Abstract
This study evaluated the long-term prognosis of return to normal mechanical milking after reconstructive teat surgery and determined the factors that have an impact on the outcome. A retrospective study of 67 dairy cows with teat lacerations was performed. Milking status at discharge and at long-term follow-up was adequate for 83% and 75% of the cows, respectively. No statistically significant differences were detected between the long-term prognosis and the age of the cow, the stage of lactation at presentation, or the configuration of the laceration. Lacerations repaired more than 24 hours after the trauma were more frequently associated with a negative outcome (P = 0.05). Mastitis was the most frequent complication (n = 17) and had a statistically significant negative impact on long-term prognosis (P = 0.02). Reconstructive surgery of lacerated teat in dairy cows can help establish return to normal mechanical milking.
Résumé
Évaluation du pronostic à long terme en regard de la traite mécanique des trayons lacérés réparés chirurgicalement chez la vache : 67 cas (2003–2013). Les objectifs de cette étude sont d’évaluer le pronostic à long terme, en regard de la traite mécanique, suivant la reconstruction d’un trayon lacéré et de déterminer les critères associés à un pronostic négatif. Une étude rétrospective sur 67 vaches laitières a été réalisée. La traite mécanique était adéquate pour 83 et 75 % des vaches à leur sortie de l’hôpital et lors du suivi à long terme. Pas de différences statistiques ont été trouvées entre le pronostic à long terme et l’âge des vaches, leur stade de lactation et la configuration de la lacération. Les lacérations réparées plus de 24 heures après le trauma avaient un pronostic moins bon (P = 0,05). La complication la plus fréquente était la mammite (n = 17). Elle avait un effet négatif sur le pronostic à long terme (P = 0,02). Reconstruire chirurgicalement un trayon lacéré peut rétablir la traite mécanique.
(Traduit par les auteurs)
Introduction
Teat lacerations are catastrophic injuries in dairy cattle. They are often self-inflicted when the cow stands, and can occur in tie stall or free stall barns. They have multiple configurations. If not repaired promptly, they can have serious consequences for the future of the animal. Mechanical milking of a lacerated teat is often impossible and the affected quarter becomes more susceptible to mastitis. Various surgical techniques have been described (1–4), with specific recommendations for the ideal suture material (5) and suture pattern (6–8).
Several authors have highlighted important prognostic indicators based on clinical impression. Early reconstruction seemed to be essential to achieve primary healing. Complex and transverse lacerations tend to have a poor prognosis since more blood vessels are severed compared to vertical lacerations. Finally, distal lacerations, in the proximity of or involving the streak canal, seemed to increase the risk of distal obstruction of the canal during the healing process (1–3). However, those prognostic indicators have never been validated. Therefore, the objectives of this study were to estimate the prognosis of return to normal mechanical milking after teat reconstructive surgery in dairy cattle and to determine the factors that have an impact on the prognosis. Our hypotheses are that the configuration, location, and delay between the laceration and the repair have an impact on long-term use of mechanical milking.
Materials and methods
Case presentation and laceration description
A medical record search was performed to identify cattle with teat lacerations that were presented to the veterinary teaching hospital between 2003 and 2013. Cows that had their teat amputated or that were not treated surgically were excluded. Data on age (older cow: ≥ 5 y old, younger cow: < 5 y old), breed and days in milk (0 to 30, > 30, dry period) of the cow were retrieved. The quarter affected, the depth of the laceration (partial or full thickness), the shape (vertical, transverse or complex defined as laceration in more than one direction), the length of the laceration (< 3 cm or > 3 cm), location (proximal, mid, or distal), and the involvement of the streak canal were obtained from the record. The time between the trauma and the surgery (< 12 h, between 12 and 24 h and > 24 h) was retrieved. If the trauma was not seen, the delay was estimated based on the last time the owner saw the teat intact. For example, a teat intact at one milking but injured at the other was classified as a laceration > 12 h old. On a dry cow, if the injury was not seen, the laceration was classified as > 24 h old. The presence of clinical and subclinical mastitis [Black plate, California Mastitis Test (CMT) and culture results] prior to surgery or in the post-operative period was also surveyed.
