DESIGN OF ALTERNATIVE BREEDING PROGRAMS FOR CROSSBRED DAIRY CATTLE IN CENTRAL ETHIOPIA

Abstract

The aim of this study was to determine breeding goal of smallholder farmers, dairy farm economic analysis, derive economic value (EV), sensitivity of EV for scenario change and relative economic importance of goal traits, estimate fixed effects and genetic parameters for selected traits, and finally design alternative breeding programs (BPs) for crossbred cattle of smallholder farmers in Arsi, West Shewa, North Shewa zones of Oromia Region and North Shewa zone of Amhara Region in Ethiopia. The data collected from 243 households and 15 farmers’ group discussions were used to define breeding goal and derive EV. Growth, reproductive, production and longevity traits data collected from Boran (B) breed and crosses of Friesian (F) and Jersey (J) breeds with B breed maintained at Holetta Agricultural Research Center during 1978 to 2020 were used to estimate effect of fixed factors and genetic parameters. The least square means were estimated following general linear model procedure of the Statistical Analysis System (SAS). A bio-economic model with fixed herd size system was used to derive EV. Wombat software program was employed to run mixed animal mode to calculate genetic parameters. In addition, the alternatives BPs were modeled using ZPLAN+ package. The study targeted 143,576 crossbred cows of smallholder farmers and about 54,822 households are expected to be benefited from implementation of breeding program. In the study area, higher proportion (p < 0.0001) of farmers (75.52%) chose dairy as the primary goal and the rest 24.48% favour dual purpose for future genetic enhancement. There was no significant difference (p > 0.05) among zones on breeding goal preferences. The least square means and standard error of daily milk yield, age at first calving (AFC) and calving interval (CI) performances of crossbred dairy cattle under farmer management were 11.28±0.24 litre, 2.96±0.04 years and 1.32±0.02 years, respectively. This study found that the highest source of revenue for dairy farmers was milk (82.77%) followed by sale of culled cows (6.52%) and male animal (6.43%). Expenditure for feed takes the highest share accounting 81.35% of the total cost. The average profit per farmers expressed in Ethiopia currency (ETB, 1 US-$ = 39.55696 ETB) was 72,458.10±5068 per year. Economic values estimated per additive xiv standard deviation were ETB 6083.62 for lactation milk yield (MY), -1311.59 for AFC, -1271.05 for CI and 117.73 for herd life (HL). The EV calculated for MY showed the highest value and contributed 69.26% of total relative importance. Analysis of sensitivity to scenario change (±20%) showed that milk price has positive association with profit and EV, whereas feed price has inversely influenced both profit and EV. The profit obtained by farmers was altered by ±29.08% and ±12.31% as milk price and feed price fluctuated by ±20%, respectively. Similarly, the EV of MY was changed by ±20% with change in milk price and ±7% with feed price. Genotype, birth year, birth season and sex of calves were significantly (p < 0.05) influenced all growth traits except sex of calf on weaning weight (WW). First generation of F and B crossbred calves gains about 80 -100 g more weight per day than the B and the other F x B contemporary groups. Heterosis due to gene combination of F and B resulted in substantial improvement on growth traits (p < 0.01). Crossbred cows significantly outperform the B cows by 3 to 7 folds of lactation milk yield (MY). Even though performance of CI and AFC slightly compromised, upgrading from 1/2F:1/2B (F1) to 3/4F:1/4B (F1) have better advantage as average MY improved by about 34%. The additive effects of F and J breeds were 3985.2±150 and 1195.6±257 kg for MY, 166.3±16 and 18.5±27 days for lactation length (LL), 52.9±25 and -40.3±44 days for CI, -0.23±2 and -9.8±4 months for AFC, and 548.7±431 and -569.9±784 days for HL, respectively. The estimated heterosis effects were 1054.8±145 and -150. 6±76 kg for MY, 62.4±15 and -7.3±8 days for LL, -58.1±24 and -88.7±13 days for CI, -1.9±3 and -4.7±1 months for AFC and -215.0±446 and -890.1±226 days for HL for J and F with B breed crosses, respectively. The loss due to recombination of F and B was significant (p < 0.005) and undesirable for MY, LL, AFC. The heritability (h2) estimates were 0.30±0.00 for MY, 0.18±0.02 for LL, 0.09±0.03 for CI, 0.19±0.06 for AFC and 0.28±0.06 for HL. Strong genetic correlations were obtained between MY and LL (0.84±0.04), LL and CI (0.86±0.10) and LL and HL (0.94±0.07). Desirably higher and negative genetic correlations were detected between yearling weight (YW) and AFC (-0.77±0.09) and post weaning weight gain (PTWWG) and AFC (-0.80±0.09). Results of alternative breeding programs revealed that the predicted genetic gain (GG) for MY per year were 34.52 kg, 49.63 kg, 29.35 kg, 76.16 kg and 77.51 kg for conventional on-station progeny testing breeding program (CSPBP), conventional on-farm progeny testing breeding program (CFPBP), conventional on-station and on-farm progeny testing breeding program (CSFPBP), genomic breeding program (GBP) xv and genomic progeny testing breeding program (GPBP), respectively. The discounted profit of the BPs ranged from ETB 1513.22 in CSPBP to 5551.40 in GBP per cow per generation. Among conventional progeny testing scheme CFPBP generated 53.52% more profit than CSPBP and 37.14% than CSFPBP. Genomic BP outperforms the CSPBP, CSFPBP and CFPBP by 266.86%, 227.70% and 138.96% of discounted profit, respectively. In addition, genotyping bulls can enhance the accuracy of selection of test bull by 16% to 30%. Profit and EV of the traits were desirably less sensitive to the change in price of milk, feed and labor. The estimated genetic variance, heritabilities and correlations between traits and decline in performance of inter-se generations reveal the available potential of improvement through selection and the need of designing appropriate breeding program (BP). Likewise, farmers across all study zones provide more attention for dairy traits than dual purpose and have a similar perception on relative importance of different traits indicating the possibility to develop similar breeding program through study sites. Establish genomic breeding program (GBP) and gradually supporting it with progeny testing (GPBP) are recommended in their order as main way forward to attain better genetic progress in Ethiopia. Following them, the conventional on-farm progeny testing breeding program (CFPBP) is profitable than the other 2 conventional systems. However, until compulsory conditions are in place for genome selection, combination of conventional on-station and on-farm progeny testing breeding program (CSFPBP) can be considered as more practical to be executed. For the success of BP, relevant governmental and non-governmental institute should be engaged, and their roles and responsibility in the implementation of breeding program should be defined. It is also crucial to enhance the community participation through training and supervision, and build the capacity of bio-technology laboratory to facilitate the genotyping of reference population and test bulls.