The effects of backgrounding system on growing and finishing performance and carcass characteristics of beef steers.

The objective of this 2-yr study was to evaluate growing and finishing performance as well as carcass characteristics of spring-born steers backgrounded on 3 different systems, using feedstuffs readily available in the Midwest: 1) grazing corn residue and being supplemented with dried distillers plus solubles at 2.68 kg DM/steer 6 d/wk (RESIDUE), 2) grazing a late summer-planted oat-brassica forage mix (CCROP), or 3) being fed a corn silage-based diet in a drylot (DRYLOT). Steers ( = 715) were stratified by BW (278 kg ± 23 in yr 1 and 291 kg ± 91 in yr 2) and assigned to treatment and replicate (4 replications per treatment per yr). Steers assigned to DRYLOT were fed a corn silage-based diet for 54 d in yr 1 and 52 d in yr 2 before being transitioned to the finishing diet. Steers assigned to RESIDUE and those assigned to CCROP grazed 65 d in yr 1 and 66 d in yr 2 and then were fed a corn silage-based diet for 21 d in yr 1 and 33 d in yr 2 before being transitioned to the finishing diet. During backgrounding, the ADG (SEM 0.022) of steers assigned to DRYLOT (1.48 kg/d) was greater ( < 0.01) than that of steers assigned to both CCROP (1.05 kg/d) and RESIDUE (0.87 kg/d) and ADG of steers assigned to CCROP was greater ( < 0.01) than that of steers assigned to RESIDUE. At the start of the finishing period, BW of steers assigned to CCROP (381 kg) was greater ( < 0.01, SEM 2.5) than that of steers assigned to DRYLOT (361 kg) and RESIDUE (366 kg). The finishing period lasted 160 d for all treatments. Both 12th-rib fat ( = 0.89) and calculated yield grade ( = 0.39) did not differ among treatments. Finishing G:F of steers assigned to DRYLOT (0.162 kg/kg) was greater ( < 0.01, SEM 0.0015) than that of steers assigned to RESIDUE (0.153 kg/kg) and CCROP (0.153 kg/kg), which did not differ ( = 0.79). In yr 1, HCW of steers assigned to CCROP (402 kg) was greater ( < 0.01, SEM 2.1) than that of steers assigned to both RESIDUE (389 kg) and DRYLOT (391 kg), which did not differ ( = 0.40). This difference in HCW is most likely a result of differences in BW at the start of the finishing phase in yr 1. However in yr 2, HCW of steers assigned to CCROP (400 kg) and RESIDUE (397 kg) did not differ ( = 0.26, SEM 2.1) but were greater ( < 0.01) than that of steers assigned to DRYLOT (367 kg), despite the fact that steers assigned to RESIDUE entered the finishing phase at a lighter BW than steers assigned to CCROP. Marbling was greater ( = 0.01, SEM 3.9) for steers assigned to DRYLOT (429) than for steers assigned to RESIDUE (414), although steers assigned to CCROP (424) were not different ( ≥ 0.10) from steers assigned to DRYLOT or RESIDUE. When cost and price scenarios from the last 5 yr were conducted, no treatment appeared to be consistently superior in terms of cost of gain or net return. Therefore, all 3 systems appear to be viable options for producers.

Effect of ferric ammonium citrate in feedlot diets with varying dried distillers' grains inclusion on ruminal hydrogen sulfide concentrations and steer growth.

Angus-cross steers ( = 128) were used to examine the effects of supplementing ferric ammonium citrate (FAC; 300 mg ferric Fe/kg DM) to diets of 20, 40, or 60% dried distillers' grains plus solubles (DDGS) on growth performance, liver mineral and ruminal hydrogen sulfide (HS) concentrations, and carcass traits of finishing steers. Steers were blocked by initial BW (436 ± 10.6 kg) into pens of 4 and randomly assigned to 1 of 6 treatments ( = 5 or 6 pens per treatment) including a 20, 40, or 60% DDGS inclusion diet with (+) or without (-) 300 mg Fe/kg DM from FAC. Liver biopsies (d -9/-10 and 96) and HS measures (d 0, 7, 14, 21, and 95) were determined from 1 steer/pen. Steers were harvested on d 102 and carcass data were collected. A treatment × month effect ( ≤ 0.006) was noted for ADG and G:F, in which the 20-FAC ADG and feed efficiency were greater ( ≤ 0.02) between d 0 to 28 but lesser ( ≤ 0.04) from d 29 to 56 than that of the 20+FAC steers. Final BW linearly decreased ( < 0.01) as DDGS inclusion increased. Final BW tended to be greater ( = 0.10) in the 60+FAC steers than in the 60-FAC steers, whereas final BW was not different ( ≥ 0.32) due to FAC supplementation in the 20 or 40% DDGS diets. A quadratic effect was noted for DMI ( = 0.02), where 60% DDGS decreased DMI. Within the 20% DDGS diet FAC+ improved DMI ( = 0.03) but had no effect within 40 or 60% DDGS inclusion. Ruminal HS concentrations were not affected ( ≥ 0.25) by FAC, but increasing DDGS linearly increased ( < 0.01) ruminal HS values. Liver Cu was decreased ( < 0.01) by FAC across all DDGS inclusions and tended to linearly decrease ( = 0.06) with increasing DDGS inclusion, whereas liver Fe, Mn, and Zn were not altered ( ≥ 0.11) by DDGS inclusion. Liver Zn concentrations tended to be ( = 0.08) or were ( = 0.03) decreased by FAC supplementation within 20 and 40% DDGS, respectively. Increasing the inclusion of DDGS linearly decreased ( = 0.04) HCW and quadratically affected marbling score where the 40% DDGS had the greatest ( = 0.02) marbling scores. Supplementation of FAC within 60% DDGS improved ( ≤ 0.03) HCW and LM area. Marbling scores were greater ( ≤ 0.04) in 20+FAC and 40+FAC compared with 20-FAC and 40-FAC, respectively. In conclusion, although ruminal HS concentrations were not affected by FAC under the conditions of this study, supplementing FAC to diets containing 60% DDGS improved HCW and LM area, suggesting that FAC may be beneficial when dietary S concentrations exceed 0.5%.

