Passage and rumination of inert particles varying in size and specific gravity as determined from analysis of faecal appearance using multicompartment models

The effect of size and density on the mean retention time of particles in reindeer (Rangifer tarandus)

Particle passage from the reticulorumen (RR) depends on particle density and size. A classic way of assessing these effects is the use of plastic markers of varying density and size that are recovered in the faeces. Here, we report results of an experiment where four fistulated reindeer (Rangifer tarandus, 96 ± 12 kg) were fed two different diets (browse, voluntary dry matter intake [DMI] 70 ± 10 g/kg0.75/d; or a pelleted diet, DMI 124 ± 52 g/kg0.75/d) and dosed via fistula with 8 different particle types combining densities of 1.03, 1.22 and 1.44 g/ml and sizes of 1, 10 and 20 mm. Generally, particles that passed the digestive tract intact (not ruminated) did so relatively early after marker dosing, and therefore had shorter mean retention times (MRT) than ruminated particles. On the higher intake, the overall mean retention time (MRT) of particles was shorter, but this was not an effect of shorter MRT for either intact or ruminated particles, but due to a higher proportion of intact particles at the higher intake. This supports the concept that ruminants do not adjust chewing behaviour depending on intake, but that a lower proportion of digesta is submitted to rumination due to pressure-driven escape from the forestomach at higher gut fills. Compared to cattle (Bos primigenius taurus), muskoxen (Ovibos moschatus) and moose (Alces alces) that had received the same markers, reindeer had a lower proportion of 1 mm particles that passed intact. Our results support the concept that the critical size threshold for particles leaving the ruminant forestomach is dependent on body size. While the results likely do not represent findings peculiar for reindeer, they indicate fundamental mechanisms operating in the forestomach of ruminants.

Determination of physical characteristics, chemical composition and digestion coefficients of treated lemon pulp with Saccharomyces cerevisiae in goat diet

The aim of this study was to evaluate the effects of processing of lemon pulp with Saccharomyces cerevisiae on physical properties, chemical composition, digestion coefficients and blood parameters. Eight adult male Raeini goats were used in a 28-day period. The experimental design was a completely randomised design with two treatments and four replicates. The first 21 days were for adaptation, and the last 7 days were for collecting samples. The animals were housed in individual metabolic cages equipped with a urine-faeces separator and were fed with diet containing alfalfa hay (60%) and lemon pulp (40%) at the maintenance level. Collected data were subjected to analysis of completely randomised design. With diet containing processed lemon pulp, functional specific gravity, bulk density, soluble dry matter, percentage of crude protein, neutral detergent fibre (NDF), acid detergent fibre and crude ash were significantly increased and water-holding capacity, insoluble dry matter, insoluble ash percentage of dry matter, organic matter, crude fat, non-fibrous carbohydrates and nitrogen-free extract were significantly decreased (p < 0.05). Digestion coefficient of organic matter in dry matter and metabolisable energy were also decreased in treated lemon pulp (p < 0.05). Compared with untreated lemon pulp, digestibility of crude protein and NDF was higher (p < 0.05), but digestibility of crude fat was lower (p < 0.05). In general, processing of lemon pulp with S. cerevisiae improved the physical characteristics and increased the percentage of crude protein and the digestion coefficients of protein and NDF.

Transmission of weed seed by livestock: a review

Weed seeds are readily translocated by livestock by attachment to their coat, by consumption or in vehicles used for transporting them. Livestock transport by land, sea and air is increasing worldwide, which together with increasing livestock production, is anticipated to escalate the risk of weed incursions and displace native flora. There is a particular risk of widespread weed seed dissemination in Australia with its extensive grazing practices and significant amounts of livestock movement. Consumption of weed seeds is largely dependent on grazing management practices, with lax grazing facilitating inflorescence production, the seeds of which may then be consumed if grazing pressure increases. Seed passage through the animal depends on the type of seed and animal intake and is typically 30–70 h. The germination rate of weed seeds is usually reduced by passage through the animal, but faeces in which seed is excreted also have the potential to provide nutrients and moisture to support the germinated plant. Seed viability is largely determined by the type of seed dormancy (particularly the permeability of the seed coat) and the species of livestock. It is concluded that weed seed transmission by livestock is a growing concern that requires addressing at local, national and international levels.

