Sixteen Holstein rumen-cannulated primiparous milking dairy cows were fed a control diet (CN) based on maize silage and soyabean meal during a 4-week period before the start of a 21-d experiment with oilseeds containing high concentration of linoleic acid (Linola™) or linolenic acid (NuLin™). Thereafter, four cows received ad libitum one of each of four dietary treatments comprising of CN, Linola (LN), NuLin (NL) and LN/NL (50/50 % combination). Each LN, NL and LN/NL treatment contained 6 % oil of DM. Rumen digesta samples were collected on days 6, 11, 16 and 21 and milk samples on days 13, 15 and 17. There were no effects ( P >0·05) of the oilseeds on pH and concentrations of NH 3 -N and total volatile fatty acids, while the acetate:propionate ratio was decreased ( P < 0·05). The oilseeds also decreased ( P < 0·05) protozoa and increased ( P < 0·1) total cellulolytic bacteria in rumen fluid, especially when containing high dietary linoleic acid ( P < 0·05). The milk protein concentration was increased ( P < 0·1) by the dietary linoleic acid, which produced most beneficial results. It was concluded that supplements of linoleic acid in diets of ruminants might contribute to better digestion of dietary fibre and increased quality of milk.

The present results are the last part of a series of experiments conducted in this laboratory on metabolism of major individual rumen ciliate protozoa species and their combinations in sheep. These species were inoculated into the rumen of fauna-free (FF) sheep to study digestibility of dietary fibre and duodenal flow of N. Sixteen rumen- and duodenum-cannulated FF sheep were divided into four equal groups and used in the present experiment. One group remained FF, while the other three were each inoculated intraruminally with the Holotrich protozoa sp. (HT),Entodiniumsp. (EN) or total mixed fauna (TF). In comparison with the FF group, the HT did not affect (P>0·05) the duodenal flow of non-NH3-N and bacterial-N, while the flow was decreased (P < 0·05) by both the EN and TF populations. The digestibility of fibre was increased (P < 0·05) by both the EN and TF populations, but the results for the HT group were mostly similar to those for the FF sheep. The fibre digestibility in the stomach for TF was intermediate between that for EN and FF. It was concluded that except when fed high-carbohydrate diets, the presence in the rumen of the HT protozoa are of no significant value or major detriment to ruminant production.

Forty crossbred steers (initial liveweight: 339 ± 41 kg) were assigned to four equal groups in a 98-d feeding experiment to determine the effects of sodium bentonite supplements (2% of dietary dry matter) on their growth performance. The steers were fed ad libitum a total mixed ration based on direct-cut (two groups) or wilted (two groups) grass silage. One group of steers fed the same silage received the diet without supplementation (control), while the second group received the diet with the sodium bentonite supplement. The steers were housed in pens with electronic headgates in an unheated enclosed feedlot. Feed intake was recorded throughout the experiment and weighing conducted every 2 wk. Apparent digestibilities of dietary components were determined with four steers in a parallel 4 × 4 Latin square experiment. Feed intake, average daily gain (ADG) and the efficiency of feed utilization were higher (P < 0.05) in steers fed wilted than in those fed the poorly fermented direct-cut grass silage. Bentonite increased (P = 0.04) ADG in steers fed the direct-cut grass silage, but in those fed the wilted grass silage ADG was virtually the same for both the control or the bentonite-supplemented steers. Except for energy, digestibility of nutrients was superior (P ≤ 0.05) in the wilted than in the direct-cut grass silage, but there were no effects (P > 0.05) of bentonite. It was concluded that it may be useful to supplement poorly fermented direct-cut silage diets with sodium bentonite, but not those based on wilted grass silage. Key words: Feedlot steers, sodium bentonite, grass silage, growth performance

