Brome Hay Research Articles

Induction of pulsatile secretion of leptin in horses following thyroidectomy

Endocrine characteristics of Quarter Horse-type mares were determined during a 68 h feed deprivation and again in the same mares following surgical thyroidectomy (THX). A crossover experimental design was implemented, in which mares received brome hay available ad libitum (FED) or were food deprived (RES) for 68 h. Blood samples were collected every 20 min for 48 h, beginning 20 h after the onset of food deprivation. Concentrations of triiodothyronine and thyroxine were undetectable post-THX. Plasma concentrations of thyrotropin were greater post-THX versus pre-THX (P<0 x 001). Plasma concentrations of leptin were greater in the THX FED group than in the THX RES group (P<0 x 01). The existence of leptin pulse secretion was found only in post-THX compared with the same horses pre-THX (P=0 x 02). We theorize that non-pulsatile secretion of leptin may have contributed to the survival of this species, as it evolved in the regions of seasonal availability of food. Lack of pulsatile secretion of leptin may contribute to the accumulation of energy stores by modulating leptin sensitivity.

Effect of fiber-based creep feed on intake, digestion, ruminal fermentation, and microbial efficiency in nursing calves1

Six Angus crossbred cow-calf pairs (653 +/- 35 kg and 157 +/- 10 kg initial BW for cows and calves, respectively) were used to evaluate the influence of a fiber-based creep feed on intake, ruminal fermentation, digestion characteristics, and microbial efficiency in nursing beef calves. Cow-calf pairs were stratified by calf age and assigned randomly to one of two treatments: control (no supplement) or supplemented. Supplemented calves received 0.9 kg of a 49% soy hulls, 44% wheat middlings, 6% molasses, and 1% limestone supplement (DM basis) daily. All calves were cannulated in the rumen and duodenum and given ad libitum access to chopped brome hay (Bromus inermus L; 7.43% CP, 40.96% ADF, and 63.99% NDF; DM basis). Supplementation was initiated on May 1 (88 +/- 10.3 d calf age). Three sampling periods were conducted throughout the study (June 14 to 25, July 5 to 16, and August 9 to 20). Supplement and forage were offered at 0800 daily. Total, hay, and milk OM intakes of nursing calves were not affected by supplementation (2,014 vs. 2,328 +/- 288.8, 1,486 vs. 1,029 +/- 3,06.9, and 528 vs. 575 +/- 87.0 g/d, respectively). Milk OM intake was less (P < 0.09) in August than in June and July (635, 691, and 345 +/- 110.6 g/d for June, July, and August, respectively). A supplementation x month interaction occurred (P < 0.10) for total-tract OM digestion. Supplementation did not affect (P > 0.40) total-tract OM digestibility during June and August; however, during July, total-tract OM digestibility was lower (P = 0.03) for the control calves. Ruminal ammonia concentration, total VFA, and butyrate molar proportion increased (P < 0.05), whereas acetate proportion decreased (P = 0.01) in supplemented calves. Microbial efficiency was not influenced by supplementation (11.8 vs. 12.0 g/kg of OM truly fermented for control and supplemented calves, respectively). These data indicate that fiber-based supplements can be used as creep feed without negative effects on OM intake, total-tract OM digestibility, and ruminal fermentation characteristics in nursing beef calves.

Nitrogen balance in lambs fed low-quality brome hay and infused with differing proportions of casein in the rumen and abomasum12

