95 Effects of Three Implant Programs on Growth Performance, Carcass Outcomes, and Weekly Activity Minutes of Finishing Steers Fed Different Days on Feed

This study evaluated the effects of a single slow-release implant compared to two re-implant programs administered at either 120 days on feed (DOF) or 80 days from harvest on performance, carcass characteristics, and activity of serially harvested feedlot cattle. Using a randomized complete block design, steers (n = 4,680) were randomly assigned to 72 pens and 1 of 12 treatments in a 3 × 4 factorial arrangement. Treatments were either a slow-release implant (SR), an initial slow-release implant followed by re-implant at 120 DOF (SR+RI-120), or an initial slow-release implant followed by re-implant 80 days from harvest (SR+RI-80) administered to cattle harvested at 166, 180, 194, or 208 DOF. A 3-axis accelerometer ear-tag was used in a subset (n =1,080) of animals to quantify rumination time and activity. No interactions (P ≥ 0.09) were observed for implant × DOF. Implant did not affect (P ≥ 0.25) final BW, ADG, or DMI, but re-implanted steers had a greater (P < 0.01) G:F ratio than SR. Re-implanted steers also had greater (P ≤ 0.03) HCW, dressed yield, and ribeye area, but less (P < 0.01) backfat, marbling, and empty body fat (EBF) compared to SR. Re-implanted steers had less (P < 0.01) choice and yield grade 4 and 5 carcasses than SR steers. As DOF increased, HCW, dressed yield, backfat, marbling, and EBF increased linearly (P < 0.01). The percentage of choice and yield grade 4 and 5 carcasses also increased (P < 0.01) linearly with additional DOF. An implant × day effect (P < 0.01) for weekly activity minutes suggests re-implanted steers had greater activity after re-implant administration. Re-implanting within the payout period of a slow-release implant increases feed efficiency, HCW, dressed yield, and activity minutes, but decreases carcass fatness and reduces quality grade regardless of timing of secondary implant administration.

PSIV-1 Effect of Corn Silage Inclusion Rate on Apparent Total Tract Digestibility of Dry Matter, Organic Matter, and Crude Protein in Finishing Steers

Maine-Anjou × Angus beef steers (n = 156; initial BW 366 ± 37.2 kg) were used in a finishing experiment at the Ruminant Nutrition Center in Brookings, SD. Steers were weighed on 2 consecutive days and assigned into 5 weight blocks. Treatments were arranged in a 2 × 2 factorial, 2 types of implants and 2 dietary treatments with 5 replicate pens for each simple effect. Dietary treatments consisted (DM basis) of 1) 15% (CS15) or 2) 30% corn silage (CS30). Other ingredients consisted of a 50:50 blend of DRC and HMC, liquid supplement and a dry supplement. Bunks were managed using a slick bunk approach and all diets contained (DM basis) 33 mg/kg monensin sodium. Feed collections occurred during the morning and afternoon feedings for two days prior to fecal collections. Each feed sample was composited in equal amounts to create a single sample for each pen. Two fecal collections from each steer occurred 7 hours apart on day 112 of the study. Feces from each steer were composited in equal amounts to create a pen sample. All samples were dried and ground through a 1-mm screen. Acid insoluble ash was used as an internal marker. Apparent total tract digestibility was calculated using the equation: 100-100 ˣ (feed marker/fecal marker) × (fecal variable/feed variable). No interaction between implant and diet was detected for any variables (P ≥ 0.08). One pen was removed from the statistical analysis due to all values being 3 standard deviations away from the mean. Intake did not differ between CS15 and CS30 (P = 0.41). Fecal output was increased 36.9% (P = 0.01) in CS30. Dry matter, organic matter, and crude protein digestion were decreased by feeding CS30 (11.47%, 10.83%, 16.35% respectively; P ≤ 0.03). As corn silage inclusion increases, digestibility coefficients for DM, OM, and CP are decreased.

