Unwilted red clover and alfalfa herbage were hand-chopped, inoculated, ensiled into laboratory silos and opened after 0, 1, 3 and 7 days. Proteolysis was 40% lower with the red clover silage than alfalfa silage after 7 days of ensiling. The lower extent of proteolysis with the red clover silages could not be explained by differences in dry matter content, pH decline nor final pH of the silage. It was determined that red clover has a buffer soluble protein that could inhibit proteolysis in red clover and alfalfa. The soluble protein is possibly a polyphenol oxidase.

One hundred and two multiparous Holstein/Friesian dairy coivs were used to examine the effect on food intake and milk production of replacing 330 g/kg dry matter (DM) of first-cut perennial ryegrass silage (GS) with either fermented (FW) or urea (40 g/kg DM) treated (UW) whole-crop wheat, brewers' grains (BG), fodder beet (FB) or maize silage (MS). A forage mixture containing GS and 750 g/kg DM of maize silage (MSH) was also offered. Dietary crude protein (CP) concentrations were equalized by offering all cows 6 kg DM per day of an appropriate concentrate supplement. DM intake and milk yield of cows offered GS (15·3, 23·0 kg/day) were increased (F < 0·01) by the inclusion of BG (16·3, 26·7 kg/day), FB (17·6, 25·9 kg/day), MS (16·6, 26·4 kg/day) and MSH (18·5, 27·6 kg/day). BG, FB and MS all produced similar increases in milk yield. Although the inclusion of FW and UW increased (F < 0·05) DM intake, milk yield was not significantly affected. The differences between the highest and lowest milk fat concentration, produced by FB (42·9 g/kg) and BG (40·1 g/kg) respectively, and the highest and lowest milk protein concentration produced by FB (32·1 g/kg) and GS (29·9 g/kg) respectively, were statistically significant (F < 0·001). Milk fat and protein yields of cows offered GS (0·97, 0·71 kg/day) were increased (F < 0·01) by BG (1·07, 0·82 kg/day), FB (1·11, 0·83 kg/day), MS (1·11, 0·83 kg/day) and MSH (1·12, 0·88 kg/day). Intermediate values were recorded for FW (1·01, 0·72 kg/day) or UW (1·00, 0·73 kg/day). Results show that farmers should consider replacing a major part of the grass silage component with an alternative forage or forage substitute.

The loss of protein (proteolysis) during the ensiling of forage legumes is a severe problem. Alfalfa (Medicago sativa L.) will lose 44 to 87% of its protein during ensiling, whereas red clover (Trifolium pratense L.), a legume of similar protein content, will lose only 7 to 40%. Reasons for this difference in proteolysis are unknown. Research was conducted to determine and compare the general characteristics (rates, pH and temperature effects) of proteolysis in red clover and alfalfa extracts, and secondly to evaluate different in vitro test proteins to monitor legume proteolysis. Proteolytic rates of alfalfa and red clover extracts were not significantly different when either ribulose 1,5‐bisphosphate carboxylase/oxygenase (RubisCo) or bovine serum albumin (BSA) was used as the protein substrate; however, both legumes displayed significantly higher rates for the degradation of RubisCo than BSA (P < 0.10). The pH optima were 5.5 for both legumes when RubisCo was degraded, and 5.5 and 6 for alfalfa and red clover, respectively, when BSA was the substrate. Proteolysis in the legume extracts had similar pH and temperature stabilities and temperature optimum for the degradation of RubisCo. These data suggest that alfalfa and red clover have similar inherent proteolytic activity and cannot explain the difference in extent of proteolysis in the two silages.

Red clover (Trifoliurn pratense) is a legume that will brown quickly upon harvesting. This browning of red clover has been correlated to a reduction in proteolysis and requires the presence of a polyphenol oxidase and soluble phenol substrates. A method was developed to screen forages for soluble phenols, soluble polyphenol oxidase activity and extract browning. Fourteen different legumes and 24 red clovers (22 plant introductions and two cultivars), field grown in replicated plots, were screened. Of the different legumes, only red clover had measurable soluble polyphenol oxidase activity (7.70 abs g-leaf) and underwent browning (0.245 abs g-leaf). This extract browning and polyphenol oxidase activity were present in all red clovers tested and ranged from 0.153 to 0.458 and 6.00 to 9.00 abs g-leaf, respectively. All of the legumes, including all red clovers, gave a positive response for soluble phenols.