Effects of expander-treating a barley-based concentrate on ruminal fermentation, bacterial N synthesis, escape of dietary N, and performance of dairy cows

Three primiparous dairy cows in early lactation with cannulas in rumen, duodenum and ileum were used in a 3×3 Latin square design to study effects of expander treatment of a barley-based concentrate. The concentrate was either pelleted at 75–80°C or expander treated at 125–130°C prior to pelleting. The diets consisted of 6.7 kg DM of grass silage and 10 kg DM of (1) 100% pelleted, (2) 50% pelleted and 50% expanded or (3) 100% expanded concentrate. The diets were offered as a mixed ration in four equal meals daily. Ruminal fermentation, bacterial N synthesis, duodenal, ileal and faecal flow of nutrients, and animal performance were monitored. Expander treatment numerically increased ruminal digestion of starch, which explained the observed increase in ruminal VFA concentration and the lowered ruminal pH (P<0.05). The proportion of butyrate in rumen liquid increased, whereas the proportion of propionate decreased in the expanded compared to the pelleted treatment (P<0.05). Expander treatment tended to increase rumen volume and rumen NDF pool size. Ruminal digestion of NDF was numerically lower in the expanded than in the pelleted treatment. No differences in bacterial N synthesis or efficiency of synthesis were observed among treatments. Expander treatment numerically increased the duodenal flow of non-ammonia N (NAN) and amino acid N (AAN), and seemed to increase the flow of non-ammonia non-bacterial N (NANBN) to the duodenum to a similar extent as was indicated by nylon bag studies. Milk production and milk fat and protein content were increased by the expander treatment (P<0.05), indicating that expander treatment increased the supply of nutrients for milk production.     

Nutritional Value of Moss for Arctic Ruminants: a Test with Muskoxen

Abstract: Although moss is commonly found in the feces of arctic herbivores, we do not know the digestible value of this forage for ruminants. We compared grass hay (Bromus sp.) with moss (Hylocomium splendens, Tomenthypnum nitens) from 2 locations in Alaska, USA: Cape Krusenstern National Monument and Fairbanks. We evaluated forages by digestion in ruminally fistulated muskoxen (Ovibos moschatus) by suspending forages in polyester bags before and after the rumen was acclimated with moss for 15 consecutive days. Ruminal degradation was not affected by acclimation to moss. Hay lost dry matter during 48 hours of ruminal incubation (-49%), whereas moss gained dry matter (+44-57%). Incubated moss gained nitrogen (+435-680%), as well as fiber (+18%), and one moss gained ash (+121%). Mass gained by moss in the rumen was probably due to the combined effect of microbial colonization and adsorption of fibrous particles onto the sponge-like matrix. We evaluated postruminal degradation of forages by incubation in acid-pepsin. Ruminally incubated mosses lost little nitrogen in acid-pepsin even though ruminally incubated hay lost 23% nitrogen on acid digestion. Consumption of moss during winter may be a net cost of selecting plants within moss communities when lichens and graminoids are scarce. Moss in feces may, therefore, indicate low availability of favored foods for muskoxen and other arctic ruminants that are confined to small winter ranges. Increasing concentrations of moss in the feces and, thus, the diet of muskoxen may alert wildlife managers to shifts in winter range quality or forage access due to changing snow conditions.     

Trophic relationships of muskoxen (Ovibos moschatus) and reindeer (Rangifer tarandus) on Wrangel Island

Seasonal changes in the diets of muskoxen and reindeer on Wrangel Island have been studied. The results are discussed with respect to consumption of basic forage plants depending on the feeding strategies and biotopic distribution of the two species.     

Surface enlargement in the rumen of free-ranging muskoxen (<Emphasis Type="Italic">Ovibos moschatus</Emphasis>)

The intraruminal papillation pattern indicates the degree of rumen contents stratification and is related to the feeding niche of a ruminant. Muskoxen (Ovibos moschatus) display a variety of morphophysiological adaptations typical for grazers. We investigated the intraruminal papillation of 22 free-ranging muskoxen from five different months by comparing the surface enlargement factor both between seasons and between individual rumen regions. The seasonal pattern of rumen papillation indicated a distinct seasonality in food quality. The intraruminal papillation indicated a moderate degree of rumen contents stratification typical for intermediate feeders. The nutritional ecology of muskoxen is characterised by specific morphophysiological adaptations to a grass-dominated diet that nevertheless allow extensive seasonal use of browse forage.     

