Effects of calcium magnesium carbonate and roughage level on feedlot performance, ruminal metabolism, and site and extent of digestion in steers fed high-grain diets.

A feedlot growth performance experiment and 2 metabolism experiments were conducted to evaluate dietary roughage concentration and calcium magnesium carbonate in steers fed a high-grain diet. In Exp. 1, one hundred ninety-two crossbred yearling steers (320 +/- 10 kg of initial BW) were fed diets based on steam-flaked corn with 0, 0.75, or 1.5% CaMg(CO(3))(2). There were no effects (P > or = 0.13) on ADG, DMI, G:F, or total water intake due to CaMg(CO(3))(2). In Exp. 2, five ruminally and duodenally fistulated steers (263 +/- 9 kg of initial BW) were used in a 5 x 5 Latin square design, with 5 dietary treatments arranged in a 2 x 2 + 1 factorial: 1) 3.8% dietary roughage and no CaMg(CO(3))(2); 2) 7.6% dietary roughage and no CaMg(CO(3))(2); 3) 11.4% dietary roughage and no CaMg(CO(3))(2); 4) 3.8% dietary roughage and 1.5% CaMg(CO(3))(2); and 5) 7.6% dietary roughage and 1.5% CaMg(CO(3))(2). Water consumption was less (quadratic, P = 0.003) when 7.6% dietary roughage was fed compared with 3.8 or 11.4% dietary roughage. Intake of DM was not affected (P > or = 0.16) by dietary roughage or by CaMg(CO(3))(2). Poststomach and total tract starch digestion decreased (linear, P < 0.01) as dietary roughage increased. Ruminal pH tended (P = 0.08) to increase as dietary roughage increased but was not affected (P = 0.60) by CaMg(CO(3))(2). In Exp. 3, DMI and ruminal pH were continuously monitored in a 6 x 6 Latin square design using 6 ruminally and duodenally fistulated Holstein steers (229 +/- 10 kg of initial BW). A 3 x 2 factorial treatment structure was utilized, with factors consisting of dietary roughage concentration (4.5, 9.0, or 13.5%) and CaMg(CO(3))(2) inclusion (0 or 1.0%) to replace MgO and partially replace lime-stone. A dietary roughage x CaMg(CO(3))(2) interaction (P = 0.01) occurred as steers consuming 13.5% roughage, 1.0% CaMg(CO(3))(2) had greater DMI per meal than those consuming 4.5% dietary roughage, no CaMg(CO(3))(2) and 9.0% dietary roughage, 1.0% CaMg(CO(3))(2). Steers consuming 13.5% dietary roughage, 1.0% CaMg(CO(3))(2) and 9.0% dietary roughage, no CaMg(CO(3))(2) had greater meal length (min/meal; P = 0.01) than steers consuming 4.5% dietary roughage, no CaMg(CO(3))(2). Total tract OM digestibility decreased linearly (P = 0.01), and ruminal pH increased linearly (P = 0.01) with increasing dietary roughage concentration. Inclusion of CaMg(CO(3))(2) can replace limestone and MgO but did not produce ruminal pH responses similar to those observed by increasing dietary roughage in high-concentrate diets.

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.

Effects of source of supplemental zinc on performance and humoral immunity in beef heifers.

Two experiments were conducted to evaluate receiving-period performance, morbidity, and humoral immune response, as well as finishing performance and carcass characteristics of heifers fed different sources of supplemental Zn. In Exp. 1, 97 crossbred beef heifers (initial BW = 223.4 kg) were fed a 65% concentrate diet with no supplemental Zn (control) or 75 mg of supplemental Zn/kg of DM from Zn sulfate, Zn methionine, or Zn propionate. During a 35-d receiving period, heifers were monitored daily for signs of bovine respiratory disease. Serum samples were collected for Zn analysis on d 0, 14, and 28. After the receiving period, heifers were adapted to and fed a high-concentrate diet with no supplemental Zn for 42 d. Heifers were then assigned to finishing diet treatments, with the same concentrations and sources of supplemental Zn as during the receiving period and fed for an average of 168 d. Serum samples also were obtained on d 0 and 56 of the finishing period and at the end of the study. During the receiving period, control heifers had a greater (P < or = 0.05) BW and G:F on d 35 than heifers in the other treatments, but no differences were observed among treatments for morbidity or serum Zn concentrations (P > or = 0.50). For the finishing period, DMI and ADG did not differ among treatments; however, overall G:F tended (P = 0.06) to be less for control heifers than for heifers in the 3 supplemental Zn treatments. On d 56 of the finishing period, control heifers tended (P = 0.06) to have a lower serum Zn concentration than heifers in the 3 supplemental Zn treatments. In Exp. 2, 24 crossbred beef heifers (initial BW = 291.1 kg) were fed the same 4 treatments as in Exp. 1 for a 21-d period. The humoral immune response to treatments was determined by measuring specific antibody titers after s.c. injection of ovalbumin on d 0 and 14. Body weights and blood samples for serum Zn concentration and ovalbumin IgG titers were collected on d 0, 7, 14, and 21. Serum Zn concentration and specific ovalbumin IgG titers did not differ (P > 0.10) among the 4 treatments on any sampling day. Results from these 2 studies showed no major differences among the sources of supplemental Zn for receiving period morbidity, ADG, DMI, and humoral immune response of beef heifers; however, a lack of supplemental Zn during an extended finishing period tended to negatively affect G:F.

