Effects of grazing residues or feeding corn from a corn rootworm-protected hybrid (MON 863) compared with reference hybrids on animal performance and carcass characteristics

One grazing and two feeding experiments were conducted to compare the feeding value of corn residue or corn grain from a genetically enhanced corn hybrid (corn rootworm-protected; event MON 863) with nontransgenic, commercially available, reference hybrids. In Exp. 1, two 13.7-ha fields, containing corn residues from either a genetically enhanced corn root-worm-protected hybrid (MON 863), or a near-isogenic, nontransgenic control hybrid (CON) were divided into four equal-sized paddocks. Sixty-four steer calves (262 +/- 15 kg) were stratified by BW and assigned randomly to paddock to achieve a stocking rate of 0.43 ha/steer for 60 d, with eight steers per paddock and 32 steers per hybrid. A protein supplement was fed at 0.45 kg/steer daily (DM basis) to ensure protein intake did not limit performance. Steer ADG did not differ (P = 0.30) between steers grazing the MON 863 (0.39 kg/d) and CON (0.34 kg/d) corn residues for 60 d. The four treatments for the feeding experiments (Exp. 2 and 3) included two separate reference hybrids, the near-isogenic control hybrid (CON), and the genetically enhanced hybrid (MON 863) resulting in two preplanned comparisons of CON vs. MON 863, and MON 863 vs. the average of the reference hybrids (REF). In Exp. 2, 200 crossbred yearling steers (365 +/- 19 kg) were fed in 20 pens, with five pens per corn hybrid. In Exp. 3, 196 crossbred yearling steers (457 +/- 33 kg) were fed in 28 pens, with seven pens per corn hybrid. In Exp. 2, DMI and G:F did not differ (P > 0.10) between MON 863 and CON; however, steers fed MON 863 had a greater (P = 0.04) ADG than steers fed CON. Gain efficiency was greater (P = 0.05) for MON 863 cattle than for REF cattle in Exp. 2, but other performance measurements (DMI and ADG) did not differ (P > 0.10) between MON 863 and REF. No differences (P > 0.10) were observed for performance (DMI, ADG, and G:F) between MON 863 and CON or MON 863 and REF in Exp. 3. In terms of carcass characteristics, no differences (P > 0.10) were observed between MON 863 and CON, as well as MON 863 and REF, for marbling score, LM area, or 12th rib fat thickness in both Exp. 2 and 3. Overall, performance was not negatively affected in the corn residue grazing or feedlot experiments, suggesting the corn rootworm-protected hybrid (event MON 863) is similar to conventional, nontransgenic corn grain and residues when utilized by beef cattle.     

Effect of age at feedlot entry on performance and carcass characteristics of bulls and steers

Seventy Angus x Simmental calves (BW = 166.3 +/- 4.2 kg) were used in a 3 x 2 factorial arrangement to determine the effect of age at feedlot entry and castration on growth, performance, and carcass characteristics. At 82 d of age, steers were castrated. Calves were placed in the feedlot at 111 (early-weaned), 202, or 371 (yearling) d of age. Steers were implanted with Synovex-S followed 93 d later with Revalor-S. Calves were harvested on an individual basis when fat thickness was estimated to be 1.27 cm. During the feedlot phase, yearlings gained faster (P < 0.01) than calves placed in the feedlot at 202 or 111 d of age (1.88, 1.68, and 1.62 kg/d, respectively); however, from 111 d of age until harvest, ADG was greatest for early-weaned calves, intermediate for cattle placed in the feedlot at 202 d of age, and lowest for yearlings (1.62, 1.47, and 1.21 kg/d, respectively; P < 0.01). Early-weaned calves spent the most days in the feedlot, followed by calves placed in the feedlot at 202 d of age; yearlings spent the fewest days in the feedlot (221, 190, and 163 d, respectively; P < 0.01). Total DMI when in the feedlot was similar (P = 0.22) among age groups; however, daily DMI was lowest for early-weaned calves, intermediate for calves placed in the feedlot at 202 d of age, and the highest for yearlings (7.1, 8.1, 10.5 kg/ d, respectively; P < 0.01). Early-weaned calves were the most efficient, followed by calves placed in the feedlot at 202 d of age; yearlings were the least efficient (227, 207, 180 g gain/kg feed, respectively; P < 0.01). Weight at harvest (682, 582, 517 kg, respectively; P < 0.01) and hot carcass weight (413, 358, 314 kg, respectively; P < 0.01) were greatest for yearlings, intermediate for cattle placed in the feedlot at 202 d of age, and lowest for early-weaned calves. Early-weaned calves had the smallest longissimus area, followed by calves placed in the feed-lot at 202 d of age; yearlings had the largest longissimus area (77, 86, 88 cm2, respectively; P < 0.01). Calves placed in the feedlot at 111 and 202 d of age had lower yield grades (3.2, 3.1, 3.5, respectively; P < 0.04), and produced fewer select carcasses than yearlings (25, 13, 48%, respectively; P < 0.01). Bulls and implanted steers both had an ADG of 1.7 kg/d when in the feedlot; however, bulls had a greater (P < 0.09) hot carcass weight (370 vs 354 kg) and a larger (P < 0.01) longissimus area (85.8 vs 81.3 cm2) than steers. Earlier feedlot placement resulted in greater quality grades but lower carcass weights.     

