Effects of Bedding on Winter Performance of Feedlot Cattle and Nutrient Conservation in Composted Manure
Vern Anderson, Ezra Aberle, and Lowell. Swenson
NDSU Carrington Research Extension Center
The states and provinces in the Northern Plains are known as a cow-calf producing region with spring calving and fall weaning commonly practiced. Winter feeding of weaned calves is becoming more common due to increasing amounts and diversity of feeds. However, mitigating winter weather stress is required for good animal husbandry and profitable enterprises. This study was conducted during the winters of 2001-2 and 2002-3 to evaluate steer performance, economic returns, and nutrient retention in manure. Steer calves born and raised at the Carrington Research Extension Center (n=107) were randomly allotted to three bedding treatments for two consecutive years and fed a high concentrate diet (62 MCal/lb NEg) from November until ready for market in the spring. The bedding treatments were: no bedding, modest bedding, and generous bedding. Feed intake was not affected by bedding treatment (P<.05). However, weight gain responded positively (P<.05) to bedding in two of the four 28 day winter feeding periods. Steers without bedding gained 2.82 pounds per day, modestly bedded steers gained 3.68 pounds, and generously bedded steers gained 3.53 pounds per day. Feed efficiency tended to improve overall for bedded steers (P=.09). Carcass quality traits were positively affected by bedding (P<.05). Marbling score, the indicator for USDA carcass quality grade, improved with bedding as did the percent of carcasses grading choice. Twenty three percent of carcasses from non-bedded steers graded USDA Choice vs. 45 percent for modest and 63 percent for generously bedded steers. Economic return increased for bedded steers with a gross return of $756.92, $818.68, and $838.53, respectively, for no bedding, modest bedding, and generous bedding treatments. With increasing amounts of bedding, nutrient losses were reduced in composted manure. Nitrogen losses were reduced from 65 percent for no bedding to 32 percent for modest bedding and 19 percent for generously bedded steers. Phosphorous (P205) and potassium (K20) losses were also reduced with increased bedding. More work is underway to explore other bedding materials and management methods for limiting nutrient losses.
Feeding cattle in the winter in North Dakota poses some environmental challenges with wind, snow, and cold. Wind fence and shelterbelt protection have been proven to be effective in enhancing performance of feedlot cattle in North Dakota (Anderson and Bird, 1993). In most commercial Canadian feedlots, wind fences and bedding are commonly provided for mitigating winter stress. Many ND farmer-feeders use straw for their calves and spread the manure/straw mix back on cropland as part of their fertility program. However, bedding feedlot cattle is not consistently practiced in commercial finishing yards in the Dakotas.
Ammonia volatilization and nitrate runoff from animal manure are considered a major potential pollution sources in the environment. Bedding may improve the carbon –nitrogen ratio of the manure/straw mixture to facilitate effective composting and greater nitrogen retention. This study evaluated use of wheat straw for bedding feedlot steers during the winter in North Dakota and determined effects of straw on nutrients in raw and composted manure.
Steer calves born and raised at the Carrington Research Extension Center were weaned, preconditioned, and randomly allotted to three bedding treatments in late fall of 2001 (n=53) and 2002 (n=54). The bedding treatments were: No bedding, modest bedding, and generous bedding. All pens were identical in size, orientation, and water source each year with approximately 150 square feet of pen space provided per head in year one and 250 square feet in year two of the study. Steers in the three treatments were fed the same finishing diet (84% concentrate, 62 Mcal NEg, corn based diet) to appetite. Feed bunks were read daily at 8 AM and the ration adjusted according to intake with feed delivered between 8:30 and 10 AM. All calves were weighed every 28 days to compare performance during segments of the winter and spring. Steer calves were fed to finish weight (estimated 60% choice in the bedded treatments) and marketed at the same time (days on feed) with carcass data collected at slaughter. Economics were calculated based on feed intake, gain, feed efficiency, carcass value, and bedding costs.
