Protozoa Counts Research Articles

Digestibility of prairie hay diets supplemented with different levels of magnesium-mica by beef heifers.

Four ruminally fistulated, nonpregnant, nonlactating heifers (515 +/- 7.9 kg) were offered chopped (10-cm screen size) prairie hay for ad libitum consumption with 1.8 kg/d of supplements to provide 0, 45, 113, or 181 g/d of magnesium-mica (MM) in a 4 x 4 Latin square design experiment. Heifers were adapted to diets for 7 d in drylot followed by a 19-d confinement period in individual stalls within a metabolism facility. Total feces and urine were collected for 5 d, daily intake and water consumption were monitored for 16 d, and in situ disappearance of fiber (prairie hay) and CP (soybean meal) were determined during the confinement period. Ruminal samples for fermentation product analyses were collected at feeding and every 2 h thereafter for 12 h on d 18, and rumens were evacuated at 1100 on d 19 to determine rumen fill. Cubic responses (P < .05) to MM level were observed for DM, OM, NDF, and ADF digestion and were characterized by a tendency for improved digestion with 45 g/d compared with the control diet, followed by a suppressive effect on digestion with 113 g/d, then little effect with 181 g/d MM. In situ NDF disappearance at 72 and 96 h tended (P < . 10) to be influenced quadratically by level of MM, but MM level had no apparent effect on ruminal fill and passage rate, ciliated protozoa counts, in situ rate of disappearance of fiber or CP, or nitrogen balance. Therefore, feeding MM at low levels to heifers consuming a prairie hay diet with a 20% CP supplement seemed to be beneficial for feed digestion with no measurable negative impact on intake or ruminal protein or fiber digestion.

Effects of feeding quebracho tannin diets, with or without a dietary modifier, on rumen function in sheep

AbstractThe effect of quebracho tannin (QT) on the activities of rumen microbes was studied both in vivo and in vitro. The in vivo study was carried out in four rumen environments created by feeding four fistulated sheep a basal diet of chopped grass hay, grass cubes and whole barley (control) with or without the addition of QT and the dietary modifier Browse Plus (BP). The active ingredients in BP are polyethylene glycol (PEG, more than 0·95 of the dry material), polyvinyI pyrrolidone (PVP) and calcium hydroxide. The diets offered were control, control plus 50 g QT per kg diet (CQT), control plus 50 g QT per kg and 0·1 (CQT+ 0·1) or 1.0 g BP per kg (CQT + 1·0). The experiment was a 4 X 4 Latin-square design with periods of 4 weeks. Rumen liquor samples were collected at 0, 2, and 8 h after feeding, 18 and 25 days after commencement of each period. Changes in free and bound proanthocyanidin (PA) concentrations, rumen pH, ammonia, volatile fatty acids (VFA), soluble protein concentrations, particle-bound cellulase and xylanase activities and rumen protozoal counts were used as indices of microbial activities. The same diets were incubated with rumen contents in vitro, except that the 0.1 g/kg level of BP was replaced by a fourth treatment made up of control plus 1·0 g BP per kg DM of hay (CBP). In vivo, bound PA concentrations in the rumen liquor of all the sheep given QT-containing diets were higher than those of the free PAs. The bound PA was higher (V &lt; 0·05) in the rumen liquor of sheep given CQT in comparison with those containing BP. There were reductions in ammonia (P &gt; 0·05), soluble protein (P &lt; 0·05) and total VFA (P &gt; 0·05) concentrations in the rumen liquor of sheep given CQT in comparison with those given the control and BP-containing diets. Reductions (P &gt; 0·05) were also observed in the cellulase and xylanase activities of the rumen microbes and in protozoal counts (P &lt; 0·05) in the presence of QT in the diet. In vitro, QT reduced (P &gt; 0·05) the viable bacterial counts, gas production and the total VFA concentrations after incubation. In both the in vivo and in vitro experiments, BP was able to alleviate some but not all of the depression in microbial activities. The main constituent (PEG) in BP binds to some of the tannins in solution and may displace tannins from tannin-protein complexes.