Twenty wether lambs (46 +/- 2 kg) fitted with ruminal and abomasal infusion catheters were used in a completely randomized design to determine the effects of differing proportions of ruminal and abomasal casein infusion on N balance in lambs fed low-quality brome hay (0.8% N, DM basis) for ad libitum intake. Wethers were infused with 0 (control) or 10.7 g/d of N from casein with ratios of ruminal:abomasal infusion of 100:0 (100R:0A), 67:33 (67R:33A), 33:67 (33R:67A), or 0:100% (0R:100A), respectively, over a 12-d period. Total N supply (hay N intake + N from casein infusion) was greater (P = 0.001) in lambs receiving casein infusion than in controls. Urinary N excretion (g/d) was greater (P = 0.001) in lambs receiving casein infusion than in controls. Urinary N excretion decreased as casein infusion was shifted from 100R:0A to 33R:67A and then slightly increased in lambs receiving 0R:100A (quadratic, P = 0.02). Total N excretion was greater (P = 0.001) in lambs receiving casein infusion than in controls and decreased linearly (P = 0.005) as casein infusion was shifted to the abomasum. Retained N (g/d, % of N intake, and % of digested N) was greater (P = 0.001) in lambs receiving casein than in controls. Retained N increased as infusion was shifted from 100R:0A to 33R:67A and then slightly decreased in lambs receiving 0R: 100A (quadratic, P < 0.07). Based on regression analysis, the predicted optimum proportion of casein infusion to maximize N retention was 68% into the abomasum. The regression suggests that supplementation with undegradable intake protein had an additional benefit over supplementation with ruminally degradable intake protein (100R:0A) and that changing the percentage of ruminally undegradable intake protein in supplemental protein from 33 to 100% resulted in minimal differences in N retention. Apparent N, DM, OM, and energy digestibility (% of intake) was greater (P < 0.03) in lambs infused with casein than controls but did not differ among casein infusion groups. These data suggest that feeding protein supplements containing a portion (greater than 0%) of the crude protein as ruminally undegradable intake protein, as compared to 100% ruminally degradable intake protein, to lambs consuming low-quality forage increases N retention and the efficiency of N utilization without influencing total-tract nutrient digestion.

Nitrogen balance in lambs fed low-quality brome hay and infused with differing proportions of casein in the rumen and abomasum12

Nitrogen balance in lambs fed low-quality brome hay and infused with differing proportions of casein in the rumen and abomasum12

Effects of route of administration of a commercially available Mannheimia (pasteurella) haemolytica vaccine on titer levels (2004)

One hundred thirteen Hereford x Angus heifer calves (average weight = 515 lb) were allotted to one of three treatments: 1) control, no vaccine; 2) a 2-cc subcutaneous injection of One-Shot (Pfizer Animal Health), a Mannheimia (pasteurella) haemolytica vaccine, three weeks before weaning; or 3) a 1⁄2-cc intradermal injection of One-Shot, three weeks before weaning. All heifers were weighed and blood samples harvested at time of injection, three weeks later at weaning, and then 28 days later. After weaning, heifers were confined to a common pen and fed freechoice brome hay and approximately 5 lb/head daily of a concentrate. Blood samples from 30 heifers were shipped to a laboratory for titer analysis. No differences were found in animal performance and sickness during the preconditioning period. Heifers injected by the subcutaneous route had greater increases in whole-cell and leukotoxin-neutralizing antibody titer levels than the intradermal or control treatments. These data suggest that beef producers should follow label recommendations for dosage and route of administration to maximize vaccine efficacy. Introduction

Temporal responses in energy expenditure and respiratory quotient following feeding in the muskox: influence of season on energy costs of eating and standing and an endogenous heat increment

Seasonal energy metabolism was investigated in young (2- to 3-year-old) muskoxen (Ovibos moschatus) during the winters of 1994 (January–April) and 1996 (January) and summer of 1995 (July and August). Energy expenditure (EE) increased 35%–42% following a meal of chopped brome hay (Bromus inermis) and declined as a double-exponential process over 8 h. The mean energy cost of eating (321 and 361 J·g dry matter–1) was lower in winter than in summer, and declined with body mass (BM) (r2 = 0.58). The mean energy cost of standing was 21% (SE = 2.7%) higher than that of bedding. Prefeeding energy expenditure (EEp) was 26% higher in summer than in winter. An endo genous heat increment, measured as EEp – EE, at 7-8 h post feeding was lower (P &lt; 0.001) in winter than in summer (39 and 58 kJ·kg BM–0.75·d–1, respectively). Mean cumulative EE (minus activity costs) for 8 h post feeding was 124 (SE = 4) and 148 (SE = 4) kJ·kg BM–0.75 (P &lt; 0.001) in winter and summer, respectively. Respiratory quotients (RQs) &gt;1 were recorded during feeding in winter and a mean RQ of 0.9 was recorded in summer. Seasonal EEp, postfeeding EE, and RQ are consistent with a low cost of maintenance metabolism in winter and an increased requirement for productivity in summer.

The effect of dietary energy source on serum concentration of insulin-like growth factor-I growth hormone, insulin, glucose, and fat metabolites in weanling horses.

