Retrospective analysis of body energy content profiles of dairy cows with different production and metabolic diseases during the transition period
Characteristics of body energy profiles for dairy cows with production and metabolic diseases during the transition period were studied. 542 cow-lactations from Holstein Friesians were used. Cows were from one of the four divergent production systems that were based on two feeding regimes - high forage and low forage and two genetic lines – control and select. Control cows were of average UK genetic merit and Select cows were of high genetic merit based on selection for fat and protein yield. Cows were milked three times daily and stockmanship was similar across all systems. Live-weight of individual cows was recorded 3 times daily in lactation and weekly in the dry period. Body condition score (BCS) was recorded weekly using a 5 point scale. Health records were maintained throughout the study period.
First, prevalence of disease within the first 4 weeks after calving was determined, as a proportion of cow lactations with disease relative to the total number of cow lactations per production system. Second, cow-lactations were categorized into disease-groups; retained placenta, metritis, metabolic and healthy. The group, ‘metabolic’, comprised left displaced abomasum, ketosis, hypomagnesaemia and hypocalcaemia. Body energy content in mega joules was calculated using the equation; EC = ((9.4 x body lipid weight) + (5.7 x body protein weight)) x 4.1868. Body lipid and protein weights were calculated using standard equations which included live weight, BCS and days pregnant. EC profiles covered the period between 6 weeks pre-calving and 4 weeks post-calving.Effects were determined using the GLM procedure of SAS.
High genetic merit cows on a forage rich diet and average genetic merit cows fed a low forage diet had the highest prevalence of disease (30 and 25%, respectively). In the pre-calving period, healthy cows had a EC of 5878±24 MJ which was significantly lower (P<0.01) than those that had retained placenta (6384±156 MJ) or metritis (6156±46 MJ). Cows that developed metabolic diseases had significantly lower EC (5466±216 MJ) than cows with retained placenta or metritis (P<0.01) In the post- calving period the metabolic disease group had significantly lower EC (P<0.001) than all other disease groups. The study demonstrated that EC is an important lead indicator of production diseases in the transition period. Real-time tracking of EC could be used to rank individual cow risk of developing metabolic diseases.
Keywords: transition period, energy content, production disease