Adapting sanitary inspections for the monitoring of small drinking water supplies in Iceland.

Sanitary inspections (SIs) are checklists of questions used to identify actual and potential sources and pathways of drinking water contamination. Though the importance of SI adaptation to local contexts is widely acknowledged, there is currently limited guidance on how this should be undertaken in practice. During this research, World Health Organization (WHO) draft template SI forms for spring and borehole supplies were adapted for use in Iceland based on a series of desk reviews and field tests, an approach which may guide other future SI adaptation processes. SI results were collected from 25 spring supplies and nine borehole supplies in three regions of Iceland using adapted SI forms. These results were combined with 10-year historical water quality data from the same supplies to explore potential relationships between both data sets. Binary logistic regression test results indicated a statistically significant association (P = 0.025; odds ratio (OR) 1.864, 95% CI 1.080-3.220) between SI Question 3 (Does ponding from surface water occur around the spring/borehole?) receiving a 'High' risk level assignment and at least one historical incidence of water quality noncompliance for the parameters heterotrophic plate count 22 °C, total coliforms, Escherichia coli, and turbidity at the same supply. The significant modifications applied to the starting template during the testing and development of the Icelandic SI form emphasises the importance of a robust adaptation process to ensure SI forms are appropriate for the local context. Results from the analysis of SI and water quality test results demonstrated the potential for these data sets to identify the primary risks at a supply. This information may then be used to direct remedial actions, especially when the amount of relevant data increases over time.

Temporal drivers of tryptophan-like fluorescent dissolved organic matter along a river continuum.

Tryptophan-like fluorescence (TLF) is used to indicate anthropogenic inputs of dissolved organic matter (DOM), typically from wastewater, in rivers. We hypothesised that other sources of DOM, such as groundwater and planktonic microbial biomass can also be important drivers of riverine TLF dynamics. We sampled 19 contrasting sites of the River Thames, UK, and its tributaries. Multivariate mixed linear models were developed for each site using 15 months of weekly water quality observations and with predictor variables selected according to the statistical significance of their linear relationship with TLF following a stepwise procedure. The variables considered for inclusion in the models were potassium (wastewater indicator), nitrate (groundwater indicator), chlorophyll-a (phytoplankton biomass), and Total bacterial Cells Counts (TCC) by flow cytometry. The wastewater indicator was included in the model of TLF at 89 % of sites. Groundwater was included in 53 % of models, particularly those with higher baseflow indices (0.50-0.86). At these sites, groundwater acted as a negative control on TLF, diluting other potential sources. Additionally, TCC was included positively in the models of six (32 %) sites. The models on the Thames itself using TCC were more rural sites with lower sewage inputs. Phytoplankton biomass (Chlorophyll-a) was only used in two (11 %) site models, despite the seasonal phytoplankton blooms. It is also notable that, the wastewater indicator did not always have the strongest evidence for inclusion in the models. For example, there was stronger evidence for the inclusion of groundwater and TCC than wastewater in 32 % and 5 % of catchments, respectively. Our study underscores the complex interplay of wastewater, groundwater, and planktonic microbes, driving riverine TLF dynamics, with their influence determined by site characteristics.

Ascophyllum nodosum supplementation: a preharvest intervention for reducing Escherichia coli O157:H7 and Salmonella spp. in feedlot steers.

