Technical note: development and testing of a radio transmission pH measurement system for continuous monitoring of ruminal pH in cows

An indwelling ruminal pH system has been used for the continuous recording of ruminal pH to evaluate subacute ruminal acidosis (SARA) in dairy cows. However this system does not allow the field application. The objective of this study was to develop a new radio transmission pH measurement system, and to assess its performance and usefulness in a continuous evaluation of ruminal pH for use on commercial dairy farms. The radio transmission pH measurement system consists of a wireless pH sensor, a data measurement receiver, a relay unit, and a personal computer installed special software. The pH sensor is housed in a bullet shaped bolus, which also encloses a pH amplifier circuit, a central processing unit (CPU) circuit, a radio frequency (RF) circuit, and a battery. The mean variations of the measurements by the glass pH electrode were +0.20 (n = 10) after 2 months of continuous recording, compared to the values confirmed by standard pH solutions for pH 4 and pH 7 at the start of the recording. The mean lifetime of the internal battery was 2.5 months (n = 10) when measurements were continuously transmitted every 10 min. Ruminal pH recorded by our new system was compared to that of the spot sampling of ruminal fluid. The mean pH for spot sampling was 6.36 ± 0.55 (n = 96), and the mean pH of continuous recording was 6.22 ± 0.54 (n = 96). There was a good correlation between continuous recording and spot sampling (r = 0.986, P < 0.01). We also examined whether our new pH system was able to detect experimentally induced ruminal acidosis in cows and to record long-term changes in ruminal pH. In the cows fed acidosis-inducing diets, the ruminal pH dropped markedly during the first 2 h following the morning feeding, and decreased moreover following the evening feeding, with many pulse-like pH changes. The pH of the cows showed the lowest values of 5.3-5.2 in the midnight time period and it recovered to the normal value by the next morning feeding. In one healthy periparturient cow, the circadian changes in ruminal pH were observed as a constant pattern in the pre-parturient period, however that pattern became variable in the post-partum period. The frequency of the ruminal pH lower than 5.5 increased markedly 3 and 4 days after parturition. We demonstrated the possible application of a radio transmission pH measurement system for the assessment and monitoring of the ruminal pH of cows. Our new system might contribute to accurate assessment and prevention of SARA.     

Technical note: a device for obtaining time-integrated samples of ruminal fluid.

A device was adapted to allow for time-integrated sampling of fluid from the rumen via a cannula. The sampler consisted of a cup-shaped ceramic filter positioned in the ventral rumen of a cannulated cow and attached to a tube through which fluid entering the filter was removed continuously using a peristaltic pump. Rate of ruminal fluid removal using the device was monitored over two 36-h periods (at 6-h intervals) and was not affected (P > .05) by time, indicating that the system was not susceptible to clogging during this period. Two cows having ad libitum access to a totally mixed ration were used in a split-block design to evaluate the utility of the system for obtaining time-integrated samples of ruminal fluid. Ruminal fluid VFA concentration and pattern in samples collected in two replicated 8-h periods by the time-integrated sampler (at 1-h intervals) were compared with composite samples collected using a conventional suction-strainer device (at 30-min intervals). Each 8-h collection period started 2 h before or 6 h after feeding. Results indicated that total VFA concentration was not affected (P > .05) by the sampling method. Volatile fatty acid patterns were likewise unaffected (P > .05) except that acetate was 2.5% higher (P < .05) in samples collected 2 h before feeding and valerate was 5% higher (P < .05) in samples collected 6 h after feeding by the suction-strainer device. Although significant, these differences were not considered physiologically important. We concluded that use of the ceramic filter improved the sampling of ruminal fluid by simplifying the technique and allowing time-integrated samples to be obtained.     

Technical note: validation of the GreenFeed system for measuring enteric gas emissions from cattle

There are knowledge gaps in animal agriculture on how to best mitigate greenhouse gas emissions while maintaining animal productivity. One reason for these gaps is the uncertainties associated with methods used to derive emission rates. This study compared emission rates of methane (CH₄) and carbon dioxide (CO₂) measured by a commercially available GreenFeed (GF) system with those from (1) a mass flow controller (MFC) that released known quantities of gas over time (i.e., emission rate) and (2) a respiration chamber (RC). The GF and MFC differed by only 1% for CH₄ (P = 0.726) and 3% for CO₂ (P = 0.013). The difference between the GF and RC was 1% (P = 0.019) for CH₄ and 2% for CO₂ (P = 0.007). Further investigation revealed that the difference in emission rate for CO₂ was due to a small systematic offset error indicating a correction factor could be applied. We conclude that the GF system accurately estimated enteric CH₄ and CO₂ emission rates of cattle over a short measurement period, but additional factors would need to be considered in determining the 24-hr emission rate of an animal.     

