The utilization of wilted and unwilted silages by lactating cows and the influence of changes in the protein and energy concentration of the supplement offered

Abstract

Twenty-four lactating British Friesian cows were used in a four-period partially balanced change-over design experiment to evaluate eight treatments consisting of two silage types (wilted and unwilted), each offered in addition to supplements containing both two crude protein (CP) levels (160 and 210 g/kg fresh weight) and two energy levels (10-8 and 12-9 MJ metabolizable energy (ME) per kg fresh weight) obtained by including 100 g spray-dried tallow per kg, in a 2 x 2 x 2 factorial arrangement. All supplements were offered at ttie same rate of 6-8 kg/day and total diet digestibility and food utilization studies were carried out on all animals at the end of the final period of the experiment. A separate twoperiod change-over design expeximent, using two lactating cows fitted with rumen cannulae, was undertaken to determine the influence of the two silages on volatile fatty acid (VFA) proportions in the rumen and to measure the rates of disappearance of dry matter (DM) and nitrogen in the silages and supplements from the rumen.There were no significant interactions between silage and supplement type in terms of animal performance. Animals offered unwilted silage consumed proportionately 003 less DM but produced 0-03 more milk than those offered wilted silage. Although total diet digestibility was not influenced by silage type because of the higher gross energy concentration of the unwilted silage the ME intake with this diet was higher than with the diet based on wilted silage and the ratios of milk energy output to ME available for production (0-54) were similar with both silages. Silage type had no effect on the rumen VFA proportions but influenced the jates of disappearance of DM and nitrogen from the rumen.Increasing the CP concentratioryof the supplement had no effect on the intake of silage DM but resulted in a significant incnja^e in milk yield (0-55 kg/day) but due to a reduction in milk fat concentration there was np^-etfect on yield of either fat-corrected milk or milk energy. The use of the higher energy supplement depressed the intake of silage DM by 0-46 kg/day but resulted in an increase in milk yield of 0-74 kg/day. Neither CP nor energy concentration of the supplement had any effect on DM or energy digestibility of the total diet but there were considerable differences between supplements in the patterns of nitrogen and DM disappearance from the rumen. ZIMMER, E. and WILKINS, R. J. 1984. Eurowilt. Efficiency of silage systems. A comparison between unwilted and wilted silages. Landbauforschung, Volkenrode, Sonderheft 69: 88.

The influence of wilting and season of silage harvest and the fat and protein concentration of the supplement on milk production and food utilization by lactating cattle

“…The resulting silages had good fermentations and the major differences in chemical compositions were higher ash, higher pH, lower crude fibre and lower organic acid concentration with the wilted than the unwilted material, all being in line with other data reported following wilting (Marsh, 1979;Gordon, 1980a and b;Castle and Watson, 1982). However, a consequence of this has been that the ME concentrations of the silages (derived assuming methane energy as 0-08 of GE) indicated only a marginally higher ME with the unwilted than the wilted silage whereas other studies from this Institute and elsewhere have generally indicated a much higher ME with the unwilted material (Gordon and Peoples, 1986). This is contrary to most other published data (Zimmer and Wilkins, 1984) and cannot be readily explained.…”

“…Zimmer and Wilkins (1984) from the Eurowilt studies have reported a mean proportionate depression in milk yield over four studies of 0-02 following wilting. This set of data is therefore not in line with that reported earlier (Gordon and Peoples, 1986) or by Zimmer and Wilkins (1984) which suggested no effects of wilting on the efficiency of MEP use for milk production nor the calorimetric data presented by Unsworth and Gordon (1985) which indicated no effect of wilting on efficiency of ME utilization for milk production. The explanation for the difference between the results of the present investigation with those reported previously lies in the very much greater increase in silage intake, and hence GE intake, and the higher digestibility of the wilted silage based diets in the present study.…”

“…Previous studies have tended to suggest a similar effect (Gordon, 1980b;Gordon and Peoples, 1986) although differences were not significant. Previous studies have tended to suggest a similar effect (Gordon, 1980b;Gordon and Peoples, 1986) although differences were not significant.…”

“…The N degradabilities of each of the three silages and four supplements were determined by the polyester bag method as described by Gordon and Peoples (1986). The fractional rumen outflow rate was determined using soya-bean meal by the method of Ganev, 0rskov and Smart (1979).…”

“…One such study t Present address: Greenmount Agricultural College, (Gordon and Peoples, 1986) while showing 22 Greenmount Road,Antrim. . One such study t Present address: Greenmount Agricultural College, (Gordon and Peoples, 1986) while showing 22 Greenmount Road,Antrim. .…”