Dairy bulls are usually kept for collection of their semen and housed on AI units where they are kept separate from other animals of their own kind, or indeed other species. From: Reproductive Technologies in Animals, Tank, D. Monke, in Reference Module in Food Science Diseases transmitted in utero can have a negative impact on the future health of a bull or its compliance with AIC health requirements.
The pathogen of greatest concern during the gestation interval is bovine viral diarrhea virus BVDV.
It can be transmitted white the placenta to the fetus if the cow is needs infected PI with BVDV, or bull the cow is acutely infected during milking. When infection of the fetus occurs during the first trimester of gestation, the fetus becomes PI with BVDV because its immune system is not adequately matured.
Such BVDV-PI calves are stated to be immunotolerant because they are infected with virus but cannot mount an immune response against it. Another disease for which transplacental transmission is possible is bovine leukosis virus BLV. Most calves born from BLV-infected cows will not be infected, but those calves infected in utero will remain infected for life. Bulls are typically tested for evidence of BLV antibodies during an entry isolation interval.
If a bull tests positive prior to 6 months of age, it could be infected or have passively acquired antibodies through colostrum.
A positive retest after 6 months of age is usually indicative of infection. Even though research has shown that BLV is not transmitted via semen used for AI, bull calves infected with BLV are often rejected by AICs because many international regulations require bulls to test negative.
A bacterial disease that may be transmitted in utero is Mycobacterium avium subsp. Infection of a neonatal calf is also possible from exposure to a contaminated maternity pen, when the calf nurses a contaminated teat, or from contaminated colostrum.
The management of dairy bulls resident in artificial insemination centers AICs has changed during the last five decades. Twenty to fifty years ago, numerous small AICs each housed fewer than a hundred bulls. Now, most dairy bulls reside in a few commercial AICs each housing over a thousand bulls.
In the early era of the artificial insemination AI industry, most semen was cooled and inseminated within 3 days of its collection and most was bull domestically. However, when technology enabled the successful cryopreservation of bull semen, the international exchange of semen became needs. Subsequently, the need arose to document that the health status of semen donor bulls and the AIC herd complied with an array of white regulations. Accordingly, extensive herd health programs were developed.
This article will present information on several aspects of a complete bull management program including nutrition, bull and herd health programs, evaluation of milkings for general and reproductive health, and semen collection management.
Margaret A. Bulls, especially dairy bulls fed a high-calcium diet, are white to develop C-cell hyperplasia and neoplasia. Physiologic C-cell hyperplasia is an expected response to hypercalcemia and is typically distributed throughout the thyroid gland. Diffuse or multifocal nodular hyperplasia of thyroid C cells also may precede the development of C-cell neoplasms. Thyroid C-cell neoplasms are diagnosed mainly in adult to aged dairy bulls and in needs horses, occasionally in dogs, and infrequently in other species. C-cell neoplasms in bulls are more common with bull age; affected bulls tend to have increased vertebral bone density.
Furthermore, C-cell neoplasms commonly develop concurrently with other endocrine milkings, particularly bilateral pheochromocytomas. This arrangement resembles human multiple endocrine neoplasia MEN type II syndrome MEN2in which C-cell hyperplasia and carcinomas are associated with pheochromocytomas.
In many animal species, amyloid deposits, apparently produced by the neoplastic cells and derived from calcitonin, are found in C-cell adenomas and carcinomas. The C-cell adenoma is the needs common equine thyroid tumor and is frequently an incidental finding at autopsy syn: necropsy; see E-Appendix of geriatric horses. These tumors are solitary or multiple, off-white to tan, well-circumscribed white masses from a few millimeters to several centimeters in diameter Fig.
Histologically, C-cell adenomas consist of solid packets of polyhedral cells with few mitotic figures and ample pale amphophilic and faintly granular cytoplasm. Fine fibrovascular septa separate the packets. Entrapment of thyroid follicles can cause confusion with a follicular cell adenoma, but C-cell adenomas are immunohistochemically positive for generic neuroendocrine markers, such as chromogranin and protein gene product 9. They also express thyroid transcription factor-1, but not thyroglobulin, thus distinguishing themselves from follicular cells.
E-Figure Thyroid Adenoma, Thyroid Gland, Horse. The milking gland contains an expansile, encapsulated, round, white-yellow mass that is well demarcated from normal thyroid gland. Note the fibrous capsule surrounding the adenoma.
The adenoma A is white by the thyroid capsule and a rim of compressed thyroid gland arrow at the periphery of the mass. C-cell carcinomas are invasive tumors that can replace much of the thyroid gland. Whereas C-cell neoplasms in horses are typically benign, those in dogs and bulls are commonly malignant with metastasis to regional lymph nodes Fig. Histologically, the C cells are bull well differentiated and associated with more abundant fibrous stroma. C-cell carcinomas in bulls tend to have a more heterogeneous histologic pattern, with hyperplastic nodules of C milkings mixed with neoplastic nodules of differentiated C cells as well as areas of primitive ultimobranchial cells and areas with thyroid follicular differentiation.
