In vitro effects of individual fatty acids on protozoal numbers and on fermentation products in ruminal fluid from cattle fed a high-concentrate, barley-based diet

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.     

Effects of DL-malate on ruminal metabolism and performance of cattle fed a high-concentrate diet.

To determine the effects of DL-malate on ruminal metabolism, four steers equipped with ruminal cannulas were fed an 80% rolled grain (75% corn:25% wheat) diet twice daily with a DMI equal to 2.0% of BW (485+/-24.8 kg). DL-Malate was infused into the rumen on two consecutive days in 500 mL of phosphate buffer to provide 0, 27, 54, or 80 g of DL-malate/d. Ruminal pH linearly increased (P < .01) with DL-malate concentration and was greater (P < .01) for DL-malate than for the control steers (6.07 vs 5.77). DL-Malate treatment linearly decreased (P < .10) total VFA and tended to linearly increase (P = .10) acetate concentration. Propionate, butyrate, and L-lactate concentrations and acetate:propionate ratio were not affected (P > .10) by DL-malate. Three finishing studies were conducted to determine the effects of feeding DL-malate on growth rate and feed efficiency. In a 98-d experiment, 33 crossbred steers were randomly allotted in a Calan gate feeding system to three DL-malate levels (0, 40, and 80 g/d). Steers (initial weight = 367+/-4.5 kg) were fed a rolled corn-based diet twice daily. After 84 d on feed, gain efficiency (gain:feed) tended to improve with more DL-malate (linear, P < .10) and was 8.1% greater (P < .05) for DL-malate than for the control. The ADG linearly increased (P < .05) with more DL-malate and was 8.6% greater (P = .10) for DL-malate than for the control. After 98-d on feed, ADG was linearly increased (P = .09) by DL--malate, and the greatest increase occurred with 80 g of DL-malate. In the second performance study, 27 Angus steers were randomly allotted in a Calan gate feeding system to three DL-malate concentrations (0, 60, and 120 g/d). Steers (initial weight = 432+/-4.6 kg) were fed diets used in the first finishing study twice daily, but DL-malate was included during the 10-d step-up period. During the 10-d step-up period, feed efficiency and ADG linearly increased (P = .01) with more DL-malate. DL-Malate had little effect on steer and heifer performance or plasma constituents in a 113-d finishing study. Collectively, these results suggest that feeding DL-malate to cattle consuming high-grain diets alleviates subclinical acidosis, and it improved animal performance in two finishing studies.     

Effects of feeding frequency on intake, ruminal fermentation, and feeding behavior in heifers fed high-concentrate diets

Four ruminally fistulated Holstein heifers (BW = 385 +/- 6.2 kg) were used in a 4 x 4 Latin square experiment to determine the effect of feeding frequency on intake, water consumption, ruminal fermentation, and feeding and animal behavior. The treatments consisted of different feeding frequencies: a) once daily (T1); b) twice daily (T2); c) 3 times daily (T3); and d) 4 times daily (T4). Heifers were offered ad libitum access to concentrate and barley straw. Feeding frequency did not affect DMI (P >0.10), but water consumption tended to increase linearly as feeding frequency increased (P = 0.08). Average ruminal pH was not affected (P >0.10) by feeding frequency, but at 12 h after feeding ruminal pH was greater for T2 than for the other treatments. Total VFA concentration and VFA proportions were not affected (P >0.10) by feeding frequency, except valerate proportion, which increased linearly (P = 0.05) as feeding frequency increased. The concentration of ammonia-N was affected (P <0.05) cubically as feeding frequency increased (greatest for T3 = 9.3 mg of N/100 mL; lowest for T2 = 7.2 mg of N/100 mL). Feeding frequency had no effect on daily percentages of behavioral activities (P >0.05), except for observational behavior, for which there was a linear decrease as feeding frequency increased (P = 0.02). Heifers spent the same time on chewing activities, independent of feeding frequency. However, meal criteria tended to be affected (P = 0.07) by feeding frequency, with T2 (39.4 min) showing the longest intermeal interval. Total daily meal time, meal frequency, and meal size were not affected by feeding frequency (P >0.10), whereas meal length and eating rate showed cubic tendencies (P = 0.10 and P = 0.06, respectively) as feeding frequency increased. These results suggest that in the present experimental conditions, with heifers fed high-concentrate diets and with noncompetitive feeding, a smaller range of ruminal pH values was observed when feed was offered twice daily. Although heifers spent the same time on chewing activities, more stable ruminal conditions were probably achieved by feeding twice daily due to the rumination pattern, which was more constant during daytime in T2 than in T1. Moreover, when daytime and nighttime ruminating activity were analyzed separately, this activity was different in T1 (17.3 vs. 30.8%, respectively; P <0.05) but not in T2 (21.5 vs. 28.0%, respectively; P >0.05).     

