EffEct of changEs in body condition scorE on thE milk yiEld of holstEin-friEsian and brown swiss cows

GerGovska, Z., Y. Mitev, t . anGelova, D. YorDanova and t . Miteva, 2011. effect of changes in body condition score on the milk yield of Holstein-Friesian and Brown swiss cows. Bulg. J. Agric. Sci., 17: 837-845 the effect of BCs at calving, loss of BCs, the duration of loss after calving and the reached minimum BCs during lactation on milk yield for 305 days have been studied. the object of study are 37 cows, of which 20 Holstein and 17 Brown swiss ones. the cows from both breeds are reared together with the same technology and nutrition. the body condition score of cows has been recorded on a monthly basis by using a 5-grade scor ing system and accuracy of recording up to 0.5 points. BCs at calving, loss of BCs and the duration of loss after calving have significant effect on milk yield. The reached minimum BCS during lactation has no significant effect. in the Holstein cows BCs before calving is lower (2.8 points), loss of BCs is greater (1.95 points) and longer (3.8 months compared to the Brown cows (3.0, 1.75 and 2.8, respectively). Cows from both breeds with higher BCS (≥3.5 points), with greater loss of BCS after calving (≥2.5 points) and longer loss of BCS at the beginning of lactation (≥5 months) have the highest milk yield for a 305-day lactation.