Case Study: Evaluation of Annual Cultivated Peanut as a Forage Crop for Grazing by Growing Beef Cattle

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1 Case Study: Evaluation of Annual Cultivated Peanut as a Forage Crop for Grazing by Growing Beef Cattle Bob Myer 1 Dan Gorbet Ann Blount Annual peanut forage like other forage legumes has excellent nutritional quality. However, it lacked adequate re-growth during the grazing season when grazed by growing beef cattle. Summary The annual cultivated peanut (Arachic hypogaea L.) was evaluated as a possible high quality pasture forage crop for grazing by growing beef cattle. A 10.2 ac field that was originally planted to annual peanut in 1999 was used. Since 1999, the peanut reseeded (self-seeded) annually. The forage initially was harvested for hay, and the seeds were left in the soil. In 2002, a 2-yr demonstration grazing study was initiated. Early weaned calves were used each year 25 (442 lb avg. wt.) for yr 1 and 20 (402 lb) for yr 2. The peanut field was rotationally grazed each year starting mid July (yr 1) or early August (yr 2). The relatively late start was to ensure the peanut set seed for the next year s forage crop. The grazing season lasted 88 d for yr 1 and 55 d for yr 2. Estimated average forage yield was 5406 lb/ac and 3915 lb/ac for yr 1 and 2, respectively. At the start of each year, forage amount and quality was high; however, both declined as grazing season progressed. Estimated calf gain per ac was 165 and 94 lb for yr 1 and 2, respectively. The annual peanut initially was an excellent forage crop for grazing by early weaned beef calves, but the lack of re-growth and declining forage quality resulted in poor performance late in the grazing periods. Introduction High quality forage legumes that can be grown during the warm season are scarce in the lower southeastern USA. Temperate perennial forage crops such as alfalfa (Medicago sativa) do not grow well in this region (Prine and French, 1999). Perennial (rhizome) peanut for forage (Arachis glabrata) can be grown in this area but is planted from rhizomes and is hard and slow to establish, taking two to three years to establish a stand (Hill, 2002; French and Prine, 2006). The cultivated or annual peanut (A. hypogaea) is well adapted to this region and is established by seed, and unlike the perennial peanut, forage would be available the first year (Gorbet et al., 1994). Recent development of annual peanut cultivars with resistance to late leaf spot may allow the production of a quality, high yielding forage crop without the use of fungicides. Fungicides are commonly used in peanut production to inhibit the development of late leaf, a common foliar disease. Late leaf spot can decrease amount of leaves and thus decrease forage amount and nutritional quality. Also, there is an inherent liability in feeding annual peanut forage to livestock because many of the pesticides, in particular, fungicides, used in peanut production are not cleared for the feeding of forage and crop residue (Gorbet et al., 1994; Hill, 2002). Previous Florida research have obtained forage dry matter yields of up to 7200 lb/ac using disease resistance lines and without the use of fungicides (Gorbet et al., 1994). In that study, Florida Beef Report

