Cattle Breeding

Performance testing
Performance test is a measure of the phenotypic value of the individual candidates for selection. Since the phenotypic value is determined by both genetic and environmental influences, the performance test is an estimate, not a measure of the genetic value. The occurrence of this estimate depends upon the heritability of the trait i.e. on the degree to which the genetic value is modified by the environmental influences.
Advantages
Among simple procedures, the performance test is the most accurate.
Environmental influences can be minimised by testing candidates for selection in the same pen or in similar environmental conditions.
The measure is direct, not on a relative basis.
All candidates for selection can be tested in contrast to progeny testing where only a parent can be tested.
Generation intervals are usually short.
Testing can usually be done on the farm under normal management conditions.
Disadvantages
Accuracy become low when heretability is low.
Phenotypes are not available for one s*xor in s*x limited traits such as milk yield.
Traits which are not expressed until maturity may become expensive or difficult to manage by performance tests since most selection decisions must be made before maturity.
Performance tests should be the backbone of most selection programmes. Although much publicity has been given to other selection methods, it remains a fact that most of the progress in livestock improvement to date has been due to selection on the individual's own phenotype i.e. performance test.
B. Pedegree selection
A pedegree is a record of an individual's ancestors including its parents. This information is valuable because each individual possesses a sample half of the genes from each parent. If we can precisely know an individual's phenotype, little is gained by considering pedegree in selection. Pedegree considerations are useful when we do not have sufficient accurate records of production of the individual. Also, it is useful in the early selection when the traits in question might not have expressed themselves. It is also useful for selection of males when the traits selected for are expressed only by the female such as milk production in dairy cattle.
Advantages
It provides information when performance tests are not available for the candidates.
It provides information to supplement performance test information.
It allows selection to be completed at a young age. Pedegree records may be used to select animals for performance or progeny testing in multi-stage selection scheme.
It allows selection of bulls can be selected on the milk records of their female relatives.
Disadvantages
Accuracy, relative to alternative selection procedures is usually low.
Too much emphasis on relatives, especially remote relatives, greatly reduces genetic progress.
Progeny of favoured parents are often environmentally favoured.
Relatives often make records under quite different environments, thus introducing non random bases into the selection system.
C. Progeny testing
In this method we evaluate the breeding value by a study of the expression of the trait in its offsprings. Individuality tells us what an animal seems to be, his pedegree tells us what he ought to be, but the performance of his progeny tells us what he is.
Progency testing is, of course, a two-stage selection system because some preliminary selection determines which animals first produce progeny followed by further culling of these which produce poor progeny.
Advantages of progney testing
a. High accuracy when many progeny are obtained.
Disadvantages progney testing
a. Long generation interval.
b. Requires high reproductive rate.
c. Low selection intensity.
D. Show ring selection
Selection on the basis of show ring performance has had considerable value in the past. Essentially this selection has been directed towards bringing the conformation of the animal to some ideal conformation.
This improvement has been based on two goals:
(i) improvement conformation, and
(ii) correlated response.
Improvement of conformation has economic value because a part of the sale price is determined by the conformation of the individual. The ideal type was chosen so that, in the opinion of the judges, the animal possessing this conformation was most likely to be a profitable producer. In other words, the judges were attempting to stress traits of conformation which are corrected with productive ability.
With the advent of record keeping it was found that direct selection for performance traits resulted in much faster progress than selection through correlated conformation traits. Also, when subjected to intensive study, many of the correlations between performance and show ring were found to be of non-genetic origin.
If the correlations are of genetic origin, direct selection for performance should improve conformation as well as the reverse situation. The show ring has been a good forum for discussion of what constitutes ideal type and good management and has produced dramatic changes in the conformation of some species.
This has resulted primarily from education of the breeders, however, for most animals which are presented in the ring are good and selection differential among these animals is usually so small as to produce little change.
Advantages of show ring selection
1. It enables breeders to exchange ideas and experience.
2. It allows comparisons among superior animals both within and between breeds.
3. It allows new breeders to make contact with established breeders.
Disadvantages of show ring selection
1. Emphasis is usually placed on traits of little economic importance.
2. Clever fitting and showmanship can mask defects of various kinds.
3. Differences between exhibited animals are usually small.
4. Conformation and production traits usually have low genetic correlations.

Use of Sex-Sorted S***m
Production of offspring of the desired s*x using s*x-sorted semen has become an established reliable technique in the dairy cattle breeding industry over the last two decades, where the major application is use of X-sorted semen on virgin heifers selected to produce the next generation of replacement animals. Although evolution of the technology has resulted in improved success, pregnancy rates are still somewhat lower than those achieved with conventional semen. Some of the reduction in pregnancy rate may be due to the lower concentration of s***m per dose (typically 2–4 million vs. 15–20 million in conventional, unsorted, semen straws). In superovulated cows, the use of s*x-sorted semen results in impaired fertilization rates and compromised yields of transferable embryos. Reduced fertilization with s*x-sorted semen may be due to low doses of s***m, an abnormal uterine environment due to supraphysiological concentrations of progesterone or atypical s***m transport in superovulated cows, damage to s***m during s*x sorting, or some combination of these factors. Thus, more research is required to optimize the yield of transferable embryos from s*x-sorted semen in superovulated donors.

