Chopped Alfalfa Hay Research Articles

Influence of Source and Amount of Dietary Protein on Milk Yield by Cows in Early Lactation

The purpose of this research was to examine the effects of various amounts of CP and RUP on AA flow to the small intestine and milk yield of lactating dairy cows. The first trial was a 5×5 Latin square design using five ruminally and duodenally cannulated multiparous cows, Diets contained chopped alfalfa hay, corn silage, high moisture corn, solvent-extracted soybean meal, and specially processed soybean meal (60.2% RUP). Soybean meal replaced high moisture corn to increase dietary CP from 14.5 to 16.5 or 18.5%, and specially processed soybean meal replaced solvent-extracted soybean meal in diets containing 16.5 or 18.5% CP to provide 6.2, 7.3, 6.7, and 8.3% RUP. Increasing dietary CP increased the flows of all AA to the duodenum. Increasing dietary RUP increased flows of Arg, His, Lys, Phe, Asp, and Glu to the duodenum. In a second trial, 36 cows were fed diets similar to those used in trial 1. Increased amounts of RUP in diets tended to increase milk yield because of improved protein status, improved intake of metabolizable energy, or both.

Plasma flow and net nutrient flux across gut and liver of cattle fed twice daily.

The objectives of this study were 1) to quantify daily patterns of plasma flow and metabolite flux through portal-drained viscera (PDV) and liver in cattle fed twice daily and 2) to identify an interval for blood sampling that would approximate the average daily plasma flow and nutrient flux values. Data are from three experiments in which multicatheterized cattle were fed at or near ad libitum intake twice daily. Five lactating primiparous Holstein cows (506 kg, fed at 0730 and 1930) ate 17.3 kg DM/d as chopped alfalfa hay:corn grain plus supplement (urea and minerals) 50:50 (Exp 1). Five beef steers (474 kg, fed at 0900 and 2100) ate 8.3 kg DM/d as chopped switchgrass hay:corn grain plus supplement 37:63 (Exp 2). Six beef steers (306 kg fed at 0900 and 2100) ate 6.9 kg DM/d as chopped alfalfa hay (Exp 3). Plasma flow (by dilution of para-aminohippurate) was measured hourly for 24 h. Plasma flows (mean +/- SE) through PDV were 1,264 +/- 147, 538 +/- 56, and 499 +/- 26 L/h for Exp. 1, 2, and 3, respectively. Corresponding liver flows were 1,662 +/- 216, 642 +/- 41, and 591 +/- 30 L/h. The within-animal differences from their respective daily means were estimated as a function of time of day using nonparametric smoothing. Across experiments, PDV and liver flows were above the daily mean from 1200 to 1400, were not different from the daily mean from 1600 to 1700, and were below the daily mean from 1930 to 2130. Metabolites measured were ammonia, urea, alpha-amino N, and glucose. In general, metabolite flux was not different from the average daily mean values between 1200 and 1600. Blood sampling over 12 h or one 12-h feeding cycle is sufficient for daily plasma flow and metabolite flux estimation in cattle fed twice daily.

Comminution of roughages by red deer (Cervus elaphus) during the prehension of feed

SUMMARYThe chewing behaviour of red deer (Cervus elaphus) during eating and the effectiveness of chewing on feed comminution was studied in two experiments. In Expt 1, deer were fed long or chopped lucerne (Medicago sativa) hay, and feed intake and chewing activity were recorded. In Expt 2, the rumen was emptied and test meals of fresh chicory (Cichorium intybus cv. Puna), lotus (Lotus corniculatus cv. Grasslands Goldie), ryegrass (Lolium perenne cv. Ruanui) forage and long lucerne hay were given, chewing activity recorded and the ingested forage quantitatively removed from the rumen. In Expt 1, the chopped hay was eaten more quickly than long hay (11·4 v. 8·3 g dry matter/min), and required fewer chewing bites per g dry matter eaten. In Expt 2, the four forages were consumed at similar rates (mean 4·3 g organic matter/min) and there was no significant difference in the chewing required to consume either total organic matter (OM) or cell wall OM. Deer chewed more quickly when eating lucerne hay than when eating lotus, and it was estimated that a greater number of chewing bites were required to form a bolus of lucerne hay than to form a lotus bolus. The proportion of ingested OM which was comminuted so as to pass a 1 mm sieve (efficiency of chewing) was greater for lotus (0·485) and lucerne hay (0·.518) than for chicory (0·.267). The efficiency of chewing ryegrass (0·.366) was intermediate and not significantly different from any other forage. For all forages, the main effect of chewing during eating appeared to be the release of cell contents, rather than the comminution of cell wall. Physical breakdown to particles which passed a 1 mm screen but were retained on an 0·25 mm screen was low for fresh forages (0·074–0·086) but was slightly higher for lucerne hay (0·127). Deer reduced feed particle size during eating with a similar efficiency to sheep, but were less efficient than goats.It is suggested that the chewing effort associated with forage consumption by red deer is related to the need to form a bolus. The amount of chewing may be as much influenced by the physical characteristics of the forage (e.g. leaf size and shape) as by its chemical composition, and the extent of comminution during eating may be determined by the processing needed to form a bolus and the resistance of the feed to bolus formation.

