Total Tract Digestibility Of DM Research Articles

Development and Validation of Equations for Predicting the Metabolizable Energy Value of Double-Low Rapeseed Cake for Growing Pigs.

Simple SummaryDouble-low rapeseed cake could be a cost-effective feed resource for swine, providing amino acids and energy. Accurate evaluation of the energy values of different double-low rapeseed cakes is of great significance to economically and effectively formulate diets when double-low rapeseed cakes are used as an alternative ingredient in diets fed to pigs. Therefore, two experiments were conducted to develop and validate an equation to predict the metabolizable energy of double-low rapeseed cake for growing pigs based on chemical compositions. Results indicated that the best-fit prediction equation for metabolizable energy (MJ/kg) was 9.33 − 0.09 × neutral detergent fiber −0.25 × crude fiber + 0.59 × gross energy (R2 = 0.93). Increasing levels of double-low rapeseed cake linearly reduced apparent total tract digestibility of nutrients, but did not affect growing performance and caloric efficiency of metabolizable energy of growing pigs fed diets balanced for standardized ileal digestibility Lys/metabolizable energy ratio. The best-fit prediction equation in this experiment can be used to accurately estimate the metabolizable energy value of double-low rapeseed cake fed to growing pigs under practical conditions.The study was conducted to develop and validate an equation to predict the metabolizable energy (ME) of double-low rapeseed cakes (DLRSC) for growing pigs based on their chemical compositions. In Experiment 1, 66 growing pigs (initial body weight 36.6 ± 4.1 kg) were allotted randomly to a completely randomized design with 11 diets. The diets included a corn–soybean meal basal diet and 10 test diets containing 19.22% DLRSC supplemented at the expense of corn, soybean meal, and lysine. Neutral detergent fiber (NDF), crude fiber (CF), and gross energy (GE) were the best predictors to determine ME. The best-fit prediction equation of ME (MJ/kg) was ME = 9.33 − 0.09 × NDF − 0.25 × CF + 0.59 × GE (R2 = 0.93). In Experiment 2, a total of 144 growing pigs (initial body weight 29.7 ± 2.7 kg), with six pigs per pen and six pens per treatment, were assigned randomly to four treatments in a completely randomized block design for a 28-day feeding trial. A corn–soybean meal basal diet was prepared, and three additional diets were formulated by adding 7%, 14%, and 21% DLRSC to the basal diet at the expense of soybean meal. All diets were formulated to provide equal standardized ileal digestibility (SID) Lys/ME ratio and SID essential amino acids/SID Lys ratio. Increasing dietary levels of DLRSC had no effect on average daily feed intake, average daily gain, and feed-to-gain ratio. The caloric efficiency of ME (31.83, 32.44, 31.95, and 32.69 MJ/kg, respectively) was not changed by increasing the dietary concentration of DLRSC. Increasing dietary levels of DLRSC linearly reduced (p < 0.05) the concentrations of triiodothyronine and tetraiodothyronine in serum, as well as apparent total tract digestibility of DM, GE, crude protein, acid detergent fiber, and organic matter of the diet. In conclusion, the ME prediction equation obtained in Experiment 1 accurately estimates the ME value of DLRSC fed to growing pigs.

Nutritive value of sorghum silage for sheep.

This study compared ensiled sorghum (ES) from two varieties (first and second cuts) with corn silage (CS) for chemical analysis, total-tract nutrient digestibility, ruminal variables and blood biochemistry metabolites in sheep. Five experimental silages representing first cut ES var. Pegah (PS1), second cut ES var. Pegah (PS2), first cut ES var. Speedfeed (SS1), second cut ES var. Speedfeed (SS2) and CS were assessed for chemical analysis, silage fermentation and anti-quality compounds. Diets consisted of lucerne hay, silage and a premix (at the ratio of 53.5:46:0.5 on a dry matter [DM] basis). Feed consumption, total-tract nutrient digestibility, microbial nitrogen supply (MNS), ruminal variables and blood biochemistry metabolites were determined in a Latin square design of five periods with five male sheep. Compared to sorghum, CS had lower (p<0.01) concentrations of ash, water-soluble carbohydrates and crude protein, but higher starch, lignin (sa), non-structural carbohydrates and apparent nutrient digestibility. The measurements of pH, lactic acid, NH3 -N and volatile fatty acids (VFA) confirmed that all silages were well-preserved. The anti-quality compound levels in the silages were below the safe limits for ruminants. No differences were observed in feed consumption (p>0.05) and total-tract digestibility of DM and nutrients (p>0.05). Rumen pH, NH3 -N, VFA concentrations and acetate to propionate ratio showed no difference among treatments (p>0.05). Sheep fed on sorghum silage showed a decrease (p<0.01) in total protozoa, and particularly in the Entodiniae population. There were no differences in cellulolytic bacteria counts (p>0.05) among treatments. Urinary N, MNS and blood biochemistry metabolites showed no difference among treatments (p>0.05). Silages from both cuts of sorghum had comparable total-tract nutrient digestibility to CS, therefore, these varieties could be used as a more drought resilient silage source in the feeding of sheep.

Effects of ractopamine hydrochloride on nutrient digestibility and nitrogen excretion of finishing beef cattle.

