Agronomic traits and growing cattle performance for whole-plant Agronomic traits and growing cattle performance for whole-plant corn and forage and grain sorghum silages corn and forage and grain sorghum silages

Summary Agronomic and cattle performance traits were measured for the following silages produced in 1992: irrigated Pioneer 3377 corn, ensiled with or without Biotal® silage inoc-ulant; DeKalb 42Y grain sorghum; and Cargill 200F, Pioneer 947, DeKalb FS-5 and FS-25E, and Northrup King (NK) 300 forage sorghums. All sorghums were grown under dryland conditions. The irrigated corn had the highest whole-plant dry matter (DM) and grain yields, and NK 300 and DeKalb FS-5 had the highest whole-plant DM yields among the sorghums. NK 300 also had the highest grain yield among the sorghums; DeKalb FS-5 and FS-25E had the lowest. Steers fed the irrigated corn silages had the fastest and most efficient gains, and the late-season forage sorghum, DeKalb FS-25E, produced the slowest and least efficient gains. Inoculating the corn silage increased DM recovery, fermentation efficiency, and steer gain per ton of crop ensiled.


Introduction
Silage production in Kansas is primarily from irrigated or dryland corns and dryland grain and forage sorghums.In several previous studies, we have documented the effects of growing condition, hybrid, stage of maturity, processing, grain addition, and climate (i.e., growing season) on the yield potential and nutritive value of numerous corn and sorghum silages.The objectives of this study were to compare both agronomic traits and cattle performance from silages produced in the 1992 growing season.

Experimental Procedures
The crops were grown near the Kansas State University campus during the 1992 season.The eight silages included irrigated Pioneer 3377 corn (with or without Biotal silage inoculant); drylan d DeKalb 42Y grain sorghum; and Cargill 200F, Pioneer 947, DeKalb FS-5, Northrup King 300, and DeKalb FS-25E dryland forage sorghums.The two fields used were predominantly Reading silt loam soil.Prior to planting, anhydrous ammonia was applie d at 100 lb per acre for the irrigated corn and dryland grain sorghum, and 80 lb per acre for the five forage sorghums.The corn was harvested at the 90% milk line stage of kernel maturity, and the six sorghums, at the very late-dough stage.All eight sila ges were made in 10 × 50 ft concrete stave silos.The silos containing the two corn silages were filled by the alternate load method.
The silos were opened on June 1 0 and 11, 1993 and emptied at uniform rates during the next 3 months.Silage samples were taken three times weekly.Each silage was fed to 16 yearling, crossbred steers (four pens of four steers per silage) in a 77-day growing trial, which began on June 15, 1993.The complete mixed rations were fed twice daily to appetite and contained (DM basis) 89% silage and 11% supplement.Supplements were formulated to provide rations of 12.0% crude protein, .50%calcium, and .30%phosphorus (DM basis); 250 mg of rumensin and 30,000 IU of vitamin A per steer daily.
For 5 days before the start of the growing trial, all steers were limit-fed a forage sorghum silage ration to pr o vide a DM intake of 2.0% of body weight.Steers then were weighed individually on 2 consecutive days.For 3 days before the final weighing, the steers were fed their respective silage rations at a restricted DM intake of 2.0% of body weight.Then individual weights were taken on 2 consecutive days.

Results and Discussion
Agronomic performance and chemical composition of the seven silage crops are shown in Table 1.The corn and DeKalb FS-5 and NK 300 had the highest wholeplant DM yields per acre; the late-season forage sorghum (DeKalb FS-25E) had the lowest DM yield.Grain yields of the five forage sorghums were above average and were highest for NK 300 and Pioneer 947.The CP values were lower and ADF values higher for the five forage sorghums than in previous years (KAES Report of Progress 678, page 16), which suggest s that all were of lower than expected nutritional values.Gains and efficiencies were not related to the percent grain in the silages but were closely related to the silage ADF content.
Average daily gains and efficiencies of gain (Table 2) were excellent for steers fed the two corn silages and the DeKalb 42Y grain sorghum silage.As expected, the corn silages produced the fastest an d most efficient gains.Steers fed the grain sorghum silage had the highest daily DM intake, whereas those receiving the late-season forage sorghum, DeKalb FS-25E, had the lowest DM intake and slowest and least efficient gain.Gains and efficiencies were poorer for steers fed the five forage  sorghum silages than for those fed the corn or grain sorghum silages.
Treating the corn silage with Biotal silage inoculant did not affect rate or efficiency of gain.However, the inoculant increased DM recovery by .9percentage units compared to the control (91.7 vs. 90.8% of th e crop DM ensiled).
The inoculated silage also had a lower pH (3.72 vs. 4.02); more lactic acid; a higher lactic to acetic acid ratio (2.2 vs. 1.2); and less acetic acid, ethanol, and ammonia nitrogen compared to the control silage.When the DM recovery and feed efficiency results were combined, the inoculated corn silage produced 3.6 lb more steer gain per ton of crop ensiled than the control silage.
a CP = crude protein, ADF = acid detergent fiber.Both are reported on a DM basis.b The Biotal-treated and untreated corn silages had similar CP and ADF contents and only the mean c values are reported.

Table 2 . Performance by Yearling Steers Fed the Eight Silage Rations in 1993
LSD = least significant difference.Means that differ more than the LSD are statistically different (P<.05) a DM basis.b