Three groups of 15 fauna-free (FF) lambs each were used to establish the effects of Isotricha sp. (IS) monofauna on the dietary copper (Cu) solubility in the stomach and on the concentration of Cu in the liver. One group remained FF (control) while the second and third groups were inoculated with IS and total mixed fauna (TF), respectively. All lambs were fed ad libitum a corn silage based diet for 168 d. Thereafter, the lambs were killed and livers, kidneys and stomachs were removed and sampled. Different fauna treatments did not affect (P > 0.1) growth performance parameters. In comparison with the FF sheep, both the TF and IS decreased (P < 0.05) the rumen solubility of Cu, but the decrease by IS (23%) was approximately half of that of TF (41%; P < 0.05). Similarly, TF and IS decreased the liver Cu concentration by 15% (P < 0.1) and 7.5% (P > 0.1), respectively. Although TF that significantly decreased the bioavailability of dietary Cu included IS and Dasytricha species, it appears that an absence of these Holotrich protozoa from the rumen protozoa population would not have a significant effect on the efficiency of the population to alleviate chronic copper toxicity in sheep. Key words: Isotricha, rumen, ciliate protozoa, lambs, copper

Three groups of five wethers with ruminal and duodenal cannulas and maintained as either fauna-free (FF) or inoculated with total mixed fauna (TF) or Entodinium caudatum as a single-species monofauna (EN) were used in an experiment with two 28 d periods. In the first period, the sheep were fed a control barley-based diet (40:60 concentrate to silage DM) and in the second period the diet was supplemented with 187 g DM of Enterolobium cyclocarpum for the last 12 d of the period. The diets of period 1 and 2 were isonitrogenous. There was no effect of fauna on apparent ruminal and total tract organic matter and fibre digestion, but bacterial and microbial N flow and efficiency were improved in FF sheep compared to TF sheep. In period 2, protozoal numbers were reduced between 31 and 88 % 2 h after feeding E. cyclocarpum for the third to twelfth day of supplementation and by an average of 25 % in samples collected over the 24 h feeding cycle. Supplementation of the diet with E. cyclocarpum and the consequent protozoal reduction in TF and EN sheep improved the flow of non-ammonia N and bacterial N to the small intestine and the efficiency of microbial synthesis. However, E. cyclocarpum reduced ruminal organic matter digestion, especially in faunated sheep, and total tract organic matter, N and fibre digestion. Thus, a reduction in the protozoal cell numbers of 25 % was sufficient to achieve the beneficial effects of reduced fauna on the bacterial protein supply, but diet digestibility was reduced.

Three groups of five rumen and duodenum cannulated fauna-free sheep were used in a 28d experiment. One group remained fauna-free, whereas the second (EN) and third (PP) groups, respectively, were inoculated intraruminally with the protozoan species Entodinium caudatum and Polyplastron multivesiculatum . Rumen fluid, duodenal digesta and faecal samples were collected during the last 12d. The flow of digesta to the duodenum was determined using Yb and Co as dual-phase markers. 15 Nitrogen and phosphatidylcholine were used as markers to calculate the duodenal flow of bacterial and protozoal N, respectively. Results showed an increase ( P <0·1) in the rumen concentration of NH 3 -N and total volatile fatty acids, and a decrease ( P <0·05) in the duodenal flow of non-NH 3 -N and bacterial N in sheep with EN and PP monofaunas, compared with fauna-free sheep. There were no differences ( P >0·05) in these variables between the two monofauna groups. Protozoal N accounted for 8% of the duodenal non-NH 3 -N flow in the EN-monofaunated sheep, whereas no such flow was detected in the PP-monofaunated sheep. Apparent rumen digestibility of organic matter, neutral detergent fibre and acid detergent fibre were similar ( P >0·05) in the monofaunated groups of sheep, but rumen acid detergent fibre digestibility was higher (P<0·05) in the monofaunated than in the fauna-free groups. Experimental results suggested that, unlike EN, the PP monofauna might not contribute to the duodenal flow of microbial protein, whereas both monofaunas showed a virtually equal degree of predation on rumen bacteria.

High linoleic acid sunflower oil (HLSO) was included at 0, 3, 6, or 9% [dry matter (DM) basis] in barley-based finishing diets offered to 60 steers fed individually (n = 15 per dietary treatment). Trends toward improved average daily gain (ADG) (by 13% with 6% HLSO; quadratic, P = 0.08) and feed efficiency (by 7%, linear, P = 0.09) were observed. Steers tolerated 9% HLSO with no adverse effect on performance. Key words: Carcass characteristics, growth performance, linoleic acid, sunflower oil