Assessment of serum 25-hydroxyvitamin D concentrations of beef cows and calves across seasons and geographical locations.

Vitamin D is critical for the growth and development of calves and positively contributes to immune function of cattle. Serum 25-hydroxyvitamin D (25(OH)D) concentrations above 20 ng/mL have traditionally been considered adequate for growth and development of cattle, but recent evidence has indicated that concentrations below 30 ng/mL are insufficient for immunity. Because little information is available regarding vitamin D status of beef cattle, the objective of this study was to evaluate vitamin D status of beef cow-calf herds on pasture as affected by season and location. Serum samples were collected from 43 cow-calf pairs plus an additional 54 calves in herds located in Florida, Idaho, and Minnesota in the spring calving season. Samples were collected again over the summer months from animals in the Florida and Minnesota herds. Effects of subcutaneous injection of vitamins A, D, and E also were investigated in a subset of calves from the Idaho herd. All cows sampled had serum 25(OH)D concentrations above 30 ng/mL at the time of calving in the spring. The average serum 25(OH)D concentrations of cows rose from near 60 ng/mL in the spring to 75 ng/mL in the summer ( < 0.001). Most calves, on the other hand, had serum 25(OH)D concentrations below 20 ng/mL. The calves in the Florida and Minnesota herds similarly rose from averages of 10 to 15 ng/mL at birth to near 50 ng/mL by the end of summer. Serum 25(OH)D of severely deficient calves increased from 3 ng/mL in nonsupplemented calves to 11 ng/mL at 48 h after birth if given a bolus supplementation of 40,000 IU of vitamin D via subcutaneous injection of a vitamin A, D, and E supplement at birth ( < 0.001). Vitamin D supplementation of cows late in pregnancy has been shown to increase serum 25(OH)D of calves; however, beef cattle generally receive very little supplemental vitamin D, as was the case for the cows studied here. The lower serum 25(OH)D of cows in spring compared with summer and the prevalence of vitamin D deficiency of calves observed here indicate that increased vitamin D supplementation of cows over the winter months or vitamin D supplementation of newborn calves would be beneficial.

Effect of protein supplementation and forage allowance on the growth and reproduction of beef heifers grazing stockpiled tall fescue.

Stockpiled tall fescue can provide adequate winter forage for beef cattle, although unsupplemented replacement heifers may display marginal performance before breeding. The objective of this study was to determine if protein supplementation and/or additional forage improves growth and reproductive performance of replacement heifers grazing stockpiled fescue. Cattle averaging 272 ± 1.59 kg were stratified by BW and then randomly assigned to 1 of 4 plots within a pasture replication. Treatment combinations were assigned in a 2 × 2 factorial arrangement and included 1) a conservative forage allocation ("normal," targeting 85% forage use) and mineral supplement (normal forage allocation with mineral supplement [FM]), 2) normal forage allocation with protein tub (FT), 3) more liberal forage allocation ("extra," targeting 70% forage use) and mineral supplement (extra forage allocation with mineral supplement [EM]), and 4) "extra forage allocation with protein tub (ET). Treatments were administered for 8 wk from early November to early January. Heifers were fed fescue hay for 1 wk before breeding in late January. Heifers were synchronized with the 7-d CO-Synch + controlled internal drug release device protocol and inseminated in late January. Heifers were checked for pregnancy by ultrasonography at 35 and 90 d after AI. Main and interaction effects between the 2 treatments were determined. Total supplement intake was greater for protein tub than mineral supplement (0.36 vs. 0.11 kg·heifer·d, respectively; < 0.0001), and the additional dietary protein in the tub groups resulted in greater serum urea N concentrations ( < 0.0001; 8.15 vs. 10.4 mg/dL for mineral and protein tub, respectively). Forage utilization efficiency was greater for normal than extra forage allocation (74.7 vs. 65.8%, respectively; < 0.0001). Main effects of both treatments on ADG were significant ( < 0.0001; 0.28, 0.43, 0.43, and 0.51 kg·heifer·d for FM, FT, EM, and ET, respectively). There was an interaction effect of the 2 treatments on change in BCS ( < 0.05; 0.12, 0.10, 0.18, and 0.31 for FM, FT, EM, and ET, respectively). Reproductive tract scores, pelvic area, and AI pregnancy rates were not different between treatments ( > 0.05). Overall, feeding a protein supplement or providing extra forage increased gain and interacted to increase BCS but did not have an effect on reproductive performance. Supplementing with protein and providing extra forage are strategies that can increase gain in heifers, which could aid heifers in reaching puberty before estrous synchronization.

