The experiment was conducted in Debre Zeit Agricultural Research Center with the objective of evaluating the effects of sources of dietary protein supplemented to oat-vetch mixture hay on milk yield, milk composition and profitability in lactating crossbred dairy cows. Four high grade cross bred (Holstein Friesian × Boran) dairy cows with similar lactation stage (mid lactation) and parity were used. The experimental diets were T1 (ad libitum oat-vetch hay + noug seed cake), T2 (ad libitum oat-vetch hay + cottonseed cake), T3 (ad libitum oat-vetch hay + linseed cake) and T4 (ad libitum oat-vetch hay + mixture of the three oil seed cakes). A 4 × 4 Latin square design was used for the feeding experiment with four dietary treatments assigned to animals at random initially. The animals were offered hay at a rate sufficient to allow for a 20% refusal and the amount of concentrate offered was at 0.5 kg/l of milk in all treatments. The concentrate mix consisted of 33% oil seed cakes (OSC), 66% wheat bran and 1% salt. Treatment effects on milk yield, milk fat, milk protein, lactose and total solids were significantly different (P<0.05). Economic analysis showed that T2 based supplementation was feasible than the remaining dietary treatments. Therefore, it can be concluded that T2 can optimize both biological and economic response of dairy cows.
Key words: Cottonseed cake, dairy cow, linseed cake, milk, noug seed cake, oat-vetch, wheat bran.
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