Adaptation of the ovine ruminal flora to biuret

Abstract

The adaptation of the ruminal flora of sheep to the hydrolysis of biuret has been successfully demonstrated. Bi-weekly measurements of biuretolytic activity of ruminal ingesta were made before, during and after the supplementation of biuret to poor, medium and high-quality rations. Generally no activity was found prior to biuret feeding, but an almost immediate response to biuret feeding occurred which increased progressively with the number of days the animals were fed biuret. The time required to reach maximum activity on very low, medium and somewhat higher protein diets were found to be 15, 30 and 70 days approximately. The supplementation with starch in addition to biuret was found to increase biuretolytic activity. Since neither protein nor starch was found to have any direct effect on biuretolytic activity in vitro, a change in numbers of biuretolytic organisms in the ingesta is discussed as a likely mechanism for the adaptation and de-adaptation of the ruminal flora. A stoichiometric conversion of biuret-N to NH 3 -N by active ingesta was demonstrated in vitro but was not reflected by the nitrogen levels in vivo. The activity of the ingesta was greatly reduced by straining.

Evaluation of Beef Cattle Range Supplements Containing Urea and Biuret2

“…These data indicate that either complete biuretolytic activity was not lost during the intermittent feeding period or the rumen microflora were able to readapt to biuret at a faster rate than reported by Schroder and Gilchrist (1969). Perhaps previously adapted animals "readapt" faster than animals never previously .…”

“…However, Clemens and Johnson (1973) and Wyatt (1973) recently found marked biuretolytic activity in 3 to 4 days in lambs fed high roughage diets. The low protein (3% CP) of the major portion of the steers' diet (dry range grass) in this trial may have facilitated the short adaptation period (Schroder and Gilchrist, 1969). Clemens and Johnson (1973), Johnson and Clemens (1973) and Schroder and Gilchrist (1969) found a rapid loss (4 days) of biuretolyric activity when biuret was removed from the diet.…”

“…The low protein (3% CP) of the major portion of the steers' diet (dry range grass) in this trial may have facilitated the short adaptation period (Schroder and Gilchrist, 1969). Clemens and Johnson (1973), Johnson and Clemens (1973) and Schroder and Gilchrist (1969) found a rapid loss (4 days) of biuretolyric activity when biuret was removed from the diet. Biuretolytic activity was not lost on day 17 of this trial even though supplemental biuret was not fed 9 of the previous 10 days.…”

Daily and alternate-day supplementation of urea or biuret to ruminants consuming low-quality forage: III. Effects on ruminal fermentation characteristics in steers1,2

“…These results can be interpreted to suggest that ruminal hydrolysis of biuret to NH 3 -N is slower than hydrolysis of urea to NH 3 -N. Therefore, biuret should be safer than urea when supplemented infrequently to ruminants. Also, early work with biuret suggested that an adaptation period is required to allow ruminal microorganisms to develop adequate biuretolytic activity (Schröder and Gilchrist, 1969) and this activity is rapidly lost when biuret supplementation is halted (Clemens and Johnson, 1973). However, research reported here and in the two companion papers suggests that adequate biuretolytic activity can be obtained after at least 18 d of supplementation and is not lost with everyother-day supplementation.…”

“…Löest et al (2001) increased diet CP of steers from 5.5% without supplementation (low-quality forage only) to 10.3% with supplementation (urea or urea/biuret molasses blocks) and collected rumen fluid on d 3, 7, 14, and 21. Early work by Schröder and Gilchrist (1969) demonstrated that the number of days required to develop maximum biuretolytic activity was a function of the CP content of the basal diet. Their data suggested that peak activity was attained after approximately 71 d with a diet CP concentration of approximately 10.3%.…”