Abstract
Background: Calf rearing is a long-term investment in feed, labour, and other resources to ensure high-quality replacements for the herd. Many of the dairy farms in urban dairy production systems do not give sufficient attention to male young stocks because they do not generate income for many months until after they first calve down and are slaughtered for beef.

Objectives: This study was conducted to formulate milk replacer and evaluate its effects on calf growth performance; physiological, hematological, and biochemical parameters.

Material and Methods: Twelve Holstein crossbred male calves aged 3 days with an average initial body weight of 38.93±2.85 kg was purposively selected and randomly allotted to three dietary treatments. The treatment diets were designated as T1 (whole milk: WM), T2 (commercial milk replacer: CMR), and T3 (locally formulated milk replacer: LMR). The treatment diets fed to calves at 12%, 10%, and 8% of body weight for the first 30 days, 31-60, and 61-90 days, respectively. Data on feed intake, growth performance, physiological, hematological, and serum biochemical parameters were repeatedly measured and analyzed.

Results: The study indicated that calves fed on whole milk significantly (P<0.05) recorded the highest body weight change, body weight gain, and feed conversion efficiency. Calves fed on farm-formulated milk replacers significantly (P<0.05) exhibited the lowest values in total red bloold cell count, hemoglobin, mean corpuscular volume, and total cholesterol, and the highest values in blood urea nitrogen . The results showed that farm-formulated milk replacer is 25,647 and 15,381.2 birr less expensive than natural milk and commercial milk replacer, respectively.

Conclusion: The study revealed that using farm-formulated milk replacers as a milk substitute for whole milk or commercial milk replacer had no adverse effect on the calf’s blood metabolites and health and would be economically advisable and profitable for dairy producers.

Key words: Calves, Biochemical, Hematological, Milk replacer, Physiological, Whole milk