Site and extent of nutrient digestion by steers fed a low-quality bromegrass hay diet with incremental levels of soybean hull substitution.

Five ruminally and duodenally cannulated steers were fed bromegrass hay (H; 5.6% CP; 70.9% cell wall) substituted with 0, 15, 30, 45, or 60% soybean hulls (SH; 10.5% CP; 87.9% cell wall) at 90% of ad libitum DMI. Diets were made isonitrogenous (11% CP) by addition of isolated soybean protein (91.5% CP). Total ruminal VFA concentration, molar proportion of acetate, and molar acetate:propionate ratio increased (linear; P less than .02) with increasing level of SH substitution, but propionate (mol/100 mol) and ruminal fluid passage rate decreased (linear; P less than .01). Ruminal pH and ammonia concentration decreased more rapidly, and to a greater extent and duration, as level of SH increased; neither was decreased to levels considered detrimental to fiber digestion. Ruminal and total tract DM, OM, and cell wall digestibilities increased (linear; P less than .01), whereas total tract N digestibility decreased (linear; P = .03), as level of SH increased Total N flow to the duodenum increased (linear, P = .03) with increasing level of SH, and microbial N flow tended (cubic, P = .09) to increase. Microbial efficiencies were unchanged (P = .10) with SH level. True ruminal digestibilities of N did not differ (P greater than .10) among diets. Rate of in situ DM disappearance of H and SH was not influenced (P greater than .10) by SH substitution, although rate tended to be fastest with 30 and 45% SH (quadratic, P = .14). We infer from these data that SH can replace 60% of the DMI of a low-quality forage diet without decreasing OM or cell wall digestion.     

Effects of alkaline hydrogen peroxide treatment of wheat straw on site and extent of digestion in sheep

Two experiments (4 X 4 Latin squares) were conducted, using four multiple-cannulated wethers (mean body weight, 65 kg), to determine effects of treating wheat straw (WS) with alkaline solutions (pH 11.5) of hydrogen peroxide (AHP; .26 g hydrogen peroxide/g WS) on site and extent of nutrient digestion in sheep. Diets contained either 33 to 37% (low WS) or 70 to 72% (high WS) AHP-treated (T) or non-treated (C) WS. Treatment of WS with AHP resulted in increased acid detergent fiber and cellulose concentrations and decreased acid detergent lignin (ADL) concentrations compared with non-treated WS. In Exp. 1, intakes were held constant at approximately 1,044 g dry matter (DM)/d. When fed AHP-treated WS diets, wethers digested more (P less than .05) DM, neutral detergent fiber (NDF) and cellulose in the stomach (54.8, 47.4, 51.6 and 20.0%; 65.6, 68.8, 51.5 and 37.2%; 66.6, 74.2, 45.2 and 40.7% of intake, respectively, for low WS-T, high WS-T, low WS-C and high WS-C diets) and in the total tract (83.0, 74.8, 68.4 and 50.0%; 81.8, 81.0, 53.9 and 42.1%; 85.2, 86.9, 50.2 and 47.6%, respectively, for the low WS-T, high WS-T, low WS-C and high WS-C diets), and had lower (P less than .05) ruminal pH than when fed the non-treated WS diets. In Exp. 2, the same wethers were fed diets similar to those fed in Exp. 1, but at ad libitum intake. Wethers consumed less (P less than .05) feed when fed the high WS-C diet than when fed the other three diets (2,234, 2,526, 2,271 and 1,297 g/d for the low WS-T, high WS-T, low WS-C and high WS-C diets, respectively). Digestibilities of DM, NDF and cellulose were higher (P less than .05) when sheep were fed the treated WS diets than when fed the non-treated WS diets (82.7, 70.7, 68.4 and 58.0%; 78.6, 72.9, 49.4 and 51.6%; 78.0, 84.0, 53.8 and 37.5%, respectively, for the low WS-T, high WS-T, low WS-C and high WS-C diets). Fluid and particulate dilution rates in the rumen were higher (P less than .08) when wethers consumed AHP-treated WS diets compared with non-treated WS diets (8.21, 8.56, 6.96 and 6.81%/h; 6.06, 6.73, 4.05 and 3.15%/h, respectively, for the low WS-T, high WS-T, low WS-C and high WS-C diets). The AHP treatment was successful in overcoming the major barriers to microbial degradation of WS in the gastrointestinal tract of wethers.     