Power of test considerations for beef cattle experiments: a review.

The use of power tests in the planning and design of beef cattle experiments provides critical information on sample sizes necessary to detect treatment differences at a predetermined significance (alpha) level. Retrospective power analysis provides additional information about previous experiments that may be helpful in designing subsequent investigations. However, in retrospective power analyses, power is inversely related to observed significance level. Benefits of prospective and retrospective power analyses in beef cattle experiments are similar to those for other species; however, because of differences in the methods and conditions involved, considerations for the use of power test procedures are specific for beef cattle research. Retrospective power analyses were conducted on 78 published experiments and on two unpublished experiments. Experiments were compiled into categories that represented group (or pen) feeding, individual feeding, and metabolism studies. Estimated power in pen feeding experiments using randomized block designs (RBD, n = 30) was less than 0.80 for ADG and feed efficiency (FE), but not different from 0.80 for completely random designs (CRD, n = 4). Furthermore, estimated power was less for ADG than for FE in both design types. For individual feeding experiments using RBD (n = 4), power was not different from 0.80 for either ADG or FE; however, for CRD (n = 18), power was less than 0.80 for both ADG and FE. Power was similar for ADG and FE for both RBD and CRD in individual feeding experiments. In metabolism experiments, estimated power for nitrogen retention was less than 0.80 for Latin square designs (n = 20) but not for CRD (n = 4). Comparisons of power between experimental design types were likely influenced by the number of experiments involved. These results indicate that retrospective power in beef cattle experiments is affected by design type, and response variable measured.

Effects of copper and zinc source on performance and humoral immune response of newly received, lightweight beef heifers.

Two experiments were conducted to evaluate the effects of Cu and Zn source on performance, morbidity, and humoral immune response in lightweight, newly received beef heifers. A 2 x 2 factorial arrangement of treatments was used in both experiments, with either a sulfate or a polysaccharide mineral complex (SQM) source of both Cu and Zn as the factors. Supplemental Cu and Zn were included in the receiving diet at concentrations designed to provide 10 mg of Cu/kg and 75 mg of Zn/kg (DM basis). In Exp. 1, 219 newly received beef heifers (British x Continental, average initial BW = 208 kg) were given ad libitum access to a 65% concentrate diet for 35 d to determine treatment effects on DMI, ADG, G:F, and bovine respiratory disease (BRD) morbidity. In Exp. 2, 24 heifers (average initial BW = 272 kg) were fed a diet with no supplemental Cu or Zn for 35 d, followed by fasting-refeeding-fasting stress, after which the same treatment diets used in Exp. 1 were fed for 21 d to examine the effects on humoral immune response (plasma IgG titer determined by ELISA on d 7, 14, and 21) to an ovalbumin (OVA) vaccine given on d 0 and 14. Copper source x Zn source interactions were not detected in either experiment. In Exp. 1, neither Cu nor Zn source affected (P > 0.10) DMI, ADG, G:F, or BRD morbidity. In Exp. 2, d 14 (P = 0.02) and 21 (P = 0.06) OVA titers were greater for heifers that received SQM Zn compared with heifers receiving ZnSO4, but heifers receiving CuSO4 had greater OVA titers than did heifers on the SQM Cu treatment on d 14 (P = 0.01) and 21 (P = 0.001). In summary, neither supplemental Cu nor Zn source affected performance or morbidity of lightweight, newly received heifers; however, source of both Cu or Zn affected the humoral immune response to OVA, although source effects were not consistent for the two minerals.

Effects of roughage source and concentration on intake and performance by finishing heifers.

