Effects of different grazing and feeding periods on performance and carcass traits of beef steers

Over three consecutive years, 180 (60/yr) fall-born steer calves were weaned in May (average initial BW = 238 kg, SD = 36.2 kg) and allocated to one of three groups: 1) calf-fed steers that entered the feedlot at weaning; 2) short yearlings that grazed irrigated pasture for another 4 mo and entered the feedlot in September; and 3) long yearlings that grazed with short yearlings during the summer, remained on annual California foothills range through the fall, winter, and spring, and entered the feedlot the following May. All steers were fed until the average group backfat (BF), determined by ultrasound, reached 11 to 12 mm. On pasture, short- and long-yearling steers gained weight in the summer; long yearlings then slightly lost weight in the fall and winter, and then gained weight again the following spring. Average days in the feedlot were 188, 158, and 94 (P < 0.10) for calves, short yearlings, and long yearlings, respectively. Feedlot DMI increased with age (and weight) at feedlot entry, with no difference among groups in gain:feed ratio. The gain of BF was nil on pasture, even when animals were gaining weight, and then increased rapidly when animals were placed on a high-energy diet. Final body weights were heaviest (P < 0.10) in long yearlings, followed by short yearlings and then calves, indicating that a prolonged growing period increases the apparent mature size of the animal. Moreover, total carcass fat contents and percentage of Choice or above were all lower (P < 0.10) in cattle that were older at feedlot entry (i.e., long yearlings) compared with the other groups. In conclusion, increasing the backgrounding period decreased time and total concentrate requirements in the feedlot of Angus-Hereford steers. Older cattle reached 10 mm of BF at heavier weights. Grazing animals gained weight without increasing BF; however, BF increased rapidly in the feedlot. Prolonged grazing may decrease quality grade, either by impairing the ability of the animal to deposit intramuscular fat or by decreasing the time during which dietary energy supply is adequate for intramuscular fat deposition to occur.     

Effect of long- or short-term feeding of alpha-tocopheryl acetate to Holstein and crossbred beef steers on performance, carcass characteristics, and beef color stability.

Three experiments were conducted to examine the effects of vitamin E supplementation on feedlot cattle. Vitamin E supplementation did not affect feedlot performance or carcass characteristics of cattle fed a high-concentrate diet (P greater than .1). The major finding was the effectiveness of vitamin E in extending the color stability of displayed beef (P less than .01). Color stability during display of longissimus lumborum steaks from cattle supplemented with 300 IU/d for 266 d, 1,140 IU/d for 67 d, or 1,200 IU/d for 38 d was extended by 2.5 to 4.8 d. Gluteus medius steaks had an extended color display life of 1.6 to 3.8 d. The accumulation of lipid oxidation products, but not aerobic microbes, associated with displayed longissimus lumborum was suppressed for muscle from vitamin E-supplemented steers. Taste panelists detected no difference among longissimus lumborum steaks from control and vitamin E-supplemented steers but found (P less than .01) steaks aged for 21 d to be more tender than steaks aged for 7 d. Supplementing cattle with vitamin E should reduce economic losses associated with discolored beef during retail display.     

Influence of steam-flaked, steamed-whole or whole shelled corn on performance and digestion in beef steers

Three trials were conducted to evaluate finishing diets containing 67% steam-flaked corn (SFC), steamed-whole corn (SWC) or whole corn (WC). In a feeding trial, steers fed SWC consumed more (P less than .05) dry matter per day (7.6 kg) than those fed WC (7.0 kg) or SFC (6.7 kg). Average daily gain was greater (P less than .05) for steers fed SFC (1.33 kg) and SWC (1.31 kg) than for those fed WC (1.25 kg), and feed efficiency was better (P less than .05) for steers fed SFC (5.06 kg dry matter/kg gain) than for those fed WC (5.62) and SWC (5.79). Carcass characteristics were not different among the three groups. In a digestion trial, method of corn processing did not affect digestibility of dry matter and crude protein. Starch digestibility was greater (P less than .05) for SFC (99.1%) than for SWC (93.8%) and WC (93.0%). There were no differences in nitrogen (N) intake or fecal N among the three diets; however, urinary N was less (P less than .05) for SWC (19 g/d) than for SFC (27 g/d) and WC (32 g/d), and N retention was higher (P less than .05) for the SWC diet. In vitro dry matter digestibility of the SFC diet was higher (P less than .05) than for WC at 4 and 8 h of incubation and higher (P less than .05) than the SWC diet at 8, 12 and 24 h of incubation. In vitro gas production after 6 h was greater (P less than .05) for SFC than for SWC grain, which was greater (P less than .05) than WC.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship between feeding behavior and performance of feedlot steers fed barley-based diets

