Surgery of the abomasum appears to be the most common abdominal surgery in dairy practice. It has been reported that up to 15% of the cows in some dairy herds develop abomasal displacement.1 Left displacement of the abomasum is largely a management disease in that it affects cows, most often in the first few weeks of lactation, that are being fed high concentrate diets to stimulate higher milk production. The full economic impact of abomasal displacement includes treatment of concurrent disease (eg, metritis, mastitis, and ketosis), treatment of the abomasal displacement, and loss of milk production. It is often difficult to fully appreciate the cost of the loss of production because the decreased milk production may be present throughout the entire lactation period, depending on the degree of illness.
Many factors including nutrition and concurrent disease contribute to LDA. The recent advent of genomic analyses has revealed genetic correlations with the development of LDA.2–4 Certainly, there should be a great interest in investigation of genetic polymorphisms to help determine any genetic predisposition or resistance to development of LDA. In the future, dairy cattle could perhaps be selected for a lower genetic risk of LDA, which may allow them to tolerate other management practices for high milk production without development of LDA. Presently, LDA continues to have a very important economic impact on the dairy industry, and practitioners will continue to make treatment decisions regarding affected dairy cows on the basis of economics, the advantages and disadvantages of each treatment option, and the preference for a particular surgical procedure.
Abomasal displacement and treatment were reported as early as the 1950s.5,6 Several surgical techniques have been described since that time. The techniques include omentopexy,7–10 left flank8,10 or paramedian abomasopexy,8–10 bar-and-toggle abomasopexy,10,11 and pyloro-omentopexy,8,10,12 as well as laparoscopic abomasopexy.12–14 Many of the various techniques have been compared.9,15–17 Some studies9,17,18 have followed cows treated for LDA from 60 days to up to 1 year. Longer follow-up information was obtained in 1 study14 wherein the mean follow-up period for cows was 15.5 months; in another study,19 cows were followed for up to 60 days into the first lactation after surgery. However, to our knowledge, pyloro-omentopexy has not been compared with omentopexy for the treatment of LDA in dairy cows and no studies (regardless of treatment) have followed the affected cows until they leave the herd. There are also reports of complications associated with several of the techniques,20–23 and the definitive best surgical treatment has not been identified. Many practitioners may preferentially use a technique simply because of their familiarity with that method; other techniques may be used on occasion as determined by factors such as the condition (illness or body condition score) of the cow, facilities (especially when working in the field), or available assistance.
Some large farms in the United States have lay workers trained to treat LDA with results reported to be comparable to those achieved by veterinarians.17 More aggressive anti-inflammatory treatment to quicken response time to treatment has been suggested24 as has the possible role of prokinetic drugs as a part of the treatment protocol.25
The objective of the study reported here was to evaluate reproductive performance and productive longevity of dairy cows treated for LDA with 1 of 2 surgical techniques (omentopexy vs pyloro-omentopexy). In addition, the intent was to determine differences in cull rates and reasons between treated cows and other cows in the herd that did not develop LDA. On the basis of our clinical experience, we hypothesized that the reoccurrence rate of LDA for cows treated by pyloro-omentopexy would be lower than that for cows treated by omentopexy and that cows treated for LDA would not be culled from this university herd sooner than herd mates not affected by LDA.
Materials and Methods
Case selection
A search was done of the medical records for cows from 1 farm (Purdue University Dairy) to identify those that were treated surgically for LDA in 2001 through 2005. The diagnosis of LDA was based on detection of a classic ping with simultaneous percussion and auscultation of the abdomen. For each case, various clinicopathologic tests were performed as directed by the clinician; as such, the specific tests and clinical information acquired were not sufficiently consistent to allow meaningful analysis in this retrospective study. All cases of LDA were treated via a standing right flank laparotomy by omentopexy (omentopexy group) or pyloro-omentopexy (pyloro-omentopexy group); in each instance, the procedure used was based on the preference of the senior clinician performing or supervising the surgery. The skin incisions were determined by the procedure chosen. In this series of cows, there were no difficulties encountered at surgery that required a change in the planned technique.
For each treated cow, age at the time of surgery, surgical procedure to correct the LDA, and most recent date of calving (to determine the interval from calving to surgery) were noted. The records were reviewed after the last treated cow left the herd (up to 4 years after the last surgery) to determine whether there had been any reoccurrence of LDA and the reason for culling from the herd for each treated cow. The dairy records of each treated cow were also examined to determine subsequent lactations and calving intervals. The herd records were examined to develop a list of reasons for culling of all animals that were in the herd during the 5-year period. The median time that the treated cows remained in the herd after surgery was determined for each treatment group. Cull rates were calculated for cows in each treatment group and the untreated herd mates.
