A study was conducted to assess the effects of rapid wilting of grass prior to ensiling on milk composition in lactating dairy cattle across a range of silage harvests. The effects of wilting on the response to bacterial inoculation were also examined. Experiments 1 and 2 were of 2 x 2 factorial design based on the factors wilting (unwilted and wilted treatments) and inoculant (control and inoculant treatments). The inoculants each had Lactobacillus plantarum plus other bacterial species. Experiments 1 and 2 had 3 and 8 harvests respectively and the corresponding feeding experiments were balanced changeover designs with 3 and 8 periods respectively. The feeding periods were of 8 and 3 weeks duration in Experiments 1 and 2 respectively and during each period each silage was fed ad libitum together with a concentrate supplement to 12 cows.
The durations of the wilting periods ranged from 24 to 48 h in each experiment and the mean initial and final dry matter contents of the grass were 200; 317 g/kg and 176; 316 g/kg for Experiments 1 and 2 respectively.
In Experiment 1 the butterfat, protein and lactose concentrations (g/kg) from the unwilted and wilted silages were 45.1 and 47.2 (s.e. 0.23, P<0.001), 33.7 and 35.6 (s.e. 0.11, P<0.001) and 48.9 and 48.7 (s.e. 0.08, P<0.05) respectively. In Experiment 2 the corresponding values (g/kg) were 45.2 and 46.4 (s.e. 0.23, P<0.05), 32.3 and 33.2 (s.e. 0.13, P<0.05) and 48.9 and 49.1 (s.e. 0.06, P>0.05) respectively. Inoculation had no significant effects on milk composition with either unwilted or wilted silage except for a reduction in protein content in Experiment 1, with values (g/kg) of 34.8 and 35.4 (s.e. 0.11, P<0.05) for control and inoculant treated silage respectively.
It is concluded that wilting produced statistically significant increases in the concentrations of butterfat and protein in milk and that inoculants had little effect on milk composition in this study.