Cr-mordanted Fibre Research Articles

No size-dependent net particle retention in the hindgut of horses.

Sieve analyses of hindgut contents of horses as well as observations in horses where plastic markers had been applied to a caecal cannula suggested that there may be a discrimination by particle size in the passage or retention of digesta. Here, we performed a similar experiment with five caecum-cannulated horses (562 ± 31 kg) fed a constant amount (6.81 kg dry matter/day) of grass hay. Passage markers representing the liquid (Co-EDTA) as well as the particulate digesta phase (Yb-undefined; Cr mordanted fibre 1-2 mm; Ce-mordanted fibre 8 mm) were given as a pulse-dose into the cannula to measure their mean retention times (MRT). The MRTs were compared by repeated-measurements analysis of variance. The MRT in the hindgut was 22.2 ± 2.4 h for Co, 25.0 ± 3.4 h for Yb, 26.2 ± 1.6 h for Cr and 26.3 ± 1.5 h for Ce. Whereas differences between the particle marker MRTs were not significant (padj. > 0.05), significant differences were observed between the solute marker Co and each of the particle markers Cr and Ce (padj. < 0.009). The results confirm the well-known significant, albeit small, difference in MRT in horses between the fluid and the particle digesta phase, and corroborate another recent study that used a combination of whole, marked hay and individual marker analysis in different particle size fractions of the faeces, which also did not detect a selective retention of any particle size class.

Individual differences in digesta retention and their relation to chewing in cattle-A pilot investigation.

While information on individual differences in digesta mean retention time (MRT) might be interesting when selecting phenotypes for digestive efficiency, MRT measurements are prohibitively labour-intensive for large-scale application. Therefore, more easily measured proxies of MRT might be helpful. We used the opportunity of an experiment applying saliva stimulant in cattle to investigate the effect of different individual chewing behaviour on fluid and particle MRT with a consistent diet. Four non-lactating cattle (670-850 kg body mass [BM]) were used in a 4 × 4 Latin square design, treated with the saliva stimulant pilocarpine in dosages of 0, 1, 2.5and 5 mg/kg BM per day. The cattle were fed hay with dry matter intake (DMI) assigned according to their metabolic body weight. MRT in the whole gastrointestinal tract (GIT), the reticulorumen (RR) and the distal tract were measured using Co-EDTA, Cr-mordanted fibre and La-mordanted fibre as markers representing fluid, small particles (2 mm) and large particles (1 cm), respectively. The chewing behaviour was measured via noseband pressure sensor and expressed as chewing frequency (chews per time) and chewing intensity (chews per DMI), both for total chewing (ingestion plus rumination) and rumination chewing alone. The animals differed considerably in chewing behaviour and MRT measures. BM did not show a significant effect on chewing behaviour and MRT measures, though it tended to negatively correlated to total chewing intensity. Chewing intensity exerted a significant negative influence on MRT of fluid and particles in the RR, which was not the case for chewing frequency. Chewing frequency showed a significant relationship with MRT of large particles in the GIT. We suggest that chewing behaviour could influence MRT in two ways: (i) by affecting saliva production via the masticatory-salivary reflex and subsequently, the fluid inflow to the RR; (ii) by contributing to particle size reduction. Should the link between chewing behaviour and MRT be corroborated in larger studies, chewing measures, with their large interindividual variation, could emerge as an easy-to-measure proxy for MRT characteristics.

Biological implications of longevity in dairy cows: 1. Changes in feed intake, feeding behavior, and digestion with age

