Physiological Markers Aid Nutrition Intervention
Dairy producers and nutritionists are constantly looking for new analytical tools that can help monitor nutrition-related parameters to allow for early intervention and correction.
These tools have typically been laboratory analyses targeted at the diet or focused on measuring pen intakes or total mixed ration sorting. However, nutritionists may want to start considering some recent advances in physiological markers, particularly when formulating and monitoring transition and fresh cow diets.
Negative Energy Balance
Monitoring physiological blood metabolites such as non-esterified fatty acids (NEFA) and beta-hydroxybutyrate (BHBA) has been used for a number of years for identifying opportunities to decrease the incidence of metabolic disorders.
Measuring these blood metabolites, which are associated with negative energy balance around calving and insulin resistance in adipose tissue (e.g., prepartum NEFA and postpartum NEFA and/or BHBA), has taken on new importance given the relationship they appear to have with reduced dry matter intake, milk production and reproductive performance (Huzzey and Overton, 2013).
During late pregnancy, insulin resistance in adipose tissue contributes to increasing plasma NEFA concentrations, and the subsequent oxidation of NEFA by the liver is the cause of decreasing intake as cows approach calving. The practical nutritional aspect relates to energy nutrition during the dry period interacting with insulin resistance during the late prepartum period.
The hepatic oxidation theory approach to close-up cow diets is to provide moderate inclusion rates of highly fermentable starch to increase insulin levels and potentially reduce fat mobilization. This is followed by fresh cow diets of low to moderate starch fermentability to allow for higher starch inclusion rates without causing acidosis or reducing meal size (Feedstuffs, Feb. 14, 2011).
Excess energy intake during the closeup period and the far-off dry period further increases insulin resistance. It appears that overfeeding energy to dry cows results in changes in metabolism that predispose cows to decreased intake and higher NEFA levels. Cows with high body condition scores are particularly at risk, leading to the recommendation for far-off and close-up groups to meet — but not exceed — energy requirements by more than 110-120%.
Controlling energy intake via high-bulk diets (containing straw) or moderately restricted feeding prepartum results in similar metabolic profiles , but limit feeding is difficult to manage if cows and heifers are commingled in pens (Butler, 2012).
More dairies are adopting routine monitoring of these energy-related markers due to increased availability of fast, accurate and low-cost cow-side tests for BHBA in the blood (Precision Xtra, Abbott Laboratories) and milk (KetoTest, Elanco Animal Health), according to Huzzey et al. (2012).
Blood samples must be sent to a commercial laboratory for the now routine analysis of NEFA. Due to convenience and cost, evaluation of postpartum BHBA in milk or blood at the farm level is the preferred first-line monitoring tool, although prepartum and postpartum NEFA concentrations in serum or plasma can provide additional insight into transition management opportunities (Huzzey et al., 2012).
In a series of studies involving more than 2,700 cows, Cornell University researchers (Ospina et al., 2010a and 2010b) described the associations of prepartum (from 14 to two days prepartum) and postpartum (days 3-14 postpartum) concentration levels of NEFA and BHBA collected from the tail vein or artery with postpartum health, milk production and reproductive performance.
The table below references critical NEFA and BHBA threshold levels derived from this field study. Regardless of parity, animals with greater than about 0.3 milliequivalents per liter (mEq/L) of NEFA during the prepartum period had nearly 700 kg less projected metabolizable energy-corrected 305-day (ME305) milk production than animals with lower concentrations. In this study, 45% of heifers and 26% of multiparous cows tested had NEFA concentrations at or above the 0.3 mEq/L threshold.
Summary of critical NEFA and BHBA thresholds as predictors of disease, milk yield and reproductive performance during the two-week period before and after calving.
|NEFA > 0.29 mEq/L
||Cattle 1.6 times more likely to develop displaced abomasum, clinical ketosis or metritis.
|NEFA > 0.27 mEq/L
||19% decreased risk of conception in all cattle.*
|NEFA > 0.33 mEq/L
||683 kg lower mature equivalent 305-day milk yield.
|NEFA > 0.57 mEq/L
||Cattle 1.9 times more likely to develop displaced abomasum, clinical ketosis or metritis. Heifers: 488 kg higher mature equivalent 305-day milk yield.
|NEFA > 0.72 mEq/L
||16% decreased risk of conception in all cattle.* Cows: 647 kg lower ME305-day milk yield.
|BHBA > 10 mg/dL
||Cattle 3.1 times more likely to develop displaced abomasum, clinical ketosis or metritis 13% decreased risk of conception in all cattle.* Cows: 393 kg lower mature equivalent 305-day milk yield.
|BHBA > 9 mg/dL
||Heifers: 403 kg higher mature equivalent 305-day milk yield.