High-sulfur in beef cattle diets: a review.

While many cattle feeding areas in the United States have long dealt with high sulfate water, increased feeding of ethanol coproducts such as distillers grains with solubles to beef cattle has led to a corresponding increase in dietary sulfur. As a result, sulfur metabolism in the ruminant has been the focus of many research studies over the past 10 yr, and advances in our knowledge have been made. Excessive sulfur in cattle diets may have implications on trace mineral absorption, dry matter intake, and overall cattle growth. This review will focus on what we have learned about the metabolism of sulfur in the ruminant, including ruminal sulfate reducing bacteria, the role of ruminally available sulfur, factors affecting the production of hydrogen sulfide in the rumen, and the potential mechanisms behind sulfur toxicity in cattle. Additionally, this review will discuss potential strategies to minimize risk of sulfur toxicity when cattle are fed high-sulfur diets, including dietary and management strategies. Further research related to high-sulfur diets including implications for carcass characteristics, meat quality, and animal health will also be discussed. As ethanol production processes continue to change, the nutrient profile of the resulting coproducts will as well. Often removal of one nutrient such as oil will result in the concentration of other nutrients such as sulfur. Therefore, it seems even more likely that a better understanding of sulfur metabolism in the ruminant will be important to beef cattle feeding in the future.

Feeding ferric ammonium citrate to decrease the risk of sulfur toxicity: effects on trace mineral absorption and status of beef steers.

The objective of this study was to determine the effects of adding ferric ammonium citrate (FAC; 300 mg ferric Fe/kg DM) to a 0.51% S diet on diet digestibility, mineral balance, and 56-d performance of steers fed a high concentrate diet. Angus-crossbred steers (n = 18) were randomly assigned to 1 of 3 treatments: 1) control diet (0.21% S; CON), 2) CON + sodium sulfate (0.51% S; high S [HS]), and 3) the HS diet + 300 mg of ferric Fe from FAC/kg DM (0.51% S; HS+Fe). This study included 2 phases, 1) a metabolism trial (d -1 to 20) and 2) a 56-d feedlot trial (d 22 to 79). In phase 1, 2 groups of 9 steers (370 ± 9.5 kg) were adapted to diet (10 d) and metabolism stalls (5 d), and following the adaptation period, a 5-d total collection of feces and urine was conducted. Feed offered and refused was recorded daily, and diet digestibility and retention of Cu, Fe, Mn, and Zn was determined. In phase 2, steers (384 ± 11.9 kg) were individually fed their respective diet in feedlot pens for 56 d and ADG was determined. From each steer, jugular blood and a liver biopsy were collected on d -1, 41, and 72 and d -1 and 72, respectively, for mineral content. Ruminal hydrogen sulfide concentrations (n = 18) were determined on d -1, 9, 23, 31, 41, 51, 61, and 72. In phase 1, DMI (P = 0.02), fecal output (P = 0.06), and intake of Cu, Mn, and Zn (P ≤ 0.04) were less in steers consuming the high S diets than CON, but DM and OM digestibility and urine excretion of minerals were not different (P ≥ 0.12) due to treatment. As a percent of intake, urinary excretion of Cu tended (P = 0.07) to be greater in the HS steers than the CON and HS+Fe steers, which did not differ (P = 0.74). In phase 2, BW, ADG, and G:F were not different (P ≥ 0.29) due to treatment, but DMI was lesser (P < 0.01) in the HS+Fe steers than CON and HS steers, which did not differ (P = 0.13). Ruminal hydrogen sulfide concentrations were greater (P < 0.01) in the steers fed high S diets than CON but were not different (P = 0.86) among the high S diets. Plasma Cu, Fe, and Zn concentrations were not different (P ≥ 0.27) due to treatment on all days. Final liver Cu concentrations were lesser (P < 0.01) in the steers fed high S diets compared with the CON, while liver Fe, Mn, and Zn concentrations did not differ (P ≥ 0.28) among treatments. In conclusion, adding Fe to a high S diet did not affect DM or OM digestibility or trace mineral absorption and status of steers relative to the HS diet alone.