Ruminal fermentation and fill change with season in an arctic grazer: responses to hyperphagia and hypophagia in muskoxen (Ovibos moschatus)

We studied castrated adult muskoxen fed a standard diet of grass hay and supplement throughout the year to determine seasonal changes in digesta passage, fill, and fermentation without the confounding effects of reproductive demands or changes in food quality. Although food intake increased by 74% between spring and autumn, mean retention times of fluid and particulate digesta markers were maintained between seasons in both the rumen (9-13 h) and the intestines (27-37 h). The rumen contained 84.5% of digesta and accounted for 79% of dry matter digestion in the whole digestive tract. Ruminal fluid space and whole-gut digesta fill increased by 31%-34%, while ruminal rates of in situ degradation increased by more than 100% between spring and autumn for cellulose and hemicellulose. Hyperphagia in autumn was accompanied by increased bacterial counts in ruminal fluid (30%), declines in ruminal pH, and increases in the concentration of fermentation acids (16%) when compared with spring hypophagia. Consumption of fresh hay and supplement increased the concentrations of acids most markedly during winter and spring when bacterial counts were low. Low food intakes in winter and spring may limit the microbial population, whereas hyperphagia in autumn may foster a much more active microflora that requires consistent supplies of substrate. Plasticity of fill and fermentation in muskoxen minimizes winter costs and maximizes nutrients and energy gained from coarse forages in small home ranges throughout the year.     

Differential passage of fluids and different-sized particles in fistulated oxen (Bos primigenius f. taurus), muskoxen (Ovibos moschatus), reindeer (Rangifer tarandus) and moose (Alces alces): Rumen particle size discrimination is independent from contents stratification

Ruminant species differ in the degree that their rumen contents are stratified but are similar insofar that only very fine particles are passed from the forestomach to the lower digestive tract. We investigated the passage kinetics of fluid and particle markers (2, 10 and 20 mm) in fistulated cattle (Bos primigenius f. taurus), muskoxen (Ovibos moschatus), reindeer (Rangifer tarandus) and moose (Alces alces) on different diets. The distribution of dry matter in the rumen and the viscosity of rumen fluids suggested that the rumen contents were more stratified in muskoxen than moose. Correspondingly, as in previous studies, the species differed in the ratio of mean retention times of small particles to fluids in the reticulorumen, which was highest in cattle (2.03) and muskoxen (1.97–1.98), intermediate in reindeer (1.70) and lowest in moose (0.98–1.29). However, the ratio of large to small particle retention did not differ between the species, indicating similarity in the efficiency of the particle sorting mechanism. Passage kinetics of the two largest particle classes did not differ, indicating that particle retention is not a continuous function of particle size but rather threshold-dependent. Overall, the results suggest that fluid flow through the forestomach differs between ruminant species. A lower relative fluid passage, such as in moose, might limit species to a browse-based dietary niche, whereas a higher relative fluid passage broadens the dietary niche options and facilitates the inclusion of, or specialization on, grass. The function of fluid flow in the ruminant forestomach should be further investigated.     

Effect of protein supplementation on ruminal parameters and microbial community fingerprint of Nellore steers fed tropical forages

