G. W. Horn

Forage intake by beef steers grazing winter wheat with varied herbage allowances

Two grazing trials were conducted in separate years on a 5.86 ha winter wheat (Triticum aestivum var. Chisholm) pasture divided into 10 experimental paddocks. Paddocks were differentially grazed with beef steers to produce an array of different herbage mass levels, expressed as kg dry matter (DM)/ha. Each experimental paddock was then continuously stocked with 3 beef steers during each 7-day forage intake trial. Daily forage intake, expressed as kg organic matter (OM)/100 kg body weight (BW), was estimated from fecal output (Cr2O3 dilution) of the beef steers and in vitro organic matter disappearance of esophageal masticate collected from each paddock. Estimated daily gain was calculated from forage intake and net energy values calculated from organic matter disappearance data. Forage intake, organic matter disappearance, and estimated daily gain were related to daily herbage allowance, expressed as kg DM 100 kg BW-1 day-1, and herbage mass utilizing a quadratic equation with a plateau function. As herbage allowance increased, organic matter disappearance improved (Y = 62.18 + 1.08 herbage allowance -.022 herbage allowance2; r2 = .64, MSE = 5.06) as did forage intake (Y = 1.3 + .12 herbage allowance -.003 herbage allowance2; r2 = .52, MSE = .07), and estimated daily gain (Y = -.059 + .12 herbage allowance -.003 herbage allowance2; r2 = 59, MSE = .07). Plateaus were achieved at herbage allowance between 20 to 24 kg DM 100 kg BW-1 day-1. Results of this study indicate forage intake and estimated daily gain declined severely as herbage allowance fell below 20 to 24 kg DM 100 kg BW-1 day-1. This data may provide a threshold herbage allowance for initiation of energy supplementation programs for growing cattle on wheat pasture.

Genetic trends in winter Wheat yield and test weight under dual-purpose and grain-only management systems

Wheat (Triticum aestivum L.) cultivars of the southern Great Plains are traditionally bred in environments managed for grain production only but are commonly grown for the dual-purpose of producing winter forage and grain from the same crop. To what extent grain yield and test weight are consistently expressed in those environments requires investigation relative to long-term attempts to improve them genetically. A historical set of hard red winter (HRW) wheat cultivars was evaluated under grain-only and dual-purpose management systems to compare their agronomic performance and derived estimates of genetic progress. Separate experiments were established for each system featuring whole-plot treatments of a foliar fungicide and split-plot treatments of 12 cultivars. The study was conducted for 3 yr at the Wheat Pasture Res. Ctr. near Marshall, OK. Dual-purpose experiments were generally grazed from November through February. Yield in the grain-only system improved 18.8 kg ha -1 yr -1 , equivalent to 1.3% of the mean yield for Turkey. The rate of progress in the dual-purpose system was significantly lower at 11.3 kg ha -1 yr -1 , equivalent to 0.9% of the mean for Turkey. Management for grazing had a more profound influence on estimates of yield improvement than did management for disease protection. Linear trends in test weight were not evident under either system, nor were cultivar differences influenced by management system consistently across years. Breeding practices should emphasize selection for grain yield in both environments if future progress is to be maximized in both.

Effects of winter growing programs on subsequent feedlot performance, carcass characteristics, body composition, and energy requirements of beef steers

The purpose of this study was to investigate the effects of winter growing program on subsequent finishing performance, carcass merit, and body composition of beef steers. Four steers were slaughtered to determine initial body composition. Remaining steers (n = 256) were blocked by BW and randomly allotted to 1 of 4 treatment groups: 1) ad libitum fed a high-concentrate diet (CF), 2) grazed on wheat pasture (WP), 3) fed a sorghum silage-based diet (SF), or 4) program fed a high-concentrate diet (PF). Steers in the WP, SF, and PF groups were managed to achieve approximately equal rates of BW gain. After the growing phase (112 d), 6 steers were randomly selected from the WP, SF, and PF treatments for determination of body composition. Remaining steers were adapted to a high-concentrate diet for finishing and slaughtered at 1.27 cm of 12th-rib fat. Six steers from each treatment were used to determine carcass, offal, and empty body composition. During the growing phase, WP, SF, and PF steers gained 1.15, 1.10, and 1.18 kg/d, respectively, and ME intake did not differ (P = 0.50) among treatments. Program-fed and SF steers had greater (P < 0.05) offal and empty body fat content than WP steers. Gain in offal and empty body fat was greatest (P < 0.05) for PF steers, intermediate for SF steers, and least for WP steers. During the finishing phase (123, 104, 104, 196 d for WP, SF, PF, and CF, respectively) DMI was greater (P < 0.01) for SF steers (10.9 kg/d) than for PF steers (10.1 kg/d); WP steers were intermediate (10.4 kg/d). Daily BW gain was greatest (P < 0.05) for SF steers (2.02 kg/d), intermediate for PF steers (1.85 kg/d), and least for WP and CF steers (1.64 and 1.63 kg/d, respectively). Accretion (kg/d) of carcass and empty body mass was less (P < 0.05) for WP and CF steers compared with PF and SF steers. Calf-fed steers had greater (P < 0.05) fat content of offal than SF and PF steers; WP steers were intermediate. Gain in empty body and carcass energy (Mcal/d) was greater (P < 0.05) for PF steers than CF steers with SF and WP steers being intermediate. At slaughter, SF steers had reduced (P < 0.01) yield grades and greater marbling scores compared with CF and WP steers; PF steers were intermediate. In conclusion, growing programs that increase fat composition of feeder calves did not negatively affect subsequent finishing performance. Finishing steers as calves may reduce retained energy of carcass tissues and increase internal fat during high-grain feeding compared with steers that previously underwent a growing program.

