Effects of animal-to-animal exchange of ruminal contents on the feed intake and ruminal characteristics of fed and fasted lambs

Four Suffolk x Hampshire wether lambs averaging 55 kg with permanent ruminal cannulas were used in a 4 x 4 Latin square design to determine the effects of exchange of ruminal contents between fed and fasted lambs on subsequent DMI and ruminal characteristics. Lambs were fed a pelleted 70% roughage diet at 2% of BW for 17 d. During each period of the Latin square two lambs were deprived of feed and water for 3 d. At the end of the fasting period ruminal contents from one fed and one fasted lamb were exchanged. Lambs were then given ad libitum access to feed for 8 d, during which DMI, feeding pattern, and ruminal characteristics were monitored. Measurements of ruminal volume determined by total collection and indigestible marker (lithium sulfate) suggested that only about 50% of total ruminal contents were actually exchanged. Fasted lambs had lower (P less than .05) DMI, ruminal fermentative capacity, ruminal DM weight, and ruminal DM percentage than fed lambs during the first 4 d of realimentation. Exchange of ruminal contents did not (P greater than .10) affect DMI, feeding pattern, ruminal fluid pH, ruminal fermentative capacity, ruminal contents DM percentage, ruminal nucleic acid concentration, or VFA. Dosing fasted lambs with ruminal contents from nonfasted lambs reduced (P less than .05) ruminal liquid volume, dry weight of ruminal contents, and propionate concentration. Results of this trial are interpreted to indicate that although decreased ruminal function is a factor in the low feed intakes of fasted ruminants, the possibility of increasing postfast feed intake via improved ruminal function is limited because other metabolic factors may play a more important role.     

Effect of ruminal infusion of glucose, volatile fatty acids and hydrochloric acid on mineral metabolism in sheep

Two experiments were conducted to study the effects of alterations in ruminal pH and volatile fatty acid (VFA) concentrations on utilization of Mg and other minerals. In Exp. 1, two metabolism trials were conducted with 12 ruminally cannulated crossbred wethers fed 800 g/d of orchard-grass (Dactylis glomerata, L.) hay. After each feeding, wethers were ruminally infused with 500 ml (4.2 ml/min) or either 1) deionized water, 2) 40% (w/v) glucose solution, 3) .26 M propionic and .17 M butyric acid solution or 4) .35 M HCl. The pH of the VFA solution was adjusted to 6.8 with 10N NaOH. In Exp. 2, a metabolism trial was conducted with 12 ruminally cannulated crossbred wethers fed 600 g of orchard-grass hay and infused with a buffered VFA solution prepared as in Exp. 1 or with an unbuffered solution. In both experiments each trial consisted of a 5-d adaption period followed by four 5-d collections of feed, feces and urine. Compared with the glucose treatment, infusion of the buffered VFA solution produced similar acetic and propionic and higher (P less than .05) butyric acid concentrations (Exp. 1). The HCl solution produced changes in ruminal and pH values similar to those of the glucose infusion. In Exp. 1, apparent absorption of Mg was increased over twofold by the glucose infusion (P less than .05), but the other infusions had no effect. Apparent absorption of P was decreased (P less than .05) by HCl infusion, and K absorption was decreased by HCl and glucose infusions. In Exp. 2, infusion of the unbuffered VFA solution decreased apparent Mg absorption by 15.7%, compared with infusion of the buffered solution. These experiments suggest that the increased Mg absorption observed with carbohydrate supplementation is not due to alterations in ruminal pH or VFA levels.     

Alternate day supplementation of corn stalk diets with soybean meal or corn gluten meal fed to ruminants.

Four experiments were conducted to determine the effect of adding corn gluten mean (CGM) or soybean meal (SBM) at 24- or 48-h intervals to diets based on corn stalks. In each experiment corn stalks was the primary diet ingredient fed to wethers or steers. Monensin was also fed to determine whether its effects on ruminal fermentation would improve the efficiency of N utilization under these conditions. Evaluation criteria included ruminal fermentation characteristics, DM intake and utilization, N balance in sheep, and steer feedlot performance. Ruminal ammonia nitrogen (NH3 N) concentrations measured over time were higher (P < .05) when diets contained SBM. Diet did not influence (P > .10) total VFA concentrations in ruminal fluid. Differences in diurnal shifts in ruminal NH3 N and total VFA due to protein source resulted in diet x hour interactions (P < .05). Dry matter intake response to protein source and frequency of supplement feeding was variable. Dry matter digestibility and nitrogen digestibility were not affected (P > .10) by protein source or feeding interval. The 48-h interval feeding of CGM was favorable compared with 24-h interval feeding (P < .05). The opposite response occurred with SBM, resulting in a diet x feeding interval interaction (P < .05). Nitrogen retention was greater (P < .05) when CGM was fed and with alternate day feeding. Diets that contained CGM supported higher (P < .05) ADG and gain/feed than diets that contained SBM when fed to steer calves. Alternate day feeding of supplements that contained monensin was detrimental to steer performance under the conditions of these experiments. Corn gluten meal is an effective substitute for SBM when alternate day protein supplementation is practiced.     