The relationship between feeding behavior and performance of 274 feedlot cattle was evaluated using Charolais cross steers from 2 consecutive years averaging 293 ± 41 kg for yr 1 (n = 115) and 349 ± 41 for yr 2 (n = 159). Steers were blocked by BW and assigned to 3 (yr 1) or 4 (yr 2) feedlot pens equipped with a radio frequency identification system (GrowSafe Systems). Each pen contained 5 feeding stalls that allowed individual animal access to a feed tub suspended on load cells. The system recorded animal identification, duration, and frequency of feedings as well as the amount of feed consumed during each visit. Daily variation in DMI (DVI), calculated as the absolute difference in DMI from one day to the next, as well as eating rate were determined for each steer. Barley-based diets were delivered to meet steer ad libitum intake over the 213- and 181-d feeding periods for yr 1 and 2 of the study, respectively. The backgrounding periods included the first 85 and 56 d of yr 1 and 2, respectively, in which steers were fed a 14 to 30% concentrate diet, whereas the finishing periods included the last 116 and 101 d of feeding in yr 1 and 2, respectively, with the diet consisting of 77.9% concentrate. Steers were weighed individually every 14 d. To relate feeding behavior to performance, steers were grouped by ADG and G:F and categorized as high, average, or low (based on 1 SD greater than and less than the mean). In the backgrounding and finishing periods of both years of the study, steers classified as having high ADG exhibited greater (P < 0.001) DVI than steers classified as having average or low ADG. Total daily DMI was also greater (P < 0.001) for steers in the high ADG group than those in the low ADG group. Overall, those steers with the greatest G:F also tended (P = 0.15) to have greater DVI than average or low G:F steers. Compared with average or low G:F steers, DMI by high G:F steers in both years of the study was less during backgrounding, finishing, and overall (P = 0.02). Bunk visits and bunk attendance duration were less frequent and shorter (P ≤ 0.01) overall for high compared with low G:F steers. In this study, steers with more variable eating patterns exhibited greater ADG and tended to have greater G:F, a finding that is contrary to industry perception.     

Influence of thyroid status regulation and Synovex-S implants on growth performance and tissue gain in beef steers.

The separate and combined effects of Synovex-S (SYN) ear implants and thyroxine (T4)-5'-monodeiodinase inhibition (Trial 1) and T3 injection to create a mild elevation in circulating T3 concentrations (Trial 2) on BW gain and composition of gain were studied. Trial 1 used 24, 285-kg Angus steers in two experimental phases. Low-level feeding of propylthiouracil (PTU, 1.5 mg/kg BW daily) was used to achieve inhibition of T4-5'-monodeiodinase activity (TMA). Twelve steers received neither treatment (control) and 12 received SYN+PTU (hypothesized to maximize weight gain) from 0 to 56 d (phase 1) in a single factor treatment comparison. Subsequently, PTU was fed to six control steers and not fed to six of the original SYN+PTU steers from 56 to 175 d (phase 2) in a 2 x 2 arrangement of treatments. Trial 2 used 24, 302-kg Angus-Hereford steers. Treatments were without or with SYN and without or with sc injections of T3 in polyethylene glycol (2 micrograms/kg BW every 48 hr) in a 2 x 2 factorial arrangement of treatments. In both trials, all steers were individually fed a diet of a corn-based concentrate and silage mixture at an equal metabolizable energy intakes per unit of metabolic body weight (.25 Mcal/kg BW.75). Measurements of daily dry matter intakes, weekly BW, 28-d estimates of empty body components (measured by urea dilution), final TMA (trial 1) and plasma thyroid hormone concentrations were obtained. In both trials, SYN increased BW gain and protein accretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Accidental intra-auricular artery injection of ceftiofur in two beef steers.

Two beef steers accidentally injected into a branch of the auricular artery with an oil-based formulation of ceftiofur died within 5 minutes of injection. Notable pathologic findings included distention and obstruction of cerebral and cerebellar arteries by a whitish tan material and hemorrhages within meningeal spaces, the choroid plexus, cerebrum, and cerebellum. Lipid material was identified within cerebral blood vessels in frozen sections stained with oil red O. This report describes an unusual case of brain ischemia in beef cattle.     