The effects of active immunization against gnRH on testicular development, feedlot performance, and carcass characteristics of beef bulls

The objective was to determine the effects of a recombinant fusion protein anti-GnRH vaccine on testicular development, feedlot performance, and carcass quality of beef bulls. Crossbred beef bulls (n = 58, average weight 306 kg, 9 mo of age), were randomly allocated to two groups and received either an anti-GnRH vaccine (GnRH) or placebo (Control) by intramuscular injection on d 0, 56, and 112. There were group effects (P < 0.01; as a percentage of Control) on testicular weight (53%), daily sperm production (40%), and epididymal sperm reserves (16%). There were group x time interactions (P < 0.0001) for scrotal circumference and serum testosterone concentrations; at slaughter, bulls in the GnRH group had a smaller (P < 0.05) scrotal circumference (28.3 vs 33.9 cm) and lower (P < 0.05) serum testosterone concentrations (2.2 vs 8.6 ng/mL) than those in the Control group. Average daily gain, feed intake, and feed efficiency were not different between treatments during the backgrounding phase (d 0 to 84). During the finishing phase (d 98 to 182), ADG was greater (P < 0.05) for bulls in the Control group (1.69 vs 1.42 kg/d), as was carcass weight (6.9%; P < 0.01). However, GnRH bulls had numerically better feed efficiency (6.12 vs 7.08 kg DMI/kg gain; P < 0.23) and shear force values for ribeye that were 16% lower (P < 0.14) than Control bulls, warranting further investigation. Vaccinating bulls against GnRH suppressed testicular function, with growth and carcass characteristics similar to that expected with steers.     

Performance, growth, and maturity of Nellore bulls

The objectives of this study were to evaluate the dry matter intake (DMI), digestibility, average daily gain (ADG), microbial efficiency, empty body weight (EBW) gain, and body composition of Nellore bulls. Additionally, Nellore bull maturity was estimated, and the prediction equation for DMI, suggested by the Brazilian nutrient requirements system (BR CORTE; Azevêdo et al. 2010), was evaluated. Thirty-three Nellore bulls, with a mean initial weight of 259?±?25 kg and age of 14?±?1 months, were used in this study. Five animals were slaughtered at the beginning of the experiment (control group), and the remaining 28 were divided into 4 groups, each slaughtered at 42-day intervals. Their diet was composed of corn silage and concentrate (55:45). The power model was used to estimate muscle tissue, bone tissue, crude protein (CP), mineral matter (MM), and water present in the empty body, while the exponential model was used to estimate adipose tissue and ether extract (EE) present in the empty body. When expressed in kilograms per day, differences were observed (P?<?0.05) only for the intake of EE and neutral detergent fiber as a function of feedlot time periods. Although there was a difference in relation to nutrient intake, it did not affect (P?>?0.05) digestibility, with the exception of EE digestibility. The equation suggested by BR CORTE correctly estimates the DMI of Nellore bulls. ADG was not affected (P?>?0.05) by time spent in the feedlot. No differences were observed (P?>?0.05) for microbial efficiency; a mean value of 142 g microbial crude protein/kg total digestible nutrients was achieved. The muscle and bone tissues, CP, MM, and water present in the empty body increased as the animal grew, although at a lower rate. The adipose tissue and EE present in the empty body increased their deposition rate when the animal reached its mature weight. Maturity is defined as when an animal reaches 22 % EE in the empty body, which corresponds to 456 kg of EBW in Nellore bulls. Therefore, this study can conclude that the feedlot time period does not affect DMI, nutrient intake, ADG, or microbial efficiency. The equation proposed by BR CORTE (Azevêdo et al. 2010) correctly estimates the DMI of Nellore bulls, which reach maturity when an EBW of 456 kg is attained.     

Weaning,yearling, and preharvest ultrasound measures of fat and muscle area in steers,bulls, and heifers

Longissimus muscle area and fat thickness were measured following weaning, at yearling, and prior to harvest using real-time ultrasound, and corresponding carcass measurements were recorded 3 to 7 d following the preharvest scan in composite steers (n = 116, 447 +/- 19 d), bulls (n = 224, 521 +/- 11 d), and heifers (n = 257,532 +/- 12 d). Although fat deposition was limited in bulls and heifers from weaning to yearling, coefficients of variation ranged from 8.46 to 13.46% for muscle area, and from 27.55 to 38.95% for fat thickness, indicating that significant phenotypic variance exists across genders. Residual correlations, adjusted for the effects of year of birth, gender, and age at measurement, were high and ranged from 0.79 to 0.87 among ultrasound and carcass measures of muscle area. Residual correlations among ultrasound and carcass measures of fat thickness were also high, ranging from 0.64 to 0.86. Weaning and/or yearling ultrasound muscle area yielded similarly accurate predictions of carcass muscle area. Yearling ultrasound fat thickness accounted for 13% more of the observed variance in carcass fat thickness than the weaning ultrasound measure in single-trait prediction models. When both weaning and yearling ultrasound measures were used to predict carcass fat thickness, partial R2 values were 0.15 and 0.61 for weaning and yearling ultrasound fat thickness, respectively. The difference between predicted and carcass measures with respect to muscle area (fat thickness) was less than 6.45 cm2 (2.5 mm) for 80.2 to 88.9% (90.3 to 95%) of animals. Preharvest ultrasound measures yielded standard errors of prediction of less than 4.95 cm2 for muscle area and 1.51 mm or less for fat thickness. These results indicate that ultrasound measures taken between weaning and yearling provide accurate predictors of corresponding carcass traits in steers, bulls, and heifers.     