In tropical regions, protein supplementation is a common practice in dairy and beef farming. However, the effect of highly degradable protein in ruminal fermentation and microbial community composition has not yet been investigated in a systematic manner. In this work, we aimed to investigate the impact of casein supplementation on volatile fatty acids (VFA) production, specific activity of deamination (SAD), ammonia concentration and bacterial and archaeal community composition. The experimental design was a 4×4 Latin square balanced for residual effects, with four animals (average initial weight of 280±10 kg) and four experimental periods, each with duration of 29 days. The diet comprised Tifton 85 (Cynodon sp.) hay with an average CP content of 9.8%, on a dry matter basis. Animals received basal forage (control) or infusions of pure casein (230 g) administered direct into the rumen, abomasum or divided (50 : 50 ratio) in the rumen/abomasum. There was no differences (P>0.05) in ruminal pH and microbial protein concentration between supplemented v. non-supplemented animals. However, in steers receiving ruminal infusion of casein the SAD and ruminal ammonia concentration increased 33% and 76%, respectively, compared with the control. The total concentration of VFA increased (P<0.05) in steers receiving rumen infusion of casein. SAD and the microbial protein concentration did not vary significantly among treatments during the feeding cycle, but mean SAD values were greater in steers supplemented in the rumen and rumen/abomasum. Ruminal ammonia concentration was positively correlated with SAD in animals receiving ruminal infusion of casein. Polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE) analysis revealed low similarity between treatments, animals and time of sample collection. Richness analysis and determination of the Shannon–Wiener index indicated no differences (P>0.05) in species richness and diversity of γ-proteobacteria, firmicutes and archaea between non-supplemented Nellore steers and steers receiving casein supplementation in the rumen. However, species richness and the Shannon–Wiener index were lower (P<0.05) for the phylum bacteroidetes in steers supplemented with casein in the rumen compared with non-supplemented animals. Venn diagrams indicated that the number of unique bands varied considerably among individual animals and was usually higher in number for non-supplemented steers compared with supplemented animals. These results add new knowledge about the effects of ruminal and postruminal protein supplementation on metabolic activities of rumen microbes and the composition of bacterial and archaeal communities in the rumen of steers.     

Comparison of digestive microflora between feedlot cattle with and without infection by<Emphasis Type="Italic">Cryptosporidium andersoni</Emphasis>

The influence of cryptosporidial abomasitis on digestive anaerobic microflora in feedlot cattle with spontaneous Cryptosporidium andersoni colonization of abomasum was shown. Significant differences were found after the cultivation of abomasal content. Scopulariopsis brevicaulis was detected in damaged areas of infected abomasum. PCR analysis of ruminal fluid showed no differences between the two animal groups regarding qualitative composition of anaerobic and facultative anaerobic rumen microflora. The concentration of volatile fatty acids (acetate, propionate, butyrate) and ammonia in the rumen content showed that examined metabolic parameters were within normal limits except for ammonia content, which was higher in infected (291 mg/kg) than in healthy animals (203 mg/kg).     

Effects of dietary forage particle size and concentrate level on fermentation profile, in vitro degradation characteristics and concentration of liquid- or solid-associated bacterial mass in the rumen of dairy cows

This study investigated effects of dietary forage particle size (PS) and concentrate level (CL) on fermentation profiles of particle-associated rumen liquid (PARL) and free rumen liquid (FRL), in vitro degradation characteristics and concentration of bacterial mass attached to the solid or fluid rumen digesta phase in dairy cows. The experiment was a 4 × 4 Latin square design with four late-lactation dairy cows in four 23 day periods. Cows were restrictively fed (17 kg dry matter (DM)/d) one of four diets varying in the theoretical PS (6 and 30 mm) of grass hay and in the levels (approximately 200 and 550 g/kg, DM basis) of a cereal-based concentrate. Proportion of large particles (>6 mm) and the content of structural fibre in the diet increased by reducing dietary CL and, particularly, by increasing hay PS. This effect was not reflected by changes in mean total volatile fatty acid concentration or pH in the rumen. However, cows fed high concentrate diets had pH of 5.28 and 5.37 in PARL at 3 h after the last meal, when fine or long chopped hay was offered. The low pH may indicate a depression of the capacity of PARL to degrade fibre in vitro. Gas production in vitro of concentrate increased with the high concentrate diet at 12 h, suggesting that amylolytic capacity was affected only in early phases of fermentation. In addition, elevating dietary CL appeared to shift ruminal fermentation outputs from propionate to butyrate and valerate. Inclusion of coarsely chopped hay to a high concentrate diet does not appear to bring advantages due to increased structure in restrictively fed dairy cows. In addition, results suggest that the response of pH in PARL is more sensitive to dietary changes (i.e., forage PS and CL) than the response in FRL, and so PARL might be better to evaluate the risk of ruminal disfunction in dairy cows.     