Pre-operative treatments and surgical procedure
The pre-operative treatments, aseptic preparation, local anesthesia, and surgical technique were reviewed. The cows received pre-operative systemic antibiotics [procaine penicillin (Pen G; Vétoquinol, Lavaltrie, Quebec), 22 000 IU/kg body weight (BW), IM, or ampicillin (Ampicillin; Novopharm, Toronto, Ontario), 10 mg/kg BW, IV], non-steroidal anti-inflammatory drugs [flunixin meglumine (Flunazine; Vétoquinol), 1.1 mg/kg BW, IV, or ketoprofen (Anafen; Merial, Baie d’Urfé, Quebec), 3 mg/kg BW, IV], and light sedation [acepromazine (Atravet; Boehringer Ingelheim, Burlington, Ontario), 0.05 to 0.1 mg/kg BW, IM, or xylazine (Rompun; Bayer, Toronto, Ontario), 0.05 mg/kg BW, IV], prior to being placed in dorsal or lateral recumbency on a custom made tilt table or in a hydraulic chute. Chlorhexidine was used to clean the teat as well as for the surgical scrub. Prior to the surgical scrub, a ring block was performed at the base of the teat using 2% lidocaine. The lacerated teat was first meticulously debrided using a combination of irrigation or hydropulsion (18-gauge needle and 30 mL syringe) with sterile isotonic saline, and sharp dissection (#10 or #15 blade) to remove all embedded organic particles and necrotic tissue from the wound. Then, a 3-layer closure was performed (for full thickness laceration). The first layer included the mucosa and submucosa, which were sutured with 3-0 to 5-0 polyglycolic acid (Dexon II; United States Surgical, Tyco Healthcare, Norwalk, Connecticut, USA) or polyglactin 910 (Vicryl; Ethicon, Somerville, New Jersey, USA) with a simple continuous (vertical laceration) or simple interrupted (transverse laceration) pattern. In 1 cow (proximal and transverse laceration), the teat mucosa could not be apposed appropriately. A 12-mm (outer diameter) silicone implant was inserted in the teat and gland cistern to avoid adhesions and excessive granulation tissue formation at the surgery site. It was sutured in place with 3 simple interrupted sutures using polydioxanone (PDS; Guaynabo, Puerto-Rico). The second layer, consisting of the muscular and subcutaneous layers, was sutured with 3-0 to 5-0 polyglycolic acid or polyglactin 910 with a simple continuous (vertical laceration) or simple interrupted (transverse laceration) pattern. Finally, the skin was closed with 2-0 or 3-0 polybutester (Novafil; United States Surgical) with a simple interrupted, cruciate, or horizontal mattress suture pattern. Teat inserts or indwelling cannulas were used for distal lacerations. The teats were bandaged immediately after surgery while the cow was still on the table. The skin sutures were removed 10 d after the surgery.
Post-operative treatments and complications
The post-operative treatments were reviewed. Every cow received an intra-mammary infusion of antibiotics [Cefa Lak (Boehringer Ingelheim), Spectramast LC (Zoetis, Kirkland, Quebec), or 1 g cefazolin (Teva Canada, Toronto, Ontario) diluted in 20 mL of sterile water] after surgery. The intramammary antibiotic therapy was repeated if evidence of clinical mastitis was observed (swelling, pain, macroscopically modified milk on black plate). Postoperative systemic antibiotics were administered for at least 3 d.
A cow was considered to have a fistula if she had a small diameter hole along the suture line that leaked milk. Cows that had tearing of the suture material through the tissue exposing the teat cistern were considered to have dehiscence (partial or complete). Cows were assumed to have teat cistern fibrosis if the teat was firm on palpation and did not fill up with milk when the quarter was manually stimulated.