Feeding diets high in soluble carbohydrates to growing horses has been implicated in the development of orthopedic diseases; as a result, substitution of dietary fat for soluble carbohydrates has received attention. Because IGF-I is integral to growth and cartilage development and because it is influenced by nutrition, we evaluated the effect of dietary fat substitution on metabolic endpoints and circulating GH and IGF-I in growing horses. Twelve Quarter Horse weanlings, four female and eight male, 151 to 226 d old, were blocked by sex and age and assigned to two treatment groups. Group one (CARB; n = six) was fed a concentrate containing 2.21% fat and 33.9% starch; group two (FAT; n = six) was fed a concentrate containing 10.3% fat and 24.0% starch. Both concentrates contained 3.0 Mcal/kg of DE and 16% CP. Brome hay also was fed. Diets were fed at 0800 and 1600 for 60 d. On d 0, 30, and 60, blood samples were obtained via a jugular catheter from 1 h before until 5 h after the morning feeding. Serum was analyzed for glucose, insulin, GH, IGF-I, NEFA, and total cholesterol (CHOL). Neither ADG (0.85 +/- 0.04 and 0.84 +/- 0.04 kg) nor concentrate DMI (4.04 +/- 0.12 and 4.03 +/- 0.12 kg/d) differed between treatments. There were consistent increases in glucose and insulin in response to feeding on d 0, 30, and 60 for both groups. On d 30, the glucose response to feeding was less (P = 0.07) over time in FAT vs. CARB; however, there were no significant treatment x time effects on d 0 or 60. On d 60, the insulin response to feeding was less (P < 0.05) over time in FAT compared with CARB; however, there was no treatment x time effect on d 0 or 30. Serum CHOL concentrations did not differ between groups on d 0. Horses in the FAT group had increased CHOL concentrations on d 30 and 60 compared with CARB (P < 0.01). Although treatment x time interactions were noted for GH on d 30 and 60 (P < 0.05), only transient and inconsistent differences in the secretory profiles between CARB and FAT treatments were evident at those sampling times. Serum NEFA and IGF-I did not differ between treatments on d 0, 30, or 60. These results suggest that dietary energy source, at least at the level used in this study, did not affect foal growth performance or serum IGF-I and NEFA concentrations. Fat substitution increased serum CHOL and variably affected serum GH, glucose, and insulin concentrations in response to feeding.

Supplementation strategies for forage-fed beef steers (2000)

A comparison was made of different supplementation strategies for steer calves wintered on brome hay for 109 days. Treatments consisted of no supplement, 1.33 lb/head daily of a 30% protein range cube, a commercially available free-choice block supplement containing 40% crude protein (19% as non-protein nitrogen), and a soy-based block supplement containing soy solubles and full-fat soybeans with 40% crude protein (25% as nonprotein nitrogen). Following the backgrounding phase, steers were placed onto finishing rations and fed for an additional 152 days before being slaughtered. Gain during the growing phase was greater for all supplemented cattle than for unsupplemented controls. Cattle fed blocks or no supplement tended to compensate during the finishing phase, suggesting that differences in gastrointestinal tract fill may have impacted body weights at the end of the back grounding phase. When performance was evaluated over the entire 261-day trial, cattle fed blocks were more efficient than controls, whereas efficiencies of cattle fed range cubes were essentially equal to those of cattle that previously received no supplement. Additionally, soybean solubles and full-fat soybeans were viable alternatives to traditional ingredients for manufacturing free-choice block supplements.

Low- and high-quality forage utilization by heifers and mature beef cows.