Antiprotozoal activity of dietary supplements of tannin, saponin, and linoleic acid were tested with four ruminally and duodenally cannulated heifers in a 4×4 Latin square experiment. The four dietary treatments were control (basal diet), quebracho (source of tannin), quillaja (source of saponin), and safflower oil (source of linoleic acid). The basal diet was based on rolled barley grain and barley silage. Three additional experimental diets were prepared by incorporating in the basal diet (g/kg of dry matter) quillaja extract (8); quebracho (6); or high linoleic acid safflower oil (27); replacing equal amounts of barley grain. The diets were fed as total mixed rations in four experimental periods of 47 days. Safflower oil caused a log reduction in numbers of protozoa as compared to the control, whereas the protozoa populations in the rumen of heifers fed quabracho, quillaja were only slightly lower than that of the control. On all diets, the proportion of Entodinia in the total protozoa population was more than 0.85. Cellulolytic, amylolytic and deaminative enzyme activities as well as concentrations of ammonia and volatile fatty acids in ruminal fluid were not affected by treatment. There was no indication that dietary supplements altered digestibility or the flow of non-ammonia nitrogen or bacterial nitrogen to the duodenum. It was concluded that although the supplements tended to lower the number of protozoa in ruminal fluid, this decline was not sufficient to significantly decrease predation of bacteria. Consequently, neither reduction in rumen ammonia nor an increase in duodenal flow of bacterial nitrogen to the duodenum was observed. Administering these additives in concentrations that are high enough to reduce protozoal numbers, without having adverse affects on feed intake or digestibility, may be difficult.

Thirty-eight midlactating Holstein cows averaging 597 kg of body weight (SD = 59) were used to determine the effects of dietary flaxseed on protein requirement and N excretion in urine and feces. Milk yield and composition, intake, and digestibility were also determined. Cows were allotted from wk 20 to 30 of lactation to 1 of 4 TMR containing 1) no flaxseed (control) and 16% protein (MPC), 2) whole flaxseed and 16% protein (MPF), 3) no flaxseed (control) and 18% protein (HPC), and 4) whole flaxseed and 18% protein (HPF). Cows fed high protein diets had greater feed intake than those fed medium protein diets (20.2 vs. 18.4 kg/d), and cows fed no flaxseed had greater dry matter intake than those fed flaxseed (20.1 vs. 18.5 kg/d). Milk yield was lower for cows fed MPF (20.3 kg/d) than for those fed HPC (24.4 kg/d), HPF (24.9 kg/d), or MPC (24.0 kg/d). Milk protein and lactose concentrations were similar for cows fed MPC and HPC, but flaxseed decreased milk protein concentration in cows fed MPF or HPF compared with cows fed the control diets. Milk fat concentration was similar in cows fed diets with or without flaxseed, but it was decreased by higher protein concentration. Digestibility was generally reduced when diets contained flaxseed and lower protein concentration. Dietary protein had no effect while dietary flaxseed increased fecal N excretion. Retention of N was lower in cows fed flaxseed compared with cows fed the control diets. Feeding flaxseed decreased milk concentrations of short- and medium-chain fatty acids and increased those of long-chain fatty acids. Flaxseed had no effect on the dietary requirement of N by midlactating dairy cows.

The conjugated linoleic acid (CLA) concentration in milk and the lactation performance of cows fed either a control (CON) or a sunflower seed [SS; 7% of dietary dry matter (DM)] containing diet were compared in a 12-wk lactation trial, starting from week 3 after calving, with 17 multiparous and 8 primiparous cows. The CON and SS diets were isonitrogenous and provided 4 and 6% crude fat in the total mixed rations and were fed to 13 and 12 cows, respectively. Daily DM intake (DMI ), milk production and weekly body weights were recorded. Milk samples collected weekly at four consecutive milkings were individually analyzed for fat, protein and lactose content, and fatty acid composition. The DMI and milk production of the cows fed t he CON and SS diets were 20.5 ± 0.80 and 20.2 ± 0.80 kg d-1 (P > 0.05) and 38.2 ± 1.71 and 38.2 ± 1.71 kg d-1 (P > 0.05), respectively. No differences due to diet were observed for cow body weight, body condition score, or for content and yield of milk fat, protein and lactose. The CLA cis-9, trans-11 concentration in milk from cows fed the CON and SS diets was 3.9 and 7.9 mg g-1 fatty acids (P < 0.01), respectively. The average CLA cis-9, trans-11 yield in milk from cows fed CON and SS diets was 5.1 ± 0.07 and 10.9 ± 0.07 g d-1, respectively, or 114% greater (P < 0.05) for cows fed the SS diet. The study indicates that sunflower seed inclusion at 7% of dietary DM to dairy cows increases the CLA concentration and yield in milk, without affecting DMI, milk production or composition. Key words: Conjugated linoleic acids, cow, milk, sunflower seed