Methane suppression by coconut oil and associated effects on nutrient and energy balance in sheep

Three different diets with increasing proportions of coconut oil (0, 3.5 and 7%) were fed to six sheep in an incomplete Latin square experiment with four replicates per diet. The diets were composed of hay and concentrates either without or with coconut oil. Concentrate comprised 28.8 and 54.6% of the diet DM in the treatments containing 3.5 and 7% coconut oil, respectively. Wethers on all treatments were fed at 1.2 × maintenance. Gaseous exchange was measured in respiratory chambers. Protozoa counts were reduced (P &lt; 0.05) by 88 and 97% when diets contained 3.5 and 7% coconut oil, respectively, whereas bacteria counts increased (P &lt; 0.05). Supplementation of coconut oil at proportions of 3.5 and 7% suppressed (P &lt; 0.001) methane production by 28 and 73%, respectively, as related to the unsupplemented diet. This proportionately reduced (P &lt; 0.001) the amount of gross energy lost through methane from 7.5 to 5.7 and 2.5%, in diets containing 0, 3.5 and 7% coconut oil, respectively. Assuming a linear suppressive effect of coconut oil, about half of the additional methane reduction with the 7% coconut oil diet as compared with the 3.5% diet was attributed to the substitution of concentrate for hay. Digestibility of cell wall constituents was numerically decreased by coconut oil. Apart from this and its effect on methane emissions coconut oil had no major influence on digestion or on energy and nitrogen balance. Key words: Coconut oil, methane, energy balance, sheep, ruminants

Effect of virginiamycin on ruminal fermentation in cattle during adaptation to a high concentrate diet and during an induced acidosis.

The objective of Exp. 1 was to compare the effects of virginiamycin (VM; 0, 175, or 250 mg x animal(-1) x d(-1)) and monensin/tylosin (MT; 250/ 90 mg x animal(-1) x d(-1)) on ruminal fermentation products and microbial populations in cattle during adaptation to an all-concentrate diet. Four ruminally cannulated, Holstein steers were used in a 4x4 Williams square design with 21-d periods. Steers were stepped up to an all-concentrate diet fed at 2.5% of BW once daily. Ruminal pH, protozoal counts, and NH3-N and VFA concentrations generally were unaffected by VM or MT. Mean counts of Lactobacillus and Streptococcus bovis were lower (P<.05) for VM-treated compared with control or MT-treated steers. Both VM and MT prevented the increase in Fusobacterium necrophorum counts associated with increasing intake of the high-concentrate diet observed in the control. The objective of Exp. 2 was to compare the effects of VM and MT on ruminal pH, L(+) lactate and VFA concentrations, and F. necrophorum numbers during carbohydrate overload. Six ruminally cannulated Holstein steers were assigned randomly to either the control, VM (175 mg/d), or MT (250 + 90 mg/d) treatments. Acidosis was induced with intraruminal administration of a slurry of ground corn and corn starch. The VM and MT premixes were added directly to the slurry before administration. Carbohydrate challenge induced acute ruminal acidosis (pH was 4.36 and L (+) lactate was 19.4 mM) in controls by 36 h. Compared with the controls, steers receiving VM or MT had higher (P<.05) ruminal pH, and the VM group had a lower (P<.05) L (+) lactate concentration. Fusobacterium necrophorum numbers initially increased in VM- and MT-administered steers. In the control steers, F. necrophorum was undetectable by 36 h. Virginiamycin seemed to control the growth of ruminal lactic acid-producing bacteria and, therefore, has the potential to moderate ruminal fermentation in situations that could lead to rapid production of lactic acid.

Potential of various fatty feeds to reduce methane release from rumen fermentation in vitro (Rusitec)

The effects of coconut oil and whole crushed oilseeds (rapeseed, sunflower seed and linseed) on rumen fermentation, as well as on methane and hydrogen release, were evaluated in vitro employing the rumen simulation technique (Rusitec). A low-fat diet served as the negative control and a diet with rumen protected fat as the positive control. By using two different proportions of concentrate in the diet, 6% and 9% of total lipids were supplied with each of the five fat supplemented diets, whereas the control diets contained about 3% total lipids. The 12 diets were provided at daily amounts of 11 g and 22 g dry matter. Rumen-protected fat as well as rapeseed had small effects on fermentation pattern and methane formation, which presumably resulted from the exchange of carbohydrates by fat. In contrast, coconut oil, sunflower seed and linseed significantly reduced protozoa count and methane release. An increased fat supply by the higher concentrate proportion further supported the suppressing effects of these types of fat on protozoa and methane. Coconut oil completely eliminated protozoa from rumen fluid after four to nine days of application, and this period was shorter by more than 30% on average at the higher level of supply. As compared with the low-fat treatment, coconut oil suppressed methane by 43% with medium and 57% with high concentrate level. The maximum methane reduction with sunflower seed and linseed accounted for about 40%. An increase in hydrogen release was found with coconut oil and oilseeds which, however, was considerably lower than the hydrogen quantities that were less incorporated into methane. In these situations, hydrogen recovery, as calculated from hydrogen balance, was reduced.