Eight cows (7 to 9 yr old, 522 kg) and six heifers (10 mo old, 169 kg) were fed either alfalfa hay (18.7% CP) or mature brome hay (5.1% CP) to determine the effect of cattle age on apparent forage utilization. Cattle were fitted with ruminal and duodenal cannulas and were individually fed once daily (ad libitum intake, 1000). The split-plot design consisted of age (whole-plot) and two sampling periods feeding alfalfa or brome hay (subplot). Each period consisted of 28 d: d 1 to 13 for adaptation, d 13 to 20 for feed intake determination, and d 20 to 28 for sampling. Nylon bags containing NDF substrate from alfalfa or brome hay were incubated ruminally for 0, 3, 6, 12, 24, 48, 96, and 192 h to determine the rate and extent of fiber degradation. Ruminal liquid dilution rate and fermentation characteristics were conducted on d 27. Ruminal fill was determined by total evacuation at 0800 on d 28. Cows consumed more feed (BW.75; P<.01) and had greater ruminal OM fill (P = .04) but had similar fluid fill (P = .88) compared with heifers. Ruminal liquid dilution rate was greater in cows than in heifers (P<.01). The rate of in situ NDF degradation was 3 and .5% per hour greater in cows than in heifers when alfalfa and brome hay were fed, respectively (age x hay, P<.01). Ruminal NDF digestibility as a percentage of intake was greater in cows than in heifers (P<.01). Numbers of ruminal cellulolytic bacteria were not affected by treatment (P>.21). These data indicate that mature cows have a smaller ruminal fluid fill that turns over more rapidly, and this may be responsible for a faster rate of ruminal fiber degradation in cows than in young heifers.

Effects of cooked molasses blocks on intake and digestion by steers fed brome hay with or without alfalfa (1999)

This study was conducted to determine how cattle fed medium to high quality forages respond to supplementation with cooked molasses blocks. Responses to blocks were measured for steers fed each of three different hays ad libitum: 1) brome containing 8.4% CP and 72% NDF, 2) alfalfa containing 19.2% CP and 52% NDF, and 3) brome fed ad lib and supplemented daily with 5 lb/day of the alfalfa (MIX). Eighteen steers (622 lb) were used for two periods. Six steers received each of the forages, and each steer was supplemented with the block in only one of the two periods. Blocks were fed once daily and removed after the appropriate amount had been consumed. Block intakes averaged .66 lb of dry matter daily (.55 lb OM) and were similar among forages. Forage organic matter (OM) intake was not affected by the block when brome (9.8 lb/day) or MIX (11.6 lb/day) was fed, but it decreased from 15.4 to 14.4 lb/day when the block was supplemented to alfalfa. Digestibility of OM was greater (P<.05) for alfalfa (61.0%) than brome (55.7%) or MIX (57.5%) and was not impacted by block supplementation. Digestible OM intake was greater (P<.05) for alfalfa (9.3 lb/day) than brome (5.6 lb/day) or MIX (6.8 lb/day) and was not greatly impacted by block supplementation. Thus, supplementation with a cooked molasses-urea block had only small effects on intake and digestion of medium to high quality forages.

Effects of supplemental degradable intake protein on intake and digestibility of low-quality brome hay (1998)

The effects of increasing levels of degradable weight and assigned to one of four increasing intake protein (DIP) on intake and digestion of levels of DIP. Each steer was offered brome hay low-quality brome hay were evaluated using 16 at 130% of the average voluntary intake for the ruminally fistulated beef steers. Trends were preceding 5-day period. Supplemental DIP evident for small, positive changes in total intake (sodium caseinate; 91.6% CP, 100% DIP) was and digestion with increasing level of DIP ruminally infused at 7:00 AM, immediately prior supplementation. As a result, total digestible to feeding forage to provide .041, .082, and OM intake (TDOMI) increased with DIP .124% BW/day; controls received none. The supplement-ation but tended to plateau below forage contained 65.4% NDF and 5.9% CP, of the highest supplementation level. which 49% was DIP. DIP was estimated using

Relationship betweenin vitrogas production and NIRS predicted enzymatic digestibility and chemical composition

Rumen fermentability of raw materials and foods can be evaluated by different means. Recently a large interest has been generated by the use ofin vitrogas production associated with the degradation and fermentation kinetics of forages and concentrates. Measuring and modelling gas production have been studied (Beuvink, 1993) and implemented by automation (Theodorouet al., 1994). This approach has been applied to a variety of foods with different purposes: estimating the effect of maturity on alfalfa and brome hay digestion (Stefanonet al., 1996), evaluating the role of genetic variation on perennial ryegrass rumen fermentation (Looet al., 1994) and comparing rice-straw fermentability (Williamset al., 1996).This research has been designed to rank maize silages according to their fermentability and to evaluate possible correlation to the near infrared reflectance spectroscopy (NIRS) predicted wet chemistry values andin vivocalculated organic matter digestibility (OMD).

In vivo and in situ measurements of forage protein degradation in beef cattle.

