A complex problem with many contributing factors
A rectal prolapse is when a portion of the rectum protrudes outside the anus. It is easy to recognize. The exposed tissue is usually a bright, cherry red (at first). Eventually, the exposed tissue becomes dry and cracked, causing more irritation and straining.
If left unattended, a rectal prolapse can become a life-threatening condition and a cruel way for an animal to die, as untreated animals may prolapse their entire intestinal tract and go into shock.
Sheep of any breed, age, or sex may be affected. Ewe lambs that prolapse should not be retained for breeding, as they are more likely to prolapse their vaginas at lambing. Prolapses occur less often in goats than sheep. Prolapses can occur in other livestock and humans as well.
Correction may be cost-prohibitive in feedlot lambs and immediate slaughter is usually recommended for market lambs. For more valuable animals, treatment may be successful. If the prolapse is mild, it may be possible to wash and lubricate the exposed tissue and replace the prolapse. It may help to suture the rectum partially shut, but this is usually only a temporary fix.
For more severe cases, a prolapse ring (or short piece of hose) can be used to repair the prolapse. The ring is placed in the rectum and an elastrator band is placed around the area to be amputated. The lamb may need a couple of ounces of mineral oil or another mild laxative each day to keep the feces soft. Antibiotics should be given to prevent infections.
Causative (Risk) Factors
Rectal prolapses are a complex disease condition in sheep. Many factors have been proven or suggested as causative factors: sex, age, condition, diet, tail dock length, coughing, chronic scours, and implanting. It is usually a combination of these factors which causes rectal prolapes in sheep and lambs.
Ewe lambs are more likely to have a rectal prolapse than wether lambs. Females lay down more internal fat, particularly in the pelvis. When a lamb strains or coughs, fat can't hold the rectal tissue and hind gut in place. Thus, most prolapsing lambs are female, regardless of other risk factors. Fat ewe lambs are most prone to prolapsing.
Rectal prolapses occur most commonly in feedlot lambs and other lambs being finished on high concentrate diets. Overly fat lambs are more prone to prolapsing.Lush clover and other legume pastures have also been implicated as a cause of prolapses. Estrogen found in these plants may cause relaxation of the vaginal-rectal muscles.
While Ralgro® (zeranol) implants are not widely used in the U.S. sheep industry, their use has been associated with increased incidence of rectal prolapse in feedlot lambs, especially ewe lambs. Ralgro® is an anabolic agent with estrogen-like activity.
Lambs in the post-weaning period are more likely to experience a rectal prolapse than young lambs or adult sheep.
Chronic coughing, due to infection or dusty feeds, may lead to an increased incidence of rectal prolapses. Continuous coughing often results in protrusion of the rectum, and if left attended, just gets worse.
Coccidiosis and other causes of diarrhea are associated with increased incidences of rectal prolapses. Diarrhea causes irritation and straining, which may cause prolapsing in susceptible lambs. Coccidiosis can be prevented with good management and the use of coccidiostats (Bovatec® or Deccox®) in the feed or mineral.
It is believed that some lambs have a genetic predisposition to rectal prolapses. However, in the scientific literature, there is only one estimate for heritablity of this trait: 0.14. Lambs with a genetic predisposition, especially ewe lambs, are more likely to prolapse if other risk factors are put into play. Blackface lambs tend to be more affected by rectal prolapses than whiteface lambs.
Short tail docking
Several studies have implicated short-tail docks as a cause of rectal prolapses in lambs fed high-concentrate diets. When tails are docked too short, the muscles attaching to the tail bone are weakened. Short tail docks (< 0.7 in.) also result in an increased incidence of flystrike (maggots) as compared to properly docked lambs.
Examining the link between tail dock length and the incidence of rectal prolapses
Tail dock length has become a contentious issue in the U.S. sheep industry, as show sheep are docked significantly shorter than most commercial sheep and sheep in other countries. A multi-state, cooperative study (2003) was undertaken to study the current issue of tail dock length in docked lambs and its relationship to incidence of rectal prolapse.
A total of 1,227 lambs at six locations (in Texas, Ohio, Oregon, Iowa, and Wisconsin) were randomly allocated to two or threetail dock treatments: 1) short - tail was removed as close to the body as possible; 2) medium - tail was removed at a location midway between the attachment of the tail to the body and the attachment of the caudal tail folds; and 3) long - the tail was removed at the attachment of the caudal tail folds to the tail.