The effect of size and density on the mean retention time of particles in the reticulorumen of cattle ( Bos primigenius f. taurus), muskoxen ( Ovibos moschatus) and moose ( Alces alces)

Particle passage from the reticulorumen (RR) depends on particle density and size. Forage particle density and size are related and change over time in the RR. Particle density mainly influences sorting in the reticulum, whereas particle size influences particle retention in the fibre mat of stratified rumen contents ('filter-bed' effect). We investigated these effects independently, by inserting plastic particles of different sizes (1, 10 and 20 mm) and densities (1·03, 1·20 and 1·44 mg/ml) in the RR of cattle (Bos primigenius f. taurus) as a pilot study, and of muskoxen (Ovibos moschatus; n 4) and moose (Alces alces; n 2) both fed two diets (browse and grass). Faeces were analysed for plastic residues for 13 d after dosing to calculate mean retention times (MRT). The results confirmed previous findings of differences in absolute MRT between species. Comparing muskoxen with moose, there was no difference in the effect of particle density on the MRT between species but particle size had a more pronounced effect on the MRT in muskoxen than in moose. This indicated a stronger 'filter-bed effect' in muskoxen, in accord with the reports of stratified RR contents in this species v. the absence of RR content stratification in moose. Low-density particles were retained longer in both species fed on grass diets, indicating a contribution of forage type to the 'filter-bed effect'. The results indicate that retention based on particle size may differ between ruminant species, depending on the presence of a fibre mat in the RR, whereas the density-dependent mechanism of sedimentation in the RR is rather constant across species.

Passage rate of solids and fluids in the digestive tract of buffaloes, cattle and sheep: selection of non-linear model

Five mathematical models were compared to select the most satisfactory model to describe digesta kinetics of solids and fluids in the gastrointestinal tract of buffaloes (Mediterranean bulls), cattle (Friesian bulls) and sheep (Delle Langhe rams) given food at maintenance level, according to a Latin-square arrangement for four consecutive periods of 21 days. Chromium mordanted alfalfa hay and cobalt-ethylenediamine tetraacetic acid were used as nonabsorbable markers and were administered through the rumen cannula in a single dose. Four different isonitrogenous diets (N × 6·25 = 140 g/kg dry matter) with different concentrate:forage ratios (12·5:87·5, 25:75, 37·5:62·5, 50:50) were used.

Faecal chromium and cobalt concentration curves were fitted with five non-linear models: three gamma (G2, G3, G4) age-dependent one-compartment, one gamma age-dependent/age-independent two-compartment (G2G1) and one multicompartment (MC).

Wilcoxon tests on residual sums of squares of the different models for solids showed that MC and G4 gave a better fit than G2G1, G2, G3 for all the data and within the species. The comparison of MC v. G4 did not show any significant difference (P > 0·05) for all the data computed together or within each species. Nevertheless, MC had a higher number of curves with lower residual sums of squares in comparison with G4 and was also able to produce estimates of digesta kinetics in the second compartment.

The cobalt excretion curves for fluids, considering all the data, and only within sheep, showed G4 as the best fitting model. When G4 was compared with other models no significant differences were recorded either for cattle: G4 v. G2 (F = 0·6645), G4 v. G2G1 (P = 0·0620) and for buffalo: G4 v. G2 (P = 0·1575), G4 v.G3(P = 0·0796) and G4 v. G2G1 (P = 0·1641).

It is concluded that the multicompartment model (MC) and G4 model were the best fits for solids and for fluids respectively.