Technical note: a double L intestinal cannula for cattle

A double L-shaped intestinal cannula was developed in an attempt to overcome problems observed previously with simple T-type cannulas. The cannula was constructed from cyclopolyvinyl chloride water pipe fittings. Construction materials were fairly rigid, but by connecting the split cannula pieces with elastic castration bands the cannula had some flexibility. Placing a short cone over the exposed cannula barrel reduced mechanical damage to the intestine. The double L cannula required a much smaller incision in the intestine during surgical insertion than a T-type cannula; it also simplified replacement. Construction is described; use and performance of the cannula has been satisfactory.     

Technical note: covariance adjustment in beef cattle research

In randomized experiments, analysis of covariance is used to increase precision of treatment comparisons. However, for factors that are observational (e.g., breed) or for covariates measured after treatments are applied, it may not be biologically meaningful to calculate treatment means adjusted to a common value of the covariate. For example, in beef cattle trials, it may not be meaningful to compare hot carcass weights of medium- and large-framed breeds adjusted to a common weaning weight because the breeds have naturally different mean weights at weaning. If done, this would typically result in an undesirable downward adjustment of mean carcass weight for the large-framed breed and upward adjustment of the mean carcass weight for the small-framed breed. However, it is desirable to evaluate the mean carcass weight for two diets, adjusted to a common weaning weight. Because of randomization, the expected weaning weights of animals on the two diets are equal and hence the only effect of covariance adjustment is to increase precision of the diet comparison. This paper presents the statistical methodology for estimating covariance adjusted means (termed partially adjusted means) when the levels of some of the factors are compared at a common value of the covariate but the levels of other factors are compared at differing values of the covariate. The methodology is extended to include several covariates, several factors, and arbitrary interactions among covariates, among factors, and between factors and covariates. These methods can be implemented using existing statistical software for linear models. Data are presented from an experiment in which hot carcass weight was recorded for beef cattle. Analyses of these data illustrate that adjusted means, partially adjusted means, and unadjusted means may differ substantially in magnitude, significance, and in the ranking of treatments.     

Technical note: isolation and characterization of sheep ruminal epithelial cells

A system for the isolation and characterization of sheep ruminal epithelial cells has been developed. Ruminal papillae from the ventral cranial sac of 12- to 24-wk-old Dorset ram lambs were subjected to serial tryptic digestions. Initial digestions (two 15-min periods) in the series were used to remove keratinized cells of the stratum corneum, which were able to produce only small amounts of beta-hydroxybutyrate from butyrate (5.37 +/- .72 nmol/120 min/per milligram of dry cell weight). Later digest fractions, containing primarily cells from the stratum basale, exhibited high viabilities (75 to 95%) and proved capable of converting butyrate to beta-hydroxybutyrate at relatively high rates (33.6 +/- 6.7 nmol/120 min per milligram of dry cell weight). Neither acetate nor propionate underwent significant conversion to beta-hydroxybutyrate. However, addition of acetate inhibited (77.4% of control) and addition of propionate stimulated (200% of control) beta-hydroxybutyrate production. Acetate addition reduced the propionate-induced stimulation of beta-hydroxybutyrate production from butyrate (136% of control). These results are similar to those obtained from in vitro incubations of ruminal papillae and suggest that an isolated cell system may prove useful in the further study of ruminal epithelial metabolism.     

Technical note: stearidonic acid metabolism by mixed ruminal microorganisms in vitro

