PRODUCTION ANIMALS

PRODUCTION ANIMALS

Surgical and postoperative events during permanent fistulation of sheep rumen by the Schalk and Amadon method Z Durmic,a* P McGrath,b M Wilmot,c N Adams,c T Tan,d L Callahand and C Mayberrye

Objective To describe and report on the course of events during and after surgical fistulation of sheep rumen by the Schalk and Amadon method and on improvements to address current trends in animal health, care and welfare. Methods A permanent re-entry fistula was created in 13 sheep using a method in which a fold of rumen is exteriorised and held by a metal clamp. Following surgery, sheep were monitored daily for any abnormalities for 4 weeks, then weekly for 6 months. Results Permanent fistulation was achieved in all 13 sheep; 2 sheep had minor complications: one during the surgery (rumen perforation) and one on the day after surgery (slipping of the metal clamp), but both recovered within 48 h with treatment. Over the 4 weeks post-surgery, 7 sheep had mildly elevated rectal temperatures, which resolved with non-steroidal anti-inflammatory drugs, systemic antibiotics and/or topical antiseptic cream. There was an 8-day variation among sheep in the time from surgery to creation of the fistula. Conclusion Rumen fistulation of sheep by the Schalk and Amadon method, as described here, is a comparatively simple, safe and ethical procedure, with minimal effect on or complications for the animal. Keywords fistulation; rumen; sheep Aust Vet J 2015;93;234–239

doi: 10.1111/avj.12343

uminants have evolved to consume large quantities of fibrous plant material and rely heavily on microbial breakdown of this food in the rumen and reticulum. Rumen content is a complex mix of feed, water, fermentation products and living organisms such as bacteria, fungi and protozoa, which varies over time and with different feedstuffs. As it is impossible to replicate this complex system in the laboratory, much research of ruminant nutrition is done in vitro using samples of rumen fluid collected fresh from living sheep. Rumen fluid can be obtained from live sheep by stomach tube or from animals that have had a permanent rumen fistula created surgically and then fitted with an intraruminal cannula. The latter method is preferred, particularly when repeated sampling is necessary,

R

*Corresponding author. a School of Animal Biology M085, The University of Western Australia, 35 Stirling Hwy, Crawley, Western Australia 6009, Australia; [email protected] b PO Box 687, Victor Harbor, SA, Australia c CSIRO Agriculture Flagship, Floreat, WA, Australia d Animal Care Services M720, The University of Western Australia, Crawley, WA, Australia e Research Services M459, The University of Western Australia, Crawley, WA, Australia

234

Australian Veterinary Journal Volume 93, No 7, July 2015

as it reduces contamination of the sample with saliva and provides a more representative sample of the rumen fluid.1 Three methods of surgical fistulation of the sheep rumen have been described. In the ‘one-stage method’, under general anaesthesia, the rumen is approached through the left paralumbar fossa and the cannula is inserted through an incision and held in place by a purse-string suture.2–5 It requires multiple sutures, antibiotics and anti-inflammatory agents. In the ‘two-stage method’, an incision is made through the skin of the paralumbar fossa under local anaesthetic, the underlying musculature is blunt-dissected to expose the rumen and a suitable area of the serosal surface of the rumen is sutured directly to the internal surface of the skin of the left paralumbar fossa using multiple sutures.6,7 The skin incision is closed and 1 week later the cannula is surgically inserted through the skin–rumen wall complex. An antibiotic is required. The third method was first described by Schalk and Amadon8 for cattle, and then modified for sheep by Hecker.9 Done under local anaesthetic, a fold of rumen wall is exteriorised through the left paralumbar fossa and clamped tightly between two metal bars, which causes the rumen to adhere to the abdominal wall while occluding the blood supply to the fold. When the fold necrotises and sloughs, a completely healed fistula between the lumen of the rumen and the outside is created.10,11 There is little published data on the comparative safety or efficacy of the three methods. Among the complications reported with the onestage method, one study that showed 1/19 sheep developed postoperative sequelae and died,5 1/14 sheep had excessive leakage5 and 1/8 expelled the canula;4 however, another study reported no major complications in 10 sheep.12 One study of the two-stage surgery reported 1/10 sheep with suture rupture, wound dehiscence and the cannula too loose to stay permanently in place.6 The original 1969 Hecker reference reported 3/71 sheep with ruminal herniation9 and a later study that was done in 32 pregnant ewes had limited documentation on any complications during or after the surgery.13 The Schalk and Amadon method is rapid, can be done under local anaesthetic, does not require extensive medication or intensive postoperative care and results in less adverse outcomes. The risk of peritonitis is greatly reduced (unpubl. obs.), because the ruminal fold sloughs after complete adhesion of the rumen to the abdominal wall, minimising the opportunity for direct exposure of the peritoneal cavity to ruminal contents. Animals are reported to recover quickly and resume their normal activities immediately after the surgery.9 In the past 4 decades, to our knowledge, more than 400 sheep have been successfully fistulated in Australia using the Schalk and Amadon method. During this period, individual researchers have developed some modifications and improvements, with some of these listed in © 2015 Australian Veterinary Association