21 Effect of Corn Silage Inclusion Rate on Live Growth Performance, Carcass Characteristics, Net Energy Utilization and Beef Production Per Hectare in Feedlot Finishing Steers

Maine-Anjou × Angus beef steers (n = 156; initial BW 366 ± 37.2 kg) were used in a finishing experiment at the Ruminant Nutrition Center in Brookings, SD. Steers were weighed on 2 consecutive days and assigned into 5 weight blocks (replicate pens). Treatments were arranged in a 2 × 2 factorial, 2 types of implants and 2 dietary treatments. Dietary treatments consisted (DM basis) of 1) 15% (CS15) or 2) 30% corn silage (CS30). Other ingredients consisted of DRC, HMC, liquid supplement and a dry supplement. The NEm, NEg and CP of CS15 was 94.8 Mcal/45.4 kg, 64.0 Mcal/45.4 kg and 12.7% and 91.2 Mcal/45.4 kg, 61.1 Mcal/45.4 kg, and 12.5% respectively (DM basis) for CS30. Bunks were managed using a slick bunk approach and all diets contained (DM basis) 33 mg/kg monensin sodium. Corn silage yield was assumed to be 45.7 Mg/ha and corn grain yield was calculated to be 10.2 Mg/ha. Beef production per hectare was calculated as (carcass adjusted final BW – initial BW)/hectare. No interaction between diet and implant (P ≥ 0.16) was detected for any variables. Final BW, ADG, and G:F were increased (P ≤ 0.02) by 2.2%, 6.5% and 7.2% respectively for CS15. Observed NE and the ratio of observed-to-expected NE for maintenance and gain was not influenced (P ≥ 0.15) by treatment. Dressing percent (64.52 vs. 63.47 ± 0.250; P = 0.01) and HCW (379 vs. 371 ± 13.1 kg; P = 0.02) were greater in CS15. Beef production per hectare was not impacted (P = 0.76) by feeding greater levels of corn silage. Feeding CS15 resulted in greater carcass-adjusted growth performance and HCW. No differences in beef produced per hectare of crop land means producers can feed greater inclusions of corn silage to finishing cattle without impacting carcass quality or beef production.

Effects of feeding two different blends of essential oils to finishing steers on growth performance, carcass characteristics, meat quality, meat composition, and shelf life

The objective was to evaluate the effects of feeding two different commercially available blends of essential oils to finishing steers to replace conventional feed additives in feedlot diets. Angus-based crossbred steers (N=43; starting BW=466±31 kg) were used in a randomized complete block design. Steers were randomly assigned to four different dietary treatments for the 100-day finishing period in which steers were fed high moisture corn/alfalfa silage/soybean meal diets. Dietary treatments included a negative control (no additives; CON), a positive control (33 mg/kg monensin and 11 mg/kg tylosin added to the diet; M/T), and two different proprietary blends of essential oils [EO-1: 1 g/steer/day Victus Liv (DSM Nutritional Products) and EO-2: 4 g/steer/day Fortissa Fit 45 (Provimi Canada ULC)]. Growth performance, carcass characteristics, meat quality, sensory attributes (excluding juiciness), most fatty acid parameters, and shelf-life (color and lipid oxidative stability) were generally unaffected by the inclusion of two different commercially available essential oil blends when compared with both a negative control (CON) and a positive control (M/T). This indicates that commercially available essential oil blends may show promise as a replacement to conventional feed additives like antibiotics without causing negative effects to meat quality, storage stability, and eating experience.

Effect of silage source, physically effective neutral detergent fiber, and undigested neutral detergent fiber concentrations on performance and carcass characteristics of finishing steers