Effect of grain processing and silage on microbial protein synthesis and nutrient digestibility in beef cattle fed barley-based diets

Effects of the extent of grain processing and the percentage of silage in barley-based feedlot diets on microbial protein synthesis and nutrient digestibility were evaluated using four steers (initial BW of 442 +/- 15 kg) with ruminal and duodenal cannulas. The experiment was a 4 x 4 Latin square with four periods of 21 d each. Dietary treatments were arranged as a 2 x 2 factorial with two levels of barley silage (20 and 5% DM basis) and two degrees of barley grain processing (coarsely and flatly steamrolled to a processing index [PI] of 86 and 61%, respectively). The PI was quantified as the volume weight of the barley grain after processing, expressed as a percentage of the volume weight prior to processing. Digest a flow (Yb) and microbial (15N) markers were continuously infused into the rumen for a period of 13 d. Ruminal, duodenal, and fecal samples were collected at various times over the last 6 d of marker infusion. Diurnal ruminal pH was measured for 48 h. Intake of DM averaged 1.8% of BW, and was not different among the dietary treatments (P > 0.10). Ruminal starch digestibility was higher (P < 0.05) for the more extensively processed grain and tended (P < 0.10) to be highest when the more extensively processed grain was combined with 5% barley silage. In contrast, ruminal fiber digestibility for the 5% silage diets was reduced (P < 0.05) when the grain was more extensively processed. There was, however, no effect of grain processing on ruminal OM digestibility (P > 0.10), and hence, no inhibitory effect on microbial N flow to the intestine (P > 0.10). There was also no effect of the level of silage on microbial N flow (P > 0.10), but there was a tendency for improved efficiency of microbial protein synthesis for the 20% silage diets (P = 0.072). Ruminal escape of nonmicrobial N (P = 0.003) was greater, and thus, protein flow to the intestine was greater for the 5% silage diets. Diurnal ruminal pH was lower (P < 0.05) for 11 of the 24 hourly time points in steers fed the 5% silage diets than those fed the 20% silage diets. In conclusion, barley grain rolled to a PI of 86 to 61% and combined with 20 and 5% barley silage had little effect on microbial protein supply. Microbial protein supply was not inhibited when the barley grain was extensively processed (PI of 61%) and the silage was limited to only 5% of the diet DM, but feed intake of steers in this study was lower than would be expected in the feedlot.     

Effects of feeding polyclonal antibody preparations on ruminal bacterial populations and ruminal pH of steers fed high-grain diets

Three experiments with factorial arrangements of treatments were designed to test the efficacy of avian-derived polyclonal antibody preparations (PAP) against Streptococcus bovis (PAP-Sb) or Fusobacterium necrophorum (PAP-Fn) in reducing ruminal counts of target bacteria in beef steers supplemented or not with feed additives (300 mg of monensin/d and 90 mg of tylosin/d; MT). Feeding increasing doses of PAP-Sb in Exp. 1 or a single dose in Exp. 2 reduced S. bovis counts in a cubic fashion (P = 0.014). In Exp. 1 and 2, inclusion of MT in the diet had no effect (P > 0.05) on ruminal S. bovis counts. In Exp. 2, ruminal pH was increased (P < 0.05) by feeding PAP-Sb, MT, and PAP-Sb plus MT. Ruminal F. necrophorum counts were reduced by feeding PAP-Fn (P = 0.002) and MT (P < 0.001). Reduction in ruminal F. necrophorum counts was greater (P = 0.008) when feeding MT alone than when feeding PAP-Fn and MT together. In Exp. 3, ruminal S. bovis counts were not affected (P = 0.64) by PAP-Fn. Ruminal pH was not affected (P = 0.61) by feeding PAP-Fn, and the total anaerobic bacterial count was not affected (P > 0.05) by either PAP-Sb or PAP-Fn in Exp. 1 or Exp. 3. In conclusion, PAP of avian origin and against S. bovis or F. necrophorum were effective in reducing target ruminal bacterial populations. These PAP could be effective in preventing the deleterious effects associated with these bacteria, and possibly in enhancing animal performance.     

