Grazing methods and stocking rates for direct-seeded alfalfa pastures: II. Pasture quality and diet selection

A 2-yr study was conducted to determine the effects of two grazing methods (GM) and two stocking rates (SR) on alfalfa (Medicago sativa L. var. WL225) pasture quality and diet selection by Holstein steers. Eight pasture plots (.76 ha) were seeded in 1988 and divided into two blocks of four pastures each. Pastures were managed to allow a 36-d rest period with an average grazing season of 105 d. Before steers entered the next paddock, canopy heights (CH) of alfalfa plants were determined and pasture-forage samples were collected. Forage samples were analyzed for DM, OM, CP, and in vitro OM digestibility (IVOMD). At 12-d intervals beginning with the second grazing cycle, extrusa samples were collected from steers with esophageal fistulas. Extrusa samples were frozen, freeze-dried, and analyzed for OM, CP, IVOMD, in situ ruminal DM degradation, and ruminal undegradable protein. There were no effects of GM on alfalfa CH or pasture DM, OM, CP, and IVOMD. Increasing the SR increased pasture CP content in both years and increased DM, OM, and IVOMD in the 2nd yr. There was no effect of GM or SR on the quality of forage selected by esophageally fistulated steers. Esophageally fistulated steers selected forage that had greater OM, CP, and IVOMD than the average nutrient content of the forage. Although forage quality was greater when stocking rates were increased, the quantity of forage available per animal may have limited gains.     

Cattle performance and production when grazing Bermudagrass at two forage mass levels in the southern Piedmont

Performance and production of growing cattle (Bos taurus) on Coastal Bermudagrass [Cynodon dactylon (L.) Pers.] pasture are affected by forage allowance, but possible interactions with fertilizer nutrient source (i.e., inorganic vs. organic) and time have not been well described. We evaluated the effects of 3 nutrient sources with equivalent N rates: 1) inorganic, 2) crimson clover (Trifolium incarnatum L.) cover crop plus inorganic, and 3) chicken (Gallus gallus) broiler litter, factorially arranged with 2 residual forage mass levels [grazing to maintain high (4,528 +/- 1,803 kg/ha) and low (2,538 +/- 1,264 kg/ha) forage mass], on cattle stocking density, ADG, and BW gain during 5 consecutive summer grazing seasons. Across grazing seasons, residual forage mass and nutrient source both affected response variables, but interactions between these variables were rarely significant (P < or = 0.10). Across grazing seasons and nutrient sources, increasing grazing pressure to maintain a lower forage mass reduced ADG (0.67 vs. 0.88 kg/d; P < 0.001) but increased BW gain/ha (726 vs. 578 kg/ha; P < 0.001) due to greater stocking density (8.7 vs. 5.8 steers/ha, P < 0.001; mean BW of growing Angus steers of 212 kg). Inorganic fertilization led to greater stocking density than other nutrient sources (8.2 vs. 6.8 steers/ha, P < 0.001) because of greater forage production. Stocking density to achieve the 2 targeted forage mass levels was widely different during the initial grazing seasons of the study but nearly similar at the end of 5 yr. Cattle performance tended to decline with time during each grazing season under both residual forage mass levels, perhaps as a result of declining forage quality, because performance was positively associated with grazing season precipitation under high forage mass. Steer BW gain/ha was greater (P < 0.05) with lower forage mass early in the grazing season of all years but not necessarily later in the grazing season. Steer BW gain/ha was also greater (P < 0.05) with a lower forage mass during the early years of the study but was similar during the later years of the study. Significant variations in cattle performance and production with time confirmed the short-term seasonal effects but suggested that the long-term effects may also be of importance in maintaining productivity and environmental quality of grazed pastures.     

Grazing methods and stocking rates for direct-seeded alfalfa pastures: III. Economics of alternative stocking rates for alfalfa pastures

A framework that permits estimation of economically optimal stocking rates for alternative economic parameters and alfalfa forage allowance was developed and applied to a controlled grazing experiment conducted with Holstein steers (243 kg) placed on direct-seeded alfalfa pastures in central Michigan. Responses of ADG to alternative levels of forage allowance (FA) were summarized by a quadratic function and the associated gains/hectare were calculated. The standard stocking rate (SSR; standard livestock units/ha) that maximized gain/hectare increased with FA and was greater than that which maximized ADG. Net returns to fixed resources(NRFR)/hectare were calculated for alternative SSR and economically optimal SSR were identified under various levels of herbage mass (kg/d). The SSR that maximized NRFR were between the SSR that maximized ADG and gain/hectare. Magnitude of the sale price discount for heavier calves, the slide, influenced the optimal SSR and the sensitivity of net return to SSR. The economically optimal SSR increased as the slide increased because animals stocked under higher SSR weighed less off pasture and therefore received a lower price discount.     