* Risk of conception within 70-day post-voluntary waiting period. Adapted from Huzzey and Overton, (2013).
In heifers, postpartum NEFA concentrations greater than about 0.6 mEq/L and BHBA concentrations greater than about 9 mg/dL were associated with increased milk yield. However, in multiparous cows, postpartum NEFA concentrations greater than about 0.7 mEq/L and BHBA concentrations greater than about 10 mg/dL were associated with lower predicted milk yield. In the postpartum group, 25% of heifers and 33% of multiparous cows had NEFA concentrations at or above 0.7 mEq/L, while 15% of primiparous animals and 27% of multiparous cows had BHBA concentrations at or above 10 mg/dL.
On each farm in the study, 15 cows were randomly selected from a prepartum group and 25 cows from a postpartum group. The researchers noted that in the vast majority of participating field study farms, heifers and multiparous cows were commingled during the period before calving. The study suggests that heifers may be compromised from the standpoint of energy intake relative to requirements and that these energy-related analytes appear more likely to be elevated in multiparous cows than heifers during the period after calving (Huzzey et al., 2012).
As a result of this study, Cornell researchers recommend sampling 12-15 cows per group. Prepartum samples should be analyzed for NEFA and postpartum samples analyzed for NEFA and/or BHBA. The cow-side blood or milk test for BHBA provides an excellent, cost-effective first-step analysis. However, the incidence of herds with high postpartum NEFA in their study was much greater than those with high postpartum BHBA, so the researchers are encouraging analysis for postpartum NEFA when early-lactation production and reproductive performance are below expectations despite acceptable BHBA levels.
Prepartum NEFA is also useful in identifying situations where a large proportion of prepartum cows have a compromised energy status (Huzzey et al., 2012).
Given the physiological, nutritional, environmental and social changes cows experience around parturition, research interest is now turning to monitoring biomarkers of stress (fecal cortisol [FCort]) and inflammation (haptoglobin) to reveal opportunities for improvements in transition cow nutrition and management.
Plasma cortisol has long been used to measure physiological stress in animals; however, restraint and handling during blood sampling can raise blood cortisol concentrations, which can fluctuate greatly across the day. Fecal cortisol metabolites (11,17-dioxyandrostanes) are the preferred alternative to plasma cortisol since their concentrations are not influenced by handling stress and are less variable over the course of the day.
Fecal cortisol metabolites are reflective of circulating concentrations of cortisol approximately 10-12 hours prior to the collection of the fresh fecal sample (Huzzey and Overton, 2013).
Measures of the immune acute phase response during the transition period may provide information about the level of risk for developing subsequent health and production complications. The acute phase protein haptoglobin is a non-specific marker of inflammation, injury or infection that has been shown to be useful for the early identification of common transition cow disorders; cows exhibiting haptoglobin levels greater than 1 g per liter on day 3 after calving are nearly seven times more likely to develop mild or severe metritis (Huzzey and Overton, 2013).
To field test the utility of stress and inflammation biomarkers, Cornell researchers collected blood and fecal samples from 412 Holstein cows beginning three weeks before calving and collected one sample within 3-10 days post-calving to determine if NEFA, cortisol, haptoglobin or FCort concentrations could be used to identify animals at an increased risk for disease or performance problems (Huzzey and Overton, 2013).
There were no associations between prepartum haptoglobin or FCort concentration and the occurrence of a single disorder (retained placenta, displaced abomasum, subclinical ketosis or high haptoglobin, suggestive of an infection such as metritis). The haptoglobin concentration tended to be 23-43% higher during the second and first weeks before calving, and FCort tended to be 11% higher during the third and second weeks pre-calving for cows that developed more than one disorder or that died by 30 days in milk relative to cows displaying no health problems.
However, neither of these analytes could predict which cows would go on to develop health complications as well as prepartum NEFA concentrations did. As shown in other studies, prepartum plasma NEFA was a strong predictor of postpartum health, but the relationship was dependent on the degree of illness after calving.