Outcome
The number of days before mechanical milking was resumed was documented. The status of mechanical milking at discharge was retrieved and qualified as adequate, difficult, or impossible. Difficult mechanical milking was defined as a quarter taking more than twice the time needed for the contralateral quarter to empty. Since a slow quarter is very frustrating for the owner, it was considered as a negative outcome in the statistical analysis. Through a standardized telephone interview with owners performed at least 6 mo after the surgery, the long-term prognosis regarding the possibility of performing mechanical milking on the affected quarter (adequate, difficult, and impossible) was recorded. Questions were also asked regarding healing of the teat, the presence of mastitis, the number of lactations completed since the surgery and the reason for culling. Finally, through the Canadian Dairy Network database, the number of lactations performed after the trauma by registered cows was retrieved.
Statistical analysis
The prevalence of front quarters versus rear quarters was compared using a Z-test. Univariable analyses were then performed using a Chi-square test to evaluate the different criteria (Table 1) associated with long-term prognosis. Univariable associations with a P-value ≤ 0.25 were retained for further modeling. Final multivariable logistic regression models were built (GLIMMIX procedure in SAS) using backward elimination strategy until P-values of all remaining variables were ≤ 0.05. Finally, the milking status at discharge was compared with the milking status at long-term follow-up using a concordance test (kappa). All the statistical analyses were performed using statistical computer software (SAS v.9.4; Cary, North Carolina, USA).
Table 1.
Factors evaluated concerning long-term prognosis (mechanical status) of lacerated teat surgically repaired in 67 dairy cows in a referral center
| Mechanical milking status | ||||
|---|---|---|---|---|
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|
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| Factor | Definition (“n” available at follow-up) | Adequate (%) | Difficult or impossible (%) | P-value |
| Age | < 5 y old (n = 27) | 67 | 33 | 0.23 |
| ≥ 5 y old (n = 34) | 82 | 18 | ||
| Stage of lactation | < 30 d (n = 25) | 72 | 28 | 0.88 |
| ≥ 30 d (n = 18) | 78 | 22 | ||
| Dry (n = 4) | 75 | 25 | ||
| Quarter | Front (n = 40) | 70 | 30 | 0.22 |
| Rear (n = 21) | 86 | 14 | ||
| Time of repair following trauma | ≤ 12 h (n = 35) | 80 | 20 | 0.05* |
| 12 to 24 h (n = 11) | 81 | 19 | ||
| ≥ 24 h (n = 11) | 45 | 55 | ||
| Depth | Partial (n = 16) | 75 | 25 | 1.00 |
| Full (n = 44) | 75 | 25 | ||
| Configuration | Vertical (n = 7) | 86 | 14 | 0.85 |
| Transverse (n = 25) | 72 | 28 | ||
| Complex (n = 28) | 75 | 25 | ||
| Length | < 3 cm (n = 13) | 69 | 31 | 1.00 |
| ≥ 3 cm (n = 34) | 71 | 29 | ||
| Location | Proximal (n = 9) | 67 | 33 | |
| Mid (n = 13) | 52 | 38 | 0.39 | |
| Distal (n = 31) | 81 | 19 | ||
| Streak canal (n = 9) | 78 | 22 | 1.00 | |
| Time of first mechanical milking after repair | < 5 d (n = 30) | 80 | 20 | |
| ≥ 5 and < 10 d (n = 9) | 89 | 11 | 0.89 | |
| ≥ 10 d (n = 9) | 78 | 22 | ||
| Post-operative complications | Clinical mastitis (n = 17) | 53 | 47 | 0.02* |
| Fistula (n = 8) | 62 | 38 | 0.39 | |
| Dehiscence (n = 4) | 50 | 50 | 0.25 | |
Statistically significant difference.
Results
Sixty-seven medical records were reviewed. Sixty-three cows were Holstein, 3 were Ayrshire, and 1 was Jersey. The breed predisposition in this study represents the breeds of the farms surrounding the veterinary hospital. The mean age was 5.2 y (range: 2 to 12 y). After surgical reconstruction of the laceration, 83% (39/47), 8.5% (4/47), and 8.5% (4/47) of the cows had adequate, difficult, or impossible mechanical milking, respectively, at discharge from the hospital. Twenty cows were dry during their hospitalization or went home before being milked. At 6-month follow-up, 75% (46/61), 8% (5/61), and 17% (10/61) of the cows had adequate, difficult, or impossible mechanical milking, respectively, at the farm. Six cows were missing from the long-term follow-up because the owner could not remember the animal or retrieve their health record.
