Abstract:
An apparatus and corresponding method obtains time-integrated samples of fluid from the rumens of cattle, sheep, goats or other animals through a cannula. The apparatus allows ruminal fluid to be sampled under standard conditions. It reduces the labor required to obtain samples and allows dynamic fermentation patterns to be followed. The apparatus includes a ceramic filter connected to a sampling tube assembly. The filter is placed in the rumen and vented to atmosphere by a first tube. A second tube connects an inside region of the filter to a peristaltic pump which removes fluid for time-integrated sampling.

Description:
This patent application claims the benefit of provisional application U.S. Ser. No. 60/138,907 filed Jun. 11, 1999. 
    
    
     The invention was made with Government support and the Government has certain rights in the invention. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The invention relates to fluid sampling in living creatures. Particularly, the invention relates to sampling of fluid from the rumens of cattle, sheep, or goats. 
     BACKGROUND OF THE INVENTION 
     Unlike nonruminants (e.g., horses, poultry and swine), ruminants (e.g., cattle, goats and sheep) have a four-compartment stomach. The rumen is the largest compartment and functions as a large fermentation chamber, in which microbes produce volatile fatty acids. These are then absorbed and used by the animal for productive purposes (e.g., milk production and growth). The importance of volatile fatty acids to animal-productivity has resulted in the development of frequent and labor-intensive sampling methods for their determination. 
     Researchers, large feed companies, and some private laboratories devote considerable resources to measuring the effects of various feeds and feed treatments on ruminal fermentation. The pattern of fermentation in the rumen must be closely monitored using some sort of sampling apparatus to properly determine the nutritional value of diets. Fermentation in the rumen [e.g., the production of volatile fatty acids (acetic, propionic, butyric, and higher acids)] is a dynamic process and a major determinant of the efficiency of animal growth, milk production, and milk composition. 
     Ruminal sampling methods also are important in veterinary practice. These techniques are responsible for assisting in the diagnosis of digestive diseases and latent or clinical conditions affecting digestion and the well-being of the animal. A critical factor limiting our ability to gather data about ruminal fermentation has been the lack of appropriate sampling methods. 
     Several factors complicate ruminal sampling; however, most arise from the heterogeneous nature of the ruminal contents and the dynamics of the digestion process. A sample representative of the biological and biochemical environment of the rumen is best collected under standard conditions in relation to time of feeding and location in the rumen, preferably from the center or ventral ruminal sac. Ruminal fluid samples should also be taken over time to account for diurnal changes. 
     Conventional methods of collecting ruminal fluid may not produce representative samples in terms of quality and quantity, while methods able to provide representative samples are often impractical. The various approaches currently used to obtain samples of ruminal fluid are: 
     A. Slaughter 
     1. Description 
     Digesta fluid samples have been obtained at slaughter for many years [e.g., Ulyatt, M. J. et al. 1984. Effect of intake and feeding frequency behavior and quantitative aspects of digestion in sheep fed chaffed lucerne hay. J. Agr. Sci. (Camb.): 102:645]. The technique has proved most useful for sampling digesta fluid in wild animals, although occasionally it has been employed in agricultural studies. 
     2. Problems 
     a. The main disadvantage of sampling at slaughter is that only single samples are obtained. Rarely does such a sampling scheme fit into current experiments on valuable livestock or endangered animals. It has been used recently only in very intensive experiments with few animals. Even more rarely is it used with wild animals. 
     b. Standard technique also requires that feed be withheld from animals for some interval before slaughter. This artificial situation makes the samples obtained less valuable. Special arrangements have sometimes been made at slaughter to allow rapid sampling after exsanguination. 
     c. Digestion is dynamic; therefore, several samples should be collected over the day to adequately describe the process. This problem has been handled by slaughtering groups of animals at various times after feeding; however, it is obviously a costly and time-consuming approach. 
     B. Stomach Tube 
     1. Description 
     In this technique, digesta fluid samples are obtained by aspiration through a tube passed through a speculum in the mouth and via the esophagus to the reticulorumen of intact animals (e.g., Geishauser, T., and A. Gitzel. 1996. A comparison of rumen fluid sampled by ororuminal probe versus rumen fistula. Small Ruminant Res. 21:63; and Dirksen, G., and M. C. Smith. 1987. Acquisition and analysis of bovine rumen fluid. Bovine Pract. 22:108). 
     2. Problems 