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.     

Effects of feeding alkaline hydrogen peroxide-treated wheat straw-based diets on intake, digestion, ruminal fermentation, and production responses by mid-lactation dairy cows.

The objective of this experiment was to determine the effects of feeding different levels of alkaline hydrogen peroxide-treated wheat straw (AHP-WS) in the diet on feed intake, nutrient digestion, ruminal fermentation, and production responses in mid-lactation dairy cows. Eight Holstein cows, averaging 147 d postpartum, were used in two replications of a 4 x 4 Latin square design. Complete mixed diets consisted of 70% forage and 30% concentrate (DM basis) with various levels of AHP-WS, alfalfa haylage, and corn silage as forage sources. Treatments contained 0 (control), 20.0, 40.1, or 60.0% AHP-WS in the diet. A quadratic effect (P = .08) of AHP-WS level on DMI was noted, with values of 2.16, 22.3, 20.8, and 18.9 kg/d for the control, 20.0, 40.1, and 60.0% AHP-WS treatments, respectively. Apparent digestibilities of DM, OM, CP, and ADF were not affected (P greater than .10) by replacing haylage and corn silage with increasing amounts of AHP-WS in the diet, but there was a linear increase (P = .03) in NDF digestibility (44% for control vs 59% for the 60.0% AHP-WS diet) and a parallel decrease (P less than .05) in cell content digestibility (82 vs 70% for these two diets). Yields of milk and 4% fat-corrected milk (FCM) were decreased (quadratic; P = .0001) as the level of AHP-WS increased in the diet. The addition of AHP-WS to the diet decreased the milk fat percentage from 3.72 to 3.60% (quadratic; P = .05) and decreased milk protein percentage from 3.27 to 3.13% (linear; P = .0001). Cows fed the higher levels of AHP-WS had linear increases (P = .0001) in ruminal concentrations of total VFA (128.0 mM for control vs 136.0 mM for the 60.0% AHP-WS treatment) and molar proportion of acetate, resulting in a quadratic effect (P less than .0001) on the acetate:propionate ratio. These data indicate that feeding the 40.1 and 60.0% AHP-WS diets lowered digestible DM and OM intakes, which resulted in reduced 4% FCM yield as nutrient intakes were decreased compared with cows fed the 20.0% AHP-WS diet or the control diet containing alfalfa haylage and corn silage. Although substituting AHP-WS for haylage and corn silage increased NDF digestibility and tended to increase digestible NDF intake, milk production was depressed because digestible DMI decreased.     

Degradation of wheat straw and alkaline hydrogen peroxide-treated wheat straw by Ruminococcus albus 8 and Ruminococcus flavefaciens FD-1

Degradation of wheat straw (WS) and alkaline hydrogen peroxide (AHP)-treated wheat straw (AHPWS) by Ruminococcus albus 8 and Ruminococcus flavefaciens FD-1 was determined by measuring the growth (OD600) of each bacterium and determining DM disappearance (DMD) of the substrate. Complex medium and defined medium with or without the addition of phenylpropanoic acid (PPA) and phenylacetic acid (PAA) were used. Tubes were incubated at 39 degrees C for 8 d. Both OD600 and DMD indicated that AHPWS was degraded to a much greater extent by either bacterium (R. flavefaciens FD-1, 60.8 +/- 1.8% and R. albus 8, 42.3 +/- 3.5%) vs untreated WS (R. flavefaciens FD-1, 16.5 +/- 1.8% and R. albus 8, 8.6 +/- 6%) in the complex medium. Most degradation occurred between d 1 and 4. With the complex medium, addition of PPA and PAA did not stimulate degradation by either bacterium. When the defined medium was used, the addition of PPA and PAA enhanced (P less than .05) degradation of AHPWS (39.6 +/- 2.6%) vs AHPWS with no added PPA and PAA (24.9 +/- 7.6%) by R. albus 8. There was no synergistic effect on degradation when the two species were co-cultured with either WS or AHPWS as the substrate. No effect of PPA and PAA on disappearance of AHPWS was observed for R. flavefaciens FD-1 or when the two bacteria were grown together. Dry matter disappearance analysis showed that R. flavefaciens FD-1 degraded AHPWS more rapidly (6.1 mg/d) than R. albus 8 did (4.2 mg/d) in complex medium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationships between chewing behavior, digestibility, and digesta passage kinetics in steers fed oat hay at restricted and ad libitum intakes

