Based on a solid foundation
The basis for this argument comes from the results of a series of large, epidemiologic studies involving multiple herds and large numbers of cows over the past 10 years. Several of these have been collaborative efforts between our research groups at Cornell University and one was a very large study led by the University of Guelph with a number of collaborators across the U.S. and Canada.
In general, these studies evaluated the relationships between serum- or plasma-based markers of energy metabolism such as nonesterified fatty acids (NEFA) or B-hydroxybutyrate (BHB), minerals such as calcium, and acute-phase proteins such as haptoglobin (a non-specific marker of inflammation in the cow). These measurements were connected to disease risk, subsequent milk yield, and reproductive performance.
The studies are listed in the table and vary in approach, sampling times relative to calving, and in analytical strategy. However, in general, these studies were focused on determining relationships between the percentage of cows in a herd that would have concentrations of NEFA and BHB above critical thresholds and calcium below a critical threshold during the time period of interest. They also measured outcomes related to clinical disease, subsequent milk yield, and reproductive performance. Although the thresholds and the percentage of cows within a herd that would indicate an “alarm” level vary across studies, the results generally indicate very meaningful associations of these serum and plasma markers with subsequent milk yield and reproductive performance.
What we have learned
In the study conducted by Nuria Chapinal and co-workers, there was no relationship between NEFA and clinical diseases of interest at the herd level. There was, however, very important negative relationships between the percentage of cows in these herd with elevated NEFA and outcomes related to milk yield and reproduction. We should not entirely discount relationships of NEFA and BHB with disease as the relationships of these markers with disease are also important, particularly at the cow-level. We miss the mark, though, if we focus solely on clinical disease as our outcome.
Although the study conducted by Julie Huzzey as part of her Ph.D. program at Cornell focused on inflammation in the transition cow, it was not designed to determine herd-level alarms. Even so, nearly 40 percent of first-calf heifers and 30 percent of second-lactation or later cows had elevated concentrations of haptoglobin during Week 1 postcalving and relationships at the cow-level with subsequent milk yield and reproduction were large. We currently are evaluating relationships of inflammation as indicated by elevated haptoglobin levels with postpartum outcomes in a large, commercial farm-based study with cooperating farms in New York and Vermont.
Results from these studies have supported the development of herd-level monitoring programs for BHB to better understand the prevalence of, and opportunity to manage, subclinical ketosis. Subclinical hypocalcemia is also highly prevalent, even in herds with low rates of clinical milk fever. With further development, we anticipate that there will be additional opportunities to create more convenient and cost-effective herd-level monitoring programs related to calcium, NEFA, and inflammation markers such as haptoglobin in the future.
The future of transition cow health
We have made great progress caring for the transition cow over the past 25 years. That will continue going forward with the combination of continued research and implementation of new knowledge and strategies to enhance transition cow management and keep pushing the bar of success even higher.