The objective was to quantify the effects of the beta-adrenergic agonist (β-AA) ractopamine hydrochloride (Actogain, Zoetis, Parsippany, NJ) on nitrogen excretion and nutrient digestibility in feedlot cattle. In experiment 1, 12 Simmental × Angus steers were blocked by bodyweight (531 ± 16 kg) and used in a randomized complete block design. Dietary treatments included: 1) a control without β-AA (CON) or 2) 400 mg/steer/d ractopamine hydrochloride (RAC) for 35 d before slaughter. Diets contained (DM basis) 55% dry-rolled corn, 20% corn silage, 15% modified wet distillers grains with soluble, and 10% supplement. For each block, total collection of feed, orts, feces, and urine were conducted for two 5 d sampling periods during week 2 and 4 of RAC supplementation. No interaction (P > 0.21) between treatment and collection period was observed for any parameter evaluated. Dietary treatment had no effect (P = 0.51) on DMI, but RAC had decreased fecal DM output (P = 0.04) compared with CON. Thus, RAC had greater apparent total tract DM digestibility (77.2 vs. 73.5%; P < 0.01), N digestibility (72.4 vs. 69.4%; P = 0.01), and NDF digestibility (65.6 vs. 60.2%; P < 0.01) than CON. Although treatment did not affect nitrogen intake (P = 0.52), RAC tended to reduce total nitrogen excretion (113.3 vs. 126.7 g/d; P = 0.10) compared with CON due to a tendency for decreased fecal nitrogen output (53.9 vs. 61.3 g/d; P = 0.10). However, dietary treatment had no effect (P = 0.53) on urinary nitrogen output or percentage of urinary nitrogen excreted as urea (P = 0.28). Experiment 2 was an in vitro experiment conducted to validate the effects of RAC on nutrient digestibility using Simmental × Angus heifers (451 ± 50 kg). Rumen fluid was collected individually by stomach tube from CON- (n = 9) and RAC-fed (n = 10) heifers to inoculate bottles containing a CON or RAC-containing substrate in a split–plot design. No interaction between rumen fluid source and in vitro substrate was observed. Greater IVDMD (P = 0.01) was observed in rumen fluid from RAC-fed heifers compared with rumen fluid from CON-fed heifers. The inclusion of RAC in the in vitro substrate increased IVDMD (P < 0.01). Overall, feeding RAC increased microbial digestion of the dry-rolled corn-based finishing diet to increase total tract dry mater digestion by 5% and reduce nitrogen excretion by 10.6% in the 35 d period prior to slaughter.

Effects of riboflavin supplementation on performance, nutrient digestion, rumen microbiota composition and activities of Holstein bulls

To investigate the influences of dietary riboflavin (RF) addition on nutrient digestion and rumen fermentation, eight rumen cannulated Holstein bulls were randomly allocated into four treatments in a repeated 4 × 4 Latin square design. Daily addition level of RF for each bull in control, low-RF, medium-RF and high-RF was 0, 300, 600 and 900 mg, respectively. Increasing the addition level of RF, dry matter (DM) intake was not affected, average daily gain tended to be increased linearly and feed conversion ratio decreased linearly. Total-tract digestibilities of DM, organic matter, crude protein (CP) and neutral detergent fibre (NDF) increased linearly. Rumen pH decreased quadratically and total volatile fatty acids (VFA) increased quadratically. Acetate molar percentage and acetate to propionate ratio increased linearly, but propionate molar percentage and ammonia-N content decreased linearly. Rumen effective degradability of DM increased linearly, NDF increased quadratically but CP was unaltered. Activity of cellulase and populations of total bacteria, protozoa, fungi, dominant cellulolytic bacteria, Prevotella ruminicola and Ruminobacter amylophilus increased linearly. Linear increase was observed for urinary total purine derivatives excretion. The data suggested that dietary RF addition was essential for rumen microbial growth, and no further increase in performance and rumen total VFA concentration were observed when increasing RF level from 600 to 900 mg/d in dairy bulls.

Graded dietary resistant starch concentrations on apparent total tract macronutrient digestibility and fecal fermentative end products and microbial populations of healthy adult dogs.

Resistant starch (RS) is fermentable by gut microbiota and effectively modulates fecal short-chain fatty acid concentrations in pigs, mice, and humans. RS may have similar beneficial effects on the canine gut but has not been well studied. The objective of this study was to evaluate the effects of 0%, 1%, 2%, 3%, and 4% dietary RS (Hi-maize 260) on apparent total tract macronutrient digestibility, fecal characteristics, fermentative end-product concentrations, and microbiota of healthy adult dogs. An incomplete 5 × 5 Latin square design with seven dogs and five experimental periods was used, with each treatment period lasting 21 d (days 0 to 17 adaptation; days 18 to 21 fresh and total fecal collection) and each dog serving as its own control. Seven dogs (mean age = 5.3 yr; mean body weight = 20 kg) were randomly allotted to one of five treatments formulated to be iso-energetic and consisting of graded amounts of 100% amylopectin cornstarch, RS, and cellulose and fed as a top dressing on the food each day. All dogs were fed the same amount of a basal diet throughout the study, and fresh water was offered ad libitum. The basal diet contained 6.25% RS (dry matter [DM] basis), contributing approximately 18.3 g of RS/d based on their daily food intake (292.5 g DM/d). Data were evaluated for linear and quadratic effects using SAS. The treatments included 0%, 1%, 2%, 3%, and 4% of an additional RS source. Because Hi-maize 260 is approximately 40% digestible and 60% indigestible starch, the dogs received the following amounts of RS daily: 0% = 18.3 g (18.3 + 0 g), 1% = 20.1 g (18.3 + 1.8 g), 2% = 21.9 g (18.3 + 3.6 g), 3% = 23.7 g (18.3 + 5.4 g), and 4% = 25.5 g (18.3 + 7.2 g). Apparent total tract DM, organic matter, crude protein, fat, and gross energy digestibilities and fecal pH were linearly decreased (P < 0.05) with increased RS consumption. Fecal output was linearly increased (P < 0.05) with increased RS consumption. Fecal scores and fecal fermentative end-product concentrations were not affected by RS consumption. Although most of the fecal microbial taxa were not altered, Faecalibacterium were increased (P < 0.05) with increased RS consumption. The decrease in fecal pH and increase in fecal Faecalibacterium would be viewed as being beneficial to gastrointestinal health. Although our results seem to indicate that RS is poorly and/or slowly fermentable in dogs, the lack of observed change may have been due to the rather high level of RS contained in the basal diet.

