The effects of varying bulk density of steam-flaked corn (SFC) in diets containing wet corn gluten feed (WCGF; Sweet Bran; Cargill Corn Milling, Blair, NE) have not been defined. In Exp. 1, yearling steers (n = 108; initial BW = 367 ± 1.18 kg) were housed in 27 pens (4 steers/pen) and received 1 of 3 different SFC bulk density treatments in a randomized complete block design. Bulk density treatments were 283, 335, or 386 g/L SFC in diets containing 25% WCGF (% of DM). Steers were fed once daily to provide ad libitum access to feed for an average of 163 d. For a 5-d period before d 70 of the experiment, DMI was measured, and fecal samples were collected from each pen for measurement of nutrient digestibility using dietary acid insoluble ash as a marker. Varying bulk densities of SFC did not affect (P ≥ 0.233) overall DMI, ADG, or G:F on a live- or carcass-adjusted basis. Dressing percent and LM area increased linearly (P ≤ 0.05) as bulk density increased, but other carcass traits were not affected by treatments. Intake of DM, OM, and CP during the 5-d digestion phase did not differ among bulk densities; however, starch intake increased linearly (P = 0.004) as bulk density of SFC increased. Digestibility of DM, OM, and CP tended (P ≤ 0.065) to decrease and starch digestibility decreased (P = 0.002) linearly as bulk density of SFC increased. In Exp. 2, a 3 × 3 Latin square design was used for collection of ruminal fluid from 3 ruminally cannulated Jersey steers adapted to the same diets used in Exp. 1. Bulk density did not affect NH3 concentrations, VFA molar proportions, ruminal fluid osmolality, and IVDMD of the diets. Total gas production increased linearly (P = 0.003) as bulk density of SFC increased from 283 to 335 g/L, but it decreased (P = 0.002) at 386 g/L. Present data suggest that bulk density can be increased up to 386 g/L in finishing diets containing 25% (DM basis) WCGF without affecting cattle performance and with limited effects on ruminal fermentation; however, digestibility of starch seemed to be affected negatively by increased bulk density in these diets.

The NRC (1996) equation for predicting DMI by growing-finishing beef cattle, which is based on dietary NEm concentration and average BW(0.75), has been reported to over- and underpredict DMI depending on dietary and animal conditions. Our objectives were to 1) develop broadly applicable equations for predicting DMI from BW and dietary NEm concentration and 2) evaluate the predictive value of using NE requirements and dietary NE concentrations to determine the DMI required (DMIR) by feedlot cattle. Two new DMI prediction equations were developed from a literature data set, which represented treatment means from published experiments from 1980 to 2011 that covered a wide range of dietary NEm concentrations. Dry matter intake predicted from the 2 new equations, which were based on NEm concentration and either the ending BW for a feeding period or the DMI per unit of average BW (End BW and DMI/BW, respectively), accounted for 61 and 58% of the variation in observed DMI, respectively, vs. 48% for the 1996 NRC equation. When validated with 4 independent data sets that included 7,751 pen and individual observations of DMI by animals of varying BW and feeding periods of varying length, DMI predicted by the 1996 NRC equation, the End BW and DMI/BW equations, and the DMIR method accounted for 13.1 to 82.9% of the variation in observed DMI, with higher r(2) values for 2 feedlot pen data sets and lower values for pen and individual data sets that included animals on lower-energy, growing diets as well as those in feedlot settings. The DMIR method yielded the greatest r(2) values and least prediction errors across the 4 data sets; however, mean biases (P < 0.01) were evident for all the equations across the data sets, ranging from as high as 1.01 kg for the DMIR method to -1.03 kg for the 1996 NRC equation. Negative linear bias was evident in virtually all cases, suggesting that prediction errors changed as DMI increased. Despite the expanded literature database for equation development, other than a trend for lower standard errors of prediction with the DMI/BW equation, the 2 new equations did not offer major advantages over the 1996 NRC equation when applied to the validation data sets. Because the DMIR approach accounted for the greatest percentage of variation in observed DMI and had the least root mean square error values in all data sets evaluated, this approach should be considered as a means of predicting DMI by growing-finishing beef cattle.

