Black rhinoceros (Diceros bicornis) and domestic horse (Equus caballus) hindgut microflora demonstrate similar fermentation responses to grape seed extract supplementation in vitro.

The domestic horse is used as a nutritional model for rhinoceros maintained under human care. The validity of this model for browsing rhinoceros has been questioned due to high prevalence of iron overload disorder (IOD) in captive black rhinoceros (Diceros bicornis), which is associated with high morbidity and mortality. Iron chelators, such as tannins, are under investigation as dietary supplements to ameliorate or prevent IOD in prone species. Polyphenolic compounds variably affect microbial fermentation, so the first objective of this experiment was to evaluate the effects of grape seed extract (GSE; a concentrated source of condensed tannins; CT) on black rhinoceros hindgut fermentation. Equine nutrition knowledge is used to assess supplements for rhinoceros; therefore, the second objective was to evaluate the domestic horse model for black rhinoceros fermentation and compare fermentation responses to GSE using a continuous single-flow in vitro culture system. Two replicated continuous culture experiments were conducted using horse and black rhinoceros faeces as inoculum sources comparing four diets with increasing GSE inclusion (0.0%, 1.3%, 2.7% and 4.0% of diet dry matter). Diet and GSE polyphenolic compositions were determined, and sodium sulphite effect on neutral detergent fibre extraction of CT-containing forages was tested. Increasing GSE inclusion stimulated microbial growth and fermentation, and proportionally increased diet CT concentration and iron-binding capacity. Horse and black rhinoceros hindgut microflora nutrient digestibility and fermentation responses to GSE did not differ, and results supported equine fermentation as an adequate model for microbial fermentation in the black rhinoceros. Interpretation of these results is limited to hindgut fermentation and further research is needed to compare foregut digestibility and nutrient absorption between these two species. Supplementation of GSE in black rhinoceros diets up to 4% is unlikely to adversely affect hindgut nutrient digestibility or microbial viability and fermentation.

Effect of corn inclusion on soybean hull-based diet digestibility and growth performance in continuous culture fermenters and beef cattle.

Two experiments were conducted using soybean hull (SH) diets with increasing corn proportions to determine increasing corn inclusion effects on fermentation characteristics, diet digestibility, and feedlot performance. The hypothesis was that fiber digestibility would quadratically respond to starch proportion in the diet with a break point where starch inclusion improved fiber digestion and feedlot performance. Proportionately, the diets contained 100:0 (SH100), 90:10 (SH90), 80:20 (SH80), 60:40 (SH60), or 20:80 SH:corn (SH20). In Exp. 1, diets were randomly distributed over 24 continuous culture fermenters and fed for 7 d. In Exp. 2, forty steers (347 ± 29 kg BW) and 50 heifers (374 ± 24 kg BW) were blocked by gender, stratified by BW, and distributed across diets. Cattle were fed for 70 d with titanium dioxide included in the diet for the final 14 d and fecal samples collected to measure digestibility. Individual DMI was measured using GrowSafe Feed Intake system. Data were analyzed using the MIXED procedure of SAS with diet evaluated as the fixed effect. In Exp. 1, NDF digestibility (NDFd) linearly decreased ( = 0.04) and ADF digestibility (ADFd) tended to linearly decrease ( = 0.09) as corn increased. Dry matter digestibility (DMd) was cubic ( = 0.01) and OM digestibility (OMd) was quadratic ( = 0.03), and among the 4 SH-based diets, DMd and OMd were greatest for SH90. Acetate:propionate ratio and pH were quadratic ( < 0.01) and greatest for SH80. In Exp. 2, ADG and G:F linearly increased ( < 0.01) as corn inclusion increased. Among the 4 SH-based diets, ADG was numerically greatest for SH80. There was no DMI difference ( ≥ 0.4) due to diet. As corn inclusion increased, DMd tended to linearly increase (P = 0.06), as did OMd ( = 0.05). Both NDFd and ADFd were quadratic ( = 0.04) and greatest for SH80. Overall, feedlot performance increased and fiber digestibility decreased as corn inclusion increased. However, based on continuous culture digestibility and VFA values as well as feedlot digestibility and performance, optimal corn inclusion for growth and diet utilization in the 4 SH-based diets fell between SH80 and SH90, or 0.4 and 0.2% BW corn supplementation. In this study, providing 0.4% BW corn supplementation in fiber-based diets (SH80) provided greater improvement in performance compared with 0.2% BW corn supplementation (SH90).

Influence of growing phase feed efficiency classification on finishing phase growth performance and carcass characteristics of beef steers fed different diet types.