The milking status at discharge had a poor correlation with the milking status at the farm (κ = 0.07). The status changed from adequate to difficult for 7 out of 39 cows (18%) and from difficult or impossible to adequate for 6 out of 18 cows (33%). Therefore, 28% (13/47) of cows had their milking status change between the time of discharge from the hospital and the long-term follow-up.
Fifty-seven percent (38/67) of the cows were older than 5 y. Fifty-one percent (27/53) of the cows were < 30 days in milk, 38% (20/53) were > 30 days in milk, and 11% (6/53) were in their dry period. No statistically significant difference was detected between the older (≥ 5 y) and the younger cows (P = 0.23), and between the days in milk (0 to 30, > 30, dry) (P = 0.88) in regards to long-term prognosis (Table 1).
Most of the owners did not witness the traumatic event. Sixty-six percent (44/67) of the lacerations involved the front quarters. The front quarter was more frequently involved than the rear quarter (P = 0.01). However, there were no statistically significant differences between the front and the rear quarter in regards to long-term prognosis (P = 0.22) (Table 1). Time between the traumatic event and the surgical repair was less than 12 h for 61% (37/61) of the cows, between 12 and 24 h for 19.5% (12/61) and > 24 h in 19.5% (12/61) of the cows. Lacerations older than 24 h had a statistically significant worse long-term prognosis (P = 0.05) (Table 1).
Seventy-three percent (48/66) of lacerations were full thickness; 11% (7/66) were vertical, 42% (28/66) were transverse, and 47% (31/66) were complex. There was no statistically significant difference regarding the depth or the shape of the laceration in regards to long-term prognosis (P = 1.00 and P = 0.85) (Table 1). Twenty-nine percent (15/52) of lacerations were ≤ 3 cm in length, but this criterion made no statistically significant difference to the prognosis (P = 1.00) (Table 1).
Fifteen percent (9/58) of lacerations involved the proximal portion, 28% (16/58) involved the mid portion, and 57% (33/58) involved the distal end of the teat. The streak canal was involved in 30% (10/33) of distal lacerations. No significant differences in long-term prognosis were detected according to the location of the laceration or the involvement of the streak canal (P = 0.39 and P = 1.00) (Table 1).
All lacerations were reconstructed upon admission. Eight surgeons were involved. Four of them had prior surgery-oriented residency training. No statistical difference, in regards to prognosis, was found between surgery trained and non-surgery trained surgeons (P = 0.72).
In 18 cows, a plastic (Indwelling milk tube; Mai, Elmwood, Wisconsin, USA) or a custom made silicone cannula was inserted through the streak canal and sutured to the teat skin to allow passive milking. Three had a laceration involving the streak canal, 4 the distal teat, 8 the mid-section and proximal teat and in 3 cases the localization was unknown. The cannula was left in place for 1 to 5 d and was removed before resuming mechanical milking. The other cows had their teat passively milked with a single use plastic cannula at milking. In the 12 cows in which the laceration involved the distal portion of the teat (6 streak canal and 6 distal teat), a silicone teat dilator (SIMPL; Jorvet, Loveland, Colorado, USA) was placed in the papillary duct for a variable period of time (1 to 10 d). Overall, 82% of the lacerations involving the streak canal, 45% involving the distal teat and 33% involving the mid and proximal teat, had a cannula or a teat dilator after the repair.
Mechanical milking was resumed within the first 5 d after surgery in 62% (30/48) of the cases, between 5 and 10 d in 19% (9/48) of the cases and > 10 d after the surgery in 19% (9/48) of the cases. No statistically significant difference was detected regarding the time of first mechanical milking and long-term prognosis (P = 0.89) (Table 1). Fifty percent of the cows with a transverse laceration were milked with the machine > 5 d after the surgery, whereas only 17% and 30% of the cows with vertical and complex lacerations, respectively, were milked > 5 d after the surgery.