Wheat middlings in high concentrate rations: digestibility and ruminal metabolism (1995)

Six medium-framed steers, fitted with ruminal cannulae were used in a 6 x 6 Latin square design and fed the following six high concentrat e (90%) rations: control; 5, 10, or 15% pelleted wheat middlings (WM) replacing the concentrate (dry rolled corn); and 5 or 10% pelleted WM replacing the roughage (chopped alfalfa hay). Dry matter (DM), organic matter (OM), and starch digestibilities decreased linearly when increasing levels of WM replaced the concentrate , but replacing the roughage increased DM and OM digestibilities linearly. WM could replace only up to 5 % of the concentrate without reducing nutrient digestibilities, but complete (10% WM) replacement of the roughage increased nutrient digestibilities.

Wheat middlings in high concentrate finishing rations: cattle performance (1995)

One hundred twenty medium-framed steers were fed one of six high (90%) concentrate rations: control (0), 5, 10, or 15% pelleted wheat middlings (WM) replacing the concentrate (dry rolled corn) and 5 or 10% pelleted WM replacing the roughage (chopped alfalfa hay). Increasing WM replacement of the concentrate increased both dry matter (DM) intake and feed/gain ratio linearly, without influencing daily gain or final weight. WM replacement of the roughage decreased DM intake linearly, but it ha d no effect on daily gain, final weight, or feed efficiency . The data indicate that WM could replace only 5% of the concentrate without reducing cattle performance, but complete (100%) or partial (50%) replacement of the roughage with WM had no adverse effect on cattle performance.

Inclusion of fat in diets for early lactating Holstein cows (1995)

Twenty-four Holstein cows were used to study the effect of dietary fat on milk production and metabolic traits. Whole cottonseed and tallow were used as fat sources and substituted into the control diet on an isocaloric basis. Chopped alfalfa hay and grain sorghum silage constituted the forage in all diets. Treatments were balanced for parity, body weight, and previous lactation milk production or genetic potential (primiparous cows). Cows were housed in a tie-stall barn beginning 4 weeks prepartum, fed similar diets, and assigned to treatment on the day of calving. Diets were formulated to provide 3.3, 4.8 and 6.5% fat. Diets actually measured 2.1, 3.8, and 5.3% fat. Serum urea nitrogen and cholesterol increased with increased dry matter intake and with increasing dietary fat. Serum triglycerides decreased at parturition and were similar among diets through 20 days postpartum. Thereafter, cows fed the 2.1% fat diet had fewer serum triglycerides than cows receiving 3.8% and 5.3% fat diets. Similar differences were observed with regard to mammary uptake of triglycerides. Serum glucose peaked at calving in all cows and tended to be similar among diets. Glucose uptake by the mammary gland increased with milk production. Cows fed the 5.3% fat diet had less urine ketones by 3 weeks postpartum. Weeks to positive energy balance were 8, 7, and 5 for cows fed 2.1, 3.8, and 5.3% fat diets, respectively. Dry matter intake in kg/day and as a percentage of body weight tended to be greater in the high fat group after 3 weeks of lactation. Milk yield (total and 3.5% FCM) was similar among diets through 10 weeks of lactation. Thereafter, lactation curves in cows fed the 5.3% fat diet were more persistent. Similar trends were observed for milk fat and protein. Milk protein percentage was slightly depressed on the 5.3% fat diet, but protein yield increased.; Dairy Day, 1995, Kansas State University, Manhattan, KS, 1995