Effects of a blend of mannan and glucan on growth performance, apparent nutrient digestibility, energy status, and whole-blood immune gene expression of beef steers during a 42-d receiving period.

We examined the effects of dietary supplementation of a blend of mannan and glucan on the growth performance, energy status, and whole-blood immune gene expression of newly weaned beef steers during a 42-d receiving period. Forty-eight newly weaned Angus crossbred steers (2-d post-weaning; 199 ± 13 kg of initial body weight [BW]) from a single source were stratified by BW and randomly assigned to one of the two treatments: basal diet with no additive (CON; n = 24) or a basal diet top-dressed with 5 g of a blend of mannan and glucan (MANGLU; n = 24). Average daily gain (ADG) and feed efficiency (FE) from days 1 to 14, 15 to 42, and 1 to 42 were calculated from daily dry matter intake (DMI) and weekly BW. Blood samples were collected on days 0, 14, and 42 for measurement of plasma glucose and nonesterified fatty acids (NEFA). Blood samples collected on days 14 and 42 were composited for each steer for untargeted carbonyl-metabolome analysis (measurement of carbonyl-containing metabolites). Expression of 84 immune-related genes was analyzed on blood samples collected on day 42. Beginning on days 37 to 42, total mixed ration, refusals, and fecal samples were collected once daily to determine apparent total tract digestibility of DM, CP, NDF, and ADF using indigestible NDF as an internal marker. Over the 42-d feeding trial, supplemental MANGLU tended to increase final BW (P = 0.07) and ADG (P = 0.06). Compared to CON, beef steers fed supplemental MANGLU had greater (P = 0.01) DMI during the first 14 d, greater DM digestibility (P = 0.03), and tended to have greater NDF digestibility (P = 0.09). No treatment effects (P > 0.10) on plasma glucose and NEFA on days 14 and 42 were detected; however, carbonyl-metabolome analysis revealed increased (FDR ≤ 0.05) plasma concentrations of galactose and glyceraldehydes, and altered (FDR ≤ 0.05) concentrations of some microbiome-derived metabolites in beef steers fed MANGLU. Compared with CON, MANGLU increased (P ≤ 0.05) the expression of five immune-related genes involved in recognition of and mounting immune defense against microbial pathogens. In conclusion, the results of this study demonstrated that supplemental MANGLU enhances beef cattle immunocompetence and productivity during feedlot receiving period.

PSII-17 Program Chair Poster Pick: Effect of ruminal protozoa on methane emissions in ruminants – a meta-analysis

Abstract The effects of ruminal protozoa (RP) concentration on methane emissions from ruminants were evaluated in a meta-analysis using 67 publications reporting data from 85 in vivo experiments. Experiments included in the database reported methane emissions (g/kg DMI) and RP (log10 cells/mL) from the same group of animals. Quantitative data including diet chemical composition, ruminal fermentation, total tract digestibility, and milk production; and qualitative information including methane mitigation strategies, animal type, and methane measurement methods were also collected. The studies were conducted in dairy cows (51%), beef steers (32%) and small ruminants (32%). 70% of the studies reported a reduction in methane emissions. Supplemental lipids reduced methane emissions 95% of the time. The relationship between methane emissions and RP concentration was evaluated as a random coefficient model with the experiment as a random effect and weighted by the inverse pooled SEM squared, including the possibility of covariance between the slope and the intercept. A quadratic effect of RP concentration on methane emissions was detected: CH4= -28.8 + 12.2 × RP-0.64 × RP2. To detect potential interfering factors in the relationship, the influence of several qualitative and quantitative factors were separately tested. Acetate, butyrate, and isobutyrate molar proportions had positive relationships with methane emissions and influenced the relationship between RP concentration and methane emissions, where the presence of ruminal fermentation variables reduced the effects of RP concentration in methane emissions. Total tract digestibility of DM, OM, and CP had negative relationships while NDF digestibility had a positive relationship with methane emissions; however, they only changed the magnitude of intercept and slope of RP and RP2 for the relationship. For dairy cows, milk fat and protein concentrations had positive relationships and milk yield had a negative relationship with methane emissions and changed the magnitude of intercept and slope of RP and RP2 for the relationship.