Amino acid flux in ruminal and gastric veins of sheep: effects of ruminal and omasal injections of free amino acids and carnosine

The possibility of free amino acid (FAA) and peptide absorption across the ruminant stomach wall was studied in multicatheterized wethers fed every 12 h. During the last third of the feeding cycle, two intraruminal or intraomasal injections of solutions containing increasing amounts of Ser, Gly, Val, Met, Phe, Lys, and carnosine were successively performed. Before injections, a net uptake of each of these FAA was measured in the ruminal and the gastric veins. The ruminal injections produced a linear increase in ruminal FAA concentration. The highest ruminal concentrations (observed with 3 g of FAA and carnosine) ranged between 5 and 14 mM. After ruminal injections, Ser (P < .05), Gly (P < .05), Val (P < .05), Met (P < .10), and Lys (P < .10) uptake decreased and carnosine net release linearly increased (P < .05), suggesting absorption across the ruminal epithelium. Owing to the low net flux generated by high ruminal concentration, the ruminal epithelium permeability to these molecules seemed to be low. After omasal injections, net flux of injected FAA were not modified, suggesting a low permeability of the gastric epithelia to FAA. Carnosine net release linearily increased (P < .05) with increasing level of carnosine injection, indicating the possibility of dipeptide absorption at the gastric level. This study demonstrated in vivo that the stomach epithelia possess the capacity to absorb FAA and small peptides; however, the permeability of these epithelia to these molecules seemed limited.     

Influence of feed intake fluctuation and frequency of feeding on nutrient digestion, digesta kinetics, and ruminal fermentation profiles in limit-fed steers

Nine crossbred beef steers (344 +/- 26 kg) fitted with ruminal cannulas were used in a randomized complete block design to evaluate the effects of feeding frequency and feed intake fluctuation on total tract digestion, digesta kinetics, and ruminal fermentation profiles in limit-fed steers. In Period 1, steers were allotted randomly to one of four dietary treatments: 1) feed offered once daily at 0800; 2) feed offered once daily at 0800 with a 10% fluctuation in day-to-day feed intake; 3) feed offered twice daily at 0800 and 1700; and 4) feed offered twice daily at 0800 and 1700 with a 10% fluctuation in a day-to-day feed intake. In Period 2, steers were reallocated across treatments. The 90% concentrate diet was fed at 90% of the ad-libitum consumption by each steer. Chromium-EDTA and Yb-labeled steam-flaked corn were intraruminally infused at 0800 on d 1 and 3 and Co-EDTA and Er-labeled steam-flaked corn were infused on d 2 and 4 of the 4-d collection period. Ruminal samples were collected at 0, 3, 6, 9, 12, 15, 18, and 24 h after the 0800 feeding, and total feces were collected for 4 d. Total tract digestibilities of OM, N, and starch were lowest (fluctuation x frequency, P < .05) when feed was offered twice daily with a 10% fluctuation in intake. Ruminal fluid volume and passage rate were not affected (P > .10) by feeding frequency or intake fluctuation. A frequency x fluctuation x sampling time interaction occurred (P < .01) for ruminal pH. Steers fed a constant amount of feed once daily had higher (P < .05) ruminal pH at 0, 3, 18, and 24 h than steers fed once daily with a 10% fluctuation in feed intake. Total VFA concentration was greater (P < .01) at 9 h after the 0800 feeding when feed was offered once vs twice daily. Feeding twice daily increased (P < .05) the molar proportion of acetate and decreased (P < .05) the molar proportion of propionate. Increasing feeding frequency resulted in a more stable ruminal environment; however, the increased acetate:propionate ratio with twice-daily feeding might result in lower efficiency of energy utilization by limit-fed steers.     

Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle

The objective of these experiments was to establish the relationship of plasma ghrelin concentrations with feed intake and hormones indicative of nutritional state of cattle. In Exp.1, 4 steers (BW 450 +/- 14.3 kg) were used in a crossover design to compare plasma ghrelin concentrations of feed-deprived steers with those of steers allowed to consume feed and to establish the relationship of plasma ghrelin concentrations with those of GH, insulin (INS), glucose (GLU), and NEFA. After adaptation to a once-daily feed offering (0800), 2 steers continued the once-daily feeding schedule (FED), whereas feed was withheld from the other 2 steers (FAST). Serial blood samples were collected via indwelling jugular catheter from times equivalent to 22 h through 48 h of feed deprivation. Average plasma ghrelin concentrations were greater (P < 0.001) in FAST compared with FED (690 and 123 +/- 6.5 pg/mL) steers. Average plasma ghrelin concentrations for FED steers prefeeding were elevated (P < 0.001) when compared with those postfeeding (174 and 102 +/- 4.2 pg/mL, respectively). Average plasma GH concentration was elevated (P < 0.05) for FAST steers compared with FED steers. Plasma GLU concentrations were not different; however, for FAST steers, NEFA concentrations were elevated (P < 0.001) and INS concentrations were decreased (P < 0.001). In Exp. 2, 4 steers (BW 416 +/- 17.2 kg) were used in a crossover design to determine the effects of i.v. injection of bovine ghrelin (bGR) on plasma GH, INS, GLU, and NEFA concentrations; length of time spent eating; and DMI. Steers were offered feed once daily (0800). Serial blood samples were collected from steers via indwelling jugular catheter. Saline or bGR was injected via jugular catheter at 1200 and 1400. A dosage of 0.08 microg/kg of BW bGR was used to achieve a plasma ghrelin concentration similar to the physiological concentration measured in a FAST steer in Exp. 1 (1,000 pg/mL). Injection of bGR resulted in elevated (P < 0.005) plasma GH concentrations after the 1200 but not the 1400 injection. Plasma INS, GLU, and NEFA concentrations were not affected by bGR injection. For the combined 1-h periods postinjection, length of time spent eating was greater (P = 0.02) and DMI tended to be increased (P = 0.06) for bGR steers. These data are consistent with the hypothesis that ghrelin serves as a metabolic signal for feed intake or energy balance in ruminants.     

Ruminal fermentation and duodenal flow following progressive inoculations of fauna-free wethers with major individual species of ciliate protozoa or total fauna

Naturally fauna-free (FF) wethers, equipped with ruminal and duodenal cannulas, were used in two groups of eight (Group A) and seven (Group B) animals in six consecutive experimental periods, each lasting for 28 d. The objective was to measure ruminal fermentation traits, and flows of nonammonia nitrogen (NAN), total amino acid (TAA), and bacterial nitrogen (BN) from the stomach after inoculation with individual ciliate protozoa species in each period. The wethers in both groups were fed a diet based on corn silage, haylage, and soybean meal, and they remained FF during the first period. At the beginning of each other period, the wethers were progressively inoculated intraruminally with one individual major species of ruminal ciliate protozoa or total fauna (TF). Thus, Group A was progressively inoculated (+) with Dasytricha ruminantium (DS), Polyplastron multivesiculatum (PP), Isotricha intestinalis (IS), Entodinium caudatum (EN) and TF-type A. Also, Group B was progressively inoculated (+) with IS, DS, Epidinium ecaudatum (EP), Eudiplodinium maggi (EU), and EN. Duodenal digesta and ruminal fluid were collected and sampled in each period on d 26 and 28, respectively, and subjected to chemical analyses. A significantly higher (P < .05) pH (6.4) in ruminal fluid of the Group A wethers was obtained when each DS, DS+PP, DS-PP-IS+EN, and TF population was present in the rumen than when the wethers were FF (6.2). In the Group B wethers, pH (6.1) was lower (P < .05) for the population of IS-DS-EP+EU than for other populations (6.2 to 6.3). The concentration of total VFA in ruminal fluid was higher (P < .05) in the Group B wethers when IS, IS+DS, or IS-DS+EP populations were present in the rumen than when the wethers were FF. The flow of NAN, TAA, and BN from the stomach to the intestinal tract was generally lower for different protozoa populations than for the FF period. Largest decreases (P < .05) in the flow of NAN, TAA, and BN occurred when EN was added into the rumen of wethers in the A and B groups, which already contained populations of DS-PP+IS and IS-DS-EP+EU, respectively. Holotrich protozoa had very little effect on the protein metabolism in the rumen, but cellulolytic protozoa (PP, EP, and EU) and EN decreased the efficiency of protein utilization by the ruminant host.     

Effects of level of feeding and ruminally undegraded protein on ruminal bacterial protein synthesis, escape of dietary protein, intestinal amino acid profile, and performance of dairy cows.