their organisational standard operating procedures, but the only published descriptions of this procedure that we have been able to locate are the original 19699 and 1980 references.13 The objective of this report was to provide a comprehensive description of the surgery and document some improvements since the original reference was published. In addition, we report on postoperative monitoring, care and complications related to the surgery. Materials and methods Animals, diet, housing and general preparation This study was approved by The University of Western Australia Animal Ethics Committee (RA/3/100/1171). The 13 Merino wethers (age 18 months, average body weight 52 ± 5.3 kg, average body condition score 2.5) were sourced from the university’s Allandale Research Farm, at Wundowie, Western Australia, and brought to the Shenton Park Research Facility in late December 2012 for 2 months of acclimatisation prior to surgery. They were maintained on sprinklerirrigated, grass-dominant pasture and supplemented with lupin grain (100 g/head/day) and lucerne hay (ad lib). At 2 weeks before surgery, the animals were individually penned indoors on slatted floors and fed a daily mixed ration of 1 kg oaten chaff, 250 g lupin grain, 25 g mineral/vitamin mix (Mac M mix, Macco Feeds, WA, Aust), plus 200 g of lucerne hay each afternoon. They had free access to water via individual nipple-drinkers. On the day the sheep were introduced to the pens, a fresh faecal sample was collected from the floor from each pen for nematode egg count and all 13 sheep returned a negative test result. At the time of surgery, in late February 2013, the animals were clinically assessed as being in good health and weighed 59 ± 4.3 kg, with an average body condition score of 2.5 Surgical preparation On the day before surgery, each sheep was given a 5 mL intramuscular injection of multivitamin B (B-Complex Injection®, Troy Laboratories Pty Ltd, NSW, Aust). A 10 × 10 cm area of each animal’s left flank (3 cm behind the last rib and 5 cm below the lateral lumbar processes) was clipped and shaved. To facilitate location of the rumen, and to avoid fistulation of the wrong part of the gastrointestinal tract, the animals were not fasted prior to surgery. On the day of the surgery, sheep were brought singly to the operating theatre, placed in right lateral recumbency and gently restrained with manual pressure on the head and hip. Their eyes were covered with a clean towel to avoid further stress. The surgical area was washed once with 4% chlorhexidine gluconate solution (Chlorhex-S®, Jurox Pty Ltd, NSW, Aust) and twice with povidone iodine (BD E-Z ScrubTM surgical scrub brush, BD Australia, NSW, Aust). Analgesia was induced by local anaesthetic (Lignocaine 20, Ilium Veterinary Products, Aust) injected subcutaneously and intramuscularly around the anterodorsal portion of the flank in an inverted ‘L’ pattern.14 Analgesia was confirmed by lack of a twitch response to gentle pricking of the skin over the surgical site with a sharp needle. Surgery A skin incision 4–5 cm long, positioned 6–7 cm from the last rib and 5–6 cm from and parallel to the spine was made using a sterile scalpel (Figure 1a). The subcutaneous fascia and muscle tissue were then separated by blunt dissection to reach the abdominal cavity. The © 2015 Australian Veterinary Association