In vivo and in situ protein degradation measurements were compared using alfalfa (2.62% N) and prairie hay (.88% N) fed to six cannulated cows in a two-period crossover experiment. Additionally, two in situ procedures were evaluated: in P1 samples were ruminally incubated in cows fed the same forage as incubated; in P2 samples were incubated in the rumens of two steers fed a "standard" brome hay (1.38% N). Duplicate bags were incubated for 0, 2, 6, 10, 16, 24, 48, and 72 h. Protein degradability was estimated using residual N from all incubation times fit to a nonlinear, least squares model (full time-series), from the 16-h incubation alone (single-point) and from a combination of the 0-h and 16-h values (double-point). Protein degradability estimates from in vivo, in situ P1, in situ P2, single-point P1 and P2, and double-point P1 and P2 were 83.4 +/- 4.3, 91.5 +/- .6, 87.2 +/- .6, 94.0 +/- .2, 92.4 +/- .8, 90.4 +/- .4, and 88.3 +/- .5, respectively, for alfalfa, and 55.5 +/- 3.5, 58.3 +/- 1.3, 57.2 +/- .4, 50.0 +/- 1.7, 52.0 +/- 2.2, 55.5 +/- 2.1, and 60.0 +/- 2.3, respectively, for prairie hay. Although relatively large differences in rates of degradation and sizes of protein fractions were measured between P1 and P2, differences between procedures for protein degradability estimates were small relative to errors of in vivo measurement. Furthermore, differences in protein degradation using single-point values as compared with full time-series analysis were overcome with the double-point approach.

Effect of maturity on digestion kinetics of water-soluble and water-insoluble fractions of alfalfa and brome hay.

Alfalfa and bromegrass, each harvested at five different stages of maturity, were separated into water-insoluble and -soluble fractions. The NDF concentrations ranged from 19 to 43% for alfalfa and from 42 to 58% for brome. The rates of digestion, by mixed ruminal microflora, of the unfractionated forage and of the water-insoluble and -soluble fractions were measured in vitro using pressure sensors to monitor gas production. Both forages showed the expected decline in fiber digestibility with increasing maturity. A dual-pool logistic model gave pool sizes, specific rates, and a single lag time for both the faster- and slower-digesting fractions. The main difference between alfalfa and brome was in the soluble pool. This pool produced approximately 40% of the total gas in alfalfa, 25% in brome. The specific digestion rates of the brome soluble pool were approximately 50% higher than those for alfalfa. Net VFA production showed a somewhat higher acetate: propionate ratio for brome (3.2) compared with alfalfa (2.2), but there was little change with increasing maturity within a given forage. Gas production curves for the unfractionated forage showed a 0 to 10% positive deviation from curves created by adding data from separate digestion of the insoluble and soluble forage fractions. Gas measurements offer a promising approach to the study of the water-soluble extracts of forages and the interaction of the soluble- and insoluble-fractions during fermentation.

Influence of crambe meal as a protein source on intake, site of digestion, ruminal fermentation, and microbial efficiency in beef steers fed grass hay.

Four ruminally and duodenally cannulated beef steers (558 +/- 37 kg) were arranged in a 4 x 4 Latin square to evaluate the influence of crambe meal as a protein source on intake, digestion, and microbial efficiency. Steers were offered chopped (10.2 cm) brome hay (6.2% CP) for ad libitum consumption and one of four supplements. Protein sources used were soybean and crambe meals (CM). Protein sources were blended to provide four levels of supplemental CM protein (0, 33, 67, and 100%). Protein supplements were fed to provide similar amounts of protein and energy. Amounts of supplements fed were 831, 885, 950, and 996 g of DM/steer daily for 0, 33, 67, and 100% CM treatments, respectively. Crambe meal represented 0, 2.00, 3.83, and 5.88% of the DM intake for respective treatments. Steers were allowed a 21-d adaptation to diets before each collection period. Supplements were offered at 0800 and forage at 0830. Crambe meal had no influence (P > .10) on forage and total DM intake (grams/kilogram of BW). Apparent total tract, ruminal, and postruminal digestion of OM, NDF, ADF, and N were unaffected (P > .10) by CM supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of volatile fatty acid disappearance and fluid flux across the abomasum of cattle, using an improved omasal cannulation technique