Milk production strategies focusing on longevity and limited use of concentrate are receiving increasing attention. To evaluate such strategies, knowledge of the development with age of animal characteristics, particularly digestion, is indispensable. We therefore investigated the development of feed intake, chewing activity, and digestion in 30 lactating Brown Swiss cows (876–3,648 d old) and 12 heifers (199–778 d old). We also studied whether age effects were exhibited differently in animals selected from herds subjected for 11 yr either to a forage-only or to a forage-concentrate feeding regimen. Forages consisted of grass hay (the only feed for heifers), corn silage, and grass pellets. Measurements lasted for 8 d, where amounts and composition of feeds, feces, and milk were recorded and analyzed. Ruminal pH data and eating and rumination activity were assessed by pH sensors put into the rumen and halter-mounted noseband sensors. The mean retention time of feed particles was assessed using Cr-mordanted fiber and data were used to calculate dry matter gut fill. Data were subjected to regression analyses with age and feeding regimen as explanatory variables, and body weight, milk yield, and proportion of hay in forage as covariates. This allowed separating age-related changes of body weight and milk yield from independent age effects and correcting for differences in preference for individual forages. In cows, organic matter intake increased with age (from slightly below to above 20kg/d), as did mean retention time and gut fill. Digestibility of organic matter did not show a clear age dependency, but fiber digestibility had a maximum in cows of around 4 to 6 yr of age. Ruminal pH and absolute eating and rumination times did not vary with cow age. Young and old cows chewed regurgitated boluses more intensively (60–70 times) than middle-aged cows (about 50 times). Effects of feeding regimen were small, except for fiber intake and rumination time per unit of intake, owing to the different fiber content of the diets. No significant interactions between age and feeding regimen were found. Heifers spent more time eating and ruminating per unit of feed than cows, which resulted in a high fiber digestibility. Irrespective of the feeding regimen tested, older cows maintained intake and digestion efficiency with longer retention times and chewing rumination boluses more intensively. The results support efforts to extend the length of productive life in dairy cows.

Using portable X-ray fluorescence (pXRF) to determine fecal concentrations of non-absorbable digesta kinetic and digestibility markers in sheep and cattle

Concentration of indigestible markers in feces is routinely used to estimate the digestibility or rate of passage of feed through the gut. Current procedure for measuring fecal marker concentrations is an acid digest before analysis using inductively coupled plasma optical emission spectroscopy (ICP). Portable X-ray fluorescence (pXRF) spectroscopy uses short wavelength X-rays to excite sample material and generate characteristic elemental emissions proportional to the concentration of the element present in ground fecal material. The aim of this study was to measure fecal concentrations of Co, Cr, Ti, and Yb digesta marker by both ICP and pXRF and determine any correlation between the two methods, thereby assessing the potential of using pXRF as a marker analysis method. Silica (Si) concentrations in fecal and feed samples were also measured using both methods. Cattle and sheep feces and various feed samples collect from four separate studies were analyzed for concentrations of Co (CoEDTA), Cr (Cr mordanted fibre), Ti (TiO2), Yb (Yb(III)acetate), and Si using ICP and pXRF. Regression analysis used to assess the relationship between ICP and pXRF determined fecal concentrations indicated strong linear relationships (P<0.01) between pXRF and ICP estimates of Co (r2=1.00), Cr (r2=0.95), Ti (r2=0.97), Yb (r2=0.94), and Si (r2=0.88). All curves were validated using a second set of independent fecal samples. A full set of total collection fecal samples for six sheep were also analyzed by pXRF for Co and Cr (digesta kinetics), and Si (digestion) marker concentrations. These fecal Co and Cr concentrations were used to estimate digesta mean retention times (MRT) and compared to estimated digesta MRT from the same sheep using Co and Cr marker concentrations determined by ICP analysis. No differences in estimated MRT were found when using either analytical method. Silica concentrations from the same fecal samples as determined by pXRF were used to determine the rate of DMD for each animal. When compared to apparent DMD for the same animals as determined using feed DM intake and fecal DM output collected during the total collection, no differences were again found using either analytical method. The results indicate that pXRF can be used as an alternative to standard ICP procedure, obviating the need for acid digestion, reducing cost and time; and may also offer an alternative analytical method for determining livestock DM digestibility.

