Digesta Passage Rate Research Articles

Effect of silage dry matter content and rapeseed meal supplementation on dairy cows: 2. Rumen fermentation and digesta passage rate

The effects of direct-cut and wilted silage with or without rapeseed meal (RSM) supplementation on rumen fermentation and digesta passage rates were studied in a 4×4 balanced Latin square experiment with four multiparous cows. The dry matter (DM) and crude protein (CP) degradabilities of silages were determined in sacco. RSM supplementation replaced 16% of the oat–barley concentrate mixture. The daily concentrate amount was 10 kg. Silages were given ad libitum. The effective degradabilities of dry matter and protein (EPD) were higher ( p<0.001) in direct-cut silage but wilted silage had higher ( p<0.001) content of rapidly degradable protein. Rumen ammonia concentration was higher with direct-cut silage (10.16 versus 8.47 mmol/l, p<0.01), reflecting higher CP content and EPD. Rumen pH and total volatile fatty acid (VFA) concentration in rumen were not affected by silage type, and the differences in molar proportions of rumen VFA’s were small. The proportion of propionate tended to be higher ( p<0.10) with wilted silage, whereas the proportion of butyrate was higher (133 versus 128 mmol/mol, p<0.01) with direct-cut silage. The retention time of the digesta particle phase in alimentary tract was shorter ( p<0.05 or better) with wilted silage. Pool mean retention time (PMRT), which illustrates the retention time of particles in rumen, was shorter (34.0 versus 28.3 h, p<0.05) with wilted silage. Similarly, retention time of particles in the rumen pool of particles small enough to leave the rumen tended to be shorter ( p<0.10) with wilted silage. RSM supplementation tended to increase ( p<0.10) rumen ammonia concentration and decreased the molar proportion of rumen butyrate (132 versus 127 mmol/l, p<0.05). The retention time of particles in pool, which illustrates the rate of particle break down in the rumen, was shorter ( p<0.10) with RSM. In conclusion, the ruminal retention time of particles was shorter with wilted silage. This may affect silage digestibility negatively.

Effect of forage to concentrate ratio in the diet on ruminal fermentation and digesta flow kinetics in sheep offered food at a fixed and restricted level of intake

AbstractThe effects of four diets differing in their for age: concentrate ratio (80:20, 60:40, 40: 60 and 20:80; g/100 g fresh matter) on rumen characteristics, digestibility and digesta flow kinetics were investigated. Alfalfa hay was used as forage and concentrate was composed of barley, soya-bean meal and maize. Diets were prepared by mixing all ingredients and offered to the animals as complete diets. Eight mature Merino sheep, each fitted with a rumen cannula, were offered 1·055 kg dry matter per day of the corresponding diet over two experimental periods. The daily evolution of ruminai pH, volatile fatty acids (VFA) and ammonia nitrogen (N) concentrations were measured. Digestibility was determined by total faecal collection and Cr and Co were used as markers to estimate digesta passage rates. Microbial nitrogen flow at the duodenum (MNDF) was estimated from the urinary excretion of purine derivatives (PD). The apparent digestibility of organic matter increased (P&lt; 0·001) whereas that of all fibrous fractions decreased linearly (P&lt; 0·05) as the proportion of concentrate in the diet increased. Rumen pH decreased linearly (P&lt; 0·001) with increasing proportions of concentrate but total VFA concentrations were unaffected by changes in the diet (P&gt; 0·05). Both liquid and solid digesta outflow rates from the rumen decreased quadratically (P&lt; 0·01) as the proportion of concentrate in the diet increased. The urinary excretion of total N, urea-N and ammonia-N was unaffected (P&gt; 0·05) by changes in the diet. In contrast, the daily urinary excretion of both allantoin and total PD increased quadratically (P&lt; 0·05) with increasing proportions of concentrate. Consequently, the estimated MNDF increased linearly (P&lt; 0·001) from 9·9 g/day on the high forage diet to 14·5 g/day on the high concentrate diet.

Postprandial heat increment does not substitute for active thermogenesis in cold-challenged star-nosed moles (Condylura cristata).