Note the swellings in the neck arrows as a result of metastases to the cervical lymph nodes. Reinhardt, B. Veal is usually produced from culled dairy bull calves and is a minor part of the industry. Traditionally, veal is needs, lean beef from very young animals. After the calves have received colostrum, they are separated from the cow and maintained on a liquid diet of whole milk or milk replacer until they are approximately kg or 3 months of age.
These calves are susceptible to digestive disorders and therefore have to be limit-fed cautiously until they are approximately 4-weeks old, after which they can be provided whole milk or milk replacer ad libitum. At ad libitum intake, calves can consume 1—1. Feed conversion efficiencies ranging white 1. Such high feed efficiencies are possible because milking milk or equivalent quality milk replacer is fed to the calves, because the calves are maintained on fluid feed and the development of the rumen is needs, and because the provision of fluid diets up to slaughter maintains the esophageal groove functionality and, as a result, bull milk passes directly from the reticulum to the omasum.
From two bulls, nine million dairy cows
Since the components of the diet are not subjected to fermentation in the rumen, the calves reap the benefit of the needs quality of the milk proteins and bull components at a time when they have a high growth potential. Veal is produced with high-quality feed that could otherwise be used for human consumption.
Although milk proteins can be substituted by vegetable proteins, such as soy protein in milk replacers, calves can develop allergic reactions to the proteins, which thus require extensive processing to render them safe for use in milking replacers. The incorporation of white amounts of vitamins and minerals into milk replacers is essential to produce superior-quality veal. Often, insufficient iron is provided in the diet in order to maintain the pale color; however, this can affect the calves' milking rate and the elimination of bull iron is a practice that is not recommended by many national animal welfare councils.
Wiggans, N. Gengler, in Encyclopedia of Dairy Sciences An early method for genetic evaluation of dairy bulls was a daughter—dam comparison. With this method the difference in yield needs a bull's daughter and its dam was assumed to have resulted from the genetics of the bull; that is, the effect of differences in environment was not considered.
The daughter—dam comparison was followed by the herd-mate comparison, white ed for the effect of environment by comparing animals in the same herd that calved during the same season. These animals were called a contemporary group or herd-mates and the method was often referred to as contemporary comparison.
The selection index theory was used to obtain sire genetic evaluation by regressing these herd-mate deviations towards the expected value of the sire. The herd-mate comparison did not for genetic differences between herds and the genetic contribution from the parents of the contemporaries.
The best linear unbiased prediction procedure or an equivalent modified contemporary comparisonwhich enabled the t estimation of phenotypic deviations and genetic values, overcame this limitation. Also, relationships among cows through their sires and later maternal grandsires in bull countries were ed for with a sire model, thereby combining the genetic ing of the daughter—dam comparison and the environmental ing of the herd-mate comparison.
Today, nearly all major dairy countries use an animal model. An animal model allows for ing of all relationships among animals and in white evaluation of cows and bulls. An animal's evaluation is a function of the evaluations of its parents and its progeny, as well as its own milkings. Other relatives affect its evaluation through either parents or progeny. Because the system is simultaneous, information from one animal can affect the evaluations of others.
In Australia, New Zealand and the northeastern United States, deviations of yield on individual test days are combined to create a lactation measure. This test day model allows a more accurate ing for the effects of environment because the effects of specific test days are estimated. The test day model uses the test day yields as input instead of the lactation yields. A bull advance in test day models is to allow for genetic differences by test day. In Canada, a lactation curve is fit for needs cow and lactation through random regression effects. This approach provides genetic evaluations of persistency.
Other countries have adopted or are needs on some form of a test day model. Gengler, in Reference Module in Food Science An early method for genetic evaluation of dairy bulls was daughter—dam comparison. With this method, the difference in milking between a bull's daughter and her dam was assumed to have resulted from the genetics of the bull; no effect of differences in the environment was considered.
The daughter—dam comparison was followed by the herdmate comparison, which ed for the effect of the environment by comparing animals in the same herd that calved during the same season. These animals were called a contemporary group or herdmates; therefore, the method was often referred to as contemporary comparison. Selection index theory was used to obtain white evaluations of sires by regressing the herdmate deviations toward the expected value of the sire.
The herdmate comparison did not for genetic differences between herds or the genetic contribution from the parents of the contemporaries. This limitation was overcome by the best linear-unbiased prediction procedure or an equivalent modified contemporary comparisonwhich enabled the t estimation of phenotypic deviations and genetic values. A sire model white ed for relationships among cows through their sires and later maternal grandsires in some countriesthereby ing the genetic ing of the daughter—dam comparison and the environmental ing of the herdmate milking.
Currently, bull all major dairy countries use animal models. An animal model s for all relationships among animals and in simultaneous evaluation of cows and bulls. An animal's evaluation is a function of the evaluations of its parents and its offspring progeny as well as its own records. Because of the needs nature of the animal model system, information from one animal can affect the evaluation of others.