In the study, short-docked lambs (7.8%) had a higher incidence of rectal prolapse than lambs with a long (1.8%) or medium (4%) dock. Female lambs (6.0%) had a higher incidence of rectal prolapse than male lambs (3.1%). In the study at the Ohio Agricultural Research & Development Center (OARDC), short-docked lambs in the feedlot had a higher incidence of rectal prolapses than short-docked lambs on a pasture diet. In the study at Oregon State University in which most of the lambs were raised on pasture, only one lamb experienced a rectal prolapse. This study implicated short tail docking as a cause of rectal prolapses in feedlot lambs, but not pasture-fed lambs.
In an earlier study conducted by the University of Minnesota over a 2 year period, 23 out 288 short-docked (1/2 inch dock) lambs (8%) prolapsed their rectums, compared to only 1 long-docked (3 inch dock) lamb. However, year-to-year differences were also observed. In 1988, only 2 lambs prolapsed, whereas in 1999, 22 lambs prolapsed, suggesting the important contribution of environmental factors to the incidence of prolapses. Like the mullti-state study, these lambs were fed a feedlot diet.
Only one lamb prolapsed in a five-state study (2005, in Utah, Idaho, Ohio, Arizona, and West Virginia) in which 784 lambs were docked at the distal end of the caudal tail fold. The research showed that there was a 91.8 percent chance that a lamb's tail will stay the same or grow longer between weaning and market when docked at the distal end of the caudal tail fold and is a 98.5 percent chance that it will stay the same or grow longer between docking and market. According to the study, there is a 99 percent probability that lambs docked at 1 inch will arrive at market at 0.7 inch or longer. 0.7 inches is the requirement for 4-H lambs in some states.
More recently, a study was conducted at Texas Tech University (2006) , utilizing 382 lambs of various breeds and breed crosses. Tail docking treatments were the same as those used by the multi-state study: short, medium, and long. Treatments were randomized among breeds, sex, and birth type. All lambs were fed a high concentrate diet in a feedlot environment.
In this study, the incidence of rectal prolapses was only 2.1 percent and did not vary among the three docking treatments. As in the multi-state study, female lambs had a greater incidence of rectal prolpases than male lambs, accounting for 6 out of the 8 prolapses. While this study is in conflict with the multi-state study, it does not eliminate short docks as a cause of rectal prolapses, it merely demonstrates that there other factors that must be considered.
The American Sheep Industry Association (ASI), American Veterinary Medical Association (AVMA), American Association of Small Ruminant Practioners, and various other animal industry groups all recommend that lambs be docked no shorter than the distal end of the caudal tail fold. In the United Kingdom, it is a law that lambs be docked so that the tail stub covers the vulva on a ewe and be an equivalent length on a male lamb.
Tips for preventing rectal prolapses in lambs
Rectal prolapses can largely be prevented with good feeding and management practices.
Dock wooled lambs no shorter than the distal end of the caudal tail fold.
Don't overfeed, especially ewe lambs.
Don't feed dusty or moldy feeds.
Prevent coccidosis with good management and use of coccidiostats in the feed or mineral (Bovatec® or Deccox®)
Don't keep rams that sire lambs that prolapse.
Don't retain ewe or ram lambs that prolapse.
Don't implant ewe lambs.
Don't finish ewe lambs in a feedlot.
Consider raising lambs on pasture or including forage in the feedlot diet.
Limit legume content of pastures, to less than 50 percent.
Feed balanced rations.
References and further reading
[PDF] Causes, prevention, and treatment of rectal prolapse in sheep - North Dakota State University
[PDF] Effects of sex, breed, callipyge phenotype and docked tail length on rectal prolapse in lambs - Sheep & Goat Research J.
[PDF] Length of docked tail and the incidence of rectal prolapse - J. Anim Sci
Rectal prolapse - Ask-a-sheep Vet
Rectal prolapse - Merck Veterinary Manual
[PDF] Rectal prolapse in lambs - The Judging Connection
Rectal prolapse - Pipestone Veterinary Services
Tail length of docked lambs and rectal prolapse - Ohio Sheep Team
[PDF] Using the DeTail device to address tail docking in show lambs - West Virginia University
[PDF] Welfare implications of tail docking of lambs - AVMA
This article was written in 2006 by Susan Schoenian.