Genetic Characteristics Required in Dairy and Beef Cattle for Temperate Grazing Systems

Genetic Characteristics Required in Dairy and Beef Cattle for Temperate Grazing Systems

Key points

1. Only about 10% of the world’s milk is produced from grazing systems. Consequently the majority of dairy cattle have not been selected under grazing, nor on seasonal systems. This is not true for beef cattle, for which the majority, especially the dams, are managed under seasonal grazing systems.

2. In grazing systems daily feed intake is limited to lower levels than are achievable on concentrate plus conserved forage rations. Consequently, cows most suited to grazing environments are likely to have a lower genetic potential for milk production than cows selected in high concentrate systems, to minimise their relative energy deficit.

3. The traits required under grazing will include those for other systems; high yields of milk with high milk solids, efficient converters of feed to product, functionality, good fertility, health and longevity. Successful grazing systems require dairy cows that are adapted to achieving large intakes of forage relative to their potential milk yields, and therefore able to meet production potential exclusively from forage. Grazing cattle must also be able to walk long distances, and in seasonal systems, must be able to conceive and calve once every year. The ability to be productive when milked once daily may also be desirable in low cost grazing systems in the future.

4. Intensive selection for milk production within the Holstein-Friesian breed on high concentrate diets has generally resulted in a genotype that is not well suited to grazing (high forage) systems, in which these cows exist in permanent energy deficit. This unsuitability is particularly true for seasonal systems, for which good fertility is an essential trait.

5. There is now strong evidence for the existence of interactions between genotype of dairy cattle and feeding system, where the genetics and the systems differ widely. Therefore mutual compatibility between the cow and the system must be optimised for production and profit.

6. The New Zealand Friesian and New Zealand Jersey, and crosses between them, or with other dairy breeds, including the North American Holstein-Friesian, have been shown to be well suited to grazing systems. Increasing evidence suggests that genetics from some Scandinavian breeding programs, e.g. the Norwegian Red, may also be suited to grazing systems, where good fertility is essential.

7. Developments in international sire evaluation (adaptations of multiple across country evaluation (MACE)) that enable differences in management systems to be taken into account will provide different breeding values for different conditions. Until then, sires should be proven in the same general management conditions in which the daughters are to be managed.

8. There is little evidence of important G x E interactions in beef cattle, for growth rate, food intake or carcass traits.

9. But beef cows from large, late maturing breeds are relatively more restricted by inadequate nutrition than smaller early maturing types. As a result both their fertility and milk production can be impaired leading to a lower weaning percentage and lighter weaning weight.

10. Interactions between the effects of genotype and nutrition on carcass composition can occur where the level of energy intake is above the muscle deposition capacity of some breeds.