Impact of substituting compound feed with increasing levels of fresh grass-clover on nitrogen metabolism and plasma metabolites of sows

The purpose of this study was to identify biomarkers for fresh grass-clover intake and determine the digestibility and energy value of fresh grass to estimate voluntary fresh grass-clover intake in sows kept on pasture according to organic production practice. A total of sixteen multiparous dry sows (Danish Landrace x Danish Yorkshire) were housed in metabolism cages for 2 periods of 5 d. To study dietary effects, sows were fed one of four mixed treatments where increasing proportions of a basal commercial organic sow compound feed was partly replaced with 0, 2, 4, or 6 kg fresh grass-clover collected 3 wk after the previous cut. Sows were fed similar amounts of metabolizable energy (ME). Total collection of urine and feces was performed on a daily basis for 5d, and blood samples were collected from the jugular vein on the last day of feeding. Plasma metabolites were analyzed using a non-targeted liquid chromatography-mass spectrometry (LCMS) approach. Analyzed plasma metabolites (area under the curve in arbitrary units from the LCMS) were screened for correlation with grass intake. Data on nutrient digestibility and plasma metabolites were analyzed using a MIXED procedure while accounting for repeated measurements. Apparent total tract digestibilities of dry matter, organic matter, nitrogen, and energy of fresh grass-clover were 72, 64, 71, and 68%, respectively, using the regression method. The N intake increased linearly with increasing fresh grass-clover intake (P < 0.001). There was no evidence of altered N deposition and N utilization in response to increasing grass intake (P > 0.05). There was a linear increase in plasma urea content (2.64 to 4.39 mM) when grass intake increased from 0 to 6 kg/d (P = 0.02). Plasma glucose, lactate, creatinine and NEFA, and triglycerides were not affected by increased grass-clover intake. The daily ME contribution from fresh grass-clover (MJ/d) was found to be highly positively correlated with plasma pipecolic acid (Y = 0.0289 X; r2 = 0.91; P < 0.001) and a metabolite tentatively identified as plasma bisnorbiotin (Y = 0.482 X; r2 = 0.92; P < 0.001). In conclusion, fresh grass-clover intake of sows was highly correlated with plasma pipecolic acid and plasma bisnorbiotin concentration and apparent total tract digestibility of DM, OM, N, and energy estimated for 100% fresh grass-clover intake in dry sows was 64 to 72% using the regression method.

Evaluation of Diets with Inclusion of Hydrothermal, Phytase, and Organic Acid Pretreated Canola Meal on Nutrient Digestibility in Swine

The objective of this study was to evaluate the effects of dietary inclusion of hydrothermal, phytase, and organic acid pretreated canola meal (CM) on nutrient digestibility in swine. A basal diet barley, wheat, and CM based, was formulated. Four diets containing 30% hydrothermal pretreated CM with 50% moisture and 40&amp;deg;C, phytase (1000 FTU/kg activity), and either citric acid (CA), malic acid (MA), or lactic acid (LA), and a control containing pretreated CM without phytase or organic acid were fed to 12 ileal-cannulated finisher pigs (initial average BW 105.3 &amp;plusmn; 2.7 kg) in a completely randomized design over two periods of 9 days per period. Nutrient composition and phytate content of the diets, ileal digesta, and feces were analyzed and apparent ileal and total tract digestibilities were determined. The inclusion of hydrothermal, phytase, and CA or MA pretreated CM in the diet decreased phytate P (by up to 38.6%) (p &amp;lt; 0.05), consequently increasing available P (by up to 55.6%). Apparent ileal digestibility (AID) was improved for P by 19.9 ‒ 35.1% units and apparent total tract digestibility of DM by 10.3 ‒ 14.8% units, of protein by 6.6 ‒ 12.1% units, and of gross energy by 12 ‒ 17% units across the treatments (p &amp;lt; 0.05), while AID of CP for MA treatment was up by 4.7% units (p &amp;lt; 0.05) relative to the control, indicating improved diet utilization, thus reduced excretion to the environment.

Branched-chain volatile fatty acids and folic acid accelerated the growth of Holstein dairy calves by stimulating nutrient digestion and rumen metabolism

The combined addition of branched-chain volatile fatty acids (BCVFAs) and folic acid (FA) could improve growth performance and nutrient utilization by stimulating ruminal microbial growth and enzyme activity. This study was conducted to evaluate the effects of BCVFA and FA addition on growth performance, ruminal fermentation, nutrient digestibility, microbial enzyme activity, microflora and excretion of urinary purine derivatives (PDs) in calves. Thirty-six Chinese Holstein weaned calves (60 ± 5.4 days of age and 107 ± 4.7 kg of BW) were assigned to one of four groups in a randomized block design. Treatments were control (without additives), FA (with 10 mg FA/kg dietary DM), BCVFA (with 5 g BCVFA/kg dietary DM) and the combined addition of FA and BCVFA (10 mg/kg DM of FA and 5 g/kg DM of BCVFA). Supplements were hand-mixed into the top one-third of total mixed ration. Dietary concentrate to maize silage ratio was 50 : 50 on a DM basis. Dietary BCVFA or FA addition did not affect dry matter intake but increased average daily gain (ADG) and feed conversion efficiency. Ruminal pH and ammonia N were lower, and total volatile fatty acids (VFAs) concentration was higher for BCVFA or FA addition than for control. Dietary BCVFA or FA addition did not affect acetate proportion but decreased propionate proportion and increased acetate to propionate ratio. Total tract digestibility of DM, organic matter, CP and NDF was higher for BCVFA or FA addition than for control. Dietary BCVFA or FA addition increased activity of carboxymethyl cellulase and cellobiase, population of total bacteria, fungi, Ruminococcus albus, R. flavefaciens, Fibrobacter succinogenes and Prevotella ruminicola as well as total PD excretion. Ruminal xylanase, pectinase and protease activity and Butyrivibrio fibrisolvens population were increased by BCVFA addition, whereas population of protozoa and methanogens was increased by FA addition. The BCVFA × FA interaction was significant for acetate to propionate ratio, cellobiase activity and total PD excretion, and these variables increased more with FA addition in diet without BCVFA than in diet with BCVFA. The data indicated that supplementation with BCVFA or FA increased ADG, nutrient digestibility, ruminal total VFA concentration and microbial protein synthesis by stimulating ruminal microbial growth and enzyme activity in calves.