Triiodothyronine influences digesta kinetics and methane yield in sheep

Methane yield from ruminants is positively correlated with mean retention time (MRT) of digesta, which is known to be influenced by the hormone triiodothyronine (T3).We hypothesised that a decrease in the MRT in the rumen in response to administration of a T3 solution to sheep would reduce their methane yield. To test this hypothesis, 10 mature Merino wethers were injected with T3 (300 µg) on two different protocols (daily; n = 5 and every second day; n = 5) and the effect on daily methane yield, digesta MRT, DM digestibility, rumen volatile fatty acid concentrations, microbial protein output and plasma T3 concentrations studied. Compared with when injected with saline (control), injection of sheep with T3 every second day resulted in decreased methane yield (P &lt; 0.05) and lower acetate (P &lt; 0.001), butyrate (P &lt; 0.001) and propionate (P &lt; 0.01) concentrations in the rumen. MRT of digesta, derived from faecal excretion of CoEDTA and Cr-mordanted fibre, were reduced in the total tract (P &lt; 0.001) and hindgut (P &lt; 0.01) but not in the rumen (P &gt; 0.05). DM digestibility was not affected by injection of T3 every second day but water intake (P &lt; 0.05) and urine output (P &lt; 0.01) were increased. When sheep were injected with T3 daily, changes were only observed in plasma T3 concentration (P &lt; 0.001) and volume of CO2 produced (P &lt; 0.05). The results indicate that increasing plasma concentration of the thyroid hormone T3 within physiological levels reduces digesta retention time, especially retention time in the hindgut and leads to a reduction in enteric methane yield. Further work is warranted to assess whether plasma T3 concentrations may be indicative of enteric methane yield.

Digesta retention time in roe deer Capreolus capreolus, as measured with cerium-, lanthanum- and chromium-mordanted fibre

Studies on particle retention time in ruminants are commonly conducted utilizing chromium (Cr) and/or a lanthanide bound to feeds. Both types of markers have different chemical properties which potentially bias estimates of digesta retention—their combined use is therefore a topic of ongoing discussion. In order to evaluate the suitability of two lanthanides for studies assessing the passage kinetics of different-sized particles, we measured the mean retention time in roe deer with cerium (Ce) and lanthanum (La) labelled to the same particle length and compared it to Cr-mordanted fibre of the same size. We expected a simultaneous excretion of Ce- and La-labelled fibre, but a delayed excretion of Cr-mordanted fibre compared to the other markers. In this study, the mean retention times of Ce- and La-labelled fibre did not differ significantly, and Cr-mordanted fibre was retained on average 5 h longer than Ce and La. Despite the limitation of the small sample size, Ce and La showed the same excretion pattern and can therefore be recommended as mordants in studies assessing passage kinetics of different particle sizes.

Role of dietary fibre source and meal size on the ileal transit of digesta in growing pigs

Dietary fibre and meal size may regulate motility and digestive transit time through the gastrointestinal tract. We studied the effect of diets containing either white rice or oats (as low and high fibre sources, respectively), offered at two levels of feeding (41.4 and 82.4 g feed/kg W 0.75·day), on the kinetics of the rate of passage of digesta through the gastrointestinal tract until the ileum (pGIT) in pigs. Eight 45-kg pigs fitted with a T-cannula at the terminal ileum were used following a double Latin square design. The rate of digesta passage, lag time (T lag) and mean retention time (MRT) through the ileal cannula were measured for 36 h using titanium dioxide (TiO 2) and Cr-mordanted fibre as indigestible markers for whole digesta and the fibrous phase of digesta, respectively. The effects of cereal source and feeding level and their interaction on the pGIT digesta kinetics parameters were analyzed for each marker. As expected, TiO 2 had a shorter MRT than Cr-mordanted fibre (7.0 h vs 10.4 h; P < 0.001), indicating that they followed different phases of digesta. Oats resulted in faster rate of digesta passage (P < 0.05) than rice for Cr-mordanted fibre, and in longer T lag (P < 0.05) and MRT (P = 0.05) for TiO 2. No effect of feeding level or interaction between feeding level and cereal source were observed for any of the markers (P > 0.1). It is concluded that the cereal source (i.e. fibre content), but not the feeding levels tested affect the pGIT kinetics of the rate of digesta passage in pigs.