Optimal Stocking Density for Dual-Purpose Winter Wheat Production

Dual-purpose winter wheat production is an important economic enterprise in the southern Great Plains of the United States. Because of the complex interactions involved in producing wheat grain and beef gain from a single crop, stocking density is an important decision. The objective of the research is to determine the stocking density that maximizes expected net returns from dual-purpose winter wheat production. Statistical tests rejected a conventional linear-response plateau function in favor of a linear-response stochastic plateau function. The optimal stocking density of 1.48 steers/ha (0.60 steers/acre) is 19% greater with a stochastic than with a nonstochastic plateau.

Supplementation of dried distillers grains with solubles to beef cows consuming low-quality forage during late gestation and early lactation.

Three experiments were conducted to evaluate supplementation of dried distillers grains with solubles (DGS) to spring-calving beef cows (n = 120; 541 kg of initial BW; 5.1 initial BCS) consuming low-quality forage during late gestation and early lactation. Supplemental treatments included (DM basis) 1) 0.77 kg/d DGS (DGSL); 2) 1.54 kg/d DGS (DGSI); 3) 2.31 kg/d DGS (DGSH); 4) 1.54 kg/d of a blend of 49% wheat middlings and 51% cottonseed meal (POS); and 5) 0.23 kg/d of a cottonseed hull-based pellet (NEG). Feeding rate and CP intake were similar for DGSI and POS. In Exp. 1, cows were individually fed 3 d/wk until calving and 4 d/wk during lactation; total supplementation period was 119 d, encompassing 106 d of gestation and 13 d of lactation. Tall-grass prairie hay (5.6% CP, 50% TDN, 73% NDF; DM basis) was fed for ad libitum intake throughout the supplementation period. Change in cow BW and BCS during gestation was similar for DGSI and POS (-5.0 kg, P = 0.61 and -0.13, P = 0.25, respectively) and linearly increased with increasing DGS level (P < 0.01). Likewise, during the 119-d supplementation period, BW and BCS change were similar for DGSI and POS (-72 kg, P = 0.22 and -0.60, P = 0.10) and increased linearly with respect to increasing DGS (P < 0.01). The percentage of cows exhibiting luteal activity at the beginning of breeding season (56%, P = 0.31), AI conception rate (57%, P = 0.62), or pregnancy rate at weaning (88%, P = 0.74) were not influenced by supplementation. In Exp. 2, 30 cows from a separate herd were used to evaluate the effect of DGS on hay intake and digestion. Supplementation improved all digestibility measures compared with NEG. Hay intake was not influenced by DGS (P > 0.10); digestibility of NDF, ADF, CP, and fat linearly increased with increasing DGS. In Exp. 3, milk production and composition were determined for cows (n = 16/treatment) of similar days postpartum from Exp. 1. Daily milk production was not influenced by supplementation (6.3 kg/d, P = 0.25). Milk fat (2.1%) and lactose (5.0%) were not different (P > 0.10). Milk protein linearly increased as DGS increased (P < 0.05) and was greater for DGSI compared with POS. Similar cow performance was achieved when cows were fed DGS at the same rate and level of CP as a traditional cottonseed meal-based supplement. Increasing amounts of DGS did not negatively influence forage intake or diet digestibility.

