Impact of separating dairy cattle excretions on ammonia emissions.

About 80% of dairy cattle N intake is excreted in urine and feces. Urinary-N is about 75% urea, whereas fecal-N is mostly organic. Urinary-N (urea) can only be volatilized when it is hydrolyzed to ammonia (NH3) in a process catalyzed by urease, which is predominantly found in feces. Minimizing contact between urine and feces may be an effective approach to reducing urea hydrolysis and subsequent NH3 emissions. Previous studies have reported 5 to 99% NH3 emissions mitigation within barns from separation of feces and urine. The objective ofthis study was to compare NH3 emissions mitigation via separation of urine and feces in postcollection storage to a conventional scrape manure handling method where urine and feces are comingled. Laboratory scale studies were conducted to evaluate NH3 emissions from simulated postcollection storag of three waste streams: (i) idealistically separated feces and urine (no contact between urine and feces), (ii) realistically separated urine and feces (limited contact of urine and feces), and (iii) conventionally scraped manure (control). From the results of these studies, NH3 losses ranking in descending order was as follows: aggregate of realistically separated waste streams (3375.9 +/- 54.8 mg), aggregate of idealistically separated urine and feces (3047.0 +/- 738.0 mg), and scrape manure (2034.0 +/- 106.5 mg), respectively. Therefore, on the basis of these results, the extra effort of separating the waste streams would not enhance mitigation of NH3 losses from postcollection storage of the separated waste streams compared to the conventional scrape manure collection system.

Effect of dietary concentrate on rumen fermentation, digestibility, and nitrogen losses in dairy cows.

The objective of this experiment was to investigate the effect of level of dietary concentrate on rumen fermentation, digestibility, and N losses in lactating dairy cows. The experiment was a replicated 3x3 Latin square design with 6 cows and 16-d adaptation periods. Ruminal contents were exchanged between cows at the beginning of each adaptation period. Data for 2 of the diets tested in this experiment are presented here. The diets contained (dry matter basis): 52% (LowC; control) and 72% (HighC) concentrate feeds. Crude protein contents of the diets were 16.5 and 16.4%, respectively. The HighC diet decreased ruminal pH and ammonia concentration and increased propionate concentration compared with LowC. Acetate:propionate ratio was greater for LowC than for HighC. Rumen methane production and microbial protein synthesis were unaffected by diet. Dry matter intake was similar among diets, but milk yield was increased by HighC compared with LowC (36.0 and 33.2 kg/d, respectively). Milk fat percentage and yield and total-tract apparent NDF digestibility were decreased by HighC compared with LowC. More ruminal ammonia N was transferred into milk protein with HighC than with LowC. Urinary N excretion, plasma urea N, and milk urea N concentration were not affected by diet. The ammonia emitting potential of manure was similar between LowC and HighC diets. Increased concentrate proportion in the diet of dairy cows resulted in reduced ruminal ammonia concentration and enhanced ammonia utilization for milk protein synthesis. These effects, however, did not result in reduced urinary N losses and only marginally improved milk N efficiency. Increasing dietary concentrate was not a successful strategy to mitigate enteric methane production and ammonia emissions from manure.

The effects of ruminally degraded protein on rumen fermentation and ammonia losses from manure in dairy cows.