Ascophyllum nodosum (Tasco-14) decreased the prevalence of enterohemorrhagic Escherichia coli (EHEC) O157:H7 in animals fed prior to harvest. Tasco-14 was supplemented on a 2% dry matter basis 14 days prior to harvest to determine its effects on EHEC and Salmonella spp. prevalence. Two hundred mixed crossbred steers and heifers (Bos indicus x Bos taurus), in a large commercial finishing facility, served as experimental units. Treatment (TRT, n = 100) animals received a steam-rolled corn-based diet containing 2% Tasco-14 on a dry matter basis, and control (CON, n = 100) animals received only the steam-rolled corn-based diet. Hide swabs and fecal samples were obtained for EHEC and Salmonella spp. evaluations. Animals were sampled 1 day prior to (d - 1) the feeding of Tasco-14 and immediately following exsanguinations. The prevalence of EHEC O157 on hide swabs and in fecal samples (P = 0.0001 and P < 0.0001, respectively) and the prevalence of EHEC O157:H7 on hide swabs and in fecal samples (P < 0.0001 and P < 0.0001, respectively) was reduced by 33 and 36% from d - 1 levels on TRT hide swabs and by 9 and 11% in TRT fecal samples. The prevalence of EHEC O157 and EHEC O157:H7 was reduced by 33 and 36% from d - 1 levels on TRT hide swabs and by 9 and 11% in TRT fecal samples. The prevalence of Salmonella spp. on hide swabs did not change for TRT animals (P = 0.64). CON animals showed an increase in Salmonella spp. prevalence (P < 0.0001) from d - 1 feeding levels on hide swabs. The prevalence of Salmonella spp. increased in both TRT and CON fecal samples when compared to d - 1 levels (P = 0.002). However, TRT samples exhibited a lower (P < 0.05) postfeeding prevalence of Salmonella spp. in fecal samples than did CON samples. Results from this study indicate that 2% Tasco-14 supplementation in feedlot cattle diets reduces EHEC O157 and EHEC O157:H7 prevalence on hide swabs and in fecal samples and may suppress increases in Salmonella spp.

Voluntary intake, gain, digestibility, rate of passage and gastrointestinal tract fill in tropical and temperate breeds of sheep.

In trial 1, Coastal bermudagrass pellets were fed for 63 d to 21 growing rams of Barbados Blackbelly (B), Dorset (D) and Blackbelly X Dorset (B X D) breeding to determine the effect of breed on voluntary intake (VI) and total gain. Initially, each breed group consisted of seven rams with mean weights of 18.6, 31.0 and 26.4 kg, respectively. At the end of the intake and growth phase, digestibility, rate of passage and gastrointestinal tract (GIT) fill were determined. Chromium-mordanted fiber was used as a particle phase marker. Intakes during the digestibility-marker phase averaged 75% of the VI determined in the intake and growth phase. Breeds did not differ in VI, total gain or digestibilities of dry matter (DM) and neutral detergent fiber (NDF). Apparent crude protein (CP) digestibility was approximately 3 percentage units higher (P less than .10) for B X D than for B or D rams. Rate of passage was faster (P less than .05) for B X D rams than for the other breed groups, while D rams were intermediate. Total mean retention time (MRT) was shorter (P less than .05) for B X D rams compared with the other breed groups. Ruminal retention time (RRT) was shorter (P less than .05) and GIT fill was less (P less than .10) for D and B X D than for B rams. In trial 2, chopped orchardgrass-alfalfa hay was fed for 26 d to 19 of the same rams used in trial 1. Breed, number of rams and initial weights (kg) were: B, 5, 25.6; D, 7, 39.4; B X D, 7, 35.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of switching diets on growth and digesta kinetics of cattle.

An approach was developed for describing live weight gain and the contribution of wet gut fill gain to live weight gain in growing cattle. In a continuous growth study, energy densities of winter:spring diets were used to define four treatment groups of cattle. Concentrates and forages were the major ingredients of higher and lower energy-density diets, respectively. Cattle receiving high and low energy sequences (HH and LL) were designated as control groups and were compared with two change-over groups: high to low (HL) and low to high (LH). Switches involved simultaneous changes in several feed characteristics. Every 2 wk for 4 mo, 39 heifers and 19 steers were weighed. Switching young cattle to another diet affected growth during the 2 wk immediately after the switch. After being switched to the lower energy-density diet (i.e., pasture), HL and LL groups lost (P less than .001) from 3.5 to 27.4 kg in both fed and fasted weight. Neither fed nor fasted weights of HH and LH steers changed during the switch to the higher energy-density diet (i.e., concentrates); HH and LH heifers continued to gain (P less than .001). Throughout the remainder of the study, growth rates of cattle were similar for HH and LH groups and for HL and LL groups. In spring, cattle consuming concentrate diets (HH and LH) had greater fill (P less than .001) than pasture-fed contemporaries (HL and LL). Less frequent measurement of growth characteristics would have obscured important facets of growth. A loss of weight followed by continuous gain is not equivalent to a reduced growth rate.

