Validation of a calf-side β-hydroxybutyrate test and its utility for estimation of starter intake in dairy calves around weaning

Abstract

Recent research suggests that circulating β-hydroxybutyrate (BHB) levels may be a meaningful indicator of grain intake and rumen development in pre-ruminant calves. As such, BHB levels may be a surrogate measure of rumen function to contribute to minimal weaning stress during the transition from liquid to solid feed. The primary objective of this study was to determine the optimal cut-point of circulating BHB levels that would be predictive of sufficient grain intake and rumen development for a successful transition from liquid to solid feed at the time of weaning. An additional objective was to validate the Precision Xtra (Abbott Diabetes Care, Abingdon, UK) calf-side test for determination of BHB in whole blood in calves around weaning, as compared with the gold standard laboratory method. A total of 20 Holstein female calves were randomly assigned at birth to be weaned at 6 wk (n=10) or 8 wk (n=10) of age. Milk replacer (mixed at 150 g/L) was offered at 1.2kg/calf per d in 2 meals until a 1-wk step down, when milk meals were reduced by 50% 1 wk before weaning. Daily measurements included the intakes of starter grain, chopped straw, and water. Weekly measurements included body weight and blood BHB, until 70 d of life. To assess digestive tract development, rumen fluid samples were taken before and after weaning (d 35, 49, and 63) and analyzed for ruminal short-chain fatty acids. Whole blood was collected by jugular venipuncture, and BHB was determined by the Precision Xtra test at calf-side. In addition, serum was separated from a clotted sample, frozen, and stored until laboratory analysis was performed. Laboratory BHB results were correlated with both the Precision Xtra test (r=0.95) and starter intake over 1 d (r=0.89), a 3-d average (r=0.90), and a 7-d average (r=0.90). Additionally, laboratory BHB results were associated with total ruminal volatile fatty acids (r=0.82), ruminal butyrate (r=0.77), and body weight (r=0.69). A receiver operating characteristic curve was created to plot the true positive rate against the false positive rate at 10μmol/L BHB intervals to determine the optimal cut-point of circulating BHB that is predictive of an average starter intake of 1,000 g/d over a 3-d period. The optimal combination of sensitivity (95.7%) and specificity (96.1%) was at 100µmol of BHB/L of blood. A value of 0.2 mmol/L on the Precision Xtra test yielded a sensitivity and specificity of 84.0 and 97.2%, respectively, over the 3-d average period of starter intake. These results show considerable promise for use of the Precision Xtra whole blood BHB test in the decision-making process of determining sufficient starter grain intake and rumen development for a successful transition from liquid to solid feed, and indicate that this test conducted at calf-side is highly accurate.

Abrupt weaning reduces postweaning growth and is associated with alterations in gastrointestinal markers of development in dairy calves fed an elevated plane of nutrition during the preweaning period

“…The major pathway for VFA metabolism in the rumen epithelium is ketogenesis (Leighton et al, 1983), the conversion of butyric acid into BHB. Because this BHB can be easily measured in blood, this has recently been tested as a method for estimating calf feed intake, ruminal fermentation, and readiness to wean (Deelen et al, 2016). The BHB results of the current experiment suggest that the step-down influenced ruminal fermentation, because higher plasma BHB is significantly higher at 48 d in the gradual compared with abrupt weaning treatment (Table 2).…”

Nitrogen utilization, preweaning nutrient digestibility, and growth effects of Holstein dairy calves fed 2 amounts of a moderately high protein or conventional milk replacer

“…This can be correlated with lesser rumen development, as was seen in significant treatment by week interactions for BHB concentrations during the 56-d trial (Figure 2). Studies have suggested that circulating BHB levels may be an indicator of rumen epithelial development and starter intake in preweaned calves (Quigley et al, 1991;Deelen et al, 2016). Quigley et al (1991) observed that total blood concentrations of VFA were greater in calves weaned early and that blood VFA responded rapidly to dry feed intake.…”

Different milk feeding intensities during the first 4 weeks of rearing dairy calves: Part 2: Effects on the metabolic and endocrine status during calfhood and around the first lactation

“…Preruminant animals are basically capable of hepatic ketogenesis when fasted, but the increase of BHB in the circulation is more likely related to the beginning ruminal production of ketones (Baldwin et al, 2004). The suitability of serum BHB as an indicator for grain intake and rumen development in calves was recently confirmed (Deelen et al, 2016). Indeed, the intakes of concentrate and the BHB serum concentrations when all calves were fed according to the MR-res protocol until weaning showed the same pattern; the highest values in both variables were observed in the WM-ad lib and MR-res groups, whereas the MR-ad lib group ate about 200 g/d less concentrate (Korst et al, 2017) and had around 80% of the BHB concentrations.…”