Selection of barley grain affects ruminal fermentation, starch digestibility, and productivity of lactating dairy cows

The objective of this study was to evaluate the effects of 2 lots of barley grain cultivars differing in expected ruminal starch degradation on dry matter (DM) intake, ruminal fermentation, ruminal and total tract digestibility, and milk production of dairy cows when provided at 2 concentrations in the diet. Four primiparous ruminally cannulated (123 +/- 69 d in milk; mean +/- SD) and 4 multiparous ruminally and duodenally cannulated (46 +/- 14 d in milk) cows were used in a 4 x 4 Latin Square design with a 2 x 2 factorial arrangement of treatments with 16-d periods. Primiparous and multiparous cows were assigned to different squares. Treatments were 2 dietary starch concentrations (30 vs. 23% of dietary DM) and 2 lots of barley grain cultivars (Xena vs. Dillon) differing in expected ruminal starch degradation. Xena had higher starch concentration (58.7 vs. 50.0%) and greater in vitro 6-h starch digestibility (78.0 vs. 73.5%) compared with Dillon. All experimental diets were formulated to supply 18.3% crude protein and 20.0% forage neutral detergent fiber. Dry matter intake and milk yield were not affected by treatment. Milk fat concentration (3.55 vs. 3.29%) was greater for cows fed Dillon compared with Xena, but was not affected by dietary starch concentration. Ruminal starch digestion was greater for cows fed high-starch diets compared with those fed low-starch diets (4.55 vs. 2.49 kg/d), and tended to be greater for cows fed Xena compared with those fed Dillon (3.85 vs. 3.19 kg/d). Ruminal acetate concentration was lower, and propionate concentration was greater, for cows fed Xena or high-starch diets compared with cows fed Dillon or low-starch diets, respectively. Furthermore, cows fed Xena or high-starch diets had longer duration that ruminal pH was below 5.8 (6.6 vs. 4.0 and 6.4 vs. 4.2 h/d) and greater total tract starch digestibility (94.3 vs. 93.0 and 94.3 vs. 93.0%) compared with cows fed Dillon or low-starch diets, respectively. These results demonstrate that selection of barley grain can affect milk fat production and rumen fermentation to an extent at least as great as changes in dietary starch concentration.

Soyhulls as an alternative feed for lactating dairy cows: a review

Dairy producers use soyhulls, a byproduct of soybean processing, to replace either grain or forage in diets of lactating dairy cows. In view of the nutritional and economical value of soyhulls it is anticipated that this practice will continue to increase in popularity among nutritionists and producers of ruminant animals. This paper reviews information regarding the nutritional value of soyhulls and the effects of feeding this alternative feed on ruminal fermentation, nutrient digestion and utilization, and performance of dairy cows. Soyhulls can replace corn grain to supply about 30% of the dry matter (DM) in high-grain diets without negatively affecting either the fermentation or digestion of nutrients in the gastrointestinal tract or the performance of dairy cows. Additionally, data suggest that soyhulls might successfully replace forage to supply < or = 25% of the DM in diets of dairy cows when the supply of effective fiber, which includes a chemical and a physical component, remains adequate after including the hulls. However, caution should be exercised when data from different studies are extrapolated to practical situations because the response to feeding soyhulls appears to be largely affected by the type of carbohydrate being replaced by soyhulls; the amount, type, and physical form of the dietary forage; and the incidence of either negative or positive associative effects before and after the addition of soyhulls to the original diet. Unfortunately, the paucity of data from experiments in which soyhulls constituted more than 25 to 30% of the dietary DM restricts the ability to identify the maximum amount of soyhulls that can be used in diets of dairy cows. Information from studies in which > or = 25 to 30% of dietary DM supplied as either cereal grains or forages are replaced with soyhulls is needed to better understand and predict the production of dairy cows fed diets containing the hulls. This knowledge is essential for maximizing the use of soyhulls in diets for dairy cows.

Granulated polyamide as external marker to estimate total faecal excretion of grazing cattle in extensive management systems