peritoneum was grasped with rat-tooth forceps, tented and incised. A fold of the rumen wall was then grasped and raised with Allis forceps, palpated between finger and thumb to confirm it was rumen and not caecum, and exteriorised through the incision in the abdominal wall (Figure 1b). A metal clamp (custom-made, consisting of two round, stainless steel rods 130 mm long and 5 mm thick, each fitted with two sets of holes drilled 25 mm from the end, with the holes in one rod threaded to take 3 × 28 mm long brass screws, Figure 1c, d), similar to that described by de Waal et al.,13 was applied over the exteriorised rumen fold (Figure 1c) and tightened to completely occlude the supply of blood to the fold (Figure 1d). One suture (Vetafil® 0.3 mm, DLC Pty Ltd, VIC, Aust) was threaded in through the skin on one side of one end of the clamp, under the serosa of the rumen wall, back out through the skin on the other side of the clamp and tied over the clamp to help prevent it being dislodged (Figure 1e). Each animal was given an intramuscular injection of 0.5 mg/kg body weight of non-steroidal anti-inflammatory drug (Metacam® 20 mg/mL solution for injection, Boehringer Ingelheim Pty Ltd Animal Health Division, NSW, Aust) immediately after the surgery and again 2 days later.

PRODUCTION ANIMALS

PRODUCTION ANIMALS

Postoperative monitoring, care and cannula insertion Each sheep was returned to its individual pen immediately after surgery and monitored for 4 weeks. The surgical wounds were evaluated daily for signs of swelling, bleeding, irritation, infection or impending sloughing of the exteriorised rumen fold. Rectal temperature was measured twice daily. Any sheep that had a rectal temperature ≥40°C was given an additional intramuscular injection of 0.5 mg/kg Metacam®, plus 20 mg/kg oxytetraycline (Engemycin®, MSD Animal Health, VIC, Aust). Topical antibiotic (Tricin Powder®, Jurox Pty Ltd) was applied to any surgical sites showing a significant discharge. Jarrett-type cannulae9 (flexible rubber sheep cannula, 62 mm long, 85 mm wide inner flange, 35 mm wide outer flange, 25 mm wide internal diameter; Nepean Rubber Mouldings Pty Ltd, NSW, Aust) were prepared by partially folding and pushing the inner flange through the cannula neck. The folded cannula was then thoroughly lubricated with a gel (Ultrasonic Gel, Virbac Animal Health, NSW, Aust). As the occluded rumen fold detached, or within 2 h of detachment (Figure 2a), the fistula was cleaned (Figure 2b) and gently stretched as necessary, using digital pressure or by gently, but firmly, inserting a lubricated barrel from a 20-mL syringe (Terumo Australia Pty Ltd, NSW, Aust). The cannula was then inserted through the fistula (Figure 2c) and the inner flange was carefully unfolded inside the rumen. A custom-made, rigid, Perspex ring was fitted over the neck of the cannula to secure it.14 The cannula bore was closed with a rubber bung secured with two 18G × 40 mm hypodermic needles (Figure 2d). All animals were given another intramuscular injection of 0.5 mg/kg of Metacam® immediately after insertion to alleviate any pain or discomfort. At 10 days after the insertion, each cannula was gently removed by cutting it longitudinally with strong scissors, folding and pulling it through the fistula. Superficial necrotic tissue around fistula site was wiped off with gauze swabs (Handy Gauze Swabs®, Smith & Nephew Pty Ltd, VIC, Aust) and a new cannula was inserted. Any local inflammation or heavy discharge was cleaned daily with a debriding agent (Ilium Oticlean Solution®, Troy Laboratories Pty Ltd) and treated topically Australian Veterinary Journal Volume 93, No 7, July 2015

235

PRODUCTION ANIMALS

PRODUCTION ANIMALS

a

d

b

c

e

with an antiseptic cream (Savlon Antiseptic Skin Healing Cream®, Boots Healthcare Australia Pty Ltd, NSW, Aust). After inspection of the cannula, any excess wool was clipped away from the fistula and both the cannula site and adjacent wool was sprayed weekly with an insecticidal spray (Clik®, Novartis Animal Health Australia, VIC, Aust). After this, long-term care and maintenance of the cannula involved checking that the bungs were in place (daily); closer examination of the cannula, bung, and fistula for signs of leakage, necrosis, inflammation or infection of the skin around the fistula and spraying with insecticidal spray (weekly); removing, washing and refitting the Perspex ring and clipping the wool if necessary (monthly); and replacing worn-out cannulae (yearly or as required). Results All 13 sheep were successfully fistulated and cannulae inserted. However, during the surgery of one sheep, a small, full-thickness tear of the rumen was noted after the Allis forceps were removed. As it could not be definitively ascertained whether the perforation