This experiment investigated the effect of dietary crude protein (CP) and ruminally degraded protein (RDP) levels on rumen fermentation, digestibility, ammonia emission from manure, and performance of lactating dairy cows. The experiment was a replicated 3 x 3 Latin square design with 6 cows. Three diets varying in CP concentration were tested (CP, % of dry matter): 15.4 (high CP, control), 13.4 (medium CP), and 12.9% (low CP). These diets provided metabolizable protein balances of 323, -44, and 40 g/d and RDP balances of 162, -326, and -636 g/d (high, medium, and low, respectively). Both the medium and low CP diets decreased ruminal pH compared with high CP, most likely because of the higher nonfiber carbohydrate concentration in the former diets. Ruminal ammonia pool size (rumen ammonia N was labeled with (15)N) and the concentration of total free amino acids were greater for the high CP diet than for the RDP-deficient diets. Apparent total-tract nutrient digestibilities were not affected by treatment. Both the medium and low CP diets resulted in lower absolute and relative excretion of urinary N compared with the high CP diet, as a proportion of N intake. Excretion of fecal N and milk yield and composition were not affected by diet. Milk N efficiency (milk N / N intake) and the cumulative secretion of ammonia-(15)N in milk protein were greater for the RDP-deficient diets, and milk urea N concentration was greater for the high CP diet. Both medium and low CP diets decreased the irreversible loss of ruminal ammonia N compared with the high CP diet. The rate and cumulative ammonia emissions from manure were lower for the medium and low CP diets compared with the high CP diet. Overall, this study demonstrated that dairy diets with reduced CP and RDP concentrations will produce manure with lower ammonia-emitting potential without affecting cow performance, if metabolizable protein requirements are met.

Effect of lauric acid and coconut oil on ruminal fermentation, digestion, ammonia losses from manure, and milk fatty acid composition in lactating cows.

This experiment (replicated 3 x 3 Latin square design) was conducted to investigate the effects of lauric acid (LA) or coconut oil (CO) on ruminal fermentation, nutrient digestibility, ammonia losses from manure, and milk fatty acid (FA) composition in lactating cows. Treatments consisted of intraruminal doses of 240 g of stearic acid/d (SA; control), 240 g of LA/d, or 530 g of CO/d administered once daily, before feeding. Between periods, cows were inoculated with ruminal contents from donor cows and allowed a 7-d recovery period. Treatment did not affect dry matter intake, milk yield, or milk composition. Ruminal pH was slightly increased by CO compared with the other treatments, whereas LA and CO decreased ruminal ammonia concentration compared with SA. Both LA and CO decreased protozoal counts by 80% or more compared with SA. Methane production rate in the rumen was reduced by CO compared with LA and SA, with no differences between LA and SA. Treatments had no effect on total tract apparent dry matter, organic matter, N, and neutral detergent fiber digestibility coefficients or on cumulative (15 d) in vitro ammonia losses from manure. Compared with SA, LA and CO increased milk fat 12:0, cis-9 12:1, and trans-9 12:1 content and decreased 6:0, 8:0, 10:0, cis-9 10:1, 16:0, 18:0, cis 18:1, total 18:2, 18:3 n-3 and total polyunsaturated FA concentrations. Administration of LA and 14:0 (as CO) in the rumen were apparently transferred into milk fat with a mean efficiency of 18 and 15%, respectively. In conclusion, current data confirmed that LA and CO exhibit strong antiprotozoal activity when dosed intraruminally, an effect that is accompanied by decreases in ammonia concentration and, for CO, lowered methane production. Administration of LA and CO in the rumen also altered milk FA composition.

Measuring concentrations of ammonia in ambient air or exhaust air stream using acid traps.

Strong acid solutions have been widely used in acid traps to determine concentrations of ammonia in ambient air or exhaust air stream. A literature survey indicates the method has a long history and a wide variation in use. Through a series of studies, this paper examines several factors including volume of the acid, depth of the acid, and airflow rate; that might affect the efficiency of sulfuric acid traps and recommends steps researchers and other users may take to ensure reliable results from this method. The results from these series of studies indicate: (i) an inverse relationship between the efficiency of the acid traps and the amount of ammonia to be trapped even when the capacity of the acid trap is excessively greater than the maximum theoretical stoichiometric capacity needed to dissolve all of the ammonia, (ii) for the same volume of acid, the efficiency of the acid trap increased with the acid depth but overall, the efficiency at any given acid depth decreased as the amount of ammonia through the trap increased, and (iii) at the two airflow rates examined in this study (0.5 and 1.0 L/min) the efficiency of the acid traps decreased at similar rates as the concentration of ammonia in the sample air increased but the efficiency of the trap was significantly higher at the lower airflow rate. To obtain reliable measurements from this method, therefore, multi-point calibrations within the entire range of target measurements is recommended to provide accurate corrections of the measurements.