Genetic correlation estimates between ultrasound measurements on yearling bulls and carcass measurements on finished steers.

Carcass and growth measurements of finished crossbred steers (n = 843) and yearling ultrasound and growth measurements of purebred bulls (n = 5,654) of 11 breeds were analyzed to estimate genetic parameters. Multiple-trait restricted maximum likelihood (REML) was used to estimate heritabilities and genetic correlations between finished steer carcass measurements and yearling bull ultrasound measurements. Separate analyses were conducted to examine the effect of adjustment to three different end points: age, backfat thickness, and weight at measurement. Age-constant heritability estimates from finished steer measurements of hot carcass weight, carcass longissimus muscle area, carcass marbling score, carcass backfat, and average daily feedlot gain were 0.47, 0.45, 0.35, 0.41, and 0.30, respectively. Age-constant heritability estimates from yearling bull measurements of ultrasound longissimus muscle area, ultrasound percentage of intramuscular fat, ultrasound backfat, and average daily postweaning gain were 0.48, 0.23, 0.52, and 0.46, respectively. Similar estimates were found for backfat and weight-constant traits. Age-constant genetic correlation estimates between steer carcass longissimus muscle area and bull ultrasound longissimus muscle area, steer carcass backfat and bull ultrasound backfat, steer carcass marbling and bull ultrasound intramuscular fat, and steer average daily gain and bull average daily gain were 0.66, 0.88, 0.80, and 0.72, respectively. The strong, positive genetic correlation estimates between bull ultrasound measurements and corresponding steer carcass measurements suggest that genetic improvement for steer carcass traits can be achieved by using yearling bull ultrasound measurements as selection criteria.     

Evaluation of sulfur content of dried distillers grains with solubles in finishing diets based on steam-flaked corn or dry-rolled corn

Crossbred yearling steers (n=80; 406 ± 2.7 kg of BW) were used to evaluate the effects of S concentration in dried distillers grains with solubles (DDGS) on growth performance, carcass characteristics, and ruminal concentrations of CH(4) and H(2)S in finishing steers fed diets based on steam-flaked corn (SFC) or dry-rolled corn (DRC) and containing 30% DDGS (DM basis) with moderate S (0.42% S, MS) or high S (0.65% S, HS). Treatments consisted of SFC diets containing MS (SFC-MS), SFC diets containing HS (SFC-HS), DRC diets containing MS (DRC-MS), or DRC diets containing HS (DRC-HS). High S was achieved by adding H(2)SO(4) to DDGS. Ruminal gas samples were analyzed for concentrations of H(2)S and CH(4). Steers were fed once daily in quantities that resulted in traces of residual feed in the bunk the following day for 140 d. No interactions (P ≥ 0.15) between dietary S concentration and grain processing were observed with respect to growth performance or carcass characteristics. Steers fed HS diets had 8.9% less DMI (P < 0.001) and 12.9% less ADG (P=0.006) than steers fed diets with MS, but S concentration had no effect on G:F (P=0.25). Cattle fed HS yielded 4.3% lighter HCW (P = 0.006) and had 16.2% less KPH (P=0.009) than steers fed MS. Steers fed HS had decreased (P=0.04) yield grades compared with steers fed MS. No differences were observed among treatments with respect to dressing percentage, liver abscesses, 12th-rib fat thickness, LM area, or USDA quality grades (P ≥ 0.18). Steers fed SFC had less DMI (P < 0.001) than steers fed DRC. Grain processing had no effect (P > 0.05) on G:F or carcass characteristics. Cattle fed HS had greater (P < 0.001) ruminal concentrations of H(2)S than cattle fed MS. Hydrogen sulfide concentration was inversely related (P ≤ 0.01) to ADG (r=-0.58) and DMI (r=-0.67) in cattle fed SFC, and to DMI (r=-0.40) in cattle fed DRC. Feeding DDGS that are high in dietary S may decrease the DMI of beef steers and compromise the growth performance and carcass characteristics of feedlot cattle.     

Effects of water sulfate concentration on performance, water intake, and carcass characteristics of feedlot steers.

