33rd Annual Scientific Meeting proceedings

The exact diagnosis and causal therapy of milk flow disorders in cattle still frequently pose a challenge to this day (Stocker et al., 1989; Mösenfechtel et al. 2004; Kaiser and Starke 2020). In contrast to open teat lesions, which usually present few difficulties in clinical diagnosis, determining the cause of milk flow disorders due to obstructive teat lesions (covered teat lesions) is not always obvious. Teat sonography has led to a marked improvement in diagnosis, with the extent and location of stenosis being determined with greater certainty. In conjunction with teat examination including exploration of the teat cistern via the teat canal with a probe, sonography can be used to localize the stenosis obstructing milk flow to the location in the glandular cistern or annular ring, in the teat cistern or in the area of the teat canal.

Among cases of milk flow disorders referred to specialized clinics, lesions in the area of the teat canal are by far the most common, accounting for 76% (Bleul, unpublished data) and 89% (Kaiser and Starke 2020), respectively. These are most frequently due to mucosal detachment in the teat canal or at the internal teat canal orifice (Fürstenberg rosette) and significantly more often affect the posterior quarters of the udder (posterior right 38%, posterior left 33%; Bleul, unpublished data). Other causes of stenoses may be hematomas in the area of the teat canal or free foreign bodies, e.g., torn mucosa, acting like a ball check valve. In the case of stenoses located further proximal, septa or large tissue masses following inflammation and, in heifers, hypo- or aplasia of the udder and/or teat cistern are usually the cause of the milk flow disorder.

Despite the exact diagnostic possibilities, surgical removal of mucosal detachments in the bovine teat is still performed in practice mainly by methods introduced many decades ago (Hug, 1903). These surgical methods have in common that a cutting instrument (e.g., Hug's Bell, Ullner's curette) is inserted via the teat canal and any tissue to be removed is excised without visual control. Other instruments (e.g. teat knives, Hug's lancet, Danish double knife) are used to widen the teat canal by incisions so that the milk flow is restored past the stenosis (Roberts and Fishwick, 2010). Due to the unspecific therapy, milkability is often unsatisfactory and frequently leads to only short-term undisturbed milk flow. The consequences are either incontinentia lactis or scar retraction and a renewed reduction in milk flow, which often leads to a repetition of the therapy. Even though only about 50% of the treatments lead to undisturbed milkability (Frerking et al.,1974; Radmacher, 1980), this type of treatment is still frequently performed because of the low time and financial resources required.

In contrast, a thelotomy, in which the tissue leading to the stenosis can be removed under visual control after opening the teat wall, is performed less frequently nowadays because of the greater effort involved. After this method, undisturbed milkability was reported in 64% of cases (Rüsch, 1988).

Due to the advantageous anatomical conditions of the teat for keyhole surgery, teat endoscopy has been established for more than 2 decades for the treatment of trauma induced milk outflow disorders in cattle. To visualize the stenosis proximal to the teat canal, the rigid endoscope can be introduced atraumatically via the teat canal into the teat cistern. In case of mucosal detachments in the area of the teat canal or the Fürstenberg rosette, the endoscope must be introduced into the cistern after perforation of the teat wall due to the forward view optics of the rigid endoscope (lateral teat endoscopy).

Two methods for the removal of a mucosal detachment have become established to date. One involves inserting a punch into the teat canal to remove the detached mucosa under endoscopic control (Querengässer and Geishauser, 2001). Since this requires a surgical assistant, theloresectoscope was developed that combines the endoscope with a high frequency cutting electrode in one device (Hospes and Seeh, 1998a). This allows the surgery to be performed by one person only.

After local anesthesia at the affected teat, the flow of blood and milk is interrupted by tourniquet at the base of the teat and the teat is flushed with physiological saline solution. For a better overview, the teat is then dilated with distilled water or air, the latter being easier and faster to perform. After insertion of the theloresectoscope, the tissue to be removed is visualized and then removed with a loop-shaped coagulation electrode. Subsequent milkability is confirmed repeatedly using instilled physiological saline until milkability is undisturbed and the milk jet no longer scatters.

In the case of lateral teat endoscopy, the perforation in the teat wall is closed with one or more single sutures or staplers and the udder quarter is treated with antibiotics due to the significantly increased risk of mastitis. For surgeries in the area of the teat canal or the Fürstenberg rosette, a wax bougie is inserted into the teat canal and fixed with a teat bandage to keep the teat canal open and wide during the temporary drying off. In the following days, depending on the milk yield, the result of the bacteriological milk test and the milk cell count, the milk of the quarter should be drained several times through a teat cannula. After 10 days, stitches or clamps can be removed, and the quarter can be milked again. Unimpaired milkability at this time is primarily dependent on the location of the tissue leading to the milk flow obstruction. While surgery of stenoses in the glandular cistern, the annular ring or in the teat cistern lead to undisturbed milkability in only 43% of cases (Bleul, unpublished data), several studies reported undisturbed milkability after removal of mucosal detachments in the area of the teat canal or Fürstenberg rosette in 87-93% of cases (Seeh and Hospes, 1998b; Zulauf and Steiner, 2001; Bleul et al, 2005, Bleul, unpublished data). The good prognosis for this type of stenosis is often compromised by the occurrence of subclinical and/or clinical mastitis in the lactation in which the operation was performed. In the affected quarter, the risk of clinical mastitis is eleven times higher, and the detection of udder pathogenic bacteria is six times higher than in any other quarter of the same cow (Querengässer et al., 2002). Milk cell counts also remain significantly higher in the affected quarter than before injury until the next dry period, but there was no longer a difference between cell counts before injury and those in the next lactation (Bleul et al., 2005).

Thus, endoscopic removal of mucosal detachments leading to milk flow disorders is a low-invasive procedure with a favorable prognosis for restoration of milkability, especially for lesions in the area of the teat canal and Fürstenberg rosette. Targeted and intensive follow-up treatment is essential to avoid compromising udder health in the current lactation.

References

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