     a. A major problem with this technique is that the fluid samples obtained are often contaminated with variable quantities of saliva and mucus. Some have tried to reduce the problem by discarding the first part of the sample obtained by aspiration. 
     b. The position of the sampling tube in the reticulorumen is unknown during sampling. The composition of spot samples from various locations in the reticulorumen often differs; therefore, it is unlikely that fluid samples via a stomach tube are representative of the overall environment in the reticulorumen. 
     This problem has been handled by focusing on differences between treatments so that the results obtained are not considered quantitative measures of the overall environment in the reticulorumen. 
     c. Animals must be disturbed and additional restraint applied to effectively sample with this method. This is especially problematic when repeated sampling is required. This problem has been handled by avoiding repeated sampling and developing skilled handlers who can obtain samples while minimizing disturbance of the animal. 
     d. Repeated sampling increases the labor required to obtain samples. This drawback has been recognized by all who have been involved in 24-hour sampling protocols. It is usually handled by enlisting groups of people to cooperate during sampling periods. 
     e. The sampling tube is often plugged when vacuum is applied because large digesta particles occlude the holes through which fluid would otherwise move. This problem occurs frequently and is usually overcome by sliding the sampling tube in and out to scrape off particles blocking the holes. 
     C. Naso-ruminal Sampler 
     1. Description 
     A naso-ruminal sampler obtains digesta fluid by aspiration through an indwelling tube passed through the nose and pharynx and then via the esophagus to the recitulorumen of intact animals [e.g., Poulsen, S. D. et al. 1988. Clinical chemical comparative examination or ruminal samples collected by means of a naso-ruminal sampler. Acta. Vet. Scand. 29:129; and Moloney, A. P. 1997. Comparison of procedures for the collection of rumen fluid from cattle. Irish J. Ag. Fd. Res. 36(Suppl. 1): 108 (Abstr.)]. 
     2. Problems 
     a. Naso-rumen samples of digesta fluid would not be representative of the overall environment of the reticulorumen, because fluid is obtained from a single but unknown location. As with the samples obtained using a stomach tube, the problem has been handled by focusing on differences between treatments so that the results obtained are not considered quantitative measures of the overall environment in the reticulorumen. 
     b. Animals must be disturbed and additional restraint applied to effectively sample with this method. This is especially problematic when repeated sampling is required. This problem has been handled by avoiding repeated sampling and developing skilled handlers who can obtain samples while minimizing disturbance of the animal. 
     c. Repeated sampling increases the labor required to obtain samples. This drawback has been recognized by all who have been involved in 24-hour sampling protocols. It is usually handled by enlisting groups of people to cooperated during sampling periods. 
     d. The sampling tube is often plugged when vacuum is applied because large digesta particles occlude the holes through which fluid would otherwise move. This problem occurs frequently and is usually overcome by sliding the sampling tube in and out to scrape off particles blocking the holes. 
     D. Spot Sampler 
     1. Description 
     This technique utilizes an evacuated flask to obtain composite samples of digesta fluid from several sites via a perforated tube in cannulated animals (e.g., Woodford, S. T., and M. R. Murphy. 1988. Dietary alteration of particle breakdown and passage from the rumen in lactating diary cattle. J. Dairy Sci. 71:687). This method is the most common currently employed. A ruminally cannulated animal is required. 
     2. Problems 
     a. Frequent and labor-intensive sampling is required to adequately describe the dynamics of digestion. This drawback has been recognized by all who have been involved in 24-hour sampling protocols. It is usually handled by enlisting groups of people to cooperate during sampling periods. 
     b. Repeated removal and replacement of the cannula cover disturbs the animal and may allow digesta to escape. This seems to be an unaddressed problem with the spot-sampling method. 
     c. The sampling tube is often plugged when the vacuum is applied because large digesta particles plug the holes through which fluid would otherwise move. This problem occurs frequently and is usually overcome by sliding the sampling tube in and out to scrape off the particles blocking the holes. 
     E. Rumenocentesis 
     1. Description 
     Herd health is sometimes monitored by sampling digesta fluid from the outside of selected intact animals using a needle attached to a syringe to penetrate the reticulorumen (e.g., Nordlund, K. V., and E. F. Garrett 1994. Rumenocentesis: a technique for collecting rumen fluid for the diagnosis of subacute rumen acidosis in diary herds. Bovine Pract. 28:109). The technique is usually employed to determine the pH of digesta in the reticulorumen. A low pH is interpreted to indicate the possible presence of acidosis or subclinical acidosis. 
     2. Problems 
