Protection of leaf protein of lucerne (Medicago sativa L.) against degradation in the rumen by treatment with formaldehyde and glutaraldehyde

Abstract

SUMMARYAqueous glutaraldehyde, in the presence of wetting agents Tween-20 or Haemosol, reacted with fresh cut lucerne (Medicago sativa L.), complete reaction being obtained with about 7·2 g (72 mmol)/kg herbage, or 18g/100g crude protein. Reaction with 25% w/v aqueous glutaraldehyde sprayed on to fresh lucerne was rapid, and at the rate of 66 mmol/kg lucerne, all aldehyde had reacted in 3 h and about 60% of the soluble leaf protein became insoluble. Formaldehyde at twice the molar concentration of glutaraldehyde was absorbed rapidly, but a longer time, up to 24 h, was required for the protein to become insoluble. Treatments with 22, 44 and 66 mmol glutaraldehyde/kg lucerne, and 44, 88 and 132 mmol formaldehyde/kg showed that reaction with leaf protein was approximately proportional to the amount of aldehyde. A major effect on the leaf cells was the fixation of chloroplasts, and intact fixed chloroplasts were isolated from treated lucerne with high protein: chlorophyll ratios of 5·8:1 to 9·5:1.Two varieties of lucerne, Kabul and Europe, pot-grown in a controlled environment cabinet, reacted rapidly when sprayed with glutaraldehyde and in 3 h soluble leaf protein was reduced from 30 to 16–17% of the total N. The plants rapidly lost water and the dry matter of the leaves rose to 42% for Kabul and 45% for Europe in 24 h. Stems showed little effect. Field spraying of lucerne with glutaraldehyde similarly fixed soluble leaf protein and caused desiccation of the leaves, rising to 47–50% D. M. in 3 days. The stems were little affected and subsequent regrowth of the plants was not inhibited.Feeding glutaraldehyde- and formaldehyde-sprayed lucerne to rumen-fistulated cattle showed that release of soluble leaf protein into the rumen fluid was greatly reduced, mean values being 40 and 43% respectively of the values obtained when control lucerne was fed. Mean ammonia concentrations were similarly reduced to 49 and 33% of the control values. Formaldehyde-treated lucerne, even after reaction for several days, frequently showed toxic effects on rumen micro-organisms, particularly protozoa. Glutaraldehyde reacted more rapidly with herbage and no toxic effects were observed. Both glutaraldehyde- and formaldehyde-treated lucerne were highly palatable to cattle.

The effect of formaldehyde or glutaraldehyde application to lucerne before ensiling on silage fermentation and silage N digestion in sheep

“…Both formaldehyde and glutaraldehyde possess antimicrobial properties which, whilst of potential benefit during ensiling, could be harmful in the rumen. Mangan et al (1980) observed reduced microbial motility in the rumen when cattle were given formaldehydetreated lucerne but not when they were given glutaraldehyde-treated lucerne. An adverse effect of formaldehyde-treated silage on rumen microbes, as evidenced by a decreased microbial N flow at the duodenum, was also found in the study of Beever et al (1977), although this did not occur in other studies (Siddons et al 1979;Thomson et al 1981;Overend & Armstrong, 1982).…”

“…In the present study, soluble protein content did decrease between additive application and completion of ensiling but this was probably due to precipitation by formic acid since it occurred to a similar extent with all treatments and was not accompanied by an increase in NPN content. The presence of formic acid in all additives may also explain the absence of a more rapid reaction between glutaraldehyde and protein than between formaldehyde and protein, as observed by Mangan et al (1980), because aldehyde-protein bonds are less stable at low pH (Ferguson et al 1967).…”

“…In terms of increasing net protein absorption from the small intestine, glutaraldehyde was superior to formaldehyde, although it also reduced OM digestion in the rumen to a greater extent which might adversely affect total DM intake. Its effect, if any, on the efficiency of utilization of absorbed protein is not known, although Mangan et al (1980) reported that both formaldehyde and glutaraldehyde reduced the nutritional value of casein and leaf protein.…”

“…The studies of Mangan et al (1980) suggested that glutaraldehyde may offer certain advantages over formaldehyde as a silage additive. Glutaraldehyde was found to be more effective than formaldehyde in the fixation of isolated chloroplasts, it reacted more rapidly with protein and did not affect protein digestibility.…”

Characteristics of the rumen proteolysis of fraction I (18S) leaf protein from lucerne (Medicago sativa L)

“…(Medicago sativa L) (McArthur & Miltimore, 1961). During mastication of herbage by cattle, fraction I is readily released from plant tissues and is freely available to the rumen microflora in large amounts (Mangan et al 1976). Preliminary communications of some of the results have been given (Nugent & Mangan, 1978;Nugent, 1978).…”