Wendy J. Powers

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.

Grazing Management Effects on Sediment and Phosphorus in Surface Runoff

Abstract Sediment and phosphorus (P) in runoff from pastures are potential non–point-source pollutants in surface waters that may be influenced by surface cover, sward height, treading damage, surface slope, soil moisture, and soil P. The objectives of the current study were to quantify sediment and total P loads in runoff produced during simulated rainfall from pastures and to evaluate their relationships with the physical and chemical characteristics of the soil and sward. Five forage management treatments—ungrazed (U), hay harvest/fall stockpile grazing (HS), continuous stocking to a sward height of 5 cm (5C), and rotational stocking to sward heights of 5 (5R) or 10 (10R) cm—were established in triplicate 0.40-ha paddocks in 3 smooth bromegrass (Bromus inermis Leyss.) pastures for 3 years. Rainfall simulations were conducted at a rainfall intensity of 7.1 cm·h−1 for 1.5 hours over a 0.5-m2 area in 3 locations at 2 slope ranges in each paddock in June, August, and October of each year and the subsequent April. Forage management did not affect mean sediment load (7.3 ± 5.0 kg·ha−1·h−1). Mean total P load was greatest from 5C treatment (0.071 ± 0.011 kg·ha−1·h−1), did not differ among the U, HS, and 10R treatments (0.019 ± 0.011 kg·ha−1·h−1), and was intermediate in the 5R treatment (0.053 ± 0.011 kg·ha−1·h−1). Of the soil and sward characteristics measured, percentage surface cover was most highly related to sediment load (R2 = 0.16) and total P load (R2 = 0.10). Surface runoff from pastures managed to maintain adequate residual forage cover did not contribute greater sediment or P to surface waters than an ungrazed grassland.

GEOTEXTILE COVERS TO REDUCE ODOR AND GAS EMISSIONS FROM SWINE MANURE STORAGE PONDS

Odor, hydrogen sulfide (H2S), ammonia (NH3), and volatile organic compounds (VOC, GC/MS analytes) were measured between May and October 2000, and between April and October 2001 at sites representing three different swine production facilities (8000-head nursery, 2000-head finishing, and 3000-head finishing) in southwestern Minnesota. For each facility type, two farms were tested. The paired farms had similar manure storage ponds, production phases, herd sizes, genetics, and diet formulations. A manure storage pond from each pair of farms was selected as treatment (with geotextile cover, Biocap.), and the other as control (without cover). Results showed reductions in odor, H2S, and NH3 flux rates due to the geotextile cover, but performance in reducing odor and H2S deteriorated during the second year of the study. No significant differences in VOC (GC/MS analytes) emissions from covered and non-covered manure storage ponds were observed during the two-year study. Analysis of ambient H2S data suggested the covers were effective in reducing ambient H2S concentrations near manure storage ponds located at the two finishing units. Odor and gaseous flux rates were poorly correlated with relevant manure parameters (NH3 -N, sulfides, and VOC).

A Review of the Capacity for Nutritional Strategies to Address Environmental Challenges in Poultry Production

Poultry production faces increasing environmental challenges, in the United States and globally. Although the environmental impact of poultry production has been decreased, regulatory and social pressures mandate that further improvements be made to decrease the pollution potential even more. Concerns over air and water quality to date have been related primarily to nutrient issues, specifically N and P. Air emission concerns include N and sulfur emissions. More recently, states have addressed emissions of volatile organic compounds. Although no regulations have been developed that are targeted at food production, greenhouse gas emissions are receiving a great deal of attention in the United States. Nutrient-related water quality concerns have focused on N and P contributions to ground and surface waters, respectively. To address nutrient-related air and water quality concerns, nutritional strategies have focused on reducing nutrient excretions. These strategies have been very successful. However, strategies beyond just reducing nutrient excesses will be needed to meet future challenges that are not nutrient-related. Challenges such as pathogens, antimicrobials, and endocrine-disrupting compounds have received considerable attention recently. The purpose of this review is to provide an overview of the findings from nutrition research with respect to reducing environmental impact and to identify areas that merit attention in the near future, recognizing that many of the emerging environmental issues are not nutrient-related.