2 the forage was harvested for hay 75 to 85 d after planting and then the seed pods were harvested at plant maturity. Defoliation of the canopy, however, resulted in decreased seed pod yields. With changes in the USA peanut program, there has been interest in growing the annual peanut strictly as a forage crop. Since the pods are not harvested, the peanut plant may be able to selfseed (re-seed) and the plants would emerge the next growing season to produce a subsequent forage crop. Thus it would be possible to obtain several years of forage from one planting. Anecdotal evidence suggests that this may be possible as annual peanut will readily emerge (volunteer) the next spring from seed left after harvest the previous fall. A 2-yr demonstration study was conducted to evaluate the suitability of annual peanut as a forage crop for grazing by beef cattle. Procedure The 2-yr demonstration study was conducted at the University of Florida s North Florida Research and Education Center (NFREC) Marianna Beef Unit located in northwest Florida (30.5 N). A 10.2 ac field that was originally planted with annual peanut (cultivar Florida MDR 98 ) in 1999 was used. Each year the peanut plants emerged in April from seed of the previous year s crop. For the first 3 yr, the forage was harvested as hay. In 2002, a beef cattle grazing study was started. The study was conducted for two consecutive years without replanting the annual peanut. The peanut seeding rate in 1999 was 85 lb/ac. Prior to the start of the grazing trial in 2002, lime (dolomite, 1000 lb/ac) was applied to the field in February. Fertilizer was applied (350 lb/ac of minor elements) during March. Also during March, the field was treated with herbicide (Sonalan, Dow AgroServices, Indianapolis, IN, USA) and then disc harrowed. The plants emerged in April. In May, the field was sprayed with another herbicide (Cadre, BASF Corp., Research Triangle, NC, USA). During July, the field was divided into four equal sized sections using temporary electric fencing. A narrow section, 12 ft wide, through the middle of the field was fenced off to provide an un-grazed check area. The four sections were rotationally grazed starting in late July. This rather late starting time was chosen to insure that the peanut plants have pegged (seed set) for re-seeding of the next year s forage crop. For the first year, 25 early weaned heifers and steers with an average initial weight of 442 ± 72 lb were used. While grazing, the calves had free access to water, mineral mix, and shade. Each section was grazed for 7 d then allowed to recover for 21 d and than grazed again. Three complete cycles were completed. After the three rotations, the cattle were allowed to graze all sections for an additional 5 d. Before grazing each section, the forage in two representative one meter (1.2 sq. yd) square areas was hand clipped to a stubble height of about 5 in. Samples were taken to estimate forage dry matter (DM) yield and determine crude protein (CP) and in vitro organic matter digestibility (IVOMD). The samples were dried, ground (1 mm) and saved for future analyses. Also, 7 d before the start in 2002 (yr 1) only, a composite sample was taken from four representative one meter square areas within the entire field. This sample was dried, ground and sent to commercial laboratory for the determination of CP, phosphorus (P), calcium (Ca), ash, acid detergent fiber (ADF), neutral detergent fiber (NDF) and lignin. The individual section samples were dried, ground and analyzed for CP and IVOMD. The above forage management and sampling, and grazing procedures were repeated for the second year (2003) except no lime was applied to the field. Only 20 calves were used (avg. initial weight of 402 ± 62 lb) for the second year. For both years, calf weights were taken after an overnight fast (no feed/pasture and water) at start and end of grazing period, and at an approximate midpoint (d 41 for yr 1 and d 32 for yr 2). For each year, the calves were gradually adjusted to grazing of peanut forage for 5 d prior to weighing and starting of the grazing periods using a small section across the ends of the four grazing sections. For the first year, an initial cattle stocking density of 2.5 head/ac was chosen based on estimated available forage. For the second year, the stocking rate Florida Beef Report

3 was lowered to 2.0 head/ac and time spent grazing each section was also lowered to 4 d. The annual peanut was grown without fungicide and under dry land conditions. Rainfall data during each year s growing-grazing period was obtained from the Florida Automated Weather Network Station at NFREC Marianna. Results Initial analyses of the annual peanut forage (Table 1) indicated very good nutritional value, similar to that of alfalfa (NRC, 2000) and perennial peanut (Prine and French 1999; Hill, 2000). Forage samples taken during the grazing periods also indicated good nutritional value; however, a noticeable decline occurred as the grazing periods progressed, especially the first year (Table 2). The estimated total DM yield of annual peanut forage obtained during yr 1 was within the range of forage yields obtained by Gorbet et al. (1994) for the annual peanut (Table 3). Forage DM yield; however, was lower than commonly obtained (4 to 8 t/ac) for established perennial peanut (Prine and French, 1999). Estimated peanut forage DM yield declined noticeably as each year s grazing period progressed, especially in the first year (Figure 1). The declines indicated a lack of re-growth. Due to the declining peanut forage yield as the grazing period progressed during yr 1, 11 calves were removed after 41 d and the trial continued with just 14 calves. For yr 2, all 20 were kept on for the duration of the grazing period; however, the grazing period lasted only 55 d vs. 88 d for yr 1(Table 3). The grazing season length each year was rather short, especially the in yr 2 (Table 3). In comparison, established perennial peanut can be grazed for 110 to 140 d (June to mid-october) per yr (Blount, A. R., personal communication). Estimated forage DM yield overall was lower in yr 2 and appeared to be negatively affected by grazing in yr 1. Evidence for this negative affect was that estimated DM forage yield obtained in the un-grazed check strip was higher than obtained in grazed areas during yr 2 (4,784 ± 506 vs. 3,915 ± 285 lb/ac). Rainfall, however, was more plentiful for yr 1 (Figure 2) which may have resulted in the difference in forage yield and also for the difference in length of grazing period for each year. Average daily gain (ADG) of the cattle was consistent for the two yr and overall averaged 0.92 lb/d (Table3). However, during yr 1, an ADG of 1.96 ± 0.60lb/d was obtained for the first 41 d. A slightly negative gain was obtained for the last 48 d. The decrease in performance was probably due to the low forage yield and poorer nutritional quality as the grazing period progressed (Table 2; Figure 1). Even though annual peanut was initially an excellent forage source in each yr, its lack of regrowth was quite evident in each year s trial. The strategy of lower initial cattle stocking density and shorter grazing times per rotation used during the second year appeared to be somewhat successful. For the first yr, very few leaves on the peanut plants were noted in a section when the cattle were rotated to the next section even though stubble height was 5 to 10 in. More leaves were evident in yr 2 with the shorter rotations. Even though forage re-growth declined as the grazing period progressed, the decline noted for yr 2 was not as steep as noted for yr 1 (Figure 1). Total calf weight gain per acre averaged 129 lb/yr in this study. Estimated costs for annual peanut for pasture would be higher than value of gain in calf weight. Even though some peanut establishment costs can be spread out over 2 yr or longer, estimated pasture costs still would be about $120 to $140/ac per yr (Hewitt, 2006). Since it appears that grazing may have a negative impact on the following year s forage yield, the probability of profitably would decline with subsequent years. In conclusion, the lack of re-growth limits the annual peanut as a pasture crop for grazing at this time. Progress via plant breeding may produce high yielding, persistent, seeded peanut cultivars that can be used for grazing over several grazing seasons from a single planting. Thus in the future, the annual peanut may be Florida Beef Report