Surgical techniques
All cows were treated surgically via a standing right flank laparotomy after establishment of distal paravertebral nerve blockade. Some cows received additional local anesthetic agent infiltration caudal to the last rib. Attempts were made to be consistent with regard to each surgical technique and the suture materials used. Potential variability was introduced by the experience of the senior clinician performing the surgery or experience of the surgical resident and level of supervision during the procedure.
The omentopexy technique has been described,7,8,10 and the approach is widely used for treatment of LDA, often with modifications of suture material and exact fixation techniques. In the cows of the present study, omentopexy was performed via a 20-cm vertical skin incision in the middle of the paralumbar fossa. The displaced abomasum was deflated with a 14-gauge needle attached by sterile tubing to a suction device. The deflated abomasum was then repositioned to the normal location by maneuvering it under the rumen. Gentle traction on the omentum in a dorsocaudal direction was applied to bring the pylorus into the field of vision.8 Three mattress sutures of size-2 polypropylene suturea were placed through the transversus abdominus muscle and peritoneum into the omentum approximately a hands-breadth from the pylorus and approximately 5 cm cranial to the incision. The peritoneum and transversus abdominus muscle were then closed in a simple continuous pattern that incorporated the omentum by use of size-2 polydioxanone suture.b The internal abdominal oblique and external abdominal oblique muscles were closed separately with the same suture material. The skin incision was closed with size-3 nonabsorbable suturec in a continuous interlocking pattern.
The pyloro-omentopexy technique was performed via a similar approach as that used for the omentopexy with the incision shifted cranioventrally on the flank just caudal to the last rib. The abomasum was deflated and repositioned as described for the omentopexy. The skin was undermined at the dorsal aspect of the incision in the dorsocaudal and dorsocranial directions over an area approximately 4 cm in width and 8 cm in length. Then size-2 polyglactin 910 suture materiald was used to place a suture through the muscular body wall into the omentum, with the pylorus at the ventral aspect of the incision, and back through the muscular body wall where it was tied. Size-1 polypropylene suturea was then used to perform the pyloropexy. The cranial body wall was reflected cranially so an interrupted suture could be placed near the ventral aspect of the incision. The suture bite was directed caudally to cranially through the peritoneum and transversus abdominus muscle at approximately 5 cm cranial to the body wall incision. The seromuscular layer of the pylorus was then pinched so the mucosa was not incorporated in the suture as it was placed in the cranial to caudal direction. Three of these sutures were preplaced approximately 2 cm apart before any were tied. Care was taken in tightening the knots to avoid bunching any of the peritoneum in the knot. Next, the omentum was tacked craniodorsally to the incision (earlier, it was in the caudodorsal position). The peritoneum and transversus abdominus muscle were closed in a continuous fashion (dorsal to ventral) by incorporating the omentum in the closure until reaching the level of the pyloropexy. The rest of the muscular body wall was closed with the same absorbable suture in 2 simple continuous layers. The skin was closed with size-3 nonabsorbable suturec in a continuous interlocking pattern.
Data analysis
Data were assessed for normal distribution with the Shapiro-Wilk test for normality. Ages at the time of surgery were normally distributed and are reported as mean ± SD. The median and range of age at the time of surgery, interval between most recent calving and surgery, and times from surgery to subsequent calvings as well as the number and proportion of cows treated with each procedure were calculated. A Wilcoxon rank sum (Mann-Whitney) test was used to test the hypothesis that age at the time of surgery was not significantly different between cows treated with pyloro-omentopexy or omentopexy. A Kaplan-Meier curve was used to graphically illustrate the times from surgery to first and second calvings among cows treated with each procedure. A log-rank test of equality across strata was used to compare variables between cows treated with each surgical procedure. Proportions of cows in the 2 treatment groups that had reoccurrence of LDA were compared with a Fisher exact test. Reasons for culling of treated and untreated cows (calves excluded) in the herd were recorded, and associated cull rates (percentage of treated cows and percentage of untreated cows in the herd that had > 1 lactation during the period of interest) were calculated. Analyses were performed with commercially available statistical software.e A value of P < 0.05 was considered significant.