Effects of feeding growing cattle high-concentrate diets at a restricted intake on feedlot performance

Three trials were conducted to compare effects of restricted intake of high-concentrate diets vs ad libitum intake of corn silage diets during the growing phase on feedlot cattle performance. In Trial 1, 120 steers (initial BW, 246 kg) were fed 1) a corn silage-based diet ad libitum, 2) a high-moisture corn-corn silage-based diet with intake restricted to a level 20% less than that of the corn silage diet or 3) a high-moisture corn-based diet with intake restricted to a level 30% less than that of the corn silage diet. Steers fed the 20% restricted corn-corn silage-based diet tended (P = .07) to gain slower than those fed the corn silage or 30% restricted high-concentrate diet. Feed efficiency and diet digestibility were greatest for steers fed the 30% restricted-intake, high-concentrate diet (P less than .01). Performance of steers during the subsequent 118-d finishing period was not affected (P greater than .65) by source of energy during the growing period. In Trial 2, ADG of steers fed the 30% intake-restricted, high-concentrate diet was lower (P less than .01) than that of steers with ad libitum access to corn silage. During the 84-d growing period, steers fed supplemental blood meal had 8.3% greater gains and a 6% greater efficiency of feed use than those fed supplemental soybean meal (P less than .01). Monensin did not affect (P = .82) performance of steers fed 30% restricted-intake diets. During the 76-d finishing period, gains and feed conversion were improved (P less than .01) for steers fed the restricted-intake diet in the growing period compared with those given ad libitum access to corn silage. During the growing period in Trial 3, ADG of steers restricted-fed an all-concentrate diet were slightly greater (P less than .10) than ADG of those given ad libitum access to corn silage. Gains did not differ (P = .37) during the subsequent finishing period when steers were switched to 85 or 100% concentrate diets. We concluded that intake of all concentrate diets can be restricted to achieve gains equal to those of steers given ad libitum access to corn silage-based diets without detrimental effects on finishing performance.     

The effects of grazing, liquid supplements, and implants on feedlot performance and carcass traits of Holstein steers

In each of 2 yr, 20 Holstein steers (185+/-7 kg initial BW) were allocated to each of three treatments: pastured for 4.5 mo on grass/legume pastures and then fed 80% corn diets (DM basis) until slaughter; pastured for 4.5 mo on grass/legume pastures with ad libitum access to molasses-based protein supplements and fed 80% corn diets until slaughter; and placed in a feedlot and fed only 80% corn diets until slaughter (FEEDLOT). Half of the steers in each treatment were initially implanted with Revalor-S and not reimplanted. Supplemented steers on pasture had greater (P < 0.05) ADG than unsupplemented steers, and FEEDLOT steers gained faster and were fatter (P < 0.05) after 4.5 mo. Implanted steers had greater (P < 0.05) ADG with no significant treatment x implant status effect. Supplement intake was variable and related to ambient temperature. During the feedlot phase, steers previously on pasture had greater DMI and ADG (P < 0.05) but were not more efficient than FEEDLOT steers. Percentage of USDA Choice carcasses, fat thickness, dressing percentage, yield grade, and final weight were greater (P < 0.05) for FEEDLOT steers than for steers on other treatments. Implanting increased ADG of all steers but did not affect carcass traits, carcass composition, or feedlot performance during the finishing phase. Holstein steers consuming supplemented and unsupplemented pasture before slaughter will be leaner, have lower carcass weights, and have generally lower quality grades than those fed exclusively in a feedlot when slaughtered at similar ages.     

Effects of establishment method and fall stocking rate of wheat pasture on forage mass, forage chemical composition, and performance of growing steers