Two hundred forty single-source, cross-bred steers (304 kg) were used to evaluate the effects of various water sulfate concentrations on performance, water intake, and carcass characteristics of feedlot steers. Cattle were stratified by weight and assigned within weight blocks to five water treatments. Averaged over time, actual water sulfate concentrations (+/- SEM) were 136.1 (+/- 6.3), 291.2 (+/- 15.3), 582.6 (+/- 16.9), 1,219.2 (+/- 23.7), and 2,360.4 (+/- 68.2) mg/L, respectively. Weather-related data were recorded. Increasing water sulfate concentration resulted in linear decreases in ADG (P < 0.01) and gain:feed ratio (P < 0.01) and a quadratic effect on water intake (P = 0.02) and tended to quadratically increase then decrease DMI (P = 0.13). Sulfate x period interactions were evident for DMI (P = 0.01), ADG (P < 0.01), and feed efficiency (P < 0.01). Time had quadratic effects on DMI, water intake, ADG, and feed efficiency (P < 0.01 for all models). Increasing water sulfate concentration resulted in linear decreases in final weight, hot carcass weight, and dressing percentage, a linear increase in longissimus muscle area, and a quadratic effect on fat thickness over the 12th rib and predicted yield grade (P < 0.05 for all dependent variables). Mean daily temperature explained 25.7% of the observed variation in water intake. Other factors that explained a significant (P < 0.01) amount of variation in water intake were BW, DMI, water sulfate concentration, barometric pressure, wind speed, and humidity. High water sulfate concentrations had a significant and deleterious effect on performance and carcass characteristics of feedlot steers. Increasing the sulfate concentration in water may have resulted in a functional water restriction early in the trial when ambient temperatures were greatest. However, toward the latter stages of the trial, cattle supplied higher-sulfate water had higher ADG and FE. These improvements later in the trial may represent compensatory gain associated with decreased ambient temperature and water requirements. Averaged over time, a water sulfate concentration of greater than 583 mg/L, equivalent to 0.22% of the diet, decreased feedlot performance.     

Net energy of ensiled wet corn gluten feed in corn silage diets for finishing steers.

Two trials were conducted to determine the NE value of ensiled wet corn gluten feed (WCGF) in corn silage finishing diets for beef cattle. In Trial 1, 96 Angus-crossbred yearling steers were fed corn silage-based diets containing 0, 20, 40, or 60% ensiled WCGF. Increased dietary WCGF resulted in improved DMI (linear, P less than .05), ADG (linear; P less than .05), and feed/gain (linear, P less than .05). Levels of WCGF had no (P greater than .05) effect on fat thickness, marbling, quality grade, carcass protein, and carcass fat. In Trial 2, four Angus-crossbred yearling steers were used in a 4 x 4 Latin square design to determine the effect of feeding 0, 20, 40, or 60% WCGF on DE and ME values. Level of WCGF had no (P greater than .05) effect on dietary DE and ME values. Regression equations were developed for predicting NEm (Y = 1.51 + .0009X; R2 = .22) and NEg (Y = 1.04 + .0028X; R2 = .35) in which Y = predicted diet NE values in megacalories/kilogram and X = percentage of dietary WCGF. The NEg value increased .06 Mcal/kg for each 20% increase in WCGF. Predicted NEm and NEg values for WCGF are 1.60 and 1.32 Mcal/kg, respectively.     

Alternative Ultrasound Predictors of Beef Carcass Longissimus Muscle Area

Longissimus width and depth were measured using ultrasound in steers (n = 174), bulls (n = 323), and heifers (n = 347) at yearling and prior to harvest. Yearling and preharvest muscle dimensions and carcass muscle area of bulls were largest (P<0.01). Steers had wider and deeper (P<0.01) longissimus than heifers at yearling; however, preharvest muscle width and depth and carcass muscle area were greater (P<0.01) for heifers. From yearling to harvest, muscle width of bulls and heifers increased at a similar rate, which was greater (P<0.01) than that of steers. Significant (P<0.01) differences existed for muscle depth increase from yearling to harvest, where bulls had the highest deposition rates, heifers had intermediate rates, and steers had the lowest deposition rates. Correlations of carcass muscle area with muscle depth were large and positive (0.52 to 0.81) and slightly larger than correlations with muscle width (0.51 to 0.74). Muscle depth was the best single predictor of carcass muscle area; however, two-trait prediction models including both muscle width and depth were superior to single-trait prediction models. At yearling (preharvest), predicted and carcass muscle areas differed by more than 9.68 cm² for less than 2% (5%) of steers and heifers and less than 7% (4%) of bulls. Further, yearling and pre-harvest carcass muscle area predictions were within 4.84 cm² of carcass measurements for approximately 54 to 65% of all animals, respectively. These results indicate that ultrasound muscle width and depth may be alternative predictors of carcass muscle area and may be useful in selection of potential replacements.     

Influence of steam-peeled potato-processing waste inclusion level in beef finishing diets: effects on digestion, feedlot performance, and meat quality