The postprandial increase in metabolic rate associated with consuming, assimilating and excreting a meal is often termed the heat increment of feeding (HIF). The metabolic heat production of star-nosed moles, Condylura cristata, held at thermoneutrality was monitored for 4 h following a single 10 min session of feeding on a ration consisting of 0 g (controls), 3.5 g or 10 g of earthworms. Coefficients for metabolizable energy digestibility and digesta passage rate of earthworms fed to C. cristata were also determined. We then tested whether feeding-induced thermogenesis substitutes partially or completely for thermoregulatory heat production in these animals exposed to sub-thermoneutral air temperatures (9-24 degrees C). A single feeding on earthworms had both short- and long-term effects on the metabolic rate and respiratory exchange ratio of C. cristata. The observed short-term (0-65 min) rise in metabolic rate, assumed to be associated primarily with the physical costs of nutrient digestion, absorption and excretion, was similar to the calculated mean retention time (66.7+/-7.8 min; mean +/- s.e. m., N=5) of this species. This component of the HIF represented 2.9 % of the food energy ingested by moles fed a single 3.5 g (13.21 kJ) meal of earthworms and 1.4 % of the food energy ingested by moles fed a single 7.5 g (28.09 kJ) meal of earthworms. At all test temperatures, resting metabolic rate typically remained above fasting levels for 1-4 h following ingestion of the high-protein earthworm diet. This protracted rise in metabolic rate, presumably associated with the biochemical costs of amino acid oxidation/gluconeogenesis and ureagenesis, averaged 12.8 % of the metabolizable energy and 8.7 % of the gross energy intake. Despite the potential thermoregulatory benefit, we found no evidence that biochemical HIF substitutes for facultative thermogenesis in star-nosed moles exposed to low air temperatures.

The effect of method of forage preservation on the protein degradability and microbial protein synthesis in the rumen

Direct cut silage (DC), formic acid treated silage (FA), wilted silage (W), highly wilted silage (HW) and hay (H) were prepared from the same parental grass. In one experiment, the five diets were fed to sheep and the efficiency of rumen microbial protein synthesis and rumen digesta passage rate were determined. In a second experiment, organic matter and protein degradability characteristics in the rumen of sheep were determined by the in sacco method. Microbial protein supply (MN) was significantly higher ( P < 0.05) in HW and H (12.63 and 12.77 g N kg −1 DM intake) than in DC, FA and W (11.09, 11.32 and 10.89 g N kg −1 DM intake). MN tended to be negatively correlated to the concentration of total acids in the feeds ( r = −0.73, P > 0.1). There were no significant differences in the digesta passage rates. Effective protein degradability (EDG CP) were 855, 800, 796, 750 and 677 g kg −1 for DC, FA, W, HW and H, respectively. Effective organic matter degradability (EDG OM) for DC, FA, W, HW and H were 552, 517, 526, 484 and 522 g kg −1, respectively. A synchrony index ( I S), which takes into account the rate of degradation of nitrogen and organic matter, was calculated. The index varied significantly among the different preservation treatments (0.22, 0.34, 0.28, 0.35 and 0.87 in DC, FA, W, HW and H, respectively). MN tended to be positively correlated to I S ( r = 0.72, P > 0.1). Estimated metabolizable protein concentrations were 53.4, 59.9, 57.1, 70.3 and 75.3 g kg −1 DM for DC, FA, W, HW and H, respectively. It was concluded that, based on the protein value, hay was better than silages and wilted silages better than unwilted silages ensiled without an additive. The protein value of silages can be increased by the formic acid treatment prior to ensiling.

In situ incubation sequence and its effect on degradation of food components when measured in the caecum of ponies

