Milk production from grass silage diets: effects of the composition of supplementary concentrates

Abstract

Thirty-six British Holstein-Friesian cows were offered 9 kg dry matter (DM) daily of one of 12 concentrates together with grass silage ad libitum in a cyclical change-over design experiment during lactation weeks 8 to 22. The carbohydrate source in the concentrates was either mainly starch, mainly digestible fibre or a 1:1 mixture. Each concentrate type was formulated to provide 120,160,200 or 240 g crude protein (CP) per kg DM and similar metabolizable energy concentration. Silage contained 142 g CP per kg DM, in vivo digestible organic matter was 0-690 kg/kg DM, pH 4-4 and ammonia-N 172-2 g/kg total nitrogen. Silage intake increased as fibre replaced starch in the concentrate. Apparent digestibility of organic matter and energy were highest for starch-based concentrates, but there was no effect of carbohydrate source on yields of milk and milk solids. Milk protein concentration was depressed by feeding mixed or fibrous carbohydrates. Silage intake increased on average by 0-13 kg DM per additional 10 g/kg CP in the concentrate. The digestibility of the diet was not affected by increasing CP except for nitrogen. Milk yield increased by 0-028 kg per additional g/kg CP in the concentrate and there were linear effects ofCP on yields of milk solids. As CP increased, milk fat concentration tended to rise ivith starch but was depressed both overall and by offering mixed or fibrous carbohydrates. In contrast milk protein concentration increased with mixed and fibrous carbohydrates but not with starch. It is concluded that when silage is given ad libitum with 9 kg/day concentrates, CP level has more effect than source of carbohydrate on milk production.

The effects of concentrate energy source on silage intake and animal performance with lactating dairy cows offered a range of grass silages

“…Concentrate energy source had no effect on milk yield in the present study, in accord with the results of Castle et al (1981), Chamberlain et al (1984) (three out of four comparisons), Mayne and Gordon (1984), Phipps et al (1987), Sloan et al (1987 and1988), Aston et al (1994) and Huhtanen et al (1995).…”

“…Concentrate energy source had similar effects on silage DM intake during both the production and digestibility studies. The lack of effect of increasing starch intake on MADF digestibility is in line with the results of Aston et al (1994) and may be attributed to similar concentrations of CP, ERDP, DUP and ME in the concentrate, and /or the concentrate being offered in four equal meals per day. The absence of an effect of concentrate energy source on total diet digestibility is similar to the results of Mayne and Gordon (1984), Phipps et al, (1987) and Huhtanen et al (1995) but is in contrast to the results of Thomas et al (1986) and Aston et al (1994).…”

“…The absence of an effect of concentrate energy source on total diet digestibility is similar to the results of Mayne and Gordon (1984), Phipps et al, (1987) and Huhtanen et al (1995) but is in contrast to the results of Thomas et al (1986) and Aston et al (1994). Concentrate energy source had similar effects on silage DM intake during both the production and digestibility studies.…”

Milk production from grass silage diets: effects of high-protein concentrates for lactating heifers and cows on intake, milk production and milk nitrogen fractions

“…However the increase amounted to 0-008 kg DM per 1 g/kg DM increase in concentrate CP concentration, which is in the same range as responses of 0-005 kg DM (Sutton et ah, 1994) and 0-013 kg DM (Aston et al, 1994a) in previous experiments in this series. However the second increment, which increased the CP concentration to 386 g/kg DM in the concentrates and 243 g/kg DM in the diet, had no effect on silage intake suggesting that silage intake responses to dietary CP concentrations much in excess of 200 g/ kg DM are likely to be small.…”

“…An alternative strategy is to reduce the crude protein (CP) concentration of a fixed ration of concentrate ration as the CP concentration increases concentrates has been shown to result in clear so that the concentrate CP intake remains constant, benefits in terms of grass silage intake and milk One purpose of the present experiments was to production by multiparous cows (Aston, Thomas, examine these two strategies in multiparous cows. Daley and Sutton, 1994a;Sutton, Aston, Beever and There was some earlier evidence that first-calf cows Fisher, 1994; Aston, Sutton and Fisher, 1995). This (heifers) are less responsive than multiparous cows strategy results in the amount of CP from the to protein supplementation (Roffler, Satter, Hardie and Tyler, 1978;Thomas, Aston, Tayler, Daley and clearly the possibility that high-protein concentrates may induce increases in the non-protein nitrogen (NPN) content of the milk or changes in the other protein fractions.…”