The performance of Mediterranean dairy sheep given access to sulla (Hedysarum coronarium L.) and annual ryegrass (Lolium rigidum Gaudin) pastures in different time proportions

Three experiments were carried out to assess the feeding value of sulla (Hedysarum coronarium L.) as complementary grazing source for Sarda dairy sheep basically fed on annual ryegrass (Lolium rigidum Gaudin) pasture. In experiment 1 (E1), non-pregnant (D) and pregnant (P) ewes were allotted into three groups allocated for 9 h daily, respectively, on plots of sulla (S9), annual ryegrass (R9) or sulla for 3 h in the morning and annual ryegrass for the remaining time (S3R6). In experiment 2 (E2), the treatments were sulla (S22), ryegrass (R22) and two "time mixtures" consisting, respectively, of 3 (S3R19) or 6 h allocation on sulla (S6R16). In experiment 3 (E3) only R22 and S6R16 were compared. In both E2 and E3, milked ewes were used and the total time on the plots was 22 It daily. In E1, the total digestible herbage intake (DDMI), measured by the n-alkane method, was affected by the interaction between sheep physiological state and grazing system (P < 0.01). No effect of the above factors on sheep body weight and body condition changes was evident. In E2, DDMI did not differ between groups up to May when S22 and S3R19 outperformed R22, S6R16 behaving as intermediate (P < 0.05). Milk yield paralleled DDMI results. Milk composition was unaffected, except for milk urea (P < 0.001), lower in R22 (34.0 mg/dl) than the other groups (39.6 mg/dl, S3R 19; 44.4 mg/dl, S6R16; 44.3 mg/dl, S22). In E3, S6R16 ewes grazed for less than 50% of the allocation time on sulla. To conclude, S3R19 can partially offset the decay of grass nutritive value in spring but results are intermediate between those of the mono-specific pastures. S6R16 is less beneficial than S3R19 possibly due to the detrimental effect of condensed tannins on grazing behaviour. (C) 2003 Elsevier B.V. All rights reserved.