A 5-yr study was conducted using 985 crossbred steers (464 kg [SD 32]) fed in 6 separate, replicated groups to determine the influence of growing phase (GP) feed efficiency (FE) classification and diet type on finishing phase (FP) FE of steers. During the GP at the University of Missouri, steers were fed either a whole shell corn-based diet (G-Corn; 528 steers) or a roughage-based diet (G-Rough; 457 steers) using GrowSafe feed bunks to measure DMI for 69 to 89 d. At the end of the GP, steers were ranked by residual feed intake (RFI) within diet, shipped to Iowa State University, and blocked into FP pens (5 to 6 steers/pen) by GP diet and RFI rank (upper, middle, or lower one-third). Steers were transitioned to either FP cracked corn- or byproduct-based diets and fed until 1.27 cm backfat was reached. After completion of the sixth group, average GP G:F within GP diet was calculated for each FP pen (168 total pens) using GP initial BW as a covariate (G-Corn: 0.207 [SD 0.038]; G-Rough: 0.185 [SD 0.036]). Pens were classified as highly feed efficient (HFE; >0.5 SD from the G:F mean; 58 pens), mid feed efficient (MFE; ±0.5 SD from the G:F mean; 60 pens), or lowly feed efficient (LFE; <0.5 SD from the G:F mean; 50 pens). Data were analyzed using PROC MIXED of SAS. Experimental unit was FP pen and the model included the fixed effects of GP diet, FE classification, FP diet, and the interactions. Group (1 to 6) was included as a fixed effect. There were no 3-way interactions ( ≥ 0.2) for any measured traits. Finishing phase G:F was not affected by any interactions ( ≥ 0.5) but was greater ( ≤ 0.03) for HFE versus MFE and LFE and greater ( = 0.02) for MFE versus LFE. Growing phase diet × FE classification effects were detected ( ≤ 0.01) for FP final BW (FBW), ADG, and DMI. Among G-Rough steers, HFE and MFE had greater ( ≤ 0.04) FBW and ADG than LFE, but among G-Corn steers, LFE had heavier ( = 0.03) FBW than HFE whereas ADG was unaffected ( ≥ 0.2) by FE classification. Dry matter intake was unaffected ( ≥ 0.3) by FE classification among G-Rough steers, but among G-Corn steers, LFE had greater ( ≤ 0.003) DMI than MFE and HFE. Overall, differences in FP G:F between FE classifications were driven by different factors depending on diet; ADG differed among roughage-grown steers and DMI differed among corn-grown steers. Ultimately, steers classified as HFE during the GP still had superior FE during the FP.

Relationship between antioxidant capacity, oxidative stress, and feed efficiency in beef steers.

Feed efficiency (FE) can vary between individuals but sources of variation are not well characterized. Oxidative stress is among the biological mechanisms believed to contribute to variation. The objective of this study was to evaluate the relationship between FE, antioxidant activity, and oxidative stress in feedlot steers representing phenotypic extremes for FE. Crossbred beef steers ( = 181) fed 70-d growing phase (GP) whole-shell corn-based (G-Corn) or rye baleage and soybean hull-based (G-Rough) diets in GrowSafe bunks at the University of Missouri were shipped to Iowa State University where the 12 most feed efficient (HFE) and 12 least feed efficient (LFE) steers from each diet (n = 48; 467 kg [SD 51]) were selected for evaluation. Steers received diets similar to GP diets, and 3 d after arrival, blood was sampled to evaluate antioxidant activity and oxidative stress markers for the GP following transit. Steers were transitioned to finishing phase (FP) cracked corn-based (F-Corn) or dried distillers' grains and soybean hull-based (F-Byp) diets, and on FP d 97, blood samples for the FP were collected. Data for the GP were analyzed as a 2 × 2 factorial, and data for the FP were analyzed as a 2 × 2 × 2 factorial using PROC MIXED of SAS. No GP diet × FP diet, FP diet × FE group, or 3-way interactions were noted ( ≥ 0.11) for FP measures. Steers fed the G-Rough diet had greater ( = 0.04) GP plasma protein carbonyl concentrations. During the GP, HFE steers had greater ( ≤ 0.04) protein carbonyl and ratio of oxidized:reduced blood lysate glutathione concentrations than LFE steers. There were GP diet × FE group interactions ( ≤ 0.03) during the GP and FP. During the GP, total blood lysate superoxide dismutase (SOD) activity was greater ( ≤ 0.03) in G-Rough/LFE steers than in G-Rough/HFE and G-Corn/LFE steers; G-Corn/HFE steers were intermediate. The G-Rough/LFE steers had greater ( < 0.04) glutathione peroxidase (GPX) activity than other groups and greater ( = 0.03) plasma malondialdehyde concentrations than G-Corn/LFE steers. During the FP, the G-Rough/LFE steers had greater ( ≤ 0.04) GPX activity than G-Rough/HFE and G-Corn/LFE steers; G-Corn/HFE steers were intermediate. The F-Byp diet had greater ( < 0.01) protein carbonyl than the F-Corn diet, and no other FP diet effects were noted ( ≥ 0.3) for any FP measures. The GP diet and FE groups had stronger relationships with antioxidant activity and oxidative stress markers measured for the GP than for the FP. Overall, antioxidant activity may play a role in FE as LFE steers, driven largely by G-Rough/LFE steers, had greater SOD activity and GPX activity than HFE steers, potentially using a greater proportion of energy otherwise available for tissue accretion.

Soybean hull and enzyme inclusion effects on diet digestibility and growth performance in beef steers consuming corn-based diets.

