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.
Materials and Methods
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.
Results and Discussion
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).
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Table 1. Influence of supplement on performance and intake of yearling steers grazing native range. |
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| Item | Control | Salt | Anionic Salt |
Calcium Hydroxide |
Hand Fed |
StdErr |
| 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 | |
| ADG, lb/day | 1.23 | 1.96 | 1.59 | 1.58 | 1.83 | 0.11 |
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Table 2. Influence of 28-day period on average daily gain of yearling steers. |
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| Item | ADG (Lbs/day) |
StdErr |
| Period 1 | 2.67 | .20 |
| Period 2 | 2.60 | .20 |
| Period 3 | 1.99 | .20 |
| Period 4 | -0.12 | .20 |
Conclusions
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
E-mail: glardy@ndsuext.nodak.edu
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