Dietary supplementation of stearidonic acid (SDA; 18:4n-3) has been considered a possible strategy to increase n-3 unsaturated fatty acid content in ruminant products; however, little is known about its metabolism in the rumen. In vitro batch incubations were carried out with bovine ruminal digesta to investigate the metabolism of SDA and its biohydrogenation products. Incubation mixtures (4.5 mL) that contained 0 (control), 0.25, 0.50, 0.75, 1.00, 1.25, or 1.50 mg of SDA supplemented to 33 mg (DM basis) of commercial total mixed ration based on corn silage, for dairy cows, were incubated for 72 h at 39°C. The content of most fatty acids in whole freeze-dried cultures was affected by SDA supplementation. Branched-chain fatty acids decreased linearly (P < 0.01), and odd-chain fatty acids decreased quadratically (P < 0.01), particularly from 1.00 mg of SDA and above, whereas most C18 fatty acids increased linearly or quadratically (P ≤ 0.04). Stearidonic acid concentrations at 72 h of incubation were very small (<0.6% of total fatty acids and ≤0.9% of added SDA) in all treatments. The apparent biohydrogenation of SDA was extensive, but it was not affected by SDA concentration (P > 0.05). Biohydrogenation followed a pattern similar to that of other C18 unsaturated fatty acids up to 1.00 mg of SDA. Stearic acid (18:0) and vaccenic acid (18:1 trans-11) were the major fatty acids formed, with the latter increasing 9-fold in the 1.00 mg of SDA treatment. At greater inclusion rates, 18:0 and 18:1 trans isomers decreased (P ≤ 0.03), accompanied by increases in unidentified 18:3 and 18:4 isomers (P = 0.02), suggesting that the biohydrogenation pathway was inhibited. The present results clearly indicate that SDA was metabolized extensively, with numerous 18:4 and 18:3 products formed en route to further conversion to 18:2, 18:1 isomers, and 18:0.     

Research note: a method for studying local differences in ruminal fermentation in dairy cattle.

A method was developed for studying local differences in ruminal fermentation. The developed sampler consisted of an acrylic glass container (460 cm3) with an aperture for digesta sampling, which could be opened and closed by the scaled "T" rod. The scale was a reference for defined rumen layers: top, middle, 5 to 10 cm and 25 to 35 cm beneath the top of particles mat, respectively, and bottom 5 to 10 cm above the rumen floor. The repeatability of the method was proved in two rumen cannulated cows. Particle/fluid ratio, pH and sample amount were measured 2 to 2 1/2 h after morning feeding in four replicates each day (over 5 days), rumen layer and animal. No significant differences between replicates were observed. The coefficients of variation (CV) of the particle/fluid ratio varied between 8.7% and 13.6%. Top layer had higher CV than middle and bottom layer. CV of pH ranged between 0.59% and 1.27%. The developed method of sampling showed satisfactory repeatability for investigation of digesta properties and fermentation in different rumen layers.     

Technical note: mineral deposits on Dacron bags during ruminal incubation.

Extensive DM contamination was found on Dacron bags that were incubated for prolonged periods of time in the rumen of steers fed alfalfa hay. The ash content of the contaminant was high, and most of it was acid-soluble X-ray analysis indicated the presence of hydroxylapatite and synthetic calcium magnesium phosphate or whitlockite. The contaminant appeared as a smooth coating on the Dacron fiber, suggesting that contamination was a gradual process rather than the result of entrapment of dislodged crystals from plant material. Contamination seemed to occur exponentially within the range of observations (0 to 42 d). Contamination also occurred in steers fed orchardgrass, although to a lesser extent than in steers fed alfalfa hay. The DM contamination was less than .04 g per bag (average bag weight was 1.2 g) during the first 10 d of incubation. However, correction for contamination might be required for studies involving longterm incubation or mineral digestion.     

Pathophysiological evaluation of subacute ruminal acidosis (SARA) by continuous ruminal pH monitoring

Evaluation of the radio‐transmission pH‐measurement system for monitoring the ruminal pH and subacute ruminal acidosis (SARA) in cattle is described. This is done in order to reveal the possible application of this system for detection and pathophysiological research of SARA by continuous ruminal pH measurement. The possibility of using this system for assessment of the ruminal pH in SARA cattle, and the presence of negative correlation between the ruminal pH and ruminal temperature in heathy and SARA cattle were determined. In addition, the 16S rRNA gene pyrosequencing analysis showed that the ruminal microbial community was simpler in SARA cattle, and the bacterial numbers in SARA cattle were lower than those in healthy hay‐fed cattle. Concentrate feeding might have reduced the diversity of the ruminal microbial community. Changes in the ruminal microbial community of SARA cattle might be related to the changes in ruminal pH followed by the decrease in the number of some bacteria. Continuous monitoring of the ruminal pH using the radio‐transmission pH‐measurement system would be applied for detection and prevention of SARA in the field and pathophysiological research of SARA, including ruminal zymology and bacteriology, which have been determined previously by sampling of the ruminal fluid and measuring of ruminal pH.     

