Materials and Methods
Results and Discussion
Salt is the most effective limiter for self-fed supplements for yearling steers grazing native range.
Our objective was to compare animal performance and effectiveness of three self-limiting supplements fed to cattle on pasture. Seventy Simmental cross yearling steers were stratified by weight and allotted randomly to one of ten 40 acre pastures in each of two years. Five treatments were utilized: control (no supplement); 16% salt; 5.25% anionic salts (ammonium chloride and ammonium sulfate); 7% calcium hydroxide; and hand fed (no limiter). Supplement intakes were higher (P < .05) for salt and anionic salts than hand fed, and higher (P < .01) for anionic salts than calcium hydroxide. Supplementation increased (P < .05) final weights over the control, with salt having increased (P < .05) final weights over anionic salts and calcium hydroxide. Average daily gain for salt was higher (P < .05) than control. Salt appears to be the most effective self-limiter for yearling steers grazing native range.
Grasslands in the Northern Great Plains provide the primary forage for growing livestock from late spring to early fall. Forage for intake is adequate, however, nutrient quality begins to decline as early as July. Therefore, producers need to be concerned with meeting the first limiting nutrient of their growing livestock. Supplementation of the limiting nutrients is one method for improving livestock performance during periods of nutritional stress. Various supplementation techniques exist; daily or hand-feeding, block or liquid supplements, and self-limiting supplements. Optimizing the amount of supplement consumed, without limiting the availability of the limiting nutrients, is the primary concern for a supplementation program. Various self-limiting supplements are available to producers currently, many using salt as the physiological limiter to intake.
Seventy Simmental cross yearling steers (avg initial wt = 769 lbs) were used in each of two years to evaluate different self-limiting supplements for yearling cattle grazing native range. Steers were stratified by weight and allotted randomly to supplemental treatment in one of ten 40 acre pastures of similar plant community structure. Steers were dewormed with Dectomax, implanted with Synovex-S, vaccinated with a viral 4-way and bacterial 7-way, and preconditioned on supplement prior to the start of the trial. Stocking density was determined so forage was not limiting; 1.5 acres/AUM. Pastures were located at the NDSU Central Grasslands Research and Extension Center on 400 acres of native mixed grass prairie. Experimental periods for year 1 consisted of three 28-day periods starting July 20 and ending October 12. Year 2 consisted of four 28-day periods beginning June 21 and ending October 8. Treatments were (2 pastures per treatment per year): control, no supplement; 16 % salt; 5.25 % anionic salts (ammonium chloride and ammonium sulfate); 7 % calcium hydroxide; and hand fed. Supplements (22% crude protein) were based on wheat midds, barley malt sprouts, and soybean hulls. Calcium hydroxide was fed in meal form, all other supplements were pelleted. Supplements containing limiters were fed in portable feeders. Hand-fed supplements were fed in bunks. Dietary cation anion differences (DCAD; Na + K - Cl - S) for salt, anionic salts, calcium hydroxide, and hand fed, of supplement were 12.9, -75.7, 13.9, and 14.3 mEq / 100 g, respectively. Steers were weighed and rotated through pastures monthly, with feed intake monitored daily. Herbage disappearance and nutritional levels (10% crude protein, 57% in vitro organic matter digestibility) were monitored through exclosures and cannulated heifers.
Supplement intakes were higher (P < .05) for salt and anionic salts than hand fed and higher (P < .01) for anionic salts than calcium hydroxide, but increased (P < .05) for all treatments across periods (Table 1). Supplement intake (% of body weight) was lower (P < .05) for hand fed than salt and anionic salts, and calcium hydroxide was lower (P < .05) than anionic salts. Supple mentation increased (P < .05) final weights over control. Final weight for salt was higher than anionic salts and calcium hydroxide. Anionic salts, calcium hydroxide, and hand fed had similar final weights. Average daily gain for salt was higher (P < .05) than the control in both years. Average daily gain was un-affected (P > .05) by supplementation for periods 1, 2, and 3 and decreased (P< .05) by period 4 (Table 2).
Table 1. Influence of supplement on performance and intake of yearling steers grazing native range.
|Initial wt, lb||768||772||771||771||762||6.00|
|Final wt, lb||889||963||930||927||942||10.00|
|Supplement intake, lb/day||5.47||6.27||4.68||3.95||0.41|
|Intake, % of BW||0.61||0.72||0.53||0.46||0.04|
Table 2. Influence of 28-day period on average daily gain of yearling steers.
Based on supplement intake and final weights, salt appears to be the most effective self-limiter for yearling steers grazing native range. Supplementation during the summer can increase performance, but supplement intake must be monitored to optimize the cost of gain. Grazing yearling steers on native range after September 10 does not enhance performance.
Dr. Greg Lardy
Animal and Range Science Department
North Dakota State University
Box 5727 State University Station
Fargo, ND 58105