TRIAGE: That’s most familiar to us as a battlefield exercise engaged in by medical personnel, in which they categorize the wounded into three groups: those who will likely survive without treatment, those who will not likely survive even if treated properly, and those for whom treatment is likely to make a difference in their chances of survival. Shepherds use the triage principle often at lambing time, which, come to think of it, sometimes resembles a war-zone.

In this column, let’s talk about applying the triage principle in the larger sense, i.e., applying it to each decision that we make and each action that we take on behalf of our sheep flock. In that way, we may be able to choose more comfortably and realistically between what’s ideal and what’s doable. For example, it would be ideal that all lambs live and thrive, but that’s an unattainable goal in a flock of any size. Rather, the shepherd should, by triaging ahead of time, set the conditions within which as many lambs as possible can survive and thrive, given the best efforts ahead of lambing season. And now, to set the stage, let’s talk about germs.

WE’VE ALL HEARD ABOUT GERM-FREE MICE IN MEDICAL RESEARCH, BUT IS THERE SUCH A THING AS GERM-FREE LAMBS?: Come to think of it, there is! In fact, lambs that are normal at birth have been germ-free for nearly 150 days, ever since conception and throughout gestation. However, that changes during the last few minutes of the birthing process itself. Yes, there are always a few exceptions; notably, there’s the abortion diseases that infect the ewe first and then the fetuses, and premature dilatation of the cervix which permits bacteria to enter the uterus and kill the fetuses.

IT’S A PRIVILEGE!: Mammalian fetuses live and grow in a privileged environment within the uterus. The uterus is a place in which germs are not welcomed graciously, nor tolerated without a donnybrook. In a word, if germs get into the uterus, the outcome is often death for the germs or the lambs, and sometimes for the ewe as well. By having knowledge of the germ-free state that exists in the uterus for 142-148 days after successful mating, the shepherd can manage the pregnant ewe so as to help newborn lambs adjust to life in the unrelentingly hostile world outside the uterus. That adaptation process, which includes the development of the fetal immune system during the last half of gestations, is buttressed for several months after birth by antibodies from the ewe’s colostrum. Although their immune system is pretty competent at birth, lambs have an absolute requirement for colostrum to aid them in resisting bacteria and other microorganisms until the immune system is tuned up to produce resistance to germs that the lamb itself has encountered. The lamb’s immune system is fully on line several months after birthing. The pace and specificity of immune adaptation by the lamb can be positively influenced at several points from conception through puberty by management interventions on the part of the shepherd.

THE START OF NEW LIFE; A FURTHER DIGRESSION: After mating of ram and ewe, a spermatozoa penetrates (fertilizes) the oocyte (egg) as it is swept along the oviduct (Fallopian tube) into the uterus. The resultant embryo grows by cell division after fertilization, nourished by the fluid within the uterus. After 10-22 days from the time of mating, membranes (known collectively as the placenta) that enclose and protect the embryo begin to attach to the uterine wall (implantation). The growing embryo is thereupon known as the fetus, and the fetus is thereafter nourished by its own circulating blood, into which nutrients are taken up at the 70 or more placentomes that partition it from actual contact with the circulating blood of the ewe. The fetus grows to about 1/3rd of birth weight in the first 100 days of gestation, but more than 2/3rds of fetal growth occurs in the last 45 days of gestation. So the uterus is a privileged environment, indeed, and germfree to boot, as long as the ewe is healthy.

BACTERIAL CONTAMINATION OF THE UTERUS AT BREEDING, AND AGAIN AT THE BIRTH OF THE LAMBS: The privileged environment within the uterus, which is vital to fertilization of the egg and the normal growth and development of fetal lambs, is maintained at considerable biological cost to the ewe. For example, the mating event contaminates the ewes’ reproductive tract with bacteria, which must be removed quickly by the ewes’ white blood cells and other protective mechanisms so that the embryo will develop properly. The cervix, which separates the vagina from the uterus, contracts quite tightly after estrus. During pregnancy, the cervix is filled with a mucus plug that largely excludes bacteria from entering the uterus from the vagina.

