Publications

Economic values for production traits (milk yield, MY, kg; 12-month sale weight, LW, kg; consumable meat percentage, CMP) and functional traits (doe live weight, DoWT, kg; number of kids weaned, NKW; kidding frequency, KF; kidding rate, KR, {%}; doe weaning rate, DoWR, {%}; doe survival rate, DoSR, {%}; post-weaning survival rate, PoSR, {%}; pre-weaning survival rate, PrSR, {%} and; residual feed intake of yearlings, RFIy, kg and does RFId, kg) were estimated for the Kenya Dual Purpose goat (KDPG) for systems under two bases of evaluation. The production systems included smallholder low-potential (SLP), smallholder medium-potential (SMP) and smallholder high-potential (SHP), while the bases of evaluation considered were fixed flock-size and fixed feed resource. Under both bases of evaluation, economic values were highest in SMP apart from the economic values for feed intake-related traits (RFIy and RFId). In SMP, the economic values under fixed flock-size scenario were KSh 71.61 (LW), 20.90 (MY), 45.20 (CMP), 13.68 (NKW), 3.61 (KF), 6.52 (KR), 12.39 (DoWR), 22.96 (DoSR), 22.87 (PoSR), 13.18 (PrSR), -2.76 (RFIy) and -3.00 (RFId). The corresponding economic values under fixed feed resources scenario were KSh 73.28, 29.39, 45.20, 16.91, 4.76, 9.45, 13.84, 25.67, 25.15, 16.19, -2.76 and -3.00. Generally in all production systems, economic values for most traits were higher under fixed feed resource than under fixed flock-size scenario. In all systems, the economic values for most of the traits were sensitive to changes in prices of feed, milk and meat. The positive economic values for most traits under fixed flock-size scenario and fixed feed resource indicates that a unit increase in genetic merit for the traits would have a positive effect on the profitability of the systems.

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.