PSXII-23 Effects of a recombinant fibrolytic enzyme on fiber digestion, ruminal fermentation, nitrogen balance and total tract digestibility of heifers fed a high forage diet

Abstract The objective of this study was to investigate the effects of a recombinant fibrolytic enzyme (RFE; xylanase XYL10C) on ruminal pH and fermentation characteristics, total tract digestibility and nitrogen balance in beef heifers. The experiment was a cross-over design with two treatments and two periods, using eight ruminal cannulated beef heifers. The treatments were a basal diet containing 60% barley silage, 30% barley straw and 10% supplement (DM basis) without (control) or with RFE. The RFE XYL10C was selected specifically for ruminants using a high throughput in vitro micro assay and was sprayed onto the barley straw at a rate of 6.6 × 104 IU/kg DM 24 h before feeding. The diet was prepared daily using a data ranger. Each period was 21 d, with a 14-d adaptation and 7-d sample collection period. The digestibility and nitrogen balance were measured by total fecal and urine collection. Data were analyzed using the PROC MIXED procedure of SAS with fixed effects of treatment, and random effects of period and heifer. Feed intake (8.9 kg/d) and total tract digestibility of DM (65.5%), NDF (57.2%) and ADF (51.2%) were not affected by RFE. Ruminal pH including mean (6.52), minimum (5.79), maximum (7.05), and duration of pH &amp;lt; 5.8 (0.64, h/d) did not differ between treatments. No treatment effects were observed for total VFA concentration (106 mM), molar proportion of acetate (68.2%) and propionate (17.5%) and acetate to propionate ratio (3.94). However, adding RFE vs. control tended (P &amp;lt; 0.08) to increase ruminal NH3-N concentration (5.75 vs. 5.23 mM) and endoglucanase activity (44.3 vs. 40.7 µmol glucose/min/mL wet rumen contents). There were no differences in nitrogen utilization and rumen microbial protein synthesis (90.7 g/d) between treatments. The results indicate that RFE XYL10C did not improve fiber digestion in heifers fed a high forage diet.

Circadian misalignment imposed by nocturnal feeding tends to increase fat deposition in pigs.

Misalignment of day/night and feeding rhythms has been shown to increase fat deposition and the risk for metabolic disorders in humans and rodents. In most studies, however, food intake and intake patterns are not controlled. We studied the effects of circadian misalignment on energy expenditure in pigs while controlling for food intake as well as intake patterns. Twelve groups of five male pigs were housed in respiration chambers and fed either during the day (10.00-18.00 hours; DF) or night (22.00-06.00 hours; NF), bihourly the same sequential meals, representing 15, 10, 25, 30 and 20 % of the daily allowance. Paired feeding was applied to ensure equal gross energy intake between treatments. Apparent total tract digestibility, energy balances and heat partitioning were measured and analysed using a mixed linear model. Apparent total tract energy and DM digestibility tended to be lower for NF-pigs than DF-pigs (P < 0·10). Heat production was 3 % lower for NF-pigs than DF-pigs (P < 0·026), increasing fat retention by 7 % in NF-pigs (P = 0·050). NF-pigs were less active than DF-pigs during the feeding period, but more active during the fasting period. RMR was greater for DF-pigs than NF-pigs during the fasting period. Methane production was 30 % greater in NF-pigs than DF-pigs (P < 0·001). In conclusion, circadian misalignment has little effect on nutrient digestion, but alters nutrient partitioning, ultimately increasing fat deposition. The causality of the association between circadian misalignment and methane production rates remains to be investigated.

Effects of inoculation of corn silage with Lactobacillus spp. or Saccharomyces cerevisiae alone or in combination on silage fermentation characteristics, nutrient digestibility, and growth performance of growing beef cattle.

This study evaluated the effects of a novel silage inoculant containing Saccharomyces cerevisiae strain 3 as a direct fed microbial (DFM) on the ensiling, aerobic stability, and nutrient digestibility of whole-crop corn silage and growth performance of beef cattle. Treatments included uninoculated corn silage (CON) or corn silage inoculated with a mixture of 1.1 × 105 cfu g-1 fresh forage Lactobacillus plantarum and Lactobacillus buchneri (INOC1) or 1.0 × 104 cfu g-1 fresh forage S. cerevisiae strain 3 (INOC2) or a mixture of INOC1 and INOC2 (INOC3). Silage in INOC1 had lower (P = 0.03) proportion of lactate, with acetate (Ac) proportion ranking as INOC1 > INOC3 > INOC2 (P < 0.01). In terminal silage, numbers of lactic acid bacteria were greater (P = 0.05) for INOC1 than CON and INOC2, while yeast counts tended (P = 0.08) to be greater for INOC2 than INOC3 on day 3 of aerobic exposure. Aerobic stability of corn silage was not impacted by inoculation with S. cerevisiae strain 3. Heifers fed INOC2 and INOC3 had lower (P < 0.01) ruminal Ac concentration than those fed CON. Apparent total tract digestibilities of DM, OM, ADF, and NDF were greater (P ≤ 0.03) for heifers fed INOC2 than those fed CON. Growth performance was similar across treatments, excepting DMI as percent of BW tended to be lower (P = 0.08) for INOC2 steers compared to CON steers. These results suggest that S. cerevisiae strain 3 has potential as a component in a fourth generation DFM silage inoculant.

