Wider slot in pens with fully slatted rubber mat flooring for fattening bulls: Effects on animal hygiene, health and welfare

This study investigated health and welfare of 119 Swedish fattening bulls when allowing wider slots in fully slatted rubber mats pens. On arrival Light bulls (around 120 ± 28 kg at 4.7 ± 1.3 mo of age) were allotted to 6 pens with fully slatted rubber mats, of which 3 Control pens had 30 mm slot openings and 100 mm slat width and 3 Test pens had 35 mm slot openings and 90 mm slat width. Reaching >400 kg (Heavy bulls), Control bulls were moved to 3 larger pens having 35 mm slot openings and 100 mm slat width and Test bulls to 3 pens having 40 mm slot openings and 100 mm slat width. Pens hosted 5–7 bulls. Bulls stayed in the same group (Control/Test), and were observed until slaughter (around 600 kg for 20.5 ± 2.1 mo). Total drainage area was 14% for Control and 18% for Test floors. Bull body condition, hygiene, locomotion and leg lesions were assessed on eight days during the 18 months study. At slaughter, hind feet were measured, trimmed, and evaluated for claw disorders. Two pens/floor were filmed during two 14-h sessions to monitor animal activities, social interactions, and lying postures. Wider slots did not affect body condition or hygiene on farm, although 3 Control and 1 Test bulls were penalised at slaughter for poor hygiene. Light bulls were dirtier than Heavy bulls, especially on thigh/flank areas. Bulls became dirtier in winter. Percentage of bulls showing locomotor problems was generally low and not affected by wider slots (1.09 vs. 0.91% for Control and Test bulls, respectively). Test bulls showed a slight tendency to develop more swelling on hock and carpus (0.55 vs. 3.18% for Control and Test bulls, respectively). Rubber mats did not cause toe overgrowth (mean dorsal wall of outer claw = 87.5 mm) and Test bulls showed lower prevalence of asymmetric claws (38.5 vs. 13.3% for Control and Test bulls, respectively). Interdigital hyperplasia and white line fissure were detected only in Control bulls. Outcomes of this study suggested that the 4%-unit increase in drainage area of fully slatted rubber mat floors did not impair bull behaviour, since few atypical transitions and lying sequences were recorded, or even improve flooring and animal hygiene. However, some limitations of the research require further investigations to provide evidence supporting the widening of slot openings in fully slatted rubber mat floors for fattening bulls’ welfare purpose.