Cows that developed multiple disorders after calving or died had the greatest concentrations of NEFA, particularly during the two-week period before calving (Huzzey, et al., 2012).
Post-calving levels of haptoglobin exceeding 1.1 g per liter were associated (P = 0.001) with a 947 kg lower projected ME305 milk yield for both heifers and multiparous cows, while higher FCort concentrations after calving were associated (P = 0.03) with lower projected ME305 milk yield for multiparous cows only (Huzzey et al., 2012).
Associations between the analytes of interest and reproductive performance were generally limited to primiparous cows. Primiparous cows with FCort greater than 2,300 ng/g of fecal dry matter during the two-week period before calving had a 36-42% decreased risk of pregnancy by 150 days in milk, suggesting that increased prepartum stress is associated with compromised reproductive performance.
Heifers with haptoglobin exceeding 0.4 g per liter during the week before calving or greater than 1.3 g per liter during the week after calving had a 41% decreased risk of pregnancy by 150 days in milk (Huzzey et al., 2012).
Blood samples must be sent to a commercial laboratory for the analysis of NEFA, haptoglobin and FCort. While most animal health laboratories routinely measure NEFA, only a handful offer haptoglobin assays (e.g., the Ontario Veterinary College’s Animal Health Laboratory or Kansas State University’s Veterinary Diagnostic Laboratory).
Presently, there are no commercial laboratories that offer an assay to measure Fcort concentrations. However, given the strong relationship that biomarkers of inflammation and stress have with milk yield and reproductive performance, further research will be conducted to develop these analytes as potential tools to help identify opportunities for improved transition cow management (Huzzey and Overton, 2013).
The Bottom Line
Transition and fresh cows incur stress and negative energy balance from physiological and environmental changes, coupled with increased energy demand and lagging dry matter intake. Physiological biomarkers may represent the next frontier in tools to help identify herds that warrant nutritional and management intervention for these important groups of cows.
In numerous studies, elevated levels of fat mobilization metabolites such as NEFA and BHBA have been shown to be associated with increased metabolic disorders and poor reproductive performance.
More recent research shows that there are tangible thresholds for these metabolites that are associated with reduced milk production. Despite the lack of routine laboratory assays, research is beginning with stress and inflammation biomarkers such as Fcort metabolites and blood haptoglobin that also appear to be associated with decreased milk yield and reproductive performance.
Butler, W.R. 2012. The role of energy balance and metabolism on reproduction of dairy cows. Proceedings of the 2012 Cornell Nutrition Conference for Feed Manufacturers.
Huzzey, J.M., and T.R. Overton. 2013. Using physiological markers to detect health and production problems in transition dairy cows. Proceedings of the Western Canadian Dairy Seminar. Advances in Dairy Technology. 25:329-339.
Huzzey, J.M., D.V. Nydam, P.A. Ospina and T.R. Overton. 2012. Using physiological markers in herd-level transition diagnostics. Proceedings of the Four-State Dairy Nutrition & Management Conference. Dubuque, Iowa.
Nydaml, D.V., P.A. Ospina, J.A. McArt, G. Oetzel and T.R. Overton. 2013. Monitoring negative energy balance in transition dairy cows for herd results. Proceedings of the Tri-State Dairy Nutrition Conference. Ft. Wayne, Ind.
Ospina, P.A., D.V. Nydam, T. Stokol and T.R. Overton. 2010a. Evaluation of nonesterified fatty acids and beta-hydroxybutyrate in transition dairy cattle in the northeastern United States: Critical thresholds for prediction of clinical diseases. J. Dairy Sci. 93:546-554.
Ospina, P.A., D.V. Nydam, T. Stokol and T.R. Overton. 2010b. Associations of elevated nonesterified fatty acids and betahydroxybutyrate concentrations with early lactation reproductive performance and milk production in transition dairy cattle in the northeastern United States. J. Dairy Sci. 93:1596-1603.
Ospina, P.A., D.V. Nydam, T. Stokol and T.R. Overton. 2010c. Association between the proportion of sampled transition cows with increased nonesterified fatty acids and beta-hydroxybutyrate and disease incidence, pregnancy rate and milk production at the herd level. J. Dairy Sci. 93:3995-3601.
Originally published in the February 2014 Feedstuffs issue. Reproduced with permission.