Effects of housing conditions on the welfare of lactating ewes

Abstract

Space allocation and housing conditions are critical factors for health and welfare of housed animals and it is well known that sheep are less easily accustomed to confinement than other farmed animals. This study was undertaken to investigate changes in the behavioral, immune and production performances of lactating ewes when subjected to different housing conditions. A one-year trial (from May 2005 to May 2006) was performed with 45 Comisana ewes. At the beginning of the trial the ewes were divided into three groups of 15 each, which were separately penned in the same building and balanced in terms of age, body weights and time of lambing. The treatments were: i) high stock density (HD) with individual ewe having 1.5 m2, ii) low stock density (LD) with individual ewe having 3 m2, iii) low stock density with external paddock (LDP) with individual ewe having 3 m2 divided into 1.5 m2 inside the building and 1.5 m2 in the external paddock. The cell-mediated immune status of sheep was evaluated by means of skin-tests which were performed on all the animals at the beginning of the trial, and then during the dry period, the first phase of pregnancy, the transition period and the beginning of lactation. Chicken egg albumin (OVA) was injected subcutaneously in both shoulders of each ewe to assess the humoral immune response. Antibody titers to OVA were determined in blood samples collected immediately before the first antigen injection and then at 20, 40, 60 and 80 days of the study period by an ELISA performed in 96-well U-bottomed microtiter plates. Behavioral observations were recorded once monthly by two trained observers equipped with video cameras. Scan samples were taken every 15 min from 0830 to 1230 and from 1330 to 1730. After lambing and weaning of lambs, the ewes were machine milked twice daily and milk yield was recorded daily by means of graduated measuring cylinders. Milk samples, consisting of proportional volumes of morning and evening milk, were individually collected weekly in 200 ml sterile plastic containers after cleaning and disinfection of teats (70% ethyl alcohol) and discharging the first streams of foremilk. Samples were carried to our laboratory by means of transport tankers at 4 °C, and analyzed for their chemical composition. Data were processed by analysis of variance, using the GLM procedure of SAS. Cell mediated immune responses detected in LDP ewes were higher than LD responses (P < 0.001). Mean antibody concentration was higher in LDP ewes than in LD ewes (P < 0.05), and in LD than in HD ewes (P < 0.001). A higher number of LDP ewes was observed standing and drinking than LD ewes (P < 0.001 and P < 0.01, respectively). Higher proportions of LD than HD ewes were observed in ambulatory activity (P < 0.01). On the contrary, lower proportions of LD than HD were observed drinking (P < 0.01); a tendency in higher number of aggressive activities was recorded in HD than in LD ewes (P < 0.1). Milk yield was lower in HD than in LD ewes (P < 0.05); milk from HD animals displayed and Somatic Cell Count (SCC) than milk from LD ewes (P < 0.001 and P < 0.05, respectively). Milk from LDP ewes had higher protein and whey protein contents (P < 0.05), and contained more lactose and less SCC than milk from LD ewes (P<0.01 e P<0.05, respectively). Data from the present trial showed that a stocking density of 1.5 m2/animal negatively influenced ewe welfare and production performance.