| dc.description.abstract |
Ten grazing studies were undertaken in which lactating cows either grazed limited amounts of pure white clover (Trifolium repens cv. Haifa) alone, or were supplemented with 3.4-5.0 kg DM/cow day-1 of maize silage. Marginal returns to additional feeding were 0.58 and 1.03 kg of 4% fat-corrected milk/kg of total DM in spring/early summer (when cows were producing >20 kg milk/day) and autumn (when cows were producing <20 kg milk/day) respectively. While the responses from the lower producing cows were exceptionally good, the relativity between the two groups of cows was contrary to normal expectations; an increase in feeding should result in a greater response from the higher producing cows. The protein level in the clover diet was only slightly lower (23 v. 25%) in spring/summer than in autumn, yet this was associated with significantly (P < 0.05) lower mean rumen ammonia concentrations (114 v. 190 mg/L), indicating that rumen degradable protein may have limited the utilization of energy from maize silage in spring/summer. This is supported by higher faecal nitrogen concentrations recorded in spring/summer. Concentrations of condensed tannins in clover were also higher in spring/summer than in autumn (0.7 v. 0.2%). It is suggested that a significant proportion of the clover protein complexed with the condensed tannins occurring in the flowers present in the sward in spring/summer. |
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