Stocking rate is a fundamental variable for managing pastures, and there is a distinct relationship between stocking rate and animal performance for each forage type. This research was conducted to determine the effects of fall stocking rate (SR) and method of establishment of wheat pasture planted into dedicated crop fields on animal performance during the fall and subsequent spring. There was a factorial arrangement of tillage methods used in the establishment of wheat pasture and fall stocking rates. Tillage treatments included 1) CT, seed sown into a prepared seedbed, 2) RT, a single pass with a light disk followed by broadcasting of seed, or 3) NT, direct seeding into the undisturbed stubble of the grazed-out wheat pasture from the previous year. The fixed SR during the fall were 1.9, 2.5, and 3.7 growing beef steers (Bos taurus L.)/ha. In the spring all pastures were grazed at the same fixed SR by steers for graze out. Data were analyzed using the mixed procedure of SAS as a randomized complete block design with field as the experimental unit and year as the block. Forage mass, forage nutritive composition, and animal performance during the fall or spring were not affected (P ≥ 0.14) by tillage method. During the fall grazing season, with increasing SR there were linear (P < 0.01) decreases in BW of steers upon removal from pasture, BW gain per steer, and ADG, whereas grazing-day per hectare and BW gain per hectare increased linearly (P < 0.01) with increasing SR. The carryover effects of fall SR into the spring grazing season decreased (P< 0.01) grazing-day per hectare and tended (P ≤ 0.09) to produce quadratic changes in BW upon removal from pasture and BW gain per hectare. Across the fall and spring grazing seasons, grazing-day per hectare increased linearly (P < 0.01) with greater SR, and BW gain per hectare increased quadratically (P = 0.02) with increased fall SR. A tillage treatment by fall SR interaction (P = 0.10) indicates that although there was no difference (P ≥ 0.12) due to tillage treatment in BW gain per hectare at 1.9 or 2.5 SR, NT fields produced (P ≤ 0.04) more BW gain per hectare than CT or RT at the 3.7 SR. Although increasing SR of growing steers leads to reduced animal performance in the fall and reduced carrying capacity in the spring, NT appears to be capable of withstanding greater fall SR with less impact on total production per hectare than CT or RT.     

Effects of grazing residues or feeding corn from a corn rootworm-protected hybrid (MON 863) compared with reference hybrids on animal performance and carcass characteristics

One grazing and two feeding experiments were conducted to compare the feeding value of corn residue or corn grain from a genetically enhanced corn hybrid (corn rootworm-protected; event MON 863) with nontransgenic, commercially available, reference hybrids. In Exp. 1, two 13.7-ha fields, containing corn residues from either a genetically enhanced corn root-worm-protected hybrid (MON 863), or a near-isogenic, nontransgenic control hybrid (CON) were divided into four equal-sized paddocks. Sixty-four steer calves (262 +/- 15 kg) were stratified by BW and assigned randomly to paddock to achieve a stocking rate of 0.43 ha/steer for 60 d, with eight steers per paddock and 32 steers per hybrid. A protein supplement was fed at 0.45 kg/steer daily (DM basis) to ensure protein intake did not limit performance. Steer ADG did not differ (P = 0.30) between steers grazing the MON 863 (0.39 kg/d) and CON (0.34 kg/d) corn residues for 60 d. The four treatments for the feeding experiments (Exp. 2 and 3) included two separate reference hybrids, the near-isogenic control hybrid (CON), and the genetically enhanced hybrid (MON 863) resulting in two preplanned comparisons of CON vs. MON 863, and MON 863 vs. the average of the reference hybrids (REF). In Exp. 2, 200 crossbred yearling steers (365 +/- 19 kg) were fed in 20 pens, with five pens per corn hybrid. In Exp. 3, 196 crossbred yearling steers (457 +/- 33 kg) were fed in 28 pens, with seven pens per corn hybrid. In Exp. 2, DMI and G:F did not differ (P > 0.10) between MON 863 and CON; however, steers fed MON 863 had a greater (P = 0.04) ADG than steers fed CON. Gain efficiency was greater (P = 0.05) for MON 863 cattle than for REF cattle in Exp. 2, but other performance measurements (DMI and ADG) did not differ (P > 0.10) between MON 863 and REF. No differences (P > 0.10) were observed for performance (DMI, ADG, and G:F) between MON 863 and CON or MON 863 and REF in Exp. 3. In terms of carcass characteristics, no differences (P > 0.10) were observed between MON 863 and CON, as well as MON 863 and REF, for marbling score, LM area, or 12th rib fat thickness in both Exp. 2 and 3. Overall, performance was not negatively affected in the corn residue grazing or feedlot experiments, suggesting the corn rootworm-protected hybrid (event MON 863) is similar to conventional, nontransgenic corn grain and residues when utilized by beef cattle.     