Modest bedding was a minimalist approach with limited amounts of straw provided so calves did not have to lay on snow or frozen manure. Generous bedding was double the amount of straw in the modest bedding treatment. Straw was added approximately every week with longer periods between bedding when weather allowed. Big round bales were deposited in the pens and spread throughout the bedding area with a front end loader equipped with a grapple fork. Calves could move from the bedded area to feedbunks and water fountains on concrete aprons. Data reported represents the last four months prior to market, roughly equivalent to December through March each year.
During the trial, calves were observed to have variable amounts tag or manure attached to their hide associated with bedding treatment. A five point scoring system was developed to quantify the amount of tag on the hide and all steers were scored prior to going to market. Three people independently scored each steer. The scoring system was 1=no tag, clean hide, 2=small lumps attached to the hide in limited areas of the legs and underbelly, 3=small and large lumps attached to the hide covering larger areas of the legs, side and underbelly, 4=small and large lumps of manure attached to the hide in areas along the hind quarter, stomach, and front shoulder, and 5=lumps of manure attached to the hide continuously on the underbelly and side of the animal from brisket to rear quarter.
Manure was weighed out of pens shortly after the cattle were removed in the spring. Each pen was sampled at eight different spots using a core of manure taken with a tiling spade. The samples were pooled for each pen and analyzed at the NDSU Soils Laboratory for fertility value (organic matter, N, P, and K) on a dry weight basis. Samples were also taken after the composting process with dry matter and nutrients determined.
Data were analyzed using SAS GLM procedures with pen as the experimental unit. Normal replicated studies allot six to eight steers per pen but limited pen availability and evaluation of the practicality of bedding suggests larger numbers of animals per pen would be more realistic. Granted, more replicates would increase the confidence of the results. Years (2) were used as replicates as variation in winter conditions may affect need for bedding.
Dry matter intake (Table 1) was not affected by bedding treatment (P<.05). It was observed that daily intake by non-bedded steers fluctuated more than bedded treatments but differences balanced out over weigh periods and multiple years (replicates) of the study. Gains responded significantly (P<.05) to bedding in two of the four periods, when weather was severe and during spring thaw, and overall. Generously bedded steers gained 3.53 pounds per day, modestly bedded steers gained 3.69, and steers without bedding gained 2.83. Gain per feed improved significantly (P=.06) in one period and tended to improve overall for bedded steers (P=.09). In the second year of this study, the no-bedding treatment was compromised for the last weigh period due to severe stress to the animals. Modest bedding was provided for one month in attempt to provide a dry environment for steers and avoid serious health challenges and marketing discounts. Feed intake and gains dramatically improved for that one month and are included in the data set.
The least amount of tag was attached to the generously bedding animals (1.58 tag score), more tag on the modestly bedded animals (2.64 tag score), and much more (3.75 tag score) associated with no bedding. The excessive tag on the non-bedding calves reduced insulation value of dry hair on a clean hide. Calves in this group were observed to be stiff and slow to get up. Individual steer weights used for calculating average daily gains included manure tags attached to the hide which may have inflated actual body weight gain.
Clean steers in bedded pens gained faster. No-bedding steers carry significant manure tag.)
Most carcass quality traits (Table 2) were positively affected by bedding (P<.05). Final weight was greater for both bedded treatments, at 1182 pounds for generous bedding and 1172 pounds for modest bedding, vs.1121 pounds for steers with no bedding. Carcass weight and dressing percent improved with bedding, with manure tags on the non-bedded calves potentially affecting dressing percent. Marbling scores, the indicator for carcass quality grade, improved with bedding as did the percent of carcasses grading Choice. Twenty three percent of carcasses from steers without bedding graded choice, vs. 45 percent for modest and 63 percent for generously bedded steers. Rib eye area tended to increase (P=.06) with bedding from 11.47 square inches to 12.09, and 11.99 respectively for modest and generous bedding treatments. Yield grade, fat thickness over the 12th rib, and internal fat (kidney, pelvic, heart fat, KPH) were not affected by bedding.