Correlation between production performance and feeding behavior of steers on pasture during the rainy-dry transition period

The aim of this study was to evaluate the correlation between production performance and feeding behavior of steers reared on pasture during the rainy-dry transition period. Twenty-two ½ Holstein-Zebu crossbred steers at an average age of 10 months and with an average initial body weight of 234.5 ± 16.0 kg were distributed in a completely randomized design with two types of supplementation and eleven replications. Pearson’s linear correlation analysis was performed between behavioral variables and weight gain and feed conversion. Correlation coefficients were tested by the t test. The time expended feeding at the trough was positively correlated (P < 0.05) with average daily gain (ADG) and with the number of periods of permanence at the trough. Bite rate and the number of bites per day were positively correlated (P < 0.05) with ADG and negatively (P < 0.05) with feed conversion, unlike the number of bites per swallow, which was negatively correlated (P < 0.05) with ADG. There was a positive correlation (P < 0.05) between feed efficiency in dry matter and neutral detergent fiber and ADG. Feeding behavior characteristics have little association with the production performance of cattle on pasture receiving mineral or energy-protein supplementation.     

Ruminal degradation kinetics,intake, digestibility,and feeding behavior of beef steers offered annual or perennial grass-hay with or without supplementation

Effects of dried distillers grains plus solubles (DDGS) on ruminal fermentation, degradation kinetics, and feeding behavior of steers offered annual (Eragrostis tef; TEFF) or perennial (Bothriochloa bladhii; OWB) grass hay were evaluated. Ruminally cannulated Angus crossbred steers (n = 6; body weight [BW] = 304 ± 11 kg) were assigned to a 4 × 6 unbalanced Latin square design with four treatments arranged as a 2 × 2 factorial: hay type (OWB or TEFF) and DDGS supplementation (0% or 0.5% BW [dry matter {DM} basis]). Steers had ad libitum access to hay. Periods consisted of a 14-d adaptation followed by 7 d of collection. Residues from the in situ incubations (0, 3, 6, 12, 24, 36, 48, 72, and 96 h post-feeding) were fitted to a first-order kinetics model using the NLIN procedure of SAS. The DDGS decreased (P < 0.01) TEFF DM intake (DMI) by 11.3%, while not affecting DMI of OWB. The greatest DMI was observed for steers supplemented with DDGS, regardless of forage, and least in steers consuming OWB without DDGS (hay type × DDGS; P = 0.03). Non-supplemented steers spent more (P < 0.01) time eating hay. Digestibility of DM tended (P = 0.06) to increase with DDGS supplementation. A hay type × DDGS interaction was observed (P ≤ 0.05) on ruminal effective degradable fractions. The rate of degradation, soluble fraction, and the potentially degradable fraction of organic matter (OM), neutral detergent fiber, and acid detergent fiber (ADF) increased (P ≤ 0.05), while the undegradable fraction of all components decreased (P ≤ 0.01) when steers were offered TEFF compared to OWB. Ruminal DM, OM, and ADF degradation lag-time increased (P ≤ 0.02) in steers offered OWB. Ruminal degradation kinetics were not (P ≥ 0.17) independently affected by DDGS supplementation. Average ruminal pH of steers offered TEFF (P < 0.01) and those offered DDGS (P < 0.01) were lower than OWB and non-supplemented steers. Total concentration of VFA tended (P = 0.09) to increase when DDGS was provided with OWB, while decreasing when TEFF was offered. The acetate:propionate increased (P < 0.01) with DDGS supplementation due to a decrease (P = 0.03) in propionate. Ruminal NH₃-N was greater (P = 0.03) in steers offered TEFF compared to OWB, and those supplemented with DDGS (P = 0.03). An annual, in place of a conventional, perennial hay improved intake and digestion of nutrients, without affecting feeding behavior. The supplementation with DDGS appears to affect forage intake, ruminal degradation, and feeding behavior, although not independent of forage quality.     