Increasing dietary neutral detergent fiber concentration decreases ruminal hydrogen sulfide concentrations in steers fed high-sulfur diets based on ethanol coproducts.

Cattle feedlot diets commonly contain ethanol coproducts that are high in S. This dietary S is reduced in the rumen by sulfate reducing bacteria, resulting in an accumulation of hydrogen sulfide (H2S), increasing the risk for S toxicity. A negative correlation between H2S and ruminal pH has been observed previously. The objective of this study was to determine the effect of varying dietary NDF from chopped bromegrass hay (66% NDF) on performance, ruminal pH, and ruminal H2S gas concentration of steers fed a high-S finishing diet. One hundred fifty crossbred steers (359 ± 51 kg BW) were blocked by BW into pens of 5 steers and randomly assigned within block to 1 of 5 treatments (n = 6 pens per treatment) and fed for 84 d. Dietary treatments included 3.5, 5.7, 7.9, 10.1, or 11.4% roughage NDF (rNDF) from bromegrass hay and contained 0.46% dietary S from a combination of dried distillers grains with solubles and condensed corn distillers solubles. In all diets, hay was added at the expense of dry-rolled corn. Effective NDF increased linearly (P < 0.01) with increased inclusion of rNDF. Final BW was not affected by rNDF (P ≥ 0.12). The addition of roughage did not affect ADG (P ≥ 0.13) or gain efficiency (P ≥ 0.12). Dry matter intake increased linearly (P < 0.01) as rNDF concentration increased. There was a treatment × month interaction for S intake (P < 0.01), explained by steers fed 3.5 or 11.4% rNDF increasing S intake each month whereas the middle rNDF inclusions had similar S intake between months 1 and 2 and increased in month 3. Ruminal H2S concentrations and ruminal fluid pH were measured at 6 h postfeeding on d 7, 14, 21, 29, and 84. Ruminal pH increased linearly (P < 0.01; 5.48, 5.61, 5.71, 5.74, and 5.80 ± 0.041 for 3.5, 5.7, 7.9, 10.1, and 11.4% rNDF, respectively) and ruminal H2S concentrations decreased linearly (P < 0.01; 1.00, 0.86, 0.76, 0.70, and 0.62 ± 0.037 g/m(3) for 3.5, 5.7, 7.9, 10.1, and 11.4% rNDF, respectively) as rNDF inclusion increased. Using mixed model regression analysis, ruminal pH had a strong negative relationship with ruminal H2S concentrations (ß = -0.63; P < 0.01). Under conditions of this study, increasing roughage did not affect cattle gains but helped maintain greater ruminal pH and decreased H2S concentration, suggesting that this dietary strategy may lessen the risk of S toxicity in feedlot cattle.

Reduced supplementation frequency increased insulin-like growth factor 1 in beef steers fed medium quality hay and supplemented with a soybean hull and corn gluten feed blend.

Reducing supplementation frequency in calf growing programs can reduce labor and equipment operation costs. However, little is understood about the metabolic response of ruminants to large fluctuations in nutrient intake. Eighteen Angus or Angus × Simmental cross steers (287 ± 20 kg and 310 ± 3.6 d of age) were individually fed 1 of 3 dietary treatments using Calan gates. Dietary treatments consisted of ad libitum hay and no supplement (NS), ad libitum hay and 1% BW (as-fed basis) of supplement daily (DS), or ad libitum hay and 2% BW (as-fed basis) of supplement every other day (SA). The supplement was 90% DM and contained (as-fed basis) 47% corn gluten feed, 47% soybean hulls, 2% feed grade limestone, and 4% molasses. Hay intake and ADG was measured over a 52-d period. Steers were then moved to individual tie stalls. Steers were fed at 0800 h and blood samples were collected every hour from 0600 to 1400 h and at 1800, 2200, and 0200 h over a 2-d period. Gains were increased (P < 0.01) by supplementation but did not differ (P = 0.68) due to supplementation frequency. Average daily gain was 0.45, 0.90, and 0.87 kg ·hd(-1)·d(-1) (SEM ± 0.05) for steers NS, DS, and SA, respectively. Across the 2-d supplementation cycle area under the concentration time curve (AUC) for plasma glucose was increased (P < 0.01) by supplementation but did not differ (P = 0.41) due to supplementation frequency. The AUC for plasma insulin was increased by supplementation (P < 0.01) but did not differ (P = 0.67) due to supplementation frequency. Plasma IGF-1 was increased (P = 0.01) by supplementation and was greater (P = 0.04) for steers supplemented SA than DS. Gains of steers supplemented with a soybean hull and corn gluten feed blend on alternate days did not differ from those supplemented daily suggesting the steers were able to efficiently utilize large boluses of nutrients fed every other day. The effect of less frequent supplementation on IGF-1 deserves further examination as this hormone has been shown to increase protein synthesis.

