IntroductionDuring the first two to eight weeks of lactation high yielding cows undergo a period of energy deficit. This negative energy balance is due to the fact that dietary intake cannot meet the energy requirements for milk yield and maintenance. Peak milk yield is reached four to seven weeks after parturition (IT), whereas the highest food intake is not reached until eight to ten weeks after calving (37, 13). Due to the negative energy balance, the blood concentration of glucose (gluc) falls and the body reserves of fat and protein are mobilized. The blood concentration of free fatty acids (FFA) is elevated and hepatic ketogenesis is accelerated, which increases the blood concentrations of the main ketone bodies, acetoacetate (AA) and Phydroxybutyrate (BHB).This negative energy status is almost normal for a dairy cow in the early stage of lactation. A whole blood concentration of AA (AA concn) interpreted as subclinically or

No abstract

No abstract

No abstract

IntroductionBovine ketosis has been regarded as a disease of great economic significance, due to its effect in reducing milk production and fertility. The effect of subclinical ketosis on milk yield and fertility is difficult to estimate, since the subclinical state cannot be detected without specific metabolic tests including the determination of the blood concentration of ketone bodies and glucose. Subclinical and clinical ketosis are due to the energy imbalance caused by the energy requirement for milk production, which cannot be met by the nutritional energy intake. This imbalance is in turn expected to reduce milk yield, but to exactly what extent has been evaluated in relatively few studies. PEHRSON (20) found a significantly lower milk yield of ketotic cows than that of the same cows before the onset of ketosis. KING (13) showed milk yield to be lower in ketosis than after recovery.The effect of ketosis on fertility is also not clear and the studies concerning this problem have yielded conflicting results (16, 17). The adverse effect of severe fatty liver on fertility, however, has been demonstrated (23). The plasma activity of ornithine carbamoyltransferase ( O C T act.) and aspartate aminotransferase (ASAT act.), indicators of probable liver damage, were shown to be highly significantly dependent on the whole blood concentration of acetoacetate (AA concn.) as determined for normal, subclinically and clinically ketotic cows (1 1).The aim of this study was to compare calving intervals, annual milk yield, and fat and protein content of the milk between normal, subclinically and clinically ketotic cows. The correlations of calving intervals, annual milk yield, milk fat and protein with the plasma activity of alanine aminotransferase (EC 2.6.1.2. ALAT act.), y-glutamyltransferase (EC 2.3.2.2. GGT act.), ASAT act. (EC 2.6.1.1.), alkaline phosphatase (EC 3.1.3.1. AP act.), OCT act. (EC 2.1.3.3.), the AA concn. and the plasma concentration of urea (ureaconcn.) and the TBR concn., respectively, were determined. The dependence of annual milk yield, calving interval, insemination number and pregnancy on the same blood parameters were studied. In addition, the correlations of whole blood concentration of glucose (gluc. concn.) and P-hydroxybutyrate (BHB concn.) with the calving interval, milk yield, fat and protein contents were determined. US. Copyright Clearance Center CodeStatement: 0721--0981/84/3109-0694$02.50/0 Annual Milk Yield and Reproductive Performance 695 Material and MethodsBlood samples were obtained from each of 600 Friesian and Ayrshire dairy cows during 11-72 days post partum. The cows were clinically examined before sampling and primary ketosis was diagnosed as clinically manifested in 114 animals, which were treated after the first sampling. Clinically healthy cows of the same age and at approximately the same stage of lactation as the clinically ketotic ones were sampled during the visit to the farm. The clinically healthy cows were sampled once and ketotic ones twice during a month after the fi...