Six cannulated lactating cows were used in two replicated, concurrently run 3 x 3 Latin square experiment to study the interaction between level of feeding and diets differing in ruminally undegraded protein (RUP) on bacterial protein synthesis, ruminal escape of dietary protein, and flow of total and individual amino acids (AA) to the small intestine. Treatments consisted of three diets formulated to contain 69 g (HL), 53 g (HH), and 48 g (LL) of RUP per kilogram of DM, respectively. Measurements were made in early lactation, at high feeding level (19.3 kg DM/d), and repeated at late lactation (9.8 kg DM/d, low feeding level) with the same animals and diets. Decreasing feed intake increased (P < .05) the apparent digestibility of OM, NDF, and ADF in the rumen and the total tract, decreased (P < .05) ruminal liquid and particulate passage rate and total ruminal VFA concentration, and increased ruminal pH and ammonia concentration. Decreased level of intake reduced the (P < .05) efficiency of bacterial N synthesis (28.1 vs 23.7 g bacterial N/kg OM truly digested in the rumen) and decreased (P < .05) ruminal protein degradation rate measured with an in situ method. Duodenal flow of nonammonia nitrogen (NAN), and total AA were highest (P < .05) for the HL diet and lowest (P < .05) for the LL diet at the high feeding level. However, at the low feeding level, diet composition did not affect the amount of NAN or total AA passing to the small intestine. Diet HL increased the proportion of Met, His (P < .05), and Arg (P < .07) in the duodenal digesta at both feeding levels. When purines were used to calculate bacterial N synthesis, no differences between diets were detected. However, when diaminopimelic acid was used, highest bacterial N synthesis was detected for diet HH at the high feeding level. Diet HL supported the highest (P < .05) milk protein production at the high feeding level, and the highest (P < .05) milk protein content at the low feeding level. In conclusion, level of feeding and amount of RUP altered the amount and composition of AA presented to the cows.     

Macromineral absorption in sheep fed tetany-prone and non-tetany-prone hays

Two experiments were conducted to determine some of the factors that led to hypomagnesemic tetany associated with the feeding of two orchardgrass hays. Sixteen mature Columbia and Suffolk wethers (62 to 72 kg), four of which were fitted with ruminal and abomasal cannulae, were fed one of two tetany-prone orchardgrass hays or a non-tetany-prone bromegrass hay. In Exp. 1, 12 wethers were used in a completely random design metabolism experiment to measure apparent absorption and retention of macrominerals. In Exp. 2, four wethers with ruminal and abomasal cannulae were used in a completely random design experiment to monitor pre-intestinal mineral absorption and ruminal characteristics. This experiment was replicated once, with wethers remaining on their diets for 16 d in each replication. In the metabolism experiment, apparent absorption and retention of Mg as a percentage of intake were lower (P less than .01 and P less than .05) for one tetany-prone orchardgrass hay compared with the other orchardgrass hay. Pre-intestinal absorption of Mg in the cannulated wethers was greater (P less than .01) for the orchardgrass hays than for the bromegrass hay. Pre-intestinal Mg absorption was higher (P less than .01), both in terms of grams per day and a percentage of intake for the orchardgrass hay with the highest Mg content. In the noncannulated wethers, the percentage of water-soluble Mg in the feces was lower (P less than .01) for the tetany-prone hays, indicating that a decrease in Mg solubility in the intestine may have influenced Mg apparent absorption.(ABSTRACT TRUNCATED AT 250 WORDS)     

Performance, methanogenesis and nitrogen metabolism of finishing steers fed monensin and nickel

Sixty-four Angus steers initially averaging 354 kg were allotted to a 2 X 2 factorial arrangement of treatments to determine the effects of dietary Ni (0 or 5 mg/kg supplemental), monensin (0 or 33 mg/kg) and their possible interaction on performance, methane production and N metabolism. The basal diet was a high energy, corn-cottonseed hull based diet containing 10.2% crude protein and .30 mg/kg Ni on a dry matter basis. Monensin reduced (P less than .05) feed intake, did not affect average daily gain and improved (P less than .05) feed conversion over the 102-d study. Nickel supplementation did not significantly alter or interact with monensin to affect steer performance. However, steers fed Ni tended to have higher average daily gains and improved feed conversions. Monensin decreased (P less than .05) in vitro methane production, altered several carcass traits, increased (P less than .05) molar proportion of ruminal propionate and decreased (P less than .05) molar proportion of ruminal acetate. Nickel did not alter methane production, carcass characteristics or ruminal volatile fatty acid proportions. Both monensin and Ni increased (P less than .05) ruminal fluid urease activity when samples were obtained before feeding. A significant monensin X Ni interaction was found to affect ruminal epithelial urease activity. Monensin increased ruminal epithelial urease in steers not receiving supplemental Ni, but had no effect on ruminal epithelial urease activity in steers fed supplemental Ni. Ruminal fluid protein and ammonia-N were decreased (P less than .05) by monensin. Results of this study indicate that Ni may interact with monensin to affect ruminal epithelial urease activity but not performance or methane production in finishing steers.     

