Investigation of the culling reasons of dairy cows in Tehran Province's dairy farms

Removal of large dairy cows required high cost of replacement heifers and in contrast with development of the herds. The economic life of dairy cattle in our country is low. Our project was planned to study and investigate the reasons for culling dairy cattle from dairy farms over a hundred head of Tehran province. In this study، about 354 industrial units of dairy cattle under the National Livestock Breeding Center of Tehran province in 2009 were obtained and analyzed. Information of inactive units and under 100 heads capacity units was eliminated. The remaining units (199 units)، based on cattle population was sorted into ascending order. Different groups of units (100 to 299-300 to 499-500 to 999 and more than 1،000 head) according to their frequency in each class were divided by capacity. Then، according to the method of proportionate random 25% of units in each class were selected for statistical analysis. Results show that from 2523 dairy cows culled in 2009 in these units، the highest frequency cause to eliminate cows was abortion and reproductive failure with 29/4%. The next important causes were non-economic and Infectious Diseases، with 18% and 15/2% ranked second and third to have. The frequency of other causes includes metabolic disorders (9/8%)، mastitis (7/3%)، the excess of (5/3%)، physical damage (5/1%)، aging (3/6%)، Genetic defects (3/5%)، economic problem (2/1%) and finally Dystocia (0/8%). The result showed high relationship between capacity and culled cow (p<0/001). Also voluntary culling in groups of one to three was more than expected. This indicates better management and more successful groups in this capacity. Likewise in the fourth batch capacity، voluntary culling was 50 percent less than the expected rate. This means that the forced removal of the animals in the herd causes the farmer have no chance to selected benefit cows.