Publications

Genetic and economic efficiency of alternative schemes breeding for resistance to gastrointestinal (GI) helminths in meat sheep was evaluated using deterministic simulation. Four breeding objectives and schemes were assessed. The first breeding objective simulated a situation where the flock size cannot be increased due to non-feed related constraints (FLOCK). The second specifically assumed that the flock size is restricted due to limited amount of feed resources (FEED). The third and fourth objectives assumed that sheep performed only tangible roles (TR) and both tangible and intangible roles (IR) in the production system, respectively. Within these breeding objectives, four breeding schemes that differed in the measures available for use as selection criteria were compared. The schemes ranged from one that utilised birth weight, weaning weight, yearling weight, litter size and lambing interval (scheme 1) to one that included two measurements of faecal egg count (FEC, eggs/g) in young rams immediately after weaning (scheme 4). For scheme 1, resistance to GI helminths was not included in the breeding objectives. A two-stage selection process was assumed in the selection of rams to be used in the nucleus. The annual monetary genetic gain and profit per ewe for all schemes varied within breeding objectives but were highest in TR. Within each breeding objective, the annual monetary genetic gain and profit per ewe was highest for the breeding scheme with the highest level of recording (scheme 4). In all objectives, the difference in the profit per ewe between a scheme that included records on FEC measured once in rams immediately after weaning (scheme 3) and scheme 4 was small (1.3–3.7%) indicating that there is little benefit taking a second measurement of FEC. The optimal size of the nucleus was determined by the breeding objective. In schemes 3 and 4, profit per ewe was optimal when the top 5%, 5%, 10% and 10% of rams were selected in the first selection stage for FEC measurement in FLOCK, FEED, TR and IR, respectively. The practical implications of these results are discussed.

Genetic and economic efficiency of alternative schemes breeding for resistance to gastrointestinal (GI) helminths in meat sheep was evaluated using deterministic simulation. Four breeding objectives and schemes were assessed. The first breeding objective simulated a situation where the flock size cannot be increased due to non-feed related constraints (FLOCK). The second specifically assumed that the flock size is restricted due to limited amount of feed resources (FEED). The third and fourth objectives assumed that sheep performed only tangible roles (TR) and both tangible and intangible roles (IR) in the production system, respectively. Within these breeding objectives, four breeding schemes that differed in the measures available for use as selection criteria were compared. The schemes ranged from one that utilised birth weight, weaning weight, yearling weight, litter size and lambing interval (scheme 1) to one that included two measurements of faecal egg count (FEC, eggs/g) in young rams immediately after weaning (scheme 4). For scheme 1, resistance to GI helminths was not included in the breeding objectives. A two-stage selection process was assumed in the selection of rams to be used in the nucleus. The annual monetary genetic gain and profit per ewe for all schemes varied within breeding objectives but were highest in TR. Within each breeding objective, the annual monetary genetic gain and profit per ewe was highest for the breeding scheme with the highest level of recording (scheme 4). In all objectives, the difference in the profit per ewe between a scheme that included records on FEC measured once in rams immediately after weaning (scheme 3) and scheme 4 was small (1.3–3.7%) indicating that there is little benefit taking a second measurement of FEC. The optimal size of the nucleus was determined by the breeding objective. In schemes 3 and 4, profit per ewe was optimal when the top 5%, 5%, 10% and 10% of rams were selected in the first selection stage for FEC measurement in FLOCK, FEED, TR and IR, respectively. The practical implications of these results are discussed.

Small ruminants (i.e., sheep and goats) are ubiquitous, and contribute significantly to the subsistence, economic and social livelihoods of a large human population in low-input, smallholder production systems in developing countries. Increasing human population, urbanization and incomes, coupled with changing consumer preferences are creating more demand for these animals and their products. This demand can effectively be met by substantially increasing the productivity of these animals. Integrated effort in terms of management, health, genetic improvement and product technology to enhance production and decrease wastage is, therefore, desirable. Efficient genetic improvement programs can boost output and profitability for the smallholders. However, there is a lack of information on sustainable conventional genetic improvement programs under smallholder production circumstances. Consequently, methods for implementing and the factors influencing the success of genetic improvement programs should be studied. This review focuses on the technical and infrastructural issues affecting the genetic improvement of small ruminants in low-input, smallholder production systems. It is concluded that a key step is to identify existing structures, institutions, and indigenous breeding practices, and, to build upon these foundation programs where there are opportunities for sustainable genetic improvement.

Small ruminants (i.e., sheep and goats) are ubiquitous, and contribute significantly to the subsistence, economic and social livelihoods of a large human population in low-input, smallholder production systems in developing countries. Increasing human population, urbanization and incomes, coupled with changing consumer preferences are creating more demand for these animals and their products. This demand can effectively be met by substantially increasing the productivity of these animals. Integrated effort in terms of management, health, genetic improvement and product technology to enhance production and decrease wastage is, therefore, desirable. Efficient genetic improvement programs can boost output and profitability for the smallholders. However, there is a lack of information on sustainable conventional genetic improvement programs under smallholder production circumstances. Consequently, methods for implementing and the factors influencing the success of genetic improvement programs should be studied. This review focuses on the technical and infrastructural issues affecting the genetic improvement of small ruminants in low-input, smallholder production systems. It is concluded that a key step is to identify existing structures, institutions, and indigenous breeding practices, and, to build upon these foundation programs where there are opportunities for sustainable genetic improvement.