The objective of this study was to evaluate the relationships between chewing behavior, digestibility, and digesta passage kinetics in steers fed oat hay at restricted and ad libitum intakes. Four Hereford steers, with an initial average BW of 136 kg, were used in an experiment conducted as a balanced 4 × 4 Latin square with 4 treatments (levels of intake) and 4 periods. Animals were fed lopsided oat hay (Avena strigosa Schreb.) at 4 levels of intake (as a percentage of BW): 1.5, 2.0, 2.5, and ad libitum. Digestibility, chewing behavior, and digesta passage kinetic measurements were recorded during the experimental period. Chewing rates during eating and ruminating [(chews?min(-1))/g of DMI?kg(-1) of BW?d(-1)] decreased (P = 0.018 and P = 0.032, respectively) with increased DMI (g?kg(-1) of BW?d(-1)), whereas total chewing and total time spent on each chewing activity increased. Calculated total energy expended by the chewing activity was 4.2, 4.4, 5.2, and 5.3% of ME intake for DMI of 1.5, 2.0, and 2.5% of BW and ad libitum, respectively, indicating that adjustments in animal chewing behavior may be a mechanism of reducing energy expenditure when forages are fed at restricted intake. Hay digestibility decreased (P < 0.001) with increased DMI (r = -0.865). Digesta mean retention time (h) was strongly correlated with DMI (r = -0.868) and OM digestibility (r = 0.844). At reduced intake, hay digestibility was enhanced (P < 0.001) by extending digesta retention time and by increasing chewing efficiency, highlighting the relationship between chewing behavior and the digestive process. Fractional outflow rate of particulate matter from the reticulorumen (k(1)) was positively correlated with total chews, emphasizing that the decrease in particle size caused by chewing facilitates particle flow through the digestive tract. Increased hay intake also increased (P < 0.001) k(1), whereas passage rate of the liquid phase, transit time, and rumen fill were not affected (P > 0.05). The latter was correlated with rumen volume (r = 0.803). In conclusion, the results of this study indicate that animals fed at restricted intake increased chewing rate when eating and ruminating, which, along with a longer digesta retention time, contributed to enhance feed digestibility.     

Effects of supplemental protein source and level of urea on intestinal amino acid supply and feedlot performance of lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw.

Two experiments were conducted to determine the effects of supplemental CP source and level of urea on intestinal amino acid (AA) supply and feedlot performance of lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw (AHPWS). In Exp. 1, five cannulated (ruminal, duodenal, and ileal) crossbred wethers (61 kg) were used in a 5 x 5 Latin square design. Treatments consisted of different sources of CP and included soybean meal (SBM), a combination of urea, distillers dried grains (DDG), and fish meal, each provided an equal portion of supplemental CP (UDF), and three levels of urea (17, 33, and 50% of supplemental CP) fed in combination with DDG (U17, U33, and U50). Organic matter and N digestibilities decreased (P less than .05) when lambs were fed U17 compared with those fed SBM. There were no differences (P greater than .05) in bacterial N or AA flows to the duodenum due to CP source despite large differences in ruminal NH3 N concentrations and lower ruminal OM digestion when lambs were fed U17. Duodenal nonbacterial N and AA flows were highest (P less than .05) in lambs fed U17 and UDF and lowest when lambs were fed U50 and SBM. Lysine concentration in duodenal digesta decreased with incremental increases in DDG. In Exp. 2, 30 individually penned ram lambs (33 kg) were allotted to five CP treatments in a randomized complete block design. Treatments were similar to those of Exp. 1, with the exception that U17 was replaced by a 14% CP diet with SBM as the supplemental CP source; all other diets were formulated to contain 12% CP. Lambs fed U50 had decreased (P less than .08) ADG and gain/feed compared with all other treatments, and lambs fed UDF had greater (P less than .05) ADG and gain/feed than lambs fed U33. It was concluded that 17% of the supplemental CP from urea seems adequate to maximize bacterial protein synthesis and that no more than 33% of the supplemental CP should be provided by urea in diets based on AHPWS. Feeding a combination of ruminally resistant protein sources with complementary AA profiles of lysine and methionine (UDF) may enhance quality of protein entering the duodenum and feedlot performance.     

