Intestinal disappearance and mesenteric and portal appearance of amino acids in dairy cows fed ruminally protected methionine

An experiment was conducted to compare the rates of disappearance of amino acids (AA) from the small intestine and their net appearance in the blood draining only the small intestine (mesenteric-drained viscera) and the whole gastrointestinal tract (portal-drained viscera) of cows fed a silage-based diet supplemented or not with ruminally protected Met. Five lactating dairy cows (118+/-4 DIM) equipped with duodenal and ileal cannulae (n = 2) or a duodenal cannula only (n = 3), two of which were multicatheterized, were fed a TMR top dressed with 0 or 72 g of ruminally protected Met per day. The addition of ruminally protected Met to the diet increased the duodenal flux of Met leading to a higher apparent digestibility of Met in the small intestine. Sixty-six percent of Met from ruminally protected Met bypassed the rumen and 82% of that Met disappeared from the small intestine. Arterial plasma Met concentrations numerically increased with ruminally protected Met (45 vs. 18 microM), while total AA concentration decreased. Feeding ruminally protected Met resulted in higher concentrations of urea-N and glucose in arterial plasma. Milk production and milk composition were unaffected. The disappearance of essential AA across the small intestine was equivalent (101%) to their flux through the mesenteric-drained viscera while the portal:mesenteric-drained viscera flux ratio for each essential AA varied from 38% for Thr to 76% for Phe. The portal:mesenteric-drained viscera flux ratio for Met was 66%. These results confirm observations made with pigs and sheep.     

Technical note: assessment of recovery site of mobile nylon bags for measuring ileal digestibility of starch in dairy cows

The objective of this study was to evaluate recovery site of mobile nylon bags for measuring ileal digestibility of ruminally undegraded starch in dairy cows. Eight feed samples of untreated and treated concentrates were examined. Three lactating cows equipped with rumen fistula and duodenal and ileal cannulas were used in the experiment. The mobile nylon bags containing intact feeds or residues after a 12-h ruminal incubation were pretreated using a 2-step procedure to simulate abomasal digestion before insertion through the duodenal cannula. To assess the effect of hindgut fermentation on starch digestibility, approximately half of the bags were collected from the ileum and half from the feces. The results indicate that feed samples should be preincubated in rumen before insertion into duodenum, and that samples with relatively high fractions of rumen-undigestible starch should be collected from the ileum instead of from feces.     

Mobile nylon bag for estimating intestinal availability of rumen undegradable protein

The objective was to develop a method for estimating intestinal availability of rumen undegradable protein. One-gram samples of six feedstuffs were placed into small (3.5 X 5.5 cm) nylon bags (pore size 48 micron). Bags were heat sealed and ruminally incubated in a polyester mesh (lingerie) bag in quadruplicate for each of six time periods (0, 2, 4, 8, 12, 24 h). Two bags from each rumen incubation time were inserted into the small intestine via a duodenal cannula at the rate of one bag per 45 min. Bags were mechanically washed either upon removal from the rumen--for determination of rumen degradability, or when recovered from the feces--for estimation of intestinal availability. Dried bags plus contents were digested intact for nitrogen analysis. Rumen degradable protein and apparent intestinal availability of undegradable protein (based on 8 h of rumen incubation) for corn gluten meal, fish meal, meat and bone meal, soybean meal, canola meal, and alfalfa hay, respectively, were 11.8, 95.0; 28.5, 82.8; 46.7, 73.0; 55.1, 99.3; 69.7, 79.2; and 68.8, 71.2. Results support the use of this technique as a rapid method for estimating both ruminal degradability, and intestinal availability of rumen undegradable protein.     

Ruminal degradability, intestinal disappearance, and plasma methionine response of rumen-protected methionine in dairy cows.