Spatial and temporal variations of the bacterial community in the bovine digestive tract

Aims:  Improved knowledge of the bacterial community of the digestive tract is required to enhance the efficiency of digestion in herbivores. This work aimed to study spatial and temporal variations of the bacterial communities in the bovine digestive tract and their correlation with gut environmental parameters.
Methods and Results:  Rumen content and faeces of five cows were sampled for 3 weeks. In addition, reticulum content was sampled during the third week. Bacterial communities were assessed by studying capillary electrophoresis single-stranded conformation polymorphism (CE-SSCP) profiles of 16S rRNA genes. The bacterial community structure differed between the forestomach and faecal contents. The abundance of several operational taxonomic units changed from week to week. Bacterial community structure of the rumen was correlated to propionic acid and NH₃–N concentrations.
Conclusions:  The bacterial community of the bovine digestive tract varied in space and time.
Significance and Impact of the Study:  The study of the bacterial communities of the digestive tract in herbivores should be widened from the rumen to the large intestine. The amplitude and origin of the temporal variation of the ruminal bacterial community need to be better understood to improve the control of the fermentative activity in herbivores.     

The effects of nitrilotriacetic acid on solubilities of zinc, copper, manganese, and iron in the stomach of sheep.

Four sheep, each prepared with a rumen fistula and reetrant cannula in the proximal duodenum, were used to study the effects of ruminal administration of nitrilotriacetic acid on solubilities of zinc, copper, manganese, and iron in rumen and duodenal digesta. The sheep received a pelleted diet and were dosed with 0, 300, 600 and 1200 microgram of nitrilotriacetic acid per gram of diet via the rumen fistula. Higher concentration of soluble zinc, manganese, and iron but not copper, were found in the rumen of the sheep when they were dosed with nitrilotriacetic acid. The concentrations increased with increasing dose of the acid. However, only the solubilty of iron was increased in the duodenal digesta. Concentrations of soluble zinc and manganese in the rumen increased, whereas copper decreased, during the first 2 h after feeding. The pattern was reversed thereafter. Changes in the concentrations of soluble during 6 h afther feeding were comparatively small. It is concluded that the solubilty of iron in the stomach of sheep is increased by ruminal administration of nitrilotriacetic acid.     

Effects of the acid–base treatment of corn on rumen fermentation and microbiota,inflammatory response and growth performance in beef cattle fed high-concentrate diet

Beef cattle are often fed high-concentrate diet (HCD) to achieve high growth rate. However, HCD feeding is strongly associated with metabolic disorders. Mild acid treatment of grains in HCD with 1% hydrochloric acid (HA) followed by neutralization with sodium bicarbonate (SB) might modify rumen fermentation patterns and microbiota, thereby decreasing the negative effects of HCD. This study was thus aimed to investigate the effects of treatment of corn with 1% HA and subsequent neutralization with SB on rumen fermentation and microbiota, inflammatory response and growth performance in beef cattle fed HCD. Eighteen beef cattle were randomly allocated to three groups and each group was fed different diets: low-concentrate diet (LCD) (concentrate : forage = 40 : 60), HCD (concentrate : forage = 60 : 40) or HCD based on treated corn (HCDT) with the same concentrate to forage ratio as the HCD. The corn in the HCDT was steeped in 1% HA (wt/wt) for 48 h and neutralized with SB after HA treatment. The animal trial lasted for 42 days with an adaptation period of 7 days. At the end of the trial, rumen fluid samples were collected for measuring ruminal pH values, short-chain fatty acids, endotoxin (or lipopolysaccharide, LPS) and bacterial microbiota. Plasma samples were collected at the end of the trial to determine the concentrations of plasma LPS, proinflammatory cytokines and acute phase proteins (APPs). The results showed that compared with the LCD, feeding the HCD had better growth performance due to a shift in the ruminal fermentation pattern from acetate towards propionate, butyrate and valerate. However, the HCD decreased ruminal pH and increased ruminal LPS release and the concentrations of plasma proinflammatory cytokines and APPs. Furthermore, feeding the HCD reduced bacterial richness and diversity in the rumen. Treatment of corn increased resistant starch (RS) content. Compared with the HCD, feeding the HCDT reduced ruminal LPS and improved ruminal bacterial microbiota, resulting in decreased inflammation and improved growth performance. In conclusion, although the HCD had better growth performance than the LCD, feeding the HCD promoted the pH reduction and the LPS release in the rumen, disturbed the ruminal bacterial stability and increased inflammatory response. Treatment of corn with HA in combination with subsequent SB neutralization increased the RS content and helped counter the negative effects of feeding HCD to beef steers.     

