H.H. Van Horn

Dietary Protein Effects on Nitrogen Excretion and Manure Characteristics of Lactating Cows

In the primary experiment, 12 diets were fed to 34 lactating cows with the objective to determine effects of level and source of dietary protein on N excretion, the first estimate needed to budget manure N flow and utilization on dairy farms. Complete collection of urine and feces separately allowed for determination of digestibilities and urine and fecal excretion of N. Equations to predict N excretion in urine and feces were developed using DM intake and N intake as the primary predictors. Including milk yield or body weight in the model did not account for appreciable additional variation. Fecal plus urine N excretions estimated from these equations agreed closely with NRC equations and estimates made assuming that N consumed was either secreted in milk or excreted in urine and feces (diet N minus milk N). Predicted N excretion for 635 kg Holstein cows consuming 17.8 kg/d dry matter (15.3% CP), which is the estimated amount required for 22.7 kg milk/d, was 325 g (150 g urine N and 175 g feces N). Fecal DM excretion averaged 34.3% of DM intake (6.1 kg for typical cow) and was 88.2% volatile solids; daily urine dry matter averaged 0.9 kg/d (20 kg urine/d averaging 0.045% dry matter) and was 47.8% volatile solids. Additionally, compositions and total daily excretions were determined for feces (ADF, NDF, crude fat, Ca, P, Mg, K, Na, Fe, Zn, Cu, Mn, and Mo) and urine (Ca, K, Mg, Na, P). As with N, amounts of various fractions excreted daily were closely associated with DM intake (which varies with milk production) and were much less variable than percentage compositions. Abbreviation key: BM = blood meal, Ca-LCFA = Ca soaps of long-chain fatty acids, CP = crude protein = N ¥ 6.25, DM = dry matter, DMI = DM intake, FtM = feather meal, RUP = ruminally undegraded protein, SBM = soybean meal.

Nutritional Implications for Manure Nutrient Management Planning

Nutrient management planning is necessary for many livestock producers. In order for producers to accurately plan on-farm nutrient generation and utilization, reasonable estimates of manure production and composition must be available. Amounts of manure nutrients (e.g., N, P, and K) originally excreted are predicted more accurately with a nutritionally based input-output model than are the amounts recovered because the amounts that are recovered vary depending on climate, storage and handling practices, and other site-specific influences. Records of amounts of manure collected and composition determined from manure sampling are essential to determine the total of manure nutrients that must be managed in the plan. It is important to compare recovered amounts with manure production estimates to determine if losses are reasonable and acceptable. Using nutritional inputs in the prediction of manure nutrient outputs permits nutrient management planners to interact with producers to assess the environmental cost of overfeeding critical nutrients. Manure nutrients (e.g., N, P, and K) equal the amounts in feed consumed minus the amounts in products produced (e.g., milk, eggs, meat, or offspring) whereas, the amount of manure dry matter is an inverse function of the ration digestibility. The indigestible dry matter is the expected amount of fecal dry matter; additional dry matter in urine is small. The percentage compositions of nutrients in manure recovered (accounting for nutrient losses as well as uncollected portions) are much more difficult to predict than total amounts that should be collected because anaerobic digestion of carbon-containing compounds that was initiated in the large intestines of animals continues after excretion or the fermentation shifts to aerobic. Volume reduction occurs as carbon dioxide and methane are emitted and non-volatile nutrients such as P and K are concentrated in the remaining dry matter. From 40% to 75% of excreted N is in the urine as urea or uric acid (birds) and can be quickly volatilized as ammonia. Some losses of N to the atmosphere are unavoidable, at least 35% of excreted N in best case scenarios and 60%, or more, in most situations. Losses of non-volatiles such as P and K are small. Due to these changes, manure becomes increasingly P-rich relative to plant fertilization needs with N:P ratios usually below 3:1; whereas, ratios based on plant needs are much wider. Thus, acreages of crop production needed to recycle manure P are much greater than acreages needed for manure N. In the future, priority will be on reducing excretion of P and on retaining a higher percentage of excreted N. Dietary measures to impact P excretion will be increasingly important. To achieve environmentally acceptable nutrient balances, many animal production facilities will have to export manure or manure products or manipulate nutrient production to match nutrient needs. The role of diet will become increasingly important as producers establish whole-farm nutrient balance plans.