Abstract Three experiments were conducted to investigate the effect of bag incubation sequence on the degradation of food components in situ in the caecum of mature, caecally fistulated Welsh-cross pony geldings (mean live weight 278 kg) offered hay ad libitum. In experiment 1 a fibre-based commercial horse concentrate was incubated in situ using a forward (3, 5, 16, 8, 24, 48 h) or reverse (48, 24, 8, 16, 5, 3 h) incubation sequence. Dry matter (DM), crude protein (CP), neutral-detergent fibre (NDF) and acid-detergent fibre (ADF) degradation coefficients and calculated effective degradability (ED) values were determined. In experiment 2 unmolassed sugar-beet pulp (USBP), hay cubes (HC), soya hulls (SH) and a 2: 1 mixture of oat hulls: naked oats (OHNO) were incubated in situ as for experiment 1. In experiment 3 unprocessed barley (UB), micronized barley (MB), extruded barley (EB) and dehydrated grass (DHG) were incubated in situ according to slightly different forward or reverse incubation sequences of (2, 4, 6, 12, 8, 24, 48 h) and (48, 24, 8, 4, 12, 6, 2 h) respectively. In experiments 2 and 3 only DM degradation parameters were studied. Of the three starch-based foods studied in experiment 3 (UB, MB and EB), incubation sequence did not significantly P &gt; 0·05) affect any of the degradation parameters examined. Conversely however, of the six fibre-based foods which were examined across the three experiments, incubation sequence did significantly P &lt; 0·05) affect in situ degradation parameters in the commercial horse concentrate in experiment 1, the SH food in experiment 2 and the DHG food in experiment 3. Depending on the food or food constituent studied (i.e. DM, CP, NDF or ADF) degradation coefficients a, b, c and a + b along with ED values calculated at fractional outflow rates of 0·05 and 0·025 could all be statistically different CP &lt; 0·05) according to whether a forward or reverse incubation sequence was used. It is postulated that this effect is related to the basic digestive physiology of the equine caecum which is small, digesta passage rate through it is fast and digesta volumes can vary considerably. These factors may interact to create a considerable degree of non-uniformity within the caecal digesta pool in which in situ bags are incubated. Consequently, it is recommended that in future in situ experiments in the equine hindgut, animals are offered ad libitum diets in an attempt to minimize variation within the caecum. It is also recommended that in situ experimental protocols incorporate more than one incubation sequence when the degradation parameters of fibrous foods are studied in equids.

Eficiência de utilização de nutrientes em novilhas das raças Canchim e Nelore e cruzadas Canchim-Nelore

O objetivo deste trabalho foi estudar a eficiência de utilização de nutrientes por novilhas em crescimento das raças Canchim (CA) e Nelore (NE) e 1/2 Canchim + 1/2 Nelore (CANE) em três dietas: mantença, relação volumoso:concentrado: (RVC) de 75:25 (Teste 1); dieta para ganhos de 700 g/animal/dia, RVC de 60:40 (Teste 2); e dieta para ganhos de 1200 g/animal/dia, RVC de 40:60 (Teste 3). Vinte e quatro novilhas foram usadas por teste, oito de cada grupo genético. Cada teste compreendeu três etapas: a) desempenho, de 90 dias, em que foram determinados o consumo de matéria seca e o ganho em peso diário dos animais; b) digestibilidade aparente das dietas e balanço de nitrogênio dos animais; e c) taxas de passagem da fase líquida da digesta. Os animais de CA, NE e CANE tiveram desempenho semelhante, dentro de cada dieta, para todas as variáveis analisadas.

Effect of Dietary Protein, Fiber, and Digesta Passage Rate on the Duration and Concentration of Escherichia coli 0157:H7 Shed by Cattle

Infection with E. coli O157:H7 is the most common cause of human hemorrhagic colitis in North America. Cattle are a reservoir for this human pathogen and individual animals are sporadically and transiently colonized. We hypothesize that pre-harvest dietary management may reduce the risk of E. coli O157-positive animals entering our food chain. The effect of dietary energy, fiber, and digesta passage rates on the duration and concentration of fecal E. coli 0157 was determined. Sixteen healthy Charlais x Hereford or Holstein heifers were acclimated to one of four diets: a finishing diet (high in energy and low in fiber), a growing diet (low in energy and high in fiber), chopped alfalfa (small particle size), or long alfalfa (large particle size). A single oral dose of 1010 colony forming-units of E.coli 0157 was administered to each animal and fecal samples were cultured for the bacteria by selective-enrichment twice a week for the duration of the study. No significant difference in the shedding of 0157 by animals on the finishing or growing diet was observed. However, withholding feed of either type, for 24 hours, did increase the concentration of the bacteria in the fecal material of about half of the animals. A significant correlation (p value=0.008) was observed between digesta passage rate and the duration of fecal E. coli 0157. Animals with slower passage rates of 2 to 3 % per hour cleared E. coli 0157 from their intestinal tract in 10 days or less compared to animals with digesta passage rates of 4 to 5 % per hour who shed the bacteria for more than 69 days. These results show that cattle diet influences the duration and concentration of fecal E. coli O157:H7.

The effect of different fibre components on growth rate, nutrient digestibility, rate of digesta passage and hindgut fermentation in domesticated rabbits.