Interrelationships between veld condition,herbage mass,stocking rate and animal performance in the Tall Grassland of Natal

Grazing trials were established at three sites in the Tall Grassveld of Natal. The objectives were to determine (a) patterns in herbage mass in relation to veld condition, stocking rate and commencement of spring grazing, and (b) animal performance in relation to herbage availability and stocking rate for the period November 1986 to September 1987. Rainfall exceeded the mean annual rainfall and, for moderate condition veld in particular, was very favourably distributed. Distinct patterns in herbage availability were seen during the season. A multiple linear regression model was developed for determining peak herbage mass (HM) in April from veld condition (VCI), stocking rate (SR) and time that grazing commenced in spring (T) (r=0,71; P<0,01). HM was positively related to VCI and delayed T and negatively related to SR. Seasonal growth phases in cattle were similar for different sites despite their spatial separation and differences in veld condition. It was essentially only the magnitude of mass loss or gain that varied. No linear relationships existed between SR and average daily gain (ADG). A multiple linear regression model was developed for determining ADG from SR, HM and the initial mass of the animals (IM) (r=0,93; P<0,01). ADG was positively related to IM and negatively related to SR and HM.     

Performance of Steers Supplemented with Zinc During Grazing and Receiving at the Feedlot

A study was conducted to compare the effects of three supplemental zinc sources on beef steers grazing winter annual pasture and during receiving in a feedlot. In southern Arkansas, 84 steers were weighed (BW = 216 ± 1.5 kg), bled via jugular puncture, and randomly assigned to 12 bermudagrass pastures (0.81 ha each) that had been overseeded with wheat, rye, and annual ryegrass (7 steers per pasture; 116 d of grazing) on January 15; the steers were allowed to graze until May 11. Steers were fed 0.45 kg daily of corn-based supplement containing 103 mg zinc from ZnSO₄, zinc amino acid complex (ZnAA), or zinc polysaccharide (ZnPOL) during the entire grazing period. On May 12, steers were shipped to a research feedlot (14 h; 1,016 km; 6.9% BW shrink) in northeast New Mexico. In the feedlot, the same groups of steers were fed a receiving diet (steam-flaked milo) that contained the same zinc sources as fed during the grazing period. Dietary concentrate was increased from 75 to 85% of dietary DM weekly. Data were analyzed as a completely random design; least squares means were separated using contrast. Steer BW on d 28 and 84 of the grazing period were greater (P<0.05) for cattle fed ZnAA and ZnPOL than for steers fed ZnSO₄; however, ADG over the 116 d of grazing and ending BW did not differ (P>0.28) among zinc sources. In the feedlot, steer BW, ADG, and feed efficiency did not differ (P>0.05) among zinc sources. Serum zinc concentrations did not differ (P>0.05) among zinc sources at any point in time. We conclude that early in the grazing period, ZnAA and ZnPOL improved steer BW compared with ZnSO₄; however, no differences were noted among zinc sources later in the grazing period or during receiving in the feedlot.     

Stocking Rate Effects on Steer Performance for Two Methods of Alleviating Fescue Toxicosis

Generally, grazing endophyte-infested tall fescue (Festuca arundinace Schreb.) in the late spring and summer is not recommended because of the effects of fescue toxicosis on cattle weight gains, which can be extreme. For steers conditioned to graze tall fescue in the early spring, stocking rate (3, 4, 5, and 6 steers/ha) effects were evaluated for two methods designed to avoid poor cattle performance during the late spring and summer (compensation period). The evaluation was conducted in 1997 and 1998. During the compensation phase, one replicate of each stocking rate was randomly assigned to 1-ha pastures of eastern gamagrass (Tripsacum dactyloides L.), and the other replicate of each stocking rate remained on tall fescue; the steers were fed a 1:1 mixture of broiler litter and corn at 2.27 kg as fed/steer per d. Average daily gain for steers fed eastern gamagrass during the compensation phase declined linearly (P<0.05) as stocking rate increased, but ADG for steers fed tall fescue plus the broiler litter-corn mixture tended to increase (P<0.10) as stocking rate increased. As a result, ADG and live weight gain (kilograms per hectare) with heavier stocking rates were higher for steers fed tall fescue plus the broiler litter-corn mixture, whereas the responses at a lighter stocking rate were higher for steers fed eastern gamagrass. At the conclusion of the compensation phase in 1998, steers fed tall fescue plus the broiler litter-corn mixture had lower (P<0.05) serum prolactin levels, and a higher (P<0.05) proportion of steers fed tall fescue had rough hair coats compared with those fed eastern gamagrass. Results of this study show that, for steers grazing tall fescue pastures, either eastern gamagrass or supplementation with a broiler litter-corn mixture can provide acceptable performance, but responses are affected by grazing pressure. Symptoms of fescue toxicosis can still occur, however.     

