Genetic parameters, productivity indices and breeding plans for designing community-based goat breeding programs in Ethiopia

Field: Agricultural and Biological Sciences (Life Sciences)

The overall objectives of this dissertation were to improve access to improved/selected bucks by farmers of the research sites and to contribute to their food security and income improvements. The specific objectives were: 1) to present reliable genetic parameter estimates based on meta-analysis of literature reports; 2) to evaluate production and productivity of three indigenous goat breeds in Ethiopia namely Abergelle (AB), Central Highland (CH) and Woyto-Guji (WG) and have bench mark production and productivity estimates for the ongoing Community Based Breeding Programs (CBBPs) in Ethiopia; 3) to evaluate alternative breeding scenarios in the CBBP of the three goat breeds including dam-side selection, genomic selection and two-tier breeding programs; and 4) to assess the need for recording birth weight in CBBP of small ruminants. This dissertation was based on four articles/manuscripts. Accordingly, in article 1, unweighted and weighted average genetic parameters including direct heritability (ha 2 ), maternal heritability (hm 2 ), ratio of common environmental variances (c2 ), repeatability (R), phenotypic (rp) and genetic (rg) correlations for growth, reproduction and milk production traits in goats were presented. Unweighted averages across publications were obtained directly. For the calculation of weighted average ha 2 , hm 2 , c 2 and R, the inverse of their variances were used. Weighted average rp and rg were transformed to an approximate normal scale using Fisher’s Z transformation and then transformed back to correlations. Weighted average ha 2 for growth, reproduction and milk production traits ranged from 0.03 to 0.45, 0.00 to 0.17 and 0.15 to 0.22, respectively. Weighted averages rp and rg correlations among growth traits ranged from -0.06 to 0.84 and 0.01 to 0.98, respectively. It seemed that weighted average ha 2 , hm 2 , c 2 , R, and rg are more reliable for two reasons: weighted estimates were more conservative than values based on relatively higher number of records and the absence of significant effects of the tested fixed factors on some parameter estimates. Papers II-VI were based on data generated from the three indigenous goat breeds, in two villages for each. Production parameters including three months weight (3mw, kg), kidding interval (KI, days) and litter size at birth (LSB); and productivity indices including live weight production per parturition (kg) (index I), index I per postpartum weight (ppw) (Index II) and overall productivity (index III) were analyzed in manuscript II. Fixed effects of villages, year, season, type, sex, and parity of kids’ birth, flock size and ppw were investigated on the parameters, except for index III. The overall means of 3mw (kg) were 7.44, 10.96 and 9.38 for AB, CH and WG goat breeds, respectively. The overall means of KI were 362, 268 and 309 days for AB, CH and WG goat breeds, respectively. The overall means of LSB for AB, CH and WG goat breeds were 1.03, 1.40 and 1.09, respectively. Overall means of index I and index II were 16.66 kg and 0.50, respectively. xii Index III ranged from 0.27 to 0.53. In general, CH goat breed was found to be the most productive using the three indices. In manuscript III, application of dam-side (SN2) and genomic selection (SN3) onto the current breeding practice, where only male side selection is practiced, (SN1) and expansion of SN1 to a two tiers programs (SN4) were evaluated for three indigenous goat breeds to determine the optimal scenario(s). Due to significant distances between CH Gonder site and CH Ambo site, separate breeding plans were optimized for the CH goat breeds. The predicted annual genetic gain (PAGG) in six month weight (6mw, kg) ranged from 0.308 to 0.467 (CH Gonder site), 0.209 to 0.311(CH Ambo site), 0.188 to 0.270 (WG) and 0.174 to 0.249 (AB). The PAGGs in KI for WG goats ranged from 0.167 to 0.419 from all the scenarios. The PAGG in average daily milk yield (ml) and survival to six months (SURV) (%) for AB ranged from 0.617 to 0.970 and 0.008 to 0.013, respectively. The PAGGs in LSB and litter size at weaning (LSW) for CH were found to be small (0.001 to 0.002). The discounted profit from SN3 was negative for all breeds. Based on the PAGGs and discounted profitability, SN2 was recommended. In article IV, the Pearson correlation "r" between birth weight (BWT) & six month weight (6MW), BWT & nine month weight (9MW), three month weight (3MW) & 6MW & 3MW & 9MW; and regression coefficients ("b") of 6MW & 9MW on BWT, 6MW & 9MW on 3MW were investigated. The "r" BWT & 6MW, BWT & 9MW, 3MW & 6MW & 3MW & 9MW ranged from 0.099 to 0.176, 0.051 to 0.163, 0.598 to 0.706 & 0.370 to 0.546, respectively. The "b" of 6MW on BWT, 9MW on BWT, 6MW on 3MW & 9MW on 3MW ranged from 0.494 to 0.999, 0.311 to 0.996, 0.706 to 0.927 and 0.415 to 0.669, respectively. In general, BWT had weak "r" with 6MW & 9MW in three indigenous goat breeds of Ethiopia. However, it seems that recording BWT in the CBBP is compulsory. Hence, it was concluded that keeping BWT records under the CBBP of small ruminants has little or no significance. In summary, reliable genetic parameter estimates are presented for genetic improvements in goats. Production parameters and productivity indices presented here could be used as reliable benchmark for the anticipated CBBPs. The productivity indices could also be used to compare productivity efficiencies among different goat breeds. Planning dam-side selection could be considered together with sire side selection. Recording of BWT could be avoided in CBBPs to contribute to reduced breeding costs.