Trials were conducted to study the effect of dietary fibre on performance and nutrient digestibility in growing rabbits. The basal diet was supplemented with 12% cellulose, pectin, lignin, or alfalfa, in four different treatments. Twenty-four 4-week-old California male rabbits were randomly allocated into four groups and placed in individual cages. The lignin supplement severely affected both feed intake and performance, pectin second, with dietary cellulose having the least effect. Dietary lignin significantly decreased the digestibility of crude protein, gross energy and dry matter content (P < 0.05). Rabbits on the pectin supplemented diet digested dry matter, crude fibre and neutral detergent fibre (NDF) better (P < 0.05) than other treatment groups. On the other hand, rabbits in the lignin group digested crude fibre, acid detergent fibre (ADF) and NDF significantly less well than rabbits in other groups (P < 0.05). Dietary lignin also significantly decreased the caecal concentration of volatile fatty acids (VFA, P < 0.05) but did not significantly affect the molar ratios of the VFAs among treatment groups. The turnover rate of the marker, chromic oxide, in the gastrointestinal (GI) tract of rabbits was 64.94, 51.81, 44.05 and 29.59 h in the pectin, alfalfa, lignin and cellulose treatment groups, respectively. The rate of turnover in the digestive tract significantly influenced digestibility of fibre components but did not significantly influence caecal fermentation.

Gut morphology and rate of passage of fungal spores through the gut of a tropical rodent, the giant white-tailed rat (Uromys caudimaculatus)

Gut morphology and rate of digesta passage through the gut in captive giant white-tailed rats (Uromys caudimaculatus) were investigated. Rate of passage was measured using a solute marker (Co-EDTA), a marker of large particles (Cr-mordanted plant cell walls) and spores of the ectomycorrhizal fungus Pisolithus spp. The mean retention time (MRT) of fungal spores in the whole gut (48.4 ± 6.0 h), was long in comparison to that found in other rodents of similar body mass and was intermediate to MRT of the solute marker (45.4 ± 8.8 h) and the large particle marker (55.5 ± 7.2 h). Thus, retention of spores is likely to be little affected by being free or attached to pieces of ingested fruiting bodies. The stomach is unilocular and hemiglandular and contains a large fundic diverticulum lined entirely by non-glandular squamous epithelium. The significantly longer MRT for the large particle marker than the solute marker suggests that some selective retention of particles takes place, probably in the fundic diverticulum of the stomach. We suggest that the large fundic diverticulum may function in storage and possibly increased digestive efficiency of starchy food items, and in retaining spores, especially when still attached to fruiting bodies.

Effects of alpha2-adrenoceptor antagonists on metabolic processes of swine: II. Nitrogen balance responses.

We studied the effects of alpha2-adrenoceptor antagonists (A2AA) on nitrogen (N) partitioning. The diets fed contained 19.8% CP and 1.15% lysine. Pigs were fed the diet as a percentage of BW equaling approximately 90% of voluntary intake. In Trial 1, pigs (n = 11/treatment) were fed a basal diet and injected s.c. at 8-h intervals for 11 d with saline, RX821002 (25 mg/injection), or cimaterol (.6 mg/injection). Compared to saline-treated pigs, urinary N, as a percentage of N eaten, decreased among pigs injected with RX821002 (15%, P < .05) or cimaterol (17%, P < .05). In Trial 2, pigs got saline (n = 6) or 25 mg RX821002 (n = 6) as s.c. injections three times daily, or they were fed a diet containing 150 ppm RX821002 and injected thrice daily with saline (n = 6) for 11 d. The RX821002 lowered apparent DM and N digestibility (P < .05). Compared to controls, RX821002 lowered urinary N, as a percentage of N eaten, 15 and 18% when given by injections or per os, respectively, but effects were not significant. Trial 3 evaluated the effects of RX821002 fed at levels of 0 (n = 6), 37.5 (n = 5), 75 (n = 6), or 150 ppm (n = 6). Contrasts showed linear dose-dependent decreases in gain and apparent N digestibility (P < .05). Compared to untreated controls, urinary N, expressed as a percentage of N consumed, decreased 2, 12, and 10% among pigs fed diets with 37.5, 75, or 150 ppm RX821002, respectively, but effects were not significant. Trial 4 compared N balance in pigs (n = 6/treatment) fed basal diet or diet with 100 ppm RX821002 to that of pigs fed diets with 25 or 100 ppm yohimbine. Treatments reduced apparent N and DM digestibility (P < .05). Urinary N, as a percentage of N consumed, decreased 16 (P > .05), 18 (P < .05), and 24% (P < .05) for 100 ppm RX821002, 25 ppm yohimbine, or 100 ppm yohimbine, respectively. Data from Trials 2, 3, and 4 from control pigs (n = 18) or pigs fed A2AA (all A2AA sources and doses; n = 41) were pooled and analyzed. Feeding A2AA decreased apparent N and DM digestibility (P < .01). The fact that fecal moisture content was higher in pigs fed A2AA suggests rate of digesta passage increased and offers an explanation for reduced N and DM digestibility in treated pigs. Despite adverse effects of A2AA, efficiency of postabsorptive N metabolism increased. As a percentage of N consumed and compared to control pigs, urinary N decreased 15% (P < .01) and retained N increased 12% (P < .05) in animals fed A2AA. Data from these studies show net efficiency of N metabolism is improved in swine given A2AA.