236

Australian Veterinary Journal Volume 93, No 7, July 2015

Figure 1. Surgical procedure. Horizontal skin incision 4–5 cm long, positioned 6–7 cm from the last rib and 5–6 cm from the spine (a); rumen wall exteriorised through the opening (b); metal clamps fitted over the exteriorised rumen wall (c); bolts tightened to occlude blood supply (d); suture was placed to secure the clamps (e).

occurred before or after the clamp was fitted, and hence whether any rumen fluid had leaked into the peritoneal cavity, this animal was given an intramuscular dose of 20 mg/kg Engemycin®. All animals (including the one with a rumen tear) resumed their normal behaviour (i.e. alertness, feed and water intake) within a few hours of being returned to their pens. On the day after surgery, the clamp on one sheep was seen to have slipped and some of the rumen fold had retracted into the abdomen (Figure 3). Although only the tissue above the clamp was becoming necrotic, the size of the rumen fold that was left clamped was considered to be too small to allow later insertion of a cannula. Accordingly, the animal was given local anaesthetic as before, placed in right lateral recumbency, the surgical area was disinfected as before, the clamp was loosened and carefully repositioned around a greater fold of rumen wall. The clamp was retightened and further secured with three sutures, making two at each end, through the skin and over the clamp. The animal was given further intramuscular injections of 0.5 mg/kg Metacam® and 20 mg/kg Engemycin® and returned to its pen where it was dosed orally with 500 mL of rumen fluid from © 2015 Australian Veterinary Association

PRODUCTION ANIMALS

PRODUCTION ANIMALS

c

a

d

b

a donor sheep and 100 mL Vytrate Liquid Concentrate® (Jurox Pty Ltd) to assist recovery. As this sheep was inappetent over the next 2 days, it was offered lucerne hay, small amounts of lupin grain and rose petals to stimulate its appetite. The animal resumed normal behaviour and food intake after 2 days. At 7–15 days post-surgery, some rumen fluid appeared on each animal’s left flank and the necrotised rumen fold sloughed, complete with the attached clamp. The fistula sites were cleaned and checked for patency and absence of unsealed areas, cuts or other lesions. All sheep required some stretching of the fistula hole © 2015 Australian Veterinary Association

Figure 2. Rumen fluid appearing on the flank and the necrotic fold falling off (a), fistula hole after cleaning (b), insertion of cannula (c) and cannula inserted and fitted with Perspex ring, bung and securing needles (d).

before the first insertion of the cannula, but the second insertion of the cannula, 10 days later, did not require any further stretching. All 13 sheep maintained their body weight in the first week postsurgery and then steadily gained weight at 100 g/day. During the 4 weeks following surgery, 10 sheep had elevated rectal temperatures (>40°C), which returned to normal within 24 h of administration of an intramuscular injection of 20 mg/kg Engemycin®. In six cases, the elevated temperature occurred within Australian Veterinary Journal Volume 93, No 7, July 2015

237

PRODUCTION ANIMALS

PRODUCTION ANIMALS

cannula; because the fistula was so narrow, we were concerned that some of the tissues may have been devitalised during stretching. Nine sheep had a significant amount of white, creamy discharge (Figure 4). Although bacterial culture yielded a heavy growth of mixed bacteria, no pyogenic bacteria were isolated. In order to reduce the bacterial burden on the wound and enhance the healing, these nine sheep were each given an intramuscular injection of 20 mg/kg Engemycin®.

Figure 3. Clamp slipping in one sheep on postoperative day 1.