Effects of Tasco (a seaweed extract) and heat stress on N metabolism and meat fatty acids in wether lambs fed hays containing endophyte-infected fescue

Wether lambs (n = 27, average BW = 40 kg) were used to test response to forage treated with Tasco-Forage (an extract of the brown kelp Ascophyllum nodosum) prior to conserving, or to direct feeding of the extract (Tasco-EX). Hays made from endophyte (Neoyphodium coenophialum)-infested tall fescue (Festuca arundinacea)-based pasture received 0 or 3 kg of Tasco/ha prior to harvest. Lambs, blocked by weight, were randomly allotted to three diets: (1) control hay, (2) treated hay, and (3) #1 + Tasco-EX fed at 1% of the diet. Hays were low in CP (<7%) so all lambs were fed soybean meal (12% of the diet) in addition to trace mineralized salt. Diets were fed at 1.5% BW to prevent refusals. Total collections (7 d) were made during periods without or with applied heat stress. After each period, rumen contents were obtained to determine pH, NH₃ and VFA. Lambs were sacrificed post-trial. A subset was used to evaluate sensory traits and muscle fatty acids. Lambs were in negative N balance during the study and Tasco treatments did not affect N metabolism. Fecal N tended (P < 0.10) to increase with short duration heat stress causing a concomitant decrease (P < 0.05) in apparent N digestibility (58.6 versus 56.1%; S.E. = 0.7). Urinary N loss decreased (P < 0.001) with heat stress (8.0 versus 5.9 g/d; S.E. = 0.2), resulting in increased (P < 0.001) N retention (−2.1 versus −0.3 g/d; S.E. = 0.2). Apparent OM digestibility was not affected by heat stress but was greater (P < 0.05) for lambs fed Tasco-EX treatment than those fed treated hay. Treatment diets decreased (P < 0.05) ruminal butyrate. Heat stress increased (P < 0.05) acetate and total VFA and decreased (P < 0.01) ruminal pH. A tendency (P < 0.11) of increased 14:1ω5, decreased (P < 0.05) 18:0 and total saturated fatty acids in muscle was observed with Tasco diets. Meat sensory characteristics were not affected by treatment. Tasco may alter some aspects of rumen or lipid metabolism but has no effect on N metabolism or meat sensory characteristics of sheep fed restricted, low-quality diets.     

Utilisation of fish oil in ruminants: I. Fish oil metabolism in sheep

Five sheep with rumen and abomasal cannulae were offered three diets sequentially in the order: control (C) pellets (lucerne hay-oat grain: 60/40, w/w), control plus unprotected tuna oil (UTO pellets), and control plus tuna oil protected (casein-formaldehyde matrix) against ruminal biohydrogenation (PTO pellets). In supplemented diets, tuna oil constituted 3% (w/w) of total dry matter (DM), and each supplement was fed for 12 days, with 9 days allowed between the two fish oil feeding periods to minimise carry-over effects. Daily DM intake was 785±38 g/head during the control period. It was significantly reduced by UTO feeding (6.2%, P<0.05) but not PTO feeding. The level of EPA in the abomasum during PTO feeding was double that measured during UTO feeding (1.30 versus 0.61% of FA, P<0.05). The level of DHA in the abomasum did not significantly differ between UTO and PTO feeding periods. Both tuna oil supplements significantly increased the levels of 18:1 trans and that of a fatty acid derivative identified as 10-hydroxystearic acid (10-HSA) in both the rumen and abomsum. Tuna oil supplementation also altered the fatty acid composition of plasma lipid fractions and 10-HSA was solely incorporated into plasma free fatty acids. This study indicates that substantial protection of tuna oil against ruminal hydrogenation inhibited reduced feed intake, but increased the proportion of 18:1 trans isomer and fatty acids derivatives (10-HSA), which indicate interference with metabolism in the rumen.     