A beef feedlot study was conducted to determine the effects of increasing soybean hull (SH) inclusion and enzyme addition on diet digestibility and animal performance. The hypothesis was SH inclusion and enzyme addition would increase fiber digestibility with no negative effect on animal performance. Eight treatments (TRT) were arranged in a 4 × 2 factorial using four diets and two enzyme (ENZ) inclusion rates. The diets were composed primarily of whole shell corn (WSC) with 0%, 7%, 14%, or 28% SH replacing corn. The ENZ was a commercial proprietary mix of , and (Cattlemace, R&D Life Sciences, Menomonie, WI) included in the diets at 0% (S0, S7, S14, S28) or 0.045% DM basis (S0e, S7e, S14e, S28e). Eighty steers (287 ± 31 kg, SD) were stratified by weight and blocked into pens with 1 heavy and 1 light pen per TRT (2 pen/TRT, 5 steers/pen). Steers were fed for 70 d with titanium dioxide included in the diets for the final 15 d. Fecal samples were collected on d 70 to determine diet digestibility. Diets were balanced for AA and RDP requirement based on available ME. Individual DMI was measured using a GrowSafe system. Diet, ENZ, and diet × ENZ effects were analyzed using the MIXED procedure of SAS. Initial BW was applied as a covariate for final BW (FBW), and DMI was included as a covariate for all digestibility measures. The diet × ENZ interaction had no effect on FBW, ADG, DMI, or any digestibility measure ( ≥ 0.11). Steers fed ENZ tended to have greater FBW ( = 0.09) and had numerically greater ADG than steers not fed ENZ. Diet influenced DMI ( < 0.01), as steers fed S7 diets had the greatest DMI ( ≤ 0.3), steers fed S0 diets had the least DMI ( ≤ 0.002), and DMI of steers fed S14 and S28 diets did not differ ( = 0.5). There was a diet × ENZ interaction for G:F ( = 0.02) in which S0, S0e, S14e, and S28e did not differ ( ≥ 0.3) and were greatest ( ≤ 0.05). There was no effect of diet or ENZ on DM, OM, or CP digestibility ( ≥ 0.2). Diet had an effect on NDF and ADF digestibility ( ≤ 0.04) which decreased as SH inclusion increased. The addition of ENZ tended to decrease NDF digestibility ( = 0.08) but had no effect on ADF digestibility ( = 0.8). Fiber digestibility in WSC diets did not improve with SH inclusion or ENZ addition but steers fed diets with 14% to 28% of WSC replaced by SH and the addition of 0.045% ENZ converted feed at the same rate as steers fed WSC diets with no SH.

Relationship between residual feed intake and lymphocyte mitochondrial complex protein concentration and ratio in crossbred steers.

Rate of oxygen uptake by muscle mitochondria and respiratory chain protein concentrations differed between high- and low-residual feed intake (RFI) animals. The hypothesis of this research was that complex I (CI), II (CII), and III (CIII) mitochondria protein concentrations in lymphocyte (blood) mitochondria were related to the RFI phenotype of beef steers. Daily feed intake (ADFI) was individually recorded for 92 Hereford-crossbreed steers over 63 d using GrowSafe individual feed intake system. Predicted ADFI was calculated as the regression of ADFI on ADG and midtest BW. Difference between ADFI and predicted ADFI was RFI. Lymphocytes were isolated from low-RFI (-1.32 ± 0.11 kg/d; = 10) and high-RFI (1.34 ± 0.18 kg/d; = 8) steers. Immunocapture of CI, CII, and CIII proteins from the lymphocyte was done using MitoProfile CI, CII, and CIII immunocapture kits (MitoSciences Inc., Eugene, OR). Protein concentrations of CI, CII, and CIII and total protein were quantified using bicinchoninic acid colorimetric procedures. Low-RFI steers consumed 30% less ( = 0.0004) feed and had a 40% improvement ( < 0.0001) in feed efficiency compared with high-RFI steers with similar growth ( = 0.78) and weight measurements ( > 0.65). High- and low-RFI steers did not differ in CI ( = 0.22), CII ( = 0.69), and CIII ( = 0.59) protein concentrations. The protein concentration ratios for CI to CII ( = 0.03) were 20% higher and the ratios of CI to CIII ( = 0.01) were 30% higher, but the ratios of CII to CIII ( = 0.89) did not differ when comparing low-RFI steers with high-RFI steers. The similar magnitude difference in feed intake, feed efficiency measurements, and CI-to-CIII ratio between RFI phenotypes provides a plausible explanation for differences between the phenotypes. We also concluded that mitochondria isolated from lymphocytes could be used to study respiratory chain differences among differing RFI phenotypes. Further research is needed to determine if lymphocyte mitochondrial complex proteins can be used for identification of RFI phenotype.

Influence of feed efficiency classification on diet digestibility and growth performance of beef steers.