High dietary sulfur decreases the retention of copper, manganese, and zinc in steers.

To examine the effects of dietary S on diet digestibility and apparent mineral absorption and retention, 16 steers [8 ruminally fistulated (368 ± 12 kg BW) and 8 unmodified (388 ± 10 kg BW)] were paired within modification status and BW, and within each of the 2 consecutive 28-d periods, 4 pairs of steers were randomly assigned to either a low-S (0.24%) or high-S (0.68%) pelleted diet. Bromegrass hay was fed at 5 or 7% of the diet, during periods 1 and 2, respectively. Sodium sulfate was used to increase the S content of the high-S diet. The low-S steers were fed the amount of feed their high-S counterpart consumed the previous day, while the high-S steers received 110% of the previous day's intake. Steers were adapted to individual metabolism stalls for 4 d (d -3 to 0 of period), acclimated to diet for 7 d (d 1 to 7 of period), and after high-S steers were consuming ad libitum intake for 7 d (d 14 of period), total urine and feces were collected for 5 d. Feed intake and orts were recorded daily. Dry matter and OM digestibility were determined. Jugular blood was collected before and after each collection period on d 14 and 20, and liver biopsies were collected on d 0 and 27. Macromineral (Ca, K, Mg, and Na) and micromineral (Cu, Mn, and Zn) concentrations were determined for pellets and hay, orts, feces, urine, and plasma and liver samples from each steer via inductively coupled plasma spectrometry. Dry matter intake, DM and OM digestibility, and urine volume were not affected (P ≥ 0.11) by dietary treatment, but fecal output was greater (P = 0.02) in the low-S steers than the high-S steers. A high-S diet decreased plasma Cu (P = 0.04) and liver Zn (P = 0.03) compared to low-S steers. No differences (P ≥ 0.20) were noted among urinary excretion of Cu, Mn, and Zn. Sodium absorption was greater (P < 0.01) and Cu, Mn, and Zn retention was lesser (P ≤ 0.01) in the high-S steers than the low-S steers. Apparent absorption of Ca, K, and Mg was not affected (P ≥ 0.18) by dietary treatment, while absorption of Cu, Mn, and Zn in the high-S treatment was lesser (P ≤ 0.06). In conclusion, consumption of a high-S diet for 28 d had limited effects on Ca, K, Mg, and Na absorption and retention, but decreased Cu, Mn, and Zn retention, which may limit growth and production of cattle consuming a high-S diet long-term.

Determining the influence of dietary roughage concentration and source on ruminal parameters related to sulfur toxicity.

Cattle feedlot diets often include ethanol coproducts that provide excess dietary sulfate, which is reduced to sulfide by ruminal bacteria and can be converted to hydrogen sulfide, which has been correlated to S toxicity. The objective of this study was to determine the impact of feeding varying concentrations of NDF from chopped cornstalks (CS) or chopped bromegrass hay (BH) on ruminal pH, ruminal H2S concentration, and DMI of steers fed a high-S finishing diet. Five ruminally fistulated steers (595 ± 87 kg BW) were used in a 6 × 6 Latin square with 14-d periods and fed diets containing 0.45% S from a mixture of dried distillers grains and condensed corn distillers solubles. The study was a 2 × 3 factorial arrangement of treatments with 2 roughage sources--CS or BH--and 3 concentrations of added roughage NDF (rNDF)--4, 7, or 10%. Steers had individual ad libitum access to feed and adapted to each diet for the first 7 d of each period. Effective NDF linearly increased (P < 0.01) as rNDF increased and did not differ between sources (P = 0.44). There was no effect of concentration or source of rNDF on DMI (P ≥ 0.69). Steer behavior was observed on d 13 of each period for 3 h postfeeding. Source of rNDF did not affect time at bunk, DMI during observation, or rate of DMI (P ≥ 0.42). Time at bunk linearly increased as rNDF increased (P = 0.01), while rate of DMI linearly decreased (P = 0.02). Area under the curve for ruminal pH of 5.4, 5.6, and 5.8, calculated using data from d 8 to 14 via an indwelling ruminal bolus, were linearly decreased (P ≤ 0.03) as rNDF increased. Manual ruminal pH taken 6 h postfeeding on d 14 of each period did not differ by source (P = 0.12) but linearly increased (P < 0.01) as rNDF increased. Ruminal H2S concentrations measured 6 h postfeeding on d 14 of each period did not differ by source (P = 0.47) but linearly decreased (P < 0.01) as rNDF increased (0.62, 0.35, 0.31 g/m(3) for 4, 7, and 10% rNDF, respectively). A segmented linear model was found to best fit the ruminal pH and H2S relationship data, suggesting that at or below a pH of 5.6 ± 0.08 with 95% confidence intervals of 5.4 and 5.8, pH is a strong predictor of H2S (P ≤ 0.05), while above this pH range H2S concentrations are not well correlated with ruminal pH (P > 0.50). In conclusion, adding at least 7% NDF from CS or BH to high-S feedlot cattle diets will increase ruminal pH and decrease H2S concentrations, thus decreasing potential for S toxicity.

