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Proper performance monitoring of cows on pasture-based diets is crucial to inform nutritional recommendations that minimize undesirable effects of high ruminant CH4 emissions into the environment. The prediction of linkages between rumination patterns, methane emissions, and correlated production traits of cows in a pasture-based automatic milking system was tested. A previous 10-d baseline measurement of rumination activity by acoustic methodology of 156 Holstein-Friesian cows was used for frequency analysis of rumination time and identification of 2 treatment groups (n = 37 cows/group) represented by cows with consistently high (HR; 75th rumination percentile = 617.55 ± 81.37 min/d) or low (LR; 25th rumination percentile = 356.65 ± 72.67 min/d) rumination. The HR and LR cows were paired by nearest parity, days in milk, body weight (BW), and previous 10-d milk production, and within pairs randomly assigned to 1 of 2 experimental groups managed on a voluntary milking system with diets consisting of at least 75% pasture, plus concentrates. Animal traits, including rumination time, mass flux of CH4 (QCH4) and carbon dioxide (QCO2), milk production, and estimated dry matter intake according to individual QCO2 fluxes over a 22-d period were analyzed with repeated measure mixed models for a completely randomized design, structural equation modeling, and nonlinear regression. High rumination and methane was seen in older and heavier cows that had greater estimated dry matter intake and milk production. A consistent difference in rumination time and QCH4 across days was detected between HR and LR, even after adjustment for metabolic BW. Estimated dry matter intake had direct positive effects on rumination and QCH4, but no independent direct effect of rumination on QCH4 was detected. The LR cows produced more QCH4/milk, associated with lower milk, BW, concentrate intake, and greater activity at pasture. A typical dilution of maintenance effect on QCH4/milk was detected as a consequence of increasing milk yield and similar significant reduction of QCO2/milk. The results raise challenging questions regarding the rumination patterning of grazing dairy cows and alternatives to reduce ruminant methane emissions in grazing dairy cows., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Objectives: To investigate the accuracy of both the optical and digital Brix refractometers compared with radial immunodiffusion (RID) for determining the immunoglobulin G (IgG) concentrations in dairy calf serum., Design: The experiment design was a cross-sectional survey of four dairy farms. Serum was sampled from 12 calves from each farm at approximately 48 hours of age., Methods: Serum IgG concentrations of 48 calves were measured using RID and both types of Brix refractometer., Results: IgG concentrations measured by Brix refractometer scores correlated with RID results: 0.74 and 0.71 for the digital and optical devices, respectively. The minimum Brix score that identified calf serum with success of passive immunity (>1000 mg/dL RID IgG) with 100% accuracy was 10% for both devices. The optical and digital devices performed similarly at identifying IgG concentrations in calf serum, with a concordance of 87%., Conclusion: Brix refractometer score ≥10% can be used to classify calves with successful transfer of passive immunity and the devices are sufficiently accurate for use as a simple, inexpensive on-farm tool for the monitoring of neonatal dairy calf immunity levels., (© 2015 Australian Veterinary Association.)

Objectives To examine the prevalence of Theileria orientalis in the Gloucester area of New South Wales and its effect on individual animals. Methods Blood samples (EDTA and clotted blood) were collected from a total of 55 calves and their dams from 6 properties over a 16-week period. A total of 202 and 190 blood samples were collected from the calves and dams, respectively, and were examined via blood film for the presence of intraerythrocytic T. orientalis piroplasms. Packed cell volume (PCV) was measured to determine infection resulting in anaemia. The presence of antibodies against the T. orientalis major piroplasm surface protein (MPSP) was tested using ELISA. Results The overall prevalence of T. orientalis infection in both dams and calves from all herds examined was 95%. Mean peak parasitaemia was observed in calves between 6 and 9 weeks of age (P = 0.051), coinciding with a decline in mean PCV. Only 3 (6%) of the blood samples collected from the dams were positive for Theileria-associated antibodies and no significant relationship (P > 0.05) was found between the presence of antibodies in the dams and PCV levels in the calves. There was no evidence that passive transfer of antibodies from dams to calves protected the calves against a decline in PCV. Conclusion This study confirmed a high prevalence of low-level Theileria infection, but low MPSP seroconversion rates, in dams and calves in an area where the disease has been endemic for a number of years. [ABSTRACT FROM AUTHOR]