The diet digestibility and feed efficiency (FE) relationship is not well characterized in cattle. The study objective was to determine effects of growing phase FE and diet as well as finishing phase diet on diet digestibility and finishing phase FE. Two groups, totaling 373 crossbred steers, were fed for 70 d at the University of Missouri for the growing phase and then shipped to Iowa State University (ISU) for finishing. GrowSafe feed bunks were used during both the growing and the finishing phases. Steers were fed either growing phase whole shell corn (G-Corn) or growing phase roughage-based (G-Rough) diets. Within each group, the 12 greatest and 12 least feed efficient steers from each growing diet ( = 96 total; 48 steers/group; 488 ± 5 kg) were selected for further evaluation. At ISU, steers were fed an average of 10 g TiO/steer daily in receiving phase diets similar to growing diets for 15 d, with fecal grab samples collected on d 14 and 15 to determine diet DM digestibility during receiving (GDMdig). For finishing, steers were transitioned to byproduct-based diets (F-Byp) or corn-based diets (F-Corn) with 12 steers per growing-finishing diet combination per group. Optaflexx (200 mg/d) was fed for 28 d before harvest, and the TiO protocol was repeated immediately before introducing Optaflexx to determine diet DM digestibility during finishing (FDMdig). Data from the 2 groups (96 steers) were pooled, and steers were ranked by growing phase G:F and then classified as the 24 greatest feed efficient (HFE) or 24 least feed efficient (LFE) steers from each growing diet. Data were analyzed using PROC MIXED of SAS with group applied as a fixed effect. There was a positive correlation between GDMdig and FDMdig for steers fed nutritionally similar diets during both feeding phases, G-Rough/F-Byp steers ( = 0.68, < 0.01) and G-Corn/F-Corn steers ( = 0.49, = 0.02), but a negative correlation for G:F between phases in G-Rough/F-Corn steers ( = -0.57, < 0.01). Finishing G:F was greater in HFE steers versus LFE steers ( = 0.04), but there was no difference ( ≥ 0.5) in GDMdig or FDMdig due to FE classification. There was a positive correlation for DM digestibility between feeding phases when steers were grown and finished on similar diets. Overall, FE was repeatable but was negatively correlated between phases when steers were roughage grown and corn finished, reinforcing the idea that cattle should be FE tested using diet types similar to the production environment of interest.

Mitochondrial complex I protein differs among residual feed intake phenotype in beef cattle.

Four experiments were performed to determine if residual feed intake (RFI) was related to mitochondrial complex I (CI) protein. For Exp. 1, crossbred Angus steers (initial BW 270 ± 2.0 kg) were fed for a total of 170 d (n = 72). For Exp. 2, crossbred Braunvieh steers (initial BW 280 ± 3.0 kg) were fed for a total of 150 d (n = 50). For Exp. 3, crossbred Braunvieh heifers (initial BW 260 ± 3.0 kg) were fed for a total of 160 d (n = 40). For Exp. 4, crossbred Angus steers (initial BW 290 ± 3.0 kg) were fed for a total of 160 d (n = 40). All cattle in all experiments were fed the same diet. The variable RFI was calculated as the difference between predicted and actual DMI. Predicted DMI was calculated from regressing intake on ADG and metabolic body weight. Blood was collected, lymphocytes were isolated, and antibody used to capture CI. For Exp. 1, 2, and 3, CI quantity was measured using an ELISA commercial kit (Mitosciences, OR). For Exp. 4, CI subunits were separated by gel electrophoresis and bands were analyzed for differences in concentration (absorbance) among RFI phenotypes. For all 4 experiments, there was a significant difference (P < 0.05) between RFI and DMI but no difference (P > 0.05) was reported for ADG and metabolic midweight. For Exp. 1, 2, and 3, CI concentration in mitochondria was greater (P < 0.05) for low RFI compared with other treatments. For Exp. 4, animals with low RFI had a trend (P = 0.07) for greater concentration of Band I (protein S1) than high RFI. Correlation between RFI and Band I was -0.72 (P = 0.04). We concluded that mitochondrial function was at least in part responsible for differences among animals in metabolic efficiency.

Rumen degradable protein supply affects microbial efficiency in continuous culture and growth in steers.

We hypothesized that microbial efficiency and output from fermentation in the rumen would be optimized when peptide supply was balanced with peptide requirement of ruminal microflora. This study was conducted to measure response of varying rumen degradable peptide (RDPep) supply on ruminal fermentation characteristics and steer growth. A continuous culture experiment was conducted with diets formulated to achieve a predicted RDPep balance (RDPep supplied above RDPep required) of -0.30 to 1.45% CP with rumen degradable N (RDN) balance (RDN supplied above RDN required) above dietary ammonia-N requirement of microbes. Two additional treatments had RDPep balances of -0.30 and 0.78% CP with insufficient ammonia-N supply to meet microbial requirements. Single-flow fermenters (N = 24; n = 6) were inoculated with rumen fluid and maintained anaerobically at 39°C with a 0.06 h(-1) dilution rate. Inadequate RDN decreased OM digestion and microbial N flow, and increased rumen undegradable N (P < 0.01). Microbial efficiency decreased in RDN-deficient diets and was greatest when RDPep balance did not excessively exceed microbial requirement of RDPep predicted (P < 0.01). A growth study was conducted with 49 yearling, crossbred, Angus steers (initial BW 370 ± 34 kg). Animals were assigned to 1 of 4 treatment groups by BW and further divided into 3 pens with 4 steers per pen to achieve similar initial pen weights. Treatments consisted of 4 isonitrogenous diets balanced for RDN but varying in predicted RDPep balance (0.55%, -0.02%, -0.25%, and -0.65% CP). Animals were maintained on treatment for 70 d with individual BW taken on d 0, 1, 21, 42, 70, and 71. Final BW decreased linearly with decreasing RDPep (P = 0.05). Average daily gain and G:F displayed a quadratic effect with greater ADG and G:F at greater and lesser RDPep levels (P = 0.02). We concluded that balancing RDPep supply to predicted requirement improved fermentation efficiency and microbial output, which in turn improved animal performance.

Genome-wide association analysis for feed efficiency in Angus cattle.