Production and characteristics of manure from lactating dairy cows in Florida

Total quantities of urine and feces excreted daily were collected from 12 lactating Holstein dairy cows averaging 567 kg (1250 lb) on fixed feed intake averaging 20 kg (44 lb) of dry matter per day, or 16 kg (36 lb) of dry matter per day per 454 kg (1000 lb) of body weight. Amounts of total and volatile solids, acid detergent lignin, phosphorus in feces, and phosphorus in urine were determined. Cows excreted an average of 44.6 kg (98.1 lb) of raw waste, 6.08 kg (13.1 lb) of total solids in feces, and 0.16 kg (0.3 lb) of fixed solids in feces daily, expressed per 454 kg (1000 lb) of body weight. Total solids of feces represented 36.4% of the daily diet dry matter intake. These values are greater than table values developed by previous researchers and used to design dairy farm facilities. Feces to urine ratio (w/w) ranged from 1.4:1 to 1.9:1. Fecal grab samples (n = 383) from cows on commercial dairies, for which estimated daily intake of feed was available, had greater acid detergent lignin content (16.9 vs. 13.8%) and about 60% more than cows on the total collection trial (4.2 vs. 2.6%), perhaps due to some ingestion of sand on pasture. For all fecal samples fixed solids percentages were much less than table values developed by previous researchers. Differences may be due, in part, to improved genetic potential of cows, because of increased feed intake, climate, or intensive management practices. Our research also confirmed that the quantity of phosphorus (P) excreted in feces was variable, but depended on intake of dietary P.

EFFECTS OF HYDRAULIC RETENTION TIME ON PERFORMANCE AND EFFLUENT ODOR OF CONVENTIONAL AND FIXED-FILM ANAEROBIC DIGESTERS FED DAIRY MANURE WASTEWATERS

Anaerobic digestion greatly reduced malodor of dairy manure flushwaters as judged by a human panel. Effects of solids content and hydraulic retention time (HRT) on digester performance and odor were tested in laboratoryscale conventional stirred tank reactors (CSTR) operated at 20, 15, 10, and 6 day (d) HRT or fixed-film digesters at 1.5- and 2.3 d HRT. Feedstocks were 2.0% total solids (TS) diluted dairy manure and 1.3% TS screened dairy manure. Methane yields (L/g volatile solids, fed) and reduction of solids, chemical oxygen demand, and odor were greatest in CSTR operated at 20 d HRT fed either feedstock; most changes from feedstock were linearly associated with HRT. Organic matter reduction, methane yields, and odor in fixed-film digesters operated at 1.5 and 2.3 d average retention times were similar to that in 10 d CSTR.

Separation of Manure Solids from Simulated Flushed Manures by Screening or Sedimentation

Feces and urine were collected separately from individual cows fed corn silage-based (50% of dry matter) diets which were supplemented with distillers dried grains plus solubles or soybean meal to be 14 or 18% crude protein (CP). Fecal samples from 30 cows were screened using wet sieving and vibrating screens (nested in series); sizes were 3.35, 2.00, 1.40, 1.00, and 0.50 mm. Effluent passing the screens contained 60.2% of total solids (TS), 86.3% of nitrogen (N), and 94.3% of phosphorus (P). Solids caught on the five screens (largest to smallest) accounted for the following percentages of materials: 14.6, 9.4, 2.8, 4.3, 8.6% of TS; 5.7, 3.1, 0.8, 1.3, 2.8% of N; 2.2, 1.2, 0.3, 0.6, 1.5% of P. In another study, a 100 g composite sample of urine and feces from each of 44 cows, mixed in proportion to the amount excreted, was diluted to 1 L with water and allowed to settle for 1 h in a graduated cylinder. Supernatant and sediment were separated by decanting. Supernatants were analyzed for N content, sediments for TS content, and these amounts were subtracted from analyzed contents of samples to obtain reciprocal fractions. Overall, the sediment contained 66% of TS and 45% of N. Estimates of sediment amount made at 5, 10, 20, 40, and 60 min by recording best-defined line between supernatant and sediment suggested sedimentation was 89% completed by 5 min. In a second sedimentation study, simulated manure flushwaters (0.5, 1.0, and 1.5% TS) were treated with additives as follows: (1) 0.75 g of CaC03 plus 0.50 mL Fe2(SO4)3 solution/L, (2) 0.75 g of Ca0 plus 0.50 mL Fe2(SO4)3 solution/L, (3) 0.50 mL Fe2(SO4)3 solution/L plus five drops of a commercial polymer, and (4) control (no additives). Precipitates with CaCO3 and CaO treatments contained 92% of the TS, 69% of the N, and 31% of the total potassium (K); the CaO treatment precipitated appreciably more P (93% of total) than other treatments; and treatment with Fe2(SO4)3 plus polymer precipitated the least TS and N. These data indicated a potential to remove more manure solids and N from flushed manure by sedimentation than by screening.