The most frequent complications were clinical mastitis (n = 17), fistula (n = 8), partial dehiscence of the incision (n = 4), fibrosis of the teat (n = 3), and dripping between milking (n = 3). Five of the 17 cows with mastitis were infected before the surgical repair. The presence of post-operative clinical mastitis had a negative impact on the prognosis (P = 0.02) (Table 1). The microbial agents cultured were Escherichia coli (n = 7), Staphylococcus aureus (n = 3), Pseudomonas aeruginosa (n = 2), and 1 each of Trueperella pyogenes, Streptococcus uberis, Streptococcus dysgalactiae, Klebsiella pneumoniae, and yeast. Ease of milking of 6 E. coli and 2 S. aureus infected quarters was adequate at follow-up. Ease of milking of all the other infected quarters was not satisfactory.
Two of the 8 fistulas were closed surgically and were doing well at follow-up. There were problems with 3 of the remaining cows at follow-up; 2 were dripping milk and had chronic clinical mastitis and 1 had a fibrotic teat and quarter from acute mastitis. The other 3 cows were being milked satisfactorily even with the fistula. The presence of a fistula did not have a statistically significant impact on long-term prognosis (P = 0.39) (Table 1). Delay before repair (≥ 24 h) (P = 0.01) and the presence of post-operative clinical mastitis (P = 0.02) had an impact on the prevalence of fistula. The factors associated with fistulae are presented in Table 2.
Table 2.
Pre-operative and post-operative factors associated with fistula, dehiscence, and fibrosis following repair of lacerated teats in a referral center
| Complications | ||||
|---|---|---|---|---|
|
|
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| Factor | Definition | Fistula (n = 8) | Dehiscence (n = 4) | Fibrosis (n = 3) |
| Age | < 5 y old | 2 | 3 | 3 |
| ≥ 5 y old | 6 | 1 | 0 | |
| Stage of lactation | < 30 d | 4 | 3 | 0 |
| ≥ 30 d | 3 | 0 | 1 | |
| Dry | 0 | 1 | 0 | |
| Quarter | Front | 7 | 2 | 2 |
| Rear | 1 | 2 | 1 | |
| Time of repair following trauma | ≤ 12 h | 3 | 2 | 3 |
| 12 to 24 h | 2 | 1 | 0 | |
| ≥ 24 h | 3 | 1 | 0 | |
| Depth | Partial | 1 | 2 | 1 |
| Full | 7 | 2 | 2 | |
| Configuration | Vertical | 1 | 0 | 0 |
| Transverse | 3 | 4 | 0 | |
| Complex | 3 | 0 | 3 | |
| Length | < 3 cm | 3 | 1 | 1 |
| ≥ 3 cm | 4 | 3 | 2 | |
| Location | Proximal | 1 | 2 | 0 |
| Mid | 1 | 1 | 1 | |
| Distal | 5 | 1 | 1 | |
| Streak canal | 1 | 1 | 1 | |
| Time of first mechanical milking after repair | < 5 d | 6 | 1 | 0 |
| ≥ 5 and < 10 d | 0 | 0 | 1 | |
| ≥ 10 d | 0 | 1 | 0 | |
Two of the 4 cows with a partial dehiscence were culled. The others were being milked satisfactorily at long-term follow-up. For those 2 cows, the dehiscence occurred during their hospitalization and was promptly repaired. Three cows with teat fibrosis were not being milked satisfactorily at follow-up. Two of them had post-operative clinical mastitis (S. uberis and P. aeruginosa).
In the multiple regression model, only the criterion “postoperative clinical mastitis” had a negative outcome at long-term follow-up (P = 0.03). The other criteria included in the model were age (P = 0.06) and time before repair (P = 0.11). Those criteria were chosen because they had the strongest impact (even if not statistically significant) on the prognosis in the univariable analysis.