Summary Six steer calves, surgically fitted with a permanent cannula in the rumen, omasoabomasal orifice, abomasum, and duodenum were used to determine total digesta flow and volatile fatty acid (vfa) concentration at various points in the digestive tract. The omasoabomasal cannula had a flexible nylon sleeve that could be exteriorized through the abomasal cannula to collect omasal effluent. Three experiments were conducted: 95% concentrate fed at maintenance (2,670 g of organic matter intake/d); 95% concentrate fed ad libitum (3,484 g of organic matter intake/d); and brome hay fed ad libitum (2,927 g of organic matter intake/d). Calves were offered the diet in 12 portions daily. Each experiment included a 14-day adaptation period and a 2-day sample collection period during which chromic oxide was used as a digesta flow marker. In all 3 experiments, vfa concentration was greatest in the rumen sample (84 to 109 mM), intermediate in the omasal sample (32 to 40 mM), and lowest in the duodenal sample (7 to 14 mM, P &lt; 0.01). Total fluid flow at the duodenum was 13 to 18 L/d greater than flow at the omasum (P &lt; 0.10). Omasal vfa flow was twofold greater than duodenal vfa flow (P &lt; 0.05). There was a net fluid increase and net disappearance of vfa across the abomasum. The cannulation technique was useful for repeated collection of omasal effluent for at least 3 months.

Influence of energy source on forage intake, digestibility, in situ forage degradation, and ruminal fermentation in beef steers fed medium-quality brome hay.

Eight ruminally cannulated steers (average initial weight 196 +/- 13 kg) were arranged in a replicated 4 x 4 Latin square. Steers had ad libitum access to chopped brome hay (Bromus inermus L. 9.9% CP) and one of four supplements. Supplements were fed to provide 195 g of CP.steer-1 x d-1 (equalized with soybean meal), and supplemental energy intake was similar among energy supplements. Supplemental treatments were control (CTRL; primarily soybean meal), barley (BAR), beet pulp (PULP), and corn (CORN). Amounts fed were 481, 1,285, 1,335, and 1,289 g of DM.steer-1 x d-1 for CTRL, BAR, PULP, and CORN, respectively. Individually stanchioned steers were allowed a 13-d adaptation period followed by an 8-d collection period. Chromic oxide was used as the indigestible flow marker. Forage intake was less (P < .10) for steers fed BAR, PULP, and CORN than for CTRL steers, but total intake (forage+supplement) did not differ among treatments. Total tract DM and OM digestibilities were greater (P < .10) for PULP- and CORN- than for CTRL- and BAR-supplemented steers. Digestibility of NDF was least (P < .10) for BAR, intermediate for CORN, and greatest for CTRL and PULP (44.0, 47.2, 50.1, and 52.1%, respectively). Apparent CP digestibility was least (P < .10) in BAR-(60.8), greatest in CTRL- (69.7), and intermediate in PULP- and CTRL- (64.0 and 64.4) supplemented steers. Ruminal DM fill was less (P < .10) in steers fed BAR and PULP than in CTRL steers. No differences (P < .10) were noted in DM and NDF rate of in situ degradation. Rate of forage CP in situ degradation was faster (P < .10) in CTRL- and PULP- than in CORN- and BAR-supplemented steers. Steers fed BAR and PULP supplements exhibited a lower overall pH response curve (P < .005) than did steers fed CTRL and CORN; this finding corresponded to increased (P < .005) response curves in PULP-fed steers for total VFA, acetate, and propionate compared with other treatments. These data indicate that energy supplementation decreased forage intake, altered ruminal fill, shifted VFA patterns, and changed in situ rate of forage CP degradation. Moreover, PULP maintained NDF digestibilities equal to CTRL levels, whereas CORN and BAR did not.

Effect of increasing ruminal butyrate on portal and hepatic nutrient flux in steers.