Effect of Soybean Hulls, Soy Lecithin, and Soapstock Mixtures on Ruminal Fermentation and Milk Composition in Dairy Cows

Two experiments were conducted to determine effects of soybean hulls, soy lecithin, and soapstock mixtures on ruminal fermentation, milk composition, and ruminal microbial populations. In Experiment 1, 20 Holstein dairy cows were assigned to one of five total mixed rations (TMR) in replicated 5 × 5 Latin squares to measure the effect of TMR on intake and milk composition. Four ruminally fistulated cows were used in a 4 × 5 Youden square to measure the effect of TMR on ruminal fermentation. The TMR consisted of 40 or 50% alfalfa and corn silages, 13% soybean hulls, and 47 or 37% of a concentrate containing either 2.25% soybean oil; 2.25% lipid from a mixture of soybean hulls, soy lecithin, and soapstock; or no added lipid. The ratios of soy lecithin to soapstock evaluated were 1:1, 2.5:1, and 4:1 (dry basis). The TMR containing soy lecithin and soapstock at ratios of 1:1 and 2.5:1 resulted in higher milk C18:2 than did the soybean oil TMR. Rate of ruminal NDF digestion of soybean hulls was reduced for the soybean oil TMR.In Experiment 2, a semi-continuous culture system was used to determine effects of soybean oil or an optimal mixture of soy lecithin and soapstock (1:1, wt/wt) on fermentation of soybean hulls and microbial populations. The TMR containing the lipid mixture increased the ratio of acetate to propionate compared with the TMR containing soybean oil and resulted in higher total protozoal counts than did the control TMR. The TMR containing mixtures of soy lecithin and soapstock at ratios of 1:1 and 2.5:1 elevated milk C18:2, and no negative effect on NDF digestion was detected, indicating some degree of ruminal protection.

Effect of multipurpose tree (MPT) supplements on ruminal ciliate protozoa

The effect of five multipurpose trees (MPTs), Acacia angustissima, Acacia saligna, Chamaecytisus palmensis, Leucaena pallida and Sesbania sesban on ciliate protozoa was investigated in rumen cannulated Ethiopian sheep. Both entodiniomorphs and holotrichs were counted. The protozoa counts from S. sesban supplemented diet were significantly ( P < 0.04) higher than from other diets. Maize stover alone and maize stover supplemented with C. palmensis or L. pallida did not have any significant ( P > 0.05) effect on the numbers of ciliate protozoa. A. saligna supplemented diet reduced the numbers of protozoa from 1.60 × 10 5 to 0.62 × 10 5 cells ml −1 rumen fluid. Differences in ciliate numbers among other MPT supplements barely failed to reach significance ( P < 0.06). Entodiniomorphs dominated (93.3%) the protozoa population in all diets, with Entodinium species being the most predominant (80.7%). None of the MPTs tested eliminated protozoa. Effect of eating S. sesban and placing it in the rumen on protozoa was tested. Protozoa numbers decreased in the sheep in which S. sesban was placed in the rumen while they remained high in the sheep that were allowed to eat the supplement. Relationships between protozoal numbers and in sacco fibre degradation and neutral detergent fibre (NDF) digestibility were also examined. Degradation rate ( c) increased with increase in protozoa numbers. NDF digestibility was significantly ( P < 0.01) lower in A. saligna supplemented diet than in others. No significant relationship was observed between ruminal pH and protozoal numbers with all diets. The animals on A. angustissima died after 9 and 21 days of the experiment.