Results
Over the 5-year period of interest, cows that developed LDA were treated surgically by 4 senior surgeons and 7 surgical residents. At the time of surgery, the mean (SD) age of cows that underwent pyloro-omentopexy was 3.74 (SD, 1.43) years and the mean age of cows that underwent omentopexy was 3.44 (SD, 1.47) years. The mean ages of cows in the 2 treatment groups were not significantly different (P = 0.318). The median interval between the most recent calving and surgery for the omentopexy group was 12 days (range, 2 to 30 days); the median interval for the pyloro-omentopexy group was similar (15 days), but the range was 2 to 326 days (P = 0.011). The interval from the most recent calving to surgery was > 30 days for 14 of the 58 (24.1%) cows in the pyloro-omentopexy group.
All the treated cows survived to be discharged from the clinic. After surgery, 56 cows (21 [72%] that underwent omentopexy and 35 [60%] that underwent pyloro-omentopexy) completed at least 1 subsequent lactation. Of those 56 cows, 32 had 2 subsequent lactations, 16 had 3 subsequent lactations, and 1 had 4 lactations after surgery. The median time to the first postoperative calving was 413 days (range, 328 to 522 days) for the 21 cows in the omentopexy group and 409 days (range, 331 to 551 days) for the 35 cows in the pyloro-omentopexy group (Figure 1). These median times did not differ between the 2 treatment groups. For the 32 cows in both treatment groups (14 that underwent omentopexy and 18 that underwent pyloro-omentopexy) that had > 2 calvings after surgery, the median time from surgery to the second postoperative calving was 811 days (Figure 2). For the 16 cows in both treatment groups (6 that underwent omentopexy and 10 that underwent pyloro-omentopexy) that had > 3 calvings after surgery, the median time from surgery to the third postoperative calving was 1,212 days. The median time that the treated cows remained in the herd after surgery was 566 days (range, 24 to 1,838 days); there was no significant difference in median time in the herd after surgery between the 2 treatment groups.
Review of records up to the point when the last of the 87 treated cows left the herd (ie, January 2001 through December 2009) revealed 15 reasons for cows leaving the herd. In the period under review, the herd had included 785 untreated cows as well as the 87 treated cows (calves excluded). Sixty-one percent of the treatment cows and 60% of the untreated cows had been culled from the herd because of lameness attributable to foot or limb problems, reproduction failure, or mastitis. Foot- and limb-associated lameness resulted in the culling of 24 of the 87 (28%) treated cows and 172 of the 785 (22%) untreated cows in the herd. The cull rate for reproductive failure was 21% for the treated cows (18/87 cows) and 21% for the untreated cows in the herd (164/785 cows). The cull rate for mastitis was 13% (11/87 cows) for the treated cows and 17% (133/785 cows) for the untreated cows in the herd. There was a reoccurrence of LDA in 4 of the 29 (14%) cows in the omentopexy group, whereas none of the 58 cows in the pyloro-omentopexy group had a reoccurrence of LDA (P = 0.011).
Discussion
In the present study, 87 cows with LDA underwent pyloro-omentopexy (n = 58) or omentopexy (29) over a 5-year period. Four senior surgeons and 7 surgical residents performed the surgeries. Although a difference in surgical experience may have contributed to the LDA reoccurrence rate or postoperative productivity among the cows, that factor was not evaluated. For example, the level of supervision given by the senior surgeon on each case was not documented in the records adequately for us to derive any meaningful information retrospectively.
Although the university dairy farm used in the present study is a commercial dairy, the authors acknowledge that the teaching and research components of the university make this a different entity in many ways from private commercial dairies, complete with different financial pressures and labor and efficiency issues as well as culling criteria that affect all aspects of management. However, the university dairy farm did provide an environment where data could be collected from cows that were under the same management practices, as opposed to comparing data from cows from several dairies. Many of the cows in the pyloro-omentopexy group were additions to the herd purchased specifically for a research project; many of these purchased cows did not have as desirable genetic traits as the typical cows in the herd. These purchased cows may have been predisposed to LDA because of the research protocol, which included diet modifications during the lactation cycle. Although difficult to definitively determine, the purchased cows were also subject to different culling pressures after the research was completed because of their less desirable genetic traits.
The higher number of cows treated by pyloro-omentopexy (many toward the end of the study period) was simply due to personal preferences of the surgeons treating the cows. Many of the cows in the pyloro-omentopexy group that were treated near the end of the study were part of the aforementioned research protocol. With regard to time from the most recent calving to development of LDA, many of those same cows were in the higher end of the range (2 to 326 days after calving), which we believe was a consequence of the research-related diet modifications. A lower percentage of cows in the pyloro-omentopexy group had at least 1 calf after treatment, which again we believe was at least partially a consequence of the higher number of cows on the research protocol. Having been purchased for research purposes and having less desirable genetic traits made them more likely to be culled after the research project was complete.