Flows of Nitrogen and Amino Acids in Dairy Cows Fed Diets Containing Supplemental Feather Meal and Blood Meal

Four Holstein cows, fitted with ruminal and duodenal cannulas, were used to determine the effects of supplemental feather meal and blood meal on ruminal fermentation and flows of N and AA to the duodenum. The basal diet contained (DM basis) 9.9% chopped alfalfa hay, 39.7% corn silage, 34.7% cracked corn, 8.2% corn starch, 2.1% vitamins and minerals, 4.4% casein, and 1% urea. A combination of feather meal and blood meal (3:l on an N basis) was used to replace 0, 33, 67, and 100% of the casein and urea in the basal diet in a Latin square design. Intakes of DM, OM, and N were similar for all diets. Flows of total N, NAN, individual AA, total AA, and total essential AA were unaltered as supplemental feather meal plus blood meal increased. Flows of microbial N tended to decrease, but flow of non-ammonia, nonmicrobial N increased as supplemental feather meal plus blood meal increased. Increased proportions of dietary feather plus blood meal decreased the proportions of Ile Lys, Met, and Thr in duodenal digesta. Molar percentages of ruminal pH and VFA were unchanged, but concentrations of ruminal NH3 N decreased linearly as supplemental feather meal plus blood meal increased. For the diets fed in this study, inclusion of one-third of the supplemental protein from feather plus blood meal resulted in maximum flows of NAN and microbial N to the small intestine.

Nonstructural Carbohydrate and Undegradable Protein Sources in the Diet: Growth Responses of Dairy Heifers1,2

Thirty-five 3-mo-old 150-kg Holstein heifers were fed diets containing two nonstructural carbohydrate sources (corn or barley) with two quantities of undegradable protein (soybean meal or extruded soybean meal) for 9 wk in a 2 × 2 factorial arrangement to evaluate NRC guidelines that the diet contain increased quantities of undegraded intake protein. Total mixed diets fed for ad libitum intake contained approximately 17.4% CP, consisting of 16.7% corn silage (DM basis), 33.3% chopped alfalfa hay, and 50% concentrate mix. Average daily gains were greater for heifers fed extruded soybean meal, but response was greater when heifers were fed barley-extruded soybean meal (1.12, 1.13, 1.05, and 1.23 kg/d for corn-soybean meal, corn-extruded soybean meal, barley-soybean meal, and barley-extruded soybean meal, respectively) than diets of barley-soybean meal. Extruded soybean meal increased DMI (5.9, 6.1, 5.2, and 6.7 kg/d), but DMI were similar when diets based on corn or barley were fed. Diets with greater concentrations of undegraded intake protein fed to dairy heifers resulted in greater DMI and average daily gains, but responses were greater when heifers were fed diets based on barley rather than corn. These results suggest that current NRC recommendations for undegraded intake protein fed to 3- to 6-mo-old dairy heifers are too high; diets containing 35 to 40% undegraded intake protein should be sufficient.

Influence of pH and Rapidly Fermentable Carbohydrate on Mineral Release in and Flow from the Rumen

Objectives for this study were to determine the effect of energy supplementation on mineral release in and outflow from the rumen, independent of pH. Nonlactating Holstein cattle with ruminal cannulas were limit-fed chopped alfalfa hay with or without energy supplement. Treatments were 1) control, alfalfa plus ruminal infusion of 3L/d of distilled water; 2) acid, alfalfa plus infusion of 3L/d of 1N HCl; 3) energy supplement, alfalfa and ground corn plus infusion of 3L/d of distilled water; and 4) buffered energy supplement, alfalfa, and ground corn plus infusion of 3L/d of distilled water containing 90g of NaHCO3. Macromineral intake was standardized across treatments by adjustment of infusion solutions with inorganic mineral sources. Dry matter consumed was 5kg/d on treatments 1 and 2 and 8.4kg/d on treatments 3 and 4. Mean ruminal pH was 6.8, 6.1, 5.6, and 6.2 for treatments 1 through 4, respectively. Ruminal pH was more significant than energy supplementation in dispersion of Ca, Mg, and P in ruminal digesta. Only 1, 17, and 27% of dietary K, Mg, and P flowed with solids from the rumen, but 52% of Ca and 41% of Cu remained with the solid phase.

