J. M. Powell

Effect of forage-to-concentrate ratio in dairy cow diets on emission of methane, carbon dioxide, and ammonia, lactation performance, and manure excretion

Holstein cows housed in a modified tie-stall barn were used to determine the effect of feeding diets with different forage-to-concentrate ratios (F:C) on performance and emission of CH(4), CO(2) and manure NH(3)-N. Eight multiparous cows (means ± standard deviation): 620 ± 68 kg of body weight; 52 ± 34 d in milk and 8 primiparous cows (546 ± 38 kg of body weight; 93 ± 39 d in milk) were randomly assigned to 1 of 4 air-flow controlled chambers, constructed to fit 4 cows each. Chambers were assigned to dietary treatment sequences in a single 4 × 4 Latin square design. Dietary treatments, fed as 16.2% crude protein total mixed rations included the following F:C ratio: 47:53, 54:46, 61:39, and 68:32 [diet dry matter (DM) basis]. Forage consisted of alfalfa silage and corn silage in a 1:1 ratio. Cow performance and emission data were measured on the last 7 d and the last 4 d, respectively of each 21-d period. Air samples entering and exiting each chamber were analyzed with a photo-acoustic field gas monitor. In a companion study, fermentation pattern was studied in 8 rumen-cannulated cows. Increasing F:C ratio in the diet had no effect on DM intake (21.1 ± 1.5 kg/d), energy-corrected milk (ECM, 37.4 ± 2.2 kg/d), ECM/DM intake (1.81 ± 0.18), yield of milk fat, and manure excretion and composition; however, it increased milk fat content linearly by 7% and decreased linearly true protein, lactose, and solids-not-fat content (by 4, 1, and 2%, respectively) and yield (by 10, 6, and 6%, respectively), and milk N-to-N intake ratio. On average 93% of the N consumed by the cows in the chambers was accounted for as milk N, manure N, or emitted NH(3)-N. Increasing the F:C ratio also increased ruminal pH linearly and affected concentrations of butyrate and isovalerate quadratically. Increasing the F:C ratio from 47:53 to 68:32 increased CH(4) emission from 538 to 648 g/cow per day, but had no effect on manure NH(3)-N emission (14.1 ± 3.9 g/cow per day) and CO(2) emission (18,325 ± 2,241 g/cow per day). In this trial, CH(4) emission remained constant per unit of neutral detergent fiber intake (1g of CH(4) was emitted for every 10.3g of neutral detergent fiber consumed by the cow), but increased from 14.4 to 18.0 g/kg of ECM when the percentage of forage in the diet increased from 47 to 68%. Although the pattern of emission within a day was distinct for each gas, emissions were higher between morning feeding (0930 h) and afternoon milking (1600 h) than later in the day. Altering the level of forage within a practical range and rebalancing dietary crude protein with common feeds of the Midwest of the United States had no effects on manure NH(3)-N emission but altered CH(4) emission.

Seasonal Diet Affects Ammonia Emissions from Tie-Stall Dairy Barns

Federal and state regulations are being promulgated under the Clean Air Act to reduce hazardous air emissions from livestock operations. Although much is known about air emissions from livestock operations in Europe, few data are available on emissions from livestock facilities in the United States and the management practices that may minimize these emissions. The objective of this study was to measure seasonal and diet effects on ammonia emissions from experimental tie-stall dairy barns located in central Wisconsin. Four experimental chambers each housed 4 lactating Holstein dairy cows for three 28-d trial periods corresponding to spring, early fall, and winter. A 4 x 4 Latin square statistical design was used to evaluate 4 diets [corn silage (CS)- or alfalfa silage (AS)-based diets at low or high crude protein] in each chamber for a 4-d ammonia monitoring period. Partially due to higher crude protein levels, average ammonia-N emissions during spring (18.8 g/cow per d) were approximately twice the emissions recorded during early fall (8.4 g/cow per d) and 3 times greater than emissions during winter (6.7 g/cow per d). Ammonia-N emissions accounted for approximately 1 to 3% of consumed feed N, 2 to 5% of excreted manure N, and 4 to 11% of manure ammonical N. Nighttime ammonia emissions were on average 30% lower than daytime emissions. Forage type did not affect ammonia emissions during winter or early fall. Only during early spring were ammonia emissions lower from chambers containing cows fed low-CP diets than from cows fed high-CP diets. Of the total chamber N inputs (feed and bedding), 93, 91, and 95% were recovered in N outputs (milk, manure, body weight change, and ammonia N) during spring, early fall, and winter trials, respectively. Confidence in the accuracy of ammonia emission results was gained by the relatively high chamber N balances and favorable comparisons of study data with published relationships among the variables of feed N intake, milk urea N, manure N, and urine N excretion, and ammonia emissions.