Effects of wet corn gluten feed and intake level on diet digestibility and ruminal passage rate in steers

Twelve ruminally cannulated Jersey steers (BW = 534 kg) were used in an incomplete Latin square design experiment with a 2 x 2 factorial arrangement of treatments to determine the effects of wet corn gluten feed (WCGF) and total DMI level on diet digestibility and ruminal passage rate. Treatments consisted of diets formulated to contain (DM basis) steam-flaked corn, 20% coarsely ground alfalfa hay, and either 0 or 40% WCGF offered once daily for ad libitum consumption or limited to 1.6% of BW (DM basis). Two consecutive 24-d periods were used, each consisting of 18 d for adaptation, 4 d for collection, and a 2-d in situ period. Rumens of all steers were evacuated once daily at 0, 4, 8, and 12 h after feeding. Chromic oxide (10 g/[steer*d]) was fed as a digestibility marker, and steers were pulse-dosed with Yb-labeled alfalfa hay to measure ruminal particulate passage rate. Dacron bags containing 5 g of steam-flaked corn, WCGF, or ground (2-mm screen) alfalfa hay were placed into the rumens of all steers and removed after 3, 6, 12, or 48 h. Wet corn gluten feed increased percent apparent total-tract digestion of OM (P < 0.01), NDF (P < 0.01), and starch (P < 0.03), decreased (P < 0.01) ruminal total VFA concentration, increased (P < 0.01) ruminal NH3 concentration, and increased (P < 0.01) ruminal pH. Wet corn gluten feed also increased (P < 0.01) ruminal passage rate of Yb. Limit feeding decreased (P < 0.01) percent apparent total-tract digestion of both OM and NDF, ruminal total VFA concentration (P < 0.01), and ruminal fill (P < 0.01), but increased (P < 0.01) ruminal NH3 concentration. Apparent total-tract digestion of starch was not affected (P = 0.70) by level of DMI. A DMI level x hour interaction (P < 0.01) occurred for ruminal pH. Limit feeding increased ruminal pH before and 12 h after feeding, but decreased ruminal pH 4 h after feeding compared with diets offered ad libitum. A diet x DMI level interaction (P < 0.02) occurred for in situ degradation of alfalfa hay, with dietary addition of WCGF increasing (P < 0.02) the extent of in situ alfalfa hay degradation in steers fed for ad libitum consumption. This study suggests that WCGF increases OM and NDF digestion, and that limit feeding diets once daily might depress OM and NDF digestion, possibly due to decreased stability of the ruminal environment.     

Effects of diet concentrate level and sodium bicarbonate on site and extent of forage fiber digestion in the gastrointestinal tract of wethers

Four adult wethers (45 kg) with permanent ruminal and abomasal cannulae were used in a repeated measures Latin-square arrangement of treatments to quantitate the effects of diet concentrate level and sodium bicarbonate (NaHCO3) on site and extent of forage fiber digestion in the gastrointestinal tract. Experimental diets consisted of Kentucky-31 tall fescue hay, soybean meal and a semi-purified concentrate mixture in ratios of 95:5:0, 76:4:20, 57:3:40 and 38:2:60; NaHCO3 represented 0 or 7.5% of the concentrate mixture. Ruminal digestion (% of intake) of neutral detergent fiber (NDF) and hemicellulose decreased linearly (P less than .05), whereas acid detergent fiber (ADF) digestion responded in a cubic (P less than .05) fashion to increasing concentrate level; NaHCO3 improved ruminal digestion of NDF (P less than .10) and ADF (P less than .05), but not hemicellulose. Post-ruminal digestion (% of rumen non-degraded) of NDF and ADF tended to increase, whereas hemicellulose digestion responded in a cubic (P less than .05) fashion to increasing concentrate level; NaHCO3 decreased (P less than .05) post-ruminal digestion of all fiber fractions. Total tract digestion of NDF and ADF showed a cubic (P less than .05) response, whereas hemicellulose digestion responded in a quadratic (P less than .05) fashion to increasing concentrate level; NaHCO3 had no effect on total tract digestion of any fiber fraction. Correlations of ruminal hemicellulose digestion with mean pH (r = .33; P = .07) and minimum pH (r = .30; P = .09) were attained in a 24-h feeding cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of bentonite on wool growth and nitrogen metabolism in fauna-free and faunated sheep.

Two experiments were carried out with sheep that originated from a fauna-free flock and were fed a soybean meal-corn silage diet with or without a bentonite supplement. One-half of the sheep fed each diet in each experiment were faunated with a mixed population of ruminal protozoa, whereas the other half of the sheep remained fauna-free until the end of both experiments. Wool growth and daily gain were measured in Exp. 1. (eight rams per treatment), which lasted 110 d, and the metabolic effects in the rumen and intestinal tract of protozoa and dietary bentonite supplement were tested with cannulated wethers (four wethers per treatment) in Exp. 2. The results of Exp. 1 showed decreased wool growth (P less than .05) due to the presence of protozoa in the rumen. Dietary supplementation with bentonite partly offset the decreased wool growth in sheep with protozoa, but there were no effects of dietary bentonite and no protozoa x bentonite interaction (P greater than .05). Daily gain was decreased by the dietary bentonite (P less than .05) supplement but was not affected (P greater than .05) by the ruminal presence of protozoa. In Exp. 2, protozoa increased (P less than .01) the ruminal concentrations of ammonia and decreased (P less than .05) the acetic:propionic acid molar ratio. Fractionation of N in the duodenal digesta flowing from the stomach to the small intestine showed that protozoa decreased (P less than .05) the flow of nonammonia N and bacterial N, and there was a protozoa x bentonite interaction for these effects (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of aluminum-citrate and citric acid on tissue mineral composition in wether sheep

