Selective Breeding by Farmers

Selective Breeding

For centuries farmers have controlled the mating of their animals to improve their stock.

Today new breeds are still being created.

Wild animals evolve through natural selection — the ability of the fittest to survive. The spectacular success of some species — the fox, for example — lies in their ability to adapt to new environments as their traditional habitats are altered or destroyed.

Domestic animals have evolved in an entirely different way. They have been subject to artificial selection by man for the last 10,000 years. The rate of change within a population is determined mainly by the intensity of the selection pressures: as the owners of livestock have understood more clearly the principles of genetics, their selection programmes have become more efficient and their livestock have changed, and often improved, more rapidly.

Early days

Ancient records show that deliberate selection of livestock was practised as early as the third millenium BC. In southern Mesopotamia the inventory of an estate near Lagash included a bull which was imported from the upland kingdom of Elam to prevent deterioration of the herd in the sultry climate of the plain.

In the British Isles the opportunities for livestock improvement were limited as long as many types of animals roamed together on the common land. The only method of selection that could be practised was castration. However, as soon as the enclosures took place the movement of animals could be controlled and matings could be planned. The improvement of livestock in the British Isles by deliberate selection thus started effectively in the early 18th century. Records show, for example, that in 1710 a famous breeder, Webster of Canley, purchased two Longhorn cows of the superior Westmorland and Lancashire variety for his farm in Warwickshire.

British breeders

The first breeder to be noted nationally as an improver of livestock was Robert Bakewell of Dishley Grange in Leicestershire. His work received wide publicity, but his success rested heavily on the improvements achieved by earlier breeders, such as Webster of Canley. Bakewell started his programme around 1750 with Shire horses, Leicester sheep and Longhorn cattle.

His incentive to improve the Longhorn was the change in market demand with the Industrial Revolution and a growing need for beef animals. The original Longhorn had a thick hide, long horns, long hair, coarse shoulders and heavy bones, and reached maturity very slowly. Bakewell selected animals that approached most closely his hypothetical ideal, and then he mated the best males and females of succeeding generations, so transforming the Longhorn into a smaller, finer-boned animal which had more meat on the valuable hindquarters and which matured earlier. In this process the breed lost much of its hardiness, its milk yield was reduced, and it retained its horns. Long horns became a severe disadvantage when cattle were housed in a confined area, and the Longhorn was eventually superseded by other breeds. Today it is a rare breed.

Bakewell’s policy of breeding ‘best to best’ inevitably led him back to the same female families and bull lines within the Longhorn breed. The result was inbreeding — the mating of closely related animals. Inbreeding can be a useful aid to the animal breeder: it can concentrate the qualities of outstanding animals in their descendants, and it usually leads to greater uniformity within a population. On the other hand, it can also lead to reduced vigour and viability, and poor performance, and it is more likely to expose any undesirable recessive characteristics lurking in the genotype of the breed, which may produce deformed animals. However, most successful breeders who were improving their livestock in the 18th and 19th centuries used inbreeding as an integral part of their programmes.

These improvement programmes changed many British cattle from triple-purpose to specialist animals. Previously they had been large, powerful animals used for pulling carts and ploughs, producing milk as a by-product, and meat only when their working life was ended. They became changed into smoother, softer, finer animals, designed for either milk or meat production. The capacious udder or well-fleshed hindquarters were preferred to powerful forequarters.

While the Longhorn is now rare, the Hereford has become the most popular beef breed in the British Isles, although its early history and development were very similar. Members of the Tompkins family were the first noted improvers of the breed in the late 18th century, and their herd was based on an outstanding cow called Silver. In the early 19th century the breed was dominated equally strongly by the Hewer family and their bull, Sir David; the influence of these two families resulted in a high level of inbreeding in Hereford cattle. Bakewell and Tomkins both wanted to change the conformation of their animals, while Hewer’s main objective was to establish a standard recognisable colour. The red, white-faced Hereford cattle seen in many pastures today both in the British Isles and throughout the world confirm his success.

Perhaps the most successful breeders of that era were the Collings brothers, Charles and Robert of Darlington in County Durham. They used to extremes the application of inbreeding in livestock improvement. They wanted more productive cattle, and they selected for medium size, early maturity, flesh production, utility and beauty of form. They carefully identified the outstanding animals and mated their descendants closely. The famous ‘Durham Ox’ and the ‘White Heifer that Travelled’ were both exhibited around the country and attracted great interest in their work.

Sheep

The Norfolk Horn sheep originally inhabited the exposed, infertile Breckland of East Anglia. It was noted for its hardiness, robustness, freedom from disease, long legs and activity, and the ewes were prolific and good mothers. It was not a very productive breed, but it lived where other breeds would have died. As land was enclosed and improved, the Norfolk Horn’s hardiness and thriftiness became less important, and its mobility and independence became a disadvantage. The breed did not possess the genes necessary to enable it to adapt to the new conditions, but around 1800 it was crossed with Southdown rams which imparted qualities of early maturity, compactness of form and a more placid temperament. Eventually the fusion of these two breeds led to an entirely new breed, the Suffolk, which today is one of the most popular international breeds of sheep. It has retained the leanness and some of the prolificacy of the Norfolk Horn, but added to it the earlier maturity and better shape of the Southdown.

The future

Each breeder has his own aims, and the success of his programme depends on three factors: the validity of his original objectives, the correctness of the matings and the efficiency of his selection procedures. The lessons learned by the earlier breeders of livestock were employed by farming consultant Lawrence Alderson to create a new breed of sheep — the British Milksheep.

Successful breeding in the future will depend largely on breeders being able to maintain the recognisable characteristics of individual breeds, such as their colour, shape, flesh production and so on; at the same time it is important to ensure that there is a sufficiently varied pool of genes available to draw on as the environment, fashions and requirements change. Each breed is suited to specific circumstances and farming systems.

Once more the hardy qualities of some of the ancient breeds (for example, the North Ronaldsay or Soay sheep, or the White Park cattle) are being appreciated by those farmers who are looking for animals that are independent and easy to manage in upland areas. Great efforts are now being made to see that they and other minor breeds in this country do not become extinct. At the same time, farmers with lush, lowland pastures are looking for breeds with high output and high turnover, such as the new British Milksheep, which make efficient use of the land and so enable food to be produced more cheaply than when less productive breeds are used. There is always more research to be done.

27. July 2011 by admin
Categories: Farm Animals, Farming, Livestock | Tags: | Comments Off on Selective Breeding by Farmers

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