Use of Flocculants in Dairy Wastewaters to Remove Phosphorus

Additions of alum (Al 2 (SO 4 ) 3 ), ferric chloride, and polyacrylamide solutions were tested in the laboratory for their effectiveness to increase nutrient removals, especially phosphorus (P), by sedimentation from flushwaters with 1% dairy manure solids. Alum and ferric chloride significantly affected TS recovered, pH, and amounts of P, TKN, K, Ca, Zn, Cu, Mn, and Na remaining in the effluent as compared with control sedimentations without additives. Effects on P removals were greatest with removal curves best fitting a quadratic polynomial (r 2 = 0.96 for P). However, the linear regression coefficients for P with a linear only model (r 2 = 0.93) were considered to be good estimates of average removal rates (4.0 mg P removed/mmol Al +3 for alum, 5.36 mg P removed/mmol Fe +3 for ferric chloride). Polyacrylamide treatments were not different from control sedimentations at the concentrations tested. Field studies tested 0, 0.9, and 1.8 mL/L additions of alum solution (4.4% Al by weight) to dairy manure flushwaters (0.33% TS and 41 mg P/L) that previously had been subjected to sedimentation and screening. Management scenarios tested, utilizing 4100 L tanks, were single-fill (batch), 3-fill continuous flow, and 6-fill continuous flow. Removals of 11 to 17 mg P/mmol Al +3 added (0.9 mL alum/L) were higher than in the laboratory experiment. All removal efficiencies in laboratory and field experiments with either alum or ferric chloride were well below theoretical efficiency of one millimole of P (31 mg) precipitated as phosphate with one millimole of Al +3 or Fe +3 but lower efficiencies are expected when organic compounds are present that can bind these ions. These studies demonstrated that reduction of P in dairy manure wastewaters to low levels is possible with additions of alum or ferric chloride solutions. However, the economics of these procedures did not appear favorable.

EFFECTS OF FE AND CAADDITIONS TO DAIRY WASTEWATERS ON SOLIDS AND NUTRIENT REMOVAL BY SEDIMENTATION

Simulated flushwaters containing 0.5, 1.0, or 1.5% dairy manure solids were utilized in four laboratory experiments to test effect of chemical additives on sedimentation of total solids, N, P, K, and other mineral nutrients. Sedimentation for 20 min without additives removed approximately 64% of total solids, 20% of N, 60% of P, and 40% of K. Additives tested were Fe2(SO4)3, Fe3Cl, FeSO4, CaO, hydrated lime (Ca and Mg hydroxides and oxides), CaCO3, and CaSO4. Ferric salts were much more effective than Fe+2 and Ca salts; Fe+3 was more effective with chloride than sulfate. Adding 278 mg/L Fe (the highest level tested) from FeCl3 effected sedimentation of 89% of solids, 56% of N, 88% of P and 60% of K; an additional 358 mg Ca/L from CaO (the most effective Ca source) sedimented 4.0% more solids and 3.9% more P but had no beneficial effect on N or K. Reuse of effluent water to simulate recycling of flushwater showed little potential to reduce flocculent salt levels. Field trials determined that an Ag Pro® Manure Extractor with screen size of 1.5 mm removed approximately 30% of volatile solids by screening and flow-through sediment basins subsequently removed an additional 23%. Although, the estimated cost of flocculants versus the value of fertilizer nutrients sedimented were not favorable, potential was demonstrated for food animal producing units that flush to use flocculants to concentrate nutrients in sediment that could be exported off-farm, if necessary to meet environmental regulations. Further work is indicated to ensure workability of an economical system under farm conditions

Achieving Environmental Balance of Nutrient Flow Through Animal Production Systems1

Abstract An animal nutrition-based model to predict nutrient excretion to be managed on food animal production units is recommended. In a dairy model, average yearly excretions per high-producing cow of common fertilizer nutrients were estimated at approximately 250 lbs N, 461bs P, 100 lbs K, and 80 lbs Ca. Multiple cropping systems have the potential to consume about 400 lbs N/acre and 50 lbs P/acre. Applicable data of this nature for specific farms are essential for development of nutrient accountability budgets. Separating fibrous solids from flushed manure facilitates irrigation of the effluent in many manure management systems but removes relatively few nutrients which are of environmental concern (e.g., N and P) because they are mostly soluble and remain with the effluent. Stationary screens are most commonly used but settling basins that can be cleaned with wheel tractors with front-end loaders are gaining favor as improved designs are tested. Estimated flow of N and P through several types of manure management systems show a wide range in the predicted acreage needed to achieve environmental balance. More input into these budgets by agronomists and soil scientists is needed; however, the trends are well founded and show that more acres are required when P is selected as the primary nutrient in acreage budgeting for manure disposal than when N is selected. Many soils are deficient in P so that some allowance may be possible for N criteria to be used until soil tests show that soil P reserves or groundwater levels of P are excessive. Manure management should be permitted to vary depending on differences in soil types and feeding practices on individual farms without automatically limiting farms to manure application rates appropriate for higher than actual manure excretion levels of N and P or less intensive cropping. Groundwater sampling wells on farms and regular soil sampling are also important to establish and maintain a history of environmental responsibility associated with the cropping and manure management programs.

Manure/Effluent Management | Nutrient Recycling

Overapplication of nutrients to land leads to losses of fertilizer nutrients and is a threat to the environmental standards that we want, especially with respect to water quality. Nutrient accumulation on intensive food animal production farms stems from farm imports of elemental nutrients in purchased feeds being greater than nutrient exports in food animal products. Manure management and application has been targeted specifically by regulatory agencies in recent years to try to assure that losses, especially of nitrogen (N) or phosphorus (P), are low and to avoid environmental consequences, off-site. Monitoring of potassium (K) also is encouraged. This article focuses on the development of manure nutrient management budgets and needed nutrient management strategies