Text Box: Introduction

North Dakota leads the United States in field pea production, giving producers in the state a high quality, palatable protein and energy source for beef cattle. This study was conducted to compare the common processing methods for field peas (grinding, rolling, or feed whole) in finishing feedlot diets. Field peas are marketed as dry, shelled products primarily for human consumption. Surplus grain, off quality grains, and screenings which contain high levels of protein (approximately 24% CP) and energy (approximately 48% starch), are an attractive, nutrient dense livestock feed. Field peas can be successfully included in corn- or barley-based rations as a protein supplement; however little information is available on the optimum level of processing needed to maximize cattle performance. Thus, our objective was to determine whether dry-rolling, grinding, or feeding peas whole was the optimum level of field pea processing in growing and finishing diets of feedlot heifers. Whole grains are less digestible than processed grain; however, dry rolling has a tendency to split the peas into a hull or endosperm fraction, which does not mix well and adds variation to the diet. Three levels of pea processing in both a growing and finishing diet were investigated in this trial: whole, dry-rolled, and ground.

 

Procedure

One hundred twenty-seven crossbred heifers (avg. wt. 799.9 11.4 lbs.) were allotted by weight to one of three pea-supplemented diets (4 pens per treatment, 10 or 11 head per pen) to determine the optimum level of pea processing to maximize cattle performance. The corn-based diets contained ground, dry-rolled or whole peas as a protein source. Diets were formulated to contain 13.5% CP with 56.5 Mcal/cwt NEg in the finishing diet. Diets were corn-based and contained whole, dry-rolled, or ground peas as a protein source. During the first 28-day period, the diet contained 22% grass-hay, after which cattle were transitioned to a 15% grass-hay diet, fed until slaughter. The 22 and 15% grass-hay diets were formulated to contain 13.5% CP and 52.5 and 56.5 Mcal/cwt NEg, respectively. Cattle were slaughtered at Tyson Foods (Dakota City, NE) when fat thickness for the entire group was estimated to be 0.40 in. Hot carcass weight, fat thickness, percentage kidney, pelvic and heart fat, ribeye muscle area, and USDA quality and yield grades were determined by qualified personnel 48 hours after slaughter.

 

Results

Particle size of ground, rolled, and whole peas was 701, 3100, and 9250 microns, respectively. Dry matter intake was greatest (P<.05) for the rolled-pea treatment (22.81 lbs. per hd/day) for the entire feeding period compared to ground (21.21 lbs.) and whole (21.33 lbs.). Intake exhibited a quadratic response (P<.05) to processing treatment during each of the feeding periods with reduced intake for the ground- and whole-pea treatments. Average daily gains were greatest (P<.01) for the rolled- pea treatment for the entire feeding period (3.39 lbs./hd/day) compared to ground (3.12 lbs.) and whole (2.96 lbs.). Statistical differences in gain were greater during period 1 (P<.01) and period 2 (P<.06) than period 3 (P<.15). Feed efficiency expressed as feed per gain or gain per feed was not different during any of the feeding periods or overall (P>.16). Carcass data followed the pattern of rate of gain and final weight with predictable numerical differences observed. Hot carcass weight (P<.13) and yield grade (P<.10) showed the greatest response to treatment with higher values for the rolled-pea treatment.

 

Discussion

Heifers consumed more (P<.05) of the dry-rolled pea diet and gained faster (P<.01) than rations with ground or whole peas. No differences in feed efficiency or carcass traits were observed (P>.10). Field peas can be successfully included in feedlot rations with the greatest intake and gain from dry-rolled peas.