Estimated breeding values for average daily feed intake (AFI; kg/day), residual feed intake (RFI; kg/day) and average daily gain (ADG; kg/day) were generated using a mixed linear model incorporating genomic relationships for 698 Angus steers genotyped with the Illumina BovineSNP50 assay. Association analyses of estimated breeding values (EBVs) were performed for 41,028 single nucleotide polymorphisms (SNPs), and permutation analysis was used to empirically establish the genome-wide significance threshold (P < 0.05) for each trait. SNPs significantly associated with each trait were used in a forward selection algorithm to identify genomic regions putatively harbouring genes with effects on each trait. A total of 53, 66 and 68 SNPs explained 54.12% (24.10%), 62.69% (29.85%) and 55.13% (26.54%) of the additive genetic variation (when accounting for the genomic relationships) in steer breeding values for AFI, RFI and ADG, respectively, within this population. Evaluation by pathway analysis revealed that many of these SNPs are in genomic regions that harbour genes with metabolic functions. The presence of genetic correlations between traits resulted in 13.2% of SNPs selected for AFI and 4.5% of SNPs selected for RFI also being selected for ADG in the analysis of breeding values. While our study identifies panels of SNPs significant for efficiency traits in our population, validation of all SNPs in independent populations will be necessary before commercialization.

Integrating bermudagrass into tall fescue-based pasture systems for stocker cattle.

The daily BW gain of stocker steers grazing tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort.]-based pastures typically declines during summer. To avoid these declines, in part to mitigate the effects of tall fescue toxicosis, it is commonly advised to move cattle to warm-season forage during this period. A 3-yr (2006, 2007, and 2008) grazing study was conducted to evaluate the effect of replacing 25% of the area of a tall fescue/clover (81% endophyte-infected) pasture system with "Ozark" bermudagrass [Cynodon dactylon (L.) Pers.] overseeded with clover (Trifolium spp.) to provide summer grazing for stocker steers (TF+BERM). The TF+BERM treatment was compared with a grazing system in which tall fescue/clover (TF) pastures were the only type of forage available for grazing. Our objective was to determine if replacement of 25% of the land area in a fescue system with bermudagrass would increase annual beef production compared with a system based solely on tall fescue. The study was conducted at the Southwest Research and Education Center of the University of Missouri near Mt. Vernon. Each treatment was rotationally stocked with 5 steers (248 ± 19.3 kg) on 1.7 ha. Fertilizer applications were applied at rates recommended for each respective forage species. Total forage production, BW gain per hectare, and season-long ADG of steers was greater (P < 0.06) for TF+BERM than for TF in 2006, but none of these measures differed (P > 0.19) in 2007 or 2008. In vitro true digestibility of pastures was greater (P = 0.01) for TF (84.4%, SEM = 0.64%) compared with TF+BERM (80.6%, SEM = 0.79%), even in summer. The decreased in vitro true digestibility of the bermudagrass pastures likely negated any benefit that animals in TF+BERM had in avoiding the ergot-like alkaloids associated with endophyte-infected tall fescue. Renovating 25% of the pasture system to bermudagrass provided some benefit to the system in years when summertime precipitation was limited (2006) but provided no value in wetter years (2007 and 2008). Although renovating endophyte-infected tall fescue pastures to a warm-season forage is a widely used practice to mitigate tall fescue toxicosis, the benefits of this practice are limited if forage quality of the warm season component is poor.

Effect of dietary crude glycerol level on ruminal fermentation in continuous culture and growth performance of beef calves.

Continuous culture and in vivo experiments were conducted to measure changes in ruminal fermentation and animal performance when crude glycerol was added to diets. For the continuous culture experiment (n = 6), diets consisted of 4 levels of crude glycerol (0, 5, 10, and 20%) that replaced corn grain. Dry matter and OM digestibility decreased linearly (P < 0.05) when crude glycerol increased in the diet, and no effect (P = 0.20 and 0.65, respectively) was observed for CP and NDF digestibility. Total VFA concentration and ammonia did not change (P > 0.05) due to crude glycerol level. Microbial efficiency increased quadratically (P = 0.012) as crude glycerol increased, whereas microbial N flow did not differ (P = 0.36) among treatments. As crude glycerol increased in the diet, crude glycerol digestibility decreased (P < 0.05). Seventy-two crossbred steer calves (250 ± 2.0 kg) were assigned to 4 treatments: 0, 5, 10, and 20% crude glycerol that replaced corn grain. Animals were fed for a total of 150 d. No differences (P = 0.08) between treatments were measured for DMI. Average daily gain and GF responded quadratically (P < 0.05), with 10% crude glycerol resulting in the greatest values. In the second in vivo experiment, 100 crossbred steer calves (300 ± 2.0 kg) were assigned to 5 treatments: 0, 5, 10, 12.5, or 15% crude glycerol replaced corn grain. Calves were fed for a total of 135 d. No significant differences (P > 0.05) were measured in growth performance. For Exp. 3, one hundred heifer calves (270 ± 2.0 kg) were assigned to 4 treatments: 0, 5, 10, or 20% crude glycerol that replaced hay. No differences (P > 0.05) were measured in animal performance. We concluded that crude glycerol addition to a diet did not negatively affect ruminal fermentation, and addition of up to 20% in concentrate and hay-based diets should not affect performance or carcass characteristics.

The effect of residual feed intake classification on forage intake by grazing beef cows.