Effects of isovalerate supplements on morphology and functional gene expression of rumen mucosa in pre- and post-weaning dairy calves

Isovalerate supplements could stimulate rumen development by improving morphology and function of rumen mucosa, and then promote the growth of calves. This study was done to evaluate the effects of isovalerate supplements on morphology and functional gene expression of rumen mucosa in dairy calves. In total, 48 Chinese Holstein male calves with 15 days of age and 45.1±0.36 kg of BW were randomly assigned to four groups. The treatments were: control, low-isovalerate, moderate-isovalerate and high-isovalerate with 0, 3, 6 and 9 g isovalerate per calf per day, respectively. Supplementary isovalerate was hand-mixed into milk in pre-weaning calves and into concentrate portion in post-weaning calves. The study consisted of a 15-day-adaptation period and a 60-day-sampling period. Calves were weaned at 60 days of age. Three calves were slaughtered from each of the four treatments at 30, 60 and 90 days of age. The weight of body and stomach were measured, samples of ruminal tissues and blood were analyzed. Total stomach weight, total stomach to BW ratio, rumen wall and keratinized layer thickness, serum growth hormone and IGF-1 for both pre- and post-weaning calves increased linearly with increasing isovalerate supplements. Rumen to total stomach weight ratio, the length and width of rumen papillae, and serum β-hydroxybutyrate increased linearly for post-weaning calves. However, abomasum weight to total stomach weight ratio decreased linearly for both pre- and post-weaning calves. The relative messenger RNA expression for growth hormone receptor, IGF-1 receptor and 3-hydroxy-3-methylglutaryl-CoA synthase 1 in rumen mucosa increased linearly for post-weaning calves. Our results suggested that isovalerate supplements promoted rumen development in a dose-dependent manner. The optimum dose was 6.0 g isovalerate per calf per day.     

Ecology of uncultivated Oscillospira species in the rumen of cattle, sheep, and reindeer as assessed by microscopy and molecular approaches

The ecology of the uncultured, but large and morphologically conspicuous, rumen bacterium Oscillospira spp. was studied. Oscillospira-specific 16S rRNA gene sequences were detected in North American domestic cattle, sheep from Australia and Japan, and Norwegian reindeer. Phylogenetic analysis of the sequences obtained allowed definition of three operational taxonomic units within the Oscillospira clade. Consistent with this genetic diversity, we observed atypical smaller morphotypes by using an Oscillospira-specific fluorescence in situ hybridization probe. Despite the visual disappearance of typical large Oscillospira morphotypes, the presence of Oscillospira spp. was still detected by Oscillospira-specific PCR in the rumen of cattle and sheep. These observations suggest the broad presence of Oscillospira species in various rumen ecosystems with the level, and most likely the morphological form, dependent on diet. An ecological analysis based on enumeration of the morphologically conspicuous, large-septate form confirms that the highest counts are associated with the feeding of fresh forage diets to cattle and sheep and in two different subspecies of reindeer investigated.     

Effect of the proportions of neutral detergent fibre and starch, and their degradation rates, on in vitro ruminal fermentation