Influence of dietary urea level on digestive function and growth performance of cattle fed steam-flaked barley-based finishing diets

Four Holstein steers (282 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to evaluate the influence of dietary urea level (0, 0.4, 0.8, and 1.2%, DM basis) in a steam-flaked barley-based finishing diet on digestive function. There were no treatment effects (P > 0.20) on ruminal digestion of OM and ADF. Increasing dietary urea level increased (linear, P < 0.01) ruminal starch digestion. Ruminal degradability of protein in the basal diet (no supplemental urea) was 60%. Increasing dietary urea level did not increase (P > 0.20) ruminal microbial protein synthesis or nonammonia N flow to the small intestine. There were no treatment effects (P > 0.20) on total-tract ADF digestion. Total tract digestion of OM (quadratic, P < 0.01) and starch (linear, P < 0.05) increased slightly with increasing urea level. Urea supplementation increased (linear, P < 0.01) ruminal pH 1 h after feeding; however, by 3 h after feeding, ruminal pH was lower (cubic, P < 0.05) with urea-supplemented diets. Urea supplementation did not affect (P > 0.20) ruminal molar proportions of acetate and propionate. One hundred twenty crossbred steers (252 kg; approximately 25% Brahman breeding) were used in an 84-d feeding trial (five pens per treatment) to evaluate treatment effects on growth performance. Daily weight gain increased (linear, P = 0.01) with increasing urea level, tending to be maximal (1.53 kg/d; quadratic, P = 0.13) at the 0.8% level of urea supplementation. Improvements in ADG were due to treatment effects (linear, P < 0.01) on DMI. Urea supplementation did not affect (P > 0.20) the NE value of the diet for maintenance and gain. Observed dietary NE values, based on growth performance, were in close agreement with expected based on tabular values for individual feed ingredients, averaging 100.4%. We conclude that with steam-flaked barely-based finishing diets, ruminal and total-tract digestion of OM and ruminal microbial protein synthesis may not be increased by urea supplementation. In contrast, ADG was optimized by dietary inclusion of 0.8% urea. Urea supplementation may not enhance the net energy value of steam-flaked barely-based finishing diets when degradable intake protein is greater than 85% of microbial protein synthesis.     

Relationship between feeding behavior and performance of feedlot steers fed barley-based diets

The relationship between feeding behavior and performance of 274 feedlot cattle was evaluated using Charolais cross steers from 2 consecutive years averaging 293 ± 41 kg for yr 1 (n = 115) and 349 ± 41 for yr 2 (n = 159). Steers were blocked by BW and assigned to 3 (yr 1) or 4 (yr 2) feedlot pens equipped with a radio frequency identification system (GrowSafe Systems). Each pen contained 5 feeding stalls that allowed individual animal access to a feed tub suspended on load cells. The system recorded animal identification, duration, and frequency of feedings as well as the amount of feed consumed during each visit. Daily variation in DMI (DVI), calculated as the absolute difference in DMI from one day to the next, as well as eating rate were determined for each steer. Barley-based diets were delivered to meet steer ad libitum intake over the 213- and 181-d feeding periods for yr 1 and 2 of the study, respectively. The backgrounding periods included the first 85 and 56 d of yr 1 and 2, respectively, in which steers were fed a 14 to 30% concentrate diet, whereas the finishing periods included the last 116 and 101 d of feeding in yr 1 and 2, respectively, with the diet consisting of 77.9% concentrate. Steers were weighed individually every 14 d. To relate feeding behavior to performance, steers were grouped by ADG and G:F and categorized as high, average, or low (based on 1 SD greater than and less than the mean). In the backgrounding and finishing periods of both years of the study, steers classified as having high ADG exhibited greater (P < 0.001) DVI than steers classified as having average or low ADG. Total daily DMI was also greater (P < 0.001) for steers in the high ADG group than those in the low ADG group. Overall, those steers with the greatest G:F also tended (P = 0.15) to have greater DVI than average or low G:F steers. Compared with average or low G:F steers, DMI by high G:F steers in both years of the study was less during backgrounding, finishing, and overall (P = 0.02). Bunk visits and bunk attendance duration were less frequent and shorter (P ≤ 0.01) overall for high compared with low G:F steers. In this study, steers with more variable eating patterns exhibited greater ADG and tended to have greater G:F, a finding that is contrary to industry perception.     