Two experiments in a 2×2 factorial design were conducted with weaned lambs to determine the effects of supplementing either high forage (Experiment 1; 140d) or grain (Experiment 2; 70d) diets containing either 12 or 16% protein without or with sunflower seed (SS) supplement (14% of diet dry matter [DM]) on plasma cholecystokinin (CCK) concentration, and on absolute viscosity, protein, starch and fat content, and amylase activity in digesta collected from different parts of the small intestine. There were four treatment groups in each experiment with 11 or 12 lambs (five or six wethers and six ewes) per treatment group in Experiments 1 and 4, 8-lamb (ewes only) groups in Experiment 2. Each group was fed one of four experimental diets based on corn silage, corn grain and soybean meal in Experiment 1, and on barley grain, straw and soybean meal in Experiment 2. Soybean meal was used to achieve the appropriate concentration of dietary protein in both experiments, while straw was used in Experiment 2 to achieve equal dietary fiber in all diets. Concentrations of CCK were determined in jugular plasma obtained from each lamb (4h after feeding) 6 weeks after the initiation of the experiment. After the end of the experiments all lambs were sacrificed and the digesta sampled within 15min of slaughter from 50cm sections of proximal, mid jejunal and distal small intestine. In Experiment 1, dietary SS increased (P<0.05) plasma CCK concentrations of ewe lambs fed the high protein diet, but reduced (P<0.05) digesta viscosity to 45.2±14.4cP from 226.0±70.2cP across all intestinal sections in all lambs fed the low protein diets. In lambs fed the low protein diet with SS, digesta fat content was increased across all sections. Digesta protein content was 61.9±8.22% in ewe lambs fed the high protein diet in proximal intestinal sections relative to 38.9±7.08% in lambs fed the low protein diet but neither dietary protein nor supplementation with SS had any effect on the amylase activity (μM reducing sugars released g−1DMmin−1). In Experiment 2, dietary SS decreased (P<0.05) viscosity of small intestinal digesta of lambs to 3.2±32.6cP, in the distal regions of lambs fed the low protein diets relative to those receiving no SS (348±79.8cP). Small intestinal digesta protein was higher (P<0.05) in lambs fed high protein diets with SS and the amylase activity as μM reducing sugars released g−1DMmin−1 was increased (P<0.05) in these animals as well. Dietary SS was effective in altering digesta viscosity and protein content in lambs irrespective of protein content of the diet, but the activity of the amylase was substantially increased by higher dietary protein in the barley grain based diets.