Effects of oscillating dietary protein on ruminal fermentation and site and extent of nutrient digestion in sheep

Eight cannulated wethers (BW = 52.5 +/- 5.7 kg) were used in a replicated 4 x 4 Latin square designed experiment to evaluate the effects of oscillating dietary protein concentrations on ruminal fermentation, site and extent of digestion, and serum metabolite concentrations. Four treatments consisted of a 13, 15, or 17% CP diet fed daily or a regimen in which dietary CP was oscillated between 13 and 17% on a 48-h basis (ACP). All diets consisted of 65% bromegrass hay (10.5% CP, 61.9% NDF, 37.2% ADF) plus 35% corn-based supplement and were formulated to contain the same amount of degradable intake protein (9.6% of DM) plus additional undegradable intake protein (SoyPLUS, West Central Cooperative, Ralston, IA) to accomplish CP levels above 13%. Each of four experimental periods were 16 d in duration with 12 d for diet adaptation followed by 4 d for sample collection. All wethers were fed at 3.0% of initial BW (DM basis) throughout the experiment, resulting in an average organic matter intake of 1.39 kg/d across treatments. When compared to the 15% CP daily treatment, feeding ACP had no effect (P > or = 0.10) on ruminal or lower tract N, NDF, ADF, or OM digestion. True ruminal OM digestion responded quadratically (P = 0.07) to increasing dietary CP, reaching a maximum of 52.0% of OM intake with the 15% CP treatment. Sheep fed ACP tended to have lower (P = 0.08) ruminal NH3 N concentrations and an overall higher (P = 0.0001) molar proportion of acetate compared to those fed 15% CP daily. Total VFA concentrations were not affected (P > or = 0.45) by increasing dietary CP. Microbial efficiency did not differ (P > or = 0.55); thus, bacterial N flow at the duodenum responded quadratically (P = 0.04) to increasing dietary CP. Nonbacterial N (P = 0.001) and total N (P = 0.01) flows at the duodenum and total tract N digestibility (P < or = 0.04) increased linearly as dietary CP increased. Wethers fed ACP maintained a lower (P = 0.002) serum glucose and lower (P = 0.0006) serum urea N compared to those fed 15% CP daily. Because the CP content of the diet was increased at the expense of corn, the response to increased CP observed in this experiment is most likely due to negative associative effects of supplemental starch on ruminal fermentation and microbial growth. Oscillating the CP content of the diet on a 48-h basis has little effect on digestion or N utilization in sheep compared with feeding the same quantity of protein on a daily basis.     

Effects of alkaline hydrogen peroxide treatment of cotton and wheat straw on cellulose crystallinity and on composition and site and extent of disappearance of wheat straw cell wall phenolics and monosaccharides by sheep

Effects of alkaline hydrogen peroxide (AHP) treatment on cellulose crystallinity and cell wall phenolic monomer and monosaccharide composition were measured using cotton and wheat straw (WS). Two WS treatments were used in this study, Type I WS, for which pH is not regulated during AHP treatment, and Type II WS, for which pH is regulated at 11.5 +/- .2 during AHP treatment. Wheat straw had a lower degree of cellulose crystallinity than cotton, but no differences occurred between treated and untreated substrates. Alkali-labile and nitrobenzene-extractable phenolic monomer concentrations were generally lower for Type I and Type II WS compared with untreated WS. Concentrations of glucose were higher and xylose and arabinose lower in Types I and II WS than in untreated WS. Disappearance of alkali-labile phenolic monomers and cell wall monosaccharides by wethers fed diets containing Type I (Exp. 1) or Type II (Exp. 2) AHP-treated WS were determined. Apparent digestibility of glucose and xylose before the duodenum, and of glucose, xylose and arabinose in the total tract, was greatest (P less than .05) when sheep were fed AHP-treated WS diets in both experiments. In Exp. 2, disappearance of alkali-labile phenolic monomers was greatest (P less than .05) before the duodenum and in the total tract when sheep were fed AHP-treated WS diets. Treatment of WS with AHP modified cell wall composition and increased cell wall monosaccharide digestion by sheep.     