White Sweetclover (Melilotus albus) and Narrowleaf Hawksbeard (Crepis tectorum) Seed Germination after Passing through Moose

AbstractWhite sweetclover and narrowleaf hawksbeard are nonindigenous invasive plant species in Alaska that are rapidly spreading, including into areas that are otherwise free of nonindigenous plants. There has been concern that native moose could be dispersing germinable seed from these plants after ingestion. To address this concern, a study was conducted involving tame moose at the University of Alaska Fairbanks Agriculture and Forestry Experiment Station, Matanuska Experiment Farm, Palmer, AK. Objectives were to determine if seeds from these two plant species could survive mastication and digestive passage through moose, whether this passage impacted seed germination, and whether seed passage rates were the same as similar sized Cr-mordanted fiber. In this study, narrowleaf hawksbeard seed rarely survived mastication and digestion with only five seedlings recovered from 42,000 germinable seed fed to the moose. About 16% of germinable white sweetclover seed (3,595 of 22,000) fed to the moose produced seedlings. Most of the sweetclover seedlings came from feces produced 2 and 3 d after feeding. In two moose, sweetclover seedlings were grown from fecal material that was passed 11 d after feeding, raising the possibility that seeds could be transported long distances after ingestion. Cr-mordanted fiber passage did not closely follow seedling producing seed, possibly because time in the rumen might reduce seed germination. Once roadsides in Alaska become infested with white sweetclover, moose can then serve as a transport vector of these weeds into river channels and floodplains, which are distant from roads. This information will impact white sweetclover management programs and alert land managers to the potential for other instances of wildlife-mediated seed dispersal.

Comparative investigations on digestion in grazing (Ceratotherium simum) and browsing (Diceros bicornis) rhinoceroses

Rhinoceroses represent the largest extant herbivores with extensive dietary specialization for plant groups like browse (black rhino Diceros bicornis) or grass (white rhino Ceratotherium simum). However, it is not clear to what extent such diet selection patterns are reflected in adaptations of digestive physiology of the respective feeding types. In this study, feeding trials with four black and five white rhinos were conducted in four zoos. The animals had ad libitum access to the same batch of grass hay (second cut; neutral detergent fiber (NDF) 63% dry matter (DM), crude protein 10.2% DM). Total intake, fecal N content, in vitro digestibility of NDF residues of feces, fecal particle size and mean retention time (MRT) of particles (Cr-mordanted fiber; 1–2mm) and fluid (Co-EDTA) were quantified. The average daily DM intake was 70±12g/kg BW0.75 for white and 73±10g/kg BW0.75 for black rhinos. In the in vitro fermentation test fecal NDF residues of black rhinos resulted in higher gas productions at fermentation times of 12 to 24h, indicating that white rhinos have a superior capacity to digest NDF. Average MRT for fluids and particles was 28±4h and 43±5h in white and 34±4h and 39±4h in black rhinos. The selectivity factor (SF=MRTparticle/MRTfluid) was higher for white (1.5±0.2) than for black rhinos (1.2±0.1) (p=0.016). In a comparison of 12 ruminant and 3 rhino species, SF was correlated to percentage of grass in diet (R=0.75). Mean fecal particle size was higher in white (9.1±1.94mm) than in black rhinos (6.1±0.79mm) (p=0.016). The results demonstrate differences between white and black rhinos in terms of retention times and fiber digestibility. The more selective retention of particles by the white rhino corresponds with the higher digestion of fiber measured indirectly. Furthermore there is indication for a general pattern of high SF in grazing ruminants and rhinos. The difference in fecal particle size between both rhino species might be due to the considerable difference in body weight.