Three experiments were conducted to evaluate the effects of roughage source and concentration on intake and performance by finishing heifers. In Exp. 1, 12 medium-framed beef heifers (average BW = 389 kg) were used in three simultaneous 4 x 4 Latin square intake trials to evaluate the effects of dietary NDF supply from alfalfa hay, sudan hay, wheat straw, or cottonseed hulls fed in each Latin square at 5, 10, or 15% of dietary DM. Within each roughage concentration, roughage NDF accounted for the majority of variation in NEg intake/kg of BW0.75 among the roughage sources. Averaged across roughage concentrations, NEg intake/kg of BW0.75 tended to be greater (P < 0.10) when heifers were fed cottonseed hulls, sudan hay, or wheat straw than when they were fed alfalfa. In Exp. 2, six medium-framed beef heifers (average BW = 273 kg) were used in a 3 x 3 Latin square design to determine whether diets containing 10% (DM basis) alfalfa, cottonseed hulls, or sudan silage differed in eating rate. Average DM eating rates did not differ (P > 0.10) among roughage sources, which we interpreted to suggest that 90% concentrate diets containing alfalfa, cottonseed hulls, and sudan silage do not differ in the amount of chewing required during eating. In Exp. 3, 105 medium-framed beef heifers (average BW = 275 kg) were used in a 140-d finishing trial to evaluate three methods of dietary roughage exchange. Alfalfa at 12.5% of the dietary DM (ALF12.5) was used as a standard, and cottonseed hulls and sudan silage were each fed at three different levels: exchanged with ALF12.5 on an equal percentage DM basis, an equal NDF basis, or an equal NDF basis, where only NDF from particles larger than 2.36 mm (retained NDF) were considered to contribute to the NDF. No differences (P > 0.10) in ADG, DMI, gain:feed ratio, or NEg intake/kg of BW0.75 were detected between alfalfa and cottonseed hulls exchanged on an equal NDF basis. For sudan silage, exchanging with ALF12.5 on an equal retained NDF basis resulted in no differences (P > 0.10) in ADG, DMI, or NEg intake/kg of BW0.75. These data provide a preliminary indication that depending on the roughage sources evaluated, roughage NDF content and(or) roughage NDF from particles larger than 2.36 mm might provide a useful index of roughage value in high-concentrate finishing diets.

Effects of supplemental vitamin E on performance, health, and humoral immune response of beef cattle.

Three experiments were conducted to examine the effect of dietary vitamin E on receiving performance and health and on finishing performance of beef cattle. One hundred twenty beef steers (Exp. 1; initial BW = 173 kg) and 200 beef heifers (Exp. 2; initial BW = 204 kg) were assigned randomly to one of three treatment diets formulated to supply 285, 570, or 1,140 IU/animal daily of supplemental vitamin E during the receiving period. Average daily gain, gain:feed, and DMI were calculated every 14 d, with pen as the experimental unit. Morbidity and retreatment data were analyzed using a nonparametric procedure. After the receiving period, cattle were assigned to a grazing period followed by a finishing program and fed until slaughter. In Exp. 3, 17 beef steers were used to evaluate effects of the same three vitamin E levels on humoral immune response to an ovalbumin vaccine given on d 0 and 14. Jugular blood samples were collected on d 0, 7, 14, and 21. In Exp. 1, vitamin E did not affect (P > 0.10) ADG, DMI, or gain:feed for d 0 to 14, 14 to 28, or 0 to 28. No effects were noted for percentage of morbidity; however, cattle receiving 1,140 IU/d had a numerically (P = 0.15) lower incidence of retreatment. During the 91-d finishing phase, a quadratic effect (P < 0.08) was noted for DMI, ADG, backfat thickness, longissimus muscle area, and yield grade. In Exp. 2, a tendency for a linear (P = 0.10) increase in ADG was observed for the first 14 d of receiving; however, ADG decreased linearly (P = 0.06) with vitamin E concentration thereafter. For the 28-d period, ADG and DMI did not differ among treatments, but gain:feed decreased linearly (P < 0.05) for d 14 to 28 and for d 0 to 28. No effects on percentage morbidity were noted in Exp. 2, and no differences were detected for ADG, gain:feed, or DMI for the 98-d finishing period. There was a linear increase in yield grade (P < 0.05) and a linear (P < 0.08) decrease in longissimus muscle area with increasing vitamin E. Heifers receiving 570 IU of vitamin E during the receiving period tended to have a higher (P < 0.09) dressing percentage at slaughter. In Exp. 3, no significant differences were detected in serum IgG titers to ovalbumin on d 0, 7 or 14; however, on d 21, a linear increase (P = 0.07) in serum IgG titers was noted with supplemental vitamin E. Supplemental vitamin E had limited effects on performance; however, effects on humoral immune response and recovery from respiratory disease warrant further research.