Relationships among ewe milk production and ewe and lamb forage intake in Targhee ewes nursing single or twin lambs1

Targhee ewes with single or twin lambs were used in four trials during early lactation through weaning to evaluate ewe milk production (MP), kilograms of lamb weaned, and forage intake by ewes and lambs. During Trial 1, ewes with lambs were individually penned, fed .45 kg of barley-ewe-1.d-1 and allowed ad libitum access to chopped alfalfa hay. Trials 2, 3, and 4 were conducted on three different types of Western range environments. Forage intake of ewes in Trials 2, 3, and 4 and of lambs in Trials 3 and 4 was estimated using chromic oxide. Estimates of milk production were obtained by hand-milking. Average lamb age was 4, 50, 78, and 106 d at the beginning of Trials 1, 2, 3, and 4, respectively. Milk production was greater (P = .01) for ewes nursing twins than for those nursing singles at d 4 and 14 in Trial 1. In Trials 2, 3, and 4, all ewes had similar (P > .18) milk production. Ewe DMI during Trials 1 and 2 was greater (P < .05) for ewes nursing twin lambs than for those nursing singles. There was no difference (P > .88) in DMI between ewes with single and those with twin lambs in Trials 3 and 4. Forage DMI by twin lambs, expressed as either kilograms.ewe-1.day-1 or percentage of lamb BW, was higher (P = .01) than intake by single lambs in Trials 3 and 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Soyhulls as a Replacement for Forage Fiber in Diets for Lactating Dairy Cows

Thirty Holstein cows in early and midlactation were fed one of five TMR for 12 wk in which soyhulls replaced 25 or 42% of the forage (alfalfa:corn silages, 1:1, wt/wt, dry basis). Within each amount of soyhull replacement, 33% of the silage was replaced with coarsely chopped alfalfa hay. All diets were isocaloric compared with the control diet, which contained 60% silage and no soyhulls. The high amounts of soyhulls fed with coarsely chopped hay improved DMI, and NDF intake and milk yield by 14, 33, and 9%, respectively, compared with the control diet. Addition of soyhulls at low or high amounts reduced milk fat yield and increased milk protein yield, but addition of hay to the high soyhull diet maintained milk fat yield similar to the control diet. The high soyhull diets increased DM digestibility by 7% compared with the control diet. Rumination time and acetate to propionate ratios were reduced by 43 and 24%, respectively, when high amounts of soyhulls were fed compared with the control diet. Soyhulls can successfully replace 42% of dietary forage when fed in combination with coarsely chopped hay in place of 33% of the dietary silage.

Altered Ruminal Mat Consistency by High Percentages of Soybean Hulls Fed to Lactating Dairy Cows

Three ruminally fistulated dairy cows in early lactation were used in a 3 × 3 Latin square design with 3-wk periods to investigate the effects of alteration of ruminal mat consistency on ruminal function and soybean hull rate of passage. The control diet consisted of 60% forage (alfalfa:corn silages, 1:1, dry basis) and no soybean hulls. Replacement of 40% of the silage mixture with soybean hulls decreased ruminal mat consistency by 57% at 6h postfeeding and reduced rumination activity 52%, ruminal pH 6%, and acetate:propionate ratio observed over 24h by 10% compared with the control diet. Replacement of 75% of the silage with 25% soybean hulls combined with 20% coarsely chopped alfalfa hay increased ruminal mat consistency by 49% at 2 and 6h postfeeding, increased the percentage of large particles (≥9.50mm) retained in the dorsal rumen, and significantly increased ruminal pH 1.5% and acetate:propionate ratio by 17% compared with the diet of 25% soybean hulls without alfalfa hay. Increasing the ruminal mat consistency with coarsely chopped alfalfa hay did not significantly decrease the rate of escape of soybean hulls from the rumen, but addition of alfalfa hay increased 4% FCM 4.8 kg/d compared with FCM of diets containing 25% soybean hulls without alfalfa hay.

Site of mineral absorption in lactating cows fed high-fat diets.