Continuous automated recording of ruminal pH in sheep nourished entirely by intragastric infusions

A method is described whereby the rumen pH in sheep entirely nourished by infusion of volatile fatty acids was determined continuously. The electrodes used were standard laboratory combination electrodes connected to a digital pH meter, a multi-channel chart recorder and an isolation module. The correlation between pH readings from the bench samples and from electrodes immersed in the rumen for periods of up to 28 days was 0.980 +/- 0.015 for 250 observations. There were fairly regular patterns of change in ruminal pH. The pH rose and fell by approximately 0.1 to 0.2 units over a period of about one hour. These changes were thought to be associated with periods of pseudorumination.     

A radio transmission pH measurement system for continuous evaluation of fluid pH in the rumen of cows

We developed a novel wireless radio transmission pH measurement system to continuously monitor ruminal bottom pH in cows, and compared these measurements to pH values determined by a spot-sample method. The wireless system consists of a pH sensor, data measurement receiver, relay unit, and personal computer with special software. The bullet-shaped sensor can be easily administered orally via a catheter into the rumen, without surgery. The glass electrode, using a temperature compensation system, can detect the rumen fluid pH with high accuracy. The ruminal bottom pH in healthy rumen-fistulated cows was measured as 6.52 ± 0.18 by the wireless system and as 6.62 ± 0.20 by the spot-sample method; with a correlation between pH measurements using these different methods (n = 8, 24 samples, r = 0.952, P < 0.01). When measured serially in a cow fed a diet evoking rumen acidosis, the ruminal bottom pH decreased markedly following the morning feeding and then increased gradually by the next morning feeding. This wireless system is a ready-to-use tool for estimating circadian changes in ruminal bottom pH.     

Technical note: A novel technique to assess internal body fat of cattle by using real-time ultrasound

The objectives of this study were to describe a system to assess KPH fat by using real-time ultrasound (RTU) and to develop equations to predict total physical separable internal fat (IFAT) based on ultrasound measurements. Data for this study were obtained from 24 Angus steers fed either hay- or corn-based diets during the backgrounding phase. Steers were serially slaughtered in 3 groups: at weaning (baseline), then at 4 and 8 mo after weaning. A fourth group was composed of 4 steers from the hay-fed group that were slaughtered at approximately 10 mo after weaning. The RTU measurements were collected every 2 mo, with a preslaughter scan approximately 7 d before the slaughter time. The RTU measurements consisted of 12th- to 13th-rib backfat thickness, 12th to 13th ribeye area, percentage of intramuscular fat, and kidney fat depth, which was measured in a cross-sectional image collected between the first lumbar vertebra and the 13th rib. For kidney fat, the ultrasound probe was placed on the flank region approximately 15 cm from the midline of the animal. Images were stored in the ultrasound console, and measurements were taken between the ventral part of the iliocostalis muscle and the end of the KPH fat at the chute side. The relationship between carcass and ultrasound measurements in the depths of kidney fat (cKFd and uKFd, respectively) had an r(2) of 0.93, with a root mean square error (RMSE) of 1.14 cm. An allometric regression between carcass KPH weight (cKPHwt) and cKFd was identified, and the untransformed regression had an r(2) of 0.96. The linear regression between total IFAT and cKPHwt had an r(2) of 0.97, with an RMSE of 2.67 kg. Therefore, a system was developed to predict IFAT from uKFd measurements by combining these equations. Additionally, a single linear regression between IFAT and uKFd measurements was developed (r(2) = 0.89, RMSE = 5.32 kg). Even though the system of equations had a lower RMSE of prediction and greater r(2) compared with the single linear regression (4.80 vs. 5.10 kg and 0.91 vs. 0.89, respectively), there was no difference between these methods in predicting IFAT (P = 0.4936) by using a pairwise mean square error of prediction analysis. Our results indicated that uKFd measurements can accurately and precisely predict the cKFd of steers consuming either high concentrate or forage rations. The results also showed that cKFd is highly correlated with cKPHwt, which can be used to estimate total IFAT. More research is needed to further evaluate this technique with different feeding strategies, breeds, and sexes.     