Interrelationships among voluntary intake, eating and ruminating behavior and ruminal motility of heifers fed corn silage.

Six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) with ruminal, duodenal and ileal cannulae given ad libitum access to corn silage with or without 100 mg monensin X head-1 were used to determine interrelationships among behavior, ruminal motility and intake. Voluntary intake was positively related (P less than .001) to eating time, duration of the main morning meal and daily mastication time. Intake was negatively related to unitary times [min X g dry matter-1 X (kg body weight X 75)-1] of eating (P less than .05), rumination (P less than .001), mastication (P less than .001), unitary number of rumination boli (P less than .001), and latency time between termination of morning meal and onset of rumination (P less than .05). Both daily and unitary eating and ruminating time were positively related (P less than .001) to daily and unitary mastication time and unitary number of strong cranio-dorsal ruminal contractions. Positive relationships (P less than .01) were found between mean duration of daily meals, main evening meal and unitary eating time, and between mean duration of rumination periods and unitary ruminating time. Daily and unitary number of rumination boli and mean duration of one bolus were positively related (P less than .01) to unitary ruminating time. Interrelationships between intake, eating and ruminating activities and associated cranio-dorsal ruminal motility were all influenced (P less than .01) by individual heifer, which indicates potential in identifying individuals with better than average mastication behavior and ruminal motility.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in ruminal and fecal particle weight distribution of steers fed coastal bermudagrass hay at four levels.

Samples of digesta from the ruminal upper strata (RUS) and feces (F) were taken from four ruminally cannulated steers fed Coastal bermudagrass hay (78% NDF) in the long form to evaluate the effects of feeding level and time postfeeding on particle breakdown. The experimental design was a 4 x 4 Latin square with 18-d periods. Treatments based on previous intakes were set at 50, 70, 90 and 110% (3.1, 4.4, 5.5 and 6.7 kg/d, respectively) of feed consumed per animal and fed at 12-h intervals. Samples were taken at 2, 6 and 12h postfeeding and wet-sieved. Dry matter weight distribution of total recovered particles was used to partition RUS and F digesta among percentages of large (greater than 4.0 mm), medium (greater than 4.0 and less than or equal to 1.0 mm), small (less than 1.0 and greater than or eual to .125 mm) and fine (less than .125 and greater than or equal to .0027 mm) particles. With increasing feeding level, the percentage of medium RUS particles increased linearly (P less than .02), whereas the percentage of fine RUS particles decreased linearly (P less than .01). Increased time postfeeding resulted in a linear decrease in the percentage of large RUS particles (P less than .01), a linear increase in the percentage of small RUS particles (P less than .01) and in a quadratic increase in the percentage of fine RUS particles (P less than .01). Percentage of medium RUS particles remained unchanged. Increasing feeding level resulted in linear increases in mean RUS (P less than .01) and F (P less than .02) particle sizes. Percentages of RUS and F material passing through a 1.0-mm sieve averaged 52.8 and 88.8%, respectively. Animal-to-animal variation in proportions of RUS and mixed reticuloruminal particles was not entirely removed by rumination and was still reflected in the percentages of F particles. Factors such as particle entrapment in the fiber mat, reticular sedimentation, changes in specific gravity, swelling and hydration capacity, reticuloruminal motility and amount of digesta exiting per contraction appear to be more important than particle size reduction in the regulation of the passage of digesta from the reticulorumen.