Effects of cycle-frequency and temperature on the performance of anaerobic sequencing batch reactors (ASBRs) treating swine waste.

Anaerobic digestion of animal waste is a technically viable process for the abatement of adverse environmental impacts caused by animal wastes; however, widespread acceptance has been plagued by poor economics. This situation is dismal if the technology is adapted for treating low strength animal slurries because of large digester-volume requirements and a corresponding high energy input. A possible technology to address these constraints is the anaerobic sequencing batch reactor (ASBR). The ASBR technology has demonstrated remarkable potential to improve the economics of treating dilute animal waste effluents. This paper presents preliminary data on the effects of temperature and frequency-cycle on the operation of an ASBR at a fixed hydraulic retention time (HRT). The results suggest that within the parameter range under consideration, temperature did not affect the biogas yield significantly, however, higher cycle-frequency had a negative effect. The biogas quality (%CH(4)) was not significantly affected by temperature nor by the cycle-frequency. The operating principle of the ASBR follows four phases: feed, react, settle, and decant in a cyclic mode. To improve the biogas production in an ASBR, one long react-phase was preferable compared to three shorter react-phases. Treatment of dilute manure slurries in an ASBR at 20 degrees C was more effective than at 35 degrees C; similarly more bio-stable effluents were obtained at low cycle-frequency. The treatment of dilute swine slurries in an ASBR at the lower temperature (20 degrees C) and lower cycle-frequency is, therefore, recommended for the bio-stabilization of dilute swine wastewaters. The results also indicate that significantly higher VFA degradation occurred at 20 degrees C than at 35 degrees C, suggesting that the treatment of dilute swine slurries in ASBRs for odor control might be more favorable at the lower than at the higher temperatures examined in this study. Volatile fatty acid reduction at the two reactor temperatures and cycle-frequencies, from a high of 639+/-75 mg/L to a low of 92+/-23 mg/L, greatly reduced the odor and the odor-generation potential in post-treatment storage. The nutrients (both N and P) in the waste influent were conserved in the effluents.

Tsetse and other biting fly responses to Nzi traps baited with octenol, phenols and acetone.