Pilocarpine and digestive efficiency in beef cattle fed a high-concentrate diet

The effect of pilocarpine HCl, a parasympathetic muscarinic agonist, on digestive characteristics was evaluated in growing beef steers fed a high-grain diet. Oral doses of 0, 2 or 4 mg/kg BW were administered daily to each of eight steers immediately prior to offering an 88% concentrate: 12% hay diet in this three-period crossover design (19 d/period). Treatments did not improve digestibilities of dry matter, organic matter and nitrogen, ruminal liquid volume and fractional dilution rate, body weight gain or feed efficiency. Although daily voluntary feed intake was not altered by treatment (P = .25), there was a dose-dependent slowing of the rate at which feed was consumed (P less than .01). Also, ruminal fluid pH was increased with increasing dose (5.36, 5.55 and 6.11 respectively; P = .10). These observations indicate that the digestive improvements due to pilocarpine reported to occur in mature, nongrowing cattle consuming a high-forage diet are not observed in growing steers fed a production-type diet.     

Effects of supplementation with narasin,salinomycin, or flavomycin on performance and ruminal fermentation characteristics of Bos indicus Nellore cattle fed with forage-based diets

The aim of the present study was to evaluate the inclusion of narasin, salinomycin, or flavomycin for 140 d on ruminal fermentation parameters, apparent nutrient digestibility, and performance of Nellore cattle offered a forage-based diet. In experiment 1, 32 rumen-cannulated Bos indicus Nellore steers [initial body weight (BW) = 220 ± 12.6 kg] were assigned to individual pens in a randomized complete block design according to their initial shrunk BW. Within block, animals were randomly assigned to 1 of 4 treatments: (1) forage-based diet without feed additives (CON; n = 8), (2) CON diet plus 13 ppm of narasin (NAR; n = 8), (3) CON diet plus 20 ppm of salinomycin (SAL; n = 8), or (4) CON diet plus 3 ppm of flavomycin (FLA; n = 8). The experimental period lasted 140 d and was divided into 5 periods of 28 d each. The inclusion of feed additives did not impact (P ≥ 0.17) dry matter intake (DMI), nutrient intake, and apparent total tract digestibility of nutrients. Nonetheless, steers fed NAR had lower (P < 0.01) molar proportion of acetate compared with CON, SAL, and FLA steers, whereas ruminal acetate tended to be greater (P < 0.09) for SAL vs. CON and FLA, but did not differ (P = 0.68) between CON vs. FLA steers. Ruminal propionate was the highest (P < 0.01) for steers fed NAR and did not differ (P > 0.20) between CON, SAL, and FLA. Consequently, NAR steers had the lowest (P < 0.01) Ac:Pr ratio, whereas Ac:Pr did not differ (P > 0.18) among CON, SAL, and FLA. Total volatile fatty acids were greater (P < 0.04) for NAR and CON vs. SAL and FLA, but did not differ (P > 0.67) among NAR vs. CON and SAL vs. FLA. In experiment 2, 164 Nellore bulls (initial shrunk BW = 299 ± 2.5 kg) were assigned to feedlot pens for 140 d in a randomized complete block design. Within block (n = 10), animals were randomly assigned to the same treatments used in experiment 1. Average daily gain was greater (P < 0.01) in NAR vs. CON, SAL, and FLA bulls, and did not differ (P > 0.12) between CON, SAL, and FLA bulls. Bulls fed NAR had greater (P < 0.02) DMI (as kg/d or % BW) and final shrunk BW compared with CON, SAL, and FLA bulls, whereas DMI and final shrunk BW did not differ (P > 0.26) between CON, SAL, and FLA bulls. Feed efficiency, however, was not impacted (P = 0.51) by any feed additives used herein. Collectively, narasin was the only feed additive that benefited performance and ruminal fermentation of Nellore animals fed a forage-based diet.     

Differential responses to dietary cobalt in finishing steers fed corn-versus barley-based diets

