd size, with regard to animal welfare seems to be overestimated. At the same time, the overall situation has to be considered as unsatisfying, based on the detected prevalence’s of technopathies. The discussion about animal protection and animal welfare has to be continued. Other factors like the management or husbandry system should be taken into the focus of further studies to improve sustainable animal welfare on farms.