Short communication: Survey of animal-borne pathogens in the farm environment of 13 dairy operations.

A survey was conducted on 13 dairies to determine the occurrence of 5 animal-borne pathogens (Salmonella enterica, Escherichia coli O157:H7, Campylobacter jejuni, Mycobacterium avium ssp. paratuberculosis, and Cryptosporidium parvum) and their distributions across farm elements (feces, bedding, milk filters, stored manure, field soil, and stream water). Presence of C. parvum was measured only in feces and stored manure. All but one farm were positive for at least one pathogen species, and 5 farms were positive for 3 species. Escherichia coli O157:H7 was detected on 6 farms and in all farm elements, including milk filters. Mycobacterium avium ssp. paratuberculosis was detected on 10 of 13 farms and in all farm elements except for milk filters. Salmonella enterica and C. jejuni were detected at lower frequencies and were not identified in soil, stream water, or milk filters on any of the 13 farms. Cryptosporidium parvum was detected in feces but not in stored manure. Stored manure had the highest occurrence of pathogens (73%), followed by feces (50%), milk filters, bedding, soil, and water (range from 23 to 31%). Association of pathogen presence with farm management factors was examined by t-test; however, the small number of study farms and samples may limit the scope of inference of the associations. Pathogens had a higher prevalence in maternity pen bedding than in calf bedding, but total pathogen occurrence did not differ in calf compared with lactating cow feces or in soils with or without manure incorporation. Herd size and animal density did not appear to have a consistent effect on pathogen occurrence. The extent of pathogen prevalence and distribution on the farms indicates considerable public health risks associated with not only milk and meat consumption and direct animal contact, but also potential dissemination of the pathogens into the agroecosystem.

Survival characteristics of Salmonella enterica serovar Newport in the dairy farm environment.

Multi-drug resistant (MDR) Salmonella enterica serovar Newport (S. Newport) has established a reservoir in dairy cattle. Infected herds suffer significant mortality in both adult and young animals, posing a considerable economic loss to producers. Land application of manure from infected animals may further spread the pathogen into the agroecosystem, causing public health concerns. Previous work by our group demonstrated that the organism persisted in manure and manured soil for 6 to 10 mo under laboratory conditions. In the present study, we determined the survival characteristics of MDR S. Newport in a dairy lagoon, compost pile, and soil of a grass field under natural conditions using environmental sentinel chambers with an initial concentration of S. Newport around 7 log(10) per gram. In the static compost pile at 64 °C, S. Newport was eliminated within 18 h. In the dairy effluent lagoon, the pathogen survived for >137 d, whereas in the field soil, the organisms persisted for over 276 d. The survival of MDR S. Newport in both the lagoon and field soil followed a pattern of (1) an increase or plateau for a few days, (2) log-linear decline for 6 to 13 wk, and (3) a long tailing phase at low and variable concentration for 4 to 9 mo. Log reduction times (days required for 90% decrease in concentration) based on the log-linear decline phase were 7 d in the lagoon and 14 to 20 d in the soil. Conditions leading to faster inactivation during the initial phase do not necessarily translate into a quicker elimination of the pathogen. Regression models of the log-linear phase may be inaccurate for estimating complete pathogen elimination.

A fecal test for assessing phosphorus overfeeding on dairy farms: evaluation using extensive farm data.

Managing P on dairy farms requires the assessment and monitoring of P status of the animals so that potential overfeeding may be minimized. Numerous published studies have demonstrated that for lactating dairy cows, increasing P concentrations in diets led to greater P excretion in feces. More recent work reported that inorganic P (P(i)) in 0.1% HCl extracts of feces (fecal extract P(i), g/kg) closely reflects dietary P changes. This has led to the proposal that 0.1% HCl fecal extract P(i) may serve as an indicator of the animal's P status (adequate or excessive) when compared with a benchmark value. Here, we present the results of an extensive evaluation of the proposed fecal P indicator test. With samples (n=575) from >90 farms, fecal total P (TP, g/kg) and fecal extract P were positively correlated with dietary P (X, g/kg): TP=1.92X - 0.17 (R2=0.36); fecal extract P=1.82X - 2.54 (R2=0.46). Fecal extract P was responsive to dietary P changes, whereas the remaining P, calculated as TP minus fecal extract P, was not. A provisional benchmark value of fecal extract P representing near-adequate P status was set at 4.75g/kg. Assessment of the farm data using the benchmark indicated that 316 out of 575 data points were associated with possible P overfeeding. Advantages of the fecal-based test over feed-based analysis to assess P status are discussed. The fecal extract P method is a simple and practical test that can be used as an assessment tool for helping dairy producers improve P management and reduce their environmental footprint.

A comparison of phosphorus speciation and potential bioavailability in feed and feces of different dairy herds using 31p nuclear magnetic resonance spectroscopy.