Studies on digestive physiology and feed digestibilities in captive Indian rhinoceros (Rhinoceros unicornis)

We performed intake, digestibility and ingesta passage studies in 11 Indian rhinoceroses (Rhinoceros unicornis) from four zoological institutions, using total faecal collection for the quantification of faecal output. The regularly fed zoo ration of roughage and concentrates (ration RC) and a roughage-only ration (ration R) were used; the roughage source differed between the facilities and comprised grass hay, grass silage, straw and lucerne hay. Dry matter intake ranged between 0.8 and 1.3% of body weight on ration RC and 0.5-1.2% on ration R. Digestibility coefficients achieved were similar to those reported for horses on diets of comparable composition. Endogenous losses as determined by linear regression analysis were within the range reported for horses. Measurements of faecal volatile fatty acids, faecal lactate and faecal pH also showed similarity to similar measurements in horses. The mean retention times of fluids (Co-EDTA) and particles (Cr-mordanted fibre <2 mm) in the whole gastrointestinal tract averaged 42 and 61 h, respectively, and were the longest ever recorded in a monogastric ungulate with this marker system. The results suggest that the horse is a useful model animal for designing diets for Indian rhinoceroses. Why digestive parameters are similar between these species in spite of enormous differences in body weight and retention times remains to be answered.

Nutrition of captive lowland anoa (Bubalus depressicornis): a study on ingesta passage, intake, digestibility, and a diet survey

Members of the Bovini genus are classified as grazers. Smaller species of ruminants are not expected to be able to digest particularly fibrous diets and are more often classified as intermediate feeders or browsers. Anoas (Bubalus spp.) are interesting in this respect as they are the smallest representatives of the Bovini, being only 10-20% of the body weight of other species of the same genus. A feeding trial was carried out with four lowland anoas (Bubalus depressicornis) at London Zoo, investigating diet digestibility by total fecal collection and passage rates by the simultaneous administration of a fluid (Co-EDTA) and a particle (Cr-mordanted fibre <2 mm) marker. The diet consisted of legume hay, dairy cow pellets, browse, fruits, and vegetables. The achieved digestibility coefficients averaged 70±4% for dry matter and 57±7% for cell walls (NDF). Mean retention times for the total gastrointestinal tract were 25±4.1 hr for fluid and 39±6.7 hr for particles, respectively. The ratio of forestomach particle:fluid retention was 2.14±0.40. Additional information regarding anoa diets in captivity was collected through a survey targeting all institutions that have anoas in their collection currently. Suitability of the provided diet was evaluated using the ratio of unstructured:structured feeds (unstructured feeds pellets, grains, produce; structured feeds=roughage, browse) on a dry matter basis and an assumed complete consumption of offered unstructured diet items, with only the remaining intake capacity being met by structured items. The use of this ratio reliably predicted one facility that reported chronic diet-related problems. As other ruminants, anoas should receive a diet with restricted amounts of concentrates and fruits. The comparatively high fibre digestibility and the high selective particle retention in the forestomach suggest a classification of an intermediate/grazing ruminant.

Matua bromegrass hay for mares in gestation and lactation.

Matua bromegrass hay (Bromus willdenowii Kunth) is a high quality forage, but its value for mares during gestation and lactation is not well known. Intake, rate of passage, performance, and reproduction by gestating and lactating Quarter Horse mares fed the hay was investigated. In this experiment, 12, 2- to 12-yr-old gravid mares (mean BW = 553 kg, SD = 36) were fed Matua hay (CP = 11.5%) or alfalfa hay (Medicago sativa L.) (CP = 15.4%) for variable days prepartum (mean 59.9 d; SD = 23.5) and for 70 d postpartum. Matua and alfalfa hay were fed as the roughage portion of the diet with a grain supplement. Mares, blocked by age, expected date of foaling, and BW, were assigned randomly within blocks to treatments (six mares per treatment). Forage type did not affect intake, gestation length, birth weight, number of foals, foal weight gain, day of first postpartum ovulation, cycles per conception, or pregnancy rate at 70 d. On d 1, milk from mares fed alfalfa hay contained less (P < 0.03) CP than milk from mares fed Matua hay. Milk CP decreased (P < 0.01) in all mares over time. In a separate experiment, voluntary intake and rate of passage of Matua (CP = 15.5%), alfalfa (CP = 24.9%), and Timothy (Phleum pratense L.) (CP = 4.1%) hays were determined in nine 2-yr-old pregnant mares (mean BW = 447 kg; SD = 21). Diets were 100% forage. Timothy hay did not meet CP requirements for mares. Voluntary intake of alfalfa hay was higher (P < 0.01) than Matua hay. Intake of Timothy hay was lower (P < 0.01) than the mean of alfalfa and Matua hay. Rate of passage offorage was measured by passage of Cr-mordanted fiber. Passage rate and retention time did not differ between Matua and alfalfa hay; however, the retention times of Matua and alfalfa hays were shorter (P < 0.01) than for Timothy hay. Our results indicate that Matua hay is a forage that can be used safely for mares during gestation and early lactation and for their young foals.

