Effects of housing conditions on dairy performance and length of productive life of Black-and-White cows with a high proportion of Holstein blood
The aim of the work is to study the effect of different housing conditions on milk production, the reasons for culling and length of productive life (LPL) of Black-and-White cows with a blood share of 78-92% for Holstein breed obtained from bulls-sires of different countries of origin. On the four farms of the Sokolovka breeding farm of the Zuyevo district in the Kirov oblast, the cows were a year-round tethering or loose box housing without walking and pastures, milking robotic or in the milk conduit. The average LPL of cows in the general herd was 3.8 lactations. The main causes of cows culling are diseases of the reproductive system, 17.5%, metabolic disorders, 15.7%, pulmonary disorders, 14.9%, mastitis, 11.6% and orthopedic diseases, 11.4%. The almost identical form of Gompertz curves describing the age dynamics of the intensity of cows leaving herd is noted for the total sum of causes and for the sum of three causes - metabolic disorders, diseases of the reproductive organs and diseases of the digestive tract. This can be interpreted as an indirect indication on the existence of causal relationships in the etiology of these groups of diseases. The highest average productivity (7200 kg for 305-days lactation) was observed on a farm with loose housing on rubber mats, without pasture, with robotic milking. In the herd, there were no significant differences in LPL between groups of daughters of bulls-sires from different countries of origin (USA, Canada, Netherlands, Germany, Russia). Against this background, the daughters of Danish bulls were less viable, the average LPL was 2.9 lactations, the fertility coefficient was 0.072 (with 0.074 an average in herd). Animals under farm conditions did not have high adaptive qualities, which limits the possibilities of realizing their genetic potential of milk productivity and longevity.