Octenol (1-octen-3-ol), acetone, 4-methylphenol, 3-n-propylphenol, and other potential attractants (human urine, stable fly faeces), as well as guiacol, creosol (potential repellents), were tested as baits for biting flies in North America using standard phthalogen blue IF3GM cotton Nzi traps, or similar commercial polyester traps. Baits were tested during the summers of 2001-04 at a residence in Canada and during January-August 2001 at a dairy in the U.S.A. Behaviour in the presence of octenol was also studied by intercepting flies approaching a trap through the use of transparent adhesive film. Analogous bait and/or trap comparisons were conducted in natural settings in June 1996 in Kenya and in September-December 1997 in Ethiopia. In Canada, catches of five of six common tabanids (Tabanus similis Macquart, Tabanus quinquevittatus Wiedemann, Hybomitra lasiophthalma [Macquart], Chrysops univittatus Macquart, Chrysops aberrans Philip) and the stable fly Stomoxys calcitrans L. were increased significantly by 1.2-2.1 times with octenol (1.5 mg/h). Catches of T. quinquevittatus and S. calcitrans were 3.5-3.6 times higher on a sticky enclosure surrounding a trap baited with octenol. No other baits or bait combinations had an effect on trap catches in North America. In Ethiopia, standard Nzi traps baited with a combination of acetone, octenol and cattle urine caught 1.8-9.9 times as many Stomoxys as similarly baited epsilon, pyramidal, NG2G, S3, biconical and canopy traps, in order of decreasing catch. When baits were compared, catches in Nzi traps of six stable fly species, including S. calcitrans, were not affected by octenol (released at approximately 1 mg/h), or cattle urine (140 mg/h), used alone or in combination with acetone (890 mg/h). Acetone alone, however, significantly increased the catches of common Stomoxys such as Stomoxys niger niger Macquart, Stomoxys taeniatus Bigot, and S. calcitrans by 2.4, 1.6 and 1.9 times, respectively. Catches of Glossina pallidipes Austen were increased significantly in traps baited with acetone, urine or octenol, or any combination, relative to those in unbaited traps (1.4-3.6x). Catches of Glossina morsitans submorsitans Newstead were increased significantly by 1.5-1.7 times, but only when baits were used individually. Unlike other studies with East African tsetse, catches of both tsetse species with the complete bait combination (acetone, urine and octenol) did not differ from those in unbaited traps. Experiments with an incomplete ring of electric nets surrounding a Nzi trap, and a new approach using a sticky enclosure made from transparent adhesive film, revealed diverse responses to artificial objects and baits among biting flies. In Kenya, daily trap efficiency estimates for traps baited with either carbon dioxide (6 L/min) or a combination of acetone, cattle urine and octenol were 21-27% for G. pallidipes, 7-36% for Glossina longipennis Corti, 27-33% for S. n. niger, and 19-33% for Stomoxys niger bilineatus Grünberg, assuming 100% electrocution efficiency. Actual trap efficiencies may have been lower, given observed outside : inside electric net catch ratios of 0.6 : 1.6. Observed ratios averaged 54% of expected values, with 10 of 15 possible ratios less than the minimum possible value of 1.0.

Effects of bioreactor temperature and time on odor-related parameters in aerated swine manure slurries.

Previous studies have linked odor generation from swine manure to some characteristics of the liquid manure such oxidation-reduction potential (ORP), five-day biochemical oxygen demand (BOD5), volatile fatty acids (VFAs), and predominant microbial population. This study investigated the effect of bioreactor temperature and time on the aforementioned parameters during aeration of swine manure. Five reactors (13 1 capacity) loaded with swine manure and maintained at temperatures of 5, 10, 15, 20, and 25 degrees C, were supplied with air for 15 days to maintain aerobic conditions. Large fluctuations in ORP (-120 to 360 mV) were observed in the first seven days of aeration, which stabilized thereafter regardless of the bioreactor temperature. The percentage removal of VFAs and BOD5 in the manure significantly increased from 0.0% on day one to 87.8% and 65.3%, respectively, on day nine, and remained relatively constant thereafter. The mean percentage of VFAs and BOD5 removed also increased significantly with an increase in the bioreactor temperature. The VFAs and BOD5 removal increased by approximately 25% and 35%, respectively, in going from 5 to 25 degrees C, during the 15 days of aeration. Both VFAs and BOD5 in the manure were significantly correlated with ORP, aerobic bacteria, and anaerobic bacteria. The data suggested that continued aeration for seven days at 20 or 25 degrees C was sufficient for significant reduction of odor precursors (VFAs and BOD5) and in stabilization of swine manure. A linear correlation of 0.97 between VFAs and BOD5 indicated that the two parameters can be used interchangeably as indicators of odor release potential in swine manure.

Development of an exposure-free bednet trap for sampling Afrotropical malaria vectors.