Inclusion of potato-processing waste (PW) from the frozen potato products industry in high-grain beef cattle finishing diets was evaluated in two studies. In a randomized complete block design, 125 crossbred yearling heifers (365 +/- 0.3 kg initial BW; five pens per treatment; five heifers per pen) were used to evaluate PW level on feedlot performance and meat quality. Heifers were fed for 85 (two blocks) or 104 d (three blocks). In a digestion study, four ruminally, duodenally, and ileally cannulated Holstein steers (474.7 +/- 26.6 kg initial BW) were used in a 4 x 4 Latin square design to evaluate effects of PW level on ruminal fermentation, site of digestion, and microbial protein synthesis. The control diet for both studies contained 80% corn, 10% alfalfa hay, 5% concentrated separator by-product (CSB), and 5% supplement (DM basis). Potato waste replaced corn and separator by-product (DM basis) in the diet at 0, 10, 20, 30, and 40% in the feedlot study, and at 0, 13, 27, and 40% in the digestion study. In the feedlot study, DMI decreased (linear; P = 0.007) with increasing inclusion of PW. Increasing PW decreased ADG and feed efficiency from 0 to 30% and then increased at 40% (quadratic; P < 0.01). Calculated dietary NEg concentrations did not differ among treatments (P = 0.18). Hot carcass weight decreased as PW increased from 0 to 30% and then increased at 40% PW (cubic; P < 0.01). Fat thickness and longissimus muscle area decreased with increasing PW (linear; P < 0.05). Level of PW did not affect marbling or liver scores (P > 0.30). No difference (P > 0.20) was observed for Warner-Bratzler shear force at 0, 10, 20, and 30% PW levels; however, 40% PW resulted in lower (P = 0.05) shear force values. Taste panel scores for juiciness and flavor intensity did not differ with increasing PW (P > 0.30). Steaks from cattle fed 0% were scored less tender than 10 and 40% PW (cubic; P < 0.05). In the digestion study, DMI decreased (quadratic; P < 0.01) with increasing PW. Ruminal pH and total VFA concentration increased (linear; P < 0.05) and true N disappearance from the stomach complex and apparent total-tract N disappearance decreased with increasing level of PW (linear; P < 0.01). Starch intake and ruminal disappearance decreased with increasing level of PW (quadratic; P < 0.05). Inclusion of PW decreased feedlot performance, with little effect on carcass characteristics or meat quality. Optimal inclusion of PW in finishing diets may depend on the cost of transportation and other dietary ingredients.     

Evaluation of the National Research Council (1996) dry matter intake prediction equations and relationships between intake and performance by feedlot cattle

Intake prediction equations of NRC based on initial BW and dietary NE(m) concentration were evaluated with a commercial feedlot database consisting of 3,363 pen means collected from 3 feedlots over a 4-yr period. The DMI predicted by NRC equations had significant (P < 0.01) mean and linear biases across the range of observed DMI in the database. In general, DMI was overpredicted by the NRC equations. Adjustment of the NE(m)-based prediction by use of a 12% increase in NE(m) concentration and a 4% decrease in predicted DMI associated with the feeding of monensin decreased bias. Dry matter intake predicted by the NE(m)-based monensin-adjusted, NE(m)- based, and initial BW equations explained 67, 66, and 64% of the variation in observed DMI, respectively. Relationships between ADG and G:F with DMI as a percentage of BW and NE(g) intake also were examined in the same data set. Across the wide range of average shrunk BW in the database (334.4 to 548.0 kg), ADG was positively related to DMI as a percentage of BW (P < 0.01); however, this relationship was not strong (r(2) = 0.17). Likewise, G:F showed little relationship with DMI as a percentage of BW (P < 0.01; r(2) = 0.05). By accounting for differences in maintenance energy requirements of pens with varying average BW, NE(g) intake was strongly and positively related to ADG (linear and quadratic, P < 0.01; R(2) = 0.70); however, G:F showed little relationship with NE(g) intake (P = 0.02; r(2) = 0.01). Our evaluations with measurements of DMI by cattle in commercial feedlots indicated the shortcomings of current published equations for predicting DMI and suggest the need for development of new equations with improved accuracy and precision. Furthermore, our data indicate that increasing NE(g) in- take increased ADG in a quadratic manner but did not affect G:F by pens of cattle in feedlots. These findings suggest a diminishing returns effect of energy intake on energy retention.     

Endocrine,growth, and carcass characteristics of bulls immunized against luteinizing hormone-releasing hormone fusion proteins

This study evaluated the effectiveness of a LHRH fusion protein vaccine on endocrine changes, feedlot performance, and carcass quality of bulls compared with steers and hormone-implanted steers. Crossbred bulls (n = 30; mean weight, 179 +/- 4 kg; mean age, 130 +/- 2 d) were randomly assigned to three treatment groups: 1) castrated (castrated; n = 10); 2) castrated-implanted with trenbolone acetate (implanted; n = 10); and 3) immunized against a cocktail of recombinant fusion proteins, ovalbumin-LHRH-7 and thioredoxin-LHRH-7 (immunized bulls; n = 10). Blood was collected every 2 wk to evaluate antibody and hormone concentrations. Serum LHRH antibodies (P < 0.001) were detected in animals of the immunized group, which had reduced serum LH concentrations (P < 0.001) compared with the castrated groups and serum FSH concentrations, which did not decrease but were significantly different when compared with castrated and implanted animals. Serum testosterone concentrations in the immunized bulls were not different from the two castrated groups (P > 0.05) by d 60 after primary immunization. Initial mean scrotal circumference of the immunized bulls was 18.0 +/- 0.6 cm on d 0 and increased to 22.6 +/- 1.3 cm by d 310. No differences (P > 0.05) in ADG were observed among treatment groups. Immunized animals had an intermediate BW gain (P > 0.05) when compared with the castrates, whereas the castrated groups differed (P < 0.05) from each other. Carcass characteristics were similar (P < 0.05) among the three groups. Vaccinating bulls against a LHRH fusion protein cocktail suppressed LH and testosterone, which led to reduced testicular development and no bullock carcasses. Growth and carcass characteristics of the immunized animals were similar to the steers.     