The value of sunflower seed (SS) in finishing diets was assessed in two feeding trials. In Exp. 1, 60 yearling steers (479 +/- 45 kg) were fed five diets (n = 12). A basal diet (DM basis) of 84.5% steam-rolled barley, 9% barley silage, and 6.5% supplement was fed as is (control), with all the silage replaced (DM basis) with rolled SS, or with grain:silage mix replaced with 9% whole SS, 14% whole SS, or 14% rolled SS. Liver, diaphragm, and brisket samples were obtained from each carcass. In Exp. 2, 120 yearling steers (354 +/- 25 kg) were fed corn- or barley-based diets containing no SS, high-linoleic acid SS, or high-oleic acid SS (a 2 x 3 factorial arrangement, n = 20). Whole SS was included at 10.8% in the corn-based and 14% in the barley-based diets (DM basis). In Exp. 1, feeding whole SS linearly increased DMI (P = 0.02), ADG (P = 0.01), and G:F (P = 0.01). Regression of ME against level of whole SS indicated that SS contained 4.4 to 5.9 Mcal ME/kg. Substituting whole for rolled SS did not significantly alter DMI, ADG, or G:F (8.55 vs. 8.30 kg/d; 1.36 vs. 1.31 kg; and 0.157 vs. 0.158, respectively). Replacing the silage with rolled SS had no effect on DMI (P = 0.91) but marginally enhanced ADG (P = 0.10) and improved G:F (P = 0.01). Dressing percent increased linearly (P = 0.08) with level of SS in the diet. Feeding SS decreased (P < 0.05) levels of 16:0 and 18:3 in both diaphragm and subcutaneous fats, and increased (P = 0.05) the prevalence of 18:1, 18:2, cis-9,trans-11-CLA and trans-10,cis-12-CLA in subcutaneous fat. In Exp. 2, barley diets supplemented with high-linoleic SS decreased DMI (P = 0.02) and ADG (P = 0.007) by steers throughout the trial, whereas no decrease was noted with corn (interaction P = 0.06 for DMI and P = 0.01 for ADG). With barley, high-linoleic SS decreased final live weight (554 vs. 592 kg; P = 0.01), carcass weight (329 vs. 346 kg; P = 0.06), and dressing percent (58.5 vs. 59.4%; P = 0.04). Steers fed high-linoleic SS plus barley had less (P < 0.05) backfat than those fed other SS diets. No adverse effects of SS on liver abscess incidence or meat quality were detected. Although they provide protein and fiber useful in formulating finishing diets for cattle, and did improve performance in Exp. 1, no benefit from substituting SS for grain and roughage was detected in Exp. 2. Because of unexplained inconsistencies between the two experiments, additional research is warranted to confirm the feeding value of SS in diets for feedlot cattle.

The objective of this study was to investigate the effects of sodium salts of individual fatty acids on protozoal numbers and ruminal fermentation variables in vitro. Ruminal inoculum was obtained from two heifers fed a finishing diet consisting of (DM basis) 90% rolled barley grain, 4% barley silage, 5% soybean meal, and 1% mineralized salt. Fatty acids (FA) were included individually in the inoculum as follows: C6:0, C8:0, and C10:0 at concentrations (wt/vol) of 0.0625, 0.125, and 0.25%; C14:0 and C18:0 at concentrations of 0.125, 0.25, and 0.5%; and C12:0, C16:0, C18:1, C18:2, and C18:3 at concentrations of 0.25, 0.5, and 1.0%. 15N-Labeled casein was included as a N tracer. In the presence of medium-chain saturated FA (particularly C10:0 and C12:0), no ciliate protozoa (99.8%Entodinium spp.) were recovered from the incubation medium. Long-chain unsaturated FA (C18:3, C18:2, C18:1) also decreased (P < 0.05) protozoal numbers. At all concentrations tested, C10:0 and C12:0 decreased (P < 0.05) ammonia and total VFA concentrations (by 29 and 22%, respectively) and increased (P < 0.05) concentrations of total free amino acids, reducing sugars, and soluble protein. At the greatest concentrations of these FA, xylanase and amylase activities of the incubation media were decreased (P < 0.05). The C18 unsaturated FA increased (P < 0.05) the polysaccharide-degrading activities of the media. These in vitro results suggest that long-chain unsaturated FA in combination with medium-chain saturated acids have the potential to decrease protozoal numbers and ruminal ammonia utilization in cattle fed high-grain diets.

Linoleic acid-rich sunflower-seed supplements (SSS) were used in two experiments (experiment 1, high-concentrate diets; experiment 2, high-forage diets) to study effects on rumen protozoa and the growth of lambs. Both experiments consisted of four treatments, two with a low-protein diet (120 g/kg) and two with a high-protein diet (160 g/kg). For both diets, one treatment was without (control) and one with the SSS (140 g/kg dietary DM). The lambs were fed ad libitum for 70 and 140 d in experiments 1 and 2, respectively. Thereafter, the digestibility of organic matter (OM), acid-detergent fibre and neutral-detergent fibre were determined for each diet with four lambs, and then all lambs were slaughtered and rumen fluid samples were collected and analysed. The results showed substantial decreases (P<0·001) or total elimination of protozoa in the rumen fluid of the SSS-receiving lambs. In the first experiment the SSS also decreased (P<0·05) feed intake, but an increase in average daily gain (P<0·06) resulted in an improved (P<0·05) feed:gain ratio. Also, the SSS increased (P<0·05) the digestibility of fibre. In the second experiment the SSS decreased (P<0·05) the OM digestibility, feed intake and growth of lambs. It was concluded that the use of sunflower-seed supplementation in high-concentrate diets of ruminants reduces rumen fauna, resulting in savings on dietary protein supplements and an increased digestion of feed.