Effect of concentrates in a hay diet on the contribution of anaerobic fungi, protozoa and bacteria to nitrogen in rumen and duodenal digesta in sheep

Two sheep, cannulated at the rumen and the duodenum, were given diets of chopped orchard grass hay (H) and 3 parts grass hay to 2 parts concentrates (M). The the pools and flows of anaerobic fungi, protozoa, liquid-associated bacteria (LAB) and solids-associated bacteria (SAB) were measured. The anaerobic fungi contributed only 11–35 g N/kg of the microbial-N in the rumen and 7–27 g N/kg of the microbial-N flowing to the duodenum. Inclusion of concentrates in the diet increased fungal zoospore counts and biomass and, in sheep 1, resulted in a more than four-fold increase in rumen protozoal counts: the protozoal contribution to its microbial N increased from 41 to 66% in the rumen and from 4 to 15% in duodenal flow. For sheep 2, there was an almost two-fold increase in protozoal counts and their contributions to its rumen and duodenal microbial N increased from, respectively, 35 to 57% and 7 to 9%. These changes were associated with a decrease in the yield of rumen microbial-N from 31 to 25 g/kg OM digested in the stomach for sheep 1 but an increase from 37 to 42 g/kg OM digested in the stomach for sheep 2. In addition, there were decreases in non-ammonia-N (NAN) flow to and digestion in the intestines of sheep 1 but increases in sheep 2. Protozoa obtained 40–58% of their N from bacteria. When diaminopimelic acid was used as the marker, bacterial-N was overestimated in rumen digesta and appeared to be underestimated in duodenal digesta. The ratio of duodenal NA 15N to either rumen or duodenal LAB- 15N underestimated the contribution of microbial-N to duodenal NAN. The mean retention times (MRT) of protozoa were much longer than those of digesta particles, reflecting protozoal sequestration in the rumen. On the hay diet, the apparent MRTs of LAB were the same as those for SAB and particles whereas, when concentrates were included in the diet, the MRTs of LAB were similar to those of solutes in sheep 2 and between those of solutes and particles in sheep 1; apparent MRTs of SAB were always similar to particle MRT. These results and the calculated generation times of LAB and SAB were consistent with the conclusion that, on the hay diet, LAB were probably SAB “in transit” between particles but, with the inclusion of concentrates, they were predominantly starch-utilizing organisms whose proliferation in the rumen of sheep 1 was limited by predation by its large protozoal population. Ammonia was produced in and absorbed from the omasum and the 15N-incorporation data were consistent with the growth of LAB in the omasum.

Soil respiration profiles and protozoan enumeration agree as microbial growth indicators

Carbon, nitrogen or phosphorus limitation of microbial growth in a forest and a field soil was evaluated from measurements of respiration and protozoan counts after nutrient addition. In both soils simultaneous addition of C (glucose) and N (NH 4NO 3) resulted in microbial growth as indicated by a gradual increase in respiration rate whereas a single addition of C did not induce microbial growth. Addition of P (KH 2PO 4 + Na 2HPO 4) to C-amended soil stimulated activity slightly in forest soil but not in field soil whereas addition of P to soil amended with C and N increased growth markedly in both soils. The stimulation of microbial growth indicated by respiration profiles following C and N addition was supported by enumeration of bacterivorous protozoa. The numbers of soil protozoa increased above the control only when C and N were added simultaneously. These observations lend support to the proposal that respiration patterns may be valuable in an analysis of nutrient limitation of microbial growth in soils.

Effect of virginiamycin on ruminal fermentation in faunated or ciliate-free sheep overfed with barley grain

The effect of virginiamycin on ruminal fermentation was investigated in faunated or ciliate-free sheep challenge fed with 1.7 kg whole barley grain. Defaunation was achieved with oral drenching of alkanate 3SL3. All sheep were fed a diet of wheaten chaff (1.4 kg day −1) supplemented twice weekly with 700 g barley grain. The faunated ( n = 10) and ciliate-free ( n = 8) sheep were each randomly allocated to two treatment groups and challenge fed with 1.7 kg barley alone or with virginiamycin at 40 g per ton. Ruminal contents were sampled at 0, 1.5, 3.0, 6.0, 12.0, and 24 h after grain challenge to enumerate ciliated protozoa and measure pH and fermentation end-products. All animals consumed the 1.7 kg of grain within an hour of being fed. The inclusion of virginiamycin with barley decreased ( P < 0.05) total ciliated protozoal counts in faunated sheep, primarily due to reduction in Entodinium species. Defaunation had no effect on rumen pH, and concentrations of lactate, VFA, and ammonia. Sheep challenged with barley alone showed no evidence of ruminal acidosis (pH > 6.0 or lactate concentration < 1.0 mM). Virginiamycin decreased ( P < 0.01) ruminal pH and increased ( P < 0.05) lactate and propionate concentrations following grain challenge. Ammonia concentration declined ( P < 0.01) in sheep challenged with barley grain but not in sheep fed barley and virginiamycin. It was concluded that sheep adapted to twice weekly supplementation of grain were able to resist overfeeding with grain and virginiamycin had the propensity to increase lactic acid accumulation in the rumen. It was hypothesized that the effect of virginiamycin on the pattern of rumen fermentation (elevated lactate and propionate) was reflective of redirection of electrons away from methane production.

