Comparative Lactation Performance in Indigenous vs. Crossbred Dairy Cattle Feedlots

Thesis Abstract

In dairy systems, Indigenous cattle are often managed under low-input conditions, while crossbred dairy cattle are favored for higher milk yield, yet the comparative lactation performance and its mediating factors in feedlot contexts remain underexplored, limiting evidence-based decision-making for breed selection and management strategies. This study aims to compare lactation performance between Indigenous and crossbred dairy cattle housed in feedlots, to identify the contributions of nutrition, health status, and management practices to lactation outcomes, and to test if breed-related differences persist after adjusting for confounders. The specific objectives are (1) to quantify daily milk yield, lactation length, total milk production, and lactation persistency across breed groups; (2) to evaluate the influence of diet composition, rumen health indicators, body condition score, and metabolic profiles on lactation performance; (3) to assess the incidence and impact of subclinical mastitis and reproductive efficiency on lactation trajectories; (4) to determine whether breed-by-management interactions exist in shaping lactation outcomes; and (5) to provide evidence-based recommendations for feedlot management tailored to Indigenous and crossbred populations. A mixed-methods, comparative cohort design will be employed. The study will be conducted in two commercial dairy feedlots located in arid and temperate agro-ecological zones to enhance generalizability. Population comprises lactating Indigenous (n = 180) and crossbred (n = 180) dairy cows, matched by parity (2–4) and stage of lactation (10–120 days in milk) at enrollment. A stratified random sampling approach will be used to select individuals within each breed category, ensuring balanced representation across pens and feeding regimens. Data collection will combine longitudinal quantitative measurements and targeted qualitative observations. Quantitative data will include daily milk yield captured via calibrated milk meters, milk composition analyses (fat, protein, lactose), lactation length, dry matter intake, body condition score, body weight, blood metabolites (non-esterified fatty acids, beta-hydroxybutyrate, glucose, urea), and health records for subclinical mastitis (somatic cell count thresholds) and reproductive metrics (calving interval, days to first insemination). Dietary data will document concentrate-to-forage ratios, crude protein, energy density, and mineral supplementation. Qualitative components will include weekly assessor notes on animal welfare indicators and observer-guided assessments of management practices. Data will be analyzed using a combination of linear mixed-effects models and generalized linear mixed models to account for repeated measures and pen-level clustering. The primary analytical framework will include fixed effects for breed (Indigenous vs. crossbred), diet regimen, health status (mastitis presence/absence, metabolic indicators), and interactions between breed and management variables, with random effects for cow and farm. Multivariate regression will identify independent predictors of total milk production and lactation length, while survival analysis will explore factors associated with lactation termination. Mediation analyses will test whether diet quality and metabolic status mediate breed effects on lactation outcomes. In addition, descriptive statistics will summarize lactation curves, and ANOVA will compare mean lactation performance across groups at key lactation stages. Theoretical underpinnings will draw on the Resource-Based View to interpret breed-specific asset differences and the Sustainable Intensification framework to evaluate management efficiency. The study will assess potential biases and perform sensitivity analyses to validate robustness of results. Expected findings include higher average daily milk yield and total lactation production in crossbred cattle, with Indigenous cattle displaying longer lactation lengths under optimized feedlot conditions; however, parity between groups may emerge when diet quality and metabolic health are enhanced. Diet quality and metabolic indicators are anticipated to emerge as significant mediators of lactation performance, with stronger breed-by-management interactions under suboptimal nutrition. The study will contribute to knowledge by quantifying breed-specific lactation responses in feedlots under real-world management, elucidating the role of nutrition and health in modulating genetic potential, and informing breed- and management-specific recommendations. The practical implications include evidence-based guidelines for feedlot nutrition schemes tailored to Indigenous and crossbred herds, including targeted supplementation, mastitis prevention strategies, and reproductive management to optimize lactation performance. The study will inform policy discussions on breed utilization in smallholder and commercial dairy systems and highlight areas for further research, such as genomic selection for lactation resilience and the economic evaluation of breed-specific lactation strategies. The main conclusion posits that while crossbred cattle exhibit superior raw lactation metrics, optimized nutritional and health-management practices can mitigate differences, underscoring the importance of integrated management to maximize lactation performance across breed groups. Recommendations emphasize tailored feeding protocols, proactive mastitis control, and ongoing monitoring of metabolic status to sustain lactation efficiency in diverse feedlot contexts.