A 60-d trial was conducted to determine effects of A1-citrate and citric acid on tissue mineral composition in wether lambs. Eighteen crossbred, yearling wether lambs equipped with ruminal cannulas were fed a diet containing low (.12%) Mg and high (2.87%) K (DM basis) and were allotted to three treatments: 1) control; 2) 2,000 micrograms A1 as A1-citrate/g of diet DM and 3) citric acid equivalent to the citrate in treatment 2. Treatments were administered in 200 ml of deionized water twice daily in divided doses via ruminal cannula. At the end of 60 d, wethers were slaughtered and samples of rib and tibia bone, liver, kidney, brain, spleen, pancreas, parathyroid and pituitary gland were analyzed for mineral concentration. Concentrations of A1 increased (P less than .05) in rib, tibia, liver, kidney, spleen and pituitary gland and tended to increase in brain (P less than .13) in wethers treated with A1-citrate compared to citric acid. Magnesium was decreased in rib (P less than .01) and tended to be decreased in pituitary gland (P less than .15), whereas Ca tended to be decreased in pancreas (P less than .07), kidney (P less than .11) and parathyroid (P less than .10) by A1-citrate treatment compared to citric acid. Potassium decreased (P less than .01) in liver, Fe increased (P less than .05) in kidney, Zn decreased in pituitary (P less than .05) and tended to decrease in pancreas (P less than .10) due to A1-citrate but not citric acid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Utilization of magnesium and other macrominerals in sheep supplemented with different readily-fermentable carbohydrates

Sheep were used to determine the effects of dietary supplementation with readily-fermentable carbohydrates on Mg, Ca, K and P utilization. In each of two metabolism trials, 15 mature, crossbred wethers (average weight, 49.2 kg) were allotted to five dietary treatments consisting of 800 g/d of orchardgrass (Dactylis glomerata, L.) hay alone, or supplemented with 450 g/d of either glucose, sucrose, lactose or starch. Each trial consisted of a 5-d adjustment period, a 10-d preliminary period and a 10-d collection period. Compared with wethers fed hay alone, supplementation with each kind of carbohydrate to the diet decreased (P less than .05) fecal Mg excretion and increased (P less than .05) apparent absorption and retention of Mg. Apparent absorption of the Ca was lower (P less than .05) in wethers fed lactose and tended to be decreased by glucose, sucrose and starch supplementation. Calcium retention was lower (P less than .05) in wethers fed sucrose and lactose, compared with those fed hay alone. All types of supplementary carbohydrates depressed (P less than .05) apparent absorption and urinary excretion of K. Serum Mg and Ca were not affected and serum K was depressed (P less than .05) by carbohydrate supplementation. Ruminal fluid pH was decreased (P less than .05) by glucose and lactose supplementation, and addition of these carbohydrates tended to decrease molar proportions of acetate and increase those of propionate and butyrate, compared with sheep fed hay alone. Sucrose addition decreased (P less than .05) acetate and increased (P less than .05) butyrate molar proportions in the ruminal fluid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intestinal supply of amino acids in sheep fed alkaline hydrogen peroxide-treated wheat straw-based diets supplemented with soybean meal or combinations of corn gluten meal and blood meal

The intestinal supply of amino acids (AA) in sheep fed alkaline hydrogen peroxide-treated wheat straw (AHPWS)-based diets supplemented with soybean meal (SBM) or corn grain plus combinations of corn gluten meal (CGM) and blood meal (BM) was measured in a 5 X 5 latin square. Sheep (avg wt 45 kg) with ruminal, duodenal and ileal cannulas were fed diets containing 65% AHPWS supplemented with the following protein sources: soybean meal (SBM), corn gluten meal (CGM), blood meal (BM), 2/3 CGM:1/3 BM and 1/3 CGM:2/3 BM. Total nitrogen (N) flow at the duodenum was not affected (P greater than .05) by protein source. Flows of bacterial N and AA increased (P less than .05) and flows of nonbacterial N and AA decreased (P less than .05) when wethers were fed SBM vs corn plus other protein sources. When diets contained SBM, quantities of total AA at the duodenum were lower (P less than .05) and the profile of AA supplied to the intestine was altered substantially. Total flows of AA at the duodenum and total quantities of AA disappearing from the small intestine were similar (P greater than .05) for all diets containing BM and CGM, but flows and disappearance of valine, histidine, lysine and arginine increased linearly (P less than .05), whereas flows and disappearance of leucine, isoleucine and methionine decreased linearly (P less than .05) as BM replaced CGM in the diets. Results suggest that quantities of individual AA flowing to the duodenum and disappearing from the intestine of wethers fed AHPWS-based diets can be altered by source of dietary protein. Furthermore, feeding protein sources resistant to ruminal degradation in combination may improve the profile of AA supplied to the intestine.     