Effects of proportions of neutral detergent fibre (aNDFom) and starch, as well as their degradation rates, on rumen fermentation were tested using an in vitro rumen simulation system (SIMCO). The in vitro system was designed to simulate selective particle retention and had an average fluid volume of 1150 ml with a liquid dilution rate of approximately 0.07 h⁻¹. Two types of hay (aNDFom sources) and two types of starch were each included at two different levels in the diet and were examined in an experiment following a 2×2×2 factorial arrangement of treatments (eight diet combinations). The hay was either late-cut timothy (Phleum pretense L.) or early cut meadow grass (Poa pratensis L.), with ruminal in situ aNDFom digestion rates of 0.03–0.04 and 0.07–0.08 h⁻¹, respectively. The two starch types were raw (R) and cooked (C) potato starch with previously determined in vitro ruminal digestion rates of 0.04 and 0.20 h⁻¹, respectively. The starch levels were 300 and 600 g/kg diet dry matter (DM) with the remaining being hay (282–682 g/kg DM) and peptone (14–111 g/kg DM). The aNDFom level varied among the diets with different starch levels and hay types. The peptone acted as a source of peptides and, together with ammonia salts from buffer, was used to balance the N contents of the diets. The feeding level for each of the eight vessels was 28 g DM/d. Two 10-day simulations were made with the system. The average pH was higher (P<0.05) for all treatments with raw potato starch (6.19) versus cooked starch (6.07). Protozoa scores, on a qualitative scale, declined faster at the higher starch level. The aNDFom digestibility was, as expected, higher (P<0.001) for meadow hay (0.57) than timothy (0.32), and was also higher (P<0.001) at the lower starch level (0.54) versus the higher (0.35). Microbial protein production efficiency (mg microbial N/g organic matter truly digested) was higher for the faster degrading aNDFom (P<0.01) and starch (P<0.05) sources, but was not affected by starch level. Cooked starch resulted in a lower acetate proportion (449 mmol/mol versus 591 mmol/mol VFA; P<0.001) but higher proportions of propionate (297 mmol/mol versus 236 mmol/mol VFA; P<0.001), and butyrate (169 mmol/mol versus 127 mmol/mol VFA; P<0.01). Butyrate increased with starch level (127 mmol/mol versus 169 mmol/mol VFA; P<0.01), and was also higher for meadow hay versus timothy (168 mmol/mol versus 128 mmol/mol VFA; P<0.01). Interactions between the treatments demonstrate that the response in VFA pattern to starch level is dependent on starch and aNDFom sources. Substrates such as starch and aNDFom are fermented differently depending on their rates of ruminal degradation.     

Influence of storage time and temperature on in vitro digestion of neutral detergent fibre at 48 h, and comparison to 48 h in sacco neutral detergent fibre digestion

The effect of within-day delays of 0.5, 2.5, 4.5 and 6.5 h between collection of rumen fluid from a cow and initiation of in vitro fermentation, as well as storage of rumen fluid for 48 h at either −24°C or 6, 22 and 39°C, on in vitro digestion of neutral detergent fibre (NDF) at 48 h was determined. In addition, the 48 h in vitro digestion of NDF, determined with a minimum time delay (i.e., 0.5 h) between collection from the cow and initiation of incubation, was compared to NDF digestion determined in sacco at 48 h. Rumen inoculum from a single cow was utilized in a thrice replicated incubation with whole crop alfalfa, corn, cereal and sudangrass forages of a lower and higher quality. The same cow was used as the host for the in sacco bags. The in vitro procedure used a bulk procedure with 5.0 cm × 5.5 cm multi-weave polyethylene polyester polymer bags that retained particles of 25 mm and larger. The in sacco procedure used the same bags retained in a large mesh bag. A within-day time delay of up to 6.5 h between collection of rumen fluid from the cow and initiation of in vitro fermentation had no impact on measured 48 h in vitro digestion of NDF. In contrast, no temperature dependent storage procedure maintained 48 h in vitro digestion of NDF at levels determined with no 48 h storage, although high quality alfalfa was least affected by any storage procedure. The 48 h in vitro digestion of NDF, determined using the minimum time delay between collection from the cow and initiation of the incubation, was higher than values obtained in sacco. Results show that this bulk in vitro procedure resulted in higher 48 h digestion of NDF than those determined with a similar in sacco procedure, thereby suggesting that laboratories located some distance from the donor animal can utilize in vitro procedures to accurately estimate 48 h digestion of NDF. However, storage of rumen fluid for 48 h, by any temperature dependent procedure examined, in order to facilitate fewer trips to the donor animal, or trips of substantially longer duration, will underestimate 48 h digestion of NDF to an extent that depends upon the forage incubated.     

Ruminal microbial digestion in free-living, in captive lichen-fed, and in starved reindeer (Rangifer tarandus tarandus) in winter.