Effect of neck injection and handler visibility on behavioral reactivity of beef steers

The use of the neck region as an injection site in cattle is becoming routine. Use of a blind may reduce aversive behavior caused by the presence of the person administering the injection. To evaluate whether cattle react to the proximity of the stockperson or to the actual injection, one hundred twenty 10-mo-old Angus steers (298 +/- 28 kg of BW; mean +/- SD) were assigned to 1 of 4 treatment groups using a partial crossover design (neck/sham injection x blind/no blind) replicated over 2 d (3 d apart). Steers were restrained for a total of 60 s in a squeeze chute, with treatment being administered 20 s after entry. Animal reactivity was rated using 2 scoring methods, including a visual and an electronic score, for three 20-s intervals (pre-treatment, treatment, and posttreatment intervals). Flight speed (m/s) was used as a measure of aversion to the treatments and was taken upon release from the chute. No interactions (P > 0.10) were observed between the blind and injection treatments for any of the measurements taken. No treatment or day effect on flight speed (2.7 vs. 2.6 m/s; P > 0.03) was observed; however, the correlation between days (r = 0.74; P < 0.001) was significant. Visual scores indicated that injected steers were more agitated during the treatment interval than were the sham injected steers (1.9 vs. 1.6, respectively; P = 0.01). However, no differences (P > 0.10) were found between injection and sham injection treatments for any of the electronic scores. Steers exposed to the blind had lower electronic reactivity scores (P < 0.05) than those not exposed to the blind, which was in contrast to the results obtained for the visual scores (P < 0.05). Discrepancies between reactivity scores may be due to the difficulty of accurately assessing minor animal responses using the visual method. The presence of a handler during an injection procedure could be a contributor to the aversion response observed in cattle undergoing routine neck injections, and use of a blind helped to reduce the reactivity of the steers.     

Effects of salinomycin on ruminal characteristics and performance of grazing beef steers

Grazing trials were conducted for 2 yr using weanling Brahman crossbred beef steers to evaluate graded levels of salinomycin (0, 50, 100 or 150 mg. head-1.d-1) for 161 d and to evaluate salinomycin in a free-choice mineral supplement (99 d). The 40 and 48 steers in trials 1 and 2 had average initial weights of 198 and 285 kg, respectively. In trial 1, steers were group-fed to consume either 0, 50, 100 or 150 mg of salinomycin.head-1.d-1 in .9 kg ground corn while grazing bermudagrass pastures. Both linear (P less than .01) and quadratic (P less than .05) effects were observed for steer performance as salinomycin level increased from 0 to 150 mg.head-1.d-1. Linear increases (P less than .01) in ruminal NH3-N (mg/100 ml) and in the molar proportion of propionate and decreases (P less than .01) in butyrate and acetate/propionate were detected. In trial 2, mineral supplements with and without salinomycin were fed free-choice to steers on bermudagrass pasture. The mean salinomycin intake of 38 mg.head-1.d-1 was lower than anticipated as a result of the instability of salinomycin in the mineral supplement and the slightly lower intake (65 g/d) than anticipated (75 g/d). Performance of steers was not influenced by salinomycin supplementation in trial 2. The ionophore salinomycin at intakes over 50 mg.head-1.d-1 appears to increase the performance of steers grazing bermudagrass pasture.     

Effects of feeding high-oil corn to beef steers on carcass characteristics and meat quality

To assess the effects of feeding high-oil corn on carcass characteristics and meat quality, 60 yearling steers were fed high concentrate diets containing either control corn (82% of diet), high-oil corn (82% of diet), or high-oil corn at a concentration that was isocaloric with the control diet (74% of diet). After being fed for 84 d, steers were slaughtered. At 72 h postmortem, carcass data were collected and rib sections from five steers grading U.S. Choice and five steers grading U.S. Select from each treatment were collected, vacuum packaged, and aged for 14 d. Three steaks (2.54 cm thick) were removed from each rib for Warner-Bratzler shear force measurement, sensory appraisal, and fatty acid composition analyses. Data were analyzed with treatment as the main effect for the carcass data and treatment, quality grade, and two-way interaction in the model for the longissimus data. The two-way interaction was nonsignificant (P > 0.05) for all variables tested. No differences were detected (P > 0.05) in carcass measurements except for marbling scores and quality grades, both of which were greater (P < 0.05) for carcasses from steers fed the high-oil corn. Overall, 78% of steers fed the high-oil corn graded U.S. Choice compared with 47% for the control and 67% for isocaloric group. Shear force and sensory properties of the longissimus were not different (P > 0.05) among treatments. Steaks from U.S. Choice carcasses rated higher (P < 0.05) for tenderness and tended to rate higher (P < 0.10) for juiciness. Feeding the isocaloric and high-oil diets increased (P < 0.05) linoleic acid, arachidonic acid, and the total PUFA content of lipid extracted from the longissimus. Saturated fatty acid percentage was lowest (P < 0.05) for high-oil corn and highest (P < 0.05) for control, with isocaloric being intermediate. Feeding high-oil corn increased (P < 0.05) pentadecyclic acid, margaric acid, and total odd-chain fatty acid content. Feeding high-oil corn in finishing beef cattle diets enhanced intramuscular lipid deposition and increased unsaturation of fatty acids of the longissimus.     