An experiment was conducted to determine the effects of dietary Co concentration on performance, carcass traits, and plasma, liver, and ruminal metabolites of steers fed corn- or barley-based diets. Sixty steers, initially averaging 316 kg, were stratified by BW and assigned randomly to treatments in a 2 x 3 factorial arrangement, with factors being a corn- or barley-based diet and supplemental Co added at 0, 0.05, or 0.15 mg/kg of DM. Control corn-and barley-based diets analyzed 0.04 and 0.02 mg of Co/kg of DM, respectively. Steers were fed individually using electronic Ca-lan gate feeders. Cobalt supplementation increased (P < 0.05) DMI and ADG over the total study. From d 85 to finish, Co supplementation increased (P < 0.05) ADG by steers fed corn- but not barley-based diets. The G:F was increased (P < 0.05) by Co supplementation during the first 84 d but not over the entire finishing period. Average daily gain and G:F were greater (P < 0.05) for corn- vs. barley-fed steers. Supplemental Co increased vitamin B12 in plasma and liver (P < 0.05), and plasma vitamin B12 was greater (P < 0.05) in steers fed corn-vs. barley-based diets. Cobalt supplementation increased (P < 0.05) ruminal fluid vitamin B12 on d 84 in steers fed corn- but not barley-based diets. Folate was greater in plasma (P < 0.01) and liver (P < 0.05) of steers fed Co-supplemented diets. Increasing supplemental Co from 0.05 to 0.15 mg of Co/kg of DM increased (P < 0.05) liver folate in steers fed barley- but not corn-based diets. Supplemental Co decreased (P < 0.01) plasma methylmalonic acid concentration in steers. Increasing supplemental Co from 0.05 to 0.15 mg/kg of DM decreased plasma and ruminal succinate concentrations, and steers fed barley-based diets had greater (P < 0.05) plasma and ruminal succinate relative to those fed corn-based diets. Addition of supplemental Co to the basal diets increased (P < 0.01) plasma glucose concentrations of steers, and steers fed corn-based diets had greater plasma glucose than those fed barley-based diets. Steers supplemented with Co had greater ruminal propionate (P < 0.01) and lesser (P < 0.05) ruminal acetate and butyrate proportions than controls. Supplemental Co increased dressing percent (P < 0.10) and HCW (P < 0.01) at slaughter. These results indicate that feeding steers corn- or barley-based diets deficient in Co adversely affects performance and vitamin B12 status.     

Influence of malic acid supplementation on ruminal pH, lactic acid utilization, and digestive function in steers fed high-concentrate finishing diets

Two trials were conducted to evaluate the influence of malic acid supplementation on ruminal fermentation. In Trial 1, six Holstein steers (300 kg) with ruminal cannulas were used in a crossover design experiment to study the influence of malic acid (MA) on ruminal metabolism during glucose-induced lactic acidosis. Treatments consisted of a 77% steam-flaked barley-based finishing diet supplemented to provide 0 or 80 g/d of MA. After a 13-d dietary adjustment period, 1 kg of glucose was infused into the rumen 1 h after the morning feeding. Ruminal pH was closely associated (R2 = .70) with ruminal DL-lactate concentration. Malic acid supplementation increased (P < .01) ruminal pH 3 h after the glucose infusion. However, there were no treatment effects (P > .10) on ruminal VFA molar proportions or ruminal and plasma DL-lactate concentrations. In Trial 2, four Holstein steers (150 kg) with cannulas in the rumen and proximal duodenum were used in a crossover design experiment to evaluate the influence of MA supplementation on characteristics of digestion. Treatments consisted of an 81% steam-flaked barley-based finishing diet supplemented to provide 0 or 80 g/d of MA. There were no treatment effects (P > .10) on ruminal and total tract digestion of OM, ADF, starch, and feed N or on ruminal microbial efficiency. Malic acid supplementation increased (P < .05) ruminal pH 2 h after feeding. As with Trial 1, there were no treatment effects (P > .10) on ruminal VFA and DL-lactate concentrations. We conclude that supplementation of high-grain finishing diets with MA may be beneficial in promoting a higher ruminal pH during periods of peak acid production without detrimental effects on ruminal microbial efficiency or starch, fiber, and protein digestion. There were no detectable beneficial effects of MA supplementation on ruminal and plasma lactic acid concentrations in cattle fed high-grain diets.     

Changes in ruminal fermentation and protein degradation in growing Holstein heifers from 80 to 250 kg fed high-concentrate diets with different forage-to-concentrate ratios

