Comparative Analysis of Feed Efficiency in Ruminants Across Farming Systems

Thesis Abstract

In the face of rising global demand for animal protein and mounting concerns about sustainable resource use, this study investigates variations in feed efficiency among ruminants across contrasting farming systems to determine how management practices, dietary regimens, and environmental conditions influence production efficiency and resource use. The problem addressed is the persistent divergence in feed conversion efficiency (FCE) and residual feed intake (RFI) among ruminants raised under pasture-based, semi-intensive, and intensive confinement systems, and how this heterogeneity affects environmental footprints and profitability. The aim is to quantify and compare feed efficiency across farming systems and elucid the underlying drivers, with specific objectives to (i) estimate FCE, RFI, and methane emissions for cattle, sheep, and goats under each system; (ii) evaluate the influence of diet composition, forage quality, and supplementation on feed efficiency; (iii) identify sys-tem-level and animal-level predictors of efficiency using multivariate modeling; (iv) assess the relationship between feed efficiency and production economics; and (v) develop system-specific recommendations for improving efficiency while minimizing environmental impact. A mixed-methods approach will be employed in a cross-sectional design. The study will sample 600 ruminant animals (200 cattle, 200 sheep, 200 goats) across six farms representing pasture-based, semi-intensive, and intensive systems in a temperate region. Data collection will involve standardized live-weight and daily feed intake measurements over 90 days, along with diet analyses using near-infrared spectroscopy (NIRS) for crude protein, neutral detergent fiber, and metabolizable energy estimates. Methane emissions will be estimated using the SF6 tracer technique on a subsample of 180 animals (60 per farming system). Individual animal data will be complemented by farm-level records on housing, grazing duration, supplementation strategies, and production outputs. Instruments will include calibrated feed troughs with automatic weighing, portable gas analyzers for methane proxies, and validated questionnaires for management practices. Validity will be established through calibration trials and inter-observer reliability checks; reliability will be assessed via Cronbach’s alpha for survey items and repeatability tests for intake measurements. Data analysis will proceed in three stages. First, descriptive statistics will summarize FCE, RFI, methane yield, and production metrics by species and farming system. Second, generalized linear mixed models (GLMMs) will assess the effects of farming system, diet composition, and environmental variables on FCE and RFI, with random effects for farm and individual animal. Third, multivariate regression and structural equation modeling (SEM) will explore causal pathways linking diet quality, management practices, and efficiency outcomes, while controlling for body weight, age, and lactation status. Methane intensity will be analyzed using regression against FCE, dietary fiber, and energy density. The theoretical framework will integrate the Production Ecology of Ruminant (PER) model and the Environmental Kuznets Curve for agricultural systems to interpret efficiency gains alongside environmental implications. Hypothesis tests will evaluate whether intensive systems yield superior FCE but also higher methane intensity, and whether improvements in forage quality and strategic supplementation mitigate emissions while enhancing efficiency. Key expected findings include quantifiable differences in FCE and RFI across systems, with semi-intensive and intensive systems showing higher individual animal efficiency but variable environmental impacts depending on diet and grazing management. The analysis is anticipated to reveal that improvements in diet quality and balanced roughage-to-concentrate ratios can elevate FCE and reduce methane per unit of product, and that institutional or farm-specific practices significantly mediate efficiency outcomes. The study contributes to knowledge by providing a comprehensive, cross-system appraisal of feed efficiency in ruminants, integrating economic and environmental dimensions, and offering evidence-based recommendations for feed formulation, grazing management, and housing configurations tailored to system-specific constraints. The conclusion will articulate pragmatic strategies for policymakers and farmers to optimize feed efficiency while reducing greenhouse gas emissions, including targeted breeding for efficient phenotypes, adoption of precision feeding technologies, and enhancement of fiber utilization through rumen-optimized diets. Recommendations will emphasize context-specific intervention packages, incremental adoption pathways, and areas for further longitudinal research to validate cross-system applicability.