Inverse-Dispersion Calculation of Ammonia Emissions from Wisconsin Dairy Farms

Ammonia (NH3) emissions were determined from three commercial dairy farms in the north-central U.S. The dairies employed similar management, having naturally ventilated free-stall barns where barn waste is scraped and transferred to outdoor lagoons. Three potential emission sources were distinguished at each farm: barns, lagoons, and sand separators. A backward Lagrangian stochastic (bLS) inverse-dispersion technique was used to measure emissions. Total farm emission varied from 15 to 330 kg NH3 d-1 depending on the farm and season. Inter-farm variability was largely explained by farm size (animal population). Emissions showed variability on seasonal and daily scales: summer rates were roughly ten times those of the winter, and mid-day rates were approximately three times those at night. The lagoons emitted 37% to 63% of the farm total during summer and fall, but they were frozen in winter and their emissions were immeasurably small. The yearly per-animal emissions from the three dairies were estimated at 20, 19, and 20 kg NH3 animal-1 year-1. Regarding the measurement technique, bLS proved well-suited to our study. With modest resources we were able to measure emissions from the variety of sources at each farm and quickly move between farms. Overall agreement in measured emissions at the three farms, together with a general harmony of our measurements with those from previous studies, provides a measure of confidence in the measurement strategy.

Technical note: effects of forage protein-binding polyphenols on chemistry of dairy excreta.

Forage chemistry can affect intake, digestion, milk production, and manure excretion. Although information is available on the effects of forage protein-binding polyphenols on small ruminant production and manure excretion, little information is available for dairy cattle. The objective of this study was to compare fecal and urinary N excretion of diets formulated with alfalfa (Medicago sativa L.) silage versus condensed tannin-containing birdsfoot trefoil (Lotus corniculatus) or o-quinone-containing red clover (Trifolium pratense L.) silages. Significantly higher concentrations of N were excreted in urine by lactating Holstein dairy cows fed red clover and low-tannin birdsfoot trefoil (8.2 g/L) than by cows fed high-tannin birdsfoot trefoil or alfalfa (7.1 g/L). Fecal N concentrations were similar (33.6 g/kg) among all diets. Dairy cows fed red clover had lower rates of urinary N excretion (5.0 g/h) compared with other forages (6.6 g/h). Fecal N excretion rates were lowest for red clover (4.1 g/h), intermediate for alfalfa (5.8 g/h), and greatest for cows fed high- and low-tannin birdsfoot trefoil (6.4 g/h). The ratio of fecal N to urinary N was highest for high-tannin trefoil, lowest for alfalfa and red clover, and higher in excreta collected in morning than evening. Concentrations of neutral detergent fiber (NDF) in feces, of N in NDF (NDIN) and acid detergent fiber (ADIN), and relative amounts of NDIN and ADIN excreted in feces were significantly higher from cows fed high-tannin birdsfoot trefoil than the other silage types. Study results imply that collection of excreta for environmental studies needs to consider forage polyphenol and diurnal effects on chemistry of dairy excreta.

Short communication: Evaluation of milk urea nitrogen as a management tool to reduce ammonia emissions from dairy farms

The purpose of this study was to compile and evaluate relationships between feed nitrogen (N) intake, milk urea N (MUN), urinary urea N (UUN), and ammonia (NH(3)) emissions from dairy farms to aid policy development. Regression relationships between MUN, UUN, and NH(3) emissions were compiled from studies conducted in Wisconsin, California, and the Netherlands. Relative reductions in NH(3) emissions were calculated as percentage decreases in NH(3) emissions associated with a baseline MUN level of 14 mg/dL (prevailing industry average). For 3 studies with cows in stanchion barns, relative NH(3) emission reductions of 10.3 to 28.2% were obtained when MUN declined from 14 to 10mg/dL. Similarly, analyses of 2 freestall studies provided relative NH(3) emission reductions of 10.5 to 33.7% when MUN levels declined from 14 to 10mg/dL. The relative reductions in NH(3) emissions from both stanchion and freestall barns can be associated directly with reductions in UUN excretion, which can be determined using MUN. The results of this study may help create new awareness, and perhaps eventual industry-based incentives, for management practices that enhance feed N use efficiency and reduce MUN, UUN, and NH(3) emissions from dairy farms.