Effects of feeding level on efficiency of high- and low-residual feed intake beef steers

Comparing heat production after ad libitum (ADLIB) and restricted (RESTRICT) feeding periods may offer insight into how residual feed intake (RFI) groups change their energy requirements based on previous feeding levels. In this study, the authors sought to explain the efficiency changes of high- and low-RFI steers after feed restriction. To determine RFI classification, 56 Angus-cross steers with initial body weight (BW) of 350 ± 28.7 kg were individually housed, offered ad libitum access to a total mixed ration, and daily intakes were recorded for 56 d. RFI was defined as the residual of the regression of dry matter intake on mid-test BW^0.75 and average daily gain. High- and low-RFI groups were defined as >0.5 SD above or below the mean of zero, respectively. Fourteen steers from each high and low groups (n = 28) were selected for the subsequent 56-d RESTRICT period. During the RESTRICT period, intake was restricted to 75% of previous ad libitum intake on a BW^0.75 basis, and all other conditions remained constant. After the RESTRICT period, both RFI groups had decreased maintenance energy requirements. However, the low-RFI group decreased maintenance energy requirements by 32% on a BW^0.75 basis, more (P < 0.05) than the high-RFI group decreased maintenance requirements (18%). Thus, the low-RFI steers remained more efficient after a period of feed restriction. We conclude that feed restriction decreases maintenance energy requirement in both high- and low-RFI groups that are restricted to the same degree.     

Influence of grain source on ruminal characteristics and rate, site, and extent of digestion in beef steers.

Six cannulated Salers steers (305 +/- 17 kg initial BW) were used in a double 3 x 3 Latin square design to compare the effects of the nature of the cereal (wheat vs corn) and the corn genotype (dent vs flint) on rate, site, and extent of digestion of high-concentrate diets. The cereals were coarsely cracked, and the diets were balanced to have the same percentage of starch (47.7 +/- 2.3%) and CP (14.6 +/- .7%). Differences in ruminal starch digestion were observed between wheat- and corn-based diets (86.6 vs 47.8%; P < .001) and between corn genotypes (60.8 vs 34.8% for dent and flint corns; P < .001). For flint corn, more than half the starch was digested in the hindgut. Total tract digestion of starch was greater (P < .001) by steers fed wheat than by those fed corn and did not differ (P > .1) between the two corn genotypes. Ruminal mean pH (P < .01) was lower and total VFA concentration (P < .1) was higher for wheat- than for corn-based diets. Ruminal acetate:propionate tended to increase with the decrease in the amount of starch degraded in the rumen, but differences were not significant (P > .1). When wheat replaced corn, nonammonia, nonmicrobial N duodenal flow decreased (P < .01), and microbial duodenal flow increased (P < .05), so there were no differences in the duodenal flow of nonammonia N duodenal flow (P > .1). The lower nonammonia N duodenal flow for the dent corn- than for the flint corn-based diet (P < .05) was related to a lower passage of nonammonia, nonmicrobial N into the duodenum. Efficiency of microbial protein synthesis was inversely correlated with the amount of starch degraded in the rumen. Nature of the cereal, wheat vs corn, and genotype of the corn, dent vs flint, alter the site and extent of starch digestion.     

Effect of live weight gain of steers during winter grazing: I. Feedlot performance, carcass characteristics, and body composition of beef steers

Two experiments were conducted to examine the effect of previous BW gain during winter grazing on subsequent growth, carcass characteristics, and change in body composition during the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) supplemented with 0.91 kg/d of cottonseed meal. Winter grazing ADG (kg/d) for HGW, LGW, and NR steers were, respectively, 1.31, 0.54, 0.16 (Exp. 1) and 1.10, 0.68, 0.15 (Exp. 2). At the end of winter grazing, four steers were selected randomly from each treatment to measure initial carcass characteristics and chemical composition of carcass, offal, and empty body. All remaining steers were fed a high-concentrate diet to a common backfat end point. Six steers were selected randomly from each treatment for final chemical composition, and carcass characteristics were measured on all steers. Initial fat mass and proportion in carcass, offal, and empty body were greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both experiments. Live BW ADG and gain efficiency during the finishing phase did not differ (P = 0.24) among treatments, but DMI (% of mean BW) for NR and LGW was greater (P < 0.003) than for HGW steers. Final empty-body composition did not differ (P = 0.25) among treatments in Exp. 1. In Exp. 2, final carcass and empty-body fat proportion (g/kg) was greater (P < 0.03) for LGW and NR than for HGW steers. Accretion of carcass fat-free organic matter was greater (P < 0.004) for LGW than for HGW and NR steers in Exp. 1, but did not differ (P = 0.22) among treatments in Exp. 2. Fat accretion in carcass, offal, and empty body did not differ (P = 0.19) among treatments in Exp. 1, but was greater (P < 0.05) for LGW and NR than for HGW steers in Exp. 2. Heat production by NR steers during finishing was greater (P < 0.02) than by HGW steers in Exp. 1 and 2. Differences in ADG during winter grazing and initial body fat content did not affect rate of live BW gain or gain efficiency during finishing. Feeding steers to a common backfat thickness end point mitigated initial differences in carcass and empty-body fat content. However, maintenance energy requirements during finishing were increased for nutritionally restricted steers that were wintered on dormant native range.     