Season-Long vs Intensive-Early Stocking with Growing Cattle Grazing Bermudagrass Pasture

Our objective was to compare the performance of weaned steer calves managed with intensive-early stocking (IES; 12.4 steers per ha for 70 d) or season-long stocking (SLS; 6.2 steers per ha for 140 d) with and without supplementation (2 x 2 factorial). Beginning on May 15, 90 steers (BW = 217 ± 0.8 kg) were randomly assigned to one of 12 common bermudagrass (Cynodon dactylon [L.] Pers.) pastures (0.81 ha each) fertilized with 168 kg of nitrogen/ ha. One of the following four treatments was randomly applied to three pastures: i) SLS plus no supplement, ii) SLS plus 0.45 kg/steer of ground corn daily, iii) IES plus no supplement, and iv) IES plus 0.45 kg/steer of ground corn daily. Steers on IES were lighter (P=0.01) than SLS steers on d 70. By d 140, SLS steers supplemented with corn were 33 kg heavier (P=0.02) than nonsupplemented steers. When using SLS, corn increased the BW gain 0.5 kg/kg of corn fed; however, when IES was used, there was no benefit from corn supplementation. Total BW gain/ha did not differ (P>0.17) among treatments, but SLS with corn supplementation could have the potential to produce more BW gain/ ha compared to the other treatments. Grazing systems did not affect feedlot ADG (P>0.53), but IES (175 d on feed) steers did have a higher (P<0.01) feedlot total BW gain than the SLS steers (154 d on feed). Using IES positively affected (P<0.08) dressing percentage and longissimus area compared to SLS; however, these differences in carcass characteristics were probably the result of the longer feeding period.     

Use of dried distillers grains throughout a beef production system: effects on stocker and finishing performance, carcass characteristics, and fatty acid composition of beef

A 2-yr study was conducted using a 3 × 2 factorial arrangement of treatments to evaluate the effects of feeding dried distillers grains throughout a beef production system on performance, carcass characteristics, and fatty acid profile of beef. Factors were wheat pasture supplement [no supplement (CON), dry-rolled corn (DRC), and dried distillers grains (DDG)] fed at 0.5% BW daily and finishing diet [steam-flaked corn based diet containing 0 (SFC) or 35% (35DDG) DDG]. Each year, 60 preconditioned Hereford steers (initial BW = 198 kg ± 3) grazed winter wheat pasture with or without supplement. Body weight gain was 8% greater for steers consuming DDG supplement compared with CON and DRC steers (P < 0.01). After the grazing period, pastures within supplement treatment were randomly assigned to SFC or 35DDG. There was no supplement by finishing diet interaction for any performance or carcass variable of interest (P ≥ 0.41). Previous supplementation on winter wheat affected BW at feedlot entry and adjusted G:F (P ≤ 0.05) but had no effect on finishing ADG or carcass traits (P ≥ 0.12). On a carcass-adjusted basis, steers consuming 35DDG had reduced final BW, ADG, G:F, and total BW gain throughout the system (P ≤ 0.04) compared with SFC. Additionally, steers consuming 35DDG had reduced HCW, dressing percent, and fat thickness (P ≤ 0.03) compared with SFC. There was a supplement by finishing diet interaction (P = 0.02) for 18:0, in which cattle supplemented with DRC and fed the SFC finishing diet had the lowest concentration of 18:0 but DRC supplemented steers fed the 35DDG diet had the greatest concentration. The interaction was not significant (P ≥ 0.18) for other fatty acids. Main effects of supplement and finishing diet affected (P ≤ 0.05) several other fatty acids of interest, particularly 18:2, which is associated with reduced flavor-stability of beef. The use of DDG as a supplement to wheat pasture resulted in greater ADG during wheat grazing and heavier BW at feedlot entry, but final BW was not different from CON or DRC groups. Feeding DDG at 35% DM in steam-flaked corn-based finishing diets reduced ADG, G:F, and HCW, and affected the fatty acid composition of beef.     

Effect of supplements on growth and forage intake by stocker steers grazing wheat pasture

