THE EFFECTS OF SUPPLEMENTATION FREQUENCY AND AMOUNT OF UREA IN DRY SUPPLEMENTS ON INTAKE AND DIGESTIBILITY OF LOW-QUALITY TALLGRASS-PRAIRIE FORAGE BY BEEF STEERS

Sixteen ruminally fistulated ste e rs were used to evaluate the effects of altering supplementatio n frequency and including urea in dry supplements on f orage intake and digestion. Intake of low-quality tallgrass-prairie hay was not affected by supplementatio n frequency or by the inclusion of u rea. Supplementing cattle less frequently resulted in a decrease in diet digestion. Howe v er, we observed a slight trend for reduced su p plementation frequency to exert a greater impact when cattle were fed supplements that contained urea.


Introduction
Because of the higher costs associated with true protein use in winter supplements, producers have been interested in the use of urea as a substitute for a portion of the degradabl e intake protein (DIP) present in supplements.Al so large-scale supplementation of cattle may entail the feeding of supplements on a less than daily schedule.Previous research at Kansas State University indicates that urea can replac e up to 30% of the supplemental DIP in dry supplements with little effect on forage intake and digestion or livestock performance.Similarly , research conducted on supplementatio n frequency indicated that dry supplements that d o not contain urea can be fed on a less than daily schedule without adverse effects on performance.The objective of our study wa s to evaluate whether urea inclusion in winter range supplements would alter the respons e to changing supplementation frequency.

Experimental Procedures
Sixteen Hereford x Angus steers (average BW = 555 lb) with ruminal fis t ulas were housed in individual tie stalls and had ad libitum access to low-quality tallgrass-prairie hay (5.6% CP, 68.4% NDF).
Steers were assigned to treatment s consisting of two supplementation frequencie s (daily and alternate day) and inclusion of urea at 30% of the DIP or no urea.Supplement s were formulated to contain 30% CP (approximately 70% of the C P was DIP) and were composed of rolled sorghum grain, soybea n meal, urea (30% treatment only), dry molasses, and miner als.The amount of supplement fed (as-fed basis) was .46% of BW/daily or .92% of BW every other day.Based on previou s research, the amount of supplement fed should have provided sufficient DIP to maximize forage i ntake.Supplements were fed in the early morning, and complete supplement consumptio n generally occurred within 45 minutes.A nimals were adapted to the diets for 14 days followed by a 6-day fecal collection period dur ing which feed offered, feed refused, and fecal output were recorded.

Results and Discussion
Forage organic matter (OM) intak e and total OM intake were not affected (P>.57) by frequency of supplement feeding or urea inclusion in the supplement (Table 1).Similarly, including urea in the supplement, when considere d on its own, did not significantly affect OM or neutral detergent fiber (NDF) digestion.Digestion of OM and NDF was depressed (P#.06) by supplementing less frequently.However, there was a slight tendenc y (P=.13 for OM and P=.19 for NDF digestion) for supplementation frequency to interact with urea inclusion in the supplement.In general, cattle fed the supplement that contained 30% of the DIP from urea responded more dramatically to changes in supplementatio n frequency than did those fed supplements without urea.Supplemen t refusal can be a problem with dry supplements, if urea is included at a high level.With feeding every other day, some steers in this trial were given as much as 5.8 lb (as fed) to consume in a single feeding (.92% of BW).In general , supplement consumption was not a problem, but we observed a trend, over time, for steers fed the largest amount of supplement on alternate days to refuse some of the supplement, although the amount was seldom more than .25 lb.In these cases, the supplemen t was placed directly into the rumen to ensure a legitimate comparison of supplemen t effects on intak e and digestion.In conclusion , intake of low-quality tallgrassprairie hay was no t affected by supplementation frequenc y or by low-level inclusion of urea in a dry supplement.However, digestion may be somewha t lower for cattle supplemented less frequently.This may be particularly true when a dry supplement contains part of its DIP in the form of urea.

Table 1 . Effect of Supplementation Frequency and Inclusion of Urea as a Portion of the Supplement DIP on Intake and Digestion
a OM = organic matter; NDF = neutral detergent fiber.b