Bioavailability of Met from a rumen-protected Met product was evaluated in two experiments using three ruminally and duodenally cannulated lactating (experiment 1) and nonlactating (experiment 2) dairy cows. In the first experiment, the ruminal in situ and mobile bag technique was used to assess ruminal degradability and intestinal disappearance of Met from the protected Met product. Effective ruminal degradability of Met at a ruminal outflow rate of 0.11/h was 21.7%. Combining effective ruminal degradability with intestinal digestibility yielded an estimate of Met availability of 25%. In the second experiment, designed as a 3 x 3 Latin square, Met availability was assessed by determining the response of plasma Met to supplementation of the protected Met product relative to that of duodenally administered Met. The periods were 1 wk with cows fed a meal containing 0, 20, or 63 g of protected Met on d 1 and infused intraduodenally with 10.7 g of Met on d 4. Blood was collected at various times relative to the time of oral dosing and the commencement of the duodenal infusion. Plasma Met response measured as area under the curve increased linearly with increasing protected Met. The response of plasma Met increased by 33 and 65.5% of the control values for 20 and 63 g of protected Met, respectively. Intestinal bioavailability of Met in the protected Met product ranged from 22 to 34%.     

Ruminal degradability and intestinal digestibility of protein and amino acids in treated soybean meal products

Four lactating dairy cows equipped with ruminal and duodenal cannulas were used to determine the impact of different methods of treating soybean meal (SBM) on the ruminal degradability and intestinal digestibility of crude protein and AA. Solvent-extracted SBM (SE), expeller SBM (EP), lignosulfonate SBM (LS), and heat and soyhulls SBM (HS) were incubated in the rumen in nylon bags for 48, 24, 16, 8, 4, 2, and 0 h according to National Research Council (2001) guidelines. Additional samples of each SBM product were also incubated for 16 h in the rumen; the residues from these bags were transferred to mobile bags, soaked in pepsin HCl, and then used for determination of intestinal digestibility in situ or in vitro. Treatment of SBM (EP, LS, HS) protected the crude protein and AA from ruminal degradation, increasing rumen undegradable protein from 42% in SE to 68% in EP. Kinetic analysis of crude protein and AA degradation in the rumen revealed that, compared with LS and HS, EP exhibited slower rates of degradation but a shorter lag phase and a higher proportion of soluble protein. For all SBM products, the pattern of ruminal degradation, at 16 h of incubation, was characterized by extensive degradation of Lys and His, whereas Met and the branched-chain AA were degraded to the least extent. Estimates of intestinal digestibility of AA and crude protein were lower when measured in vitro than in situ; the magnitude of the difference between the 2 methods was greater (25%) with treated SBM products than with SE (10%). The availability of essential and nonessential AA was consistently greater (30%) with treated SBM than with SE. Among the treated SBM products, 4 essential AA (Ile, Leu, Phe, and Val) showed differences in availability, with values consistently lower for HS than for LS. This study showed that, based on in situ measures, heat and chemical treatment of SBM enhanced AA availability, and that compared with HS, EP and LS had a higher potential to enhance the AA supply to the small intestine of high-producing dairy cows.     

Prediction of duodenal nitrogen supply from degradation or organic and nitrogenous matter in situ

The contribution of different feedstuffs to nitrogen reaching the duodenum was evaluated in situ. Dacron bags containing barley grain, corn grain, wheat silage, corn silage, alfalfa hay, rye grass, whole cottonseeds, or soybean meal were suspended in the rumens of three dairy cows fed roughage and concentrate diets. The effective degradability of the nitrogenous and organic matter of feedstuffs was calculated from their residues after incubation in the rumen for 3, 6, 9, 12, 24, 36, or 48 h. The duodenal nitrogen content at ruminal outflows of 2, 5, or 8%/h was calculated as the sum of undegradable dietary nitrogen and potential microbial nitrogen (assuming 32 g N/kg ruminally degradable organic matter). Comparison of the in situ estimates with previously reported in vivo measurements of duodenal nitrogen in cattle fed diets with similar ingredients to the tested feedstuffs yielded a linear relationship (r2 = .887). The dacron bag technique appears to hold promise for the prediction of nitrogen flow to the duodenum.     