Six Holstein heifers (initial BW = 65.2 +/- 1.8 kg) fitted with ruminal cannulas were used in a repeated measures trial to assess the effect of age and forage-to-concentrate ratio on ruminal fermentation end products and in situ degradation kinetics of four plant protein supplements (soybean meal, sunflower meal, peas, and lupin seeds). Alfalfa hay also was incubated in situ to estimate NDF degradation. Three experimental periods were conducted at 13, 27, and 41 wk of age. Heifers were fed one of two diets, 12:88 vs. 30:70 forage-to-concentrate ratio (DM basis), offered as total mixed ration on an ad libitum basis. Intakes of DM, OM, CP, NDF, and ADG were not affected (P > or = 0.105) by diet. The 30:70 diet resulted in faster (P = 0.045) fluid passage rate and decreased (P = 0.015) ammonia N concentration compared with the 12:88 diet, but no differences (P > or = 0.244) were detected in ruminal pH and total VFA concentration between diets. The rate of degradation and the effective degradability of N in protein supplements was greater with the 30:70 diet for peas (P < or = 0.008) and lupin seeds (P < or = 0.02), and in the 12:88 diet for sunflower meal (P < or = 0.06). Degradation of NDF of alfalfa hay was low with both diets (18.5 and 23.7 % for 12:88 and 30:70, respectively); however, the rate and extent of DM and NDF degradation were greater (P < or = 0.016) with the 30:70 diet, suggesting a higher cellulolytic activity. Total VFA concentration and the proportion of propionate increased (P < or = 0.035), and the acetate proportion decreased (P = 0.021) with age. Average pH, ammonia N concentration, and passage rates were not affected (P > or = 0.168) by age. Degradation rate and effective degradability of N of sunflower meal, peas, lupin seeds, and of DM of alfalfa hay increased (P < or = 0.08) with age, but degradation kinetics of NDF of alfalfa hay was not affected (P > or = 0.249). The increase in the rate and extent of N degradation with age would suggest an increase in proteolytic activity, and the changes in the fermentation pattern may reflect an increase in amylolytic activity caused mainly by an increase in the gross intake of nonstructural carbohydrates and by adaptation of ruminal microflora after long exposure to these nutrients.     

Methane emissions from feedlot cattle fed barley or corn diets

Methane emitted from the livestock sector contributes to greenhouse gas emissions worldwide. Understanding the variability in enteric methane production related to diet is essential to decreasing uncertainty in greenhouse gas emission inventories and to identifying viable greenhouse gas reduction strategies. Our study focused on measuring methane in growing beef cattle fed corn- or barley-based diets typical of those fed to cattle in North American feedlots. The experiment was designed as a randomized complete block (group) design with two treatments, barley and corn. Angus heifer calves (initial BW = 328 kg) were allocated to two groups (eight per group), with four cattle in each group fed a corn or barley diet. The experiment was conducted over a 42-d backgrounding phase, a 35-d transition phase and a 32-d finishing phase. Backgrounding diets consisted of 70% barley silage or corn silage and 30% concentrate containing steam-rolled barley or dry-rolled corn (DM basis). Finishing diets consisted of 9% barley silage and 91% concentrate containing barley or corn (DM basis). All diets contained monensin (33 mg/kg of DM). Cattle were placed into four large environmental chambers (two heifers per chamber) during each phase to measure enteric methane production for 3 d. During the backgrounding phase, DMI was greater by cattle fed corn than for those fed barley (10.2 vs. 7.6 kg/d, P < 0.01), but during the finishing phase, DMI was similar for both diets (8.3 kg/d). The DMI was decreased to 6.3 kg/d with no effect of diet or phase while the cattle were in the chambers; thus, methane emissions (g/d) reported may underestimate those of the feedlot industry. Methane emissions per kilogram of DMI and as a percentage of GE intake were not affected by grain source during the backgrounding phase (24.6 g/kg of DMI; 7.42% of GE), but were less (P < 0.05) for corn than for barley during the finishing phase (9.2 vs. 13.1 g/kg of DMI; 2.81 vs. 4.03% of GE). The results indicate the need to implement dietary strategies to decrease methane emissions of cattle fed high-forage backgrounding diets and barley-based finishing diets. Mitigating methane losses from cattle will have long-term environmental benefits by decreasing agriculture's contribution to greenhouse gas emissions.     

Effect of ruminal dosing of mechanical stimulating brush on carcass characteristics and fatty acid composition of dressed carcass fat in fattening Holstein steers fed with high-concentrate diets

This experiment was undertaken to examine the effect of dosing of a mechanical stimulating brush (RF) in the rumen on dressed carcass characteristics and on the fatty acid composition of dressed carcass fat in fattening beef cattle. The fattening trial was carried out with high-concentrate diets (organic cell wall contents: 27.5% on a dry mater basis) in eight Holstein steers (12 months of age). Four of the experimental animals were orally dosed with three RF/head (RF group); the other four animals without RF dosing were allotted as the control group. Grass hay was fed to the animals (0.2 kg/head/day) until 19 months of age. Concentrate diet was given ad libitum during the experiment. There were no statistical differences between the RF group and the control group in yield score and meat quality score of dressed carcass characteristics. Regarding fatty acid composition of dressed carcass fat, the proportion of C18 : 2 fatty acids in subcutaneous fat in the RF group was greater ( P  < 0.05) than that in the control group. C16 : 0 fatty acids in kidney fat in the RF group was lower ( P  < 0.05), and C18 : 2 fatty acids and total unsaturated fatty acids of 18 carbon number in kidney fat in the RF group were higher ( P  < 0.05) compared with the control group. The proportion of C18 : 2 fatty acids in rib eye fat in the RF group was greater ( P  < 0.05) than that in the control group. C18 : 1 fatty acids, C18 : 2 fatty acids and total unsaturated fatty acids of 18 carbon number in rib fat in the RF group were greater ( P  < 0.05) than those in the control group. The results suggest that in fattening Holstein steers fed with high-concentrate diets, the effect of ruminal RF dosing on dressed carcass characteristics is not significant, but the proportion of unsaturated fatty acid of carcass fat is increased.     