Effects of pore size of nylon bags and dilution rate on fermentation parameters in a semi-continuous artificial rumen

Incubation trials were carried out with the rumen simulation technique (RUSITEC) to study the effects of bag pore size (40, 100 and 200 μm) and dilution rate (2.3%/h and 3.5%/h) on the fermentation parameters and number of protozoa when a high forage diet was incubated. The lower dilution rate resulted in a decrease in pH and an increase in the molar proportion of butyrate, but the disappearance of the diet from the bags was not affected. Protozoal counts were not affected by dilution rate, but holotrichs disappeared completely at low dilution rate as a consequence of low pH. Disappearance of the diet from the bags was higher with 100 μm than with 40 μm bags, but this could not be explained by higher washing losses. Numbers of protozoa were lower with 40 μm than with 100 μm bags, and large protozoa were not present when 40 μm bags were used. There was no difference in protozoa counts between pore sizes of 100 μm and 200 μm and large protozoa were present with both of them. However, disappearance of the diet from the bags and methane and acetate productions were higher ( P < 0.05) with 100 μm bags than with those of 200 μm. Our results indicate that pore size of the bags in RUSITEC affects not only the disappearance of the diet, but also the microbial population in the system and therefore the fermentation.

Digestion in defaunated and refaunated sheep fed soybean oil hydrolysate or crushed toasted soybeans

Defaunated then refaunated sheep were given diets containing soyabean oil hydrolysate (SOH: 70 g/day) or an equivalent amount of lipids administered as crushed toasted soyabeans (TSB). Defaunation increased molar percentage of propionate in the rumen, while butyrate decreased. SOH caused a similar effect in both the defaunated and refaunated rumen, while the effect on acetate proportions was variable. Protozoal counts were lower after feeding SOH. Crushed toasted soyabeans had a minor effect on rumen fermentation pattern. Rumen digestibility of organic matter was decreased by both defaunation and SOH feeding, with a concomitant shift in digestion to the lower intestinal tract. Total tract digestibility was not affected. Both treatments increased nonammonia N flows at the duodenum, but this was only significant with defaunation. Total tract digestion of N remained almost constant. Defaunation resulted in more microbial protein reaching the duodenum. Except for the TSB diet, total lipid leaving the rumen equalled intake. Total tract digestibility of total lipid was much higher with SOH and TSB than with controls. Defaunation almost doubled microbial growth efficiency and this value tended to increase by SOH feeding. The decrease of protozoal count or even elimination of protozoa after lipid feeding could not entirely explain the change in rumen metabolism, as additional changes in defaunated sheep were shown.

Effects of some ionophore antibiotics and polyoxins on the growth of anaerobic rumen fungi

The growth of mixed rumen fungi in vitro was suppressed by both ionophore antibiotics (salinomycin, monensin and portmicin) and polyoxins (polyoxin B and D: inhibitors of chitin synthesis). The fungistatic effect of the ionophores on a Piromonas spp. was more pronounced than on a Neocallimastix spp. The polyoxins, however, were more potent fungistatically against the Neocallimastix spp. than the Piromonas spp. Higher concentrations of the polyoxins were required to elicit the same effect as that observed with the ionophores. Salinomycin administration decreased fungal count in the rumen of sheep, but fungal count increased after the cessation of the feeding of the antibiotic. Polyoxin D also suppressed the growth of fungi in vivo, but the effect was short-lived. Nevertheless, both bacterial and protozoal counts tended to increase during and after the administration of polyoxin D. Total volatile fatty acid concentrations in the rumen tended to increase during the period of polyoxin D administration. This increasing tendency was maintained for 10 d after the cessation of antibiotic administration. Offering polyoxin D to sheep increased production of propionate (P < 0.05), while decreasing that of acetate. The results indicate that the rumen fungi are sensitive to chitin synthesis inhibitors as well as ionophores, and are essential members of microbes in the rumen ecosystem.