4 viable high quality summer legume forage for grazing in the southeastern USA. Literature Cited French, E.C. and G.M. Prine UF-IFAS EDIS Publ. No. AA183. Gorbet, D.W., et al Peanut Sci. 21: Hewitt, T. D Hill, G.M Vet. Clin. Food Anim. 18: National Research Council (NRC) Nutrient Requirements of Beef Cattle, 7 th Revised Ed. National Academy Press. Washington, DC. Prine, G. M., and E. C. French Perspectives on New Crops and Uses. ASHS Press, Alexandria, VA, USA. pp Acknowledgment The assistance of Mary Chambliss, Harvey Standland, Todd Matthews, Tina Gwin, John Crawford, Wayne Branch, and Richard Fethiere is gratefully acknowledged. Partial funding was from Florida Peanut Check-Off funds. 1 Bob Myer, Professor, Dan Gorbert, Professor Emeritus, and Ann Blount, Associate Professor; UF- IFAS, North Florida Research and Education Center, Marianna, FL Florida Beef Report

5 Table 1. Composition of annual peanut forage a Item Crude protein 17.8 Neutral detergent fiber 32.8 Acid detergent fiber 26.8 Lignin 8.6 Ash 8.2 Calcium 0.85 Phosphorus 0.21 a Average of analyses of samples taken just prior to grazing in yr 1. b Dry matter basis. % b Table 2. Crude protein (CP) and in vitro organic matter digestibility (IVOMD) of annual peanut forage during grazing trials. a Year Sampling period CP,% IVOMD,% 1 First 28 d Second 28 d Last 33 d First 16 d Second 16 d Last 23 d a Average analyses of four samples per period per year; dry matter basis Florida Beef Report

6 Table 3. Animal grazing days, forage dry matter (DM) yield, and performance of growing cattle grazing annual peanut forage. a Year 1 Year 2 Grazing period: Start 12 Jul 5 Aug End 8 Oct 29 Sep Days Grazing d/ac Forage DM, lb/ac 5406 ± 148 b 3915 ± 285 b Stocking density, head/ac Avg. daily gain, lb 0.99 ± 0.42 c 0.86 ± 0.29 d Gain, lb/ac a Yr 1, 25 head for first 41 d of grazing and 14 head for last 48 d of grazing. Yr 2, 20 head for entire grazing period. b N = 4. c N = 19 (weighed average). d N = Year 1 Year First Second Last Figure 1. Estimated annual peanut forage yield, lb dry matter/ac (First = first 28 d period of grazing for yr 1 and first 16 d for yr 2; Second = second 28 d for yr 1 and second 16 d for yr 2; and Last = last 33 d for yr 1 and last 23 d for yr 2; S.D. = 102, 112 and 46, and 73, 57 and 72 lb DM/ac for each of the three periods for each yr, respectively) Florida Beef Report