Effects of feeding polyclonal antibody preparations on rumen fermentation patterns, performance, and carcass characteristics of feedlot steers

In a previous study, preparations of polyclonal antibodies (PAP) against Fusobacterium necrophorum (PAP-Fn) or Streptococcus bovis (PAP-Sb) were successful in decreasing ruminal counts of target bacteria and increasing ruminal pH in steers fed high-grain diets. The objective of this study was to evaluate the effects of feeding PAP-Fn or PAP-Sb on performance, carcass characteristics, and ruminal fermentation variables of feedlot steers. In Exp. 1, during 2 consecutive years, 226 or 192 Angus and Angus crossbred steers were fed a high-grain diet containing either PAP-Sb or PAP-Fn, or both. When measured on a BW basis, steers fed only PAP-Sb had a greater G:F (P < 0.05) than those fed no PAP. Nevertheless, when both PAP were fed, feed efficiency was similar (P > 0.10) to steers fed no PAP or only PAP-Sb. Steers receiving PAP-Fn (alone or in combination with PAP-Sb) had a decreased (P < 0.05) dressing percentage. Steers receiving PAP-Fn (alone or in combination with PAP-Sb) had a decreased severity of liver abscess (P < 0.05). No differences (P > 0.10) were observed in any other carcass characteristics. In Exp. 2, sixteen ruminally cannulated Angus crossbred steers (BW = 665 +/- 86 kg) were fed a high-grain diet containing either PAP-Sb or PAP-Fn, or both. Feeding only PAP-Fn or PAP-Sb for 19 d decreased (P < 0.05) ruminal counts of S. bovis when compared with steers fed both or no PAP. The ruminal counts of F. necrophorum in steers fed PAP-Fn alone or in combination with PAP-Sb were decreased by 98% (P < 0.05) after 19 d, when compared with the counts in control steers. Mean daily ruminal pH was greater (P < 0.05) in steers fed both PAP when compared with feeding either or no PAP. Ruminal pH in the first 4 h after feeding was greater (P < 0.05) for steers receiving PAP-Fn alone or in combination with PAP-Sb. Steers receiving either PAP alone or in combination had less (P < 0.05) ruminal NH(3)-N concentrations in the first 4 h after feeding when compared with those of control steers. Polyclonal antibody preparations against S. bovis were effective in enhancing G:F of steers fed high-grain diets, but dressing percentage was decreased. Mechanisms of enhancement of G:F remain unknown but may be related to changes in ruminal counts of target bacteria and associated effects on ruminal fermentation products.     

A fenbendazole oral drench in addition to an ivermectin pour-on reduces parasite burden and improves feedlot and carcass performance of finishing heifers compared with endectocides alone

Two studies utilizing 1,862 yearling heifers were conducted to determine the effects of a fenbendazole oral drench in addition to an ivermectin pour-on (SG+IVPO), compared with an ivermectin pour-on (IVPO) or a doramectin injectable (DMX) alone, on parasite burden, feedlot performance, and carcass merit of feedlot cattle. In the first study, heifers receiving the SG+IVPO had fewer (P = 0.02) cattle retreated for disease and 73% fewer (P = 0.06) worm eggs per fecal sample 98 d after treatment than heifers treated with IVPO. Heifers treated with SG+IVPO consumed more DM, had greater ADG, were heavier at slaughter, and had heavier carcasses than IVPO-treated heifers (P < 0.05). Heifers treated with SG+IVPO also had more (P = 0.07) carcasses grading USDA Prime or Choice than IVPO-treated heifers. In the second study, heifers treated with SG+IVPO had fewer (P < 0.01) worm eggs per fecal sample 35 d after treatment and had fewer numbers of adult and larval Cooperia and Trichostrongylus spp. in the small intestine at slaughter (P < 0.10) compared with heifers treated with DMX. Heifers treated with SG+IVPO consumed more DM, were heavier at slaughter, and had heavier carcasses than DMX-treated heifers (P < 0.01). The SG+IVPO-treated heifers also had greater ADG (P < 0.10). The broad-spectrum effectiveness of a combination of a fenbendazole oral drench and an ivermectin pour-on reduced parasite burden and increased feed intake, ADG, and carcass weight in feedlot heifers compared with treatment with an endectocide alone.     

Calcium salts of fatty acids with varying fatty acid profiles in diets of feedlot-finished Bos indicus bulls: impacts on intake,digestibility, performance,and carcass and meat characteristics