Effects of restricted and ad libitum intake of diets containing wheat middlings on site and extent of digestion in steers

A 5 x 5 Latin square design was used to determine the effects of restricted and ad libitum intake of diets containing wheat middlings on the site and extent of digestion compared to ad libitum intake of a corn-based diet and ad libitum intake of chopped alfalfa hay. Five ruminally and duodenally cannulated Angus steers (519 +/- 41.5 kg BW) were used to compare five dietary treatments. The five treatments were as follows: ad libitum access to a corn-based finishing diet (control), the control diet with 25 percentage units of the corn and soybean meal replaced with wheat middlings offered ad libitum (WM), the WM diet restricted to 75% of predicted ad libitum intake (RWM), the RWM diet with wheat middlings replaced with ammoniated wheat middlings (RNWM), and ad libitum access to a chopped alfalfa hay diet. Although RWM steers were fed to consume 75% of ad libitum intake, RWM steers consumed 15.5% less DM than WM. Steers fed ad libitum hay consumed 28.6, 31.7, and 37.2% less (P < 0.01) DM, OM, and nitrogen than RWM steers. No differences in apparent or true ruminal digestibility were observed among steers fed the control vs WM, WM vs RWM, RWM vs RNWM, or RWM vs hay diets. However, the steers fed the hay diet had 32.5, 33.4, and 36.9% lower (P < 0.01) apparent total tract digestibilities of DM, OM, and N than those fed the RWM diet. Average ruminal pH was lower (P < 0.01) for control steers than those fed the WM diet and for those fed RWM compared to the hay diet. The acetate:propionate ratio was higher for cattle fed hay vs the RWM diet. Microbial DM and OM flow to the small intestine was higher (P < 0.02) for steers fed the RWM diet than those fed the hay diet. In addition, bacterial N flow to the small intestine was higher (P < 0.01) for cattle receiving the RWM diet than the hay diet. Feeding diets containing 25 percentage units of wheat middlings at 75% ad libitum intake had no effect on ruminal digestibility.     

Effects of supplemental protein source and alkaline hydrogen peroxide treatment of wheat straw on site of nutrient digestion and flow of nitrogenous compounds to the duodenum of steers.

The objective of this study was to determine the effects of soybean meal (SBM) or spray-dried blood meal (BM) supplementation of diets based on untreated (UNT-WS) or alkaline hydrogen peroxide-treated wheat straw (AHP-WS). A 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments was used. Variables included nutrient digestion and flow to the duodenum. Four Simmental steers (average weight 477 kg) fitted with ruminal and duodenal cannulas were fed 65% UNT-WS or AHP-WS based diets in 12 equal portions daily. Diets were formulated to contain 10% CP. Chromic oxide was used as the digesta flow marker and purines were used as the microbial marker. There were no straw type x protein source interactions. Total tract and ruminal OM digestibility were approximately 25% greater (P < .04) when AHP-WS was fed than when UNT-WS was fed. Source of protein did not affect (P > .10) OM or fiber digestion in the rumen or total tract. Ruminal digestion of NDF and ADF was increased (P < .01) by 51 and 40%, respectively, when AHP-WS was fed than when UNT-WS was fed. Main effect means (P > .10) for N flow to the duodenum as a percentage of N intake were 128.2, 142.5, 133.4, and 137.6 for UNT-WS, AHP-WS, SBM, and BM treatments, respectively. Despite increased (P < .01) ruminal OM digestion for AHP-WS, microbial N flow to the duodenum was greater (P < .01) when UNT-WS was fed than when APH-WS was fed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of alkaline hydrogen peroxide treatment on cell wall composition and digestion kinetics of sugarcane residues and wheat straw.