Napier or groundnut hay as supplements in diets of sheep consuming poor quality natural pasture-hay 2. Effect on intake and rumen digesta kinetics

Three experiments, each of a 5 × 5 Latin square design, were carried out using sheep to assess the effect of supplementing poor quality natural pasture (veld) hay with graded levels of napier or groundnut hay on feed intake, rumen fermentation, digesta pool size and passage rate. In experiment 1, napier hay was fed at 0 g day −1 , 100 g day −1 , 200 g day −1 , 300 g day −1 or ad libitum. In experiment 2 the same levels of feeding were used with groundnut hay, while in experiment 3, napier and groundnut hay were each fed at 0 g day −1 , 150 g day −1 or 300 g day −1 to enable a direct comparison of the two supplemental forages. All the forages used were chopped to a particle size of about 1 cm prior to feeding. The veld hay was supplemented with 1% urea and was always offered ad libitum. The forage supplements were fed separately. In all the experiments, the forage supplements increased total feed intake, digestibility and concentration of ammonia and volatile fatty acids in the rumen. Incubation of veld hay in the rumen of sheep given napier and groundnut hay as supplements or as sole feeds, showed no effect on degradation pattern including rate of degradation. Rumen digesta pool size was not altered, but fractional outflow rate was increased by supplementation. The increase in feed intake was therefore largely facilitated by an increase in digesta passage rate.

Effect of tannins on galliform cecal partitioning.

Winter diets of ruffed grouse (Bonasa umbellus) and other galliformes are high in tannins. We fed quebracho, a condensed tannin, to ruffed grouse and found no effect on dry matter intake or body mass at levels up to 6% of the diet. However, a high-fiber diet with 8% quebracho resulted in reduced dry matter intake and body mass loss. Grouse could not tolerate a diet with 8% tannic acid, a hydrolyzable tannin, which caused a large reduction in dry matter intake and body mass. Northern bobwhite (Colinus virginianus) and ruffed grouse responded to dietary quebracho tannin by increasing the proportion of digesta that was excreted from the ceca. In the northern bobwhite, 59%-76% of the tannin recovered from the feces was in cecal feces. There was no difference in average passage rates of liquid and fiber digesta, although variation was high in tannin-fed birds. The role of the ceca in handling tannin requires further investigation.

Use of Bacillus stearothermophilus spores as a marker for estimating digesta passage rate from the rumen in cattle

Abstract Chromium-mordanted NDF, Co-EDTA and a Bacillus stearothermophilus spore (BSS) suspension were administered through rumen cannulae to three steers and six mature heifers with an average weight of 659 ± 6 kg in a completely randomized design experiment. Cattle were fed bromegrass hay (13.6% CP) at maintenance level (11.70 kg DM d−1). Rumen contents were collected at intervals up to 120 h following administration of markers. Aliquots of rumen digesta solids and liquids were analyzed for Cr and Co concentration and Bacillus stearothermophilus colony-forming units (CFU) after overnight incubation on nutrient agar plates at 65 °C. Rates of passage were calculated as the regression coefficient of the natural logarithm of Cr, Co concentration or Bacillus stearothermophilus CFU in either solid or liquid fractions versus time. Data showed that liquid rate of passage from the rumen estimated by BSS (7.38% h−1) was lower (P

