Behavioral, adrenal, immune, and productive responses of lactating ewes to regrouping and relocation.

Abstract

The experiment involved 40 mid-lactating Comisana ewes. The animals were housed in straw-bedded pens and assigned to a control group (n = 10) and two test groups of 15 subjects each. Control ewes were never moved from their pen and peers throughout the experiment period, whereas test animals were subjected to either regrouping (RG) or regrouping and relocation (RGRL) three times at weekly intervals (d 7, 14, and 21 of the trial). Three behavioral recordings were conducted after each social and pen exchange over a 6-h period (1000 to 1600). Animals from groups RG and RGRL were bled immediately before each regrouping and relocation and 15 and 60 min afterward. The phytohemagglutinin skin test was performed at d 9, 16, and 23. Milk yield was recorded when the ewes were mixed and moved, and before and after each mixing and moving procedure. Individual milk samples were analyzed for composition, renneting parameters, and bacteriological characteristics; samples with more than 10(6) somatic cells/mL were cultured for mastitis-related pathogens. Control ewes spent more time lying than groups RG (P < 0.001) and RGRL (P < 0.01) and less time in ambulatory activities than RGRL sheep (P < 0.05). Moved and remaining ewes showed a higher number of aggressive interactions than control subjects (P < 0.001 and P < 0.01, respectively). Control sheep showed the highest cell-mediated immune response compared with both moved and mixed ewes (P < 0.001 and P < 0.01, respectively). The RGRL ewes gave lower yields of milk than did the control ewes on the days after the first (P < 0.05) and the second (P < 0.01) change of pen and peers. The RGRL ewes also had a lower fat content (P < 0.05) than control ewes in the milk yielded on the day of the first regrouping and relocation and a lower milk protein content (P < 0.05) on the following day. The RG treatment resulted in the ewes yielding milk with a lower fat content (P < 0.01) on the day of each mixing procedure as compared with controls and in a decreased milk protein content on the days after the first (P < 0.05) and the second regrouping (P < 0.01). One case of subclinical mastitis was recorded in both the RG and RGRL groups, whereas no cases were detected in control group. These findings suggest that regrouping and relocation may cause increased aggression, altered immune responses, and short-term effects on the production performance of lactating ewes. These practices should be performed by attempting to minimize their impact on animal welfare.