Five lactating Holstein cows with ruminal and duodenal cannulas were used in a 5 x 5 Latin square to determine the site of mineral absorption and effects of sources and amount of dietary fat on apparent absorption. Cows were fed (DM, 17.4 +/- .8 kg/d) chopped alfalfa hay, alfalfa haylage, corn silage, and concentrate at 1:1:1:2 (DM) at 12-h intervals. Calcium salts of palm fatty acid distillate (CS) or animal-vegetable (AV) fat were 0% (control), 2.5% (low, L), or 5.0% (high, H) of the diet DM. After 2 wk of adaptation, duodenal and fecal grab samples were collected at 7-h intervals for 5 d and composited by animal. Calcium intake increased (P < .05) with high-fat diets (195 vs 170 g/d), whereas Mg intake remained unchanged (54.3 +/- 9.0 g/d). Apparent absorption, estimated by Cr2O3, was regressed on Ca or Mg intake (grams/day) and fatty acid (FA) intake (grams/day). Total absorption of Ca (grams/day) = -37.4 + .264 Ca (P = .07, R2 = .14). Ruminal absorption of Mg was independent of FA intake, and magnesium was secreted posterior to the duodenum. Total tract Mg absorption (grams/day) was described by -7.685 + .464 Mg -.0044 FA (P < .0005, R2 = .46). Fat intake decreased (P < .05) total tract Mg absorption, and Ca absorption was decreased by high fat compared with low fat intake (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Roughage level and corn processing infinishing diets: subacute acidosis (1994)

Roughage level and method of corn processing were evaluated for the propensity to cause subacute acidosis in a controlled acidosis challenge model. Four ruminally fistulated steers were adapted to a high grain diet, randomly allocated within a 4 x 4 Latin square, and fed a corn-based finishing ration at 2% of BW/day (dry basis) in two equal feedings. Chopped alfalfa hay was used as the roughage source and added at 8% of the diet dry matter or not added. Corn was fed either whole (WSC) or dry rolled (DRC). Roughage level and grain processing had no effect on postchallenge molar percentage of acetate or total volatile fatty acid production. An interaction (P<.05) was seen in both percent propionate and acetate:propionate ratio. Eliminating roughage in the WSC diet resulted in increased production of propionate and a lower acetate:propionate ratio. Ruminal pH at 3 hours postchallenge and intake during the recovery period were lower (P<.05) for 0 vs 8% roughage. Ruminal pH at 3 and 6 hours postchallenge was lower (P<.05) for DRC than for WSC. Intake during the recovery period did not differ between DRC and WSC. Hours below pH 5.6 were greater (P<.05) for DRC vs WSC and for 0 vs 8% roughage. Though statistically higher (P<.05), no biologically significant levels of lactate were found for either DRC or WSC. This study indicates that adding roughage or feeding WSC vs DRC reduces the propensity for subacute acidosis.

Liver blood flow and metabolic clearance rate of progesterone in sheep

To study the effects of feeding on concentrations of peripheral plasma progesterone, ovariectomised ewes, given exogenous progesterone, were fed 750 g of chopped lucerne hay at either 09.00 (group A, n=5) or at 15.00 (group B, n=5) or were fed ad libitum regularly through the experimental period (group C, n=5). Peripheral blood samples were taken from each ewe at 09.00, 11.00, 15.00, 17.00 and 23.00. In ewes of groups A and B, mean plasma progesterone concentrations declined significantly (P<0·05) after feeding. Mean progesterone concentrations of group C ewes remained low and were significantly different (P<0·05) from the pre-feeding values of group A and B ewes. These results showed that the metabolic clearance rate of progesterone changed with the act of feeding. In a second experiment, portal, hepatic and mesenteric vein cannulae were placed in ovariectomised ewes (n=17). They were then feda ration calculated to maintain liveweight for seven days (M ration). The ewes were then infused with progesterone into a jugular vein and with p-amino hippuric acid into a mesenteric vein. Ewes were then allotted to receive either half M or twice M rations for seven days after which the infusions and blood sampling procedures were repeated. The mean rate of blood flow in the portal vein was directly related to the level of feed offered when ewes received either 1 2 M , M or 2M rations. The liver and gut region removed a mean of 96 per cent of the progesterone entering these tissues. It was concluded that an increased blood flow through the gut and to the liver, coupled with the high efficiency of these tissues to metabolise progesterone, explained the increased metabolic clearance rate of progesterone associated with increased feed intake.