Effects of pasteurization of potato slurry by-product fed in corn-or barley-based beef finishing diets

Pasteurization of vegetable by-products such as potato slurry (PS) before feeding may be necessary to prevent the spread of pathogens and beef carcass blemishes. We hypothesized that pasteurization would increase ruminal fermentability of PS starch. Four ruminally cannulated crossbred beef steers (initial BW = 432) were used in a 4 x 4 Latin square experiment with a 2 x 2 factorial arrangement of treatments to examine the main effects and interactions of pasteurization (54.4 degrees C for 2 h) of PS and grain type (GT; dry-rolled corn and barley) on ruminal and total tract digestion of beef finishing diets. Diets contained 7% alfalfa hay and 14% PS (DM basis) and were fed ad libitum three times daily. Corn-based diets had 71.7% corn, whereas barley-based diets had 60% barley and 11.7% corn. Pasteurization resulted in greater (P = 0.004) soluble, rapidly degradable starch (34.3 vs. 26.7% for pasteurized and nonpasteurized PS, respectively). Ruminal fluid pH was more acidic (P < 0.07) for corn-based diets than for barley-based diets (P = 0.07) at 0200 and 2100 (sample time x GT; P < 0.05). Ruminal fluid pH was more acidic (P = 0.06) at 1400 for corn-based diets containing pasteurized PS compared with other dietary treatments (sample time x pasteurization x GT; P = 0.04). Minimum and maximum ruminal pH were greater (P < 0.10) for barley-based diets than for corn-based diets. Ruminal fluid pH was < 6.0 for a greater (P = 0.04) proportion of the day for corn-based compared with barley-based diets. In vitro incubation measurements revealed that pasteurization of PS resulted in lower (P = 0.06) ruminal fluid ammonia N concentration. Ruminal fluid ammonia N concentration was lower (P = 0.11) for barley-based diets than for corn-based diets. Steers fed barley-based diets had greater (P = 0.02) DMI and lesser (P < 0.05) total tract digestibility of DM and ADF compared with steers fed corn diets. Pasteurization increased (P = 0.10) total tract starch digestibility. Results indicate pasteurization increased rapidly degradable starch, ruminal starch fermentability, and total tract starch digestibility of PS. Grain type interacted with pasteurization such that feeding corn-based diets containing pasteurized PS resulted in periodic reductions in ruminal pH. Feeding management may be more critical when feeding pasteurized PS in beef finishing diets.     

Effects of calcium source and level on site of digestion and calcium levels in the digestive tract of cattle fed high-concentrate diets

The effect of calcium (Ca) source and level on site of digestion of an 88% concentrate diet was tested with four 431-kg, intestine-cannulated steers in a 4 X 4 Latin square experiment. Diets, limit-fed at 1.3% of body weight, contained .25% Ca with no supplemental Ca (B), .40 or .48% Ca from addition of either .95% CaCl2-2H2O (Cl) or .65% CaCO3 (LL), or 1.11% Ca from addition of 2.5% CaCO3 (HL). No effects of source of Ca (CaCl2-2H2O vs CaCO3) were observed, although ruminal pH and ruminal ammonia-nitrogen (N) concentrations tended to be lower with Cl. Ruminal fluid dilution rate increased linearly (P less than .05) with the addition of Ca to the diet. Ruminal fluid dilution rate and volume were negatively related (r = -.72; P less than .01). Organic matter (OM) and starch digestibilities in the rumen tended to decline with the addition of Ca to the diet, while postruminal OM and starch disappearance increased (P less than .05) to compensate. Flow of N to the duodenum decreased (P greater than .05) with addition of Ca to the diet. Concentrations of soluble Ca found in ruminal and duodenal fluid increased linearly (P less than .05) with dietary Ca intake. Intestinal Ca disappearance increased linearly and quadratically (P less than .05) with increasing dietary Ca and exceeded 80% of Ca entering the small intestine. In a second experiment, the rate of in situ dry matter (DM) disappearance of rolled corn was not greatly altered by addition of Ca to the diet.     