Influence of alfalfa maturity on feed intake and site of nutrient digestion in sheep

Four wethers fitted with ruminal, duodenal and ileal cannulas were used to study effects of maturity of alfalfa hay on intake, digestion and rate of passage of nutrients in various sites of the digestive tract. Pre-, early-, and mid-bloom hays were harvested from the same field; full-bloom hay was acquired from elsewhere due to wether conditions. Dry matter intake decreased (P less than .05) as intakes of NDF and ADF increased. This was attributed to decreased digestibility and increased retention time of undigested residues. Digestion of OM in the stomach (% of intake) was 44.2, 47.4, 38.8 and 35.1 for pre-, early-, mid- and full-bloom hay, respectively. Digestion of ADF in the stomach was lower for mid-bloom than for pre-and early-bloom hay (P less than .05). Degradation of alfalfa protein in the rumen was 94, 88, 81 and 78% for pre-, early-, mid- and full-bloom hay, respectively. Concentration of ruminal NH3 N, flow of N at the duodenum, fecal N and urinary N decreased of the hay and to N intake. Digestion of N in the small intestine (g/d) decreased as maturity advanced (P less than .05). Duodenal flow of total amino acids was greater (P less than .05) when animals consumed pre-bloom hay than when they consumed more mature hays. Relative feed value calculated from the detergent fiber analysis correlated with actual value determined biologically (r = +.81). Intake and site of nutrient digestion of alfalfa hay were influenced by the stage of maturity at harvest.     

The effects of corn milling coproducts on growth performance and diet digestibility by beef cattle

Simmental x Angus weanling heifers (n = 96; 239 +/- 2.3 kg) were used in four replications to evaluate three dietary treatments in Trial 1. Treatments were cracked corn-hay diets supplemented with one of three corn milling industry coproducts: dry corn gluten feed (DCGF), dried distillers grains (DDG), and a new modified corn fiber (MCF). In Trial 2, ruminally cannulated mature crossbred beef steers (n = 4; 606 +/-60 kg) were used in a 4 x 4 Latin square with 11-d periods to determine digestibility and ruminal metabolism of limit-fed cracked corn-alfalfa haylage diets supplemented with cornstarch (CON), DCGF, DDG, or MCF. During Periods 3 and 4, an in situ study was conducted to compare the rate and extent of CP degradation of DCGF, DDG, and MCF. In Trial 1, there were no differences (P > .10) in initial weights or DM intake. Average daily gain and feed efficiency (G/F) were improved (P < .01) for heifers fed DCGF or DDG vs heifers fed MCF. In Trial 2, no differences (P > . 10) in digestibilities of any nutrients or in ruminal VFA concentrations were observed for steers fed coproducts. The CON supplementation decreased (P < .05) total dietary fiber (TDF) digestibility, improved (P < .10) digestibilities of DM and OM, increased (P < .05) total VFA concentrations and concentrations of propionate and valerate, and decreased (P < .05) concentrations of butyrate, isobutyrate, and isovalerate when compared with the coproducts. Dry corn gluten feed increased (P < .05) and DDG tended (P < .10) to increase percentages of the immediately soluble fraction of CP, and both had increased (P < .05) rates (Kd) and greater (P < .05) extent of ruminal CP degradation than MCF. These data suggest that DCGF and DDG may be utilized in limit-fed high-energy diets without sacrificing performance. Feeding of MCF resulted in poorer performance of heifers, suggesting a limited feeding value that results from high ADIN content and slow in situ protein digestion.     

Resistance of feed enzymes to proteolytic inactivation by rumen microorganisms and gastrointestinal proteases.

