3.6 Breeding goals consists of several traits

The breeding goal for food production aims, irrespectively of the species, at: improving gross efficiency (amount of product divided by the amount of feed consumed) en reducing the cost price by: 1) improving productivity (higher yield and financial returns, 2) improving feed conversion (less feed per kg of product and less costs) and 3) improving reproduction, health and survival (less replacement animals needed and less costs). Increasing attention to improve welfare and to reduce environmental impact might be additional breeding goal traits.

Nowadays, in commercial breeding programs for dairy cattle, pigs and poultry sophisticated breeding programs with complex breeding goals are in place. For other species breeding programs are less complicated with a limited number of breeding goal traits. E.g. globally in small ruminants kept for meat production (sheep and goat) with less complex breeding programmes growth appears to have the greatest importance in the breeding objective. In commercial pig and poultry breeding special lines with different breeding objectives are developed that are crossed to obtain the final egg or meat producing animal with the optimal combination of objectives selected for in the different lines. Due to a limited number of breeding goal traits in a specialized line, a lot of progress can be made in each line. By crossing the lines, the breeding goals, for which a high level is reached in each line, are combined. His proved to be more profitable than selection for all important breeding goal traits in one line or one breed.

A simplified example of the use of special lines is a three-way cross often applied in in pig breeding: first, sows of a line selected for number of piglets is crossed with a boar of a line selected for growth. Second, crossbred sows are subsequently crossed with boars of a line selected for carcass quality. The result is a lot of piglets born with a good growth and carcass quality. Around 1970 in a sheep breeding trial, ewes from the Finnish Landrace breed (a breed with a high litter size) were mated to a ram of the Ile de France breed (a breed that can be bred irrespective of the season). This resulted in crossbred ewes with a high number of lambs due to three lambing’s in two years’ time. The sire of the lambs was a ram of the Texel breed famous for growth and slaughter quality.