Diagnosis of subacute ruminal acidosis (SARA) by continuous reticular pH measurements in cows

The objective of this study was to determine whether subacute ruminal acidosis (SARA) could be diagnosed by continuous measurements of the reticular pH, as compared with the ruminal pH, using healthy cows fed a control diet and SARA cows fed a rumen acidosis-inducing diet. The reticular and ruminal pH were measured simultaneously by a radio transmission pH measurement system. The mean reticular pH at 1-h intervals decreased gradually from the morning feeding to the next feeding time in both healthy and SARA cows, though the decrease in the ruminal pH was observed to be more drastic as compared with that observed in the reticular pH. The threshold of the 1-h mean pH in the reticulum for a diagnosis of SARA was considered to be 6.3, and a significant positive correlation was observed between the reticular and ruminal pH. No differences in the concentrations of lactic acid, ammonia nitrogen, and volatile fatty acids were noted between the reticular and ruminal fluids in SARA cows. These results demonstrate that the reticular pH can be used to detect SARA in cows, as opposed to using the ruminal pH.     

Technical note: effectiveness of different methods of continuous marker administration for estimating fecal output.

Six ruminally fistulated crossbred steers (BW = 369 kg) were used in a randomized complete block experiment to test the efficacy of continuous-infusion pumps and controlled-release boluses for administering external markers to predict fecal output. Steers, limit-fed chopped alfalfa hay at 2% of BW daily, were fitted with continuous-infusion pumps that administered Co-EDTA and YbCl3 solutions intraruminally. In addition, a controlled-release bolus containing Cr2O3 was inserted into the rumen of each steer. Fecal grab samples were taken every 6 h for 7 d during initial marker equilibration; after this period, fecal grab samples were taken every 3 h for 48 h to evaluate diurnal variation patterns. Steers were subsequently fitted with fecal bags for 7 d to allow total fecal collection. Grab samples also were taken during the total fecal collection period at 0600 (AM) and 1400 (PM). The marker X time effect was nonsignificant. Similarly, time of grab sampling (AM or PM) did not affect estimates of fecal output (P greater than .10), but the Cr2O3 bolus overestimated fecal output (P less than .05). Fecal marker concentrations during the 48-h profile showed little diurnal variation regardless of marker used. All markers equilibrated in the feces at approximately 100 to 120 h after initiating infusions. The continuous-infusion pumps evaluated were efficacious for administering markers for estimating total fecal output in limit-fed steers; however, the Cr2O3 boluses evaluated overestimated fecal output when the manufacturer's suggested release rate was used for fecal output calculations.     

A method for recording the motor activity of the reticulum in cattle

A method for recording the motility of the reticulum in normal cattle has been devised. The method is based on measurement of the pressure variations occurring in connection with the reticular contractions. The pressure is transferred through open, water-filled catheters via a pressure transducer to an electromanometer, from which it is recorded with the aid of a mingograf.Mean values for the interval, duration and amplitude of the reticular contractions in 10 normal cows are given.The method permits recording in intact animals without any preliminary measures, and can therefore be used in clinical cases.     

Technical note: a dynamic model to predict the composition of fat-free matter gains in cattle

Composition of empty BW (EBW) was described in terms of ether-extractable lipid (FAT) and fat-free matter (FFM), and the terms dEBW, dFAT, and dFFM were used to represent daily gains in these components. The dFFM comprised protein, water, and ash, and a model was developed to predict the composition of dFFM. The conceptual approach used in model development was based on experimental data that showed as cattle grew from birth to maturity: 1) the water content of FFM decreased and the protein and ash content increased; 2) the protein content of FFM increased at a decreasing rate; and 3) the protein-to-ash ratio in the fat-free DM was approximately constant. These results suggest that the protein content of dFFM would be high at birth and decrease at a decreasing rate as the animal grows. The protein content of dFFM was predicted as a function of the fraction of dEBW that was dFFM, FAT content of EBW, and dFFM. A fixed protein-to-ash ratio of 4.1:1 was used to calculate the quantity of ash, and water was obtained as a residual. Growth and body composition of Hereford x Angus steers from birth to 500 kg BW were simulated with a previously published model using the experimental growth data as input, and the model under discussion was used to predict the composition of dFFM. Predicted response curves of the EBW components over the growth period were similar in shape to observed data. Predicted curvilinearity in response of protein weight against FFM weight for Hereford x Angus steers was similar to observed data. The standard error about the regression of predicted on observed protein weight was 1.87 kg, and the average bias of the model was to underpredict protein weight by 0.64%. Compared with using a constant value for the protein fraction of dFFM, the model provided more accurate predictions of dEBW in an independent evaluation data set.     