Comparison of the In Situ and In Vivo Intestinal Disappearance of Ruminally Protected Methionine

We designed a switchback expriment to compare the intestinal disappearance of ruminally protected Met determined in situ or in vivo over three consecutive periods. Four nonlactating Holstein heifers (477±36kg) with cannulae in the rumen, duodenum, and ileum were fed a diet based on timothy silage to meet requirements for maintenance (dry matter intake = 8.72±0.15kg). A total of 16 bags, containing 1.5g of ruminally protected Met, were incubated in the rumen (4.5h) of each cow and transferred to an acid-pepsin solution to simulate the abomasum (2.5h). Following each incubation, bags were recovered and three bags were dried at 55°C and analyzed for Met. Remaining bags were introduced directly into the duodenal or ileal cannula for the in situ method, while for the in vivo method, the content of remaining bags was transferred into gelatin capsules before their introduction in the duodenal or ileal cannula. Spot samples of digesta were collected during a 96-h period, with Co-EDTA and Cr-mordanted fiber used as indigestible markers to estimate in vivo digestibility. The disappearance of Met in the small intestine determined in vivo tended to be higher than in situ (74.45 vs. 43.65±1.79%). Our results indicate that when used to assess intestinal availability of ruminally protected Met, the mobile nylon bag technique can underestimate the true bioavailability of Met.

Effect of dietary fiber concentration on apparent digestibility and digesta passage in non-human primates. II. Hindgut- and foregut-fermenting folivores

Two test diets with different acid detergent fiber (ADF) concentrations (15% ADF, 30% ADF) were fed to seven adult hindgut- and seven adult foregut-fermenting primates. Apparent digestibilities (%) of dietary dry matter (DM), gross energy (GE), and fiber components (neutral detergent fiber [NDF], ADF, hemicellulose [HC], and cellulose [C]) were measured. Rates of digesta transit (TT1) and retention (RGIT) times were assessed using acetate beads, Co-ethylenediaminetetraacetic acid, and Cr-mordanted fiber as markers. Apparent digestibilities (%) of components of the 15ADF and 30ADF diets, respectively, by hindgut versus foregut fermenters were 69.3 and 61.7 versus 81.2 and 76.7 for DM, 68.5 and 61.5 versus 80.9 and 75.6 for GE, and 44.8 and 47.4 versus 77.1 and 74.7 for NDF. No significant differences in TT1 or RGIT between dietary treatments or markers were detected. The role of plant fiber in maintaining the health and normal function of the gastrointestinal tract in captive leaf-eating primates is discussed. Zoo Biol 18:537–549, 1999. © 1999 Wiley-Liss, Inc.

Effect of dietary fiber concentration on apparent digestibility and digesta passage in non-human primates. I. Ruffed lemurs (Varecia variegata variegataandV. v. rubra)

Two test diets with different fiber concentrations (15% acid detergent fiber [ADF], 30% ADF) were fed to five adult female ruffed lemurs (Varecia variegata). Apparent digestibility (%) of dry matter (DM), gross energy (GE), and fiber components (neutral detergent fiber [NDF], ADF, hemicellulose [HC], and cellulose [C]) were measured. Rates of digesta transit (TT1) and retention time (RGIT) were assessed using acetate beads, Co-ethylenediaminetetraacetic acid and Cr-mordanted fiber. Apparent digestibilities (%) of components of the 15ADF and 30ADF diets, respectively, were 51.0 and 41.7 for DM, 47.0 and 39.7 for GE, and 20.4 and 20.7 for NDF. TT1 was approximately 2.7 hours. RGIT was 3.8 hours. No differences in TT1 or RGIT between dietary treatments or marker types were detected. Results of this study support anecdotal observations that Varecia variegata have a limited capacity to utilize plant cell wall constituents as a significant energy source, when compared with more folivorous prosimans. Zoo Biol 18:529–536, 1999. © 1999 Wiley-Liss, Inc.

