Effects of season and diet, including costs,
on feedlot performance of bison

Bryan Miller and Vern Anderson
Double MM Bison Ranch, Carrington ND,
and Carrington Research Extension Center , NDSU

Summary
Weaned bison bull calves (n=78; avg wt. 471 + 18 pounds) were randomly assigned to four different feedlot diets in a 4 treatment by 4 period Latin square study. The feeding periods were 80 days long and closely associated with spring, summer, fall and winter seasons. The four dietary treatments were identified based on major ingredients in the formulation and are described as 1)wheat screenings, 2) wheat middlings, 3) crambe meal and 4) a commercial bison ration. A significant season effect (P<.10) was observed for gain with winter gains lower (P<.01) than spring, summer and fall. Gains averaged 1.73 lbs. during the spring, 1.38 lbs. during the summer, 1.76 lbs. during the fall, and 38 lbs. during the winter. Average daily gains were 1.73 lbs for wheat screenings, 1.63 lbs. for wheat middlings, 1.53 lbs. for crambe meal, and 1.61 lbs. for the commercial diet during the 242 days of spring summer and fall seasons. Wheat screenings gains were higher (P=.07) than crambe meal with wheat midds and the commercial diet intermediate. No differences were detected due to dietary treatment for dry matter intake, intake per unit weight, and dry matter per gain. Feed costs per pound of gain were $.54 for wheat screenings, $.73 for wheat middlings, $.73 for crambe meal, and $.89 for the commercial diet. Bison in this study gained less in the winter than other seasons, consumed a variety of feeds with limited differences in performance that resulted in highly variable feed cost per pound of gain.
Key words: Bison, feedlot, season, diet, feed cost

Introduction
The rapidly growing bison industry in the northern plains has producers looking for information on what feeds can be used for bison in the feedyard. In some intensively managed operations, bison calves are weaned in the fall, separated by sex, and started on feed. Bull calves are confined in a lot and fed until slaughter. The feeding period is often a year or more as bison eat less and gain slower than beef (Koch, et al., 1995). Winter gains are a particular concern with very low and erratic gains experiences by many bison feeders (Stanton and Schutz, 1995). A natural trait of bison is to self limit intake of concentrate feeds. Self feeders are frequently used without concern for overeating or acidosis, however accumulation of fines may reduce intake. Many bison producers use a completely pelleted wheat screenings based diet which includes corn, molasses and mineral supplements. As bison numbers increase and the availability of wheat screenings varies from year to year, producers need information on other feeds. A number of alternative or co-product feeds are available in the northern plains. A feeding trial was partially funded by North Dakota Agricultural Products Utilization Commission to compare four different diets for bison fed during four seasons of the year.

Materials and Methods

Seventy eight fall weaned bison bull calves averaging 471.0 + 18.1 pounds were randomly allotted to one of four dietary treatments and assigned to identical 50 by 100 foot feedlot pens on February 5, 1993 at the Double MM Bison Ranch, near Carrington, ND. Four feeding periods in the Latin square design were closely associated with spring, summer, fall, and winter. Feeding periods started on February 15, May 5, July 25, and October 14. Dietary treatments were identified based on major or unique ingredients in the diet. They were 1)wheat screenings, 2) wheat midds, 3) crambe meal, and 4) a commercial bison ration. Formulations are given in Table 1 for the first three diets. No formulation was available for the commercial bison feed. The wheat screenings diet commonly used by many bison producers was considered the control. Wheat screenings are highly variable in composition but generally consists of green and yellow foxtail seed , commonly called pigeon grass (60-80%), cracked wheat (10-20%), and other weed seeds. Wheat middlings were from durum, milled for the production semolina used to make pasta. Middlings from hard red wheat and durum are generally similar in nutrient content and co-mingled for marketing. Crambe meal is an oil seed meal (35% protein) remaining after removal of the high erucic acid industrial oil from crambe seed. Crambe is a close relative of rape, and canola. It is a new crop in the northern plains with limited acreage. The commercial diet used a wheat midds base and contained a minimum of 12% crude protein, 2% crude fat and a maximum of 12% crude fiber. Nutrient analysis of the four diets on a dry matter basis is given in table 2.

The pelleted rations were offered in identical self feeders in the center of each pen. Bison calves in all four pens were offered the same low quality grass hay free choice in large round bale feeders. Water was available from heated fountains in the corner of each pen.

Calves were weighed at the start of the study, and at the end of each feeding period. Bison in each pen were rotated to a different pen and a different feed after each period.