Two hundred twenty-four steers (initial BW = 363 ± 1.57 kg) were used in a 2 × 3 + 1 factorial arrangement of treatments to evaluate the interactive effects of concentration of wet corn gluten feed (WCGF) and bulk density (BD) of steam-flaked corn (SFC) on feedlot performance, carcass characteristics, and apparent total tract digestibility. Diets consisted of 0, 15, or 30% WCGF (DM basis) with a BD of SFC at 283 or 360 g/L. The additional treatment consisted of 15% WCGF, SFC at 283 g/L, and a 6% inclusion of alfalfa hay vs. 9% for all other treatments. Steers were fed once daily for an average of 163 d. During a 5-d digestion period, DMI was measured, and fecal samples were collected for measurement of nutrient digestibility using dietary acid insoluble ash as a marker. There were few WCGF × BD interactions for feedlot performance, carcass characteristics, and digestibility. Similarly, contrasts between the treatment containing 15% WCGF/360 g/L SFC and 15% WCGF/360 g/L with 6% hay yielded few differences for performance and carcass data. Final BW responded quadratically (P ≤ 0.02) to WCGF inclusion and showed increased (P ≤ 0.007) BW for greater BD. As WCGF inclusion increased, G:F and calculated NE values (P ≤ 0.03) decreased quadratically. Steers consuming 360 g/L SFC had greater (P < 0.05) G:F than those fed 283 g/L SFC. Marbling score, HCW, 12th-rib fat thickness, and calculated yield grade increased quadratically (P ≤ 0.04) with increased inclusion of WCGF. Percentage of cattle grading premium Choice or greater responded quadratically (P = 0.04) to WCGF concentration. Increasing BD increased (P ≤ 0.01) HCW, dressing percent, marbling score, and 12th-rib fat thickness and decreased calculated yield grade and percentage of cattle grading Select; however, lower BD tended (P = 0.09) to increase LM area. Intake of DM, OM, CP, and NDF and fecal output during the digestibility period increased linearly (P ≤ 0.01) with increasing WCGF, and greater BD increased (P ≤ 0.04) intake of DM, OM, starch, and CP. Starch digestibility decreased quadratically (P = 0.008) as WCGF increased; however, digestibility of CP and NDF increased (P ≤ 0.02) linearly as WCGF increased. The 283 g/L BD increased (P ≤ 0.02) starch and CP digestibility compared with 360 g/L. These data suggest that increasing WCGF in feedlot diets with a greater BD of SFC can increase performance and carcass characteristic, but it might not be ideal for starch digestibility.

Liver and pulmonary artery tissue from 5 Angus cross bred steers, 6 goats, and 6 pigs were collected at a commercial abattoir to examine the relationship of pulmonary artery copper (Cu) concentrations and genes involved in copper homeostasis. Liver and pulmonary artery samples were collected at the time of harvest and snap frozen. Liver and pulmonary artery Cu concentrations were determined via flame atomic absorption spectrophotometry and gene expression was determined via real time PCR. Liver Cu concentrations (mg Cu/kg DM±SE) were higher (p<0.01) in cows (396.4±109.1) and goats (181.4±37.0) than in pigs (19.2±3.5). All liver Cu concentrations were within normal ranges and considered adequate for each species. Liver Cu concentration was more variable in cows and goats compared to pig liver Cu concentrations. Pulmonary artery β-hydroxylproline was higher (p<0.01) in cow and pig than goat. Real Time PCR revealed that goat liver atp7a was positively correlated (r2 = 0.92; p<0.01) to liver Cu concentrations while cow and pig atp7a was not correlated to liver Cu concentration. In the pig, liver atp7a concentration was positively correlated to atp7b (r2 = 0.66; p<0.05). Pulmonary artery Cu concentration was highest in cows (14.9±4.7), intermediate in pigs (8.9±3.3), and lowest in goats (3.9±1.1). Goat pulmonary artery Cu concentration was not correlated to ctr1 concentration, however, atp7a concentration was positively correlated with ctr1 (r2 = 0.90; p<0.01). In cow pulmonary artery, loxl1 concentration was positively correlated to eln mRNA concentration (r2 = 0.91; p<0.02). Pulmonary artery CTR1 protein concentration was positively correlated to pulmonary artery Cu (r2 = 0.85; p = 0.03) concentration while negatively correlated to liver Cu (r2 = −0.79; p<0.04). Pulmonary artery Cu concentration was not correlated to concentration of Cu homeostatic genes in the pig. These data indicate that genes involved in Cu homeostasis (ctr1, atp7A, atp7B, loxl1 and eln) are differently regulated in different species.

No abstract