Diseases of the Periparturient Ewe

CHAPTER 92 Diseases of the Periparturient Ewe



Excluding the abortion diseases, the problems of the periparturient ewe often are metabolic and related to fetal number, nutrition, and management. With the advent of more prolific and productive sheep, the likelihood that the large animal practitioner will be called on to treat one of these various problems is high. As with many other diseases, the clinically ill animal may represent just the tip of the iceberg, and the challenge to the practitioner is determining whether the illness constitutes an isolated case or reflects a flockwide ailment.




ACIDOSIS


To compensate for the reduced rumen volume, most owners begin the feeding of concentrates to the ewes during the last trimester, but because of disparity in gestation and fetal numbers, intake among the ewes may not be equal. Some owners inadvertently feed too much to begin with or increase the amount too rapidly. Occasionally, ewes escape and find their way to a concentrate source. Rarely, an alternative feed, high in fermentable carbohydrates, such as bread or tacos, may be offered in too great a quantity. The same amount of a cracked, rolled, or ground grain may be substituted for the whole grain, which ferments much more slowly.




Treatment


Treatment is focused on returning blood and rumen pH to normal (7.4 and 6.5, respectively). Rumen pH varies according to the diet of the ewe. The rumen pH in ewes on forages ranges from 7.0 to 8, whereas that in ewes that have been on diets rich in carbohydrates for any length of time may be as low as 5.5. In a ewe on hay and a small amount of grain, rumen pH should be in the vicinity of 7.0. Intravenous administration of 2 to 4 L of bicarbonate (50 g/gal of water [313 mEq/L]) is in order if the blood pH is below 7.2; otherwise, oral medication usually is adequate. Calf electrolytes with bicarbonate such as Biolyte, Calf Quencher, Delyte H20K,§ Enterolyte, Resorb, or magnesium hydroxide** should be administered orally. Additional bicarbonate must not be added to electrolyte fluids, because sodium toxicity is likely to occur.


After administration of oral electrolytes, ruminal contents should again be tested for pH and further medication administered if necessary. Mineral oil can be given orally to promote rapid evacuation of the rumen, and an oral antibiotic such as neomycin or tetracycline given to reduce the activity of the fermenting bacteria. Flunixin meglumine†† injections (150–250 mg given intramuscularly) will make the animal more comfortable. Bicarbonate treatment usually has to be repeated in 2 to 4 hours, as determined by the amount of depression and results of another rumen tap.


A rumenotomy to remove the fermenting ruminal contents is the treatment of choice, particularly in severe cases; however, most owners balk at the cost of the surgery.




TRAUMA


In cold climates, frozen or muddy ground causes footing to be unstable. When scrambling to reach the feed bunk, aggressive agile ewes may cause other ewes late in pregnancy, heavy with multiple fetuses, to slip and fall. Ruptured round ligaments, fractured pelvises, torn stifle ligaments, and fractured femurs are not uncommon. Obviously, these ewes will be found “down.”


In such instances the ewe is bright and alert and will readily eat and drink. Her rectal temperature will be in the normal range. The complete blood count and blood chemistries are normal. A thorough examination of the rear legs, however, often will reveal crepitation or muscle fasciculation in the pelvic or thigh region.




HYDROPS


Hydrops allantois and hydrops amnion are not unknown in the sheep. Generally, by the time the veterinarian sees the ewe, her abdomen has become so enlarged that the animal can no longer support her weight and becomes a “downer.” Hydrops allantois is characterized by more rapid enlargement of the abdomen than with hydrops amnion and is more likely to cause rupture of the prepubic tendon. Determining which one of the two is the cause of the enlargement is difficult, however, and probably makes little difference in the outcome.





CALCIUM DEFICIENCY


In the bovine, calcium deficiency or milk fever is one of the most common problems of the period just before and after parturition, and low blood calcium is associated with many bovine problems after parturition. The ewe differs in that clinical hypocalcemia is relatively uncommon under normal conditions. When it is seen, however, it usually will be in large outbreaks. Up to 30% of ewes exposed to long-distance transport, experiencing sudden deprivation of food or feed supplying calcium, or grazing on oxalate-containing plants in late pregnancy may experience clinical hypocalcemia.


Because the calcium concentration is low in both grasses and concentrates, subclinical hypocalcemia may be an unrecognized factor in other periparturient problems when grass hay is used as winter feed.


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Sep 3, 2016 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Diseases of the Periparturient Ewe

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