Although feed intake and efficiency differences in growing cattle of low and high residual feed intake (RFI) classification have been established, little is known about the difference in grazed forage intake between beef cows of known RFI classification. Two experiments were conducted using Hereford cows for which RFI had been determined as heifers using the GrowSafe 4000E feed intake system, after which heifers had been divided into thirds as low RFI, mid RFI, and high RFI. During Exp. 1, 2 replicates of low and high RFI cows (n = 7/replicate) in mid- to late-gestation were blocked to 1 of 4 non-endophyte-infected tall fescue paddocks (1.8 to 2.4 ha), which they grazed continuously for 84 d during summer. Using grazing exclosures, weekly rising plate meter readings, and forage harvests every 21 d, average forage DMI was calculated. Low and high RFI groups did not differ (P > 0.05) in BW change or BCS change over the trial (19.5 vs. 22.1 kg of BW gain and 0.11 vs. 0.10 BCS gain), but low RFI cows had a 21% numerically lower DMI than high RFI cows (12.4 vs. 15.6 kg/d; P = 0.23). The average area needed per paddock over the trial was similar for low and high RFI cows (1.71 vs. 1.82 ha; P = 0.35), and the average DM on offer over the trial was less for low RFI than for high RFI cows (4,215 vs. 4,376 kg; P = 0.06). During Exp. 2, 3 replicates of low and high RFI cows with their calves (n = 4 pair/replicate) strip-grazed stockpiled and early spring growth tall fescue paddocks (0.7 to 0.9 ha) for 60 d in late winter and early spring. Because of limiting forage availability and quality at trial initiation, cow-calf pairs were also fed 3.31 kg/pair of pelleted soyhulls daily. Pre- and post-grazed forage samples were harvested for 4 grazing periods, and forage growth was estimated using a growing degree days calculation and on-site weather station data. Performance did not differ (P > 0.05) between low and high RFI cows throughout the experiment (18.4 vs. 26.6 kg of BW gain and -0.04 vs. 0.15 BCS gain). Despite the utilization of forage offered being similar for low and high RFI cow-calf pairs (P > 0.05), low RFI cows and their calves had an 11% numerically lower DMI than high RFI pairs (12.5 vs. 14.1 kg/d; P = 0.12). We concluded that either no intake differences existed between low and high RFI cows or that current methodology and small animal numbers limited our ability to detect differences.

The relationship of feeding behavior to residual feed intake in crossbred Angus steers fed traditional and no-roughage diets.

Two studies were conducted to determine the relationship of feeding behavior to a phenotypic expression of residual feed intake (RFI), a measure of efficiency. In Exp. 1, a feedlot diet containing roughage was fed (traditional). In Exp. 2, a no-roughage diet was fed. Residual feed intake, a measure of feed efficiency, was calculated for both studies. In Exp. 1, six feed-efficient (low RFI) steers and six feed-inefficient steers (high RFI) were selected from a contemporary group of 80 steers, and feeding behaviors were analyzed. In Exp. 2, nine feed-efficient and eight feed-inefficient steers were selected from a contemporary group of 40 steers. There were no differences (P > 0.13) in initial or final BW or ADG between efficient and inefficient groups in either Exp. 1 or 2. In Exp. 1, DMI and average eating bouts daily differed (P < 0.001), with efficient steers consuming less feed and eating fewer times per day. In Exp. 2, efficient steers consumed less (P < 0.001) feed, and average eating bouts daily tended (P = 0.07) to be fewer in efficient animals. Limited differences were noted in feeding behavior between groups, with inefficient steers from both studies having a more variable eating pattern throughout the day. The average daily eating rate did not differ (P > 0.20) between groups in either experiment. The average number of days comprising a feeding pattern for both efficiency groups in Exp. 1 and 2 was found to be 2 to 3 d and multiples of 2 to 3 d. In Exp. 1, the feed intake pattern of efficient and inefficient steers changed once they reached a BW of approximately 391 and 381 kg, respectively. This occurred near d 47 for the efficient steers and near d 32 for inefficient steers. In Exp. 2, the feed intake pattern of both efficient and inefficient steers changed once they reached a BW of approximately 399 kg, which occurred on d 31 for the efficient steers and on d 33 for the inefficient steers. From the measured variables, there were no differences in growth and limited differences noted in feeding behavior between efficient and inefficient groups. The results of the trials suggest increased variability of feed intake throughout the day for inefficient animals.

The relationships among mitochondrial uncoupling protein 2 and 3 expression, mitochondrial deoxyribonucleic acid single nucleotide polymorphisms, and residual feed intake in Angus steers.

The objective of this study was to determine the relationships of uncoupling protein 2 and 3 expression, SNP of mitochondrial DNA, and residual feed intake (RFI) in Angus steers selected to have high or low RFI. Individual feed intake was measured via the GrowSafe feed intake system over a 3-mo period and used to calculate RFI, a measure of efficiency. Based on these calculations, 6 low- (average RFI = -1.57 kg) and 6 high- (average RFI = 1.66 kg) RFI steers were selected for further study. Blood was collected via jugular venipuncture 1 wk before slaughter for the isolation of mitochondrial DNA. The steers were then killed to collect LM for the measurement of uncoupling protein 2 and 3 mRNA and protein expression. Protein and mRNA expression of uncoupling protein 2 and 3 were determined by Western blotting and quantitative PCR, respectively. To determine SNP of mitochondrial DNA, total DNA was isolated from blood via standard phenol/chloroform extraction; fragments were amplified with PCR and sequenced with an automated nucleotide sequencer. Average daily gain and carcass composition were not different (P > 0.13) between the high- and low-RFI steers; however, ADFI by the high-RFI animals was 3.77 kg greater (P < 0.001) than the low-RFI animals. No difference (P > 0.55) was observed between the high- and low-RFI animals in their expression of uncoupling protein 2 or 3 mRNA or protein. On average 9.8 and 8.9 polymorphisms were found per mitochondrial genome for the low- and high-RFI steers, respectively. None of these polymorphisms were related to RFI. It seems that the expression of uncoupling protein 2 and 3 and mitochondrial DNA sequence are not related to RFI status.