During weeks 5–7 post-surgery, when the sheep had been returned to their paddock, all but one showed some degree of white-green, smelly, sticky discharge around the fistula site, associated with some physiological remodelling of the fistula and responding within 7 days to a single treatment of debridement with Ilium Oticlean Solution® and topical application of Savlon Antiseptic Skin Healing Cream®. At 10 weeks post-surgery, the fistula was completely formed in all 13 animals and clear of any superficial necrosis, discharge or irritation. All animals remained well and no further complications with the fistula sites up to 10 months after the surgery (at the time of preparation of this report) occurred. Discussion We confirmed that the Schalk and Amadon method is a simple, relatively straightforward method of creating a permanent rumen fistula for research purposes in sheep, offering multiple advantages over the one- and two-stage methods. No animals fistulated by this method have died as a direct consequence of the fistulation, whereas some animals died after being subjected to the other procedures.11 The method also avoids the complications attendant upon general anaesthesia in ruminants, such as the need for preoperative fasting, control of salivation, risk of inhalation pneumonia, hypoxia and hypercarbia,15 because it can be done under a local anaesthetic. Lack of preoperative fasting also facilitates location of the rumen and its discrimination from other abdominal organs such as the caecum. Healing and early physiological remodelling of fistula created by the Schalk and Amadon method is by second intention and the cannula is inserted once the granulation tissue has matured into a scar, as opposed to freshly cut tissue (one-stage technique) or young granulation tissue (two-stage technique). The only suture needed is to prevent the clamp slipping, which means there is less opportunity for sutures to break down and allow herniation, as implied by Hecker.9 The one suture used is simply removed with the clamp at the time of first cannula insertion,8 whereas with the other two procedures, there is a need to restrain the animals for suture removal.3 One concern with the method in pregnant ewes is that pressure from the pregnant uterus may impinge upon formation of adhesion between the rumen and the abdominal wall.13 For this reason, we propose that fistulation of pregnant ewes should not be performed.

Figure 4. White, creamy discharge from fistula site.

24 h of inserting the rumen cannula and in four when the cannula was changed. One sheep was given an intramuscular injection of 20 mg/kg Engemycin® at the time of first insertion of the rumen

238

Australian Veterinary Journal Volume 93, No 7, July 2015

We believe the elevated rectal temperatures we observed were related to general inflammation at the fistula site and the discharge was from commensal bacterial overgrowth on devitalised and superficial necrotic tissue. Because healing occurs by second intention, this is expected, but the systemic antibiotics and anti-inflammatory drugs that were given did appear to help the sheep to recover. Although we opted to administer these on an ‘as needed’ basis, the majority © 2015 Australian Veterinary Association

PRODUCTION ANIMALS

Convulsions that were observed occasionally during previous fistulation surgeries (prior to 2007) conducted in Western Australia were thought to be linked to vitamin B deficiency, because administration of vitamin B complex prior to surgery (2007 onwards) prevented the onset of convulsions during or after the procedure (unpubl. obs.). Many soils in Australia, especially those in the south-west of Western Australia, are deficient in cobalt, which often leads to vitamin B12 deficiency in grazing sheep.6 Clinical signs, which include inappetence, anaemia and failure to thrive,17 can be alleviated by adding cobalt to pasture fertilisers, by supplementing the sheep with cobalt in the form of an intraruminal bullet or by regular injections of vitamin B.15 Thiamine-responsive polioencephalomalacia also occurs sporadically in sheep in south-western Australia.16 Therefore, erring on the side of safety, especially in similar areas where vitamin/mineral deficiencies are suspected, we recommend that animals receive vitamin B complex prior to the surgery. However, there is a possibility that convulsions also occur because of accidental intravenous injection of some of the local anaesthetic and associated overdose.14,18 As a precaution, it is important not to exceed the toxic dose in sheep (i.e. 10 mg/kg by local infiltration) and to draw back on the syringe each time before infiltration to ensure that lignocaine is not being administered directly into a blood vessel. We observed a significant variation among the sheep in response to the surgery. The fistula site is ready for insertion of cannula when the rumen fluid starts to appear on the flank, and this varied from 7 to 15 days post-surgery, with majority of sheep becoming ready at day 11. This is at some variance to what was previously reported.10,11 We used soft rubber cannulae in preference to rigid ones, as they reportedly offer more flexibility and less irritation to tissue.19 They were well accepted and no significant gross changes such as ulceration or erosion were seen. The rigid, clear Perspex outer rings fitted to our cannulae12 restricted cannula movement well and we have had none dislodged. Also, because they are clear, they facilitate early detection of any abnormalities of the fistula site while sheep are in the paddock and the tighter contact with the wool and skin potentially prevents access to flies and reduces risk of flystrike at the fistula site. We have also found that securing the rubber stopper in the neck of the cannula with two hypodermic needles effectively prevents dislodgement of the stopper, which can be a problem when sheep are kept in the paddock where they may rub against fences (P. Cowl and K. Muthsam, pers. comm.). Finally, it should be noted that physiological remodelling of the fistula will continue for several weeks after the surgery and the wound should be allowed to granulate naturally to form a broad, strong scar. We therefore think it best to limit vigorous cleaning around the fistula site during this period.