Influence of Jet-Sploding and extrusion on ruminal and intestinal disappearance of canola and soybeans

In situ rumen degradation and intestinal digestibility of DM and CP of Jet-Sploded and extruded protein sources were estimated, using two ruminally and duodenally cannulated lactating Holstein cows, in two experiments. One-gram samples of ground (1 mm) whole canola seed, canola meal, extruded canola meal, Jet-Sploded whole canola seed, Protec, soybean meal and extruded soybean meal (Experiment 1), and whole canola seed Jet-Sploded at temperatures ranging from 116 to 177 degrees C (Experiment 2) were heat sealed into small nylon bags for incubation in the rumen and insertion into the duodenum. Extrusion had no effect on DM or CP disappearance in the rumen nor on effective degradability. Jet-Sploding of whole canola seed dramatically reduced effective degradability (%) of DM (80.5 vs 35.9 at .08 h-1 rumen outflow rate) and CP (83.5 vs. 43.2 at .08 h-1). Total tract disappearance of DM and CP exceeded 90% for all protein sources, except Protec and Jet-Sploded material. Jet-Sploding appears to have potential for decreasing ruminal degradation of canola protein or DM without markedly decreasing intestinal digestibility.     

Fate of supplementary B-vitamins in the gastrointestinal tract of dairy cows

Four lactating Holstein cows equipped with ruminal, duodenal, and ileal cannulas were used in 2 studies to evaluate the disappearance of supplementary B-vitamins before and from the small intestine. The cows were fed a total mixed ration with chromic oxide in 12 daily meals. Each study consisted of a control (no vitamin supplementation) and a treatment period (with vitamin supplementation). Amounts of vitamins (mg/d) supplemented in studies 1 and 2, respectively, were: thiamin: 300 and 10; riboflavin: 1600 and 2.0; niacin: 12,000 and 600; vitamin B₆: 800 and 34; biotin: 20 and 0.02; folic acid: 2600 and 111; vitamin B₁₂: 500 and 0.4. In study 1, vitamins were added to the feed 5 d before and during the 4-d collection period. In study 2, vitamins were infused postruminally 1 d before and during the 4-d collection period. Substantial disappearance before the duodenal cannula was noted in study 1 (67.8% thiamin, 99.3% riboflavin, 98.5% nicotinamide, 41.0% pyridoxine, 45.2% biotin, 97.0% folic acid, and 62.9% vitamin B₁₂). Except for nicotinamide and folate, there was almost no disappearance of postruminally infused vitamins before the duodenal cannula (study 2), suggesting extensive ruminal destruction or use. Apparent intestinal absorption values differed greatly among vitamins, but the proportion of vitamins disappearing from the small intestine was not negatively influenced by supplementation. Except for riboflavin and niacin, absolute amounts disappearing from the small intestine were greater during the treatment than the control periods, suggesting that B-vitamin supply in dairy cows is increased by supplementation, although losses in the rumen are extensive.     

Apparent ruminal synthesis and intestinal disappearance of vitamin B12 and its analogs in dairy cows

The aim of the project was to calculate the apparent synthesis or destruction of cobalamin (vitamin B₁₂) and its analogs in the rumen as well as their apparent intestinal disappearance in dairy cows. Four lactating cows were fed a diet supplemented with cobalt alone (0.76 mg/kg of DM; control) or with cobalt and vitamin B₁₂ (cyanocobalamin, 500 mg/d; treated). In addition to cobalamin, the only biologically active molecule for the cow, 7 analogs were identified in duodenal and ileal digesta: cobinamide, which lacks the base, ribose, and phosphate groups; and 6 other molecules in which the base, 5,6-dimethylbenzimidazole, is replaced by cresol, 2-CH₃-adenine, adenine, 2-CH₃-S-adenine, or 5-OH-benzimidazole, or an unidentified cobamine. Small amounts of cobalamin and cobinamide were detected in the total mixed ration, but apparent synthesis of all forms took place in rumen. During the control period, cobalamin represented 38% of the total amounts of corrinoids produced in rumen. Approximately 11% of the average daily intake of cobalt was used for apparent ruminal synthesis of corrinoids, of which only 4% was incorporated into cobalamin. Only 20% of the supplement of cyanocobalamin was recovered at the duodenal level; cobinamide appeared to be the major product of degradation of supplementary cyanocobalamin in the rumen. During the control and treatment periods, there was an apparent intestinal disappearance of cobalamin and 5-OH-benzimidazole cobamide only; only the apparent intestinal disappearance of cobalamin differed between the 2 periods. Although cobalamin was not the major form synthesized by ruminal microflora and, even if supplementary cyanocobalamin was extensively destroyed by ruminal microflora, based on calculations of apparent intestinal disappearance, cobalamin seems to be the major form absorbed in the small intestine.     