Our objective was to characterize changes in cell wall composition and digestibility of sugarcane bagasse, pith from bagasse, and wheat straw after treatment with alkaline hydrogen peroxide (AHP). The AHP treatment solution contained 1% H2O2 (wt/vol) maintained at pH 11.5 with NaOH. The H2O2 in solution amounted to 25% of the quantity of substrate treated. After treatment, residues were washed and dried. Detergent fiber composition, total fiber components (neutral sugars, uronic acids, Klason lignin, and noncore lignin phenolic acids), IVDMD, in vitro digestion kinetics of NDF, and monosaccharide digestibilities (24 and 120 h) were determined. Total fiber (TF) and NDF concentrations of all treatment residues were increased (P less than .05) over control substrates by AHP because of greater losses of cell solubles than of cell wall constituents. Hemicellulose:cellulose ratio in NDF of treatment residues was decreased (P less than .05) by AHP for all substrates, but the neutral sugar composition of TF did not agree with this preferential loss of hemicellulose components. Klason lignin, ADL, and esterified noncore lignin, especially ferulic acid, were reduced (P less than .05) by AHP, whereas etherified noncore lignin composition was unchanged. Treatment increased (P less than .05) IVDMD, extent of NDF digestion, and monosaccharide digestibilities of all crop residues. The rate of NDF digestion was increased (P less than .05) for the sugarcane residues but not for wheat straw. Alkaline hydrogen peroxide improved crop residue digestibility, probably as a result of the removal of core and noncore lignin fractions.     

Site and extent of apparent magnesium absorption by lambs fed different sources of magnesium

Ten abomasally cannulated crossbred wether lambs (avg wt, 33 kg) were used in a replicated 5 x 5 latin square design to determine the site and extent of apparent absorption of Mg when fed different sources of Mg. Lambs were fed twice daily 220 g of chopped mixed grass hay and 180 g of a corn-based supplement (control; .13% mg, DM basis), or the control diet supplemented with Mg (.26% Mg, DM basis) from MgO, magnesium citrate (MgC), smectite-vermiculite (Mg-Mica) or MgOH. Lambs were maintained in metabolism stalls during each of the five experimental periods. Each period consisted of a 7-d dietary adjustment followed by a 3-d collection of abomasal samples, feces and urine. Abomasal contents were sampled four times daily during the 3-d collection period. The diet contained .5% chromium oxide as a digestion marker. Apparent absorption of Mg was .17, .55, .85, .78 and .82 g/d for lambs fed the control, MgO, MgC, Mg-Mica and MgOH diets, respectively. Apparent absorption of Mg (g/d) was similar (P greater than .05) in the lambs fed the supplemented diets and greater (P less than .05) than in those fed the control diet. Preintestinal absorption of Mg was .21, .57, 1.08, .14 and .92 g/d when the control, MgO, MgC, Mg-Mica and MgOH diets were fed. Lambs fed the control and Mg-Mica diets absorbed similar (P greater than .05) quantities of Mg in the preintestinal region and less (P less than .05) than lambs fed the MgO, MgC and MgOH diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic and endocrine responses of lambs fed Acremonium coenophialum-infected or noninfected tall fescue hay at equivalent nutrient intake

Ten Hampshire x Western wether lambs (means weight = 30.1 kg) equipped with ruminal and abomasal cannulas were fed either low-Acremonium coenophialum (AC) Kentucky-31 (less than 1% infected) or high-AC G1-307 (greater than 95% infected) varieties of tall-fescue (TF) hay of similar nutrient composition in a completely randomized design. Lambs were housed in metabolism crates at 21 +/- 1 degrees C and fed 552 g DM/d of ground hay at 0800 and 2000. A 10-d adaptation preceded 7 d of sample collection. Levels of water and DM voluntarily consumed by the low-AC group during the adjustment period were held constant for both treatment groups throughout the collection period by intraruminal insertion of unconsumed DM and water. Fixed water intake markedly reduced voluntary water intake but it alleviated previous depressions in voluntary DM intake in lambs fed high-AC. Mean daily respiration and heart rates, rectal temperature and hematocrit were not affected (P greater than .10) by treatment. Compared with high-AC, lambs fed low-AC retained a greater (P less than .10) amount of N (1.8 vs 1.1 g/d) and a greater (P less than .10) percentage of their N intake (16.4 vs 9.9%). Abomasal total and bacterial N flow and ruminal digestion of cell wall components were not affected (P greater than .10) by treatment. Total tract digestion of DM, NDF and ADF was lower (P less than .01) for high- than for low-AC. Serum prolactin concentration was higher (P less than .10) for lambs fed low- than for those fed high-AC TF, but serum cortisol and thyroxine concentrations were not affected (P greater than .10) by treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