Effects of mastication and microbial contamination on ruminal in situ forage disappearance.

In an experiment to determine the effects of mastication and microbial contamination on in situ forage disappearance, samples of masticated (M) or nonmasticated alfalfa hay (AH), orchardgrass hay (OGH) and bermudagrass hay (BGH) were incubated in the rumen of two steers for 6, 12, 24, 48 and 96 h. Using diaminopimelic acid as a marker, microbial DM and CP contamination ranged from 10.3 to 22.3% and 46.3 to 95.3% of residual DM and CP, respectively. Percentage contamination was influenced by both time of incubation and forage treatment (P less than .001). Corrected DM and CP disappearances (DMD and CPD) were higher than apparent disappearances (P less than .001). Maximal NDF and ADF disappearances (NDFD and ADFD) obtained at 96 h were 58.2, 52.4; 62.7, 62.3 and 56.7, 52.6% for AH, OGH and BGH, respectively. Lag times (h) for corrected DMD and CPD were shorter (at least P less than .05) than for apparent disappearances, except for corrected CPD of AH. There were no differences (P greater than .10) in lag time of NDFD or ADFD among forages. Rates of disappearance (%/h) of corrected DMD and CPD were faster (at least P less than .01) than for apparent disappearances. The total quantity of microbial CP (mg CP/g DM) associated with residues varied with time depending on forage type (P less than .001). There was a significant relationship between the quantity of microbial CP contamination and the extent of disappearance. Masticated forages followed trends similar to those of nonmasticated forages, but the effect of mastication was not consistent. Results support the need for microbial correction of in situ forage residues.

Technical note: preservation of tissues and gastrointestinal tract portions by plastic coating or plastination.

Two methods to preserve gastrointestinal tract (GIT) organs and tissues, plastic coating (PC) and plastination (PN), were investigated and compared. Specimens to be preserved were removed from animals within 2 h of death and immediately cleaned with water. Digesta contents were removed by flushing desired portions of GIT with water until the exiting water was clear. In the PC method, cleaned specimens were dehydrated by immersion in an isopropanol solution, dried with forced air after positioning and orientation as in situ, and finally coated on the outer and inner surfaces with a clear plastic material. In the PN procedure, specimens were filled with, and submerged in, a low-formaldehyde fixative, then dehydrated by immersion in a cold acetone solution. Dehydrated specimens were immersed in silicone and placed in a freeze drier for impregnation under low vacuum, followed by overnight gas curing with a silicone crosslinker. Finally, viewing windows were cut out with a scalpel in GIT preserved by both methods. Preserved GIT and tissues had an appearance similar to their appearance in vivo. The PC method was simple and inexpensive. Plastinated specimens were more flexible, durable, and lifelike than those preserved by the PC method. In addition, many body parts, such as muscles, nerves, bones, ligaments, and central nervous system specimens, were preserved by PN. Both methods were found to be useful tools for postmortem studies of tissues and GIT organs.

Whole-tract digesta kinetics and comparison of techniques for the estimation of fecal output in steers fed coastal bermudagrass hay at four levels of intake.