© 2015 Australian Veterinary Association

Conclusion Rumen fistulation of sheep by the Schalk and Amadon method, with some modifications as described here, is a safe, inexpensive procedure, with minimal complications. Animals altered this way provide a longterm, readily available source of rumen content for research purposes. Acknowledgments

PRODUCTION ANIMALS

of the animals eventually were given treatment post-surgery. Therefore, it may be advantageous to administer systemic antibiotic to all animals immediately after the surgery as a prophylaxis.

We thank Peter Cowl, Keren Muthsam, Tom Riedel (UWA Animal Care Services), staff and students (UWA Animal Biology) for their help during the surgery and postoperative care of the animals, and all those involved in developing CSIRO SOP S.14. The study was part of DAFF/MLA-funded project ‘Efficient Livestock and Low Emissions (ELLE) from Southern Grazing Systems’. References 1. Shen JS, Chai Z, Song LJ et al. Insertion depth of oral stomach tubes may affect the fermentation parameters of ruminal fluid collected in dairy cows. J Dairy Sci 2012;95:5978–5984. 2. Dougherty R. Permanent stomach and intestinal fistulas in ruminants: some modifications and simplifications. Cornell Vet 1955;45:331–357. 3. Lamberth JL. A simplified technique for permanent rumen fistulation of cattle. Proc Aust Soc Anim Prod 1968;7:455–456. 4. Muzzi L, Muzzi RAL, Gabellini E. Técnica de fistulação e canulação do rúmen em bovinos e ovinos [Rumen fistulation and cannulation technique in cattle and sheep]. Ciênc Agrotec 2009;33:2059–2064. 5. Stedile R, Beck CAC, Nóbrega FS et al. Rumenostomia com colocação de cânula flexível em ovinos [Rumenostomy with placement of flexible cannula in sheep]. Acta Sci Vet 2008;36:35–38. 6. Azizi S, Pir-Mohammadi R, Pour-Hasani F. A two-stage rumen cannulation technique in sheep. J Anim Vet Adv 2007;6:29–32. 7. Jarrett IG. The production of rumen and abomasal fistulae in sheep. J Council Sci Ind Res Aust 1948;21:311. 8. Schalk AF, Amadon RS. Physiology of the ruminant stomach (bovine): study of the dynamic factors. N Dak Agric Exp Station Bull 1928;216:5–63. 9. Hecker JF. A simple rapid method for inserting rumen cannulae in sheep. Aust Vet J 1969;45:293–294. 10. Godwin IR, Chaffey GA. Simple rapid method of rumen cannulation. Aust Vet J 1988;65:227–228. 11. Stoddard GE, Allen NN, Hale WH et al. A permanent rumen fistula cannula for cows and sheep. J Anim Sci 1951;10:417–423. 12. Elices Mínguez R, Revuelta Rueda L, Martínez-Darve J et al. Surgery technique for ovine ruminal cannulation. Rev Comp Cienc Vet 2010;4:41–52. 13. de Waal HO, Engels EAN, Biel LC. A note on the insertion of rumen cannulae in pregnant ewes. South Afr Tydskr Veek 1983;13:264–265. 14. Taylor PM. Anaesthesia in sheep and goats. In Pract 1991;(Jan):31–36. 15. Judson GJ, Babidge PJ. Vitamin B12 injection for preventing cobalt deficiency in lambs. Aust Vet J 2002;80:777–778. 16. De Ridder T, Hollingsworth T. Thiamine deficiency induced polioencephomalacia (PEM) of sheep and cattle. PEM Farmnote, DAWFA, 2012. 17. Rammell CG, Hill JH. A review of thiamine deficiency and its diagnosis, especially in ruminants. NZ Vet J 1986;34:202–204. 18. Morishima HO, Pedersen H, Finster M et al. Toxicity of lidocaine in adult, newborn, and fetal sheep. Anesthesiology 1981;55:57–61. 19. Harmon DL, Richards CJ. Considerations for gastrointestinal cannulations in ruminants. J Anim Sci 1997;75:2248–2255.

(Accepted for publication 28 July 2014)

Australian Veterinary Journal Volume 93, No 7, July 2015

239

Surgical and postoperative events during permanent fistulation of sheep rumen by the Schalk and Amadon method.

To describe and report on the course of events during and after surgical fistulation of sheep rumen by the Schalk and Amadon method and on improvement...
1MB Sizes 25 Downloads 7 Views