Now it’s true that not every bred ewe has a germ-free uterus when she comes into heat. If there is pre-existing infection and inflammation of the uterine lining before the ewe comes into heat, conception may occur but the embryo may be killed within a few days or implantation may not occur properly. Such ewes may re-cycle and be bred again, with the same outcome, and such a ewe, if continually infected, may be barren at lambing time. Alternatively, if a ewe has a germ-free uterus when she comes into heat, the protective mechanisms may not rid the uterus of the germs that invariably contaminate it during the act of breeding, and the embryo may die as in the previous example. It’s reality that the uterine lining is repeatedly contaminated with germs during the life of the ewe. It’s also reality that the uterus has very effective mechanisms to rid itself of germs, as attested to by the 95%+ pregnancy rates that are often attained in some ewe flocks.

THE WORK IS FINISHED AND THE LAMBS HAVE BEEN DELIVERED, BUT THE UTERUS IS CONTAMINATED WITH GERMS ONCE AGAIN: Five months after conception, when the lambs are born, the uterus is again flooded with bacteria from the vagina, including bacteria and other organisms from feces, from the soil, and from the skin of the ewe. Once again, white cells and protective proteins from the blood aid in immobilizing and removing these bacteria. The outcome options are:

A. The germs are cleared away promptly, e.g., in a couple of weeks, vaginal drainage ceases, and the uterus is prepared for breeding when the ewe comes in heat again, or

B. The germs are not cleared away but remain in the uterus for weeks and contribute to a continuing or intermittent vaginal drainage that, with or without treatment, either ceases before the next breeding season or continues unendingly. Even if drainage ceases, the uterus is not necessarily a privileged environment for the embryo on the first estrus cycle, although it may become so subsequently as a result of the beneficial changes such as increased blood flow, entry of white blood cells, and muscular activity that accompany the estrus event. At the very least, those ewes whose vaginal discharge is still detectable at the next breeding season should be culled. Those that cease the vaginal discharge but are subsequently barren should also be culled. In either case, their inability to control uterine contamination and infection may be passed on to ewe lamb daughters that may be born if they are retained and bred successfully after their barren season. That’s known as throwing good money after bad, i.e., keeping a barren ewe, because by retaining them we have the opportunity to lose money on them twice instead of once! Talk about slow learners, I tell you!

THE MAIN EVENT: But the more urgent question is: What’s going on with the lambs that have just vacated their privileged environment? This is where we can make a real difference in profitably potential, by using the triage principle before the lambing season begins and after it ends, and by not working quite so hard during the lambing season.

THE LAMB’S TRANSITION FROM GERM-FREE STATUS TO BEING JUST PLAIN DIRTY: It is jokingly said that only two things in life are certain: death and taxes. There’s at least one other certainty, which is that every live-born lamb goes from germ-free status to being germ-laden in the twinkling of an eye during the birth process. As the ewes’ cervix relaxes to permit passage of the lambs, contamination of the lambs with germs—bacteria, fungi, even viruses— begins. By the time that the lambs’ nose and mouth are visible at the vulva, contamination of the facial skin, nasal cavity, and mouth is well along. When the newborn lamb breathes and swallows, organisms are delivered ever-deeper into the trachea and digestive tract. It’s inescapable, this germ-contamination process (and that’s why colostrum must be suckled by the lamb early and often) but there are at least three aspects of it that are worth remembering:

1. It’s not all bad, because it (contamination with germs) occurs mostly on three surfaces: a) skin, b) trachea and lungs, and c) mouth and digestive tract. Bacterial germs must usually attach to a surface in order to increase in numbers and harm the animal. Think of those surfaces (named above) as real estate available for rent; whoever arrives first has the best chance to live there. If non-pathogenic germs settle in on a surface first and increase in numbers, there’s less available surface for harmful germs to set up house-keeping. Pack the area with your friends, and exclude the bad guys!

2. Newborn lambs have virtually no antibody immunity; they depend on antibodies that are present in the dam’s colostrum. Need I say more? Probably not, but see below.