Rumen-protected methionine for lactation, wool and growth in sheep

Two experiments were conducted to investigate the value of rumen-protected methionine (RPmet) for lactating ewes and growing lambs. In Expt. 1, 18 lactating Dorset ewes (60.2 kg) with twin lambs and 12 Dorset ewes (59.4 kg) with single lambs were fed a supplement (1.0 kg/day) containing either 0 or 0.2% RPMet and had ad libitum access to chopped alfalfa hay for 42 d commencing 5 d post parturition. Treatment effects were not significant for either ewe or lamb bodyweight gain, ewe milk production, milk protein, or milk fat ( P > 0.05). In Expt. 2, 26 12-wk-old Dorset ewe lambs (16.9 kg) were used to study the effect of RPMet on bodyweight gain and wool growth. Lambs were fed a corn-soybean meal supplement containing either 0, 0.1 or 0.2% RPMet. Lambs had ad libitum access to chopped grass hay. The supplement was offered to appetite for the first 56 d, and at 0.5 kg/d from d 56 to 112. RPMet did not affect bodyweight gain, feed efficiency, wool yield or staple length ( P < 0.05). Results show that RPMet had no affect on bodyweight change, milk production or wool growth in Dorset ewes and growing lambs under the conditions of these experiments.

Characterization of toxicosis in sheep dosed with blossoms of sacahuiste (Nolina microcarpa)1

To characterize more fully sacahuiste (Nolina microcarpa Watson) toxicosis in sheep and to evaluate benefits of supplemental Zn, sheep were dosed intraruminally with sacahuiste blossoms. In Trial 1, eight fine-wool sheep (47 +/- 2 kg BW) were fed alfalfa hay at 1% of BW daily and dosed intraruminally with inflorescences amounting to 1% of BW daily, in three portions per day, for 10 d. Four sheep were dosed intraruminally with aqueous ZnSO4 (30 mg of Zn/kg BW) daily for 3 d before initial sacahuiste dosing and on alternate days thereafter, and four sheep were untreated with Zn. Toxicosis was evident within 24 h after initial sacahuiste dosage, involving inappetence, depression, hypokalemia, hypophosphatemia, hyperbilirubinemia, and elevated serum enzymes (alkaline phosphatase, creatine kinase, lactate dehydrogenase, aspartate aminotransferase, and gamma-glutamyl transpeptidase). One sheep (untreated with Zn) died on d 3. Aqueous ZnSO4 alleviated inappetence and suppressed elevation of serum urea N and creatinine but did not suppress other changes in serum clinical profiles. In Trial 2, sacahuiste inflorescences were ruminally dosed into 12 fine-wool wethers (29 +/- 2 kg BW) in amounts equalling 0, .25, .50, .75% of BW per day, and chopped alfalfa hay was provided at 1.75% of BW per day for 14 d. Sacahuiste inflorescenses dosed at .75% of BW elicited severe toxicosis within 24 h, and dosage at .50 or .25% of BW per day increased (P = .12) serum bilirubin. Ruminal fluid pH, mean particle retention time, and particulate passage rate were not affected (P > .10) by sacahuiste, but ruminal fluid passage rate increased 1.6-fold (P < .10) and ruminal fluid volume decreased by 60% (P < .10) in sheep given inflorescenses amounting to .50% of BW daily. Sacahuiste inflorescenses dosed intraruminally at .75% of BW per day elicited ruminal impaction with severe hepatotoxicosis, and dosages amounting to .50% or .25% of BW per day caused similar trends.

Effects of intraruminal infusions of urea, sucrose or urea plus sucrose on plasma urea and glucose kinetics in sheep fed chopped lucerne hay

