Genetic analysis of phenotypic indicators for heat tolerance in crossbred dairy cattle

Climate change-induced rise in global temperatures has intensified heat stress on dairy cattle and is contributing to the generally observed low milk productivity. Selective breeding aimed at enhancing animals’ ability to withstand rising temperatures while maintaining optimal performance is crucial for ensuring future access to dairy products. However, phenotypic indicators of heat tolerance are yet to be effectively factored into the objectives of most selective breeding programs. This study investigated the response of milk production to changing heat load as an indication of heat tolerance and the influence of calving season on this response in multibreed dairy cattle performing in three agroecological zones Kenya. First-parity 7-day average milk yield (65 261 milk records) of 1 739 cows were analyzed. Based on routinely recorded weather data that were accessible online, the Temperature-Humidity Index (THI) was calculated and used as a measure of heat load. THI measurements used represented averages of the same 7-day periods corresponding to each 7-day average milk record. Random regression models, including reaction norm functions, were fitted to derive two resilience indicators: slope of the reaction norm (Slope) and its absolute value (Absolute), reflecting changes in milk yield in response to the varying heat loads (THI 50 and THI 80). The genetic parameters of these indicators were estimated, and their associations with average test-day milk yield were examined. There were no substantial differences in the pattern of milk yield response to heat load between cows calving in dry and wet seasons. Animals with ≤50% Bos taurus genes were the most thermotolerant at extremely high heat load levels. Animals performing in semi-arid environments exhibited the highest heat tolerance capacity. Heritability estimates for these indicators ranged from 0.06 to 0.33 and were mostly significantly different from zero (P &lt; 0.05). Slope at THI 80 had high (0.64–0.71) negative correlations with average daily milk yield, revealing that high-producing cows are more vulnerable to heat stress and vice versa. A high (0.63–0.74) positive correlation was observed between Absolute and average milk yield at THI 80. This implied that low milk-producing cows have a more stable milk production under heat-stress conditions and vice versa. The study demonstrated that the slope of the reaction norms and its absolute value can effectively measure the resilience of crossbred dairy cattle to varying heat load conditions. The implications of these findings are valuable in improving the heat tolerance of livestock species through genetic selection.</p

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

The livestock sector transformation in Ethiopia: the fundamental role of animal identification, registration, data recording and traceability systems

Livestock production in Ethiopia is predominated by extensive production systems where animals graze in communal grazing lands that exposes to disease transmission and indiscriminate breeding. Intensive stall feeding occurs, mostly in peri-urban settings, with cows mainly fed on straw and limited fresh forages. Animal movement within the country for herd replacement poses disease risk due to lack of movement control. Export of live animals and animal products, mostly meat require traceability system which not only able to identify the animal and the premises, where they are raised, but also traces how they left such premises to the ultimate markets. Ethiopia has developed a road map for livestock information system which also requires household, farm, and animal level information. This paper describes and discusses the need for a harmonized national livestock identification, registration, and data recording system, review existing experiences in the country and elsewhere in Eastern Africa, based on which recommendations in the related areas are made. The critical place of animal identification, registration and data recording as the basis for animal and animal product traceability, disease control, genetic improvement of farmers’ animals, annual planning, acquisition of bank loan and insurance are outlined. The need and values of adopting standardized identification system, establish a centralized database, and data capture tools are articulated. In addition, for success, the importance of long-term commitment, at different levels, including the role of both the public and private sectors are emphasized. The role of government in enforcing the related laws and policies, the requisite organizational structure, infrastructure, and human capacity needs are also pointed out. Professional societies like the Ethiopian Society of Animal Production (ESAP), and Ethiopian Veterinary Association (EVA) are platforms to exhaustively discuss and promote establishment and implementation of national system for animal identification, registration, and data capture are underscored

The pathway to genetic gains in Ethiopian dairy Cattle: Lessons learned from African Dairy Genetic Gains Program and tips to ensure sustainability

In recent years, information and communication technology, and genomic tools have respectively enabled crowd-sourced herd performance recording and fastening of genetic gains in dairy cattle. The African dairy cattle genetic gains (ADGG) program is a collaborative effort of International Livestock Research Institute, Livestock Development Institute, and other national and international partners to foster sustainable genetic improvement. The ADGG program has developed and implemented digital herd performance recording tools, national dairy recording platforms, digital extension services, and genomic evaluation pipelines for Tanzania, Kenya, and Ethiopia. The initial program’s target was to register 12,000 dairy herds in each country, however in Ethiopia’s in 98 districts and 6 regions, more than 74,500 herds and 157,000 animals had been registered by July 2022. The volume and diversity of data being captured by national dairy database is steadily growing. For example, today 440,000 test-day milk yield and 313,000 body weight records have been captured. The above data has been used to undertake the first genomic evaluations, results of which have been publicized in the national Cow and Bull Catalogue for the locally bred but genetically superior bulls and cows. Three of the top ranked bulls have been recruited into the National Artificial Insemination (AI) center for broader use nationally. So far, a total of 67,000 semen straws have been extracted from these bulls and are being used to breed cows and heifers in 14 districts of Ethiopia, thereby not only benefiting many local smallholder dairy farmers, but also significantly saving the country foreign exchange which would otherwise have been used to import bulls and semen from outside the country most of bulls may not be as locally adapted and genetically superior. The great achievement has been realized due to existence of systematic animal identification and consistent performance recording, both of which are crucial for sustained national genetic evaluation, identification, and use of genetically superior and locally adapted dairy breeding stock. Furthermore, identifying roles and responsibilities, and strengthening collaboration among key dairy actors and strong government leadership and support are mandatory to build sustainable breeding program