日粮中添加亚麻籽对肉羊消化代谢的影响

16只体重相近,均值为(34.06±1.68)kg的杂交公羔羊按单因素随机设计原理被分成4组,每组4只,日粮中添加0%,5%,10%,15%亚麻籽进行消化代谢试验,研究不同水平的亚麻籽对绵羊消化代谢的影响。结果表明:随着亚麻籽添加水平的提高,干物质的采食量表现下降的趋势,但干物质的表观消化率各组间没有差异(P>0.05);亚麻籽的含量与可消化氮和沉积氮呈现负相关趋势,氮的表观消化率各组间差异显著(P<0.05),呈现逐渐递减的现象;有机物的表观消化率变化幅度不大,前3组差异不显著(P>0.05),添加15%亚麻籽的Ⅳ组与其他组比较差异显著;粗脂肪的表观消化率与亚麻籽的添加水平呈正相关,且各组间表现显著;纤维类物质中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)随着亚麻籽添加水平的增加而表现大幅度的下降,各组间差异显著(P<0.05)。     

Effects of roughage particle size on site of nutrient digestion and digesta flow through the gastrointestinal tract of sheep fed corncob-concentrate diets

An experiment examining nutritional effects of dietary corncob particle size was conducted using ruminal-, duodenal- and ileal-cannulated sheep in a 4 X 4 Latin square design. Site of nutrient digestion and digesta flow were the principal criteria evaluated. Analyses of dry matter (DM), N, starch and neutral detergent fiber (NDF) were performed on feed, feces and digesta samples. Chromic oxide-impregnated paper was used as an external marker to estimate digestibilities at different sites along the gastrointestinal tract. Ruminal pH and volatile fatty acid molar proportions were also determined. All diets (74.9% concentrates: 25.1% corncobs) were pelleted and were similar in ingredient composition but varied in corncob particle size (corncob mean particle sizes were 6.5, 5.4, 1.4 or .8 mm). Dietary crude protein levels differed little among treatments. Starch concentration was higher in diets containing the larger corncob particles while NDF, acid detergent fiber (ADF), cellulose and hemicellulose concentrations were lower in diets containing larger particles, suggesting a reaction between starch and fiber moieties during the pelleting process. Starch flow past the duodenum decreased (P less than .05) as dietary corncob particle size decreased. Apparent NDF digestion before the duodenum was highest for sheep fed diets containing 1.4-mm corncobs (P less than .05). Apparent starch digestion in the small intestine decreased (P less than .05) as dietary corncob particle size decreased. A considerable amount of NDF was apparently digested in the small intestine of sheep consuming diets containing 5.4- and .8-mm corncobs. Likewise, a substantial amount of NDF was apparently digested in the large intestine. Few differences in apparent total tract digestibilities were noted.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of Bermudagrass hay and soybean hulls inclusion on performance of sheep fed cactus-based diets