This study was designed to evaluate the effect of silage source (barley vs. wheat silage) when harvested at two chop lengths (low vs. high physically effective NDF [peNDF]) and when barley silage was partially replaced with straw to increase the undigested neutral detergent fiber (uNDF) concentration on performance and carcass characteristics of finishing steers. Four hundred and fifty yearling commercial crossbred steers with an initial body weight (BW) of 432 ± 30.5 kg were allocated to 30 pens and fed diets containing 90% concentrate:10% forage for 123 days in a completely randomized block design with a 2×2 + 1 factorial arrangement. Treatments included: 1) barley silage (BarS) with low peNDF (LpeNDF); 2) BarS with high peNDF (HpeNDF); 3) BarS with straw to yield a diet with LpeNDF + uNDF; 4) wheat silage (WhS) LpeNDF; and 5) WhS HpeNDF. There were no silage x peNDF interactions for dry matter intake (DMI), average daily gain (ADG), or gain to feed ratio (G:F), but cattle fed WhS LpeNDF had a lower (P < 0.01) proportion of yield grade 3 and a greater proportion in yield grade 2 carcasses than cattle fed BarS LpeNDF or HpeNDF and WhS HpeNDF. Cattle fed WhS LpeNDF had greater (P = 0.02) incidence of severe liver abscesses when compared to cattle fed BarS LpeNDF or HpeNDF and WhS HpeNDF. Cattle fed BarS consumed less (P < 0.01) uNDF as a percentage of BW, had increased (P = 0.02) ADG, heavier (P = 0.02) hot carcass weight, with greater (P = 0.01) back fat thickness, and (P < 0.01) incidence of minor liver abscesses when compared to cattle fed WhS. Feeding HpeNDF did not affect DMI, ADG, or G:F, but increased (P = 0.02) marbling score, and reduced (P < 0.01) the proportion AA quality grade and increased (P < 0.01) those classified as AAA as compared to cattle fed LpeNDF. Cattle fed low uNDF had lesser (P < 0.01) uNDF intake as a percentage of BW, greater dressing percentage (P = 0.01), had a lower (P < 0.01) proportion of carcasses in yield grade 2, and a greater (P < 0.01) proportion of carcasses in yield grade 3 when compared to cattle fed high uNDF. Thus, silage source, peNDF, and uNDF content do not impact DMI or G:F when diets contain 10% forage, but BarS relative to WhS as well increasing the peNDF concentration may increase ADG, HCW, back fat thickness, dressing percentage, marbling score and carcasses classified as quality grade AAA. Future research is needed to evaluate the usefulness of peNDF and uNDF in rations for finishing cattle.

291 Influence of feeding amino acid complexes of zinc and copper on growth performance and carcass response of finishing steers fed ractopamine hydrochloride

A 42-d research study evaluated effects of feeding beef steers increasing levels of dietary Zn from Zn methionine (AAC-Zn; ZINPRO, Zinpro Corporation, Eden Prairie, MN) with or without supplemental Cu from Cu amino acid complex (AAC-Cu; Availa Cu, Zinpro Corp.) concurrently with ractopamine hydrochloride (RAC; Optaflexx, Elanco Animal Health, Greenfield, IN). One hundred-twenty steers (mean BW = 624 kg), ≤ 50 d from projected harvest were randomized to three pens (40 steers/pen) equipped with GrowSafe Systems (Calgary AB, Canada) feed bunk technology. Each pen was assigned to one of three treatment diets: 1) basal finishing diet + 30 mg Zn/kg DM from AAC-Zn (CON); 2) basal finishing diet + 90 mg Zn/kg DM from AAC-Zn (AAC-Zn90); or 3) AAC-Zn90 diet + 10 mg Cu/kg DM from AAC-Cu (AAC-Zn/Cu). Following allocation to treatments, cattle were acclimated to pen cohorts and GrowSafe feed bunks for 7 days. All steers were fed 300 mg RAC∙hd-1∙d-1 starting 35 d prior to harvest. Individual feed intake measurements began with RAC feeding and continued for 35 d until cattle were shipped for harvest. Carcass data were collected from each steer. Data were analyzed with individual animal as the experimental unit using PROC MIXED and PROC GLIMMIX procedures of SAS 9.4 (SAS Institute, Cary, NC). Numerically AAC-Zn90 fed cattle had heavier carcass weights than CON and AAC-Zn/Cu. Steers fed AAC-Zn90 had greater (P = 0.02) marbling scores compared to AAC-Zn/Cu. Steers fed AAC-Zn90 had lower backfat thickness (P = 0.02) and numerically greater marbling scores compared to CON. A biphasic program of feeding a lower level of AAC-Zn for the duration of the finishing phase followed by an increased rate of AAC-Zn during RAC feeding may optimize overall live and carcass response and improve total individual animal value.