     a. Animals must be disturbed and additional restraint applied to effectively sample with this method. It is also problematic when repeated sampling is required. This problem seems unavoidable when rumenocentesis is employed. Animal health and welfare concerns would seem to preclude repeated sampling with this method. 
     b. A small sample volume (1 to 3 ml) is obtained. This problem limits the analyses that can be conducted and, as a spot sample, is not representative of the overall ruminal environment. The proposed method allows collection of about 55 ml per hour, an adequate but not excessive sampling rate. 
     c. There is potential for inflammatory reaction at site of needle entry. Pathogen entry is always a risk in surgical procedures and aseptic methods are recommended for rumenocentesis. 
     d. At best, this technique (as currently employed) is of questionable value in describing the dynamics of digestion. Use of rumenocentesis to sample digesta fluids and interpretation of its results is currently a controversial topic in ruminant nutrition and veterinary medicine. 
     SUMMARY OF THE INVENTION 
     The invention provides an apparatus and method for sampling body fluids from an animal body, including from humans, using a filter to be inserted into the body and a first tube venting the filter to atmosphere and a second tube extending from inside the filter to outside the animal body. A pump draws sampled fluid which collects inside the filter, to a collection vessel. 
     This invention includes an apparatus and method that allows time-integrated and representative samples of ruminal fluid to be obtained with less error and labor. The apparatus includes a cup shaped ceramic filter located within the rumen of the animal. The filter is vented to remain at atmospheric pressure. A draw tube removes fluid which flows into the filter via a peristaltic pump. 
     The time-integrated sampler can comprise a small cup-shaped ceramic filter, two outer tube lengths connected at an angle, one inner flexible tube and one outer flexible tube, a ruminal cannula cover, and a peristaltic pump. The filter connects to the outer flexible tube via a clamp. The neck of the filter can extend close to the end of the outer tube lengths. The outer flexible tube is tethered outside the rumen to prevent it from being moved during ruminal contractions. The outer tube lengths extend from the filter through the cannula cover or plug and maintain the filter in the ventral rumen while securing the outer flexible tube. Thus, the filter is inserted into the ventral rumen by closing or replacing the cannula cover. This allows the filter to be easily removed for cleaning and inspection. 
     The inner flexible tube, through which filtrate entering the filter is removed continuously, travels from the inside base of the filter through the outer flexible tube and, via a peristaltic pump, into a collection vessel. The inner flexible tube can be kept in place using small clamps inside the outer flexible tube. It is important to note that the peristaltic pump is not responsible for the flow of fluid into the filter but for removing fluid that passively enters the filter. Ruminal fluid flows into the filter due to the natural pressure gradient existing in the ventral rumen and not because of an external source of vacuum. 
     A time-integrated, therefore, representative sample relying on natural mixing contractions is achieved. Repeated sampling is possible, therefore the diurnal dynamics of fermentation can be followed. Fixed, known, optimal sampling position is achieved. The sampling rate is adequate to support varied and repeated chemical analyses, but not so fast that the dynamics of ruminal fermentation are adversely affected. 
     Reduced sample processing is achieved. Most particles are removed as fluid seeps into the filter with 6-μm pores; therefore, the usual filtering step is avoided saving materials and labor. Reduced or eliminated clogging of the tube during sampling is achieved. Manipulation of the device is not required to obtain continuous or repeated samples. 
     The device and method are adaptable to automatic sampling. By coupling the peristaltic pump to a fraction collector, composite samples integrated over arbitrary time periods could be obtained automatically. This provides a significant labor savings. The device and method are adaptable to ambulatory or remote sampling. Ambulatory and remote sampling of ruminal fluid would be valuable in situations in which animals are not confined, e.g., grazing. 
     The method provides a labor savings. The device has a relatively simple construction. 
     A small dead volume allows rapid stopping of fermentation and less exposure to air than all techniques, except rumenocentesis. 
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a sampling system of the present invention; 
     FIG. 2 is a schematic view of a prior art sampling system; 
     FIG. 3 is a perspective view of the apparatus of the present invention; and 