Comparison of agar plate and real-time PCR on enumeration of Lactobacillus, Clostridium perfringens and total anaerobic bacteria in dog faeces.

AIMS: To compare agar plate and real-time PCR methods on enumeration of total anaerobic bacteria, Lactobacillus and Clostridium perfringens in dog faeces. METHODS AND RESULTS: Thirty-two faecal specimens from Labrador retriever dogs were used to compare agar plate and real-time PCR enumeration methods for Lactobacillus, C. perfringens and total anaerobic bacteria. Total anaerobic bacteria, C. perfringens and Lactobacillus of faeces were counted (as CFU g(-1) faeces) for 48-h incubation at 37 degrees C in an anaerobic gas chamber on genus-selective media. Total genomic DNA from samples was extracted by the QIAamp DNA stool mini kit. The quantification of DNA (as DNA copy per gram faeces) by real-time PCR was performed with a LightCycler system with the QuantiTect SYBR green PCR kit for PCR amplification. The results indicated that there was a significant correlation between CFU and DNA copy of Lactobacillus (R2 = 0.78, P < 0.01) and total anaerobic bacteria (R2 = 0.21, P < 0.05); but no correlation was found between CFU and DNA copy of C. perfringens. The regression equations for Lactobacillus and total anaerobic bacteria were log(DNA copy) = 0.83 x log(CFU) + 1.43 and log(DNA copy) = 1.62 x log(CFU) - 6.32 respectively. CONCLUSIONS: The real-time PCR method could be used to enumerate Lactobacillus within 2 days when compared with plating method which requires 5-6 days. SIGNIFICANCE AND IMPACT OF THE STUDY: The real-time PCR method and the primer set for Lactobacillus spp. harboured in the dog intestine can be used for rapid enumeration of lactobacilli and monitoring of the faecal Lactobacillus community.

The relationship between mitochondrial function and residual feed intake in Angus steers.

The objective of this study was to examine the relationship between mitochondrial function and residual feed intake in Angus steers. Individual feed intakes were recorded for a contemporary group of 40 steers via the GrowSafe feed intake system. Intakes were then used to calculate residual feed intake (RFI), a measure of efficiency. Based on these calculations, 9 low (RFI = -0.83) and 8 high (RFI = 0.78) RFI animals were selected for further study. Blood samples were collected via jugular venipuncture 1 wk before slaughter for the determination of plasma glucose and insulin concentrations. Tissue samples were taken from the LM from both the high and low RFI animals and mitochondria were isolated for measurement of oxygen consumption and hydrogen peroxide production. Average daily gain and carcass composition were not different between the high and low RFI steers; however, ADFI by the high RFI animals was 1.54 kg/d greater (P < 0.001) than for the low RFI animals. Low RFI steers exhibited a greater (P < 0.05) rate of state 2 and 3 respiration, respiratory control ratio, and hydrogen peroxide production than high RFI steers when provided with glutamate or succinate as a respiratory substrate. The acceptor control and adenosine diphosphate:oxygen ratios were not different between the 2 groups for either substrate. When hydrogen peroxide production was expressed as a ratio to respiration rate there was no difference between groups, signifying that electron leak was similar for both groups. Plasma glucose concentration was greater (P < 0.05) in the high RFI steers than in the low RFI steers; however, plasma insulin concentration was not different (P = 0.22) between the 2 groups. The ratio between plasma glucose and insulin concentration was similar (P = 0.88) between the 2 groups indicating no difference in glucose metabolism. The increased plasma glucose concentration observed in the high RFI steers was presumed to be the result of a greater feed intake by these animals. It seems that mitochondrial function is not different between the high and low RFI groups but rather the rate of mitochondrial respiration is increased in low RFI steers compared with high RFI steers.

Growth rate, body composition, and meat tenderness in early vs. traditionally weaned beef calves.

One hundred forty spring-born Angus x Gelbvieh and purebred Angus steers were selected for study as early weaned (EW; average age at weaning = 90 +/- 30 d) or traditionally weaned (TW; average age at weaning = 174 +/- 37 d) steers that were non-implanted or implanted (Synovex-S, Fort Dodge Animal Health, Overland Park, KS). Initially, steers were sorted by age, sire, and farm, and then allotted randomly in a 2 x 2 factorial arrangement of treatments of EW implanted (EWI), EW nonimplanted (EWN), TW implanted (TWI), or TW nonimplanted (TWN). Ultrasound measurements (US) of LM area (LMA), 12th rib fat thickness (US-BF), and marbling (US-M) were collected every 28 d during the time that steers were on feed. At 202 d of age, EW calves had larger US-LMA, US-BF, and BW than TW calves (37.9 vs. 32.3 cm2, 0.38 vs. 0.26 cm, and 271.6 vs. 218.9 kg, respectively; P < 0.001). At slaughter, EW calves had heavier HCW (290.4 vs. 279.7 kg, respectively; P < 0.05) and greater USDA marbling scores (51.25 vs. 46.26, respectively; P < 0.05) than TW calves; more EW steers graded USDA Choice or greater (P = 0.05). However, no differences were detected in BW (P = 0.15), LMA (P = 0.39), BF (P = 0.45), or liver abscess scores (P = 0.41). Twenty-four implanted steers were selected from the original group of 140 and sorted into two slaughter groups of 12. Twelve implanted steers from each weaning group, matched in slaughter BW but differing in age, were subsampled at slaughter to assess the effect of weaning age and chronological age on muscle tenderness. Younger animals had lower Warner-Bratzler shear force values (P < 0.001) than older calves after 14 d of postmortem aging; however, no differences were found in tenderness after 21 d of aging. Furthermore, there was greater variance (P < 0.001) in Warner-Bratzler shear force values among younger, EW steers vs. older, TW steers. These data provide evidence that early weaning of beef calves may be used as a tool to more effectively manage the cow-calf production system without compromising the quality of the offspring.

