مجله علوم و فنون دامی
سال:1396 | دوره:5 | شماره:1 |تعداد مقالات:8

This study was carried out in a commercial herd from 2008 to 2012 in order to determine the most prevalent reasons for culling Holstein cows and to assess the effects of risk factors. Overall, 519 (28.2%) cows were culled for involuntary (98.8%) and voluntary (1.2%) reasons. The involuntary causes of culling were diseases (38.7%), reproduction problems (36.0%), udder disorders (7.7%), lameness (3.7%) and death (12.7%). Mean age of cows at culling was 70.5±15.6 months and the time interval from last calving to culling averaged 263±196 days. Logistic binary regression was used to model the hazard of culling. The analysis of risk factors showed that parity, calving season, and age at first calving had significant effects on the hazard of culling (P<0.05 to P<0.001). Thus, cows at parity 3 and 4 or greater had a 116.5% and 253.8% risk of culling, respectively than cows at parity 1 (reference class) (P<0.001). Cows that calved from May to August and from September to December had a 19.7% and 45.5% risk of culling, respectively, higher than those that calved from January to April. The risk of culling increased with increasing age at first calving. Thus, cows having an age at first calving of 25-30 and 31-38 months had a 130.8% and 90.4% risk of culling, respectively, higher than cows having an age at first calving less or equal than 24 months. It was concluded that identifying reasons for culling can be helpful in determining management problems in dairy herds.

Data from 183 animals raised in 61 flocks were collected to investigate the morphological characteristics of the Northern Morocco goat. Nine zoometric measures and seven combined indices were obtained. Three zones were defined based on geo-climatic characteristics and environ-mental influences: Mediterranean, Atlantic and Dual. The morphological variables showed the absence of sexual dimorphism in the northern Morocco goat population. Measures were generally very similar (n.s. at p<0.05) for male and female, except shin girth was high in males compared with females. A few variables including height at withers, ear length, rump length, length led and ears index were significantly (p<0.05) influenced by geographical area. Mahalanobis distances and Canonical analyses showed a greater distance between the most geographical separated subpopulations (Atlantic and Dual) and animals from these areas were the most heterogeneous. The stepwise procedure showed that length led, ear length, rump length and shin girth were the most discriminate variables between areas. Results suggest that the goat population of north Morocco, exhibiting different morphological variables by location, maybe due to the environmental adaptation or the differences in origin and recent influences by introgression or crossbreeding.