We hypothesized that the inclusion of calcium salts of fatty acid (CSFA) into the diets and the fatty acid (FA) profile of the supplements would impact performance and meat characteristics of Bos indicus bulls. Hence, the objective was to evaluate the effects of CSFA profiles on intake, body weight (BW), carcass, and meat characteristics of feedlot-finished B indicus bulls. Fifty-three Nellore bulls [initial BW 315 ± 5.9 kg and 20 ± 2 mo] were used. At the beginning, 6 bulls were randomly chosen and slaughtered for determination of their BW composition, and the remaining 47 bulls were evaluated during a 140-d experimental period. The bulls were placed in individual pens, blocked according to initial BW and randomly allocated to 1 of the 3 following treatments: (1) control diet containing sugarcane bagasse, ground corn, citrus pulp, peanut meal, and mineral–vitamin mix (CON), (2) CON with the addition of 3.3% of CSFA from soybean oil (CSO), or (3) CON with the addition of a mixture of 3.3% of CSFA from palm, soybean, and cottonseed oils (CPSCO). Diets were offered ad libitum and formulated to be isonitrogenous. Bulls supplemented with CSFA had a greater (P < 0.01) final BW, dry matter intake, average daily gain (ADG), feed efficiency (FE), and FA intake vs. CON. Among carcass parameters, CSFA-supplemented bulls had greater (P < 0.01) carcass ether extract concentration vs. CON bulls. When the CSFA profile was evaluated (CSO vs. CPSCO), CPSCO bulls had a better (P ≤ 0.03) FE, carcass ADG, and hot carcass weight (HCW) vs. CSO bulls. The FA intakes differed among CSFA treatments, as the total saturated, palmitic, and oleic FA intakes were greater for CPSCO (P < 0.01), whereas lower intakes of total unsaturated and polyunsaturated FA (P < 0.01) were observed for CPSCO vs. CSO. Samples from the Longissimus muscle contained greater palmitoleic (P = 0.01) and reduced linoleic (P = 0.02) FA concentrations in CSFA-supplemented bulls vs. CON bulls. In agreement with the FA intakes, CPSCO-supplemented bulls had a greater (P ≤ 0.05) unsaturated FA concentration vs. CSO in Longissimus muscle. In summary, CSFA supplementation improved the performance of finishing B. indicus bulls vs. CON. Moreover, the inclusion of CSFA from palm, soybean, and cottonseed oil benefited the FE, carcass ADG, and HCW compared with the inclusion of CSFA from soybean oil, demonstrating the potential of specific FA for improving the performance and meat quality of B. indicus bulls.     

Effects of wet corn gluten feed and roughage levels on performance, carcass characteristics, and feeding behavior of feedlot cattle

Two experiments were conducted to evaluate the effects of feeding different levels of wet corn gluten feed (WCGF) and dietary roughage on performance, carcass characteristics, and feeding behavior of feedlot cattle fed diets based on steam-flaked corn (SFC). In Exp. 1, crossbred steers (n = 200; BW = 314 kg) were fed 4 dietary treatments (DM basis): a standard SFC-based diet containing 9% roughage (CON) and 3 SFC-based diets containing 40% WCGF, with either 9, 4.5, or 0% roughage. A linear (P = 0.04) increase in final BW and DMI (P < 0.01) was observed in diets containing WCGF as dietary roughage increased. Steers fed WCGF and higher levels of roughage had greater (P = 0.01) ADG than steers fed lower levels of roughage. Steers fed the CON diet had lower (P = 0.04) daily DMI and greater (P = 0.03) G:F than those fed WCGF. Most carcass characteristics of steers fed CON did not differ (P > 0.10) from those of steers fed WCGF. Based on feed disappearance and visual scan data, consumption rate did not differ (P > 0.10) among treatments; however, feeding intensity (animals present at the bunk after feeding) was greater for steers fed CON (P < 0.01) than for steers fed WCGF. In Exp. 2, yearling crossbred steers (n = 1,983; BW = 339 kg) were fed 4 dietary treatments (DM basis): a standard SFC-based control diet that contained 9% roughage (CON) and 3 SFC-based diets containing either 20% WCGF and 9% roughage or 40% WCGF with 9 or 4.5% roughage. Steers fed the CON diet tended to have lower final BW (P = 0.14), ADG (P = 0.01), and DMI (P < 0.01) than steers fed diets containing WCGF. Steers fed the 20% WCGF diet had greater (P = 0.08) G:F than steers fed the 40% WCGF diets. With 40% WCGF, increasing roughage from 4.5 to 9% decreased (P < 0.01) G:F and increased (P = 0.06) DMI. Gain efficiency was improved (P < 0.01) for steers fed CON vs. those fed diets containing WCGF, whereas HCW (P = 0.02) and dressing percentage (P < 0.01) were greater for steers fed WCGF. Percentage of cattle grading USDA Choice was greater (P = 0.02) for cattle fed WCGF. Results suggest that replacing SFC with up to 40% WCGF increased ADG and decreased G:F when 4.5 to 9.0% roughage was supplied. More CON steers were present at the feed bunk during the first hour after feeding than WCGF steers, suggesting that including WCGF at 40% of the diet affected feeding behavior.     

Circulating leptin and its muscle gene expression in Nellore cattle with divergent feed efficiency

Background: Leptin has a strong relation to important traits in animal production, such as carcass composition,feed intake, and reproduction. It is mainly produced by adipose cells and acts predominantly in the hypothalamus.In this study, circulating leptin and its gene expression in muscle were evaluated in two groups of young Nellore bulls with divergent feed efficiency. Individual dry matter intake(DMI) and average daily gain(ADG) of 98 Nellore bulls were evaluated in feedlot for 70 d to determinate the residual feed intake(RFI) and select 20 animals for the high feed efficient(LRFI) and 20 for the low feed efficient(HRFI) groups. Blood samples were collected on d 56 and at slaughter(80 d) to determine circulating plasma leptin. Samples of Longissimus dorsi were taken at slaughter for leptin gene expression levels.Results: DMI and RFI were different between groups and LRFI animals showed less back fat and rump fat thickness,as well as less pelvic and kidney fat weight. Circulating leptin increased over time in all animals. Plasma leptin was greater in LRFI on 56 d and at slaughter(P = 0.0049). Gene expression of leptin were greater in LRFI animals(P = 0.0022) in accordance with the plasma levels. The animals of the LRFI group were leaner, ate less, and had more circulating leptin and its gene expression.Conclusion: These findings demonstrated that leptin plays its physiological role in young Nellore bulls, probably controlling food intake because feed efficient animals have more leptin and lower residual feed intake.     