Fructooligosaccharide supplementation in the yearling horse: effects on fecal pH, microbial content, and volatile fatty acid concentrations.

Short-chain fructooligosaccharides (FOS) were supplemented to the diets of nine quarter horses ranging in age from 489 to 539 d with initial BW averaging 400.6 +/- 21.2 kg. The objectives of this study were to determine the effects of dietary FOS on the fecal responses in terms of pH, the microbial population, and VFA concentrations. The horses were used in a 3 x 3 replicated Latin square design, fed according to NRC requirements, and their individual diets were supplemented with no FOS (CON), 8 g of FOS/d (LOW), or 24 g of FOS/d (HIGH) over three 10-d feeding periods. On the last 3 d of each 10-d feeding period, a single fecal sample was collected between 0730 and 0930. Fecal pH decreased linearly (P = 0.01) from 6.48 with the CON diet to 6.38 with the HIGH diet, but there was no change (P = 0.19 for linear effect) in fecal consistency among treatments. A quadratic effect (P < 0.01) was observed for fecal Escherichia coli population, but no difference (P = 0.88 for linear effect) was found in fecal Lactobacilli enumeration among treatments. The presence of fecal Bifidobacteria was unable to be confirmed and was therefore not reported. Fecal acetate concentrations increased linearly (P = 0.03), with means of 2.13, 2.18, and 2.52 mg/g of wet feces for CON, LOW, and HIGH treatments, respectively. Similarly, fecal propionate concentrations increased linearly (P = 0.01), with means of 0.58, 0.64, and 0.73 mg/g for CON, LOW, and HIGH treatments, respectively. Fecal butyrate concentrations also increased linearly (P = 0.02), with means of 0.40, 0.46, and 0.54 mg/g for CON, LOW, and HIGH treatments, respectively. Total VFA (P = 0.01) and lactate (P = 0.02) concentrations increased linearly, with total VFA means of 3.47, 3.69, and 4.25 mg/g for CON, LOW, and HIGH treatments, respectively, and lactate means of 0.36, 0.41, and 0.47 mg/g for CON, LOW, and HIGH treatments, respectively. Supplementing FOS in diets fed to yearling horses altered fecal microbial populations, fecal VFA concentrations, and pH.

Level of supplemental protein does not influence the ruminally undegradable protein value.

Two experiments were conducted to determine whether elevating the percentage of ruminally undegradable protein (RUP) in the diet would influence the RUP value of the protein feedstuff. A single-effluent, continuous-culture study was designed to test the effect of RUP inclusion rate in the diet on ruminal degradability of the protein. Treatments consisted (DM basis) of a control diet with no supplemental protein, control + 2.5% bloodmeal (BM-L), control + 5% bloodmeal (BM-H), control + 4.45% soybean meal (SBM-L), and control + 8.89% soybean meal (SBM-H). Proteolytic activity and total VFA concentration were not affected (P = 0.73 and P = 0.13) by treatment. Within protein source, dietary RUP value was not affected (P = 0.94) by level of inclusion. When corrected for control diet RUP flow, the RUP value of the blood meal (BM) protein was higher (P = 0.01) than soybean meal (SBM); however, level of supplementation did not affect (P = 0.07) the RUP value of BM or SBM. In Exp. 2, 32 British x Continental crossbred steers (276 +/- 26.3 kg) were fed for 72 d to examine the effects of balancing the AA:energy ratio, using BM as a RUP source, on ADG, G:F, and lean tissue deposition. Diets were formulated to provide increasing levels of arginine, while ruminally degradable protein and energy were held constant. Four dietary treatments provided 0.5, 1, 1.5, and 2x the required amount of arginine, whereas the control diet had no BM included. Daily DMI averaged 7.6 kg/steer and did not differ (P = 0.71) among treatments. Steers gained an average of 1.9 kg/d and average G:F was 0.260, with no differences (P = 0.60 and P = 0.97, respectively) among treatments. There was no difference (P = 0.48) in the change in 12th-rib fat depth during the study; however, change in LM area was affected quadratically as the level of BM increased in the diet, with the greatest increase in LM area occurring in steers fed the 1x and 1.5x required arginine treatments. Balancing the AA:energy ratio did not affect G:F, DMI, or ADG; however, it increased deposition of lean in the LM quadratically. Level of dietary inclusion of BM as an RUP source does not affect its RUP value or efficacy of providing postruminal AA in growing steers.