Effects of breed exoticness and agroecological zones on selected production and fertility traits in multibreed dairy cattle in Kenya

The aim of this study was to evaluate the effect of degree of exoticness of multi-breed dairy cattle on production and fertility traits in 3 different agroecological zones of Kenya. Test-day milk yield (MY) records (n = 62321) together with fertility-trait records on age at first calving (AFC) (n = 1490) and calving interval (CI) (n = 2640) from a total of 1490 dairy cattle performing in semi-arid arable, semi-arid pasture-based, and semi-humid agroecological zones were analyzed. Animals were grouped into two breed classes based on the proportion of exoticness in their breed composition. These groups were, Exotic Class 1 (EC1) (≤50% exotic, n = 481) and EC2 (>50% exotic, n = 1009). A multiple linear regression model was fitted for AFC and a mixed-repeatability model for test-day MY and CI to determine the effect of exoticness on these traits and to assess whether this effect changed in the different agroecological zones. Overall, EC2 cows had lower AFC than EC1 cows (32.4, se = 0.2 vs. 34.0, se = 0.2 months). However, EC1 cows had a shorter CI than EC2 cows (452, se = 6 vs 466, se = 7 days). Within breed group comparison showed that EC1 had a larger AFC of 36.7 months (se = 0.4) in the semi-arid pasture-based agroecological zone compared to 31.0 (se=0.6) in the semi-humid environment. This denotes delayed puberty in the semi-arid pasture-based agroecological zone. For the EC2, however, it was in the semi-arid arable agroecological zone where cows had the higher AFC compared to the semi-humid environment (34.7, se=0.2 vs. 28.9, se=0.3). In both breed groups, MY was highest in semi-humid and lowest in semi-arid pasture-based environment. Although the semi-humid agroecological zone seemed to favor the onset of puberty and high milk yield, this environment had the longest CI for both breed groups (478, se=9 days for EC1 and 484, se= 7 for EC2). Genotype by environment interaction was significant for AFC and MY (P50% exotic, n = 1009). A multiple linear regression model was fitted for AFC and a mixed-repeatability model for test-day MY and CI to determine the effect of exoticness on these traits and to assess whether this effect changed in the different agroecological zones. Overall, EC2 cows had lower AFC than EC1 cows (32.4, se = 0.2 vs. 34.0, se = 0.2 months). However, EC1 cows had a shorter CI than EC2 cows (452, se = 6 vs 466, se = 7 days). Within breed group comparison showed that EC1 had a larger AFC of 36.7 months (se = 0.4) in the semi-arid pasture-based agroecological zone compared to 31.0 (se=0.6) in the semi-humid environment. This denotes delayed puberty in the semi-arid pasture-based agroecological zone. For the EC2, however, it was in the semi-arid arable agroecological zone where cows had the higher AFC compared to the semi-humid environment (34.7, se=0.2 vs. 28.9, se=0.3). In both breed groups, MY was highest in semi-humid and lowest in semi-arid pasture-based environment. Although the semi-humid agroecological zone seemed to favor the onset of puberty and high milk yield, this environment had the longest CI for both breed groups (478, se=9 days for EC1 and 484, se= 7 for EC2). Genotype by environment interaction was significant for AFC and MY (P<0.01). These findings demonstrated that biophysical variation in different agroecological zones affects production and fertility traits in multibreed dairy cattle differently and hence, it is an important factor to consider when designing genetic improvement programs

Testing phenotypes for degree of resilience using fluctuations in milk yield of dairy cows in sub-Saharan Africa

Despite the relevance of dairy production in the fight against food insecurity and unemployment in sub-Saharan Africa (SSA), negative effects of climate change and general changes in the production environment pose huge challenges to its profitability. Thus, there is a need to improve resilience capacity of dairy animals to adapt to this changing environment. In the current study, we tested two indicators of resilience, logtransformed variance (LnVar) and Skewness (Skew) of deviation, based on fluctuations in animals’ milk yield. Further, we assessed the effects of genotype, agroecological zone, and genotype by agroecological zone (G×E) interaction for these phenotypes. Cows with less than 50% of exotic genetics had higher degree of resilience (P<0.05). Cows performing in semi-arid zones had higher resilience capacity compared to those in semi-humid environment (P<0.05). G×E did not significantly influence both indicators. The results provide valuable information that would inform dairy cattle improvement initiatives in SSA

Enhancing individual animal resilience to environmental disturbances to address low productivity in dairy cattle performing in sub-Saharan Africa

The current review examines potential solutions to enhance the sustainability and productivity of the dairy sector in sub-Saharan Africa (SSA) with an emphasis on breeding for resilience. Additionally, the paper explores various indicators for measuring resilience and provides insights into the data that can be utilized to quantify resilience in SSA’s dairy production systems. Dairy production contributes significantly to food and nutritional security and employment in SSA. However, besides the general lack of enabling policy and institutional environments, production is negatively affected by environmental challenges such as high temperatures and heat stress, diseases and parasites, unreliable rainfall patterns, shortages of feeds and forages and undue preference for taurine cattle breeds regardless of their poor adaptability to prevailing local conditions. Fostering the resilience capacity of dairy animals is imperative to combat climate-related adversities and maintain productivity. This can only be achieved if reliable and practical methods for quantifying and analyzing resilience in SSA are described and undertaken. This study has reviewed variance of deviations, root mean square of deviations, autocorrelation of deviations, skewness of deviations, slope of the reaction norm and its absolute value as possible indicators of resilience in SSA. While previous research has reported genetic variation and favorable correlations of these indicators with health, fitness, and fertility traits, their potential in SSA environments requires further investigation. Besides, labor- and cost-effective phenotypic data collection is essential for characterization of resilience using these indicators. Through this study, we propose frequently collected data on milk production traits, body fat-related traits, and activity patterns as suitable in the sub-Saharan Africa context. The African Asian Dairy Genetic Gains Project by the International Livestock Research Institute (ILRI) offers a valuable opportunity to collate data from diverse dairy systems in SSA for testing the potential of these indicators. Insights from this study are helpful in improving resilience of dairy animals in SSA, which would contribute to poverty alleviation, animal welfare improvement, and better preparedness in lieu of climate change in SSA.</p