PSXII-2 Potential interactions between prior endophyte exposure and phytogenic supplementation for finishing steers with varying chute exit velocities

All-natural phytogenic supplementation has gained momentum in the feeding industry. Because mechanisms likely differ, these supplements could add benefit when combined with antibiotics in finishing cattle diets. Our objective was to determine influence of Actifor®Energy (ActEN) when fed with monensin and tylosin on performance and carcass measurements of finishing cattle with varying chute exit velocities (EV) and differing prior endophyte exposure (E). Crossbred steers (n = 118; 345 ± 33 kg BW) were utilized in a split plot design (whole plot: prior grazing toxic [EI] or nontoxic [EN] fescue × 6g·hd-1·d-1 dietary ActEN or control). Prior EV (PEV, subplot factor) from receiving, backgrounding, and grazing periods was included as a covariate. Weights and EV were recorded on d0, d28, d56, d112, and at slaughter when cattle were shipped to a commercial abattoir, harvested, and carcass measurements recorded. Starting weights were 22 kg lower (P = 0.10) for cattle previously grazing EI and 10 kg lower (P < 0.01) per 1m·s-1 increase in PEV. Intake (%BW) was unaffected (P > 0.10) by E or ActEN. Gain:feed (E×ActEN P = 0.09) was greater for EN/ActEN compared with EI/ActEN, most influenced by the first 28d. ADG was depressed by EI and increasing PEV (E×PEV P = 0.09) with greater PEV impact for EN compared with EI. Endophyte effects on ADG were most prominent in the first 56d. ActEN tended (P = 0.12) to interact with E status for ADG where gains were numerically greater for ActEN with EN compared with EI, especially during the first 28d. Carcass measurements were largely unaffected (P > 0.10) by E or ActEN. Decreased PEV (P ≤ 0.02) was associated with heavier HCW, increased backfat, and higher YG. Prior exit velocity and grazing regimen were the primary factors influencing performance and carcass traits. Indications of smaller effects of phytogenic supplementation on top of antibiotics, especially during the first 28 d of feeding, warrant further investigation.

189 Evaluation of Hybrid Rye on Growth Performance, Carcass Traits, and Efficiency of Net Energy Utilization in Finishing Steers

Predominately Angus steers (n = 240, initial shrunk BW 404 ± 18.5 kg) were used in a 117d feedlot experiment to evaluate the effect of hybrid rye (KWS Cereals USA, LLC, Champaign, IL; Rye) as a replacement for dry-rolled corn (DRC) on growth performance, carcass traits, and comparative net energy value in diets fed to finishing steers. Rye from a single hybrid (KWS Bono) with an ergot alkaloid concentration of 392 ppb was processed with a roller mill to a processing index (PI) of 78.8 ± 2.29. Four treatments were used in a completely randomized design (n = 6 pens/treatment, 10 steers/pen) where DRC (PI = 86.9 ± 4.19) was replaced by varying proportions of Rye [DRC:Rye, DM Basis (60:0), (40:20), (20:40), and (0:60)]. Liver abscess scores and carcass characteristics were collected at the harvest facility. Carcass-adjusted performance was calculated from HCW/0.625. Performance-adjusted NE was calculated using carcass-adjusted ADG, DMI, and mean equivalent shrunk BW with the comparative NE values for Rye calculated using the replacement technique. Data were analyzed using the GLIMMIX procedure with pen as the experimental unit. Means were separated using linear and quadratic contrasts. Replacing DRC with Rye linearly decreased (P ≤ 0.01) carcass-adjusted final BW, ADG, DMI and G:F. Feeding Rye linearly decreased HCW and LM area (P ≤ 0.04). Distributions of liver scores and USDA grades for quality and yield were unaffected by treatment (P ≥ 0.09). Using observed performance from d 19 to d 117 (period when steers were on final diet), the estimated replacement NEm and NEg values for Rye were 1.93 and 1.26 Mcal/kg, respectively. Rye can be a suitable feed ingredient in finishing diets for feedlot steers with the optimal inclusion in this experiment at 20% of DM. Complete replacement of DRC with Rye depressed DMI, ADG, and G:F.