Effects of supplemental protein percentage and feeding level on intake, ruminal fermentation, and digesta passage in beef steers fed prairie hay.

Twelve ruminally cannulated steers (average initial BW 357 kg) were allotted to four treatments (three steers per treatment) in a replicated 4 x 4 Latin square design with 21-d periods (12 d for adaptation and 9 d for collection) to compare the effects of protein supplements that differed in percentage of CP and feeding level on low-quality forage utilization. Treatments were 1) control (C), ad libitum access to 5.6% CP prairie hay, 2) C +600 g of DM.steer-1.d-1 of a 43% CP supplement based on cottonseed meal (PS), 3) C + 1,200 g of DM.steer-1.d-1 of a 22% CP supplement based on corn grain and cottonseed meal (GS), and 4) C + 600 g of DM.steer-1.d-1 of a 22% CP supplement based on corn grain and cottonseed meal (LS). Ruminal total VFA concentrations were increased 8% (P less than .07) by PS vs GS 1 h after supplementation. Among supplemented steers, ruminal acetate (mol/100 mol) was decreased 1.2 mol/100 (P less than .03) by GS vs PS and LS; however, supplementation did not affect (P greater than .10) acetate proportions compared with C. Neither propionate nor butyrate was affected (P greater than .10) by supplementation, but among supplemented steers, butyrate proportions were 8% greater (P less than .03) for GS than for PS and 5% less (P less than .10) for LS than for the average of GS and PS. Ruminal pH did not differ (P greater than .10) among treatments. Ruminal ammonia concentrations were increased 1.4 to 4.8 mg/100 mL (P less than .07) by supplementation and typically were less for LS than for PS and GS at most sampling times. Prairie hay DMI (average = 16.3 g/kg BW) was not affected (P greater than .10) by supplementation. Fluid dilution rate was 8% faster (P less than .01) when steers were supplemented than when they were not fed supplement, and fluid dilution rate was increased 4% (P less than .04) by GS compared with PS. Particulate digesta passage rate was not affected (P greater than .10) by treatment, but total tract retention time was decreased (P less than .01) 10% by supplementation. Extent and rate of prairie hay NDF digestion in situ were not greatly affected by supplementation, but in situ disappearance of supplement N was 6 to 10 percentage units less (P less than .06) for GS than for PS and 2 to 6 percentage units less for LS than for the average of PS and GS supplements.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of slow-release urea on ruminal digesta characteristics and growth performance in beef steers

Two experiments were conducted to evaluate the effects of slow-release urea (SRU) versus feed-grade urea on ruminal metabolite characteristics in steers and DMI, gain, and G:F in growing beef steers. Experiment 1 used 12 ruminally cannulated steers (529 +/- 16 kg of BW) to monitor the behavior of SRU in the ruminal environment. Compared with feed-grade urea, SRU decreased ruminal ammonia concentration (P = 0.02) and tended to increase ruminal urease activity (P = 0.06) without affecting ruminal VFA molar proportions or total concentrations (P > 0.20). After 35 d of feeding, the in situ degradation rate of SRU was not different between animals fed urea or SRU (P = 0.48). Experiment 2 used 180 Angus-cross steers (330 +/- 2.3 kg) fed corn silage-based diets supplemented with urea or SRU for 56 d to evaluate the effects on feed intake, gain, and G:F. The design was a randomized complete block with a 2 x 4 + 1 factorial arrangement of treatments. Treatments included no supplemental urea (control) or urea or SRU at 0.4, 0.8, 1.2, or 1.6% of diet DM. Over the entire 56 d experiment, there were interactions of urea source x concentration for gain (P = 0.04) and G:F (P = 0.01) because SRU reduced ADG and G:F at the 0.4 and 1.6% supplementation concentrations but was equivalent to urea at the 0.8 and 1.2% supplementation concentrations; these effects were due to urea source x concentration interactions for gain (P = 0.06) and G:F (P = 0.05) during d 29 to 56 of the experiment. The SRU reduced DMI during d 29 to 56 (P = 0.01) but not during d 0 to 28, so that over the entire experiment there was no difference in DMI for urea source (P = 0.19). These collective results demonstrate that SRU releases N slowly in the rumen with no apparent adaptation within 35 d. Supplementation of SRU may limit N availability at low (0.4%) concentrations but is equivalent to urea at 0.8 and 1.2% concentrations.     