Potential feed enzyme additives for ruminants were tested in vitro for their stability to ruminal microbial and gastrointestinal proteolysis. Four commercial preparations from Trichoderma longibrachiatum (A, B, C, and D) and one from an undisclosed source (E) were incubated up to 6 h with ruminal fluid taken from four lactating dairy cows before or 2 h after feeding. The stability of preparation B was also tested in the presence of pepsin at pH 3 and pancreatin at pH 7. Cellulase (EC 3.2.1.4), cellulose 1,4-beta-cellobiosidase (EC 3.2.1.91), beta-glucanase (EC 3.2.1.6), xylanase (EC 3.2.1.8), beta-glucosidase (EC 3.2.1.21), and beta-xylosidase (EC 3.2.1.37) activities were monitored throughout the incubations. Polysaccharidase activities of all enzyme preparations were remarkably stable in ruminal fluid taken after feeding. Ruminal fluid obtained before feeding inactivated the polysaccharidases in preparations B and D to a greater extent than ruminal fluid obtained after feeding. Cellulase and cellulose 1,4-beta-cellobiosidase activities were the least stable, declining (P < 0.05) by 35 and 60% for preparations B and D, respectively. Xylanase activity of preparation D decreased (P < 0.05) by up to 30% after 6 h of incubation, whereas beta-glucanase activity was not affected. The ability to degrade exogenous enzymes also differed among cows (P < 0.05). Pepsin and acid (pH 3.0) did not affect polysaccharidases in preparation B but decreased glycosidase activities by 10 to 15% (P < 0.05) after 1 h of incubation. Pancreatin, at the maximum concentration used, inactivated cellulase, cellulose 1,4-beta-cellobiosidase, and xylanase activities at a rate of 0.55, 1, and 0.45%/min, respectively. beta-Glucosidase and beta-xylosidase activities decreased by 1 and 0.75%/min, respectively. Partial proteolysis of cellulase, cellulose 1,4-beta-cellobiosidase, and xylanase by pancreatin produced a transient increase in activity. This twofold increase for cellulase and fourfold increase for cellulose 1,4-beta-cellobiosidase was directly proportional to pancreatin concentration. These results suggest that the enzyme feed additives tested were stable in the rumen of animals after feeding. Exogenous enzymes are likely to be more susceptible to the host gastrointestinal proteases in the abomasum and intestines than to ruminal proteases. However, exogenous polysaccharidases may survive for a considerable period of time in the small intestine and they probably maintain activity against target substrates in this environment.     

Influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide on ruminant nitrogen metabolism: II. Ruminal nitrogen metabolism, diet digestibility, and nitrogen balance in lambs

Three lamb metabolism experiments were conducted to investigate the effects of chronic administration of the novel urease inhibitor N (n-butyl) thiophosphoric triamide (NBPT) on ruminal N metabolism, fermentation, and N balance. In Exp. 1, ruminally cannulated wethers (n = 28; 45.0 +/- .9 kg) were administered one of seven doses of NBPT (0 [control], .125, .25, .5, 1, 2, or 4 g of NBPT daily) and fed a common cracked corn/cottonseed hull-based diet twice daily containing 2% urea at 2.5% of initial BW for the duration of the 15-d experiment. Overall, NBPT decreased (linear P < .0001; quadratic P < .001) ruminal urease activity, resulting in linear increases (P < .0001) in ruminal urea and decreases in ruminal NH3 N concentrations. However, the detection of an NBPT x day interaction (d 2 vs 15; P < .01) indicated that this depression in urea degradation diminished as the experiment progressed. Increasing NBPT linearly decreased (P < .01) total VFA concentrations on d 2 of the experiment, but it had no effect (P > .10) on d 15. Increasing NBPT had no effect (P > .10) on DM or ADF digestibilities, but it linearly decreased (P < .01) N digestibility. Supplementing NBPT produced a linear increase (P < .05) in urinary N excretion and a linear decrease (P < .01) in N retention. In Exp. 2, ruminally cannulated wethers (n = 30; 46.8 +/- .6 kg) were fed one of two basal diets (2.0 vs 1.1% dietary urea) at 2.5% of initial BW and dosed with either 0 (control), .25, or 2 g of NBPT daily for the duration of the 15-d experiment. There were no NBPT x dietary urea interactions (P > .10) for Exp. 2. Increasing NBPT depressed (linear and quadratic P < .0001) ruminal urease activity, producing linear (P < .0001) increases in urea N and linear decreases in NH3 N in the rumen. As in Exp. 1, an NBPT x day interaction (P < .05) was noted for urea, NH3 N, and total VFA concentrations; the maximum response to NBPT occurred on d 2 but diminished by d 15 of the experiment. Administration of NBPT did not influence (P > .10) DM, ADF, or N digestibilities in Exp. 2. In Exp. 3, wether lambs (n = 30; 26.4 +/- .7 kg) were subjected to the same treatment regimen as in Exp. 2 for a 14-d N balance experiment. Although several NBPT x dietary urea interactions (P < .05) were noted, increasing NBPT did not affect (P > .10) N digestibility. Administration of NBPT quadratically increased (P < .10) urinary N excretion, producing a linear decrease (P < .05) in N retention. These results suggest that although NBPT is capable of inhibiting ruminal urease short-term, the ruminal microflora may be capable of adapting to chronic NBPT administration, thereby limiting its practical use in improving the utilization of dietary urea.