3. It’s possible for the shepherd to modify events so as to improve the newborn lambs’ chances for a healthy life, and that’s where our triage decisions come into their own:

· Nutrition; yes, good old nutrition!: The shepherd who feeds ewes appropriately for their phase of production and who develops and adheres to a target BCS score for each phase of the production cycle is doing the single most important thing to assure that as many healthy lambs as possible are born into the flock. Even a least-cost ration has to meet the requirements of both dam and fetuses. We can’t expect good outcomes with poor nutrition!

· Shepherds can exclude specific disease-causing germs (e.g., those associated with foot-rot and epididymitis) from the flock by carefully purchasing replacement ewes and rams that are free of these disease.

· Vaccinate ewes several weeks before the time of birthing, to enhance antibody protection against germs that colostrum confers to newborn lambs. At minimum, protection against enterotoxemia and tetanus should be enhanced by vaccination with Clostridium perfringens type C and D bacterin-toxoid and tetanus toxoid (or a combination product). This is the basic vaccination program for sheep flocks in the U.S.

· Shear ewes or crutch them before lambing season begins, to minimize the lambs’ oral intake of germs from manure in the fleece and to maximize the lambs’ chances of finding a clean nipple.

· Allow ewes and ewe-lambs to give birth unassisted to the extent that your nerves will allow. Require the ewes to demonstrate their maternal characteristics! Don’t do as one shepherd did: He personally assisted all 50 of their ewes to deliver their lambs every year. I think that he was selecting for a ewe flock that would need more and more birthing assistance as the years went by.

· Strip out the teat plugs so lambs can suckle effectively, but don’t waste colostrum—The lambs need every drop.

· Give ewes and their newborn lambs privacy for 4-6 hours following birthing. If the lambs’ belly isn’t distended with colostrum by that time, tube the lamb, give 4-8 ounces, and check the lambs again in 4-6 hours. Use sheep colostrum if possible and adult cow colostrum if necessary. Time of colostrum ingestion is of the essence; the lambs’ intestine takes the antibody proteins into the lambs’ bloodstream on a scale of efficiency that declines steadily after a few hours and closes off permanently at about 16-18 hours after birth. In the absence of properly-timed intake of good-quality colostrum, there is increased risk of invasive infections known as septicemia, often caused by certain strains of E. coli. Septicemia in a colostrum-deprived lamb, or in a lamb that didn’t get colostrum in a timely manner is likely to be fatal, even with drug treatments.

· Make the birthing area as dry and draft-free as possible. If it’s cold or chilly and the ewe doesn’t lick the lambs dry, it’s your job to towel them off. After all, it was your decision to have them born in cold weather! Be prepared to put jackets on them if it’s really, really cold, and then reevaluate your production goals and decide whether or not you want to continue jacketing lambs every year. If not, change your production goals.

· Lamb the ewes out on pasture to reduce the amount of manure in the birthing area and to limit early contact with other sheep; lacking that, cover the birthing area with dry straw and use jugs to limit contact with other sheep and lambs.

· Move ewes and lambs as quickly from jugs as possible to less crowded mixing pens.

· Colostral immunity is quantitative; the more that is absorbed by the intestine, the better the lamb is protected. Older ewes have more and better-quality colostral antibody than do ewe-lambs. See, there is something good about being old!

· Colostral (passive) immunity degrades steadily because the antibody proteins are metabolized (broken down) in the lambs’ tissues over time. Passive immunity is largely lost by 2-3 months of age.

· Good news! The lamb is capable of making its own protective antibodies at birth, but it takes some weeks to do so efficiently enough that it can ‘go it on its own’. That’s what passive immunity is for; it’s the bridge across the troubled water of early life. Antibodies are made in response to germs that enter the lambs’ bodies or against vaccines that are injected into them. Thus, the same vaccines that have been given to the ewe flock (C&D&T) are given to the lambs in a series of 2-3 doses, beginning at 8-10 weeks of age. That series of vaccinations, given at that age, brings about specific immunity that can be maintained by yearly boosters.

· Germs that cause diarrhea usually make their presence known within a day or two after birth (E. coli and rotavirus), after several weeks (salmonella), and after weaning (coccidia). Cleaning and liming the jugs, prompt manure removal from all areas where ewes and lambs are held, vaccination for E. coli, and using chemical coccidiostats in the feed are strategies to minimize or avoid these scour problems.