The effect of prepartum injection of vitamin E on health in transition dairy cows.

The objective of this study was to investigate parenteral vitamin E for the prevention of peripartum disease in dairy cows. A randomized clinical trial was conducted in 21 commercial dairy herds. Cows (n = 1142) were randomly assigned to receive either a single subcutaneous injection of 3000 IU of vitamin E, or placebo, 1 wk before expected calving.

Prepartum monensin for the reduction of energy associated disease in postpartum dairy cows.

A total of 1317 Holstein cows from 45 farms in the Canadian provinces of Quebec, Prince Edward Island (PEI) and Ontario were enrolled in a randomized trial during 1998 and 1999 to further confirm the efficacy of a monensin controlled release capsule in preventing periparturient disease in lactating dairy cows. Cows were randomized on the farms to receive either a monensin controlled release capsule (CRC) 2 to 4 wk before expected calving or to serve as negative controls. Health data were collected for 90 d postcalving and were analyzed with logistic regression accounting for the intraherd correlation with generalized estimating equations.

Effect of a prepartum administration of monensin in a controlled-release capsule on apparent digestibilities and nitrogen utilization in transition dairy cows.

The influence of a monensin controlled-release capsule, which was administered 3 wk before the calving date, on diet digestibility and nitrogen utilization was investigated in 16 multiparous dairy cows between approximately 10 and 3 d precalving and 3 and 9 d postcalving. Monensin decreased rumen ammonia from 5.4 to 3.

Short communication: effects of monensin on 3-methylhistidine excretion in transition dairy cows.

Urinary 3 methyl-histidine excretion was measured in high yielding dairy cows between 10 and 3 d precalving and between 3 and 9 d postcalving. Cows received a sodium monensin controlled-release capsule or a placebo 3 wk before calving. Monensin did not affect urinary 3 methyl-histidine.

Metabolic aspects in the etiology of displaced abomasum.

Results of studies on metabolic variables that exist prior to the diagnosis of displaced abomasum (DA) indicate that subclinical ketosis is a risk factor for DA. Serum aspartate aminotransferase activity, serum and milk betahydroxybutyric acid concentrations, and milk fat-to-protein ratios were often elevated before the diagnosis of DA, and these variables may be used to predict DA. Prevention of subclinical ketosis may prevent DA.

Subclinical ketosis in lactating dairy cattle.

Subclinical ketosis is an important and common condition of early-lactation dairy cattle. It is associated with losses in milk production and increased risk of periparturient disease. Prevention depends on several factors, including proper transition-cow nutrition, management of body condition, and the use of certain feed additives such as niacin, propylene glycol, and ionophores.

Use of ionophores in lactating dairy cattle: a review.

Ionophores are feed additives that alter rumen microbial populations through ion transfer across cell membranes. Although ionophores have been used widely in the beef industry for improved feed efficiency and control of coccidiosis, there has been limited use by the dairy industry. In Canada, the label warning prohibiting the use of monensin premix in lactating dairy cattle was removed in June 1996.

The effect of tilmicosin administered to ewes prior to lambing on incidence of clinical mastitis and subsequent lamb performance.

The effect of tilmicosin on the incidence of clinical mastitis and subsequent lamb performance was studied in 9 sheep flocks in Ontario. Ewes were treated randomly with either tilmicosin or placebo approximately one month prior to lambing. Outcome was assessed by comparing rates of clinical mastitis, palpable udder abnormalities, and preweaning (50-day) lamb weights between the 2 treatment groups, while controlling for other important variables.

Effect of a monensin-controlled release capsule on cow health and reproductive performance.

Dry cows and pregnant heifers from 25 farms near Guelph, Ontario, Canada were enrolled in a large, double-blind, randomized clinical trial designed to evaluate the impact of monensin on energy metabolism, health, and production. A total of 503 cows was given monensin in controlled-release capsules, and 507 cows were administered placebo capsules 3 wk before expected calving date. The effects of treatment on health were evaluated using a logistic regression model.

Effect of prepartum administration of monensin in a controlled-release capsule on milk production and milk components in early lactation.

Dry cows and pregnant heifers from 25 farms near Guelph, Ontario, Canada were enrolled in a large double-blind, randomized clinical trial that was designed to evaluate the impact of monensin on energy metabolism, health, and production. A total of 503 cows was given monensin in controlled-release capsules, and 507 were administered placebo capsules 3 wk prior to the expected calving date. The effects of treatment on milk production and milk components at the first three Dairy Herd Improvement (DHI) tests were evaluated using repeated measures analysis of variance.

The association between first DHI milk-test parameters and subsequent displaced abomasum diagnosis in dairy cows.

First Dairy Herd Improvement Corporation (DHI) test milk that was sampled prior to displaced abomasum (DA) diagnosis was used to examine the association between milk yield (kg), fat (%), protein (%), or fat/protein ratio and DA in dairy cows. 27 DA cases were matched to 3 controls per case by herd and calving date. Logistic regression was used to examine the effect of each milk parameter on the odds of DA, adjusting for lactation number and days in milk (DIM) at test.

Efficacy of monensin for the prevention of subclinical ketosis in lactating dairy cows.

A total of 1010 dry cows and pregnant heifers was randomly selected from 25 dairy farms near Guelph, Ontario, Canada to receive either a controlled-release capsule of monensin or a placebo at 3 wk prior to expected calving. Serum samples were obtained at the time of treatment administration, and both serum and milk samples were collected at wk 1, 2, 3, 6, and 9 postcalving. The threshold used to define subclinical ketosis was selected a priori at a concentration of > or = 1200 mumol/L of beta-hydroxybutyrate.

