Editor’s note: This article was written by Robert Van Saun, Extension veterinarian, Penn State Department of Veterinary and Biomedical Sciences and first appeared in the Penn State Dairy Digest.
Ensuring more cows will transition smoothly from pregnancy into lactation is one of the ongoing challenges to dairy production. Field surveys show that more than 50 percent of cows will experience one or more metabolic or infectious disease process following calving, though on any given farm this may range from minimal (< 20 percent) to the extreme (> 80 percent). Much research has focused on underlying mechanisms that result in high disease susceptibility at this time in a cow’s life. Initially the research focus was on metabolic changes, especially those related to energy balance and the observed decline in feed intake immediately around calving. These observations spawned much interest in using measures of energy balance, namely nonesterified fatty acid (NEFA) and beta-hydroxybutyrate (BHB) concentrations to diagnose or predict postpartum disease risk, but no intervention method has been identified to successfully treat cows with higher NEFA or BHB concentrations to prevent the disease process.
A number of feeding practice cycles suggesting higher or lower energy intake, maximizing or optimizing feed intake, low calcium or DCAD diets have come and gone without significant overall improvements in transition cow health across farms. Although the research documented protein needs of the transition cow suggest a low requirement, most farms feed a higher protein level in the prepartum diet; yet this has not reduced postpartum disease. Some of these dietary approaches seemingly work on one farm, but not consistently on other farms. Ultimately it would seem something more than nutrition alone.
Recent research into transition cow problems from the University of Wisconsin have focused less on nutritional manipulations, but more on management practices and cow-to-environment interactions. Wisconsin researchers identified feed bunk space, excessive cow pen moves during transition, and cow comfort issues related to stall design as important contributors to postpartum disease risk. Part of the environmental or management contribution to postpartum disease issues may result from physiologic responses to stress. When cows experience stressful conditions, stress hormones are released that induce a number of metabolic changes as well as activating immune cells of the body. Activated immune cells induce the release of chemical messengers called cytokines from these cells that modify many body responses. Key inflammatory cytokines alter metabolism so that more nutrients are partitioned to maintenance, thus reducing production efficiency. Additionally, inflammatory cytokines cause a reduction in dry matter intake, a central issue to transition cow problems.
In reviewing production data from cows participating in two separate feeding trials previously performed at Penn State, we identified a collection of cows that had absolutely no problems through transition as well as a population of cows that had one or more diagnosed problems. In comparing these two groups we found some interesting differences. Most significant of our findings was the dramatic difference in dry matter intake between the two groups over the first five weeks of lactation. As expected, cows without disease problems had significantly higher postpartum intake over all five weeks for any disease process (metritis, retained fetal membranes, mastitis, ketosis, udder edema). This was of interest as disease diagnosis for many postpartum diseases does not occur until 7 to 21 days after calving.
In evaluating body weight, body condition score change, and milk yield differences between healthy cows and cows experiencing disease, we saw no significant change in body weight or condition score, but highly significant losses in milk starting in the first week postpartum. This observation emphases that cows experiencing various postpartum disease conditions are losing milk prior to when the problem is diagnosed. Based on dry matter intake differences and known energy density of the diets, we predicted potential milk losses over this 5-week period. Observed milk losses were greater than we predicted, most likely due to effects of inflammatory cytokines altering nutrient usage in the body.
Another fascinating aspect of this data evaluation was the comparison of dry matter intake prepartum. Unlike what we observed during the postpartum period, there were not significant differences in daily dry matter intake between healthy cows and cows that went on to become sick. However, we did find a significant interaction between health status and week prepartum between these cow groups. Cows that went on to have postpartum disease showed a greater decline in dry matter intake during the last 2 to 3 weeks prior to calving. Healthy cows maintained a more stable prepartum intake up until the day of calving. This observation reinforces the Wisconsin work suggesting environmental factors that affect intake are significant contributors to postpartum disease problems. Other research from the University of British Columbia has also shown cows that go on to have postpartum metritis or ketosis problems have altered feeding patterns and lower overall intake during the prepartum period compared to cows that remain healthy. What exactly causes this altered intake resulting in greater disease susceptibility is unknown.
Although reports would suggest progress is slow in preventing transition cow problems, we have made a number of strides in better understanding underlying contributing issues. Significant progress has been achieved on many individual farms. As we have learned more about transition metabolism and cow-environment interactions, we are realizing just how complicated the adaptations to transition is for the cow. As we move forward in this field, we will need to better address the complex interaction of metabolism, environment, and immunologic response especially in relation to how this interaction influences cow eating patterns prior to parturition. Monitoring and controlling feed intake in the 4 to 5 weeks prior to calving may be our best approach to preventing transition problems and minimizing production losses.
Source: Penn State Dairy Digest