Dietary sulfur concentration affects rumen hydrogen sulfide concentrations in feedlot steers during transition and finishing.

Angus steers (n = 96; 321 ± 29 kg BW) were used to determine how previous exposure to increased dietary S would affect ruminal hydrogen sulfide concentrations ([H(2)S]) in the feedlot, to investigate the effects of dietary S on ruminal [H(2)S] during transition and finishing, and to determine if dietary S affects the glutathione status of finishing cattle. Steers were strip-grazed on smooth bromegrass (Bromus inermis L.) over a 35 d period and received a dry distillers grains plus solubles (DDGS) supplement at 1% of BW (DM basis) that contained either 0.50% S (LS; n = 4 plots) or the DDGS supplement with an additional 0.30% S from sodium sulfate (0.80% S in supplement; HS; n = 4 plots). On d 36 steers were moved from the pastures to feedlot pens with one-half of the steers on each treatment in the pasture period remaining on the same treatment during the feedlot period and half being switched to the other treatment (n = 6 pens). For the first 10 d in the feedlot, steers were fed hay ad libitum and 1% BW of the DDGS supplement representing their new treatment, followed by transition to finishing diets. Dietary S of transition and finishing diets were 0.2% to 0.3% S for LS and 0.5% to 0.6% S for HS. No interaction between pasture and feedlot treatment was observed (P ≥ 0.50), so data for the feedlot period were pooled by feedlot treatment (n = 12 pens). Rumen [H(2)S] were measured on d 35 of the pasture period and on d 46 while receiving ad libitum hay and supplement at 6 h after the feeding of the supplement and after 7 d on each of the 3 transition diets (d 53, 60, and 67) and on d 93, 126, and 155 of the study after receiving the finishing diet for 26, 59, and 88 d at 6 h after feeding. Ruminal [H(2)S] did not differ between treatment while steers were fed the supplement on forage-based diets. However, ruminal [H(2)S] of HS-fed steers was greater (P < 0.05) than LS-fed steers when transition diets and the finishing diets were fed. Relative to S intake, ruminal [H(2)S] increased disproportionally after 26 d on the finishing diet. This was followed by a decrease in [H(2)S] on d 59 of finishing, although S intake was increased (P < 0.05) compared with d 26 of finishing. It appears that factors other than S intake alone contribute to ruminal [H(2)S]. The amount of glutathione in the liver of steers did not differ (P = 0.47) because of dietary S, but the concentration of oxidized glutathione increased (P = 0.03) in HS-fed compared with LS-fed steers, suggesting that the potential for oxidative stress in cattle fed high-S diets may warrant further investigation.

Mineral concentrations of plasma and liver after injection with a trace mineral complex differ among Angus and Simmental cattle.

To examine the effects of cattle breed on the clearance rate of an injectable mineral product, 10 Angus and 10 Simmental steers were blocked by breed and initial BW (332 ± 33 kg) and injected with either Multimin 90 (MM) or sterilized saline (CON) at a dose of 1 mL/45 kg BW. Multimin 90 contains 15 mg Cu/mL (as Cu disodium EDTA), 60 mg Zn/mL (as Zn disodium EDTA), 10 mg Mn/mL (as Mn disodium EDTA), and 5 mg Se/mL (as sodium selenite). Steers received a corn-silage-based diet, and inorganic sources of Cu, Zn, Mn, and Se were supplemented at NRC recommended amounts. Jugular blood was collected immediately before injection and at 8 and 10 h post-injection and on days 1, 8, and 15 post-injection. Liver biopsies were collected 3 d before injection and on days 1, 8, and 15 post-injection. Liver and plasma mineral concentration and glutathione peroxidase (GSH-Px) activity data were analyzed as repeated measures. Plasma concentrations of Zn, Mn, and Se were greater (P = 0.01) and Cu tended to be greater (P = 0.12) post-injection in MM steers compared with the CON steers. Regardless of treatment, Simmental cattle had lower plasma concentrations of Cu, Zn, and Se (P ≤ 0.05) when compared with Angus cattle. Erythrocyte GSH-Px activity was greater (P = 0.01) in MM steers compared with CON steers. Liver concentrations of Cu, Zn, and Se were greater (P = 0.05) in MM steers compared with CON steers post-injection. Liver Mn concentrations tended to be greater (P = 0.06) in MM steers compared with CON steers in the days post-injection. Interestingly, Simmental cattle exhibited greater (P = 0.01) liver Mn concentrations in the days after injection compared with Angus cattle (7.0 and 6.0 mg Mn/kg for Simmental and Angus cattle, respectively), regardless of treatment. It is unclear if this breed difference is biologically relevant; however, these data may suggest that differences in liver excretion of Mn exist between the two breeds. Overall, use of an injectable trace mineral increased liver concentrations of Cu and Se through the 15-d sampling period, suggesting that this injectable mineral is an adequate way to improve Cu and Se status of cattle through at least 15 d.