Factors Stimulating Propagation of Legionellae in Cooling Tower Water

Our survey of cooling tower water demonstrated that the highest density of legionellae, >/=10 CFU/100 ml, appeared in water containing protozoa, >/=10 MPN/100 ml, and heterotrophic bacteria, >/=10 CFU/100 ml, at water temperatures between 25 and 35 degrees C. Viable counts of legionellae were detected even in the winter samples, and propagation, up to 10 CFU/100 ml, occurs in summer. The counts of legionellae correlated positively with increases in water temperature, pH, and protozoan counts, but not with heterotrophic bacterial counts. The water temperature of cooling towers may promote increases in the viable counts of legionellae, and certain microbes, e.g., protozoa or some heterotrophic bacteria, may be a factor stimulating the propagation of legionellae.

Avaliação dos protozoários ciliados no rúmen de búfalos (Bubalus bubalis L.) e bovinos (Bos indicus L.) em regime de confinamento

Num experimento de engorda em confinamento, foram utilizados nove bubalinos e nove zebuínos, todos machos castrados, de 18 a 24 meses de idade e peso médio de 340 kg, mantidos em baias individuais, consumindo dieta de 2,0 kg de soja crua moída, 2,0 kg de espigas de milho desintegradas (grão, palha e sabugo) e silagem de sorgo à vontade (controlando-se o consumo diário). Ao final do período de confinamento, todos os animais foram abatidos e o conteúdo ruminal de cada indivíduo foi homogeneizado, sendo colhidas amostras de 30 a 40 ml de liquido ruminal e, desta, retirou-se alíquota de 10 ml em tubo de ensaio com 20ml de formaldeído diluído em água destilada a 1:2,para fixação dos protozoários ciliados. As contagens de protozoários foram feitas em 100 campos e os resultados permitiram as seguintes conclusões: 1) adieta favoreceu maior concentração de protozoários ciliados/ml de liquido ruminal dos zebuínos que no de bubalinos, apesar destes apresentarem maior número de gêneros; 2) os protozoários ciliados digestores de fibra foram detectados em maior quantidade nos zebuínos que nos bubalinos; 3) o gênero Emodinium spp representou mais de 80% do total dos protozoários ciliados identificados nos zebuínos e nos bubalinos.

Total Protozoa Counts and Ammonia in the Rumen of Mature Dry Friesian Cows on Hay-based Rations

The present work was an attempt to determine whether the variations in ruminal ammonia concentrations could be directly correlated to corresponding changes in total protozoa numbers of cattle. Four dry Friesian cows fed with hay-based rations were used through several experiments in which the twice daily feeding (6.15-15.30 h) as well as a 30 h-fasting period were studied. Simultaneously to a continuous or a regular collection of rumen liquor (for NH3), samples of rumen contents (for total protozoa numbers) were regularly withdrawn from the ventral sac. Any definite nycthemeral cycle of the protozoa numbers could not be related to feeding time. Moreover, no significant relationship could be found between the ruminal ammonia and the corresponding total protozoa numbers measured in the nocturnal interprandial period or during starvation. The data suggest that the nycthemeral ammonia profiles recorded in cattle are not directly related to protozoal activity.

Predation rates of flagellate and ciliated protozoa on bacterioplankton in a river

Predation rates of flagellate and ciliate protozoa on the bacterioplankton of Butron River (Spain) were determined from FLB (fluorescently labelled bacteria) uptake rates. Bacterial and ciliate protozoa counts were higher when higher water temperature was recorded. Flagellate counts did not show this pattern, which suggested predation of flagellates by other organisms, or some other different nutritional mode besides phagotrophy. Average individual ciliate predation rates were up to 40-times higher than those of flagellates. These results were compared with similar data obtained from other authors in several aquatic systems. However, the population predation rates of flagellate protozoa were on average 6-times higher than that of ciliate protozoa, due to the low population numbers of the latter. Thus, flagellate protozoa can be considered as more important bacterial consumers than ciliates in this aquatic system.

