Identifying Early Indicators of Tail Biting in Pigs by Variable Selection Using Partial Least Squares Regression.

This study examined relevant variables for predicting the prevalence of pigs with a tail lesion in rearing (REA) and fattening (FAT). Tail lesions were recorded at two scoring days a week in six pens in both REA (10 batches, 840 scoring days) and FAT (5 batches, 624 scoring days). To select the variables that best explain the variation within the prevalence of pigs with a tail lesion, partial least squares regression models were used with the variable importance in projection (VIP) and regression coefficients (ß) as selection criteria. In REA, five factors were extracted explaining 60.6% of the dependent variable's variance, whereas in FAT five extracted factors explained 62.4% of the dependent variable's variance. According to VIP and ß, seven variables were selected in REA and six in FAT with the tail posture being the most important variable. In addition, skin lesions, treatment index in the suckling phase, water consumption (mean), activity time (mean; CV) and exhaust air rate (CV) were selected in REA. In FAT, additional musculoskeletal system issues, activity time (mean; CV) and exhaust air rate (mean; CV) were selected according to VIP and ß. The selected variables indicate which variables should be collected in the stable to e.g., predict tail biting.

Evaluation of a small volume oil-free in vitro production system for bovine embryos.

BACKGROUND: Embryos are usually produced in culture systems with an oil overlay, which conveys protection against the evaporation of water and microbial contamination. The oil can also release toxic substances and absorb essential components, such as hormones, which adversely affect the quality of the oocytes and the development of embryos in vitro. OBJECTIVE: The aim of this study was to validate an oil-free bovine in vitro production (IVP) system. METHOD: Cumulus-oocyte complexes collected from abattoir-derived ovaries were matured, fertilized and cultured employing a standard system. The quantity of medium in both groups (with and without an oil overlay) and throughout all stages of IVP was maintained at a volume of 100 µl. The oil group was covered with paraffin oil. The maturation stage of oocytes was assessed using fluorescence staining after 24 hr and developmental stages of embryos were evaluated on day 8. The expanded day 8 blastocysts were assessed by live-dead staining. RESULTS: Oocytes matured in the absence of an oil overlay had significantly higher maturation rates when compared against matured oocytes in medium with an oil overlay. Steroid concentration is higher in medium after maturation without oil cover. The developmental rate was significantly higher after culture without oil overlay. The total cell number and the live-dead ratio was not significantly different. The osmolality did not differ between both groups during maturation and slightly decreased during culture without oil. CONCLUSION: Based on the current study, bovine oil-free IVP systems can be suggested as an alternative to oil-covered medium.