Comparative digestibility and digesta flow kinetics in two breeds of sheep

AbstractA study was conducted to compare apparent digestibility and digesta flow kinetics in the whole digestive tract in two breeds of sheep (Churra and Merino) offered alfalfa hay at about maintenance. Ten mature sheep (five Churra and five Merino) each fitted with a rumen cannula were used in the study. Apparent digestibility was determined by total faecal collection. Liquid (Co-EDTA) and solid (Cr-mordanted fibre) markers were used to estimate rumen volumes and digesta flows. There were no significant differences between Churra and Merino sheep either in dry-matter or fibre apparent digestibility (P &gt; 0·05). Liquid and solid passage rates did not differ between breeds and the estimated total mean retention times were similar for both genotypes. The volume of liquid in the rumen was proportionately 0·14 greater in Churra than in Merino sheep, although the difference was not significant. Estimated saliva secretion was greater in Churra (11·6 (s.e. 0·77) I/day) than in Merino sheep (10·5 (s.e. 0·72) I/day) but the difference did not reach statistical significance. Solid contents of the rumen did not differ between breeds. Rumen particle density was lowest at 2 h after feeding and remained stable at other sampling times, with no significant differences between breeds. There were no significant differences between breeds in the urinary excretion of total purine derivatives but urinary excretion of allantoin and microbial nitrogen supply tended to be higher in Merino than in Churra sheep (P &lt; 0·20). This was attributed to the smaller rumen pool size of Merino (8·0 (s.e. 0·62) kg) compared with Churra sheep (9·2 (s.e. 0·63) kg). The study indicated that there were no apparent breed differences between Churra and Merino sheep in digestibility and digesta passage when they were given a good-quality forage at a low level of intake.

Effect of forage to concentrate ratio on comparative digestion in sheep, goats and fallow deer

AbstractThree ewes, three female goats and three male fallow deer, aged between 7 and 12 months and weighing 24·0 to 32·2 kg, were used in this experiment to outline the main differences in digestion among the three species. Dietary treatments were three diets with three forage: concentrate ratios of 10: 90, 50: 50, and 90:10 and two different feeding levels (45 and 90 g/kg M0·75per day). The three diets were given to the three animals of each species in a Latin-square design; the two levels of feeding were compared ivithin diet in each period of the Latin square. The diet selected, apparent digestibility, and rumen retention time of Cr-mordanted neutral-detergent fibre were significantly different among species and dietary treatments. Interactions between species and dietary treatments were also significant for all the above variables. Sheep showed the highest intakes and apparent digestibilities of the forage-rich diets, and the longest rumen mean retention times. Goats tended to select diet components, despite allowance of diets being limited, and had lower food intakes than sheep. Apparent digestibility of forage-rich diet was also lower. Rumen mean retention times were shorter and less influenced by dietary treatments. Fallow deer had an apparent digestibility of forage-rich diets which was even lower than that of goats. Food intake was similar to that of sheep, with no evidence of selection. Rumen mean retention time was shorter than that of goats.

Effects of diet and chemical form of selenium on selenium metabolism in sheep.

