New Zealand Rare Breeds Website: www.rarebreeds.co.nz – Information
» Home » Breeds » Directory » About » News » Webmart » Projects » Gene Bank » Links » Join » Contact
 
 

Grading Up Programmes

      The terms “grading up” and “breeding up” are often used synonymously and interchangeably in the livestock world, and this generally does not matter, although they do refer to somewhat different processes.

      The former is aimed at increasing the number of animals of a particular breed by a carefully controlled system of cross-breeding. It is resorted to where a breed has become so low in numbers that it is at risk of becoming extinct. The cross-bred progeny produced during this process are known as ‘grade’ animals.

      Breeding up strictly refers to the system used to increase or fix a single desired feature of a breed, for example, colour or coat-type. It may involve cross-breeding or simply selected matings within a breed. Both processes involve the orderly manipulation of the genetic makeup of the animals that are the end result.

Jersey cow with Grade 1 Dexter heifer calf 
(Jeanette McIsaac photo)
Jersey cow with Dexter Grade 1 heifer calf
(Jeanette McIsaac photo)

Grading Up – Dexter Cattle

      The New Zealand Dexter Cattle Society has carried out a grading up scheme since its inception in 1993. This requires a purebred Dexter bull (or semen for AI) plus one or more suitable base or “foundation” cows of another breed. Ideally, these base cows will be of breed that reflects some of the characteristics of Dexters – that is, they are relatively small in size and of a solid colour. Suggested suitable breeds include Angus, Red Poll, and Jersey. (Most unsuitable are large, broken-coloured breeds such as the Friesian.)

      The purebred Dexter bull is mated to these cows. Any resulting bull calves are discarded from the breeding programme, but the heifers are retained. These females are genetically 50% Dexter and 50% of the base breed; they are known as Grade One or G1 Dexters. These are in turn mated to a purebred Dexter bull and the heifer calves are retained as Grade Two Dexters which are statistically 75% Dexter and 25% base breed.

      By repeating the above process two more times an animal is obtained which at Grade Four is almost 94% Dexter. At this level heifers can be admitted to the Herd Book as “purebreds”. Bulls, however have to be taken to Grade Five (nearly 97%) before being considered purebred.

      The scheme has been so successful that by October 2005 there were more than 3000 Dexters registered in New Zealand, and from 30 June 2007 Grade One animals will no longer be registered by the Society.

      It is important to note that this kind of grading up, which initially introduces a large quantity of genes from another breed, should be used only where numbers of a rare breed have fallen so low that the breed is seriously at risk of being lost.

Other types of Breeding Up

      Other types of grading or breeding up do not involve an initial cross-breeding at such an extreme level. Two examples of such currently being undertaken in New Zealand involve Galloway cattle and Alpacas.

      In the former, the rare White Galloway colouring is being bred for by mating standard black Galloway cows to a purebred White Galloway bull and then continuing using the mating system described above. In this case, however, white animals can be obtained by the second cross and these are immediately eligible for Herd Book registration.

      In the Alpaca world, a current breeding up programme involves the rather rare long-coated Suri Alpaca. Numbers of this desirable strain are being increased by crossing them with the more common Huacaya Alpacas. Because the long coat of the Suri is produced by a dominant gene, the resulting offspring are all long-coated (although 50% Huacaya genetically). From these animals, however, it is a relatively simple task by controlled breeding over several generations to produce animals which are almost 100% Suri. Besides increasing the number of Suri Alpacas, variations in colour are also being introduced.

      In all grading or breeding up programmes the secret of success is an initial understanding of the genetics involved together with a planned and controlled breeding programme.

Against Grading Up

      World wide, there has been some strong criticism of grading up programmes, mostly (though not entirely) because the increased population is obtained at the cost of loss of genetic purity. And it is interesting to note that many Dexter breeders in New Zealand proudly use the term “fullblood” to refer to animals that have no grading up in their ancestry – though this usage is frowned upon by the New Zealand Dexter Cattle Society.

© Copyright 
 » Go to Rare Breeds Home Page 
See also Navigation Bar at top of this page

Rare Breeds Conservation Society of New Zealand Incorporated

XHTML and CSS Valid icons

2002-2006