An experiment was conducted to examine how potential phosphorus (P) bioavailability (inferred from speciation) differs in feed and feces collected in spring from four dairy herds representing different management systems: (i) total confinement with cows fed total mixed ration (TMR), (ii) total confinement with TMR plus P mineral supplement, (iii) a hybrid of confinement with TMR and pastoral grazing, and (iv) predominantly grazing with supplemental grains. A treatment was included that air dried feces to simulate conditions after dung deposition. Wet chemical techniques and solution (31)P nuclear magnetic resonance spectroscopy ((31)P-NMR) were used to identify P concentrations and compounds present in water (a surrogate for P in overland flow), dilute acid (0.012 M HCl, an estimate of P utilization by cattle), or NaOH-EDTA (a solution that maximizes the organic P extraction) extracts of feed and feces. In general, P concentration in feces paralleled P in feed. Air drying feces decreased water-extractable P by 13 to 61% largely due to a decrease in orthophosphate, whereas NaOH-EDTA-extractable P increased by 18 to 48%. Analysis of dilute HCl was unsuccessful due to orthophosphate precipitation when pH was adjusted to 12 for (31)P-NMR. In water extracts, more P was in bioavailable diester-P forms, undetectable by colorimetry, than in NaOH-EDTA extracts. In feed, orthophosphate dominated (46-70%), but myo-IHP varied with feed (<10% in forage samples but 43% in a TMR sample). The proportion of myo-IHP decreased in feces compared with feed via mineralization but decreased less in systems with a greater proportion of available P input (e.g., orthophosphate and phospholipids). Feed and drying effect the concentrations and forms of P in feces and their potential impact on soil and water quality. Although bioavailable P in feces from pasture-based and confined systems can be similar in spring, dung-P is distributed on a lower kg P ha(-1) rate in grazing systems. The best method to mitigate P loss from feces is to decrease P in feed.

Evaluation of free-stall mattress bedding treatments to reduce mastitis bacterial growth.

Bacterial counts were compared in free-stall mattresses and teat ends exposed to 5 treatments in a factorial study design on 1 dairy farm. Mattresses in five 30-cow groups were subjected to 1 of 5 bedding treatments every other day: 0.5 kg of hydrated limestone, 120 mL of commercial acidic conditioner, 1 kg of coal fly ash, 1 kg of kiln-dried wood shavings, and control (no bedding). Counts of coliforms, Klebsiella spp., Escherichia coli, and Streptococcus spp. were lowest on mattresses bedded with lime. Mattresses bedded with the commercial acidic conditioner had the next lowest counts for coliforms, Klebsiella spp., and Streptococcus spp. Wood shavings and the no-bedding control had the highest counts for coliform and Klebsiella spp. Compared with wood shavings or control, fly ash reduced the counts of coliforms, whereas for the other 3 bacterial groups, the reduction was not always significant. Streptococcus spp. counts were greatest in the control group and did not differ among the shavings and fly ash groups. Teat swab results indicated that hydrated lime was the only bedding treatment that significantly decreased the counts of both coliforms and Klebsiella spp. There were no differences in Streptococcus spp. numbers on the teats between any of the bedding treatments. Bacterial populations grew steadily on mattresses and were generally higher at 36 to 48 h than at 12 to 24 h, whereas bacterial populations on teats grew rapidly by 12 h and then remained constant. Hydrated lime was the only treatment that significantly reduced bacterial counts on both mattresses and teat ends, but it caused some skin irritation.

Use of flyash as environmental and agronomic amendments.

Coal combustion power plant flyash materials have been reported as useful soil amendments with agronomic and environmental benefits. This paper reports the efficacy of fluidized bed combustion (FBC) and flue gas desulfurization (FGD) byproducts, when amended with dairy, swine, and broiler litter manures, in reducing phosphorus (P) solubility and potential impact on water quality. At a rate of 400 g/kg, FBC reduced water soluble P by 60% for dairy and swine and 50% for broiler litter, as compared to un-treated control samples. Byproduct FGD had little effect when amended into dairy manure, but reduced water soluble P by nearly 80% when amended into swine and broiler manure at a rate of 250 g/kg. The amount of Ca added in the amendments together with pH of the mixture is the major contributing factor in soluble P reduction. Sequential extraction results showed that the flyash treatments shifted water soluble P into mainly bicarbonate extractable P. The latter is still considered available for crop uptake but less vulnerable for environmental losses. Coal combustion byproducts, when amended into manure and used properly, can provide a useful and viable option for improving nutrient management on animal farms.

Phosphorus feeding levels and critical control points on dairy farms.

A viable and cost-effective approach to managing P on dairy farms is to minimize excess P in diets, which in turn leads to less excretion of P in manure without impairing animal performance. A questionnaire survey was conducted, coupled with on-site feed and fecal sample collection and analysis on dairy farms in New York, Pennsylvania, Delaware, Maryland, and Virginia. The purpose was to assess dietary P levels and to identify critical control points pertaining to P feeding management. Survey responses, 612 out of 2500 randomly selected farms, revealed a wide range of dietary P concentrations for lactating cows, from 3.6 to 7.0 g/kg of feed DM. The mean was 4.4 g/kg, which was 34% above the level recommended by the NRC for 27.9 kg milk/d, the mean milk yield in the survey. Higher P concentrations in diets were not associated with higher milk yields (n = 98, R2 = 0.057 for the survey farms; n = 92, R2 = 0.043 for farms selected for on-site sampling). However, higher dietary P led to higher P excretion in feces (n = 75, R2 = 0.429), with much of the increased fecal P being water soluble. Phosphorus concentrations in diet samples matched closely with P concentrations in formulated rations, with 67% of the feed samples deviating <10% from the formulations. On 84% of the survey farms, ration formulation was provided by professionals rather than producers themselves. Most producers were feeding more P than cows needed because it was recommended in the rations by these consultants. In conclusion, P fed to lactating cows averaged 34% above NRC recommendations; to reduce excess dietary P, ration formulation is the critical control point.