Timing of Grazing Termination in Dual-Purpose Winter Wheat Enterprises1

Timing of grazing termination is a key management variable in maximizing income from dual-purpose winter wheat enterprises. The objective of this research was to determine the effect of grazing hard red winter wheat pasture past first hollow stem (FHS) on steer BW gain and subsequent grain yield, and to develop production functions relative to time of grazing termination. Grazing trials were initiated at the emergence of FHS on March 13 and 5 of 2003 and 2005, respectively. Angus steers (greater than 7/8 Angus) grazed 4 clean-tilled, dryland winter wheat pastures in 2003 (n = 52; 405 ± 30 kg) and a single pasture in 2005 (n = 34; 357 ± 42 kg). Forage allowance averaged 199 kg DM/100 kg BW during 2003 and 133 kg DM/ 100 kg BW during 2005. Beginning in

Effect of ammoniation and energy supplementation on the utilization of wheat straw by sheep

Abstract Two experiments were conducted with mature wethers to study the effects of ammoniation of wheat straw and type (Experiment 1) and level (Experiment 2) of energy supplementation on straw intake, digestion and utilization of nutrients. In Experiment 1, sheep were fed coarsely chopped untreated (US) or ammoniated wheat straw (AS). The AS diets were supplemented with whole shelled corn (WSC), cottonseed hulls (CSH) or both. A fourth diet of US was supplemented with WSC, CSH and urea (5 g per head per day). Whole shelled corn and CSH were fed daily in amounts of 10 and 5 g per 0.75 kg, respectively. In Experiment 2, treatments consisted of coarsely chopped US and AS and 3 levels of supplemental WSC (i.e., 0, 10 or 20 g per 0.75 kg) fed daily. Sheep fed US were also supplemented daily with 15 g urea per head. Straw intake of sheep supplemented with WSC and CSH was increased 30% (not significant, P > 0.05) by ammoniation in Experiment 1, and was increased 33% ( P P 0.75 in Experiment 2. Apparent digestibility of total diet neutral detergent fiber remained unchanged with WSC supplementation in Experiment 1, but decreased linearly ( P 3 -N concentrations after feeding ( P P P 3 -N concentrations decreased linearly ( P P −1 ; Y ) on digestible OM intake (DOMI, g per 0.75 kg; X ) observed in Experiment 2 resulted in the following relationships: (US) Y = 0.74 + 0.079 X ; ( R 2 = 0.06, n = 24); (AS) Y = −5.67 + 0.240 X ( R 2 = 0.46, n = 24). For every g per 0.75 kg increase in DOMI, the increase in N retention was 3-fold greater ( P

Cool Season Perennial Grasses as Complementary Forages to Winter Wheat Pasture1

ABSTRACT Three grazing trials with growing cattle were conducted to evaluate three cool season perennial grasses (Manska pubescent wheatgrass, Lincoln smooth bromegrass, and Paiute orchardgrass) as complementary forages for winter wheat pasture. Initial stocking rate averaged 1,359 kg BW/ha for approximately 60 d in the two spring trials (April and May) and 857 kg BW/ha for 40 d in the fall trial (late September and October). The ADG and gain per hectare averaged, respectively, 0.86 kg/d and 287 kg/ha and 0.50 kg/d and 59 kg/ha for the spring and fall trials. Generally, neither animal growth performance nor production per hectare was different among the three grasses. However, OM of wheatgrass was more digestible, and its CP was more ruminally degradable, than that of the other grasses. Crude protein concentrations of the grasses generally ranged from 13.6 to 32.4% of DM and were more than adequate to support BW gains of 1 kg/d for growing cattle. Grazing days per hectare and BW gain per hectare from the fall grazing period were only about 30 and 20%, respectively, of the totals for spring and fall 1999, which supports previous findings that most of the production of these grasses occurs in the spring. Orchardgrass was the least resistant to summer drought. Cattle must be removed from dual-purpose winter wheat at the first hollow stem stage of maturity in late winter. However, late winter forage production of these cool season perennial grasses was inadequate to serve as complementary forage to dual-purpose winter wheat.

Optimal Grazing Termination Date for Dual-Purpose Winter Wheat Production

Dual-purpose winter wheat (fall-winter forage plus grain) production is an important economic enterprise in the southern Great Plains. Grazing termination to enable grain production is a critical decision. The objective is to determine the optimal grazing termination date for dual-purpose wheat. The value of knowing the occurrence of first hollow stem (FHS), a wheat growth threshold for grazing termination, is also determined. Results indicate that for most price situations grazing should be terminated at or before FHS. Marginal wheat returns from extended grazing were negative and the value of FHS information ranges from

ENERGY SUPPLEMENTATION STRATEGIES FOR WHEAT PASTURE STOCKER CATTLE UNDER UNCERTAIN FORAGE AVAILABILITY

1.50 to