Effect of different levels of berseem (Trifolium alexdrinum) supplementation of wheat straw on some physical factors regulating intake and digestion

Four ruminally fistulated cattle of about 318 ± 16 kg body weight were randomly distributed into four groups in an experiment based on 4 × 4 Latin square design. The four dietary treatments were: wheat straw ad lib without any supplement (I), supplemented with berseem at 15 (II), 30 (III), and 45 (IV) percent level. DMI was 3.95, 5.85, 7.28 and 7.08 kg; digestibility of DM was 39.85, 45.61, 52.97 and 47.52%; rumen content was 55.60, 68.45, 74.18 and 75.93 kg, or 18.09, 22.01, 23.37 and 23.22% of body weight; rumen fluid content was 48.62, 60.39, 65.20 and 68.01 kg; rumen pool size of DM was 6.02, 7.61, 7.92 and 7.66 kg; rumen pool size of particles larger than 1.18 mm (LP) was 2.38, 2.78, 2.80 and 2.55 kg; rumen pool size of particles smaller than 1.15 mm (SP) was 3.64, 4.91, 5.12 and 5.05 kg in Groups I, II, III and IV, respectively. Intake and digestibility increased significantly (p < 0.01), with increased level of berseem up to 30%, beyond which no further improvement was observed. Total rumen contents, rumen fluid content and pool sizes of DM increased significantly (p < 0.5) with berseem supplementation, level of berseem had no significant effect. Pool of LP and SP was similar in all the groups. Maximum rumen content was observed at 9, 9, 6 and 3 h post feeding in Groups I, II, III and IV, respectively. Rate of clearance of LP was 3.71, 6.71, 7.27 and 8.75; SP was 0.46, 0.83, 1.20 and 1.35; and communition rate was 3.45, 5.79, 5.92 and 7.37% h−1 in Groups I, II, III and IV, respectively. Rate of clearance of LP and rate of communition were significantly higher (p < 0.01) in berseem supplemented groups. Rate of passage (Kp) was 1.72, 1.88, 2.33 and 2.56% per hour. Kp increased significantly (p < 0.01) with increased level of berseem. From the results it is evident that rumen pool size of indigestible component, rather than rumen content, determines the intake. As Kd was more than Kp, there was an overall improvement of digestibility by 14, 33 and 19% in Groups II, III and IV, respectively, compared with Group I.