Study of the Status and Causes of Culling In Dairy Cattle in Qazvin Province

One of the most important and complex management decisions in dairy farms that greatly affects the economy and profitability of the dairy herd is the issue of culling. Regarding the importance of the subject, this study aimed to investigate the culling status and causes of Holstein dairy cattle in Qazvin province. For this research, the culling data of 35 industrial dairy herds under the cover of Qazvin Farmerschr('39') Union were collected and analyzed during one year. Herds were categorized into five categories(treatments) of dairy cows including herds by capacity less than 100 (low), 100-200 (relatively low), 200-500 (average), 1000-500 (relatively high) and more than 1000 heads (high)., The culling data were analyzed in a completely randomized design in two main categories of forced and optional removal. The results showed that there was a significant difference in mean parity of the cows between the different treatments and mean parity decreased with increasing capacity of the studied cows. The mean parity of culling cows in the studied herds in Qazvin province was 3.92. There was no significant difference between different treatments in the percentage of fresh cows, primiparous cows as well as the percentage of productive cows (lactating and dry). Clinical mastitis accounted for 5.08% of total culling in dairy herds and there was no significant difference between treatments for this disease. BLV disease accounted for 1.25% of the total culling in the dairy herds studied and the difference between relatively high and high treatments were significant (P≤0.05). There were no significant differences between treatments for acidosis, abomasal displacement, ketosis / fatty liver, milk fever and bloat. The results of this study showed that in high capacity dairy herds (more than 500 heads), cows are culled earlier from the herd. The voluntary removal ratio in industrial dairy herds in Qazvin province was 27.67%. The most important factor for removal in these dairy farms was infertility and reproductive malformations with the ratio of 31.85%.