A Technique for the Collection of Reticular Effluent of Sheep

Two sheep were equipped with rumen and omasal fistulae. A teflon tube with 1 mm outer diameter (OD) was permanently fixed between the abomasal fistula and the reticulo-omasal orifice. The effluent sampling tube was introduced through the abomasal cannula, through the omasal canal into the reticulo-omasal orifice by aid of the teflon tube. The technique allowed direct collection of reticular effluent from sheep. Intermittent flow of reticular effluent was observed. The moments of flow coincided with the end of the second phase of reticular contractions. From the flow pattern it was concluded that the motility of the reticulo-omasal orifice was not affected by the sampling procedure. From the similarities in the pH values, DM contents, and total protozoal counts in the effluent and in the reticular samples, it was concluded that representative samples of effluent could be obtained by the method. One animal was used for sampling for a period of eight months and then again 2 1/2 years later. A fraction of 97 to 98% of the DM present in the reticular effluent and in the reticular samples passed a sieve with 1 mm pore size. From the analyses of reticular content and reticular effluent it was concluded that the reticulo-omasal orifice does not have a significant discriminating function for the selective passage of particles and protozoa into the omasum.

Effects of a fat and ground maize supplement on feed intake and digestion by cattle consuming bermudagrass hay ( Cynodon dactylon)

Five beef cows (450 kg) and five Holstein steers (254 kg) were used in two Latin square experiments to determine the effects on intake and digestion of supplementing bermudagrass ( Cynodon dactylon) hay with maize and fat, singly and in combination, and to compare fat poured on hay with fat mixed with maize. The cows received hay at 1.0% of their body weight (BW) per day alone (control) or with ground maize (0.49% BW) and/or fat (0.054% BW, beef tallow). Treatments were control (C), maize alone (MZ), fat poured on hay alone (PF), maize plus poured fat (MZ-PF) and maize mixed with fat (MZ-MF). Calcium carbonate (0.011% BW) was given to all supplemented animals. Mean ruminal fluid protozoal counts were higher with than without supplements ( P < 0.05), for MZ than for PF, and for simultaneous vs. singular offering of maize and fat ( P < 0.05). Flows of microbial organic matter and nitrogen at the duodenum were higher with than without supplements, for MZ than for PF, and for MZ-MF than for MZ-PF. Digestion of neutral detergent fiber in the whole tract declined with supplementation, but differences among supplement treatments were not significant. In the second study, steers received hay ad libitum and higher levels of supplements (maize 0.89, fat 0.099 and calcium carbonate 0.021% BW day −1). Total dry matter intake was C 5.86, MZ 7.86, PF 6.83, MZ-PF 7.90 and MZ-MF 7.75 kg day −1, being affected by supplementation and higher for MZ than PF ( P < 0.05). Total tract neutral detergent fiber digestion was C 72.0, MZ 67.0, PF 69.2, MZ-PF 65.1, and MZ-MF 61.0%, and was depressed by supplementation and lower for simultaneous vs. singular supplementation with maize and fat ( P < 0.05). In conclusion, there were no advantages in intake or digestion to adding fat to supplemental maize either separately or mixed as compared with supplementation with maize alone.

EFFECT OF TANNIN CONTENT IN TWO ISOSYNTHETIC STRAINS OF BIRDSFOOT TREFOIL (Lotus corniculatus L.) ON FEED DIGESTIBILITY AND RUMEN FLUID COMPOSITION IN SHEEP

Low tannin (LT) and high tannin (HT) isosynthetic strains of birdsfoot trefoil containing 1 and 3% condensed tannins on a dry matter (DM) basis were cut fresh daily and fed to eight ruminally cannulated Suffolk wethers. Rumen fluid samples were collected before feeding and 3 and 6 h after feeding for pH, chlorophyll, supernatant protein nitrogen (N), ammonia nitrogen (NH3-N) and volatile fatty acids (VFA) determinations, and protozoa counts. Daily samples of the forage fed to the animals, and of feces, were analyzed for crude protein (CP) content, acid detergent fiber (ADF) and organic matter (OM). Results from rumen fluid analyses indicated that sheep receiving the HT strain had lower (P &lt; 0.01) supernatant protein N and NH3-N concentrations, and consistently but not significantly lower VFA and chlorophyll concentrations. Animals fed HT showed higher (P &lt; 0.05) protozoa counts than LT-fed animals, but only in the samples taken 3 h postfeeding. Ruminal pH was similar on LT and HT diets. Apparent digestibility of CP was 9% less (P &lt; 0.05) in sheep fed the HT strain. However, apparent digestibilities of DM, OM and ADF were not affected by the tannin level. Key words: Lotus corniculatus L., birdsfoot trefoil, tannin, digestibility, rumen, sheep