Elevated concentrations of crude glycerin in diets for beef cattle: feedlot performance, carcass traits, and ruminal metabolism1.

Three experiments were conducted to evaluate the inclusion of crude glycerin (CG) in diets for beef cattle. In Exp. 1, 4 ruminally cannulated steers were fed diets with 0 or 15% CG (DM basis), to evaluate DM disappearance, VFA profiles, and gas production. There was a tendency for an interaction (P = 0.06) between diet fed to donor animals and substrate fed to in vitro system, and digestion was increased when CG was added to cultures with ruminal fluid from CG-fed animals. Total VFA were unaffected by diets or by substrate incubated. The CG increased production of propionate, butyrate, and valerate (P < 0.01) while the gas production was unaffected (P = 0.16). In Exp. 2, 24 crossbred heifers (334.4 ± 0.9 kg BW) were fed the same diets as Exp. 1, for 35 d. Fecal grab samples were collected 3 times daily on day 7, 21, and 35, to evaluate total tract digestibilities of DM, OM, and NDF. The CG improved digestibility of diet OM (P = 0.04), and DM followed a similar trend (P = 0.06), while the NDF digestibility was unaffected (P = 0.29). In Exp. 3, crossbred heifers (n = 374; 375.8 ± 36.1 kg BW) were used to evaluate feedlot performance and carcass traits when fed diets with 0, 7.5, or 15% CG, with or without added 0.3% salt. Heifers were assigned to 25 pens and were harvested on day 125. Removing salt from CG-based diets did not impact performance (P = 0.50). The CG did not influence average daily gain (P = 0.27), but decreased DM intake (P = 0.003), USDA Yield Grade (P = 0.01), and improved feed efficiency (P = 0.03), while tended to decrease USDA prime carcasses (P = 0.10). Carcass weight (P = 0.24), Longissimus muscle area (P = 0.63), and kidney, pelvic, heart fat (P = 0.59) were unaffected by CG. Twelfth-rib fat was less for heifers fed 15% CG without salt compared with the other treatments (P = 0.005), while marbling was less for heifers fed CG diets compared with the control-fed animals (linear, P = 0.004; quadratic, P = 0.02). In conclusion, GC can replace dry-rolled corn in diets for beef heifers when fed at 15% of diet DM, improving OM digestion, increasing ruminal propionate and butyrate without affecting greenhouse gas emissions. Feeding up to 15% CG improves feed efficiency but depresses marbling and tends to decrease Quality Grade. Removing supplemental salt from CG-diets has no impact on performance or carcass traits.

Effects of a recombinant fibrolytic enzyme on fiber digestion, ruminal fermentation, nitrogen balance, and total tract digestibility of heifers fed a high forage diet1.

A metabolism study was conducted using 8 ruminal cannulated beef heifers to investigate the effects of a recombinant fibrolytic enzyme (RFE; xylanase XYL10C) selected specifically for forage-fed ruminants on ruminal pH, fermentation, nitrogen balance, and total tract digestibility of heifers. The experiment was a cross-over design with 2 treatments and 2 periods. The 2 treatments were a basal diet containing 60% barley silage, 30% barley straw, and 10% supplement (DM basis) without (control) or with RFE. The enzyme was sprayed onto the barley straw at a rate of 6.6 × 104 IU·kg-1 DM 24 h before feeding. Each period comprised 2 wk of diet adaptation and 1 wk of sampling and data collection. Feed intake and total tract digestibility of DM, OM, NDF, and ADF were unaffected by RFE. Ruminal pH including mean, minimum, maximum, and duration pH <5.8, did not differ between treatments. Total VFA concentration, molar proportion of individual VFA, and acetate-to-propionate ratio were also not affected by RFE. However, ruminal NH3-N concentration (P < 0.06) and endoglucanase activity (P < 0.08) in ruminal fluid tended to be higher with RFE. Nitrogen utilization and microbial protein synthesis were not affected by treatment. These results indicate that XYL10C did not improve fiber digestion in heifers fed a high forage diet, despite the fact that it was specifically selected for this trait in laboratory assays. However, the increased ruminal NH3-N concentration suggests it potentially increased ruminal proteolytic activity.

Insoluble dietary fiber does not affect the ability of phytase to release phosphorus from phytate in the diet of nursery pigs1.