The objective of this experiment was to determine the effects of replacing corn with soybean hulls (SH) or Bermudagrass tifton hay (TH) on performance of sheep fed cactus-based diets. Three ruminally fistulated sheep were used in a 3 × 3 Latin square experiment with 21-day periods. All diets contained 75% spineless cactus (dry matter basis, DM) and formulated to be isonitrogenous. Fiber source had no influence on nutrient intakes except for the intake of neutral detergent fiber (NDF) which was lower (p < 0.05) for animals fed corn relative to those fed SH or TH. Time expended in rumination and total chewing time were higher (p < 0.05) for animals fed TH than those fed SH or corn. In vivo nutrient digestibilities were similar for all dietary treatments and averaged 69.6%, 74.8%, 69.9%, and 61.8% for DM, organic matter, crude protein, and NDF, respectively. Feeding SH relative to TH and corn decreased ruminal pH (p < 0.05) and increased concentration of total volatile fatty acids (p < 0.05). However, ruminal NH₃–N concentration was higher (p < 0.05) for animal fed TH than for those fed SH or corn. Abdominal distension and ruminal biofilm production were greater (p < 0.05) in animals fed corn or SH than in those fed TH. It was concluded that replacing corn with SH or TH up to 15% of the diet DM in a cactus-based diet had no effect on nutrient intakes or total tract nutrient utilization. Changes in ruminal fermentation parameters reflected differences in ruminal degradability between the two fiber sources. Bermudagrass tifton hay was more effective than SH in reducing the risk of bloat associated with feeding high levels of spineless cactus to ruminants.     

Nutrient intake and digestion as influenced by wash water solids as a protein source for lambs fed orchardgrass hay

Two experiments were conducted with sheep fed orchardgrass hay plus one of four supplements to evaluate use of a cheese processing wash water solid (WWS) material as a protein supplement. In both trials, lambs were fed either a cornstarch control (0% WWS-N) or a protein supplement containing 25, 50 or 75% N from WWS (25, 50 or 75% WWS-N, respectively). The majority of the remaining protein was supplied by soybean meal (SBM). Trial 1 was a replicated 4 x 4 extra-period Latin square. Protein supplementation increased total tract NDF and N digestibilities (P less than .10) 13% and 29%, respectively, compared with the cornstarch control. Total tract N digestibility was depressed (P less than .10) when 75% WWS-N (71.5%) vs 25 or 50% WWS-N (75.9 and 75.9%, respectively) was fed. Total VFA were depressed (P less than .10) 6 and 9 h postfeeding in sheep fed 75% WWS-N compared with the control (78.3 and 74.6 mM vs 98.8 and 94.6 mM for 6 and 9 h, respectively). Two hours postfeeding, lambs fed control had lower (P less than .10) ruminal pH compared with lambs fed 25, 50 and 75% WWS-N (6.2 vs 6.4, 6.5 and 6.5, respectively). Ruminal ammonia concentrations were 5 to 10 mg/dl lower (P less than .10) at all times in control lambs. In Trial 2, a metabolism study, feeding 75% WWS-N resulted in lower N digestibility (P less than .10) than did feeding 25% and 50% WWS-N (47.2 vs 56.4 and 55.2%, respectively). Data suggest that up to 50% of the SBM-N in a protein supplement for wethers may be replaced by WWS-N without adversely altering nutrient digestibility, ruminal fermentation or N metabolism.     

The delivery of cottonseed meal at three different time intervals to steers fed low-quality grass hay: effects on digestion and performance

A ruminal fermentation trial and a steer growth trial were conducted to evaluate the effects of time interval of cottonseed meal (CSM) supplementation of predominantly meadow fescue grass hay (GH; CP = 6.6%) on nutrient digestion and growth performance of beef steers. The fermentation trial used four ruminally cannulated steers assigned to a 4 x 4 latin square design with dietary treatments of GH fed alone (C) or GH supplemented with 3 g CP/kg BW.75 daily as supplied by CSM every 12, 24 or 48 h. Nylon bags containing GH were inserted into the rumen on d 1 and 2 of each collection period and incubated for 12, 24, 48 and 96 h to measure NDF and ADF degradation. Subsequently, steers were fed Yb-labeled GH and fecal samples were collected to determine particulate passage rate (PR). Dry matter and NDF intake, mean NDF and ADF in situ disappearance and ruminal VFA concentrations were greater (P less than .05) when CSM was fed; however, the delivery of CSM at various times did not affect (P greater than .10) these variables. Supplemented diets tended (P = .08) to have faster PR compared with the C diet. In the growth trial, CSM supplemented steers consumed more digestible DM (P less than .05) and had greater (P less than .05) daily gain compared with C steers. Effects due to time of CSM supplementation were not observed for the variables measured in the present study.