Coastal bermudagrass (Cynodon dactylon [L.] Pers) hay was fed to four ruminally cannulated steers (380 +/- 14 kg BW) of evaluate the effects of intake level on digesta flow kinetics in a 4 x 4 Latin square design. Forage intakes represented 50, 70, 88, and 99% of feed voluntarily consumed per animal during a pre-experimental period. Masticated boli and wet-sieved masticated leaves (ML) and stems (MS) retained by a 4.0-mm sieve and feces retained by a .063-mm sieve were mordanted with chromium or marked with erbium, ytterbium, or dysprosium, respectively. Particle markers and a solution of Co-EDTA were pulse-dosed via the ruminal cannula. A continuous infusion of Co-EDTA was later delivered with peristaltic pumps. Intake level had no effect (P > .10) on fluid and particle passage rate (PR; percentage/hour) of any fractions marked. For all particle fractions, increasing intake level caused linear decreases in mean retention time (MRT; P < .03 to P < .07) and linear increases in gastrointestinal tract fill (FILL; P < .003 to P < .02) and fecal output (FO; P < .001). Estimates of FO and DM digestibility from the pulse dose of Cr mordant and continuous infusion of Co-EDTA did not differ. Kinetic estimates differed in magnitude according to the characteristics of the particle fractions marked. Marked feces gave the shortest estimate of MRT and the smallest estimate of FILL and FO. Kinetics of ML and MS also differed (P < .001), the former having faster PR, shorter MRT, and smaller FILL and FO. Use of representative samples of ingested feed should give more realistic estimates of digesta kinetics than estimates derived from ingesta fractions because kinetics of separated leaf and stem fractions differed.

Effects of grass species on grazing steers: II. Dry matter intake and digesta kinetics.

Animal responses to treatments in grazing experiments frequently remain unexplained because of inadequate pasture and(or) animal measurements. This 2-yr study examined DMI, gastrointestinal tract fill of undigested DM (FILL), rate of digesta passage (ROP), and digesta mean retention time (MRT) for steers grazing tall fescue (Festuca arundinacea Schreb.), switchgrass (Panicum virgatum L.), flaccidgrass (Pennisetum flaccidum Griseb.), and bermudagrass (Cynodon dactylon [L.] Pers.). A randomized complete block design was used with two agronomic replicates. Comparisons in June (yr 1) among continuously grazed switchgrass (SG), flaccidgrass (FG), and bermudagrass (BG) or in May (yr 2) among tall fescue (TF), SG, and FG showed similar digesta kinetics, but different DMI (kg.d-1.100 kg BW-1), among these forages within each sampling. In the June evaluation, the DMI of SG and FG were similar (means = 3.09), DMI of bermudagrass (BG) was lowest (2.23), and fecal DM output (FO) was similar among forages. In the May evaluation, DMI by steers grazing SG (3.90) was higher than that by steers grazing FG (2.97); DMI of tall fescue (TF) was intermediate (3.41) but similar to DMI of FG. Differences in DMI were due to differences in diet in vitro DM disappearance (IVDMD) rather than to differences in digesta kinetics. In July (yr 2), the MRT was highest for BG (84 h) and similar for SG and FG (57 h). Steers grazing different forages exhibited similar ROP and FILL, but FO (kg.d-1.100 kg BW-1) among steers varied (.37 for steers fed BG; .74 for steers fed SG and FG).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of monensin on voluntary intake, eating and ruminating behavior and ruminal motility in heifers fed corn silage.

Eating and ruminating behavior and associated ruminal motility of six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) given ad libitum access to corn silage with or without 100 mg monensin X head-1 X d-1 were examined according to a two-period crossover design. There was no effect (P greater than .05) of monensin on level of intake, daily and unitary eating, ruminating and masticating times [min X g dry matter-1 X (kg body weight X 75)-1], duration or number of these activity periods, duration of main meals or latency time for onset of rumination following cessation of main eating activities. With the monensin treatment, daily numbers of normal boli and total boli were decreased (P less than .05) and mean duration of one rumination bolus cycle was longer (P less than .05). Analysis of covariance indicated relationships between intake of corn silage and duration of the main morning meal, duration or number of rumination boli and total ruminal contractions were affected (P less than .01) by monensin. Frequency and unitary number of strong cranio-dorsal ruminal contractions were similar for both treatments. During eating, number of contractions per minute was about twice (2.55/min) that during idling and rumination activity (1.43/min and 1.22/min, respectively). The unitary daily number of contractions was negatively (P less than .05) related to level of intake. Total daily ruminal contractions were slightly reduced (-3.96%, P greater than .05) by monensin. Results are interpreted to suggest that monensin indirectly affects rumination through a lowered motility and thereby affects turnover, gut fill and intake.