Effects of residual and reapplied biosolids on performance and mineral status of grazing beef steers

An experiment was designed to assess the mineral status of 60 Angus yearling beef steers grazing bahiagrass pastures fertilized with large amounts of biosolids from three sources: Baltimore, MD; Tampa, FL; and Largo, FL. Biosolids were classified as exceptional quality and thus had no regulatory restrictions on loading rate. They differed primarily in concentration of Mo (12 to 56 mg/kg of DM). Residual treatments (biosolids applied only the previous year) for Baltimore biosolids were applied at 22.4 and 44.8 t/ha, and Tampa biosolids were either 16.8 or 33.6 t/ ha. The reapplied treatments (applied in consecutive years) for both Baltimore and Tampa sludges were applied at 22.4, 44.8, 16.8 , and 33.6 t/ha, respectively. The two Largo biosolids treatments were either 56 or 112 t/ha and were applied only in the 2nd yr. Liver biopsies and blood samples were collected on d 1, 95, and 180. Liver and plasma were analyzed for minerals and blood was analyzed for hemoglobin, hematocrit, and superoxide dismutase of polymorphonuclear neutrophils. Experimental animals were generally adequate in macromineral status and Co, Fe, and Mn throughout the experiment. Copper deficiency was evident based on the clinical signs of hair coat discoloration, very low plasma Cu at d 95, and the continuous decline in liver Cu over 180 d. A sharp decline in plasma Cu was observed for all treatments from d 1 to 95, after which Cu concentrations rebounded to normal concentrations (> 0.65 microg/mL) by d 180. Liver Mo was well below concentrations indicating toxicity (> 5.0 mg/kg). The steep decline in liver Cu over the first 95 d reflects the dietary Cu deficiency and the possibility of high forage S (0.26 to 0.52%) interfering with Cu metabolism. Biosolids application to bahiagrass pastures was not detrimental to mineral status except for declining Cu stores; however, the controls likewise declined, but to a lesser degree.     

Effects of body weight, frame size and rate of gain on the composition of gain of beef steers

Energy concentration of gain (EG) is an inherent component in beef cattle feeding systems. The National Research Council (NRC) uses equations based on body weight, rate of gain and cattle type to predict EG and, in turn, to calculate dietary energy requirements. From EG, fat and protein deposition can be calculated directly. A dynamic computer growth model also can be used to estimate EG. In both the NRC and the computer model, EG increases from about 3 to 6 Mcal/kg as body weight increases from 200 to 500 kg if daily gain is 1 kg. Both NRC and the model predict EG of calves to be about .3 Mcal/kg greater than a previous NRC system. In contrast to the NRC, model-predicted EG of yearlings is lower at lighter and greater at heavier body weights. Rate of gain affects estimates of EG more for the dynamic model than for the NRC systems. When predicted EG was compared with observed EG for 46 pens of feedlot steers in comparative slaughter trials, NRC estimates exhibited a narrow range compared with observed values with correlation coefficients of r = .38 and r = .71 (previous NRC). Model estimates of EG were closer (r = .85). The NRC predictions of EG systematically erred with initial body composition, diet metabolizable energy and length of feeding period (P less than .01) and with initial body weight and rate of gain (P less than .05). No systematic errors in model-predicted EG were detected. Enhanced model sensitivity to compensatory growth and rate of gain should reduce both EG and body weight gain prediction errors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic and phenotypic relationships of feeding behavior and temperament with performance, feed efficiency, ultrasound, and carcass merit of beef cattle

