Infertility problems in cattle practice

Extract

For the cow the simplest definition one could give for fertility is that she regularly delivers a live virile calf on approximately the same day each year.     

Polioencephalomalacia in range cattle.

Polioencephalomalacia developed in 27 of 225 cattle grazing on 486 hectares of dry, short, grama grass pasture. Chemicals in drinking water, toxin from nitrate-utilizing ruminal bacteria, and documented poisonous plants were considered as etiologic agents. Attempts to reproduce the disease by injecting mice and dosing sheep with broth filtrate from nitrate-utilizing ruminal bacteria were not successful. Mushrooms collected from the pasture and fed to a cow did not reproduce the disease.     

Factors influencing time of parturition in range beef cattle

A total of 2434 calving records from seven calving seasons were analyzed by the least-squares and chi-square procedures to study the influences of breeding group, age of dam, sex and birth weight of calf and dam weight at calving on the time of day of parturition. Frequency of day calving (0630 ± 030 to 1900 h) was slightly but not significantly higher than night calving (1900 h to 630 ± 030). The frequency of night calving was higher among heifers compared with the older cows. The cows which calved after May 15 (the last one third period of pregnancy) had higher frequency of day calving compared with those that calved earlier. The frequency of daytime calving was higher among the cows that weighed at most one standard deviation below the average compared to heavier cows of comparable age.     

Thermal balance of cattle grazing winter range: model application

Beef cattle grazing semiarid foothill rangeland of the Northern Rockies during winter may be exposed to cold temperatures and high winds while grazing pastures with low nutritional value. Cattle can physiologically and behaviorally respond to the changing environment to lower their metabolic requirements and reduce the effects of cold exposure. Requirements of grazing cattle may be overpredicted with models developed in controlled settings that do not account for energy-conserving behaviors. We refined a simple thermal balance equation to model heat exchange of free-ranging cattle. We accounted for the complex interactions between animal behavior and the changing natural environment by applying the insulation characteristics of the cattle's tissue and coat to a simple geometric shape of an asymmetric ellipsoid at different orientations to the sun and wind. We compared the model predictions with heat production measured in 3 studies, and in all cases the model predictions were similar to those reported. Model simulations indicate behaviors, such as lying and orientation to the sun, mitigated the effects of extreme weather. For many combinations of winter weather variables, metabolic requirements increased only slightly due to cold exposure of mature beef cattle in a near-maintenance state. The results indicate that solar radiation contributes strongly to the thermal balance of a cow. Thus, previous models that do not account for the irradiative environment may overestimate metabolic requirements of cattle acclimated to grazing winter range.     

Polioencephalomalacia and photosensitization associated with Kochia scoparia consumption in range cattle.

Cattle consuming only Kochia scoparia in a pasture southeastern Colorado became ill. Clinical signs were lacrimation, depression, anorexia, nystagmus, head pressing, and recumbency. Some cattle died acutely, with the only clinical signs being recumbency, nystagmus, and occasionally opisthotonos. Pathologic findings were pulmonary edema and congestion, hepatic necrosis and fibrosis, necrosis of proximal convoluted tubular epithelium in the kidneys, epidermal necrosis of lightly pigmented areas, and laminar cerebrocortical necrosis. When the cattle were removed from the pasture, the problem ceased.     

Investigation of bovine viral diarrhea virus infections in a range beef cattle herd

Bovine viral diarrhea virus (BVDV) infections resulting in clinical disease developed in calves, despite vaccination of dams and high maternal BVDV antibody titers in calves. Eight persistently infected (PI) calves born to immunocompetent dams were identified in the herd. Neutralizing BVDV antibody titers of PI calves had decreased greatly by the time the calves were 1 to 2 months old. Antibody titers of PI calves decreased more rapidly than antibody titers of calves that were not PI. Reduced antibody titers in PI calves allowed detection of BVDV in serum specimens of all PI calves by the time they were 8 weeks old. Persistent infection in suspect calves was detectable serologically and was confirmed by virologic examination of serum specimens 4 months after weaning, when the calves were 9 months old. Growth rates were reduced in viremic calves.