Fragmentation and flow of grazed coastal Bermudagrass through the digestive tract of cattle.

Samples of forage fragments were obtained from the upper (RUS) and lower (RLS) strata of the reticulorumen and feces (F) of four Brahman X Jersey steers grazing Coastal bermudagrass (CB) of two maturities with dry matter digestibilities (DMD) of 54.8 and 64.3%. Forage fragments were separated by particle size and evaluated histochemically for tissue type and fragmentation pattern. Fragmentation pattern was similar to that previously observed due to ingestive mastication. There was longitudinal separation of vascular bundles (VB) and severing at VB ends. Microscopically, similar size fragments from RUS were indistinguishable from those of RLS. The major difference between RUS and RLS was the distribution of different size particles. Larger particles were associated with the RUS in cattle consuming immature and mature CB. More large particles were associated with mature compared with the immature CB in the RUS and RLS. The distribution of different size particles in the F was similar for both maturities, suggesting that similar particle size reduction was required regardless of maturity. Smaller particles in the rumen and F appeared to contain more lignin (determined histochemically) and were composed of indigestible fragments of cuticle and lignified vascular tissue. Cattle grazing mature CB had higher ruminal fills (2.40 vs 2.02 kg dry matter/100 kg body weight), reduced rates of passage and lower voluntary intake (2.50 vs 3.14 kg DM/100 kg body weight). Lower intake of mature CB may have resulted from a reduced rate of particle size reduction. Similarities in fragmentation patterns due to ingestive and ruminative mastication were interpreted to indicate that mastication was responsible for most of the particle size reduction of CB and that mastication facilitated digestion of potentially digestible tissues.

Eating and ruminating behavior of steers fed Coastal Bermudagrass hay at four levels.

Effects of feeding level on chewing behavior and physical reduction of particles during ingestive mastication and rumination were examined in four ruminally cannulated steers fed Coastal bermudagrass (Cynodon dactylon [L.] Pers.) hay in the long form. The experimental design was a 4 x 4 latin square with 18-d periods. Treatments based on previous intakes were set at 50, 70, 90 and 110% of feed consumed per animal. Steers were fed at 12-h intervals. Chewing behavior was monitored over 4 d with a computerized system. Boli of ingested, masticated hay (MH), collected at the cardia, and serial samples of digesta taken from the ruminal upper strata (RUS) were wet-sieved. Dimensions of MH particles retained on 4.0- and 2.0-mm sieves were determined by image analysis. Increasing feeding level resulted in a linear increase in the number of boli ruminated (P less than .01) and in linear increases in eating (P less than .01), ruminating (P less than .05) and total chewing time (P less than .01). Linear increases in number of eating (P less than .01), ruminating (P less than .01) and total chews (P less than .01) also were observed. Feeding level had no effect on bolus duration, number of chews/bolus, number of boli/min rumination time and number of chews/min rumination time. The extent of particle breakdown during ingestive mastication was a determinant of the number of boli ruminated daily and their associated number of chews. Number of boli ruminated daily also was related to the RUS mean particle size. Eating time did not provide a reliable indication of how well feed was chewed.(ABSTRACT TRUNCATED AT 250 WORDS)

Passage of chromium-mordanted and rare earth-labeled fiber: time of dosing kinetics.

