Determining and predicting feed intake in crossbred sheep from weaning until maturity

Area of Science:

• Animal Science
• Agricultural Economics

Background:

• Feed costs represent a significant operational expenditure in feedlots.
• Accurate feed intake models are essential for efficient livestock management and decision-making.

Purpose of the Study:

• To develop genotype-specific feed intake models for South African feedlot lambs.
• To assess the accuracy of models for predicting daily feed intake, percentage of body weight intake, cumulative intake, and feed conversion ratio.

Main Methods:

• Monitoring feed intake and growth in eight lamb genotypes (four ram, four ewe) from weaning to one year of age.
• Fitting various statistical models to the collected feed intake and growth data.
• Evaluating model performance using R-squared and P-value metrics.

Main Results:

• No satisfactory univariate models were found for predicting daily or percentage feed intake.
• A linear model for cumulative intake demonstrated a good fit (R² > 0.80, P < 0.01).
• Slope parameters of the cumulative intake model correlated strongly (72%) with feed conversion ratio.
• A model predicting feed conversion ratio at a given body weight showed moderate accuracy (R² = 0.5, P < 0.05).

Conclusions:

• The developed cumulative intake model is accurate and simple enough for practical application in feedlot management.
• The cumulative intake model's slope parameters can serve as effective proxies for feed conversion ratio.
• Genotype-specific models offer potential for improved feed efficiency and economic outcomes in feedlots.