This experiment was conducted with stocker steers to determine the effects of supplementary fiber and grain on ruminal acid concentrations and OM intake following abrupt dietary change to lush, primary-growth wheat (Triticum aestivum) pasture and to measure the effects of those supplements on weight gain at different levels of herbage mass (HM). Each of four irrigated wheat pastures (2.4, 3.6, 4.9, and 6.1 ha) was stocked with nine Angus crossbred steers (mean = 189 kg). In each pasture, three steers were individually fed a daily supplement of 11.3 g of cottonseed hulls (CSH)/kg BW(.75), three steers were fed a supplement mixture of 11.3 g CSH/kg BW(.75) and 8.5 g corn grain/kg BW(.75), and three steers remained as controls. Body weight and HM changes were measured at 28-d intervals throughout the experiment. Ruminal samples for VFA determination were collected twice during the 1st wk on pasture. Organic matter intake calculations were based on fecal output and OM digestibility estimates made during the 2nd wk on pasture. Fecal outputs were estimated from nonlinear least squares analyses using a two-compartment rumen model of excretion patterns of Yb following a single oral dose. Digestibility of OM was estimated using indigestible NDF in feed and feces as an internal marker. Dietary supplements had no detectable effect on ruminal VFA characteristics. The magnitude of changes in ruminal acetate:propionate ratios between d 3 and 7 on pasture was significantly and negatively related to ADG during the first 28-d growth measurement period. Body condition scores taken on d 0 also had a significant, negative relationship to ADG. Average fecal output was greater for steers fed supplements (36 g/kg BW(.75)) than for control steers (30 g/kg BW(.75)) (P < .03). The supplements also significantly reduced estimates of total diet OM digestibility. However, supplements had no measurable effect on BW changes. Herbage mass up to 1,000 kg/ha had a significant and positive effect on ADG, which was 1.44 kg during Period 1, when HM was apparently not limiting in any pasture. The deduced threshold level of the influence of HM on ADG was 850 kg/ha. Under the conditions of this experiment, the effects of supplemental fiber and(or) grain on fecal output and OM digestibility were detected. However, in the amounts fed, these supplements had no detectable effect on ADG at any level of HM.     

Growth Performance by Stocker Steers Fed Magnesium-Mica During a Grazing and Feedlot Period

Two experiments were conducted to determine the effects of Mg-mica supplementation on grazing and feedlot performance of stocker steers. In Exp. 1, eight groups of six steers were fed a basal diet of 80% ground grain sorghum, 15% corn silage, and 5% control protein supplement (DM basis) or a supplement containing Mg-mica (9% of supplement; 4.5 mg/kg diet DM) for 141 d. Marbling scores tended (P<0.10) to be greater, and the percentage of carcasses grading USDA Choice or higher was greater (P<0.05), from steers fed Mg-mica than from those fed the control supplement. In Exp. 2, eight groups of nine head each were offered either a control grain sorghum-based supplement or one containing 34 g/d of Mg-mica (2.7 g Mg) while grazing smooth bromegrass pastures for 112 d. Pasture groups were then placed in feedlot pens for 120 d and fed a basal diet similar to that described above. Two groups fed each pasture supplement received a control supplement, and two received a supplement containing Mg-mica (10% of supplement; 5 mg/kg diet DM). Steers fed Mg-mica during the pasture phase tended to have heavier (P=0.11) hot carcass weights, higher (P<0.05) dressing percentages, numerically (P>0.10) higher marbling scores, and a higher percentage of carcasses grading USDA Choice than steers fed the control supplement during the pasture phase. Therefore, adding Mg-mica to pasture supplements or feedlot diets appears to have no impact on grazing or feedlot performance, but may improve carcass quality.     

Season-Long vs Intensive-Early Stocking with Growing Cattle Grazing Bermudagrass Pasture

Our objective was to compare the performance of weaned steer calves managed with intensive-early stocking (IES; 12.4 steers per ha for 70 d) or season-long stocking (SLS; 6.2 steers per ha for 140 d) with and without supplementation (2 × 2 factorial). Beginning on May 15, 90 steers (BW = 217 ± 0.8 kg) were randomly assigned to one of 12 common bermudagrass (Cynodon dactylon [L.] Pers.) pastures (0.81 ha each) fertilized with 168 kg of nitrogen/ha. One of the following four treatments was randomly applied to three pastures: i) SLS plus no supplement, ii) SLS plus 0.45 kg/steer of ground corn daily, iii) IES plus no supplement, and iv) IES plus 0.45 kg/steer of ground corn daily. Steers on IES were lighter (P=0.01) than SLS steers on d 70. By d 140, SLS steers supplemented with corn were 33 kg heavier (P=0.02) than nonsupplemented steers. When using SLS, corn increased the BW gain 0.5 kg/kg of corn fed; however, when IES was used, there was no benefit from corn supplementation. Total BW gain/ha did not differ (P>0.17) among treatments, but SLS with corn supplementation could have the potential to produce more BW gain/ha compared to the other treatments. Grazing systems did not affect feedlot ADG (P>0.53), but IES (175 d on feed) steers did have a higher (P<0.01) feedlot total BW gain than the SLS steers (154 d on feed). Using IES positively affected (P<0.08) dressing percentage and longissimus area compared to SLS; however, these differences in carcass characteristics were probably the result of the longer feeding period.     