The antiprotozoal activity of Enterolobium cyclocarpum foliage was tested in the present study in in vitro, using a technique that measures the breakdown of [14C]-labelled Selenomonas ruminantium, and in vivo experiments. In vivo, the activity was measured in two experiments with rumen cannulated sheep fed a diet based on barley silage and barley grain. Rumen fluid samples were collected and used in both experiments for enumeration of protozoa and analysis of rumen fermentation parameters. The in vitro assay showed a 20–95% decrease in the rate of breakdown of [14C]-labelled S. ruminantium by protozoa with increased amounts of E. cyclocarpum in the incubation media, ranging from 0.5 to 10gl−1. The results of the first in vivo experiment with sheep showed that the E. cyclocarpum supplement reduced (P<0.05) protozoal numbers during days 4–11 (by 49–75%), but the numbers gradually increased to the level of the control group by day 20. The reduction in the protozoal population was associated with a reduced (P<0.1) concentration of ammonia-N in rumen fluid. pH and volatile fatty acid (VFA) concentrations were not affected by the treatment (P>0.05). The results of the second experiment showed that compared to day −1, there were reduced (P<0.05) protozoa concentrations in rumen fluid on almost all days during Period 1, but protozoa were reduced (P<0.05) only on days 6, 8 and 21 in Period 3. Comparison of Periods 1 and 3 resulted in lower (P<0.05) protozoal concentration means in Period 1 on days 3–6, but the rest of the days were not different (P>0.05). It was concluded that the antiprotozoal effect of the E. cyclocarpum foliage supplement was only transitory and effective only the first time it was fed to the same animals.

Eighteen rumen cannulated sheep in three groups of six were supplemented with tea seeds at 0 (control), 3 or 6% of the dietary dry matter in a 22-d experiment. Rumen fluid samples were collected on 3 d before and on various days during the experiment. The concentration of protozoa in rumen fluid was not affected by the tea seed supplements (P > 0.05), but the numerical concentration of the Entodinium genera declined by 12% (P < 0.05) and that of cellulolytic protozoa increased by 90% (P < 0.05) due to the 6% tea seed supplement. The associated percentage in the rumen ciliate protozoa population of the cellulolytic protozoa increased (P < 0.05) and that of the Entodinium genera decreased (P < 0.05) due to the 6% supplement. There were no effects (P > 0.05) of the 3% tea seed supplement on the protozoa population parameters. Since ammonia and volatile fatty acid concentrations were not affected (P > 0.05) it was apparent that the tea seed supplements did not influence rumen fermentation. The positive effect of the 6% tea seed supplement on the ciliate protozoa population obtained in the present study was relatively modest. Because the seeds contain astringent properties, higher than 6% dietary supplements of tea seeds can be harmful to animals. It was therefore concluded that tea seeds are of no apparent value as an antiprotozoal dietary component in ruminant production. Key words: Tea seeds, ciliate protozoa, rumen fluid, sheep

The diet is the source of many essential fatty acids such as linoleic and linolenic acids for all mammals. These fatty acids either, as altered isomers or as other elongated products, have been found to provide unique advantages to human health. Currently two conjugated linoleic acids (CLA) isomers (cis-9, trans-11 C18:2; trans-10, cis-12 C18:2) and two elongated products of linolenic acid [eicosapentaenoic acid (EPA, C20:5 n-3), docosahexaenoic acid (DHA, C22:6 n-3)] have been recognized for their roles in maintaining human health. Consumers can obtain these functional fatty acids from beef if the feeding management of beef cattle can be altered to include precursor fatty acids. Diet, breed, and gender are important factors that affect total fat content and/or the fatty acid profile of beef with regard to CLA, EPA, and DHA. Diet provides the precursor fatty acids that are altered and deposited, and breed dictates, the amount of fat that is deposited. These fatty acids can be increased in beef by increasing the forage:concentrate ratio, inclusion of non-fermented forage, and supplementation with various oils or oil seeds. The CLA and vaccenic acid (trans-11 C18:1) concentration in beef was increased by feeding sunflower oil or seeds, linseed, and soybean oil supplemented diets, while cattle fed linseed and fish oil supplemented diets had increased concentrations of EPA and DHA. Although the concentration of these fatty acids can be increased in beef, there is a need to further the understanding of the mechanism by which they exert positive affects on human health. Key words: Cattle, beef, fatty acids, conjugated linoleic acid, eicosapentaenoic acid, docosahexaenoic acid