An exposure-free bednet trap (the 'Mbita trap') for sampling of Afrotropical malaria vectors was developed during preliminary studies of mosquito behaviour around human-occupied bednets. Its mosquito sampling efficiency was compared to the CDC miniature light-trap and human landing catches under semi-field conditions in a screen-walled greenhouse using laboratory-reared Anopheles gambiae Giles sensu stricto (Diptera: Culicidae). When compared in a competitive manner (side by side), the Mbita trap caught 4.1+/-0.5 times as many mosquitoes as the CDC light-trap, hung beside an occupied bednet (P < 0.000 1) and 43.2+/-10% the number caught by human landing catches (P < 0.0001). The ratio of Mbita trap catches to those of the CDC light trap increased with decreasing mosquito density. Mosquito density did not affect the ratio of Mbita trap to human-landing catches. In a non-competitive comparison (each method independent of the other), the Mbita trap caught 89.7+/-10% the number of mosquitoes caught by human landing catches (P < 0.0001) and 1.2+/-0.1 times more mosquitoes than the CDC light trap (P = 0.0008). Differences in Mbita trap performance relative to the human landing catch under noncompetitive vs. competitive conditions were explained by the rate at which each method captured mosquitoes. Such bednet traps do not expose people to potentially infectious mosquito bites and operate passively all night without the need for skilled personnel. This trap is specifically designed to catch host-seeking mosquitoes only and may be an effective, sensitive, user-friendly and economic alternative to existing methods for mosquito surveillance in Africa.

The effect of limited aeration on swine manure phosphorus removal.

Two low level aeration schemes (intermittent vs. continuous) were investigated on a laboratory scale, in conjunction with swine manure pH adjustment using sodium hydroxide (1.0 M), for manure phosphorus (P) removal. According to the data, an 80% reduction in soluble P was observed when the manure pH was increased to 8. Both intermittent and continuous aeration treatments could raise manure pH above 8 with an airflow rate of 1 L/minute in a period of 15 days. A drastic increase in pH (about 1 unit) was observed for both aeration schemes within the first day of test, resulting in a 76% reduction in soluble P concentration in the liquid. It appeared that there is no difference in terms of P removal between the two aeration programs, suggesting that the intermittent aeration be preferred to save energy while still achieving the same level of P removal.

Integrating composting and vermicomposting in the treatment and bioconversion of biosolids.

Traditional thermophilic composting is commonly adopted for treatment of organic wastes or for production of organic/natural fertilizers. A related technique, called vermicomposting (using earthworms to breakdown the organic wastes) is also becoming popular. These two techniques have their inherent advantages and disadvantages. The integrated approach suggested in this study borrows pertinent attributes from each of these two processes and combines them to enhance the overall process and improve the products qualities. Two approaches investigated in this study are: (1) pre-composting followed by vermicomposting, and (2) pre-vermicomposting followed by composting. The substrate was biosolids (activated sewage sludge) with mixed paper-mulch as the carbon base. Eisenia fetida (red wigglers) was the species of earthworms used in the vermicomposting processes. The results indicate that, a system that combines the two processes not only shortens stabilization time, but also improves the products quality. Combining the two systems resulted in a product that was more stable and consistent (homogenous), had less potential impact on the environment and for compost-vermicomposting (CV) system, the product met the pathogen reduction requirements.

Effect of solid-liquid separation on BOD and VFA in swine manure.

Fresh swine manure was sieved into seven different particle size categories, i.e., <0.075 mm, < 0.15 mm, < 0.25 mm, < 0.5 min, < 1.0 mm, < 1.4 mm, and < 2.0 mm. Manure was stored in seven PVC columns and sampled every 5 days up to 30 days. Manure samples were analyzed for total volatile fatty acids (VFAs), 5-day biochemical oxygen demand (BOD5), total solids (TS), total suspended solids (TSS), and total volatile solids (TVS). Two parameters (VFAs and BOD5) were used to determine the odor generation potential of the test manure. The results showed that total VFAs correlated well with BOD5 (R2 = 0.8297). The levels of ISS only explained 40% of BOD5 and 46% of VFAs, both of which increased with storage time, regardless of solid particle sizes. Also, the data inferred that most of the odorous compounds (measured by VFA and BOD levels) were contained in manure solid particles less than 0.075 mm. These cannot be removed by commercial mechanical separators with screen size ranging from 0.5 to 3.0 mm. With an average separation efficiency of 25% for most commercially available mechanical separators, the removal efficiencies of BOD5 and VFAs were as low as 10% and 12%, respectively. These findings cannot justify the use of solid-liquid separation tocontrol odor. Data also showed that for swine manure, it is critical to run separation treatment within the first ten days after the manure is excreted to potentially improve the separation efficiency. After ten days, the degradation of TSS was accelerated due to the increased biological activities, which may greatly reduce the separation efficiency.