Effect of the gain rate during growing phase on the performance and characteristics of carcass and meat of super precocious steers

The aim was to evaluate the effect of different rates of weight gain during the backgrounding on animal performance and carcass and meat characteristics of steers finished in feedlots. Thirty-six Angus steers, 12 ± 2 months of age, were backgrounded during 91 days on Aruana grass pasture (Panicum maximum cv. Aruana) managed under different stocking rates to achieve three different weight gains: HIGH ADG (average daily gain)—no feed restriction (ADG = 0.846 kg); MEDIUM ADG—moderate feed restriction (ADG = 0.456 kg); and LOW ADG—high feed restriction (ADG = 0.154 kg). To ensure the difference in ADG, we offered 0.7% live weight of concentrate feed in the HIGH treatment and a better forage supply in the MEDIUM treatment. After the backgrounding, the animals were finished in feedlot. There was no effect of the previous performance on the animals' performance in the feedlot. The LOW presented higher weight (218.9 vs. 207.9 kg) and hot (54.0% vs. 51.3%) and cold (53.5% vs. 50.5%) carcass yield than the MEDIUM, besides presenting meat with less cooking losses (15.0% vs. 18.2%), marbling (7 vs. 4.0 points), palatability (7.1 vs. 6.3 points), juiciness (7.2 vs. 6.4 points), tenderness (7.1 vs. 6.3 points), and lower shear force (5.78 vs. 8.75 kg) than HIGH. LOW ADG steers stay longer in the finishing phase but presented in general better quality carcass and meat than those with MEDIUM or HIGH during the backgrounding.     

Technical note: stocking equivalents and stocking rate-gain relationships for steers and cow-calf pairs grazing oversown bermuda grass.

Grazing experiments may use steers or cow-calf pairs for measuring animal performance on pasture treatments, but the validity of extrapolation between these classes of cattle has not been verified. A grazing study was conducted in the spring and summer of both 1988 and 1989 to determine stocking equivalents and stocking rate-weight gain relationships for steers and cow-calf pairs grazing Coastal bermuda grass (Cynodon dactylon [L.] pers.) oversown with rye (Secale cereale L.) and ryegrass (Lolium multiflorum Lam.). Average daily gain and stocking rate (SR; 3.2, 4.2, 6.2, and 7.4 animals per hectare for steers and 1.7, 2.5, 3.7, and 4.9 pairs per hectare for cow-calf pairs) were both adjusted so that comparisons could be made on an equal BW basis. Disk meter height readings were used as measurements of forage accessibility. Disk meter height responses to SR did not differ (P greater than .10) between steer and cow-calf paddocks. There was a linear (P less than .001) decrease in ADG as SR increased, but this decline was steeper (P less than .001) for steers than for cows or suckling calves. Steers tended to be more productive than calves at low SR but less productive at high SR. Disk meter heights for the range of SR used in the study did not differ (P greater than .10) for steers and cow-calf pairs at equivalent BW per hectare. Our study suggests that live BW is a reasonable basis for determining forage requirements of steers and cow-calf pairs under grazing conditions, but extrapolation of production between classes of livestock will not be reliable.     

Responses of yearling steers to different stocking rates on a subtropical grass-legume pasture

Despite potential benefits, limitations of individual tropical legumes have restricted development of sustainable grass-legume pastures in tropical and subtropical regions. Sowing mixtures of complementary legumes may overcome limitations of individual species. Responses of yearling steers grazing a mixture of three tropical legumes with bahiagrass (Paspalum notatum Flugge) were evaluated at three stocking rates under continuous grazing. Carpon desmodium (Desmodium heterocarpon [L.] DC.), which is persistent under grazing but often difficult to establish, was combined with the short-lived legumes aeschynomene (Aeschynomene americana L.) and phasey bean (Macroptilium lathyroides [L.] Urb.). Diet composition, as determined by microhistological analysis of fecal samples, and animal performance were evaluated in three grazing periods: summer 1987 and spring 1988 (2.0, 3.5, and 5.0 steers/ha) and summer 1988 (3.0, 5.3, and 7.5 steers/ha). Stocking rate did not affect percentage of the selectively grazed legumes, aeschynomene and phasey bean, in the diet. Average daily gain decreased linearly (P less than .05) with increased stocking rate, as is typical for grass pastures. Aeschynomene and phasey bean contributed to diets during the first summer, and carpon desmodium contribution was greater in the second summer. These results indicate that this pasture mixture can provide legume herbage from aeschynomene and phasey bean in the year of sowing and from carpon desmodium thereafter. Over the range of grazing pressures obtained, legume responses were generally consistent; thus, optimizing stocking rate for gain per hectare or for economic returns can be targeted without additional constraints to maintain the contribution of these legumes to grazing livestock.     

