Effects of ketosis disordey on blood factor and milk yield and composition in Holstein dairy cows in Golestan province.

Fifty healthy pregnant Iranian Holstein cows were selected random from 10 commercial dairy farms in Golestan province in Iran for this study. Milk and blood were sampled eight times on d 3, 7, 10, 14, 17, 21, 24 and 28 after calving (within period most susceptible to ketosis) while milk yields of the cows were determined twice weekly for 60 d after calving. Cows were milked three times daily for 60 d after calving, and the milk production of individual cow at each milking was recorded, pooled for the day as the daily milk production. Corn silage and total mixed ration were sampled eight times on d 3, 7, 10, 14, 17, 21, 24 and 28 after calving then transferred to the laboratory for chemical analysis including pH and fatty acids profile and nutrients. Fifty eigh t percent of the cows had SCK during first month of lactation in Golestan province, Iran. High correlation coefficients were observed between plasma BHBA and plasma NEF A, and between plasma and milk BHBA. Milk yield of cattle with SCK decreased (P0.01) but fat percentage and milk fat: protein ratio increased (P0.01) as compared to those of the health cows. The commercial keto‎صtest paper used had a low false positive result at a cut-off point of 200 umol of BHBA/L of milk. The results showed that the best time to assess SCK using the commercial keto-test paper was 10, 14 and 17 days after in the total mixed ration (TMR), net energy for lactation (NEL, 1.48 Meal/kg), crude protein (CP, 13.4%) and NFC (30.5%) were lower while the fibre (NDF 44.23%) were higher than the recommended requirements of lactating cows, only NEL was found to besignificantly tO. 05) affecting incidence of SCK. Butyric acid concentration in the corn silage as high in four out of the ten farms studied but butyric acid had no significant effect on the occurrence SCK. Cows showed more than 0.5 unit loss of BCS during first month after calving because of the low energy content of the TMR used in the farms. However, BCS at calving was normal in most of the dairy cows and had no significant effect on the incidence of SCK. Key words: Subclinical ketosis, BHBA, NEFA, Milk yield and components