Granulated polyamide (PA) was tested for use as an external marker to estimate faecal DM (FDM) excretion of Zebu cattle (Bos indicus). The study was conducted in Mali, using seven and eighteen animals respectively in four field trials and six indoor experiments. Cattle ate fresh or dry pasture vegetation and half the animals were additionally supplemented with crop byproducts. Gelatine capsules containing 35, 40 or 45 g PA were administered orally at 12 h intervals. Estimates of FDM were based on the average marker concentration in faeces and were correlated with the actual excretion measured by total faecal collection. The pre-measurement period required to establish equilibrium for regular marker dosing was determined at 4 d. Except for diets with a N content of less than 9.26 g/kg organic matter, marker recovery averaged 98.1 (SE 0.93)% (n 62), and was not influenced by diet composition and the quantity of feed ingested (P > 0.05). Estimates of FDM based on average PA concentrations in faecal samples were correlated to the actual excretion with r 0.98 (n 62; P < or = 0.001). Since the PA concentration in individual faecal grab-samples is not correlated with either sample mass or sampling time, accurate estimates of FDM require a grab-sampling schedule that covers the 24 h day. However, estimates of FDM were found to be acceptable if calculations are based on the average PA concentration in the sub-total of samples collected during the day or during night respectively (r 0.95, n 29; P < or = 0.001 in both cases). It is concluded that the use of PA marker is a simple and inexpensive method resulting in reliable estimates of FDM. Since sophisticated analytical procedures are not required to recover PA in faecal samples, the marker is particularly suitable for application in extensive grazing systems and in studies conducted in less-developed countries.

Ability of mathematical models to predict faecal output with a pulse dose of indigestible marker

The aim of the work was to compare the faecal output and digestibility estimated by two mathematical approaches with the actual amount of faeces excreted or feed digested by Simmental cows. Experimental data (intakes and digestibility measured over 5 d) and faecal Cr concentrations (measured at 0, 4, 8, 12, 16, 24, 32, 48, 56, 72, 96, 120 and 144 h after a pulse dose of Cr-mordanted forage) were collected from published experiments and fitted to a multicompartmental (MC) model and a gamma age-dependent (AD) model. From a statistical point of view, the MC model was very satisfactory while the AD model produced lower r2 and higher SE values and reached satisfactory statistical values only for higher DM intakes (lactating animals). The MC model produced higher correlations with the digestibility values while the AD model generated better correlations with the intake data; DM intake and digestibilities were more highly correlated with the model's parameters than neutral-detergent fibre terms. The regression between the estimated faecal outputs obtained with the two models showed an intercept close to 0 (P > 0.05) and angular coefficients near 1; there was a good correspondence of the estimates especially for the lowest values of output. The r2 values of the regressions were 0.800 and 0.829 for the MC and AD models respectively and their SE were 2.93 and 2.63. The ability of the two models to predict faecal output and digestibility was very similar, independent of the statistical accuracy of fitting the Cr-concentration data. The results indicate that variation of Cr concentration is the result of the entire digestive process, i.e. dilution and passage, which interact in a competitive or associative way.

The influence of density and size of particles on rumination and passage from the reticulo-rumen of sheep

Plastic particles with different densities (0.92, 1.03, 1.22 and 1.44 g/ml) and sizes (1, 10 and 20 mm) were introduced into the rumen of fistulated sheep kept on a roughage diet. The forestomach was emptied 12 and 24 h after the introduction of the particles, and the contents were replaced by the same amount of rumen contents without plastic particles. The proportions of particles which left the reticulo-rumen (RR) during the experimental period were determined by collecting the faeces during the following 5 d. Non-ruminated particles were separated from the dried RR contents and from the faeces. Large particles were ruminated independently of particle size and density within the investigated range. After 12 and 24 h, 59 and 81% respectively of the particles initially introduced were comminuted due to rumination. During the 12 h period about four times as many particles with a density of 1.44 g/ml passed from the RR into the omasum compared with particles with a density of 0.92 or 1.03 g/ml. Three to ten times more 1 mm particles were excreted than originally-large particles (10 and 20 mm). Particles introduced with an original size of 10 or 20 mm were recovered mostly comminuted in the faeces. In a further experiment the rumens of eight sheep were emptied and filled with a buffer solution. Plastic particles (10 g) of each length (1, 5, 10 and 20 mm; all with a density of 1.03 g/ml) were introduced into the ventral rumen. Sedimentation of particles was prevented by gassing the solution in the RR. Of the initially introduced particles, 31.9, 25.4, 12.7 and 1.5% of the 1, 5, 10 and 20 mm long particles respectively left the RR within 4 h. It is concluded that rumination of particles is independent of particle density and size within the tested range. The probability of particles leaving the RR increases with the higher particle density and with the smaller size. If particle sedimentation is prevented in the RR even 10 mm long particles can leave the RR in considerable amounts.