The Ural catchment is rich in natural resources. The Sarmat tribes were already associated with husbandry and cattle breeding and they developed copper mines and melted iron ore. For thousands of years, various caravans passed through the Ural area. In 1640, at the mouth of the Ural, the town Guriev was founded as a commercial fishery. During that period dense forests fringed the rivers. In 1734 the Verhneuralsky pier was constructed in the upper Ural, from which boats and timber were floated downstream to Orenburg. Clear cutting and timber floating changed the morphology of the river. Further development of the Ural catchment was linked to rapid human occupation. Forest clear-cutting, claiming of land, and irrigation have modified the hydrological regime of the river. As a consequence, the Ural River bed started to gradually aggrade.

In the 20th century the construction of artificial water bodies and abstraction of water for industrial and public demands modified the seasonal flow regime. Today, seven reservoirs exist in the Ural catchment. Along the main Ural are the reservoirs Verhneuralskoe, Magnitogorskoe and Iriklinsky. The Aktyubinskoe reservoir is on the Ilek, the Verhne–Kumakskoe along the Bolshoy Kumak, the Kargalinskoye at Djaksy along the Kargala, and the Chernovskoye is on the Chernaya River. Water abstraction and surface retention lead to a 1.2–1.3 km3 reduction in the total annual flow. During dry years, annual flow reduction can be up to 2.2 km3 and, except during the spring flood, little water reaches the Caspian Sea during a dry year.

The Ural increasingly suffers from heavy pollution (in particular the Ilek), from siltation in the delta, and from water abstraction for industry and agriculture. Important industries include blackening and colours metallurgy, mining (leading to high metal concentrations of Fe, Cu and Zn), natural gas exploitation, large-scale crop production, and livestock-breeding. Large collective farming operations have historically contributed substantial loads of fertilizers and pesticides to the Ural. However, the near-natural flow regime in the middle and lower river limits human exploitation of vast floodplains, thereby creating landscapes of high conservation value. The floodplains along the lower river in Kazakhstan, as well as the northern shore areas of the Caspian Sea, have already been declared as protected zones.

Embryo Transfer
The feasibility of embryo transfer was demonstrated in 1890 in rabbits, but application to cattle breeding came much later, with the first calf born in 1951. In the 1960s and 1970s, nonsurgical methods were introduced for recovery and transfer of uterine-stage embryos, and cryopreservation of embryos followed soon after. Better understanding of follicular dynamics in cattle (1980s) permitted refinement of ovarian superstimulation programs.

In its simplest form, embryo transfer depends on induction of multiple ovulations by providing sufficient exogenous FSH to rescue subordinate follicles in a follicular cohort from atresia. Multiple follicles become functionally dominant and ovulate. The donor cow is then inseminated and fertilized embryos recovered from the uterus at 6 or 7 days after estrus. (In cattle, the zygote completes tubal transit in about 4 days.) These embryos are identified under a stereoscopic microscope, evaluated based on stage of development and morphology, and transferred to synchronous recipients.

At first, embryo transfer was simply used to multiply offspring from genetically valuable females. In dairy cattle, systematic use of ovarian superstimulation and embryo transfer in multiple ovulation and embryo transfer (MOET) herds also allowed generation of large full-sib or half-sib cohorts from young donors, permitting genetic evaluation of sisters rather than daughters of potential AI sires, thus generating reliable breeding values in much less time. This formed the basis of more rapid genetic progress and shorter generation intervals. Mastery of embryo transfer techniques is also important for establishing pregnancies in recipients using embryos created by in vitro embryo production methods or by cloning (somatic cell nuclear transfer).

There is some risk of disease transmission involving embryos, but health standards and embryo-handling procedures have been developed to allow safe commerce in embryos, domestically and internationally. Indeed, embryos can be transported internationally with less risk of disease or injury than transport of mature animals, and much more cheaply. Additionally, resulting calves are born to (recipient) dams with native immunity appropriate for their location and prosper more readily than adult animals translocated to a new environment. There is, however, an obvious imperative to ensure that recipient females are screened for, and clear of, vertically transmissible infectious diseases both at the time of transfer and throughout pregnancy. Biosecurity programs for recipient herds become just as important as the status of the genetically superior donor animals for all forms of assisted reproduction.

Embryo transfer has also been used to increase reproductive performance in some circumstances. For example, high-producing mature cows tend to have lower pregnancy rates when inseminated than when receiving donated embryos, suggesting that their own oocyte quality is reduced. This is especially marked during periods of heat stress, when use of donated embryos can reduce the detrimental impact of heat stress on normal fertility.

In vitro techniques can also be applied to oocytes recovered as part of a terminal procedure from donors with catastrophic injury or acute terminal illness. The number of viable oocytes may be increased if there is time for superstimulation, although ethical concerns must be addressed before undertaking exogenous hormone administration because of the added time delay. In the event of illness being the causative reason rather than catastrophic injury, there will most likely be a negative impact on oocyte viability and subsequent pregnancy numbers. Fever and conditions that give rise to severe systemic inflammation, as well as neoplasia (especially multicentric lymphosarcoma), appear to be associated with very poor results when terminal oocyte harvest is attempted.