In free-living (FL) reindeer eating a natural mixed winter diet dominated by lichens, captive (CF) reindeer fed pure lichens ad libitum, and CF reindeer subsequently starved for 1 day (CS1 reindeer) or 4 days (CS4 reindeer), the dominant rumen anaerobic bacteria were characterized, their population densities were estimated, and ruminal pH and volatile fatty acid concentrations were determined. In the FL reindeer, the total median viable anaerobic bacterial population ranged from 18 x 10(8) to 35 x 10(8) cells per ml of rumen fluid (n = 4), compared with 26 x 10(8) to 34 x 10(8) and 0.09 x 10(8) to 0.1 x 10(8) cells per ml of rumen fluid in CF reindeer (n = 2) and CS4 reindeer (n = 2), respectively. The median bacterial population adhering to the rumen solids ranged from 260 x 10(8) to 450 x 10(8), 21 x 10(8) to 38 x 10(8), and 0.5 x 10(8) cells per g (wet weight) of rumen solids in FL, CF, and CS4 reindeer, respectively. Although there were variations in the rumen bacterial composition among the FL reindeer (n = 4), strains of Bacteroides, Fibrobacter, Streptococcus, and Clostridium dominated in the rumen fluid. Streptococcus spp. and Clostridium spp. were the dominant bacteria in the CF reindeer (n = 2), while in the CS4 reindeer (n = 2) the dominant bacteria were Fusobacterium spp., members of the family Enterobacteriaceae, and Eubacterium spp. Transmission electron micrographs of lichen particles from the rumen of one FL reindeer, one CF reindeer, and one CS4 reindeer show bacteria resembling Bacteroides spp. adhering to the lichen particles, evidently digesting the lichen hyphae from the inside.(ABSTRACT TRUNCATED AT 250 WORDS)     

Postnatal differential expression of chemoreceptors of free fatty acids along the gastrointestinal tract of supplemental feeding v. grazing kid goats

The gastrointestinal tract (GIT) of animals is capable of sensing various kinds of nutrients via G-protein coupled receptor-mediated signaling transduction pathways, and the process is known as ‘gut nutrient chemosensing’. GPR40, GPR41, GPR43 and GPR119 are chemoreceptors for free fatty acids (FFAs) and lipid derivatives, but they are not well studied in small ruminants. The objective of this study is to determine the expression of GPR40, GPR41, GPR43 and GPR119 along the GIT of kid goats under supplemental feeding (S) v. grazing (G) during early development. In total, 44 kid goats (initial weight 1.35±0.12 kg) were slaughtered for sampling (rumen, abomasum, duodenum, jejunum, ileum, cecum, colon and rectum) between days 0 and 70. The expression of GPR41 and GPR43 were measured at both mRNA and protein levels, whereas GPR40 and GPR119 were assayed at protein level only. The effects of age and feeding system on their expression were variable depending upon GIT segments, chemoreceptors and expression level (mRNA or protein), and sometimes feeding system × age interactions (P<0.05) were observed. Supplemental feeding enhanced expression of GPR40, GPR41 and GPR43 in most segments of the GIT of goats, whereas G enhanced expression of GPR119. GPR41 and GPR43 were mainly expressed in rumen, abomasum and cecum, with different responses to age and feeding system. GPR41 and GPR43 expression in abomasum at mRNA level was greatly (P<0.01) affected by both age and feeding system; whereas their expression in rumen and abomasum at protein level were different, feeding system greatly (P<0.05) affected GPR41 expression, but had no effect (P>0.05) on GPR43 expression; and there were no feeding system×age interactions (P>0.05) on GPR41 and GPR43 protein expression. The expression of GPR41 and GPR43 in rumen and abomasum linearly (P<0.01) increased with increasing age (from days 0 to 70). Meanwhile, age was the main factor affecting GPR40 expression throughout the GIT. These outcomes indicate that age and feeding system are the two factors affecting chemoreceptors for FFAs and lipid derivatives expression in the GIT of kids goats, and S enhanced the expression of chemoreceptors for FFAs, whereas G gave rise to greater expression of chemoreceptors for lipid derivatives. Our results suggest that enhanced expression of chemoreceptors for FFAs might be one of the benefits of early supplemental feeding offered to young ruminants during early development.