Coastal bermudagrass hay was labeled with Cr by the Cr-mordant procedure and with 177Lu applied to the same fiber. Neutral detergent fiber prepared from the same Coastal bermudagrass hay was labeled with Yb, 169Yb, Tb and 160Tb by soaking overnight following by thorough washing and drying. Wood chips were similarly labeled with Sm or La, and Solka Floc was labeled with 147Nd and 141Ce. The carriers, labels and times of administration to cattle were: bermudagrass fiber with both Cr and 177Lu, bermudagrass fiber with 169Yb and Solka Floc labeled with 147Nd at 0 h; bermudagrass fiber with Yb, Solka Floc with 141Ce and wood chips with Sm at 24 h; wood chips with La at 48 h; and bermudagrass fiber labeled with 160Tb at the beginning and labeled with Tb at the end of a meal. Fecal collection followed and passage characteristics were determined with a two-compartment, age-dependent model. Markers labeling the different fiber sources had different (P less than .01) passage rates (Solka Floc greater than Coastal bermudagrass greater than wood chips), but there was no difference within fiber source for rare earth passage. There also was no difference between the passage characteristics of Cr-mordant and 177Lu. However, passage rate of particles administered at the beginning of the meal (160Tb) was 42% higher than for particles at the end of the meal (Tb).(ABSTRACT TRUNCATED AT 250 WORDS)

Selection among nonlinear models for rate of passage studies in ruminants.

Eight Toggenburg wether goats were fed either Coastal bermudagrass (Cynodon dactylon) or orchardgrass (Dactylis glomerata)-alfalfa (Medicago sativa) hay (57:43%) in a reversal design. Four markers were used to study the movement of different digesta fractions: erbium for large particles greater than 1,700 microns; ytterbium for medium particles less than 1,700 microns and greater than 500 microns; chromium for small particles less than 500 microns and greater than 32 microns; and cobalt to follow liquid passage. Fecal samples were collected every 4 h for 6 d. The excretion curves obtained for every marker in each animal were used for model selection. One-compartment gamma age-dependent models (gamma 2, 3 and 4 age-dependent), two-compartment (gamma 2 and gamma 3 age-dependent, age-independent) models and a biexponential model were fitted to the data. Residual sums of squares and the Davidson and MacKinnon test were used to select the most appropriate models. These procedures indicated that the models best describing the movement of different digesta fractions through the gastrointestinal tract of goats, in this experiment, were the biexponential model for liquids, gamma 2 two-compartment model for small and medium particles and gamma 3 two-compartment model for large particles. To accurately describe the behavior of different components of digesta in the digestive tract, different mathematical models are required. In general, models that describe the movement of large particles have higher orders of age-dependency than models that describe the passage of liquids or small particles.

Effects of ingestive mastication on particle dimensions and weight distribution of coastal bermudagrass hay fed to steers at four levels.

Coastal bermudagrass (Cynodon dactylon [L.] Pers.) hay was fed in the long form to four ruminally cannulated steers to evaluate the effects of intake level on the physical reduction of feed particles during ingestive mastication. The experimental design was a 4 x 4 latin square with 18-d periods. Treatments based on previous intakes were set at 50, 70, 90 and 110% of feed consumed per animal and fed at 12-h intervals. Boli of ingested, masticated hay were collected at the cardia and separated by wet-sieving into fragments retained on sieves of .0027 to 4.0 mm (mesh aperture). In addition, particles retained on the 4.0-mm and 2.0-mm sieves were scanned by image analysis. Ingestive mastication resulted in a linear decrease (P less than .05) in the proportion of boli particles retained on the top (4.0-mm) sieve and linear increases on the 2.0- (P less than .02), 1.0- (P less than .06) and .25-mm (P less than .06) sieves with increasing level of intake. Sixteen to 21% of the ingested hay particles passed through a 1.0-mm sieve. Mean particle size, as determined by sieving data, decreased linearly (P less than .05) as feeding level increased. Image analysis showed no differences in length (L) or width (W) of particles retained on the 4.0- and 2.0-mm sieves as feeding level increased, but L/W decreased linearly (P less than .05) on both sieves. The frequency of jaw movements following feeding was very similar across feeding levels and averaged 71.3 chews/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in forage quality, ingestive mastication, and digesta kinetics resulting from switchgrass maturity.

