The extent to which dietary components are fermented in the rumen is a function of both rate of fermentation and residence time in the rumen. The latter, usually expressed as the mean retention time (i.e. the reciprocal of the fractional outflow rate; MRT), can be determined from the decrease in the concentration of a non-absorbable marker in rumen digesta after an intraruminal dose of marker. This technique, whilst generally satisfactory for solute markers, is less reliable for particulate markers because of difficulties in obtaining representative samples of rumen digesta. The faecal marker excretion technique (Grovum & Williams, 1973) overcomes the problem of representative sampling and also has the added advantage that fistulated animals are not necessarily required. It is based on the fact that the pattern of marker excretion in the faeces after an intraruminal dose of marker reflects the cumulative effects of marker residence time in the various sections of the digestive tract. Provided a satisfactory mathematical description of the excretion curve can be achieved and the component parts identified, or at least that part relating to the rumen, the MRT in the rumen can be obtained. Blaxter et al. (1956) suggested that the ruminant gut is essentially composed of two mixing compartments and a tubular compartment, and that digesta flow can be described by a model consisting of two exponential terms and a time delay. Subsequently, Grovum & Williams (1973) used this model to describe the change in marker concentration in sheep faeces following an intraruminal dose of marker and showed that the longer MRT was associated with the rumen. However, other workers (e.g. In their paper on the theoretical considerations and computer simulation of digesta passage, Grovum & Phillips (1973) concluded that 'a poor fit between the observed concentration of marker and the predicted values for the two-pool model may indicate that a model with two compartments is not descriptive of passage of marker through the gut. Thus new models and new equations can be sought that are more appropriate.' In the present paper an alternative model to describe faecal marker excretion is proposed and was derived by considering digesta flow as a multicompartmental exponential process. It consists of a multiplicative equation containing an exponential term and a doubleexponential term :, available at https://www.cambridge.org/core/terms. https://doi
Greater cultivation of the underutilised Gac fruit, Momordica cochinchinensis, by poorly resourced householders and farmers would potentially improve livelihoods, and, on a larger scale, meet the increasing demand for Gac as a health product. Cultivation methods need to be developed to suit small-and large-scale production and must consider the unpredictable ratio of male to female plants grown from seed, and slow growth induced by cool temperatures. In this study, we examined the responses of Gac to propagation and protected cropping techniques to identify potential methods for increasing production. Plants germinated from seed in seed-raising mix under warm and humid conditions were grown hydroponically to maturity in a climate-controlled greenhouse during a temperate winter, producing fruits that were harvested ripe, from 44 weeks after sowing. Cuttings taken from female plants were dipped in indole-3-butyric rooting hormone powder or gel, or were left untreated, and then placed in rock wool, potting mix, water or closed media sachet. All treatment combinations, with the exception of the untreated potting mix, permitted the development of healthy plants in a second greenhouse crop. Growing plants from seed, then vegetatively increasing the number of productive female plants by cuttings is a means to increase Gac production with limited resources. Gac production using greenhouse technology, as described here for the first time, is relevant to other temperate regions. The finding that larger fruits have a higher percentage of edible aril than smaller fruits provides a new area of investigation towards enhancing production.