Data were analyzed using general linear model procedures according to SAS (SAS, 1988). Pen was the experimental unit and period the replicate. Analyses were conducted for the main effects of diet, pen and season and diet x season interactions.

Results and Discussion
Daily gains were significantly lower (P<.05) during the winter feeding period than during spring, summer, and fall. Gains were 1.73, 1.38, 1.76 and .38 +.25pounds per day respectively for spring, summer, fall and winter (Table 3). Dry matter intake was higher (P<.05) during fall and winter than spring and summer which may be due in part to heavier animals. Intake per unit weight was not different throughout the four periods. Table 3 presents feedlot performance information by season. Dry matter per gain appears to increase throughout the study suggesting decreased feed conversion as the bison grew. However, the low gains and tremendous variation during the winter contribute to a very high standard error in that period.
Poor performance during the winter may be due to a photoperiod effect on intake by bison (Stanton and Schutz, 1995). Wild species are known to consume large amounts of feed if available during the late summer and fall to store up nutrients for winter (Chistopherson et al., 1979). Lower intake and activity has been observed during colder darker months probably to conserve energy expenditure from activity (Rutley, 1992).
More research is needed on photoperiod effects and possibly develop lighting strategies or feeding regimes to counter this phenomena. An alternative feeding strategy would be to reduce diet energy content for a more natural feeding pattern. However, reduced winter gains could significantly decrease profitability in bison feeding. Artificial lighting has been shown to increase intake in cattle (Peters et al., 1980; Tucker et al., 1984) which may respond less to photoperiod than wild animals due to their long term domestication.
Because of the differences in gain during the winter period, dietary comparisons were made using only the spring, summer, and fall seasons. The wheat screenings diet produced gains significantly higher (P=.07) than crambe meal with gains from the other two diets intermediate. However, crambe meal included in the diet of growing and finishing beef steer calves at up to 17% of intake did not alter consumption or gains (Anderson et al., 1993). Bison bulls gained 1.73, 1.53, 1.63 and 1.61 + .05 pounds per head per day for the wheat screenings, crambe meal, wheat midds, and commercial diets respectively. Table 4 presents information on performance by dietary treatment. Dry matter intake averaged 19.00, 20.05, 20.99 and 21.33 + 2.17 pounds per day. Dry matter intake, feed per pound gain, and intake per unit weight of bison was similar for all treatments. No interactions were observed for diet and season.
Feed costs per pound of gain were $.54 for wheat screenings, $.73 for both crambe meal and wheat midds and $.89 for the commercial feed. Yardage, interest rates, and death loss were not considered in determining feed cost per pound of gain. Keeping feed costs low without reducing gains is imperative for profitable bison feeding. Using alternative feeds from grain processing, especially wheat screenings, appears to produce the lowest feed costs. Feed costs can be highly variable depending on distance to co-product sources and processing facilities as well as labor, handling equipment, and storage facilities for ingredients and finished feeds.

Implications
Results of this study indicate bison will consume rations with a variety of ingredients similar to cattle, provided the diet is palatable and nutritious. The wheat screenings based diet provide the lowest feed cost per unit gain. Screenings, however, may be highly variable in nutrient content depending on the source, year, and several other factors. It is not known if co-product feeds are economically competitive with higher energy feed grains such as corn or barley.

Literature Cited
Anderson, V. L., W. D. Slanger, S. L. Boyles, and P. T. Berg. 1993. Crambe meal is equivalent to soybean meal for backgrounding and finishing beef steers. J. Anim. Sci. 71:2608.

Christopherson, R. J., R. J. Hudson, and M. K. Christopherson. 1979. Seasonal energy expenditures and thermoregulatory responses of bison and cattle. Can. J. Anim. Sci. 59:611.

Koch, R. M., H. G. Jung, J. D. Crouse, V. H. Varel, and L. V. Cundiff. 1995. Growth, digestive capability, carcass, and meat characteristics of Bison bison , Bos taurus, and Bos x Bison. J. Anim. Sci. 73:1271.

Peters, R. R., L. T. Chapin, R. S. Emery and H. A. Tucker. 1980. Growth and hormonal response of heifers to various photoperiods. J. Anim. Sci. 51:1148.

Rutley, B. 1992. Average daily gains of feedlot finished plains bison. Bison Evaluation Unit Bison Bulletin. BB 92:1.

SAS, 1988. SAS/STAT, Users Guide (6.03 Ed.) SAS Institute Inc., Cary, NC.

