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1999 Beef & Bison Production Field Day


Laboratory Scale Evaluation of Cull Potato Silages

Greg Lardy, Karl Hoppe, Marc Bauer and Don Heuchert

North Dakota State University Extension Service,

Fargo and Carrington

NDSU Animal and Range Science Dept., Fargo and Beef Cattle and Potato Producer, Hensel, ND

Abstract

Acreage dedicated to potato production in North Dakota is increasing. Cull potatoes represent a loss in revenue to potato producers, and a potential feed source for cattlemen whose operations are located near potato producing regions. This project evaluated the efficacy of ensiling cull potatoes with a variety of feedstuffs. Wheat midds, dried beet pulp, whole barley, ground corn, wheat straw and alfalfa hay were evacuated as potential silage ingredients. Various moisture levels were also used in this demonstration project. When potatoes were ensiled at high moisture levels (25% DM), effluent liquid runoff production was high. Silages which were 35% DM appeared to be most acceptable and have lower effluent production. Silages made at higher DM levels became difficult to pack, making oxygen exclusion difficult. All ingredients evaluated appeared to make acceptable silages, provided DM levels were approximately 35%. Cull potato silages may be an alternative feedstuff for beef cattle producers located near potato producing regions.

Potatoes and potato byproducts have been fed for many years. Cattle feeders in the Pacific Northwest (Idaho, Oregon, Washington) routinely use these products in cattle rations (Duncan et al., 1991; Heinemann and Dyer, 1972). North Dakota ranks sixth and Minnesota ranks seventh in the nation in production of potatoes, producing over 10% of the nation's crop. In 1996, the sale of potatoes in Minnesota and North Dakota generated over $215 million in gross income for producers in those two states (Minnesota Agric. Stat. Service, 1998; North Dakota Agric. Stat. Service, 1998). This represents a significant impact on the economy of both states. However, potatoes which are culled following harvest (due to harvest damage, inferior size, or other problems) represent a significant economic loss to the industry (ranging from 19 to 15% of the value of production; North Dakota Agric. Stat. Service, 1997).

Cull potato management can have a significant impact on future potato production. Late blight is a fungal disease in potatoes caused by the fungus Phytophtora infestans (Draper et al., 1994). The cultural practice of making "cull piles" or spreading cull potatoes back onto farm fields intended for potato production contributes to the spread of late blight (Rowe et al., 1995). The late blight fungus requires potato tissue to overwinter (Secor, 1998, personal communication). By spreading cull potatoes back on fields, the late blight fungus is spread to the following crop, and the disease cycle is not broken. Producers with late blight and other fungal diseases are forced to use fungicides as a method to control the disease or face lower production. In some cases, fungicides must be applied every five to seven days during time periods when plants are susceptible to late blight (Anonymous, 1997). This represents a significant cost to the state. Winter feeding costs average almost $150 per cow. This represents approximately 40-45% of the annual cost of maintaining a cow (Hughes, 1997). Reducing the cost of winter feeding for beef cattle operations can increase profitability of beef cattle operations and increase sustainability of these agricultural enterprises.

Whole potatoes have been successfully fed as either sun-dried or freeze-dried potatoes in California and North Dakota (NRC, 1983). Successful freeze drying involves spreading potatoes on fields or pastures during the winter, allowing them to freeze dry, and then letting cattle graze the freeze-dried potatoes. In North Dakota, two practical barriers exist with this method of feeding. Heavy snowfall may prevent cattle from grazing the potatoes. Consequently, the potatoes left on farm fields could contribute to a late blight disease problem the following year if they have been spread on farm fields. In addition, there is still the concern of choking if the potatoes are not completely freeze-dried.

Materials and Methods

During the summer of 1997, cull potatoes from the Don Heuchert farm near Hensel, North Dakota were used to make cull potato silage on a laboratory scale. Cull potatoes were processed through a Haybuster round bale shredder before ensiling. Cull potatoes were mixed with the following feed ingredients to make silages: pelleted beet pulp (25, 35, and 45% DM), pelleted wheat midds (25, 35, and 45% DM), whole barley (25 and 35% DM), ground corn (25 and 35% DM), wheat straw (25% DM), and ground alfalfa hay (25 and 30% DM). Table 1 gives the ingredient formulation for the various silage blends used in the trial.

Each ingredient dry matter combination was replicated three times. Silages were allowed to ferment for 3 weeks before sampling for laboratory analysis. Following the three week fermentation, samples of each of the silages were taken for analysis of DM, ash, CP, in vitro organic matter disappearance (IIVOMD) and pH.


Results and Discussion
Nutrient composition of the various potato silages are presented in Table 2. Raw potatoes are approximately 9% CP on a DM basis. As expected, the addition of graded levels of wheat midds, alfalfa, and barley increased the crude protein content of the silages.