Effect of micronizing full fat canola seed on amino acid disappearance in the gastrointestinal tract of dairy cows

Ruminal and total tract digestion of the amino acids (AA) in full fat canola seed was studied in two in situ experiments with three nonlactating, ruminally and duodenally fistulated dairy cows. Whole, full fat canola seed was hand-cracked or micronized (an infrared heat treatment) for 90 s and then studied in that form or after grinding to pass a 1.25-mm sieve. In the first experiment, the four sample types were ruminally incubated in nylon bags for up to 96 h. In the second experiment, they were sealed in mobile nylon bags, incubated ruminally for 16 h, placed in acidified pepsin for 1 h, and then inserted into duodenal cannulas for passage through the intestine. Amino acids in the canola seed and in the residues from in situ incubations were analyzed by HPLC. Micronization reduced ruminal disappearance of total AA and essential AA from full fat canola seed. Degradation kinetics from Experiment 1 indicated reduced soluble fraction and increased slowly degradable fraction of both total AA and essential AA following micronization. Micronization reduced disappearances of total AA and essential AA from whole canola seed in the total digestive tract but did not affect total tract digestion of total AA or essential AA in ground seed. Intestinal disappearance of total AA and essential AA from both whole and ground full fat canola seed were increased by micronization. Micronizing canola seed may be of value in improving AA utilization in ruminants.     

Effects of Amount and Availability of Starch on Amylolytic Activity of Ruminal Solid-Associated Microorganisms

Three ruminally cannulated dry cows were used in an experiment designed as a Latin square to investigate the effects of amount and availability of starch on the amylolytic activity of ruminal solid-associated microorganisms (SAM). Animals were fed twice daily a diet (7 kg DM day^-1) consisting of wheat straw, cocksfoot hay and ground barley in the ratios 10: 90: 0, 10: 60: 30 and 10: 30: 60. Nylon bags containing rapidly (barley) or slowly (maize) degradable cereal grains were incubated in the rumen. Enzymes of the SAM were extracted from rumen contents and bag residues, and amylolytic (amylase and α-D -glucosidase) activities were measured. The in situ degradation of starch was determined. Increasing the level of barley in the diet induced a linear increase in amylase activity of SAM in the rumen contents. In the bags, amylase activity and starch degradation rate were not modified by supplementation. High activity was observed more rapidly in bags containing barley, where starch is rapidly available, than in bags containing maize, where starch is protected by a resistant endosperm. These results suggest that amylolytic activity of SAM may depend on the amount of starch available to microorganisms. © 1997 SCI.     

In situ disappearance of malate from alfalfa and bermudagrass hay

The objectives of this study were to determine the rate of malate and dry matter disappearance from different forages in the rumen. Four nonlactating, ruminally cannulated Holstein cows were fed a hay-based diet. Samples of early and late harvested alfalfa, Coastal bermudagrass, and Tifton 85 bermudagrass hays were ground, placed in nylon in situ bags, and ruminally incubated for 0, 0.5, 1, 2, 4, 8, 12, 24, and 48 h. After incubation, samples were rinsed, freeze-dried, extracted, and analyzed for malate content by HPLC with an organic acid column. When forages were incubated in the rumen, malate concentrations were less than 0.55 mg/g of dry matter at 0.5 h and remained low for the 48-h incubation period. These results suggest that malate was solublized and utilized within 30 min after reaching the rumen. Dry matter digestibility of both forages increased with time and was different across forages. Both alfalfa samples were digested to a greater extent between 0.5 and 24 h than either type of bermudagrass, but after 48 h the early maturity Tifton 85 digestibility was similar to alfalfa. Even though it is more common to feed unground forages to ruminants, these in situ results suggest that once malate is available in the rumen it will disappear quickly.     