Feeding behavior and temperament may be useful in genetic evaluations either as indicator traits for other economically relevant traits or because the behavior traits may have a direct economic value. We determined the variation in feeding behavior and temperament of beef cattle sired by Angus, Charolais, or Hybrid bulls and evaluated their associations with performance, efficiency, and carcass merit. The behavior traits were daily feeding duration, feeding head down (HD) time, feeding frequency (FF), and flight speed (FS, as a measure of temperament). A pedigree file of 813 animals forming 28 paternal half-sib families with about 20 progeny per sire was used. Performance, feeding behavior, and efficiency records were available on 464 animals of which 381 and 302 had records on carcass merit and flight speed, respectively. Large SE reflect the number of animals used. Direct heritability estimates were 0.28 +/- 0.12 for feeding duration, 0.33 +/- 0.12 for HD, 0.38 +/- 0.13 for FF, and 0.49 +/- 0.18 for FS. Feeding duration had a weak positive genetic (r(g)) correlation with HD (r(g) = 0.25 +/- 0.32) and FS (r(g) = 0.42 +/- 0.26) but a moderate negative genetic correlation with FF (r(g) = -0.40 +/- 0.30). Feeding duration had positive phenotypic (r(p)) and genetic correlations with DMI (r(p) = 0.27; r(g) = 0.56 +/- 0.20) and residual feed intake (RFI; r(p) = 0.49; r(g) = 0.57 +/- 0.28) but was unrelated phenotypically with feed conversion ratio [FCR; which is the reciprocal of the efficiency of growth (G:F)]. Feeding duration was negatively correlated with FCR (r(g) = -0.25 +/- 0.29). Feeding frequency had a moderate to high negative genetic correlation with DMI (r(g) = -0.74 +/- 0.15), FCR (r(g) = -0.52 +/- 0.21), and RFI (r(g) = -0.77 +/- 0.21). Flight speed was negatively correlated phenotypically with DMI (r(p) = -0.35) but was unrelated phenotypically with FCR or RFI. On the other hand, FS had a weak negative genetic correlation with DMI (r(g) = -0.11 +/- 0.26), a moderate genetic correlation with FCR (r(g) = 0.40 +/- 0.26), and a negative genetic correlation with RFI (r(g) = -0.59 +/- 0.45). The results indicate that behavior traits may contribute to the variation in the efficiency of growth of beef cattle, and there are potential correlated responses to selection to improve efficiency. Feeding behavior and temperament may need to be included in the definition of beef cattle breeding goals, and approaches such as the culling of unmanageable cattle and the introduction of correct handling facilities or early life provision of appropriate experiences to improve handling will be useful.     

Effects of forage and protein source on feedlot performance and carcass traits of Holstein and crossbred beef steers.

Fifty-eight Holstein and 58 crossbred beef steers were individually fed one of four isonitrogenous diets to evaluate the effects of forage source (corn silage and alfalfa haylage) and protein source (soybean meal and fish meal) on feedlot performance. Phase 1 diets (up to 354 kg of BW) were 40% forage and 60% concentrates and were fed for 70 to 136 d (depending on diet and breed group). Phase 2 diets (354 kg of BW until slaughter) were 20% forage and 80% concentrates and were fed for 127 to 150 d (depending on diet and breed group). Slaughter end points were .6 cm of 12th rib fat for Holsteins and 1.0 cm of rib fat for crossbreds using real-time ultrasonic estimates. The steers were fed for a maximum of 330 d each year. Forage source was a significant component of variation for most growth, efficiency, and carcass traits. Holstein and crossbred steers fed alfalfa haylage had significantly lower average daily gain, feed efficiency, dressing percentage, and empty body fat and required more days on feed to reach slaughter end points, but had higher total feed energy intake available for production. Steers fed corn silage diets had significantly greater energetic efficiency (P less than .05) than those fed alfalfa haylage, due to increased use of ME to produce fat in the carcass. Protein type did not influence gain, feed or energetic efficiency, energy intake, or most carcass traits. A significant protein system x forage source interaction among the four diets was detected for crossbred steers fed corn silage and fish meal, for which there was significantly greater feed conversion with lower energy intake above maintenance, possibly due to better fiber digestion and(or) amino acid flow to the lower tract. Alfalfa haylage plus soybean meal diets decreased (P less than .05) the percentage of Holsteins grading USDA Choice or higher. These results indicate that corn silage, because of greater energy concentration, was a more desirable forage in feedlot diets composed of less than or equal to 40% forage and that protein type (soybean meal and fish meal) in growing diets is not an important factor in feedlot performance or carcass traits of Holstein or crossbred steers that are fed these diets.