Influence of drying technique on chemical composition and ruminal degradability of subtropical Cajanus cajan L.

The experiment investigated the influence of forage drying methods on the dry-matter digestibility of foliage from Cajanus cajan varieties（ICEAP 00557, ICEAP 01514 and CIMMYT100/01）. These leaves were harvested at week 20 of growth and either oven-or shade-dried and analysed for chemical components and rumen degradability. Three rumen fistulated lactating Holstein cows（430 ± 18 kg live weight） were used to evaluate ruminal degradation kinetics using in vitro and in sacco procedures. Samples were incubated for 0, 4, 8, 12, 24, 30 and 48 h in vitro(Ⅳ Daisy;) procedure. In the in sacco procedure, samples were incubated for 0, 4, 8, 12, 24, 30 and 48 h in the rumen of cows. Dry matter disappearance（DMD）data for both measures were fitted to the equation Y = a + b(1 -e;), where b is the slowly degradable fraction and c is the degradation rate constant, to approximate rumen degradability characteristics of varieties. Shade dried leaves contained higher crude protein（CP）(P < 0.05) than oven dried leaves. Oven drying method increased（P < 0.05） neutral detergent insoluble nitrogen（NDIN） and acid detergent insoluble nitrogen（ADIN） content of varieties. However, shade drying method gave the higher concentration of NDIN and ADIN. Drying technique had no effect（P > 0.05） on ash, neutral detergent fiber（NDF）, acid detergent fiber（ADF） and acid detergent lignin（ADL） of varieties. Drying method did not affect（P > 0.05） calcium（Ca） and phosphorus（P） concentration in the forage dry matter. Drying method had no effect（P > 0.05） on b and c of all varieties during in vitro procedure. However, shade-drying method increased（P < 0.05） b and c of all varieties during in sacco procedure. It was concluded that shade-drying, in contrast to oven-drying, would be the most suitable method as it improves the nutritive value of the forage for ruminants.