SUMMARYThe effect of rumen fermentation on the relationship between urea and glucose kinetics was examined in sheep fed chopped lucerne hay with intraruminal infusions of water, urea, sucrose, or urea plus sucrose at Palmerston North, New Zealand in 1986. Sheep were fed hourly and infused intraruminally with water (1200 m1/day), or a similar volume containing either urea alone (13·7g/day), sucrose alone (178·2 g/day) or urea (14·6 g/day) plus sucrose (175·0 g/day). The added sucrose resulted in a lower rumen ammonia concentration (P&lt; 0·05), lower plasma urea concentration (P&lt; 0·05) and reduced urinary urea excretion (P&lt; 0·05). Urea recycled to the gut tended to increase with the sucrose, urea or sucrose plus urea treatments compared with the water treatment. The fermentation of sucrose in the rumen resulted in decreases in ruminal pH (P&lt; 0·05) and in the ratio of acetate to propionate (A:P) (P&lt; 0·05). The infusion of sucrose also increased the concentration of propionate in rumen fluid (P&lt; 0·05), tended to increase the plasma glucose level and increased plasma glucose irreversible loss (P&lt; 0·05). The infusion of urea resulted in an increase in the plasma urea level (P&lt; 0·05), urea pool size (P&lt; 0·05) and urea irreversible loss (P&lt; 0·01). However, urea infusion did not affect glucose metabolism or volatile fatty acid (VFA) fermentation. The effects of sucrose infusion on glucose and urea kinetics were broadly similar when given alone or with urea, apart from changes in the urea degradation rate. It was concluded that the additional fermentative activity resulting from sucrose increased propionate production which, in turn, was available for glucose production, thus ‘sparing’ amino acids for tissue protein utilization and reducing urea excretion.

Protein, acetate and propionate for roughage-fed lambs. 1. Body and blood composition

AbstractSixty castrated male lambs fca. 37 kg) were allocated to an initial slaughter group (no. = 12) or to one of six treatment groups (no. = 8). Chopped oaten hay (sprayed with 10 g urea per kg) was offered ad libitum with 57 gjday chopped lucerne hay. Additional supplements were 0 or 57 g/day formaldehyde-treated casein (protected casein) and volatile fatty acids (VFAs) at ca. 1·45 MJ gross energy per day. The VFAs given were acetate or propionate or a mixture of these (molar ratio 4: 1). Daily food intake and weekly live-weight (LW) gain were measured and rumen fluid and blood were collected. The lambs were shorn, slaughtered and body composition was determined.Food intake (g/kg LW) was not affected by treatments. Supplementation with protected casein increased LW gain and wool growth. Supplementation with propionate reduced LW gain, but not when given with protected casein. Plasma concentrations of urea-nitrogen and insulin were increased, and plasma somatotropin decreased in lambs given protected casein. Final body content of water, fat, protein and gross energy, adjusted to the mean fleece/digesta-free body weight of 36·5 kg, was not affected by the treatments. The partitioning of water, fat and energy between the carcass and the rest of the body was affected by the treatments. Excretion of VFAs in urine was measured in two sheep in experiment 2, and was negligible compared with the quantity of VFAs given. It is concluded that energy from salts of VFAs, in particular propionate, is used inefficiently for body-weight gain in lambs given low-protein roughage diets. The nutritional treatments had only marginal effects on the composition of body gain.

Influence of addition of monensin to an alfalfa hay diet on net portal and hepatic nutrient flux in steers.

Six Holstein steers (381 +/- 11 kg BW; mean +/- SE) surgically fitted with hepatic portal (n = 6), hepatic venous (n = 4), mesenteric venous, and arterial catheters were used in a replicated crossover design experiment to evaluate the influence of monensin addition to an alfalfa hay diet on net portal and hepatic nutrient flux. Steers were fed 6.5 kg of DM/d in 12 portions using automatic feeders. Diets included chopped alfalfa hay (20.4% CP) plus 418 g of DM/d of finely ground corn (8.5% CP) with monensin added (240 mg/d) for treated steers. Experimental periods lasted 21 d, with blood samples taken on the final 2 d of each period. Five sets of arterial, portal, and hepatic blood samples were collected hourly from 0900 to 1300 each day. Ruminal fluid samples were collected by stomach tube at the end of each sampling day for VFA analysis. Blood flow was determined by a primed-continuous infusion of p-aminohippurate into the mesenteric venous catheter. Addition of monensin increased (P = .04) the molar percentage of ruminal propionate and decreased ruminal isobutyrate (P = .02) and isovalerate (P = .03). Percentages of the other ruminal VFA, total ruminal VFA concentration, and pH were not affected by feeding monensin. The arterial concentrations of L-lactate (P = .02) and beta-hydroxybutyrate (P = .01) were greater with monensin; however, none of the arterial concentrations of the other metabolites was changed. Feeding of monensin also did not affect (P > .10) portal, hepatic, or hepatic arterial blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)