Stanton, T. L., D. Schutz, W. McFarlane, R. Seedig and D. Stewart. 1995. Effect of concentrate level in bison finishing rations on feedyard performance. Colorado State University.

Tucker, H. A., D. Petitclerc and S. A. Zinn. 1984. The influence of photoperiod on body weight gain, body composition, nutrient intake and hormone secretions. J. Anim. Sci. 59:1610.


Table 1 Formulations of bison feedlot dietary treatments
(Percent as fed)
                      Wheat       Crambe         Wheat
Ingredient         Screenings      Meal          Midds
-------------------------------------------------------
Wheat screenings      66.80         -.-            -.-
Corn grain            15.00        16.00          12.50
Crambe meal            -.-         14.00           -.-
Wheat middlings        -.-         30.00          66.20
Oat hulls              7.50        30.20          11.50
Molasses               5.00         5.00           5.00
TM salt                2.50         2.50           2.50
Vitamins/minerals      3.20         2.30           2.30
-------------------------------------------------------
                     100.00       100.00         100.00	


Table 2. Nutrient analysis of bison dietary treatments
                   Screenings  Crambe Meal  Wheat Midds  Commercial  Hay

                   ----------------Pelleted Diets------------------
Dry matter, %        90.03        89.68        90.01       91.58    87.66
                   ---------------Dry matter basis-----------------
Crude protein, %     14.89        15.11        14.35       14.24     8.29
Acid det. fiber, %   12.34        16.60        11.10       17.91    50.31
Neut. det. fiber, %  21.94        29.53        22.91       35.06    74.10
Ash, %                6.70        10.52         9.11        9.61    11.24
Fat,  %               3.37         3.20         3.39        3.93     1.02
Mcal/gram             4.30         4.19         4.17        4.24     4.07
Phosphorous, %         .75          .71          .52         .61      .09
Calcium, %             .77         1.10          .94        1.14      .59


Table 3 Performance of bison in the feedlot by season of the year
Season                Spring    Summer    Fall    Winter    Std Err
--------------------------------------------------------------------
Avg. wt, lb.           540       665      795      876       12.33
Avg. daily gain, lb.     1.73a     1.38a    1.76a     .38b     .25
Pellet intake, lb.      13.70a    13.34a   19.62b   15.96ab   2.23
Hay intake, lb.          5.94a     7.20ab   8.30b   11.54c     .97
DM intake, lb.          17.67a    18.50a   25.13b   24.75b    1.96
DM intake, % body wt.    3.27      2.78     3.17     2.82      .27
DM intake/gain          10.24a    13.51a   14.41a   66.00b   19.85
--------------------------------------------------------------------
a, b, c - values with different superscripts are significantly different, P<.05


Table 4. Performance of bison in the feedlot by dietary treatment
                    Screenings  Crambe  Wheat midds  Commercial  Std Err
------------------------------------------------------------------------
Initial wt., lb.       463       471       481          469       19.43
Final wt., lb.         883       870       852          840       25.63
Hay intake/day, lb.      7.56      6.59      7.44         7.00      .33
Pellet intake/day, lb.  14.01     15.62     15.82        16.77     2.41
DM intake/day, lb.      19.00     20.05     20.99        21.30     2.17
Avg. daily gain, lb.     1.73x     1.53y     1.63xy       1.61xy    .05
DM intake/gain          11.62     13.21      12.86       13.19     1.70
DM intake, % body wt     2.90      2.99       3.15        3.16      .34
------------------------------------------------------------------------
x,.y values with different superscripts are significantly different, p=.07


Table 5 Economics of feeding bison by dietary treatment
                             Wheat    Crambe    Wheat
                          Screenings   Meal     Midds    Commercial
-------------------------------------------------------------------
Ingredient cost/ton, $ a     67.03     80.70    87.36        -
Pelleted feed cost/ton, $ b 112.03    125.70   132.36      155.00
Hay cost/ton, $              40.00     40.00    40.00       40.00
Feed cost/hd/day, $            .94      1.11     1.20        1.44
Feed cost/lb gain, $           .54       .73      .73         .89
-------------------------------------------------------------------
a Based on ingredient prices of $30/ton for wheat screenings, $2.25/bu for corn, $70/ton for crambe meal, $70/ton for wheat midds, $30/ton for oat hulls, $150/ton for molasses , $165/ton for TM salt and $34.00/cwt for vitamin-mineral mixture
b Includes flat storage, trucking and pelleting costs of $45/ton
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