Efficacy of alum and coal combustion by-products in stabilizing manure phosphorus.

Animal manures contain large amounts of soluble phosphorus (P), which is prone to runoff losses when manure is surface-applied. Here we report the efficacy of alum and three coal combustion by-products in reducing P solubility when added to dairy, swine, or broiler litter manures in a laboratory incubation study. Compared with unamended controls, alum effectively reduced readily soluble P, determined in water extracts of moist manure samples with 1 h of shaking, for all three manures. The reduction ranged from 80 to 99% at treatment rates of 100 to 250 g alum kg(-1) manure dry matter. The fluidized bed combustion fly ash (FBC) reduced readily soluble P by 50 to 60% at a rate of 400 g kg(-1) for all three manures. Flue gas desulfurization by-product (FGD) reduced readily soluble P by nearly 80% when added to swine manure and broiler litter at 150 and 250 g kg(-1). Another by-product, anthracite refuse fly ash (ANT), was ineffective for all three manures. In all cases, reduction in readily soluble P is primarily associated with inorganic phosphorus (P(i)) with little change in organic phosphorus (P(o)). Sequential extraction results indicate that the by-product treatments shifted manure P from H2O-P into a less vulnerable fraction, NaHCO3 - P, while the alum treatment shifted the P into even more stable forms, mostly NaOH-P. Such shifts in P fractions would have little influence on P availability for crops over the long-term but would retard and reduce potential losses of P following manure applications.

Manure sampling for nutrient analysis: variability and sampling efficacy.

Reliable estimation of nutrient concentrations is required to manage animal manure for protecting waters while sustaining crop production. This study was conducted to investigate sample variability and reliable nutrient analysis for several manure types and handling systems. Serial samples were collected from dairy, swine, and broiler poultry operations while manure was being loaded onto hauler tanks or spreaders for field application. Samples were analyzed for total solids (TS), total nitrogen (N), ammoniacal nitrogen (NH4-N), total phosphorus (P), and potassium (K). The least number of samples needed for reliable testing of total N and P, defined as +/- 10% of the experimental means with 99% probability, was obtained for each farm using a computer-intensive random resampling technique. Sample variability within farms, expressed as the coefficient of variation (CV), was mostly 6 to 8% for farms that used agitation of manure storages but several times higher (20-30%) on farms where no agitation was applied during the sampling period. Results from the random resampling procedure indicated that for farms that used agitation, three to five samples were adequate for a representative composite for reliable testing of total N and P; whereas for farms without agitation, at least 40 samples would be required. Data also suggest that using book values for manure nutrient estimations could be problematic because the discrepancies between book standards and measured farm data varied widely from a small amount to several fold.

Nitrogen fertilizer rate and crop management effects on nitrate leaching from an agricultural field in central Pennsylvania.

Eighteen pan lysimeters were installed at a depth of 1.2 m in a Hagerstown silt loam soil in a corn field in central Pennsylvania in 1988. In 1995, wick lysimeters were also installed at 1.2 m depth in the same access pits. Treatments have included N fertilizer rates, use of manure, crop rotation (continuous corn, corn-soybean, alfalfa-corn), and tillage (chisel plow-disk, no-till). The leachate data were used to evaluate a number of nitrate leaching models. Some of the highlights of the 11 years of results include the following: 1) growing corn without organic N inputs at the economic optimum N rate (EON) resulted in NO3--N concentrations of 15 to 20 mg l(-1) in leachate; 2) use of manure or previous alfalfa crop as partial source of N also resulted in 15 to 20 mg l(-1) of NO3--N in leachate below corn at EON; 3) NO3--N concentration in leachate below alfalfa was approximately 4 mg l(-1); 4) NO3--N concentration in leachate below soybeans following corn was influenced by fertilizer N rate applied to corn; 5) the mass of NO3--N leached below corn at the EON rate averaged 90 kg N ha(-1) (approx. 40% of fertilizer N applied at EON); 6) wick lysimeters collected approximately 100% of leachate vs. 40-50% collected by pan lysimeters. Coefficients of variation of the collected leachate volumes for both lysimeter types were similar; 7) tillage did not markedly affect nitrate leaching losses; 8) tested leaching models could accurately predict leachate volumes and could be calibrated to match nitrate leaching losses in calibration years, but only one model (SOILN) accurately predicted nitrate leaching losses in the majority of validation treatment years. Apparent problems with tested models: there was difficulty estimating sizes of organic N pools and their transformation rates, and the models either did not include a macropore flow component or did not handle macropore flow well.