Exposure to chronic light-dark phase shifts during the prepartum nonlactating period attenuates circadian rhythms, decreases blood glucose, and increases milk yield in the subsequent lactation.

Maintaining metabolic balance is a key factor in the health of dairy cattle during the transition from pregnancy to lactation. Little is known regarding the role of the circadian timing system in the regulation of physiological changes during the transition period. We hypothesized that disruption of the cow's circadian timing system by exposure to chronic light-dark phase shifts during the prepartum period would negatively affect the regulation of homeostasis and cause metabolic disturbances, leading to reduced milk production in the subsequent lactation.

Characterization of the analytic performance of an electrochemical point-of-care meter for measuring β-hydroxybutyrate concentration in blood and plasma from periparturient dairy cattle.

Background: The Precision Xtra electrochemical meter is widely used to measure blood β-hydroxybutyrate concentration (BHBb) in dairy cattle. The meter uses an algorithm optimized for human blood that assumes the HCT in cattle is the same as in people, and that intra-erythrocyte β-hydroxybutyrate (BHBe) and plasma β-hydroxybutyrate (BHBp) concentration are equivalent.

Objectives: The first objective was to characterize the analytic performance of the meter for measuring BHBb and BHBp in dairy cattle.

Clinical utility of calf front hoof circumference and maternal intrapelvic area in predicting dystocia in 103 late gestation Holstein-Friesian heifers and cows.

The objective of this study was to determine the clinical utility of measuring calf front hoof circumference, maternal intrapelvic area, and selected morphometric values in predicting dystocia in dairy cattle. An observational study using a convenience sample of 103 late-gestation Holstein-Friesian heifers and cows was performed. Intrapelvic height and width of the dam were measured using a pelvimeter, and the intrapelvic area was calculated.

Dexamethasone-induced exophthalmos in a group of Holstein calves.

Six Holstein calves were evaluated for progressive exophthalmos. The affected calves were receiving daily injections of dexamethasone (30 microg/kg subcutaneously twice daily) as part of a metabolic study. The control calves did not exhibit exophthalmos.