Isolation of Trypanosoma spp. from wild tsetse flies through procyclic expansion in Glossina morsitans centralis.

Procyclic trypanosomes from wild tsetse flies were membrane-fed to Glossina morsitans centralis in order to develop an optimal technique for propagating field isolates. A 70% success rate was achieved in isolating Trypanosoma simiae and a variety of genotypes of T. congolense originating from G. pallidipes, G. brevipalpis and G. swynnertoni. Parasites matured into forms infective for mammals, and could be maintained by passage of gut forms to new groups of flies. In experiments with laboratory stocks, we also passaged immature gut infections of T. congolense and T. brucei from various tsetse species to G. m. centralis. The optimal technique was investigated for procyclic T. congolense through addition of various compounds to goat blood using G. m. centralis and G. m. morsitans as recipients. From these experiments, many approaches to procyclic expansion appeared possible. However, a simple and practical method based on the use of fresh goat blood for rapid feeding of G. m. centralis is recommended. Application of this technique should aid in the resolution of questions relating to the cryptic diversity of Nannomonas trypanosomes in diverse host and vector communities.

Effect of puparia incubation temperature: increased infection rates of Trypanosoma congolense in Glossina morsitans centralis, G. fuscipes fuscipes and G. brevipalpis.

Puparia of Glossina morsitans centralis (Machado), G.fuscipes fuscipes (Newstead) and G.brevipalpis (Newstead) were incubated at 25 +/- 1 degrees C, 28 +/- 1:25 +/- 1 degrees C, day:night or 29 +/- 1 degrees C throughout the puparial period, and maintained at 70-80% relative humidity. Puparial mortality was higher at 29 than at 25 degrees C (optimum temperature) in all three species, particularly in G.f.fuscipes and G.brevipalpis. Adults of G.m.centralis from puparia incubated at 29 degrees C, and those of this subspecies, G.f.fuscipes and G.brevipalpis from puparia incubated at 28:25 degrees C, day:night or 25 degrees C throughout, were infected as tenerals (27 h old) by feeding them at the same time on goats infected with Trypanosoma congolense (Broden) IL 1180 after the parasites were detected in the wet blood film. Infection rates on day 25 post-infected feed were higher in G.m.centralis from puparia incubated at 29 degrees C and in adults of the three different tsetse species from puparia incubated at 28:25 degrees C, day:night, than in those from puparia incubated at 25 degrees C. However, in G.f.fuscipes the labral and hypopharyngeal infection rates were not significantly different from those of the tsetse produced by puparia kept at 25 degrees C.

A comparative study of the neutralising capacity of eight brands of antacids.

Eight brands of antacid tablets commonly available in the private market in Kenya were subjected to in-vitro tests for neutralizing capacity. The neutralizing capacity per gram and per tablet of the products was compared. The neutralizing capacity in millilitres of 0.1 M HC1 per gram ranged from 103.10 for Gelusil to 225.13 for Maalox, with others ranging between +/- 18.1% and -12% about the average. The neutralizing capacity per tablet ranged from 64.90 ml for Magnesium trisilicate Co tablets B.P. to 263.15 ml for Maalox, with the others ranging between +/- 24.9% and -33.1% about the average. This shows high variation in the neutralizing capacities of the different brands available especially in relations to the neutralizing capacities per tablet due to the high variation in the tablet weight.