The association between selected metabolic parameters and left abomasal displacement in dairy cows.

The objective of this study was to examine the association between selected metabolic parameters and subsequent left displaced abomasum (LDA) diagnosis in dairy cows. Forty-four LDA cows sampled in the third week ante partum (a.p.

Effect of prepartum administration of monensin in a controlled-release capsule on postpartum energy indicators in lactating dairy cows.

The effects of monensin on the energy metabolism of dairy cows in early lactation were investigated in a large clinical trial that was randomized and double-blinded. A total of 1010 Holstein cows and first lactation heifers were allocated to receive a controlled-release capsule of monensin or a placebo at 3 wk prior to expected calving date. Treatments were randomized across 25 dairy farms located near Guelph, Ontario, Canada.

An evaluation of protein/fat ratio in first DHI test milk for prediction of subsequent displaced abomasum in dairy cows.

First DHI test milk that was sampled prior to displaced abomasum (DA) diagnosis was used to evaluate milk protein/fat ratio (PFR) for prediction of subsequent DA in dairy cows. Odds ratio, sensitivity, specificity, and likelihood ratio were determined. Twenty-seven DA cases were matched to 3 controls per case by herd and calving date.

Evaluation of five cowside tests for use with milk to detect subclinical ketosis in dairy cows.

The objective of this study was to evaluate the characteristics of five ketone tests for use with milk to detect subclinical ketosis [defined as > 1200 mumol of beta-hydroxybutyrate (BHBA)/L of blood] in dairy cows. The tests studied were the Ketolac BHB strip to detect BHBA (Hoechst, Unterschleissheim, Germany) and four tests based on sodium nitroprusside to detect acetoacetate (Rothera tests) [Ketostix strip (Bayer, Etobicoke, ON, Canada), Bioketone powder (Societé d' Analyses Biopharmaceutiques, Laval, QC, Canada), Ketocheck powder (Great States, St. Joseph, MO), and Utrecht powder (University of Utrecht, Utrecht, The Netherlands)].

An evaluation of milk ketone tests for the prediction of left displaced abomasum in dairy cows.

Two commercial milk ketone tests (Ketocheck) Great States, St. Joseph, MI and Ketolac BHB; Hoechst, Unterschleissheim, Germany) were used with milk samples collected within 2 wk postpartum to evaluate the use of these tests in the prediction of left displaced abomasum in dairy cows. Odds ratios, sensitivities, specificities, and likelihood ratios were determined.

Evaluation of aspartate transaminase activity and beta-hydroxybutyrate concentration in blood as tests for prediction of left displaced abomasum in dairy cows.

Objective: To evaluate aspartate transaminase (AST) activity and beta-hydroxybutyrate (BHB) concentration in blood obtained during the first or second postpartum (PP) week as tests for prediction of subsequent left displaced abomasum (LDA) diagnosis in dairy cows.

Animals: 36 cows with LDA tested at a mean 3 PP days, which was 7 to 22 days prior to LDA diagnosis (25, 75% quantiles), and 28 cows with LDA tested at 10 PP days, which was 5 to 18 days prior to LDA diagnosis, were matched to 3 controls per case by herd and calving date. Data were available from a large field study.

Use of test day milk fat and milk protein to detect subclinical ketosis in dairy cattle in Ontario.

Serum beta-hydroxybutyrate (BHB) levels were determined for 1333 dairy cows in various stages of lactation and parity on 93 dairy farms in Ontario. The data were collected in a cross-sectional manner, as part of the 1992 Ontario Dairy Monitoring and Analysis Program. The median serum BHB was 536 mumol/L for all cows, with a range of 0 to 5801 mumol/L.

Fat/protein ratio in first DHI test milk as test for displaced abomasum in dairy cows.

First DHI test milk that was sampled prior to displaced abomasum (DA) diagnosis was used to evaluate milk fat/protein ratio (FPR) for prediction of subsequent DA in dairy cows. Odds ratio, sensitivity, specificity, predictive values, and likelihood ratio were determined. Twenty-seven DA cases were matched to three controls per case by herd and calving date.

Extinction of within-event learning is contextually controlled and subject to renewal.

Five experiments examined within-event learning in rats by inducing an appetite for one of the elements (salt) of a compound stimulus and assessing preference for the other element (almond). Almond preference was conditional upon (1) the almond flavour having been presented in compound with the salt, and (2) the assessment being conducted when the rats were out of sodium balance (Experiment 1). Presentations of the compound in one environment (A) and of the salt and almond elements in a second environment (B) resulted in greater almond preference when rats were tested in A than in B (Experiment 2).

Fos expression in the spinal cord is suppressed in rats displaying conditioned hypoalgesia.

Two experiments used c-fos expression as a marker of spinal nociceptive processing to study the neural correlates of hypoalgesic responses to conditioned stimuli (CSs) paired with an aversive event. Immunoreactive (ir) neuronal labeling of Fos, the nuclear protein encoded by the c-fos gene, was examined in the spinal cords of rats killed 2 hr after injection of dilute formalin into a hind paw. Compared with control rats either not conditioned or conditioned in one environment but tested elsewhere, there were significantly fewer Fos-ir neurons in the spinal cords of rats displaying hypoalgesic responses when tested in the presence of aversive CSs.