Ruminal ciliated protozoa in cattle fed finishing diets with or without supplemental fat

Ruminal samples were collected at slaughter from 364 unfasted steers fed different finishing diets to obtain information on numbers and species distribution of ciliated protozoa in feedlot cattle. Total numbers of protozoa averaged 1.59 X 10(5)/g of ruminal contents. A total of 47 steers (12.9%) were defaunated, but 4.1% of the steers possessed numbers of protozoa greater than 10(6)/g. Entodinium species did not always dominate the protozoan populations; 41 faunated steers (11.2%) were devoid of entodinia, and 79 additional steers (21.7%) possessed populations dominated (greater than 50%) by other genera. Isotricha was the most commonly occurring genus supplanting Entodinium, but Polyplastron and Epidinium were frequently present in high concentrations. Tallow and soybean soapstock supplementation reduced (P less than .05) numbers of protozoa in steers consuming wheat diets. However, yellow grease supplementation did not affect numbers of protozoa in steers fed either sorghum or corn diets. Average ruminal pH was 6.20 on the wheat diet, 6.05 on the corn diet, and 5.69 and 6.23 for the two sorghum diets, respectively. We found no correlation between ruminal pH and numbers of protozoa on any diet. The presence of relatively high protozoan concentrations and few defaunated animals in feedlot cattle necessitates reevaluation of the role that ciliated protozoa play in ruminal metabolism of animals fed processed, high-concentrate diets.     

Rumen ciliate protozoal fauna of native sheep, friesian cattle and dromedary camel in Libya.

Rumen ciliate species and composition were surveyed on the native sheep, Friesian-cattle and dromedary (one-humped) camels kept in Libya. As a result of survey, 5 genera including 14 species with 5 formae in native sheep, 9 genera including 27 species with 6 formae in Friesian-cattle and 6 genera including 13 species and 7 formae in dromedary camels were identified. All of the ciliate species and their percentage composition detected from the Libyan sheep and cattle in this examination were similar to those found from corresponding animals in the other countries. Libyan camels lacked some peculiar ciliate species found from camels in the other countries, but had many cosmopolitan species common with those in the domestic ruminants, suggesting that ciliate faunae of camel are easily affected by the other domestic ruminants kept together. The ciliate density was estimated as 105/ml in every host species.     

Growth, feed intake, carcass characteristics, and eating behavior of feedlot lambs fed high-concentrate diets containing soybean hulls

The objectives of this experiment were to determine the effects of replacing ground corn with soybean hulls (SH) in high-concentrate diets on the growth (56-d period), carcass characteristics, and eating behavior of feedlot lambs. Sixty-four Santa Inês ram lambs (18.3 ± 2.8 kg of BW and 69 ± 5 d of age) were assigned to a randomized complete block design experiment with 8 blocks and 4 diets. The control diet contained 10% coastcross (Cynodon sp.) hay, 70% corn, and no SH (SH0) in the dietary DM. In the remaining diets, SH replaced corn at the rate of 15 (SH15), 30 (SH30), or 45% (SH45) of the original corn concentration, resulting in 0, 10.5, 21.0, or 31.4% SH in the dietary DM. Dry matter intake increased linearly (P < 0.01) when SH replaced ground corn (1.0, 1.0, 1.1, and 1.1 kg/d for SH0, SH15, SH30, and SH45, respectively). There was no effect on ADG of lambs, with values of 276, 278, 282, and 287 g for SH0, SH15, SH30, and SH45, respectively. Feed efficiency decreased linearly (P < 0.01) with SH inclusion. Carcass measures were not affected by SH as a replacement for ground corn. Eating time, expressed as minutes per day and minutes per gram of NDF, showed a quadratic effect (P < 0.05), whereas no effect was observed when expressed as minutes per gram of DM. Rumination, in minutes per day, was not influenced by dietary SH inclusion, but a linear decrease (P < 0.01) was observed when this variable was expressed as minutes per gram of NDF. Soybean hulls can replace up to 45% of the ground corn (31.4% of SH in the dietary DM) in high-concentrate diets fed to feedlot lambs without negative effects on ADG and carcass measures. The linear decrease in feed efficiency (11.6% reduction from SH0 to SH45) suggests that optimal dietary SH inclusion rates should be dictated by the relative costs of SH and corn.