     FIG. 4 is a sectional view of a portion of the apparatus of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawing and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     FIG. 1 illustrates a time-integrated sampler  10  that comprises a small cup-shaped ceramic filter  12  (such as manufactured by Soil Moisture Equipment Corp., Santa Barbara, Calif.), two outer tube lengths  14 ,  16  (polyvinyl chloride (PVC), preferably 50 cm long with a diameter of 2 cm) connected at an angle, one inner flexible tube  18  (preferably plastic) and one outer flexible tube  20  (preferably plastic), a ruminal cannula cover  28  and a peristaltic pump  32  (such as manufactured by Rabbit, Rainin Instrument Co., Woburn, Mass.). The filter  12  connects to the outer flexible tube  20  via a clamp (not shown). A neck  12   a  of the filter  12  can extend close to the end of the outer tube length  14 . The outer flexible tube  20  is tethered outside the rumen to prevent it from being moved during rumimal contractions. The outer tube lengths  14 ,  16  extend from the filter through the cannula cover and maintains the filter in the ventral rumen while securing the outer flexible tube  20 . Thus, the filter can be inserted into the ventral rumen by closing or replacing the cannula cover  28 . This allows the filter to be easily installed and removed for cleaning and inspection. 
     The inner flexible tube  18 , through which filtrate entering the filter is removed continuously, extends from the inside base  12   b  of the filter  12  through the outer flexible tube  20  and via the peristaltic pump  32  into a collection vessel  40 . The inner flexible tube  18  can be kept in place using small clamps (not shown) inside the outer flexible tube  20 . 
     It is important to note that the peristaltic pump  32  is not responsible for the flow of fluid into the filter but for removing fluid that passively enters the filter. Ruminal fluid flows into the filter  12  due to the natural pressure gradient existing in the ventral rumen and not because of an external source of vacuum. 
     FIG. 3 illustrates a preferred embodiment sampling device  100 . The sampling device includes a cup-shaped ceramic filter  106  which is connected to an outer flexible tube  108 , preferably plastic, via a screw activated clamp  110 . An outer sleeve  114 , preferably a PVC tube, surrounds the outer flexible tube  108 . The sleeve  114  is connected to a 45° elbow  120  by a coupling  122 . The elbow  120  is connected to a further coupling  123  which connects a short straight section  119  to a further coupling  125 . The couplings  123 ,  125  capture a cannula plug  130  therebetween, to fix the cannula plug or cover  130  onto the short straight section  119 . 
     The outer flexible tube  108  extends from an open end  134 , through the coupling  125 , through the short straight section  119 , through the coupling  123 , through the elbow  120 , through the coupling  122 , through the sleeve  114 , through a coupling  116 , to the clamp  110 , to be connected to the ceramic filter  106 . The ceramic filter is thus vented to atmospheric pressure through the outer flexible tube  108  which extends outside the rumen through the cannula plug  130 . Inserted through the outer flexible tube  108 , is an inner flexible tube  126 , preferably plastic, which extends through the open end  134  of the outer flexible tube  108  to the ceramic filter  106 . The inner flexible tube  126 , as shown schematically in FIG. 1, extends into the ceramic filter and has a hole or open end  126   a  (FIG. 4) therein to receive fluid from the rumen. The opposite end  140  of the inner flexible tube  126  is connected to a peristaltic pump as described in FIG.  1 . 
     FIG. 4 illustrates the outer flexible tube  108  clamped to an outlet neck  107  of the filter  106 . The neck  107  is sized such that the outer flexible tube  108  is bulged or flared outwardly at an end  108   a , around the neck  107 . The neck  107  of the filter preferably has an outer diameter of 13 mm and an inner diameter of 8 mm. The size of the bulged end  108   a  is about the size of an open end  116   a  of the coupling  116 . Thus, the bulged end  108   a  when drawn against the end  116   a , substantially closes the open end  116   a  to help keep matter out of the coupling  116  and the outer PVC sleeve  114 . The inner flexible tube  126  inserts through the outer flexible tube  108  and into the filter  106 . The inner flexible tube  126  is centered in position to the filter  106  at the neck  107  by a tubular fitting or insert  150 , preferably plastic, having a tapered insertion end  152 . The fitting has an outside diameter of 10 mm and an inside diameter of 6 mm. The fitting  150  is sized to be sufficiently loose between the outside diameter of the inner flexible tube  126  and the inside diameter of the fitting  150  to allow free flow of air past the fitting  150 , through the outer flexible tube  108 . 
     In a preliminary study, the rates at which water passively entered two cup-shaped porous ceramic filters (such as manufactured by Soil Moisture Equipment Corp., Santa Barbara, Calif.) vented to the atmosphere were evaluated. A filter was desired which allowed about 5 ml of water to enter per minute to ensure that water could be removed from inside the filter faster than its entry rate into the filter. Therefore, the speed of an in-line peristaltic pump was adjusted to keep air entering a sampling tube placed in the filter. The larger filter had a diameter of 4 cm, a length of 19 cm, a wall thickness of 0.5 cm, and a pore size of 6 μm (Soil Moisture Equipment Corp, part number 652X18-B.5M2). The smaller filter measured 2.2 cm in diameter, 6 cm in length, had a wall thickness of 0.2 cm and a pore size of 6 μm (Soil Moisture Equipment Corp. part number 655X01-B.5M2). Both filters had a saturated hydraulic conductivity of 3.11×10 −5  cm/sec. It was concluded from the preliminary study that the smaller filter was more appropriate because water entered the larger filter more quickly than desired. 