Season and bedding impacts on ammonia emissions from tie-stall dairy barns.

Federal and state regulations are being promulgated under the Clean Air Act to reduce hazardous air emissions from livestock operations. Few data are available on emissions from livestock facilities in the USA and the management practices that may minimize emissions. The objective of this study was to measure seasonal and bedding impacts on ammonia emissions from tie-stall dairy barns located in central Wisconsin. Four chambers each housed four Holstein dairy heifers (approximately 17 mo of age; body weights, 427-522 kg) for three 28-d trial periods corresponding to winter, summer, and fall. A 4x4 Latin Square statistical design was used to evaluate four bedding types (manure solids, chopped newspaper, pine shavings, and chopped wheat straw) in each chamber for a 4-d ammonia monitoring period. Average ammonia-N emissions (g heifer(-1) d(-1)) during summer (20.4) and fall (21.0) were similar and twice the emissions recorded during winter (10.1). Ammonia-N emissions accounted for approximately 4 to 7% of consumed feed N, 4 to 10% of excreted N, and 9 to 20% of manure ammonical N. Cooler nighttime temperatures did not result in lower ammonia emissions than daytime temperatures. Ammonia emissions (g heifer(-1) d(-1)) from chambers that contained manure solids (20.0), newspaper (18.9), and straw (18.9) were similar and significantly greater than emissions using pine shavings (15.2). Chamber N balances, or percent difference between the inputs feed N and bedding N, and the outputs manure N, body weight N, and ammonia N were 105, 90, and 89% for the winter, summer, and fall trials, respectively. Relatively high chamber N balances and favorable comparisons of study data with published values of ammonia emissions, feed N intake, and manure N excretion provided confidence in the accuracy of the study results.

Protocols for Nationally Coordinated Laboratory and Field Research on Manure Nitrogen Mineralization

Abstract The National Program structure of USDA‐ARS provides an opportunity to coordinate research on problems of national and global significance. A team of USDA‐ARS scientists is conducting nationally coordinated research to develop predictions of manure N availability to protect water quality and improve farm solvency. Experimental design and research protocols were developed and used in common across all participating locations. Laboratory incubations are conducted at each location with a minimum of three soils, three temperatures, two wetting/drying regimes, and two manure treatments. A soil from the central United States (Catlin silt loam, fine‐silty, mixed, superactive, mesic Oxyaquic Argiudoll) is used as an internal reference across all locations. Incubation data are compiled across locations to develop generalized predictions of manure nitrogen mineralization (Nmin). Field validation data are then obtained by monitoring nitrogen (N) transformations in manure‐amended soil cores equipped with anion exchange resin to capture leached nitrate. This field data will be used to compare laboratory‐based predictions with field observations of Nmin in each soil, climatic zone, and manure type represented. A Decision Support System will then be developed for predicting manure N mineralization across ranges in soil, climate, and manure composition. Protocols used by this research team are provided to 1) document the procedures used and 2) offer others detailed information for conducting research on nutrient transformation processes involving collaboration across locations or complementary research between laboratory and field environments.

Measures of nitrogen use efficiency and nitrogen loss from dairy production systems.

In dairy production systems, tradeoffs can occur between fertilizer N applications and crop N use, feed N consumption and manure N excretion, and environmental impacts. This paper examines (i) how stocking rates affect N imports and management on dairy farms, N use efficiency (NUE; i.e., the amount of applied N incorporated into product N), and N loss; (ii) how reductions in fertilizer N and feed N may affect crop and milk production, NUE, and N loss; and (iii) why tradeoffs in N use outcomes should be considered when attempting to enhance overall NUE and reduce N loss. The Integrated Farm Simulation Model simulations of two representative dairy farm types and analyses of regional studies, long-term field experiments, and cow nutrition trials were used to demonstrate that (i) stocking rate affects cropping patterns, fertilizer and feed imports, and N loss; (ii) although fertilizer N reductions of 20 kg N ha may reduce slightly the crude protein (CP) content of corn silage (which would require purchase of additional CP supplements), this practice should not affect long-term corn yield but would reduce nitrate (NO) and nitrous oxide (NO) losses by 13 to 38%; (iii) dietary CP could be reduced on many dairy farms, which would not affect milk production but would reduce ammonia (NH) and NO emissions by 15 to 43%; and (iv) greater recognition of the tradeoffs in N use and N loss are needed to provide a better understanding of the potentials to enhance overall NUE and reduce environmental N loss from dairy production systems.