Five maturities of switchgrass hay harvested at 14-d intervals (vegetative through 20% heading) were fed to Hereford steers (297 kg) in a 5 x 5 Latin square. Relationships with switchgrass maturity were negative and quadratic (P < .05) for DMI and cubic (P < .05) for digestible DMI. Declines in apparent digestibilities of DM, ADF, and cellulose were cubic (P < .05), whereas these were quadratic (P < .05) for NDF, hemicellulose, and CP. Whole masticates from the least, mid, and most mature hays showed linear (P < .05) declines in DM concentration and IVDMD with increasing maturity, whereas NDF concentrations increased linearly (P < .05). Mean retention time of gastrointestinal DM increased linearly (P < .01) from 64 to 94 h from the least to the most mature hay, and the associated rate of passage declined linearly (P < .01) from 3.3 to 2.1%/h. Sieving of masticate DM showed a reduced proportion of large particles (> or = 2.8 mm) and an increased proportion of small particles (< or = .5 mm) with advancing forage maturity. More than 94% of the sieved fecal DM passed a 1.0-mm sieve, but particle sizes showed the same relationship with forage maturity as noted for masticate DM. This occurred despite the comminution from the rumination and digestive processes.

Evaluation of the Captec chrome controlled-release device for the estimation of fecal output by grazing sheep.

Three grazing experiments were conducted to compare actual fecal output (FO) by sheep, determined with fecal collection bags, to fecal output predicted using Captec chromic oxide (Cr2O3) controlled-release capsules. In Exp. 1, 14 crossbred wethers dosed with controlled-release Cr2O3 capsules rotationally grazed four paddocks of alfalfa (Medicago sativa L.) for 18 d. Total fecal collection and grab samples were taken daily from each animal; feces were dried and assayed for Cr. From d 5 to 12 after dosing, mean actual FO (429 +/- 9.6 g of DM/d) differed (P less than .001) from FO predicted by the capsule (463 +/- 12.8 g of DM/d). The correlation between actual and predicted FO was r = .59. When data were averaged by day, the correlation increased to .82. In Exp. 2, Tifton 44 bermudagrass (Cynodon dactylon [L.] Pers.) was strip-grazed for 30 d by the same 14 wethers used in Exp. 1. Mean actual FO (369 +/- 5.1 g of DM/d) differed (P less than .0001) from predicted FO (415 +/- 9.3 g of DM/d), with a correlation of .60. In Exp. 3, 72 crossbred lambs were blocked by weight (light and heavy) and assigned to six groups of eight wethers (four with fecal bags) and four ewes, allotted randomly to three stocking rates (74, 99, and 148 sheep/ha). Sampling occurred from d 6 to 10 after dosing (Period 1) and d 20 to 24 after dosing (Period 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Image analysis and nonlinear modeling to determine dimensions of wet-sieved, masticated forage particles.

A procedure to estimate dimensions of digesta particles was developed and evaluated. After wet sieving, particles of masticated switchgrass and bermudagrass hays retained on sieves with apertures of 1.0 mm2 or larger were placed on moist white filter paper, separated manually, and photographed. Photographs were scanned with a flat-bed scanner, scaled to size, and digitized. Projected area, perimeter, length, and width of particles were determined by a microcomputer system. Variables derived for each particle included the form factor, which was defined as (4 x pi x area)/perimeter2, and each particle's length: width ratio. Ninety-three percent of data from two trials with steers had significant lack of fit (P less than .05 to P less than .0001) to normal, lognormal, Weibull, or gamma distributions. As an alternative, individual particle measurements were summed on a cumulative percentage basis for each variable and were fit to an inverted Gompertz function to estimate median, mode, and mean dimensions of scanned particles. Estimates from the equation fit the distribution well; asymptotic SE averaged 3.5 and 1.4% of parameter means for dimensions of masticated switchgrass and bermudagrass hay particles, respectively. No analytic solution exists for the mean, which must be estimated numerically, but analytic solutions are available for the median and mode. Use of this equation will prevent bias caused by lack of fit to a particular distribution and yield more accurate estimates of mean particle dimensions than arithmetic means.