Effects of increased dietary sulfur on beef steer mineral status, performance, and meat fatty acid composition.

Ninety-six crossbred yearling steers (321 ± 29 kg BW) were used to determine the effects of feeding cattle a high S diet on pasture before receiving a high S diet in the feedlot. Steers were blocked by BW, allocated to 2.4-ha bromegrass (Bromus inermis L.) pastures (n = 4 plots per treatment), and supplemented at 1% BW with either low S dried distillers grains with solubles (DDGS; 0.34% total diet S; LS) or LS DDGS with additional S (0.47% total diet S; HS) from NaSO(4) for 36 d. On d 37, steers moved into the feedlot where one-half remained on the previous S treatment and the other half switched treatments, resulting in 4 treatments (LS-LS, LS-HS, HS-LS, HS-HS; LS: 0.2 to 0.3% total diet S, HS: 0.5 to 0.6% total diet S; n = 6 feedlot pens per treatment). During the pasture period, forage mass offered, grazing residual mass, and in vitro digestible DM of forage did not differ among treatments (P > 0.40), and ADG did not differ (LS: 1.6 kg · d(-1), HS: 1.7 kg · d(-1), P = 0.54). Plasma Mg measured on d 35 was decreased by ≈ 5% in response to increased dietary S during the pasture period (P = 0.05), though no effect on plasma Mg was observed during finishing (P > 0.15). Plasma Cu concentrations on d 155 were ≈ 15% less (P = 0.02) in HS vs. LS steers, and d 155 liver Cu concentrations were ≈ 51% less in HS vs. LS steers (P = 0.01). Increased dietary S during the feedlot period decreased ADG by ≈ 10% (P = 0.01) and tended to decrease HCW by ≈ 5% (P = 0.06) compared with LS steers. Steers receiving the HS diet had increased stearic acid (C18:0) and heptadecanoic acid (C17:0; P = 0.04 and 0.01, respectively) percentages in rib facings collected at slaughter. Exposing cattle to greater S diets (0.47% S) during a forage-based diet did not influence later performance on high S feedlot diets (0.5 to 0.6% S); however, cattle fed high dietary S on pasture had greater fat cover at slaughter (P = 0.01), suggesting S may have influenced lipid metabolism.

Effects of supplementation frequency on ruminal fermentation and digestion by steers fed medium-quality hay and supplemented with a soybean hull and corn gluten feed blend.

Reducing the frequency of supplementation to beef cattle would reduce labor and vehicle maintenance costs and could have the potential to increase profits if performance is not negatively affected. Six ruminally cannulated beef steers (362 ± 18 kg of BW) were used in a replicated 3 × 3 Latin square design to determine the effect of supplementation frequency (daily or on alternate days) on digestion and ruminal parameters when feeding medium-quality hay and supplementing with a mixture of soybean hulls and corn gluten feed. Dietary treatments consisted of ad libitum fescue hay (8.8% CP and 34.8% ADF) that was supplemented at 1% of BW daily (SD), supplemented at 2% of BW on alternate days (SA), or not supplemented (NS). The supplement (14.6% CP and 29.8% ADF) contained 47% soybean hull pellets, 47% corn gluten feed pellets, 2% feed grade limestone, and 4% molasses (as fed). Each period consisted of a 12-d adaptation phase followed by 6 d of total fecal, urine, and ort collection. All supplement offered was consumed within 2 h. Ruminal fluid was collected every 4 h for 2 d. Hay intake was reduced (P < 0.01) for SD and further reduced (P < 0.01) for SA. Hay intake was 1.54, 1.19, and 1.02% of BW (SEM ± 0.036) for NS, SD, and SA, respectively. There was a treatment (P < 0.01) × day interaction for mean ruminal pH. On the day of supplementation, ruminal pH for SA (6.13) was lower (P < 0.01) than those for both SD (6.29) and NS (6.52). However, on the day the SA treatment did not receive supplement, ruminal pH of SA (6.53) did not differ (P = 0.87) from ruminal pH of NS and was greater (P < 0.01) than that of SD. Ruminal pH of SD was lower (P < 0.01) than that of NS. Diet DM digestibility was increased (P < 0.01) by supplementation but did not differ (P = 0.58) because of frequency. Dry matter digestibility was 57.9, 64.1, and 64.6% (SEM ± 0.65) for NS, SD, and SA, respectively. The amount of N retained did not differ (P = 0.47) because of frequency (24.9 ± 5.61 and 22.0 ± 5.50 g/d for SD and SA, respectively) and was greater (P < 0.01) for the supplemented treatments than for NS (4.2 ± 3.30 g/d). When supplementing a blend of soybean hulls and corn gluten feed, producers can reduce the frequency of supplementation to every other day without reducing digestibility or N retention.