Phosphorus feeding andmanure nutrient recycling on Wisconsin dairy farms

Recently approved nutrient management regulations for livestock operations focus on a farm’s ability to recycle the phosphorus (P) contained in manure. Most efforts to improve dairy manure management emphasize manure handling, storage, and land application techniques. Little is known about relationships between dairy feeding practices and manure P levels under farm conditions, or between herd size, cropland area and a farm’s ability to recycle manure P through crops. A survey of 98 representative dairy farms in Wisconsin showed that most farms were self-sufficient in forage (alfalfa, corn silage) and grain production. Lactating dairy cows derived 90% of their feed dry matter (DM) and 78% of their P intake from these homegrown feeds. The P content (DM basis) of the dairy diet ranged from 2.3 to 8.5 with an average of 4.0g P kg−1. Approximately 85% of the surveyed dairy farms fed P in excess of the recently updated National Research Council (NRC) requirements. On these farms, amounts of P in manure were related to dietary P. Of the annual manure P excreted by cows fed a diet supplement, approximately two-thirds is derived from homegrown feeds and one-third from imported mineral and protein supplements. Stocking rates ranged from 0.19 to 1.68 AU ha−1. Farms having stocking rates of less than 0.70 AU ha−1 are self-sufficient in feed production. Approximately half of the farms are self-sufficient in feed production, 68% produce 90%, and 80% produce 80% of their annual feed requirement. Approximately 40% of the farms have a positive P balance (manure P exceeds harvested crop P). On these farms, lowering dietary P to the levels recommended by NRC would reduce the number of farms having a positive P balance by 67%, and the land area in positive P balance by 60%. For farms having a high animal stocking rate, manure export, the addition of cropland for manure spreading, and/or reductions in livestock (cow and/or heifer) numbers may be the only feasible strategies for achieving P balance on a farm.

Emissions of ammonia, nitrous oxide, methane, and carbon dioxide during storage of dairy cow manure as affected by dietary forage-to-concentrate ratio and crust formation.

Sixteen 200-L barrels were used to determine the effects of dietary forage-to-concentrate (F:C) ratio on the rate of NH(3)-N, N(2)O, CH(4), and CO(2) emissions from dairy manure during a 77-d storage period. Manure was obtained from a companion study where cows were assigned to total mixed rations that included the following F:C ratio: 47:53, 54:46, 61:39, and 68:32 (diet dry matter basis) and housed in air-flow-controlled chambers constructed in a modified tiestall barn. On d 0 of this study, deposited manure and bedding from each emission chamber was thoroughly mixed, diluted with water (1.9 to 1 manure-to-water ratio) and loaded in barrels. In addition, on d 0, 7, 14, 28, 35, 49, 56, 63, 70, and 77 of storage, the rate of NH(3)-N, N(2)O, CH(4), and CO(2) emissions from each barrel were measured with a dynamic chamber and gas concentration measured with a photo-acoustic multi-gas monitor. Data were analyzed as a randomized complete block with 4 replications. Dietary F:C ratio had no effect on manure dry matter, total N and total ammoniacal-N (NH(3)-N + NH(4)(+)-N), or pH at the time of storage (mean ± SD: 10.6±0.6%, 3.0±0.2%, 93.1±18.1 mg/dL, and 7.8±0.5, respectively). No treatment differences were observed in the overall rate of manure NH(3)-N, N(2)O, CH(4), and CO(2) emissions (mean ± SD over the 77-d storage period; 117±25, 30±7, 299±62, and 15,396±753 mg/hr per m(2), respectively). The presence of straw bedding in manure promoted the formation of a surface crust that became air dried after about 1 mo of storage, and was associated with an altered pattern in NH(3)-N and N(2)O emissions in particular. Whereas NH(3)-N emission rate was highest on d 0 and gradually decreased until reaching negligible levels on d 35, N(2)O emission rate was almost zero the first 2 wk of storage, increased sharply to peak on d 35, and decreased subsequently. The emission rate of CH(4) and CO(2) peaked simultaneously on d 7, but decreased subsequently until the end of the storage period. In this study, C:N ratio of gaseous losses was 32:1, reflecting higher volatile C loss than volatile N loss during storage. On a CO(2)-equivalent basis, the most important source of non-CO(2) greenhouse gas emitted was CH(4) until formation of an air-dried crust, but N(2)O thereafter. Taken together, these results suggested that the formation of an air-dried crust resulting from the straw bedding present in the manure reduced drastically NH(3)-N, and CH(4) emissions, but was conducive of N(2)O production and emission.