1. The effect of harvesting date of perennial ryegrass (Lolium perenne) on the nutritive value of the resultant silage and the effect of substitution of late-cut silage with barley was examined in growing cattle. The diets comprised early-cut (H) and late-cut (L) silage offered alone or with 280 (LCI) or 560 (LC2) g rolled barley/kg total dry matter (DM) substituted for late-cut silage.2. Both silages were prepared with the addition of formic acid (850 g/l; 2.4 litres/t fresh weight) to a partially wilted crop, and were judged to be well fermented (pH 3.9,3.8) with lactic acid contents of 108 and 73 g/kg DM, total nitrogen contents of 24.6 and 18.4 g/kg DM and ammonia-N contents of 121 and 124 g/kg total N (values for early-and late-cut silages respectively).3. Two experiments were conducted to measure duodenal non-NH,-N (NAN) supply in relation to N intake on the four diets (feeding level 18 g DM/kg live weight (LW)) and to examine the partition of the metabolizable energy (ME) supply from the four diets using open-circuit indirect calorimetry (three feeding levels, 14, 17 and 20 g DM/kg LW). The experiments were undertaken with eight and nine Friesian male castrates respectively with a mean starting weight of 300 kg and age 12 months. The animals used in Expt 1 had been previously fitted with cannulas into the dorsal rumen and the proximal duodenum.4. NAN supply was significantly higher on diet H than all other diets which were similar irrespective of the level of barley inclusion. Mean ME contents (MJ/kg DM) of the two silages differed markedly (H 11.9, L 9.7) and barley addition (LCI and LC2) restored values to 10.7 and 11.1 MJ/kg DM respectively. Estimated NAN absorption in relation to energy supply was significantly higher for diet H (1.47 g/MJ ME) than for all other diets (mean 1.25 g/MJ ME).5. Partition of ME supply using conventional linear analysis indicated dietary differences with respect to estimated ME for maintenance (L H, LCI and LC2) and efficiency of utilization of ME supplied above maintenance (L > H, LCI and LC2), but difficulties in biological interpretation of these findings led to the use of exponential curve analysis. This provided an improved description of the findings, and whilst dietary differences were apparent, none were statistically significant. It was concluded that a single exponential equation could be used satisfactorily to describe all values.6. The consequence of these findings in relation to the carcass retentions of energy. fat and protein reported by Thomas ef al. (1988) is discussed and possible reasons for the discrepancies in energy retention measured by comparative slaughter balance and open-circuit indirect calorimetry are considered.In the previous paper (Thomas et al. 1988) the consequence of delaying the harvesting of grass for ensiling on the nutritive value of the resultant silage when offered to beef cattle was examined, and the response to barley substitution of the later-cut material was quantified. That study was concerned with the examination of body and ...
1. Pure swards of perennial ryegrass (Lolium perenne cv. Melle) and white clover (Trifolium repens cv. Blanca)were harvested daily as primary growth (grass in May, clover in June) or regrowths (clover only in July) and offered, in the long form, to growing cattle at a feeding rate of 22 g dry matter/kg live weight. With each forage, two treatments were compared with the untreated forage (C): monensin (100 g active ingredient/kg, 250 mg/d) addition to the rumen (treatment M) or formaldehyde (30 g/kg crude protein (nitrogen x 6.25)) application to the diet (treatment F). The objective of the experiment was to examine means of manipulating N metabolism in the rumen and the duodenal non-ammonia-N (NAN) supply derived from fresh forages. 2.The apparent digestion of ingested organic matter (g/kg) in the rumen was unaffected by treatment M (C 509, M 497) but was significantly ( P < 0.01) reduced by tieatment F (443). The extent of cellulose digestion in the rumen was not affected by any of the treatments imposed and the changes in organic matter digestion were due mainly to effects on N digestion and rumen microbial synthesis. On the untreated diets, duodenal NAN supply averaged 0.74 g/g N intake and treatment M caused a small but non-significant increase (M 0.79 g/g N intake).In contrast, the effect of treatment F was much larger (F 0.91 g/g N intake; P < 0.01). These differences were accompanied by corresponding reductions in rumen NH, concentrations (mg/l; C 350, M 310, F 220; P < 0.001).3. Of the increased flow of NAN to the small intestine observed on the white clover only diets with treatment F, 0.70 was accounted for by an increased net synthesis of microbial N, while treatment M had no effect on microbial N synthesis and a marginal reduction in feed N degradability only with the regrowth white clover diet. Treatment F reduced feed N degradability to a limited extent on both clover diets (C 0.82, M 0.81, F 0.77). No corresponding measurements were made for the ryegrass diets.4. It is concluded that the extensive loss of N from the reticulo-rumen of cattle fed on fresh forages can be reduced by the use of agents to reduce protein solubility. However, the study demonstrated that treatment F may in some circumstances increase N supply to the small intestine more through enhancing microbial N synthesis within the rumen than through increasing the passage of undegraded feed N to the small intestine. The use of monensin, to manipulate proteolytic or deaminative activity in the rumen, or both, was not found to confer any beneficial effects on duodenal-NAN supply.There have been several studies to evaluate the digestion of fresh forages and the nutrient supply arising from such diets (Beever et al. 1971(Beever et al. , 1976(Beever et al. , 1978b Ulyatt & Egan, 1979; VtritC et al. 1984). Recent experiments with growing cattle (Ulyatt et al. Beever et al. 1985 Beever et al. , 1986a have demonstrated that as the amount of nitrogen in the crop increases, considerable losses of N between mouth and duodenum (up to 0.40 of N...
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