Phytase is added to swine diets to improve the utilization of phytate-bound P in swine diets. This provides financial and environmental benefits to the pig industry. However, it is unclear if phytase works equally well in all dietary circumstances. The objective of this experiment was to determine if insoluble fiber affects the efficacy of the phytase enzyme in nursery pigs when fed diets limiting in P content. A total of 480 pigs (initial BW 5.48 ± 0.14 kg) were blocked by BW and randomly assigned (10 pigs per pen) to treatment within the block. A common nutrient-adequate diet was fed from days -14 to -5, and two basal P deficient diets (either a corn-soy diet containing 0.16% standardized total tract digestible [STTD] P [low insoluble fiber [LF]], or a corn-soybean meal plus 20% corn bran containing 0.14% STTD P [high insoluble fiber [HF]]) were fed from days -5 to 0 to acclimate pigs to a P deficient diet. From days 0 to 21, pigs received eight dietary treatments (six pens per treatment: n = 6). Experimental diets consisted of LF supplemented with one of four levels of added phytase (0, 109, 218, and 327 phytase units [FTU]/kg; Quantum Blue 5 G, AB Vista, Wiltshire, United Kingdom) expected to provide 0.16, 0.21, 0.26, and 0.31% STTD P, respectively, or HF supplemented with one of the same four levels of added phytase expected to provide 0.14, 0.19, 0.24, and 0.29% STTD P. Titanium dioxide was added to the diet at 0.4% as an indigestible marker. On day 21, one pig representing the average BW for each pen was euthanized, and fibulae were collected and analyzed for bone ash. Fecal samples were collected from each pen on days 19-20. Data were analyzed using PROC MIXED of SAS. There were no interactions between insoluble fiber and phytase for any of the variables evaluated. For days 0-21, adding phytase increased ADG (P < 0.001) with the response being linear (P < 0.001), whereas insoluble fiber decreased ADG (P = 0.033). There were no effects of phytase or insoluble fiber on ADFI (P = 0.381 and P = 0.632, respectively). Phytase improved G:F ratio (P < 0.001) with the response being linear (P < 0.001). Insoluble fiber tended to decrease G:F ratio (P = 0.097). Phytase increased bone ash (P = 0.005) with the response being linear (P = 0.001), but there was no effect of insoluble fiber (P = 0.949). Phytase did not affect the apparent total tract digestibility of DM, NDF, or ADF (P > 0.050), whereas insoluble fiber decreased the ATTD of DM (P < 0.001), NDF (P < 0.001), and ADF (P < 0.001). In conclusion, the addition of insoluble fiber did not affect the ability of phytase to improve growth performance and bone mineralization in nursery pigs fed a P deficient diet.

Effects of level of intake of a 50% concentrate pelleted diet on metabolizability by mature Katahdin wethers

Ten adult Katahdin sheep wethers (74.3 ± 2.03 kg initial BW), approximately 3 yr of age, were used in a crossover experiment to study effects of a restricted feeding regime on digestibility, metabolizability, and heat energy. A 50% concentrate pelleted diet was fed near the ME requirement for maintenance (Control; DM intake = 44.4 g/kg BW0.75) and at 55% of this level (Restricted; DM intake = 24.4 g/kg BW0.75). Periods were 4 wk in length, with 3 wk for adaptation, measures in the final week when animals were situated in metabolism cages, and 2 days for gas exchange quantification via a head-box respiration calorimetry system. Apparent total tract digestibilities of DM (68.9 and 76.1%; SEM = 1.08), OM (78.3 and 83.3%; SEM = 1.57), CP (74.6 and 80.7%; SEM = 1.68), NDF (50.9 and 61.9%; SEM = 3.23), and gross energy (77.9 and 83.0%; SEM = 1.59) were greater (P < 0.05) for Restricted than for Control. Expressed in MJ/day, energy in urine (1.03 and 0.67; SEM = 0.294) and ruminally emitted methane (1.03 and 0.77; SEM = 0.076) were greater for Control vs. Restricted (P < 0.05), but as a percentage of gross energy were at least numerically greater for Restricted (urine: 5.63 and 6.48%, SEM = 2.218 and P = 0.594; methane: 5.46 and 7.16% for Control and Restricted, respectively, SEM = 0.579 and P = 0.030). As a consequence, ME intake as a percentage of gross energy intake did not differ (P = 0.354) between treatments (66.8 and 69.4% for Control and Restricted, respectively; SEM = 2.89). The treatment difference in heat energy (11.05 and 9.29 MJ/day; SEM = 0.563) was less than in ME intake (12.67 and 7.30 MJ/day for Control and Restricted, respectively; SEM = 0.508); thus, recovered energy differed from 0 (P < 0.05) and was greater for Control vs. Restricted (1.62 and −1.99 MJ/day; SEM = 0.661). In conclusion, restricted feed intake had marked influence on digestibility, although energy losses in urine and methane energy compensated so that metabolizability did not differ between treatments. With a diet of this nature a similar ME concentration could be assumed for studies with hair sheep fed near the standard maintenance requirement and restricted in intake.

Extruded Corn Meal as a Partial Replacement for Steam Flaked Corn in Finishing Diets for Feedlot Cattle: Growth Performance and Digestive Function of Feedlot Cattle

Sixty-four Holstein steers (247 ± 4 kg) were used in a 70-d experiment to evaluate the effects of partial replacement of steam flake corn (SFC) with extruded corn meal (EC) on growth performance and dietary net energy. Treatments consisted of a steam flaked corn-based finishing diet containing 0%, 10%, 20%, or 30% EC, where EC replaced 0%, 15%, 30%, or 45% of SFC (DM basis). Replacement of SFC with increasing levels of EC did not affect (P > 0.10) ADG, DMI, and gain efficiency. When EC replaced 15% to 30% of SFC, observed dietary NE was 99% of expected. Whereas, when EC replaced 45% of SFC, observed dietary NE was 94% of expected. Four Holstein steers (210 ± 7 kg) with cannulas in the rumen and proximal duodenum were used in a 4 × 4 Latin square experiment to evaluate treatment effects on characteristics of digestion. Partial replacement of SFC with EC did not affect (P > 0.10) flow of undegraded feed N and microbial N and to the small intestine, and ruminal microbial N efficiency (g microbial N/kg OM fermented). Likewise, there were no treatment effects (P > 0.10) on ruminal digestion of OM, NDF, starch and feed N. As expected, total tract digestion of starch for all treatments exceeded 99%. However, partial replacement of SFC with EC decreased total tract digestion of DM and OM (linear effect, P = 0.02), and dietary DE (linear effect, P = 0.03). These effects were more pronounced where EC replaced 45% of SFC. Partial replacement of SFC with EC did not affect (P > 0.10) ruminal pH, total VFA concentration, molar proportions of acetate, propionate, and butyrate, and estimated methane production. It is concluded that partial replacement of SFC with EC does not have a beneficial effect on ruminal microbial efficiency and digestive function. The feeding value of extruded corn for feedlot cattle is comparable to that of steam flaked corn provided the inclusion rate does not exceed 20% of diet dry matter.