A comparison of purine derivatives excretion with conventional methods as indices of microbial yield in dairy cows

Three multiparous, ruminally and duodenally cannulated Holstein-Friesian milking cows (558 +/- 14 kg BW) with a mean milk yield of 19.9 +/- 1.4 kg/d in their 4th mo of lactation were fed a mixed diet of forage and concentrate at 100, 85, and 75% of ad libitum intake in a 3 x 3 Latin square design. Duodenal digesta flow was estimated using the dual-phase technique in which Cr-EDTA and Yb-acetate were used as liquid and solid markers, respectively. Microbial N (MN) was estimated using the duodenal flow of purine bases (PB); bacterial isolates from the rumen liquid and solid phases were used as references. Additionally, duodenal flow of PB and MN were estimated indirectly using the excretion of purine derivatives (PD) in urine and milk. Duodenal flow of PB and derived MN tended to decrease with feed restriction (from 258 to 154 mmol/d and 123.5 to 74.4 g/d, respectively). Estimates of PB and MN based on urinary PD showed the same trend, and decreases in PB (from 314 to 266 mmol/d, using LAB) were statistically significant. Using LAB, efficiencies of microbial protein synthesis in the ad libitum treatment were 12.9 and 17.0 g of MN/g of organic matter apparently digested in the rumen when estimated using duodenal PB and urinary excretion of PD, respectively. Urinary excretion of PD closely reflected changes in duodenal flow of PB as a result of feed restriction.     

Determination of rumen degradability and ruminal effects of three sources of methionine in lactating cows

Objectives were to quantify the ruminal effects and flows to the omasum of Met provided as 2-hydroxy-4-(methylthio)-butanoic acid (HMB), the isopropyl ester of HMB (HMBi), and DL-Met. Eight ruminally cannulated cows were used in a replicated 4 x 4 Latin square design. Treatments were 1) no Met (control), 2) HMB at 0.10% of DM, 3) HMBi at 0.13% of DM, and 4) DL-Met at 0.088% of DM. Diets were identical except for type of Met supplement and were based on corn silage and alfalfa hay at 30 and 13% of dietary DM, respectively. Samples of omasal fluid were used to determine the proportion of Met supplements passing out of the reticulorumen. Dry matter intake (20.1 kg/d) was restricted during the week of sampling to a maximum of 95% of ad libitum DMI determined during the first 2 wk of the period. Milk yields (37.7 +/- 0.8 kg/d) and fat concentration (3.42 +/- 0.15%) were not significantly different for control, HMB, HMBi, and DL-Met. Milk protein concentration (2.91, 2.95, 3.02, 2.96 +/- 0.07%, respectively) was significantly increased by the HMBi treatment. Rumen volatile fatty acids profile and NH3 concentrations were similar across treatments. Apparent ruminal digestibility of organic matter and neutral detergent fiber were higher for the three diets supplemented with Met sources than for the control diet. In situ rate of digestibility of CP from alfalfa hay, TMR, and corn silage was affected by Met sources. Passage rates of small particles (0.071/h) and fluid (0.167/h) were not affected by treatments. Protozoal counts in the rumen and omasum were not significantly affected by Met sources. Proportion of omasal N from bacterial N was not different (0.54 +/- 0.03), and bacterial N flow (305 +/- 24.4 g/d) was similar across treatments. The proportion of HMB that passed into the omasum was 5.3 +/- 1.5% of the amount consumed. Only a small amount (2.3%) of HMBi was found as HMB in the omasum. These results indicate that little HMB escapes ruminal degradation through passage to the omasum and that the site of HMBi absorption must be preomasal.     