Six Holstein steers (mean +/- SE BW = 344 +/- 10 kg) fitted with hepatic, portal, and mesenteric vein and mesenteric artery catheters and a ruminal cannula were used in a 6 x 6 Latin square design to evaluate the effects of increasing ruminal butyrate on net portal-drained visceral and hepatic nutrient flux. Steers were fed a 40% brome hay, 60% concentrate diet in 12 portions daily at 1.25 x NEm. Water (control) or butyrate at 50, 100, 150, 200, or 250 mmol/h was supplied continuously via the ruminal cannula. Simultaneous arterial, portal, and hepatic blood samples were taken at hourly intervals from 15 to 20 h of ruminal infusion. Portal and hepatic blood flow was determined by continuous infusion of P-aminohippurate, and net nutrient flux was calculated as the difference between venous and arterial concentrations times blood flow. Ruminal and arterial concentrations and total splanchnic flux of butyrate increased (P less than .01) with increased butyrate infusion. Arterial concentrations of acetate (P less than .10), alpha-amino-N (P less than .05), and glucose (P less than .01) decreased with increased butyrate, whereas arterial beta-hydroxybutyrate (P less than .01) and acetoacetate (P less than .05) increased. Increased butyrate produced an increased portal-drained visceral flux of acetoacetate and an increased net hepatic flux of beta-hydroxybutyrate. Urea N and glucose net portal and hepatic fluxes were not affected by ruminal butyrate. Alpha-amino-N uptake by the liver decreased with increased butyrate (P less than .10). Simple linear regression (r2 = .985) indicated that 25.8% of ruminally infused butyrate appeared in portal blood as butyrate. Only 14% could be accounted for as net portal-drained visceral flux of acetoacetate plus beta-hydroxybutyrate.

Influence of source and level of ruminal-escape lipid in supplements on forage intake, digestibility, digesta flow, and fermentation characteristics in beef cattle

Six ruminally fistulated steers (550 kg) and 24 heifers (315 kg) were used to determine the effect of source and amount of ruminal-escape lipid in a supplement on forage intake and digestion. Steers were used in a 6 x 6 Latin square digestion study to evaluate six supplementation treatments: 1) negative control (NC), no supplement; 2) positive control (PC), soybean meal:grain sorghum supplement; 3) low-Megalac (calcium salts of fatty acids; LM) supplement; 4) high-Megalac (HM) supplement; 5) low-Alifet (crystallized natural animal fat, LA) supplement; and 6) high-Alifet (HA) supplement. Supplements were fed at .30% of BW on a DM basis and were isoenergetic within fat levels (high vs low). Steers were fed mature brome hay (7.2% CP) at 1.5% of BW on a DM basis. In the forage intake trial, heifers were assigned randomly to the same supplement treatments. Prairie hay (4.4% CP) was offered at 130% of ad libitum intake. Dry matter and NDF digestibility, ruminal DM fill, indigestible ADF passage rate, and fluid dilution and flow rates were not different (P greater than .10) among treatments. Total VFA concentrations were greater (P less than .01) and acetate-to-propionate ratio (Ac:Pr) was less (P less than .01) in supplemented groups; however, neither source nor level of escape lipid influenced either total VFA or Ac:Pr. Forage intake was greater (P less than .01) for supplemented groups than for the NC. At the high level of fat inclusion, heifers supplemented with Alifet ate slightly more (P less than .05) forage than those supplemented with Megalac.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of a parasympathomimetic agent, slaframine, on reticulo-omasal orifice function

Three nonlactating, nonpregnant, ruminally cannulated Holstein cows (680–732 kg) fed chopped brome hay ad libitum once daily were used to study effects of slaframine (SF) on rumen function in a 3 × 3 Latin square design. Animals were injected intramuscularly with 0, 20 or 40 μg kg BW−1 SF, allowing for 1 d between trials. At 0, 40, 180 and 360 min postinjection rumen contents were partially evacuated. Reticular contraction frequency (RCF) was determined using a balloon placed in the reticulum connected to a pressure transducer and physiograph and reticulo-omasal orifice opening duration (ROOD) was measured using palpation and endoscopy. RCF as a percentage of predose was decreased linearly by SF treatment (P &lt; 0.01). SF affected ROOD, which was higher (P &lt; 0.05) for both SF treatments. This pattern was also linear (P &lt; 0.01). A characteristic change in reticulum pressure was identified that correlated with SF mediated variation in ROOD (r = 0.67; P &lt; 0.01). Previous research has indicated that SF administration increased salivation and shifted site of digestion. The results presented herein are consistent with these observations and indicate that duration of reticulo-omasal orifice opening may be more highly associated with the rate of digesta passage than reticular frequency. Key words: Slaframine, reticulo-omasal orifice, reticulum motility, cattle