Effects of 2-hydroxy-4-(methylthio)-butanoic acid on performance and carcass characteristics of finishing beef cattle and on fermentation in continuous culture

Three experiments were conducted to evaluate the effects of feeding 2-hydroxy-4- (methylthio)-butanoic acid (HMTBA) on performance and carcass characteristics of feedlot cattle and on microbial fermentation in a continuous-culture system. In Exp. 1, 160 crossbred steers (initial BW = 385 +/- 10.3 kg) were assigned to 4 treatments consisting of control (0% HMTBA) or 3 diets containing HMTBA (0.069, 0.137, and 0.204%; DM basis) in a randomized complete block design. As the percent of HMTBA increased in the diet, final BW (P = 0.069), final BW adjusted to a constant dressing percent (P = 0.063), and overall ADG (P = 0.099) tended to decrease linearly. Overall DMI decreased linearly (P < or = 0.006) with increasing HMTBA dose. No differences (P > or = 0.10) were noted for carcass characteristics, except for a tendency (P = 0.078) for a linear increase in the percentage of cattle grading USDA Choice with increasing HMTBA dose. In Exp. 2, 80 crossbred steers (initial BW = 450 +/- 17 kg) in a randomized complete block design were assigned to a control (0% HMTBA) diet or to a diet in which the concentrations of HMTBA were gradually increased from 0.036 to 0.212% of DM over a 50-d period. The HMTBA-containing diet tended to decrease DMI (P = 0.132), but G:F (P = 0.319) for the overall feeding period, carcass measurements, and USDA quality grade (P > or = 0.149) did not differ between treatments. In Exp. 3, continuous culture fermenters (n = 5/treatment) were used to determine the effects of HMTBA (control vs. 0.24% HMTBA) on microbial fermentation. No differences (P > or = 0.31) were detected between treatments in ruminal OM digestibility, microbial N synthesis, pH, ammonia, molar proportions of VFA, or effluent concentration of selected long-chain fatty acids. These results suggest that HMTBA decreased DMI by feedlot steers fed a steam-flaked corn-based diet in a dose-dependent manner; however, gradually increasing the dose over time seemed to moderate effects on DMI. No major changes in microbial fermentation in continuous culture were observed with HMTBA at 0.24% of dietary DM, suggesting effects of HMTBA on DMI were not likely associated with changes in ruminal digestion or fermentation.     

Effect of processing flax in beef feedlot diets on performance, carcass characteristics, and trained sensory panel ratings

To assess the effects of flax addition and flax processing on feedlot performance and carcass characteristics, 128 yearling beef heifers (360 +/- 14 kg of initial BW) were blocked by weight and assigned randomly to feedlot diets that included no flax (control), whole flax (WHL), rolled flax (RLD; 1,300 microm), or ground flax (GRD; 700 microm). Heifers were fed a growth diet (31% corn, 30% corn silage, 18% barley malt pellets, 14% alfalfa, 4% linseed meal, and 3% supplement; DM basis) for 56 d, after which they were adapted to a finishing diet (79% corn, 7% corn silage, 7% alfalfa, 4.75% linseed meal, and 2.25% supplement; DM basis). In WHL, RLD, and GRD, flax replaced all linseed meal and partially replaced corn at 8% of diet DM. All diets provided 0.5 mg of melengestrol acetate, 2,000 IU of vitamin E, and 232 mg of monensin per heifer daily. Cattle were slaughtered by block after 96, 97, and 124 (2 blocks) d on feed. At 24 h postmortem, carcass data were collected, and a portion of the loin was removed, vacuum-packaged, and aged for 14 d. After aging, 2 steaks were removed from each loin for Warner-Bratzler shear force measurement, sensory panel evaluation, and fatty acid analysis (approximately 100 g of muscle was collected). Flax inclusion (WHL, RLD, and GRD vs. control) did not affect DMI (P = 0.79), fat thickness over the 12th rib (P = 0.32), or LM area (P = 0.23). Flax inclusion increased ADG (P = 0.006), G:F (P = 0.006), and USDA yield grade (P = 0.01). Flax processing (RLD and GRD vs. WHL) increased ADG (P = 0.05), G:F (P = 0.08), and apparent dietary NEm and NEg (P = 0.003). Muscle from heifers fed flax had greater phospholipid 18:3n-3 (P < 0.001), 20:5n-3 (P < 0.001), 22:5n-3 (P < 0.001), and 22:6n-3 (P = 0.02) fractions, and greater neutral lipid 18:3n-3 (P < 0.001). Feeding 8% flax to feedlot heifers increased gain and efficiency, and processing flax increased available energy and resulted in increased efficiency of gain. Feeding 8% flax also increased levels of n-3 fatty acids in fresh beef.