     In the first study, a ruminally cannulated lactating Holstein cow receiving ad libitum access to a totally mixed ration (TMR) fed twice daily and consisting of corn silage, alfalfa haylage, and a ground corn and soybean meal-based concentrate mixture (25:25:50 on a DM basis) was used. The time-integrated sampler was placed in the ventral rumen of the cow for two 36-h (with 6-h collection intervals) periods to determine the rate of ruminal fluid uptake and, in the process, the susceptibility of the filter to clogging. During this period observations were also made concerning ruminal fluid uptake during standing and lying, and to ensure that the device did not interfere with normal ruminal contractions. 
     In a second study, two non-lactating Holstein cows (fitted with permanent ruminal cannulas) given ad libitum access to the same TMR fed in the first study once daily were used in a split-plot design to determine the utility of the time-integrated device for obtaining ruminal fluid samples representative of the dynamic fermentation environment. Sampling was evaluated by comparing the volatile fatty acid concentrations in ruminal fluid collected by the time-integrated device with that collected using the conventional suction-strainer device. Ruminal fluid sampled by both methods was collected in four 8-h studies starting either 2 h before or 6 h after feeding. Samples were collected continuously at 1-h intervals by the time-integrated method while sampling occurred every 30 min using the suction-strainer device. The 30-min collection interval used for the suction-strainer device was necessary to determine if the time-integrated sampler provided an accurate estimate of the overall ruminal fermentation environment with respect to time. 
     Immediately following collection, all suction-stainer samples were placed in ice water to stop fermentation, mixed, and subsampled (50 ml) for pH and volatile fatty acids analysis. Ruminal fluid collected by the time-integrated sampler was acidified with 15 ml of 25%-metaphosphoric acid as it entered the collection vessel. The collection vessel was stored in ice water. Subsamples (50 ml) from the suction-strainer device were stabilized by the addition of 15 ml of 25%-metaphosphoric acid. All samples were filtered through four layers of cheesecloth, and centrifuged for 20 min at 20,000×g and −15° C. The supernatant was transferred to two 1.5-ml micro-centrifuge tubes and frozen overnight at −20° C. to precipitate soluble protein. Samples were then thawed to room temperature and centrifuged again (20 min at 20,000×g and −15° C.). Volatile fatty acid concentrations in the supernatants were determined using a Vista 44 gas liquid chromatograph (Varian, Walnut Creet, Calif.) and 2-ethyl butyric acid as an internal standard. 
     Methods were compared using analysis of variance for a split-plot design. The model included the effects of study, method, time, method by time interaction, and study by method interaction as the error term for method. If a significant (P&lt;0.05) F value was indicated for a main effect, then comparisons were made using Tukey&#39;s Test to detect differences among methods. 
     The rate of ruminal fluid uptake by the time-integrated sampler averaged 0.359±0.006 ml/min over the two 36-h periods and was unaffected (P&gt;0.05) by time. Sampling occurred while the animal was standing and lying down. There were no visible signs of discomfort or any indication that ruminal contractions were altered. The consistency of uptake observed for the method indicated that the time-integrated sampler was not susceptible to clogging during this time period and that position of the animal (lying or standing) did not influence uptake. 
     Total ruminal fluid volatile fatty acid concentrations in samples collected using the time-integrated sampler did not differ (P&gt;0.05) from those gathered using the suction-strainer device (Table 1). Molar percentage of propionate, isobutyrate, butyrate, isovalerate, and valerate in samples that began collection 2 h before feeding were similar (P&gt;0.05) between methods, but acetate was 2.5% higher (P&lt;0.05) in samples collected by the suction-strainer device (Table 2). Molar percentages of acetate, propionate, isobutyrte, butyrate, and isovalerate in samples that began collection 6 h post-feeding were similarly unaffected (P&gt;0.05) by method except valerate, which was 5% higher (P&lt;0.05) in samples collected by the suction-strainer device. Although significant, the small differences are not considered physiologically important and may represent a type I error arising because of the many comparisons made. 
     Although already in usable form, the device could be further developed to allow sampling under ambulatory conditions. 
     The device could possibly be adapted for use in human and in veterinary medicine to obtain larger fluid samples from the gastrointestinal tract via endoscopy. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Total volatile fatty acid concentrations 
               