Starch and stage of maturity of grass silage: site of digestion and intestinal nutrient supply in dairy cows

The interaction between the quality of grass silage and starch supplementation on ruminal digestion was studied in an experiment with a 2 x 2 factorial design using four dairy cows. Treatment factors were grass silage harvested after either 21 or 37 d of regrowth and two concentrations of steam-flaked corn starch (0 or 4 kg/d). Ruminal volume and flow of duodenal digesta were estimated. When forage was harvested at a more mature stage, only minor effects were noted for silage composition and, consequently, ruminal and intestinal digestion. The addition of starch to the diet tended to reduce ruminal digestion of neutral detergent fiber. The reduction in ruminal digestion was not compensated by increased digestion in the large intestine. Starch increased duodenal nonammonia N flow because of an increase in bacterial N flow. The increase in bacterial N was accompanied by a reduction in the escape of feed N from the rumen. Results from this study indicate that the addition of ruminally available starch to diets based on grass silage reduced ruminally degradable neutral detergent fiber and increased the duodenal supply of protein. These effects have to be taken into account to predict production responses to extra starch.     

Ruminal escape, gastrointestinal absorption, and response of serum methionine to supplementation of liquid methionine hydroxy analog in dairy cows

Availability of liquid methionine hydroxy analog [D,L-2-hydroxy-4-(methylthio)-butanoic acid] was evaluated in two experiments using four cannulated lactating dairy cows. The first experiment was designed as a 4 x 4 Latin square. Each cow received a pulse dose of 0, 30, 60, or 90 g of the methionine analog in the rumen each day for 10 d. Duodenal samples were collected at 16, 20, and 24 h after dosing for the last 5 d and pooled. The methionine analog was not detected in duodenal contents because it passed rapidly from the rumen relative to the sampling protocol. In the second experiment, cows were offered 90 g of the methionine analog and 600 ml of Cr-EDTA (3.5 g of Cr) mixed with ground corn for a period of 20 min after which any remains of the treatment were placed in the rumen. The concentration of the analog peaked in ruminal and duodenal fluid at 1 and 3 h, respectively. Based on the fractional rate constants for ruminal and duodenal disappearance of the methionine analog and passage of the liquid, it was determined that 50.0 +/- 2.8% of the methionine analog escaped ruminal degradation and became available for intestinal absorption (44.6 +/- 5.7%) or was absorbed from the omasum (5.4 +/- 3.3%). Serum methionine concentration peaked 6 h after analog dosing at a level that was three times the predose level, indicating that the methionine analog that escaped ruminal degradation was absorbed and metabolized to methionine.     

Ruminal supplementation of direct-fed microbials on diurnal pH variation and in situ digestion in dairy cattle

To evaluate the effect of direct-fed microbial (DFM) concentration on diurnal rumen pH profiles and in situ digestibilities, nine ruminally cannulated cows in early lactation were fed treatments consisting of DFM (Enterococcus faecium, Lactobacillus plantarum, and Saccharomyces cerevisiae) at a level of a) 1 x 10(5) cfu/ml of rumen fluid (10(5)), b) 1 x 10(6) cfu/ml of rumen fluid (10(6)), and c) 1 x 10(7) cfu/ml rumen fluid (10(7)). Treatments were directly administered via rumen cannula once daily. Cows were fitted with pH probes in their cannula and connected to dataloggers, which monitor pH hourly. The experimental period was 21 d: 7-d adjustment, 14-d for pH, and in situ measurements. Cows fed 10(5) were able to sustain a higher nadir pH than were cows fed 10(6) or 10(7). Cows fed 10(5) had a higher digestion rate of high moisture ear corn (HMEC) dry matter. Corn silage digestion was higher for cows fed 10(5) and 10(6) compared with those receiving 10(7). There were no carryover effects of treatment associated with rumen pH when switching from one treatment regimen to the next. Results from this study demonstrate that incorporation of a specific level of DFM aids in reducing diurnal ruminal acidity.     

