Feeding Value of Field Pea and Hull-less Oat in Growing Calf Diets (continued)

Keywords

Introduction

Materials and
Methods

Results

Discussion

Conclusions/
Implications

References

Project
Background

Introduction
Alternative crops are playing a greater role in North Dakota field crop production. Annual legumes complement crop rotations by expanding the number of crops available to small-grain producers who want to avoid problems associated with continuous small-grain cropping (Peel, 1998). Field pea (Pisum sativum), an annual legume, can be grown in small-grain rotations in North Dakota (Peel, 1998). Since pea was first cultivated 8,000 years ago, it has indirectly been valued for its nutrient composition as a food for humans (Hickling, 1994).

Common oat (Avena sativa) threshes with the hull intact and is lower in energy and less dense than other feed grains (Ensminger and Olentine, 1978). Oat groat (oat grain minus the hull) is comparable to corn in feeding value (NRC, 1984), but is usually expensive. Oat hull is less palatable and lower in nutritive value than oat groat (Ensminger and Olentine, 1978). Because of these characteristics, conventional oat, oat hull and oat groat are not widely used in the feeding of feedlot cattle ( Johnson and Boyles, 1991). Hull-less varieties of oat are accessible (Peel, 1997), but grain availability has been limited. Because of a reduced hull concentration, hull-less oat may have a feeding value similar to oat groat (e.g. higher digestibility, higher protein, lower fiber). Several hull-less oat varieties are being developed in the U.S. and Canada. 'Paul' oat is a hull-less oat variety that was recently developed in North Dakota (McMullen et al., 1997)

Pea and hull-less varieties of oat have not been widely fed to livestock in North Dakota. As the acreage for these crops expands, producers are looking for alternative markets for their grain. Chemical composition of these two types of grain suggests that both crops have potential for use as livestock feed (Table 1). Preliminary observations suggest that in North Dakota pea is palatable and readily consumed by cattle (V. Anderson, personal communication) and in South Dakota, when pea is used as a protein supplement, there is a tendency for feed efficiency to be improved in finishing cattle (C. Birkelo, personal communication). Hull-less oat also improves feed efficiency when used in growing and/or finishing cattle diets (Johnson et al., 1995; Anderson et al., 1997; Schimek et al., 1997). Little research has evaluated the feeding value of either pea or hull-less oat in growing beef cattle diets. Establishing feeding values is essential if these grains are to be used in least-cost ration formulations.

Cattle feeding studies were designed to evaluate the potential of 'Trapper' pea and 'Paul' oat for use as feedstuffs for weaned calves. Studies involved substituting a portion of the barley (Hordeum vulgare) and soybean (Glycine max) oil meal (SBM) in a control diet with test feeds (pea and hull-less oat). In addition to documenting animal performance and feed efficiencies, treatments were designed to establish relative net energy values for test feeds. This is vital information for the future use of the these feed grains in diet formulations for cattle.

Materials and Methods
Two experiments were conducted to meet the following objectives:

1. Determine the effect of including pea or hull-less oat in backgrounding diets for weaned calves on animal performance and feed efficiency.

2. Establish relative net energy concentrations for pea and hull-less oat.

Experiments were conducted at the Manning Ranch facility of the Dickinson Research Extension Center. Twelve feedlot pens (3072 ft², with 16 ft of fence-line bunk space, per pen) were used in each experiment. Each pen was equipped with a slatted-board windbreak in the northwest corner and water was provided free-choice by automatic, frost-free waterers.

The first experiment (Exp 1; fall 1995) was designed to evaluate the effect of feeding pea ('Trapper') or hull-less oat ('Paul') on the performance of early weaned calves. Forty-eight crossbred calves were blocked by sex (steer or heifer) and weight (heavy or light) and randomly allotted within group into 12 pens (three pens per blocking combination). Pens within group were assigned to one of three dietary treatments. Diets were formulated to meet or exceed the nutritional requirements of a medium frame steer calf gaining 2.6 lb of liveweight per day (NRC, 1984; Bandyk et al., 1994). Treatments included a control diet (CONT1; approximately 70% concentrate and 25% ground oat hay in a total mixed ration) and two diets where a portion of barley and SBM in the concentrate of the control diet was replaced by one of two test grains (Table 2). The test grains included pea (FPEA1) and hull-less oat (HOAT1). The fat from hull-less oat in the second test diet was formulated not to exceed 5% of diet dry matter. All feed grains were processed in a roller mill prior to mixing diets. Calves were started on an all forage diet and the grain portion of the diet gradually increased until the desired level of grain was achieved. All diets included lasalocid (Bovatec^®) as an ionophore (40.8 g/ton of diet dry matter). Calves were fed test diets ad libitum for 63 days. Animals were weighed on two consecutive days at the beginning and end of the test feeding period to calculate average body weights (BW) and average daily gain (ADG).

Feed ingredients were sampled for nutrient analysis at the beginning of the experiment. Chemical analysis of feed grains included dry matter (131°F), crude protein (AOAC, 1990), ADF (AOAC, 1990) and NDF (Robertson and Van Soest, 1982). Forages were analyzed for the same nutrients using near infrared spectroscopy (NIRS; Iowa Testing Laboratories, Inc., Eagle Grove, IA). Composition of salt (NRC, 1984) and supplement (Feedlot No. 411B, Vigortone Ag Products, Inc., Cedar Rapids, IA.) were assumed to be as reported. Feed ingredient usage per diet and individual pen deliveries were recorded daily. Dietary chemical composition (Table 2) was computed as a weighted average of the product of ingredient composition and average feed ingredient usage. Feed bunks were cleaned and feed refusals weighed and subsampled at the end of each week. Weekly feed refusals were dried (131°F) and dry matter intake (DMI) calculated as the difference between dry matter delivered and refused.

The second experiment (Exp 2; winter 1996) was designed to evaluate dietary treatments similar to those in Exp 1 in older, later weaned calves. The basic design and protocol were similar to those used in Exp 1. Crossbred heifer calves (n=72) were blocked by weight and randomly allotted within group into one of 12 pens. Pens within group were assigned to one of four dietary treatments. A higher forage diet (39% corn silage, 25% ground oat hay and 33% concentrate on a dry matter basis) was fed as a total mixed ration. Diets were formulated to meet or exceed the nutritional requirements of a medium frame hiefer gaining approximately 2.3 lb of liveweight per day (NRC, 1984; Banduk et al., 1994). Dietary treatments (Table 3) were similar to those used in Exp. 1 (control, CONT2; pea, FPEA2; hull-less oat, HOAT2), with the addition of one test diet that contained both pea and hull-less oat (COMB2). All diets included lasalocid (Bovatec^®) as an ionophore (27.8 g/ton of diet dry matter). Calves were fed the test diests ad libitum for 63 days.

Average BW and ADG were used to estimate net energy retention of calves over a test period. Energy retention (calculated from shrunk BW and ADG; NRC 1984) and actual dry matter intake were used to calculate the net energy (NE) concentration of each diet (Zinn, 1987). Net energy concentration (NRC, 1984) of dry rolled barley and SBM was assumed and the energy concentration of test grains expressed relative to barley and SBM. The combined pea/hull-less oat diet was used to test the relative energy concentration calculations.

Data from both experiments were analyzed as randomized complete block designs using general linear modeling (PROC GLM) procedures (Freund et al., 1986). Significant (P less than or equal to.1) effects were evaluated using a Bonferroni t-test. The overall experimentwise error rate was set at .10. The Pdiff option of SAS was used to make individual t comparisons. In Exp 1, no interactions (P>.1) were observed between sex and dietary treatment.

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Table of Contents – Summer 1998