Dual-pur­pose birds

NZ Lifestyle Block - - Your Poultry - Light Sus­sex

The light breeds tend to be egg lay­ers only and aren’t renowned for their eat­ing qual­i­ties, but many of the heavy breeds are known as dual-pur­pose breeds as they are good for both lay­ing and eat­ing.

For ex­am­ple, the orig­i­nal Light Sus­sex and Rhode Is­land Reds, or a cross of the two breeds, were de­vel­oped in the early 1900s as dual-pur­pose birds, and some strains were also ex­cel­lent lay­ers.

In the 1940s, lighter Leghorn hy­brids were de­vel­oped for the pro­duc­tion of ta­ble eggs as both in­ten­sive hous­ing and com­mer­cially-made feed be­came pop­u­lar. These birds were care­fully bred for their feed-to-egg con­ver­sion rate (eg, small­est amount of feed for the most eggs pos­si­ble), not for longevity, which is why com­mer­cial hy­brids don’t tend to be long-lived, but in their first 1-2 years are out­stand­ing lay­ers.

Some heavy breeds are very poor lay­ers, their ge­net­ics work­ing to lay down a great deal of mus­cle, like the Cor­nish

and In­dian Game breeds.

The cre­ation of the com­mer­cial layer and the broiler chicken has meant du­alpur­pose breeds have lost favour, un­able to com­pete against spe­cial­ist egg layer and meat birds se­lected for the ex­treme ends of pro­duc­tiv­ity, as has hap­pened with dairy and beef cat­tle breed­ing.

Se­lec­tion for growth and pro­duc­tiv­ity is of­ten the op­po­site to fer­til­ity so high egg pro­duc­ers are fer­tile and high meat pro­duc­ers are not-so-fer­tile.

Along with a dif­fer­ence in body size, there is a big dif­fer­ence in me­tab­o­lism and the nu­tri­tional re­quire­ments for these birds to func­tion at their most ef­fi­cient. Knowl­edge of the nu­tri­tional needs of poul­try has come a long way in the last 100 or so years, and more rapidly in the last 50 years. There is a greater un­der­stand­ing of the nu­tri­ent re­quire­ments of the birds, and the abil­ity to an­a­lyse the make-up of food­stuffs and to test each sea­sonal batch of in­gre­di­ents for pro­tein and energy lev­els. This has meant nu­tri­tion­ists can for­mu­late di­ets to suit both the age and type of stock (eg the ef­fi­cient diet of the egg layer vs the higher pro­tein diet of the meat pro­ducer).

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