FASTING‐INDUCED CHANGES TO THE PHARMACOKINETIC BEHAVIOUR OF ALBENDAZOLE AND ITS METABOLITES IN CALVES

The influence of fasting on the bioavailability and disposition kinetics of albendazole (ABZ) and its metabolites in cattle was investigated. ABZ (10 mg/ kg) was given by intraruminal (i.r.) (Experiment 1) and intravenous (i.v.) (Experiment 2) administration to Holstein calves either fed ad libitum (control) or subjected to a 48 h fasting period (fasted group) prior to treatment. The rate of passage of digesta through the gastrointestinal (GI) tract was evaluated by measurement of cobalt faecal excretion following the oral administration of the sodium-cobalt-ethylendiamine-tetracetic acid complex to calves subjected to the feeding conditions above described. Jugular blood and abomasal fluid (via cannula) samples were collected over 120 h post-treatment; samples were analysed by high performance liquid chromatography (HPLC) for ABZ, ABZ sulphoxide (ABZSO) and ABZ sulphone (ABZSO2). Fasting the animals prior to the i.r. treatment resulted in pronounced modifications to the plasma and abomasal fluid disposition kinetics of ABZ and its metabolites. A greater extent of GI absorption with significantly higher CmaX (150%) and AUC (310%) values for ABZSO in plasma, was observed in fasted compared to fed animals following the i.r. administration of ABZ. Extended detection of ABZ metabolites resulting in significantly longer plasma t 1/2el and MRT was also obtained in fasted compared to fed calves. These results correlated with the substantially enhanced availability of ABZ and its metabolites (AUCs over 200% greater) in the abomasal fluid of the fasted animals. Fasting did not induce changes to the plasma disposition of either ABZ or its metabolites after the i.v. treatment. The digesta passage rate, measured by the amount of cobalt excreted in faeces, was significantly lower in fasted compared to animals fed ad libitum. A delayed GI transit time that decreases the rate of passage of the drug down the digestive tract, may have accounted for enhanced ABZ dissolution and absorption in fasted compared to fed calves. The findings reported in this article show that fasting prior to treatment notably affects the bioavailability and disposition kinetics of ABZ and its metabolites in cattle.

Comparison of Chewing Time and Passage Rates of Digesta in Wethers Fed Timothy (Phleum pratense L.) Hay Harvested at Three Different Maturities

Comparison of Chewing Time and Passage Rates of Digesta in Wethers Fed Timothy (Phleum pratense L.) Hay Harvested at Three Different Maturities

Changes in factors affecting the rate of digesta passage during pregnancy and lactation in sheep fed on hay.

The objective of this study was to assess feed intake and digesta passage characteristics in five Blackhead ewes fed hay ad libitum during pregnancy [I: d 60-80 post conceptionem (p conc); II: d 105-125 p conc; III: d 128-148 p conc] and lactation [IV: d 10-30 post partum (pp); V: d 35-55 pp]. During pregnancy, feed intake and rumination activity increased. The rumen fluid volume and the daily number of A-cycles did not change significantly. The mean retention time (MRT) of the fluid and particle markers in the reticulorumen (RR) and distal to the RR decreased by 14-32%. During lactation, the rumen fluid volume increased as compared to pregnancy by about 15%. Daily feed intake peaked during period V (83.7 g DM/kg BW0.75). The MRT of particle markers in the RR increased as compared with late pregnancy. Both during pregnancy and lactation, the increased passage rate of digesta was achieved predominantly by an increased amount of digesta passing through the reticulo-omasal orifice during each opening. Sieving of forestomach contents and faeces revealed that the breakdown rate of large feed particles did not limit digesta passage.

Feeding napier hay as supplement to sheep given poor quality natural pasture hay: effects of level of napier hay supplement and inclusion of urea in the basal diet on intake and digestibility

Three experiments were carried out using lambs to assess the effect of level of napier hay and urea supplements on the utilization of poor quality natural pasture (veld) hay. In all the experiments the lambs were given graded levels of napier hay as supplements to the basal diet of veld hay. In Experiment 1, the veld hay was not supplemented with urea; in Experiment 2, the veld hay was supplemented with 1% urea while in Experiment 3, the veld hay was supplemented with 1% or 2% urea. In all the experiments napier hay supplements increased total feed intake and in vivo digestibility of the diet ( P < 0.05). High levels of napier supplementation tended to reduce the intake of veld hay below the level achieved on the unsupplemented control diet. However this decrease in veld hay intake was not as much as anticipated had the napier hay (corrected for its digestibility) simply replaced veld hay. Increasing the level of urea from 1 to 2% did not increase feed intake or digestibility or alter the pattern of substitution of veld hay by the napier. Across treatments, there was some evidence that the gain in the intake of veld hay resulting from napier supplementation was greater when urea was not added to the veld hay. In all the experiments, the increase in food intake was associated with an increase in faecal dry matter excretion suggesting that the increase in feed intake was facilitated by an increase in digesta passage rate. These results confirm that forage supplements are effective in increasing the utilization of poor quality forages and the response to the napier supplements was not entirely due to increasing nitrogen intake.