Data from IVOMD analysis indicated that all silages are quite digestible. As one might expect, the addition of lower energy feedstuffs tended to reduce digestibility of the silages.

Visual observation of silages following fermentation revealed that silages formulated to contain 25% DM (75% water) resulted in excess effluent production. This would result in excessive nutrient loss in farm scale silage making. Beet pulp appeared to be more apt to absorb excess moisture, even at low levels of inclusion in potato silages. Silages containing higher levels of beet pulp ($45% DM) were difficult to pack due to the drier nature of the silages. In most cases, visual observation of the silages indicated that approximately 35% DM silages (65% water) resulted in the most acceptable silages. There was also considerable effluent production when whole barley was included in 35% DM silages, likely due to the less fibrous nature of barley compared to beet pulp or wheat midds. Data from other university research (Hugh et al., 1993) also indicates excessive effluent production when potatoes are ensiled alone.

One additional anecdote which we found interesting was that when whole potatoes were ensiled, they lost their turgid nature during fermentation. In fact, following fermentation, whole potatoes could be crushed or mashed easily with you hand. This indicates that it is likely not necessary to chop or crush all potatoes prior to ensiling, but to simply break up potatoes enough so that adequate packing and oxygen exclusion can occur.

Conclusions

Cull potatoes can be readily ensiled with a wide variety of feedstuffs. Our preliminary laboratory scale data, as well as data from other universities, indicates that potatoes must be ensiled at the correct moisture level to prevent excessive effluent production and nutrient loss. Cull potato silages may be an economical way of using and storing cull potatoes for livestock feed. Distance from potato growers or processors will limit use of these products due to their high water content.

Literature Review

Agriculture Canada. 1974. Guidelines for feeding potato processing wastes and culls to cattle. Publication 1527, p. 13.

Anonymous. 1997. An online guide to plant disease control: potato late blight. Oregon State Univ. Dept. of Botany and Plant Pathology.

Burton, W.G. 1989. Uses of the potato other than for human consumption. The Potato. Third Ed. John Wiley & Sons, Inc., New York.

Draper, M.A., G.A. Secor, N.C. Gudmestad, H.A. Lamey, and D. Preston. 1994. Leaf blight diseases of potato. NDSU Ext. Service Bulletin PP-1084., North Dakota State Univ., Fargo, ND.

Duncan, R.W., J.R. Malels, M.L. Nelson, and E.L. Martin. 1991. Corn and barley mixtures in finishing steer diets containing potato process residue. J. Prod. Agric. 44:426.

Heinemann, W.W. and I.A. Dyer. 1972. Nutritive value of potato slurry for steers. Bulletin 757. Washington Agricultural Experiment Station.

Hough, R.L., M.H. Wiedenhoeft, B.A. Barton, and A.C. Thompson, Jr. 1993. The effect of dry matter level on effluent loss and quality parameters of potato based silage. J. Sustain. Agr. 4:53.

Hughes, H. 1997. IRM herd costs and returns in North Dakota. NDSU Ext. Service.

Johnson, R.F., E.F. Rinehart, and C.W. Hickman. 1953. Potato silage for beef steers. Bulletin No. 293, University of Idaho, Agricultural Experiment Station.

Minnesota Agricultural Statistics Service. 1998. Minnesota Agricultural Statistics.

NRC. 1983. Underutilized resources as animal feedstuffs. National Academy Press. Washington, D.C.

North Dakota Agricultural Statistics Service. 1997. North Dakota Agricultural Statistics. Ag Statistics No. 66.

North Dakota Agricultural Statistics Service. 1998. North Dakota Agricultural Statistics. Ag Statistics No. 67.

Partridge, J.E. 1997. Late blight of potato. Univ. of Nebraska-Lincoln Dept. of Plant Path. Bulletin.

Rowe, Randall C., Sally A. Miller, and Richard M. Riedel. 1995. Late blight of potato and tomato. Ohio State Univ. Ext. Fact Sheet. HYG-3102-95.

Sauter, E.A., D.D. Hinman, and J.F. Parkinson. 1985. The lactic acid and volatile fatty acid content and in vitro organic matter digestibility of silages made from potato processing residues and barley straw. J. Anim. Sci. 60:1087.

Secor, G. Potato pathologist, NDSU. 1998. Personal Communication.

 


Table 2: Nutrient Composition of Potato Silages (Dry Matter Basis).

Formulated Silage Dry Matter

Cull Potatoes IVOMD

pH

93.4

4.19

--

--

91.7

4.00

92.4

3.92

Potatoes IVOMPD

pH

93.7

4.08

--

--

89.7

4.04

86.1

3.99

IVOMD

pH

92.8

4.21

--

--

93.7

4.19

--

--

IVOMD

pH

93.0

4.17

--

--

94.8

4.01

--

--

IVOMD

pH

86.8

4.16

--

--

--

--

--

--

IVOMD

pH

89.2

4.27

85.3

4.4

--

--

--

--

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