The amount of bedding varied somewhat with year but overall averaged 385 pounds per head for modest bedding and 674 pounds per head for generous bedding. Size of pens, number of animals, method of bedding (shredder, whole bales etc), bedding material (straw, stover, soybean residue), precipitation, southern exposure, temperature and other factors may affect amount of bedding required. Economies of scale suggest larger numbers of animals in a pen may require less bedding per animal but this would reduce the carbon addition to manure. At $30 per ton for straw, modestly bedded steers were charged $5.77 per head and generously bedded steers $10.15 per head for bedding.
Economic returns greatly favor the bedded treatments. If steers are sold on a grid using $1.20 for Choice cattle and $1.10 for Select cattle, the advantage for bedding based on data in this study increases to $61.76 for modest bedding and $81.61 for generous bedding. A larger price spread between Select and Choice would increase the return from bedding. Steers with no bedding may have graded better if they had been fed longer, however, the additional feed, yardage, and other costs would at least partially offset anticipated improvement in carcass value.
In a commercial operation, the cost of distributing bedding, removing manure from pens and composting practices needs to be considered with labor and equipment operation as the major expenses. On the credit side, the extra fertilizer value of raw and/or composted manure must also be included.
Nutrients in raw and composted manure are reported on a dry basis in pounds per head in Table 3 and Figures 1 -5. Dry matter percentage was lower for bedded treatments as a result of the increased absorbency of the straw in both raw (48.3% for no bedding, 23.9% modest bedding and, 29.7 for generous bedding) and composted (51.2% for no bedding, 38.77% for modest bedding and, 42.4% for generous bedding) manure. The proportion of organic matter recovered from raw to composted manure appears to favor the two straw treatments. Organic matter recovery was 12 percent for no bedding to 45 and 33 percent respectively for modest and generous bedding. Nitrogen losses to volatilization and runoff decreased with bedding treatments. Recovery of N is calculated at 35, 68, and 81 percent respectively for no bedding, modest bedding, and generous bedding. Phosphorous (P205) recovery was observed at 68, 111, and 130 percent of the original amount. No specific explanation is given for recovering more P than originally present and bedding contained very small amounts of phosphorous. Potassium was recovered at 31, 37, and 86 percent for the respective treatments. While modest bedding provided evidence of sequestering other nutrients, the higher level of bedding appears to improve proportion of potassium captured in the composted manure. The most significant point of this data is the increasing capture or sequestration of nitrogen, which will increase the value of manure as fertilizer while reducing potential pollution by ammonia and runoff.
The magnitude of improvement in steer performance and net return for bedding is much greater in this study than other researchers have reported, probably due to the more severe weather stress encountered in North Dakota. In a southern South Dakota study, Birkelo and Lounsbery (1992) observed a positive effect on gain, feed efficiency, and return when using 266 pounds of bedding per head in open lots. A Colorado study (Stanton and Schutz, 1996) also concluded that bedding improves gain and dressing percentage in finishing steers but had no impact on
feed intake and returned an extra $8.00 per head above costs. While bedding is important for the comfort of the animals and profitability for northern feeders, it is a factor in reducing ammonia volatilization from animal manure. Reducing losses of 65 percent of nitrogen (35% recovered) in raw manure from the no bedding treatment to less than 20 percent with generous bedding identifies a method producers can use to increase the fertility value of the manure as well as protect the environment.
North Dakota feeders can be very competitive with other states in the cattle feeding industry. Low feed costs, quality of cattle, and availability of bedding are key factors. Bedding feedlot cattle during the winter contributed to a profitable feeding enterprise and limited environmental pollution from ammonia while capturing more nutrients to be used as fertilizer.
Birkelo, C.P. and J. Lounsbery. 1992. Effect of straw and newspaper bedding on cold season feedlot performance in two housing systems. South Dakota Beef Report p42-45.