Estimation of the digestible energy of ruminant feedstuffs by the combined bag technique

The combined bag technique was used to estimate digestible energy of ruminant feedstuffs. Samples of corn, barley, and sorghum grains; soybean and sunflower meals; corn and wheat silages; and vetch and wheat hays were incubated in dacron bags in the rumens of dairy cattle for 3 to 72 h. Bags containing residues after 12 h of ruminal incubation were introduced into the duodenum and recovered from feces. Feeds and ruminal and intestinal residues were analyzed for dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber, and nonstructural carbohydrates. The effective ruminal degradability of OM was higher in grains (639 g/kg of DM) and in protein supplements (609 g/kg of DM) than in forages (373 g/kg of DM). For grains and forages, carbohydrates contributed most of the degradable OM in the rumen, but, in protein supplements, about 50% of the ruminally degradable OM originated from carbohydrate. For protein supplements, 54% of the OM that disappeared postruminally was CP, but, in the grains and forage ingredients, CP contributed less than 20% of the postruminal OM that disappeared. In grains and forages, 83% of total tract disappearance of OM was from carbohydrates. For protein supplements, CP contributed 50% to overall OM disappearance. The calculated energy equivalent of digested matter averaged among feeds was 4.71 kcal/g. A high correlation was found between digestible energy estimated by the combined bag technique and the respective National Research Council values. The combined bag technique is a useful tool for the estimation of digestible energy in feedstuffs.     

Technical note: A method to facilitate retrieval of polyester bags used in in sacco trials in ruminants

A method is described to facilitate the retrieval of polyester bags from ruminally cannulated cattle. The system consists of 2 major components, i) an accommodation vessel for multiple polyester bags in the form of an opaque nylon stocking, referred to as the “receptacle,” and ii) a shorter stocking, knotted with a loop on one end to attach to the receptacle, referred to as the “catcher.” The catcher is tied on the other end to the inside of the cannula plug. Sample bags are inserted in tandem into the receptacle, separated from each other by a tight knot. The receptacle is tied to the catcher and subsequently inserted into the rumen. Upon retrieval, receptacles are pulled out only far enough to expose the first bag to be removed. This procedure ensures easy bag retrieval without exposing the remaining bags (intended for further incubation) to air.     

Effect of sometribove on rumen fermentation, rate of passage, digestibility, and milk production responses in dairy cows.

Six ruminally and duodenally fistulated Holstein cows 60 d postpartum were assigned randomly to each of two treatments in a single reversal design. Treatments consisted of placebo or 25 mg of sometribove (bST) injected daily. Treatments were initiated at 60 d +/- 7 postpartum and maintained for 6 wk with a 3-wk adjustment between treatment periods. All cows received a TMR consisting of 16% CP and 1.67 Mcal of NE I/kg of DM. Influence of bST on rumen fermentation characteristics, digesta rate of passage, apparent nutrient digestibility, and milk production was evaluated. Milk yield of treated animals was 4.0 kg/d higher than controls. The 3.5% FCM and milk production efficiency (3.5% FCM/DMI) were significantly higher in treated animals than in controls (29.0 vs. 25.4 kg/d and 1.38 vs. 1.21 kg/kg, respectively). Percentage of rumen cellulolytic bacteria (of total viable bacteria) was not significantly different for bST-treated animals (6.4 vs. 3.4%). Total number of rumen protozoa tended to be higher (7.25 vs. 6.55 x 10(3)/ml) in bST-treated animals. Ruminal percentages of CP, NH3 N, alpha-amino N, VFA, and pH were unaffected by treatment. Sometribove treatment did not significantly affect liquid dilution or solids turnover rates. Percentages of CP, alpha-amino N, and NH3 N content in duodenal samples were unaffected by treatment. Total tract apparent digestibility of nutrients and mean daily DMI were unaffected by treatment.