Effect of exercise on apparent total tract digestibility of nutrients and faecal recovery of ADL and TiO2 in ponies

Exercise and physical training are known to affect gastrointestinal function and digestibility in horses and can lead to inaccurate estimates of nutrient and energy digestibility when markers are used. The effect of exercise on apparent nutrient digestibility and faecal recoveries of ADL and TiO2 was studied in six Welsh pony geldings subjected to either a low- (LI) or high-intensity (HI) exercise regime according to a cross-over design. Ponies performing LI exercise were walked once per day for 45 min in a horse walker (5 km/h) for 47 consecutive days. Ponies submitted to HI exercise were gradually trained for the same 47 days according a standardized protocol. Throughout the experiment, the ponies received a fixed level of feed and the daily rations consisted of 4.7 kg DM of grass hay and 0.95 kg DM of concentrate. The diet was supplemented with minerals, vitamins and TiO2 (3.0 g Ti/day). Total tract digestibility of DM, organic matter (OM), CP, crude fat, NDF, ADF, starch, sugar and energy was determined with the total faeces collection (TFC) method. In addition, DM and OM digestibility was estimated using internal ADL and the externally supplemented Ti as markers. Urine was collected on the final 2 days of each experimental period. Exercise did not affect apparent digestibility of CP, crude fat, starch and sugar. Digestibility of DM (DMD), OM (OMD), ADF and NDF tended to be lower and DE was decreased when ponies received the HI exercise regime. For all treatments combined, mean faecal recoveries of ADL and Ti were 87.8±1.7% and 99.3±1.7%, respectively. Ti was not detected in the urine, indicating that intestinal integrity was maintained with exercise. Dry matter digestibility estimated with the TFC, ADL and Ti for ponies subjected to LI exercise were 66.3%, 60.3% and 64.8%, respectively, while DMD for HI ponies were 64.2%, 60.3% and 65.2%, respectively. In conclusion, physical exercise has an influence on the GE digestibility of the feed in ponies provided with equivalent levels of feed intake. In addition, the two markers used for estimating apparent DMD and OMD indicate that externally supplemented Ti is a suitable marker to determine digestibility of nutrients in horses performing exercise unlike dietary ADL.

583 Effects of lipid intake and degree of saturation on nutrient digestion and nitrogen balance in steers consuming corn-based diets

Increases in dietary lipid can augment energy density; however, lipids can mitigate ruminal fermentation of feed. We evaluated effects of amount and source of dietary lipid on nutrient digestibility, ruminal fermentation, and N balance in cattle consuming corn-based diets. Five steers (BW = 392 ± 15 kg) fitted with ruminal, duodenal, and ileal cannulas were used in a 5 × 5 Latin square with 12-d periods. Diets contained no added fat, or 4 or 8% added lipid from either a predominantly saturated (i.e., tallow) or predominantly unsaturated (i.e., linseed oil) source. Unsaturated fat decreased (P= 0.01) DMI compared to saturated fat and increasing amount of lipid supplementation tended (Linear= 0.14) to decrease DMI. Neither added amounts or source of lipid affected (P≥ 0.33) ruminal NDF digestion. However, increased diet lipid decreased ruminal DM digestibility (Linear= 0.04) and tended (Linear= 0.15) to decrease ruminal starch digestibility. Apparent (Linear= 0.03) and truly (Linear= 0.05) fermented OM in the rumen decreased in response to increased dietary lipid. Ruminal pH (P≥ 0.50), ammonia (P≥ 0.18) and total organic acid content (P≥ 0.31) were not affected by diet lipid. Additionally, amount and source of lipid had no effect on ruminal acetate (P≥ 0.21) or propionate (P≥ 0.21) concentrations; however, lipid amount tended (Linear= 0.07) to decrease acetate:propionate. Similarly, total tract digestion of DM (Linear<0.01), OM (Linear<0.01), and NDF (Linear= 0.02) were decreased by added dietary lipid. Greater lipid intake also tended (P= 0.12) to decrease total tract starch digestion. Unsaturated lipid tended (P= 0.06) to decrease total tract NDF digestibility, but saturated lipid tended to decrease total tract DM (P =0.12) and OM (P= 0.10) digestion. Microbial N flow to the duodenum was not affected (P≥ 0.18) by lipid, but microbial efficiency tended (Linear= 0.06) to increase with increased lipid intake. Fecal N excretion was decreased (P<0.01) by unsaturated lipid. Nitrogen balance (P≥ 0.28) and N efficiency (P≥ 0.58) were not affected by lipid source or amount.