Ruminal escape protein supplementation and zeranol implantation effects on performance of steers grazing winter annuals.

Fifty-four crossbred steers (275 kg) were assigned randomly to one of three isoenergetic but not isonitrogenous ruminal escape protein (EP) supplements: high ruminal escape protein (HEP), low ruminal escape protein (LEP), or corn. The supplements contained corn, distillers' dried grains with solubles (DDGS), and fish meal. Supplements were fed at approximately 1.5 kg/d; the HEP and LEP supplements provided .25 and .12 kg more EP per day than corn, respectively. These supplements also supplied .20 and .10 kg more CP per day than corn. Fish meal and DDGS provided 66.7 and 33.3% of the supplemental EP, respectively. One-half of the steers in each supplement treatment were implanted once with 36 mg of zeranol. Steers grazed wheat (Triticum aestivum L.)-annual ryegrass (Lolium multiflorum Lam.) pastures for 73 d (March 1 to May 12). Daily gains (kg/d) increased linearly (P less than .07) as EP increased (HEP, 1.61; LEP, 1.54; corn, 1.47); responses were apparent only during the later periods as forage quality declined. Zeranol implants increased (P less than .02) ADG (kg/d) by 9.7% (1.58 vs 1.44). After grazing, all cattle were fed a finishing ration for 76 d. Pre-feedlot EP level produced a negative linear (P less than .04) response on feedlot ADG (kg/d) (HEP, 1.44; LEP, 1.50; corn, 1.59). Zeranol implantation during the grazing phase did not affect (P greater than .2) performance during the feedlot phase or carcass characteristics other than increased ribeye area (P less than .08). Compensatory feedlot performance negated all weight gain advantages elicited by EP supplementation during the grazing period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Corn oil or corn grain supplementation to steers grazing endophyte-free tall fescue. I. Effects on in vivo digestibility, performance, and carcass quality

Twenty-eight Angus (289 +/- 3.8 kg) steers were used in a completely randomized design to evaluate the effect of isocaloric supplementation of 2 different energy sources to steers rotationally grazing tall fescue pastures for 197 d in comparison to positive and negative controls. Steers were supplemented with either corn grain (0.52% BW on a DM basis; PC) or soybean hulls plus corn oil (0.45% BW on a DM basis + 0.10% BW on an as-fed basis; PO) using Calan gates for individual intake measurement. Negative, pasture only (PA), and positive, high-concentrate control diets (85% concentrate:15% roughage on DM basis; C) were also included in the study. Steers on PC, PO, and PA treatments were managed together under a rotational grazing system, whereas C steers were fed a high-concentrate diet for the final 113 d using Calan gates. Forage DMI and apparent DM and NDF digestibility for the grazing treatments were evaluated using Cr(2)O(5) and indigestible NDF as digesta markers. Energy supplementation decreased (P = 0.02) forage DMI (% of BW) with respect to PA, but not (P = 0.58) total DMI. There were no differences (P = 0.53) among grazing treatments on apparent total DM digestibility. However, NDF digestibility was less (P < or = 0.05) in PC than in PO and PA; the latter 2 treatments did not differ (P > 0.05). Overall ADG was greater (P < 0.01) in supplemented, regardless of type, than in nonsupplemented grazing treatments. During the final 113 d, ADG was greater (P < 0.01) in C than in the grazing treatments. Overall supplement conversion did not differ (P = 0.73) between supplement types and was less (P = 0.006) than C. Carcass traits did not differ (P > 0.05) between energy sources. Dressing percentage and HCW were greater (P < 0.01) in supplemented cattle than in PA. Fat thickness and KPH percentage for PA were less (P < 0.05) than for PO but did not differ (P > 0.14) from PC. Marbling score, LM area, and quality grade did not differ (P > 0.05) between grazing treatments. Hot carcass weight for C was heavier (P < 0.001) than for pastured cattle. Quality and yield grades of C carcasses were also greater (P < 0.001) than carcasses from pastured steers. Energy supplementation, regardless of source, to grazing steers increased ADG, dressing percentage, and carcass weight compared with PA steers; however, supplemented steers had less ADG, efficiency, dressing percentage, and carcass weight compared with high-concentrate finished steers.