The effects of 14 bioactive agents on ruminal fermentation and protozoal activity were investigated in vitro as potential feed additives to improve feed efficiency. Agents studied were: lecithin, herring meal, canola oil, coconut oil, linseed oil, palm oil, and soybean oil, with each oil at final concentrations of 0.5, 1.0 and 2.0%; the saponin-containing plants Yucca schidigera (yucca) and Quillaja saponaria Molina (quillaja), tannic acid, and bentonite, each at 0.1, 0.2, and 0.4%; the surfactant Tween 80 (at 0.05, 0.1, and 0.2%); and the ionophores monensin (at 2.5, 5.0, and 10 mg/l) and salinomycin (at 1.25, 2.5, and 5.0 mg/l). Duplicate 4 h incubations each included controls (no additives) and 15N labeled casein as a N tracer. Yucca, tannic acid and both ionophores decreased (P<0.05) NH3 concentrations. Total free amino acids (TFAA) were decreased (P<0.05) by yucca and by bentonite, but were increased (P<0.05) by fish meal, monensin and salinomycin. Tannic acid and bentonite reduced (P<0.05) total VFA concentrations, and tannic acid reduced (P<0.05) the acetate:propionate (A:P) ratio. Bentonite, tannic acid, palm oil, quillaja and salinomycin reduced (P<0.05) carboxymethylcellulase (CMCase), xylanase, and amylase activities, whereas monensin, lecithin, Tween 80, yucca, and the feed oils (except coconut) decreased (P<0.05) amylase activity only. Protozoal populations, which comprised 84% Entodinium spp., decreased (P<0.05) with tannic acid, lecithin and quillaja. Tannic acid, fish meal, and the ionophores reduced (P<0.05) the rate of protozoal engulfment of bacteria. Fish meal and salinomycin, and the higher concentrations of quillaja and Tween 80 depressed (P<0.05) incorporation of 15N from casein into bacterial cells. Only lecithin effectively reduced protozoal numbers, by 27%, without impeding the extent of 15N incorporation into bacteria.

The effects of feeding a linoleic acid-rich sunflower seed supplement and different levels of dietary protein on protozoal numbers and fermentation parameters in rumen fluid were determined in an 84-d experiment with rumen-cannulated sheep. The experiment comprised four treatments, two with low crude protein diets [12% of dietary dry matter (DM)] and two with high protein diets (16% of DM). On both low and high protein diets, one treatment was without (Control) and one with the sunflower seed (high linoleic acid variety 6150) supplement (14% of dietary DM). The four diets used were based on corn silage and corn grain, and soybean meal was used to achieve the desired concentration of dietary protein. The sheep were fully fed each morning and rumen fluid samples were taken 2 h later on various days of the experiment (daily during the first 14 d for enumeration of protozoa). In addition, rumen fluid was sampled at different hours after feeding on day 43 of the experiment. Results showed a protozoa-decreasing effect (P < 0.001) of sunflower seeds causing a decline in protozoa numbers after 2 d of supplementation. The effect of protein on protozoa numbers was dependent on the presence of sunflower seed supplement. Measurements on day 43 showed increased protozoa numbers (P < 0.05) and ammonia nitrogen concentrations (P < 0.001) due to higher dietary protein, and decreased protozoal numbers (P < 0.05) and ammonia nitrogen (P < 0.001) due to the sunflower seed supplement, without significant effects (P > 0.05) on volatile fatty acid concentrations. The linoleic acid-rich sunflower seed supplement was highly effective in reducing both protozoa numbers and ammonia nitrogen concentrations in rumen fluid. Key words: Rumen ciliate protozoa, sunflower seeds, dietary protein, sheep