In a completely randomized design with a factorial arrangement (3× 5× 3), three fistulated sheep with an average body weight of 47.5 ± 2.5 kg were used to determine the effect of cutting and growing stages (no bloom , early bloom and full bloom) on chemical composition and In situ degradability of alfalfa (Medicago sativa). Nylon bags (50 µm pore size) were filled with 3.5 g of each sample and suspended in the rumen before morning feeding and incubated for seven different times (0, 2, 4, 8, 16, 24 and 48 h). The results showed that alfalfa at no bloom stage had the highest crude protein and the lowest crude fiber content. The third – cut alfalfa had the highest degradability of dry matter and organic matter. Extent of degradability depended on crude fiber and solubility. During growth stage, the protein, soluble material and degradability levels decreased while crude fiber, neutral detergent insoluble crude protein (NDICP), and acid detergent insoluble crude protein (ADICP) increased. The amount of ADICP was an estimate of unavailable crude protein in the rumen. Although the rate of organic matter degradation was maximum in full bloom, no significant difference was observed between the three stages of growth. Effective degradability (ED) of crude protein was significantly different among stages the growth (p<0.05). Effective dry matter degradability (EDDM) with a passage rate of 6%/h was significantly higher in the third cutting of alfalfa. The results of this study showed that first cutting and full bloom alfalfa had the lowest and fifth cutting and no bloom had the highest CP levels. The effect of cutting and growing stages on degradability parameters was variable and did not allow any firm conclusions to be made.

Keywords: Alfalfa, Degradability, Crude protein, Dry matter, Growth stage, Cutting time.

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