Other reviews of cows treated for LDA have included shorter follow-up periods (often to evaluate completion of the lactation or rebreeding)9,14,17,19 than that of the present study, which followed cows to the time of culling from the herd. The previous studies9,14,17,19 also involved many farms rather than one and were therefore affected by many differences in management. We are not aware of any previous study that compared cows treated by omentopexy or by the pyloro-omentopexy technique used in the present study and that followed the cows on 1 farm until they left the herd. The cull rates and reasons for culling among the cows with LDA in the present study were similar to those among the other cows in the herd during the period of interest. There were no significant differences in the examined variables between the omentopexy and the pyloro-omentopexy groups with the exception of the reoccurrence rate of LDA; 14% of cows in the omentopexy group had reoccurrence of LDA, whereas none of the cows in the pyloro-omentopexy group had reoccurrence of LDA.
In a previous retrospective study,26 the reported LDA recurrence rate when catgut suture was used for the omentopexy in 315 cows was 4%. One could speculate that the higher than expected recurrence rate of LDA in the present study was attributable to several factors, including a relatively small sample of cows from 1 farm, suture materials used, modifications of fixation technique, experience of surgeon, and extent of senior clinician supervision. In all 4 affected cows, the reoccurrence of LDA was 2 years after the omentopexy; all of those cows completed the lactation cycle after surgery with another uneventful calving and lactation before reoccurrence of the LDA after the second postoperative calving. One of the cows in the omentopexy group that had a reoccurrence of LDA also had signs of abomasal ulcers. The cow was euthanized, and the postmortem examination revealed no signs of adhesions from the omentopexy. Three of the cows that had a reoccurrence of LDA underwent a second surgery. One cow had no sign of adhesions; the other 2 cows had omentopexy adhesions that had stretched to allow displacement of the abomasum. With regard to the second omentopexy procedures, there were no comments in the cows' medical records of any intra-operative complications or the animal being overly fat. The procedures were done by surgeons in training, and the level of supervision was not documented. One might speculate that the suture material used in the present study may not have stimulated the same inflammatory reaction as that associated with suture materials historically used for omentopexy. In the experience of one of the authors (ANB) at 3 other institutions over a period of 16 years, reoccurrence of LDA in cows treated by omentopexy is not uncommon. We do not have case numbers with which to calculate an LDA reoccurrence rate in cows treated by omentopexy but we would not be surprised if it exceeded 4%. One could also speculate that some mature cows may have been culled for other reasons before a reoccurrence of LDA or were lost to follow up in a previous study,26 whereas the cows in the present study were in a university herd, under different culling pressure, and followed until leaving the herd.
The pyloro-omentopexy technique has been described8,10,27 but appears to be done in the field with modifications by many practitioners. In the experience of one of the authors (ANB), observed surgeries in the field have involved incision of the skin in the middle of the paralumbar fossa and transabdominal placement of pexy sutures. The sutures appear to have been placed blindly rather than following direct visualization of the pyloric antrum and possibly included more than the seromuscular layer. That author's students have reported observation of this modification when visiting practices. The modifications may contribute to the complications related to pyloro-omentopexy. The technique described in the present report has not been associated with reoccurrence or other complications in our experience.
In the present study, there were no noted complications associated with the pyloro-omentopexy technique used. We believe the complications associated with the pyloro-omentopexy technique may be more related to modifications of the technique or location of the body wall incision rather than the suture placement to secure the pyloric antrum to the body wall. Indeed, although this technique is not difficult to perform, it may be easier to accomplish after directly observing the procedure than after reading written instructions.
The results of the present study indicated that cows with LDA treated with either pyloro-omentopexy or omentopexy can be expected to have productive lives comparable to those of unaffected herd mates. There were fewer recurrences of LDA in cows treated by pyloro-omentopexy as there were in those treated by omentopexy. There were no complications associated with the pyloro-omentopexy technique used in this group of cows.
Acknowledgments
Presented in part as a poster at the XXVI World Buiatrics Congress, Santiago, Chile, November 2010.
ABBREVIATIONS
LDA | Left displaced abomasum |
Footnotes
Prolene, Ethicon Inc, Somerville, NJ.
PDS II, Ethicon Inc, Somerville, NJ.
Supramide Extra II, S. Jackson Inc, Alexandria, Va.
Vicryl, Ethicon Inc, Somerville, NJ.
Stata, version 11.2, StataCorp, College Station, Tex.
References
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