Estimation of relationships between mineral concentration and fatty acid composition of longissimus muscle and beef palatability traits.

The objective of this study was to determine the influence of beef LM nutrient components on beef palatability traits and evaluate the impact of USDA quality grade on beef palatability. Longissimus muscle samples from related Angus cattle (n = 1,737) were obtained and fabricated into steaks for trained sensory panel, Warner-Bratzler shear force (WBSF), lipid oxidation measured by thiobarbituric acid reactive substances (TBARS), fatty acid, and mineral composition analysis. Pearson phenotypic correlations were obtained by the correlation procedure of SAS. Beef palatability data were analyzed by the GLM procedure of SAS with USDA quality grade as the main effect. Specific mineral concentrations did not demonstrate strong correlations with WBSF or sensory traits (r = -0.14 to 0.16). However, minerals appeared to have a stronger relationship with flavor; all minerals evaluated except Ca and Mn were positively correlated (P < 0.05) with beef flavor. Stearic acid (C18:0), C18:2, C20:4, and PUFA were negatively correlated (P < 0.05) with all 3 panelist tenderness traits (r = -0.09 to -0.22) and were positively correlated (P < 0.05) with WBSF (r = 0.09 to 0.15). The MUFA were positively correlated (P < 0.05) with panelist tenderness ratings (r = 0.07 to 0.10) and negatively associated (P < 0.05) with WBSF (r = -0.11). The strongest correlations with juiciness were negative relationships (P < 0.05) with C18:2, C18:3, C20:4, and PUFA (r = -0.08 to -0.20). Correlations with beef flavor were weak, but the strongest was a positive relationship with MUFA (r = 0.13). Quality grade affected (P < 0.05) WBSF, TBARS, and all trained sensory panel traits, except livery/metallic flavor. As quality grade increased, steaks were more tender (P < 0.05), as evidenced by both WBSF and sensory panel tenderness ratings. Prime steaks were rated juiciest (P < 0.05) by panelists, whereas Select and Low Choice were similarly rated below Top Choice for sustained juiciness. Quality grade influenced (P < 0.05) beef flavor, but not in a linear fashion. Although there were significant correlations, these results indicate tenderness, juiciness, and flavor are not strongly influenced by individual nutrient components in beef LM. Furthermore, the positive linear relationships between USDA quality grade and beef palatability traits suggest quality grade is still one of the most valuable tools available to predict beef tenderness.

Performance of growing cattle grazing stockpiled Jesup tall fescue with varying endophyte status.

The objective of this study was to evaluate the performance of growing cattle when intensively grazing stockpiled endophyte-infected (E+), endophyte-free (E-), and nontoxic endophyte-infected (EN) tall fescue during the winter. The experiment was conducted over 5 consecutive winters. In each year, plots (1 ha each, 4 per treatment) were harvested for hay in August, fertilized in September, and forage was allowed to accumulate until grazing was initiated in early December. Each year, 48 Angus-cross tester cattle (4 per plot) were given a daily allotment of forage, under strip-grazing (frontal grazing) management, with a target residual height of 5 cm. Steers were used the first year, and heifers were used in subsequent years. The grazing periods for determination of pasture ADG were 86 d (yr 1), 70 d (yr 2), 86 d (yr 3), 72 d (yr 4), and 56 d (yr 5). Pasture ADG of cattle did not differ among treatments (P = 0.13) and were 0.51, 0.59, and 0.56 kg/d (SEM 0.03) for E+, E-, and EN, respectively. Serum prolactin concentrations of heifers grazing E+ were less (P < 0.05) than those grazing E- and EN during all years except yr 2. In yr 2, E+ and E- did not differ (P = 0.11). Serum prolactin of heifers grazing E- and EN did not differ (P > 0.20) except in yr 4. During yr 4, serum prolactin of heifers grazing E- was greater (P = 0.05) than that of heifers grazing EN. Serum urea-N concentrations (SUN) tended to differ among treatments (P = 0.10) and there was a treatment x year interaction (P = 0.05). During yr 1 through 3, SUN did not differ (P > 0.15) among treatments. However, as the stands aged, E- had a greater invasion of other plant species, which increased the CP content of the sward, thus causing heifers grazing E- during yr 5 to have greater (P < 0.01) SUN than heifers grazing E+ and EN, which did not differ (P = 0.89). Forage disappearance (DM basis) did not differ (P = 0.75) among treatments and was 4.7, 4.7, and 5.0 kg/animal daily (SEM 0.27) for E+, E-, and EN, respectively. Body weight gain per hectare was greater (P = 0.04) for E+ (257 kg) than for E- (220 kg) or EN (228 kg). In most years, animal grazing days on E+ were greater than those on E- or EN. However, in yr 5, animal grazing days did not differ (P > 0.20) among treatments. The use of stockpiled E+ as a source of low-cost winter feed is a viable option for producers, whereas grazing of EN may be more beneficial during the spring and fall, when more severe negative effects of ergot alkaloids have been observed.