             
          
           
               
                   
                 Method 
                 2 h Before feeding a   
                 6 h Post-feeding a   
               
               
                   
                   
               
             
          
           
               
                   
                 Suction-strainer 
                 79.3 
                 78.1 
               
               
                   
                 device, mM 
               
               
                   
                 Time-integrated 
                 74.0 
                 73.0 
               
               
                   
                 device, mM 
               
               
                   
                 SEM b   
                 13.3 
                 5.7 
               
               
                   
                   
               
               
                   
                   a Period starting time.  
               
               
                   
                   b Pooled standard error of the means estimated across time within an 8-h study.  
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Volatile fatty acid pattern (moles/100 moles) 
               
             
          
           
               
                 Method 
                 Acetate 
                 Propionate 
                 Isobutyrate 
                 Butyrate 
                 Isovalerate 
                 Valerate 
               
               
                   
               
               
                 Period starting 
                   
                   
                   
                   
                   
                   
               
               
                 2 h before feeding 
               
               
                 Suction- 
                 65.4 a   
                 18.7 a   
                 1.3 a   
                 11.5 a   
                 1.6 a   
                 1.5 a   
               
               
                 strainer device 
               
               
                 Time- 
                 63.8 b   
                 19.9 a   
                 1.4 a   
                 11.8 a   
                 1.7 a   
                 1.4 a   
               
               
                 integrated device 
               
               
                 SEM c   
                  .9 
                  .5 
                  .3 
                  .4 
                  .3 
                  .2 
               
               
                 Period starting 
               
               
                 6 h Post-feeding 
               
               
                 Suction- 
                 62.6 a   
                 19.0 a   
                 1.2 a   
                 13.7 a   
                 1.9 a   
                 1.6 a   
               
               
                 strainer device 
               
               
                 Time- 
                 62.1 a   
                 19.1 a   
                 1.3 a   
                 14.1 a   
                 1.9 a   
                 1.5 b   
               
               
                 integrated device 
               
               
                 SEM c   
                  .4 
                  .4 
                  .1 
                  .4 
                  .1 
                  .2 
               
               
                   
               
               
                   a,b Means in the same column and sampling period with different superscripts differ (P &lt; .05).  
               
               
                   c Pooled standard error of the means estimated across time within an 8-h study.