It was possible to retrieve the milking records of 38 cows. Fifty-five percent (21/38) of them had at least 1 lactation following the trauma [median: 2 lactations (range: 1 to 4 lactations)]. Nineteen of those cows had a satisfactory milking status and 2 were difficult or impossible to milk at long-term follow-up. One of those 2 cows lost the operated quarter because of acute mastitis due to E. coli. She was kept as a 3-quarter cow and produced 12 555 kg of milk in 305 d. The other was kept although the affected quarter required a long time to be milked. She produced 10 015 kg of milk in 305 d.
Forty-five percent (17/38) of the cows did not complete their lactation or were culled at the end of their lactation. Seven of them were culled because the quarter was difficult or impossible to milk. Eight cows were culled with a functional quarter. Two of them had chronic mastitis in another quarter, 2 had udder suspensory ligament rupture, 1 had reproductive issues, and 4 were culled for unknown reasons unrelated to the surgery.
Discussion
Our primary objective was to evaluate the prognosis of return to normal mechanical milking of surgically repaired lacerated teat in dairy cattle. Our studies showed that 83% and 75% of repaired teats were being milked satisfactorily at discharge from the hospital and at long-term follow-up (> 6 mo after the surgery), respectively. However, a low kappa was obtained when a concordance test was performed to compare the mechanical status at discharge from the hospital with the status at follow-up. Therefore, the milking status at discharge did not ensure a similar status at the farm. Thirty-three percent of the quarters difficult to milk at discharge improved and 18% of the quarters that were milked satisfactorily at discharge became worse.
A second objective of our study was to determine the factors that had a significant impact on long-term prognosis. Factors such as configuration (transverse or complex), location (distal), or delayed repair have always been thought to have a negative impact on the prognosis. In our study, we were able to show that the time of repair after the trauma had an impact on mechanical milking. Lacerations repaired more than 24 h after the trauma were more likely to cause impossible milking of the quarter at long-term follow-up. Since the other factors did not have a significant impact on long-term prognosis, we had to partially reject our hypothesis. An interesting but not surprising finding was that the presence of post-operative clinical mastitis had a significant negative impact on the milking status at long-term follow-up.
Surgical site infection, in any tissue, has serious consequences on healing (9,10). Infection delays healing and can precipitate resorption of suture material, leading to total or partial dehiscence of the surgery site (5,11). In teat surgery, no study has looked at the effect of clinical mastitis on the healing of a thelotomy or a repaired laceration. Our clinical experience tells us that exuberant granulation tissue and adhesions frequently formed along the mucosa in face of clinical mastitis. Depending on the location or the size of the laceration, this tissue may or may not have an impact on milk flow. In our study, 2 cows with partial dehiscence of their repair had clinical mastitis. Five of the 8 cows that developed a fistula also had clinical mastitis. No bacterial cultures were performed on the incisions. However, it is highly suspected that they were infected which led to further complications. It is therefore important to diagnose clinical mastitis early by performing black plate analysis at every milking and doing bacteriological culture on positive results. These test results will allow prompt treatment of affected quarters with the appropriate medications. If pre-operative clinical mastitis is identified, using a suture material that retains its strength for a longer period of time might be indicated (5).
In our study, many microbial agents were isolated, with the main agents being E. coli and S. aureus. Interestingly, those 2 agents rarely caused complications at long-term follow-up compared with the other agents isolated such as T. pyogenes and P. aeruginosa. It is possible that early aggressive treatment (intra-venous fluids, intra-mammary antibiotics, non-steroidal anti-inflammatory drugs, and systemic antibiotics) combined with an E. coli lacking virulence factors (not evaluated in this study) were responsible for the lack of long-term negative effect on the teat. For S. aureus, it is possible that the intramammary antibiotic given was able to locally control the infection in the early phase of healing of the teat. In summary, it seemed that we were able to achieve clinical healing, not necessarily bacteriological healing, of clinical mastitis caused by E. coli and S. aureus, therefore, preventing further complications during the healing of the laceration. However, it seemed that we were not able to achieve the same results when T. pyogenes and P. aeruginosa were involved, explaining the higher rate of fistula and dehiscence when those 2 agents were isolated.
