Influence of deep-litter bedding materials on environmental and welfare-related factors in boar studs

Abstract

In recent years, it has become increasingly difficult for artificial insemination (AI) centers to procure high-quality bedding materials. The aim of this study was to investigate influences of bedding materials on selected environmental and welfare-related aspects in breeding boars. Including seasonal changes, two trial runs were conducted in winter (T1) and summer (T2) to compare five deep-litter bedding materials (wood shavings (WS), hemp straw (HS), linen straw (LS), spelt husks (SH), and regional wood shavings (RWS)). The cleanliness of the boar pens was visually assessed at the end of T1 and T2 using a 4-point scale (1 = >75%, 2 = 75-51%, 3 = 50-25%, and 4 = <25% clean surface). Simultaneously, a body position score for each boar was assessed (1 = lying on flank, 2 = lying on belly, 3 = sitting, and 4 = standing). Temperatures of bedding at 5cm and 15cm depth were determined using a thermometric probe at week 6 and 16 after initial bedding replacement. Ambient temperature and relative humidity were measured at the same time. Simultaneously, fecal samples were collected and analyzed for oocysts in T1. To include flies as a health hazard and nuisance, sticky traps were evaluated in T2. Generalized linear mixed models and a two-way ANOVA were calculated for the statistical evaluation of observations. Cleanliness evaluation showed differences among bedding materials in T1 (P = 0.004) but not in T2 (P > 0.05). There were no differences in the body position score among the materials. WS and RWS were generally cooler at the start of T1 and T2. The greatest difference of 7°C in means was detected between RWS and SH at the start of T2 and 15cm depth (P ≤ 0.001). Oocyst counts revealed no difference among bedding materials in T1. In T2, fly numbers differed for time of bedding period and for the interaction term between time of bedding period and material (P ≤ 0.05). In conclusion, the results demonstrate clear differences between materials in terms of temperature, cleanliness of pens (T1), and partially fly burden (T2). Considering heat is a great stressor for most animals, we favor wooden materials as deep-litter bedding for AI boars compared to others due to lower heat development during the bedding period. Moreover, we recommend avoiding replacement of deep-litter bedding during hot summer months in AI centers to reduce excessive heat development.