The effect of incremental levels of dietary nitrate on methane emissions in Holstein steers and performance in nelore bulls

Two experiments were conducted to study effects of dietary nitrate on enteric methane production, blood methemoglobin concentration, and growth rate in cattle. In Exp. 1, 36 Holstein steers (288 ± 25 kg BW) were fed increasing levels of dietary nitrate (6 levels; 0 to 3.0% of feed DM) in corn silage-based total mixed rations. Nitrate was introduced gradually in a 25-d adaptation period before methane production was determined in environmentally controlled rooms. In the rooms, feed intake was restricted and similar among all treatments. Methane production (g/d) decreased linearly as dietary nitrate concentration increased (P < 0.01). The apparent efficiency (measured methane reduction divided by potential methane reduction) with which enteric methane was mitigated was 49%. Blood methemoglobin levels increased with increasing nitrate dose. In Exp. 2, 300 Nelore bulls (392 ± 28 kg) were fed increasing levels of nitrate (6 levels; 0 to 2.4% of feed DM) in high-concentrate total mixed rations offered ad libitum. Feed intake decreased linearly with increasing level of dietary nitrate (P < 0.01). However, ADG was not affected by nitrate dose (P = 0.54), resulting in a linear improvement in G:F (P = 0.03) as dietary nitrate level increased. Carcass dressing percentage showed a quadratic response to incremental dietary nitrate, reaching the highest value at 0.96% of NO3/kg DM (P = 0.04).

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.

The use of distillers dried grains plus solubles as a feed ingredient on air emissions and performance from laying hens

The objectives of the current study were to evaluate the effect of feeding diets containing 0, 10, or 20% distillers dried grains plus solubles (DDGS) to laying hens (21 to 26 wk of age) on emissions of NH3 and H2S. Hy-Line W-36 hens (n = 640) were allocated randomly to 8 environmental rooms for a 5-wk period (hens in 3 rooms were offered the 10% and 20% DDGS diets each; hens in 2 rooms were offered the 0% DDGS diet). Diets were formulated to contain similar CP levels (18.3%), nonphytate P (0.46%), and Ca (4.2%). On an analyzed basis, the 0, 10, and 20% DDGS diets contained 0.22, 0.27, and 0.42% S. Egg weight (50.9 g), egg production (85%), and feed intake (87.9 g/hen per d) were unaffected by diet (P > 0.05) over the study period. Daily NH3 emissions from hens fed diets containing 0, 10, and 20% DDGS were 105.4, 91.7, and 80.2 mg/g of N consumed, respectively (P < 0.05). Daily H2S emissions from hens fed commercial diets containing 0, 10, and 20% DDGS were 2.6, 2.4, and 1.1 mg/g of S consumed, respectively. Overall, feeding 21- to 26-wk-old laying hens diets containing 20% DDGS decreased daily NH3 emissions by 24% and H2S emissions by 58%. Each hen emitted approximately 280 mg of NH3 and 0.5 mg of H2S daily when fed a control diet containing 18% CP and 0.2% S. The results of this study demonstrate that 20% DDGS derived from ethanol production can be fed to laying hens, resulting in lower emissions of NH3 and H2S with no apparent adverse effects on hen performance.

Reduced Crude Protein Effects on Aerial Emissions from Swine

The effect of feeding reduced crude protein (CP) diets on air emissions was evaluated using barrows fed over the course of four feeding phases: G1 (beginning at 24.5 kg BW), G2 (55.3 kg), F1 (87.2 kg), and F2 (111.4 kg). Pigs were offered a control diet (C), a low CP diet (LCP) or an ultra low CP diet (ULCP). Both the LCP and ULCP diets were supplemented with crystalline amino acids to avoid performance loss. Analyzed CP of G1 was 22.1%, 18.8%, and 17.2% for the C, LCP, and ULCP diets, respectively. Dietary treatment had no effect on pig performance (P > 0.05). Ammonia concentrations were reduced 24% (2.93 ppm) in the ULCP diets compared to the LCP diet and 36% compared to the C diet. Pigs fed the LCP diet produced exhaust NH3 concentrations 16% less than pigs fed the C diet (3.86 vs. 4.57 ppm). Rates of NH3 emissions for the C, LCP, and ULCP diet, corresponded to a daily mass of NH3 emitted of 88.0, 68.9, and 46.0 mg kg-1 BW, respectively. Feeding phase effects were observed for NH3 concentration, NH3 emission rate, daily mass emitted and daily mass per unit BW, hydrogen sulfide (H2S) concentration, and daily emitted mass of H2S per unit body weight. No diet effects were observed for H2S. Diet had no effect on mass of manure produced; however TKN and NH3-N concentration decreased with decreasing diet CP (79, 67, 57 g kg-1 and 54, 44, and 35 g kg-1, respectively, for C, LCP, and ULCP diets).

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.