Comparative measurements on ruminal pH-value in cattle

Subacute rumen acidosis (SARA) of ruminants is an important factor in terms of animal health, especially in high yielding cattle. In order to find an accurate method to determine the ruminal pH-value, three methods using eight rumen cannulated cattle were compared. An indwelling measuring unit (sensor) was used for continuous measurement of the ruminal pH-value. These results were compared to the pH-values of samplings via rumen fistula and to the results of samplings via oral stomach tube. Due to the different rations, mean pH-value of trial 1 (average of all methods) was 6.64 +/- 0.37 (hay ad lib., 2 kg concentrate/ animal) and 6.24 +/- 0.36 for trial 2 (75% maize silage, 1 kg hay, 2 kg soybean meal). In trial 1 no statistically significant differences between all methods could be observed. Under more acidic ruminal conditions of trial 2 all methods differed significantly (p < 0.05). In the lower pH-range of trial 2, a difference of 0.32 that data can be collected continuously. The sensor system was evaluated by a comparison with standardized pH-dilutions (pH 4, pH 7). The sensor system has proven to be an accurate and reliable instrument (r = 0.9984) and it represents an innovative system for answering scientific questions in terms of rumen physiology and rumen pathology.     

Anti-lipopolysaccharide antibody administration mitigates ruminal lipopolysaccharide release and depression of ruminal pH during subacute ruminal acidosis challenge in Holstein bull cattle

The effects of anti-lipopolysaccharide (LPS) antibody on rumen fermentation and LPS activity were investigated during subacute ruminal acidosis (SARA) challenge. Eleven Holstein cattle (164 ± 14 kg) were used in a 3 × 3 Latin square design. Cattle were fed a roughage diet on days −11 to −1 (pre-challenge) and day 2 (post-challenge), and a high-grain diet on days 0 and 1 (SARA challenge). For 14 days, 0-, 2-, or 4-g of anti-LPS antibody was administered once daily through a rumen fistula. Ruminal pH was measured continuously, and rumen fluid and blood samples were collected on days −1, 0, 1, and 2. Significantly lower ruminal LPS activity on day 1 was observed in the 2- and 4-g groups than those in the 0-g group. In addition, significantly higher 1-hr mean ruminal pH on SARA challenge period (days 0 and 1) was identified in the 4-g group than in the 0-g group. However, rumen fermentation measurements (total volatile fatty acid [VFA], VFA components, NH₃-N and lactic acid) and peripheral blood metabolites (glucose, free fatty acid, beta-hydroxybutyrate, total cholesterol, blood urea nitrogen, aspartate aminotransferase and gamma-glutamyl transferase) were not different among the groups during the experimental periods. Therefore, anti-LPS antibody administration mitigates LPS release and pH depression without the depression of rumen fermentation and peripheral blood metabolites during SARA challenge in Holstein cattle.     

Technical note: Evaluation of the official identification system for pigs for sale in New South Wales

A study was undertaken at 2 saleyard (1 domestic, DS, and 1 export, ES) and 2 abattoir (1 domestic, DA, and 1 export, EA) locations in New South Wales, Australia, to assess the compliance (presence) and readability of body tattoos used to identify individual pigs presented for sale or slaughter. Each location was visited on 3 trading or slaughter days, and tattoo presence and readability of porkers (25 to 60 kg of BW), baconers (60 to 90 kg of BW), backfatters (>90 kg of BW but not for breeding), and breeders were recorded. A total of 4,655 pigs were inspected, including 158 DS, 1,599 ES, 1,257 DA, and 1,641 EA. Tattoo performance at the saleyards was influenced by producer (P < 0.05). Average brand presence at the DS (93.0%) did not differ (P = 0.28) from ES (74.2%). Tattoo compliance ranged from 88.3 to 100% of pigs across pig classes (P > 0.05) at DS. At the ES, tattoo compliance among baconers, backfatters, and breeding stock ranged from 82.4 to 88.3% and was greater (P < 0.05) than that of porkers (70.3%). Average readability was 85.4% at ES and 77.6% at DS (P > 0.05). Tattoo compliance differed (P < 0.05) between abattoirs (98.7% at DA and 92.6% at EA). Readability was greater (P < 0.05) at the EA (80.1%) than at the DA (72.0%). Final performance, as readable brands among animals sold or slaughtered, of the official tattoo system was similar between locations and ranged from 63 to 74%. Our results suggest that current compliance and readability of tattoos would compromise traceback to the farm of origin in the event of an emergency animal disease outbreak. Education activities on legislation requirements and tattoo procedure would likely increase compliance and performance of the system.