The effects of diet composition and chemical form of Se on intestinal flow, absorption, and retention of Se were determined in sheep by the balance technique and by disappearance of Se from sites along the gastrointestinal tract with reference to dual-phase digesta markers. Six sheep with ruminal and duodenal cannulas were used in a crossover design with a split-plot arrangement of the Se isotope treatments. Sheep were fed a forage (alfalfa hay)-based (.37 mg Se/kg) or concentrate (barley)-based (.27 mg Se/kg) diet at 90% of ad libitum intake. Selenium stable isotopes (enriched [77Se]yeast, enriched [82Se]selenite) and fluid (Co-EDTA) and particulate (Cr-mordanted fiber) markers were administered simultaneously into the rumen four times daily for 7 d, and total collections of feces and urine were made every 24 h for these and the following 7 d. A larger proportion (51 to 61%) of the Se tracers flowing to the duodenum was associated with the particulate fraction, mainly as bacteria-associated Se, than with the fluid fraction. The [82Se]selenite was more available (P < .05) for absorption and retention than [77Se]yeast, indicating that inorganic chemical forms of Se are as available to the ruminant as organic forms of Se commonly found in feedstuffs. Selenium absorption and retention were greater (P < .05) in sheep receiving the concentrate-based diet than in sheep receiving the forage-based diet. Thus, the availability of Se from inorganic and organic sources in sheep seems to be influenced by diet composition.

Digestibility and gastro-intestinal transit time of diets containing different proportions of alfalfa and oat straw given to Thoroughbreds, Shetland ponies, Highland ponies and donkeys

AbstractA series of 4 × 4 Latin-square digestibility trials was carried out to determine whether there were any differences between different types of equid in their ability to digest diets containing different levels of fibre and protein. The equids (Thoroughbreds, Highland ponies, Shetland ponies and donkeys) were offered one of four molassed diets in turn and these contained different proportions of alfalfa and oat straw: 1·0:0, 0·67:0·33, 0·33:0·67, 0:1, respectively. The apparent digestibility of dry matter (DM), organic matter (OM), gross energy (GE), crude protein (CP), acid-detergent fibre (ADF) and neutral-detergent fibre (NDF) were estimated. The rate of passage of the different diets was measured using Cr-mordanted fibre (Cr-fibre) and Co-ethylene diamine tetra acetic acid.All animals digested the components of the high-fibre diets less well than those of the low-fibre diets (P &lt; 0·001 for DM, OM, GE, CP and ADF). Donkeys digested fibre more effectively than the other equids (F &lt; 0·01 for ADF and NDF). The gastro-intestinal transit time of the high fibre diets was significantly less than that for the low fibre diets (P &lt; 0·001) and donkeys retained food residues longer than the other equids (P &lt; 0·01).

Prediction of voluntary dry-matter intake, digestible dry-matter intake and growth rate of cattle from the degradation characteristics of tropical foods

AbstractAn experiment using twenty-five bulls aged between 1 and 1·5 years and weighing 117 to 209 kg was carried out to estimate voluntary dry-matter intake (DMI), digestible dry-matter intake (DDMI), dry-matter apparent digestibility (DMD) and growth rate when the bulls were given 18 foods available from smallholder dairy farms on the slopes of Mount Kilimanjaro, Tanzania. The animals were randomly allocated to five groups of five animals each. Foods were then randomly allocated to the five groups for four periods of 60 days each during which DMI was measured. A digestion trial was made at the completion of each measurement. Outflow rates of solids from the rumen were determined by giving the animals 200 g Cr-mordanted fibre of each food and grab faecal samples were obtained. Dry matter (DM) degradation characteristics of the foods were determined in sacco in the rumen of three Boran steers fed on guatemala grass and the water soluble fraction (A) was measured. DMI varied from 2·2 kg for banana pseudostem to 4·77 kg/day for urea-treated maize stover. DMD ranged from 549 for untreated maize stover to 767 g/kg DM for banana pseudostem and growth rate ranged from 72 for banana leaves to 275 glday for urea-treated maize stover. Potential degradability (defined by A + B) (where B is the insoluble fraction degradable with time) for the DM ranged from 617 g for banana leaves to 874 g/kg DM for banana pseudostem and the degradation rate (c) ranged from 0·0168 for banana leaves to 0·0440 per h for green maize stover. The separate use of degradation characteristics A, B and c in multiple regression to predict DMI, DDMI, and growth rates gave better results than when A + B or (A + B) + c were used. Multiple correlation coefficients between degradation characteristics and DMI, DDMI and group rate were r– 0·90, 0·93 and 0·93 respectively. The results indicate that DMI, DDMI and growth rates by cattle fed on crop residues and forages could be predicted well using the rumen degradation characteristics of the foods.