Repairing lacerations less than 24 h after the trauma did not have a negative impact on the long-term outcome. However, when the repair was delayed for more than 24 h, mechanical milking at long-term follow-up was more likely to be compromised. Similarly, a fistula along the laceration repair was more likely to be present. These results are in agreement with the study by Azizi et al (12) that showed that lacerations more than 24 h old were more at risk of developing a fistula. However, even if the prognosis is poor when the repair is delayed (45%), we believe the surgery should still be performed. It is easier to repair a fistula or a partially dehisced incision than to reconstruct a scarred and fibrotic teat cistern. As with quarters with clinical mastitis, a suture material retaining its strength for a longer period of time might be indicated for delayed repair attempt.
The configuration and location of the laceration had no impact on the prognosis. Seventy-two percent of quarters with transverse lacerations had adequate milk flow at follow-up. This type of laceration was thought to carry a poor prognosis since it compromises the vasculature more than vertical lacerations (1–3). Careful debridement and reconstruction combined with an extended rest from mechanical milking (50% were milked with the machine more than 5 d after the surgery) were probably key elements for a successful outcome. Even the cow that required a silicone prosthesis had successful healing and return to mechanical milking. However, because of the high morbidity rate associated with this implant, it should only be used when primary closure of the mucosa is not possible (13–18).
Distal lacerations or lacerations involving the streak canal were also thought to carry a poor long-term prognosis (1–3). These types of lacerations, because of the proximity or the involvement of the streak canal, are more susceptible to adhesions that could completely or partially obstruct milk flow. In our study, 80% of cows with a laceration involving the streak canal and or the distal end of the teat had satisfactory milk flow at long-term follow-up. Eighty-two percent of teats had a cannula or a teat dilator used during the postoperative period compared to only 33% of cows with a mid or a proximal teat lesion. This type of plug has been used to treat internal lesions of the streak canal with success (19–21). They were used in a similar manner for the distal lacerations which might have contributed to the positive outcome.
The only similar study published on teat lacerations found that older cows had more lacerations than younger cows and were more susceptible to post-operative complications such as fistula (12). The researchers found that lacerations occurred more frequently in the first month of lactation and that the front quarters were more frequently involved. The most frequent configurations were vertical since the lacerations occurred on pasture on barbed wire. In our study, the only similarities were the more frequent involvement of the front quarter and the stage of lactation when the laceration occurred. Age had no impact on the healing and older cows were not overrepresented. The most frequent configurations were transverse and complex. This difference could be explained by the different dairy cattle husbandry practices between our 2 countries. In North America, dairy cattle are mostly kept in tie stalls or in free stalls. Lacerations are self-inflicted (dew claws) or caused by a neighboring cow resulting in transverse and complex lacerations.
Our study involved a large number of cows with teat laceration. Like most retrospective studies, not all the needed information could be retrieved from the medical records or milking database thereby decreasing the power of our analysis. However, we were able to identify that delayed repair and post-operative clinical mastitis had a statistically significant negative impact on long-term prognosis and on the incidence of teat fistula. In face of clinical mastitis, the owner should be warned that the prognosis to re-establish mechanical milking from the injured teat is poor. An informed decision can then be taken, depending on the value of the animal, to pursue further treatment on the teat.
In conclusion, all types of lacerations can heal and allow mechanical milking with thorough debridement and careful reconstruction. Teat lacerations are emergencies and should be repaired as soon as possible. Clinical mastitis should be treated aggressively and clients should be warned of the risk of dehiscence and possible fistula formation. Finally, it is important to note that the mechanical milking status can change in the weeks following the repair. Therefore, a teat difficult to milk early after the repair should be given time to heal before being declared a failure.
Acknowledgments
The authors acknowledge Dr. Nicolas Tyson and Mme Josée Lemay-Courchesne for building the database, M. Guy Beauchamp for the statistical analysis and Dre Marketa Kopal for her linguistic help. CVJ
Footnotes
Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (hbroughton@cvma-acmv.org) for additional copies or permission to use this material elsewhere.
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