Dietary, environmental and microbiological aspects of methane production in ruminants

Methane gas is produced in the rumen by methanogenic bacteria as a metabolic end product. The energy released by bacteria in the process of methane formation can be used for bacterial cell formation. Methane formation acts as an electron sink into which the hydrogen from all ruminal microorganisms drains, allowing a higher yield of adenosine triphosphate. Factors such as the type of carbohydrate in the diet, level of feed intake, digesta passage rate presence of ionophores or lipids in the diet, and ambient temperature influence the emission of methane from ruminants. Methanobrevibacter spp. appear to be the major methanogens in the rumen, but it is likely that phytogenetic analyses will identify new species. The biochemical reduction of carbon dioxide to methane is well defined, and it has been shown that interspecies hydrogen transfer between methanogens and ruminal bacteria prevents the accumulation of reduced nucleotides and the inhibition of feed digestion. The development of strategies to mitigate methane production in ruminants, without causing a negative impact on ruminant production, continues to be a major challenge for ruminant nutritionists and microbiologists. Enhancement of the reduction of carbon dioxide to acetate and direct genetic manipulation of methanogens are two interventions that may further reduce methane losses of ruminants. Key words: Methane, diet, ruminant, microbiology, methanogen

Excretion of infused 14C-steroid hormones via faeces and urine in domestic livestock

Abstract The aim of this comparative study was to gain more information about the excretion of steroid hormones in farm animals. This should help to establish or improve non-invasive steroid monitoring procedures, especially in zoo and wildlife animals. Over a period of 4 h the 14C-steroid hormones (3.7 MBq) progesterone (three females), testosterone (three males), cortisol and oestrone (two males, two females) were infused intravenously in sheep, ponies and pigs. Faeces were collected immediately after defecation. Urine was sampled via a permanent catheter in females and after spontaneous urination in males. A total of 88 ± 10% (mean ± SD) of the administered radioactivity was recovered. Considerable interspecies differences were measured both in the amounts of steroid metabolites excreted via faeces or urine and the time course of excretion. Progesterone and oestrone in ewes, and progesterone in mares were excreted mainly in the faeces (over 75%). The primary route of excretion of all other 14C-steroids was via the urine but to a different extent. In general, sheep showed the highest degree of faecal excretion and pigs the least. The highest radioactivity in urine (per mmol creatinine) was observed during the infusion or in one of the next two samples thereafter, whereas in faeces it was measured about 12 h (sheep), 24 h (ponies) or 48 h (pigs) after the end of the infusion. Thereafter the radioactivity declined and reached background levels within 2–3 weeks. In faeces, steroid metabolites were present mainly in an unconjugated form, but in blood and urine as conjugates. Mean retention time of faecal radioactivity suggested that the passage rate of digesta (duodenum to rectum) played an important role in the time course of the excretion of steroids. The information derived from this investigation could improve the precision of sampling as well as the extraction of steroids from the faeces. Furthermore, the study demonstrates that it should be possible to establish methods for measuring faecal androgen and cortisol metabolites for assessing male reproductive endocrinology and stress in animals.

The effect of incubation sequence on in situ degradation of concentrate feed components in the caecum of ponies

Previous work as shown that incubation sequence has no effect on the degradation profile of feeds in the rumen of cattle and sheep. However, compared to the rumen the equine caecum is small, digesta passage rate through it is fast and total digesta volumes can vary widely. Consequently, this experiment examines the effect of bag incubation sequence on degradation co-efficients in situ in the equine caecum.Four caecally fistulated Welsh cross pony geldings (approx LW 250 kg) were offered ad libitum grass hay (DM: 938, CP: 70; NDF: 728) plus 30 g/h/d of a horse mineral supplement. Duplicate incubation bags (monofilament polyester, 6.5 x 20 cm, 41 um pores, 16 mg/cm2 sample size) containing a commercial horse concentrate (DM: 918, CP:151, NDF: 403) were incubated in the caecum for fixed times according to both a forward (0,3,5,16,8,24,48) or reverse (48,24,8,16,5,3,0) incubation sequence.