The productivity of lactating dairy cows grazing white clover and supplemented with maize silage

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.