BRISTLY GRUBS: Have you ever found a grayish, bristly larvae on the bottom of a water fountain or water bucket in the pen or paddock? These are usually over an inch long and about as big around as a good-sized earthworm, (actually 30x8mm, to be technical about it!). They’re light gray in color, have bristles or spines on the underside of their body and alternating cross-bands of darker pigment on the upper side. If you’ve found any creature that meets this description, it likely was the nasal bot of sheep, the latin name of which is Oestrus ovis.1 The life cycle of this parasite starts when a female fly of the Oestrus ovis species hovers in front of a sheep, takes aim, and literally squirts tiny (2mm) white larvae at the sheep’s nostrils. The larvae that hit the target enter the nasal cavity, feed on mucus and cells, enter the sinuses and, after 2-10 months of further growth and maturation, return to the nostrils as the above-described nasal bot and are sneezed to the earth or into the water source. The nasal bots pupate for about a month, and adult flies emerge (in the spring, in the temperate zone) and thus continue the life cycle. You’ve undoubtedly seen sheep shake their head and drop it abruptly lower when confronted by other bugs—gnats and biting flies—but they really go bananas when the Oestrus ovis flies confront them. The sheep stamp their feet, run for shelter, and position their nose in tall forage or under the bellies of flockmates. This frantic behavior interrupts their feeding activity and their sense of well-being. Infected sheep often have persistent discharge of mucus from the nostrils, which they may snort and sneeze out at intervals. Treatment with ivermectin at 50 micrograms per kg body weight should be done during the autumn, when the larvae are small.1 Treatment in winter or spring may cause inflammation in the sinuses.

CLOUDS OF CULICOIDES: In mid-summer, there may be veritable clouds of small flies (gnats) swarming about in late evening and after dark. One species of these small flies, Culicoides varipennis in North America, attacks sheep on pasture or in open pens, each female fly engorging a blood meal from sheep every 3-4 days.1 If the ingested blood contains the bluetongue virus (BTV), the female fly may become contaminated with the virus and support virus replication within its body. After 7-10 days, the bluetongue virus is excreted in saliva from the fly, potentially infecting a susceptible sheep as the fly takes another blood meal. Cattle and wild ruminants are less susceptible to bluetongue disease than are sheep and deer, but all serve as reservoirs of BTV from which it may be transmitted by Culicoides to other susceptible ruminants. After a few days of high fever, infected sheep have reddened membranes of the soft tissues of the mouth (sometimes the tongue is bluish-tinged, thus the name), and reddening of the skin of the face and of the skin just above the hooves, the latter being causative of lameness. The face may also be swollen and puffy and, later, there may be erosions and hemorrhages in the mouth, loss of hoof parts, stiffness, and weakness. Separating sick sheep from the flock reduces competition for feed, and permits the giving of supportive treatments. If susceptible ewes are infected (or vaccinated with attenuated Strain 10 virus) during weeks 4-8 of pregnancy, some of their lambs may have hydrocephalus and other lesions of the central nervous system. BTV is widely distributed, and the prevalence of the disease is variable from flock to flock and region to region. Prevention is aided by housing the sheep flock at night, because the Culicoides flies are reluctant to enter enclosed buildings, and by grazing them during daylight only. Low-lying wet areas, which favor the presence of Culicoides, should be avoided as habitat for sheep; rather, "keep ‘em on high ground!", particularly at night.

DEFORMED LAMBS: The finding of newborn lambs with hydrocephalus, deformed limbs, and other fetal and placental abnormalities may be evidence of a virus infection during the dam’s first trimester of pregnancy. One cause of such abnormalities is Cache Valley virus (CVV) infection of some of the ewes during mild weather early in pregnancy.2 CVV is widespread in North America, and the virus is capable of infecting many species, including humans. Fetal abnormalities appear primarily in sheep, and CVV infections of other species are usually asymptomatic.

SUMMER ACTIVITIES TO BENEFIT THE SHEEP FLOCK

Marry together the grazing program and body condition scores (BCS). Make it your plan never to be surprised by finding thin ewes (or rams) when you gather them before breeding in late summer or early fall. It takes a little effort, because you must put your hand on the sheep every so often during the grazing season.

First, know what the range of BCS is across the ewe flock when they go to grass. Knowing that range serves as a guide to the grazing plan. The end-goal is to have them all above BSCS 2 and, it is to be hoped, close to 3 when they enter the pre-breeding phase of your production program. If yours are heavy-milking ewes, which I hope they are, they are likely to be thin at weaning; indeed, many of them may be well below BCS 2. After keeping them on hard rations until udder involution is well-along, make your grazing decisions according to BCS data. If the range of BCS is greater than 1 unit (e.g., fairly uniformly spread across 1+ to 2.5+), divide the flock into lower and higher BCS sub-flocks and graze the thin sub-flock ahead of the better-conditioned sub-flock. As you lay your hand across the loin to determine the BCS of each ewe, gate-cut them into the two sub-flocks,———and I gotta’ say this, (be tough with yourself and the ewes), have a third pen for the ‘special cases’.

SPECIAL CASES

Examples of ‘special-case’ ewes are the occasional emaciated ewe, the ewe with major evidence of udder damage due to mastitis, those that were open during the last lambing season (they took away all the profit from seven ewes that did raise lambs!), the ewe that has a BCS above 3 (if she had a lamb, did it live?), the ewe with severely deformed hooves, the weak ewe that pants heavily or has paroxysms of coughing, and any other types that you want to include, based on your knowledge of your flock. And now (here’s the tough part), back up the trailer, load all of the special-case ewes, and sell ‘em! Now! Don’t pull any of them back because they’ve done well in the past! Refuse to honor the pretty face or the plaintive bleat! Send to pasture only those ewes that can nourish twins the next time around. You’ll be glad that you did.

BACK TO BUSINESS

Keep grazing the thinner sub-flock ahead of the better-conditioned ones for as long as it takes to get them up near 2.5. If it happens, merge the sub-flocks and graze on for the rest of the summer. If it doesn’t happen, adjust the flushing period so that the thinner ewes catch up before the rams are joined with the ewes. If the thinner ewes can’t catch up in spite of all of your special effort, including the use of an effective anthelmintic for all ewes in the flock, get different sheep. There are plenty of sheep out there that, given a well-planned parasite control program, can thrive on decent grass. Find them and let them work for you. Check around for sheep that are represented to do well on grass.

BCS OF RAMS, AND OTHER THINGS

Rams have received their share of attention in recent columns. Just don’t fall asleep on their BCS during the summer! Screen them for testicular and epididymal lumps at intervals. Schedule the breeding soundness examination before breeding season begins. Sure, it may take several repeated ejaculations to be assured that high-quality semen is in the pipeline, but it’s worth the effort. Why wait until all the ewes have cycled once before you have a breeding soundness examination done? Have feelers out for potential replacement rams/ram lambs, because you may need one or more in a hurry as breeding season approaches.

EWE LAMBS

How are the ewe lambs doing this summer? They’ve long since been separated from the ram lambs and wethers, I hope! And they had better not be grazing with the ewe flock, that’s for sure. If you are to improve your genetic base with those good rams that you’re so proud of, you’ll need well-grown, forage-adapted ewe-lambs to put them to. And if your strain of Suffolks is at the upper end of the size-range, you may choose to defer breeding them in their first year. It’s necessary to do risk-analysis before making that important decision. Check with your friends and with those who don’t like you and with those who have purchased replacements from yours or a closely-related flock. Compare the obvious advantages of having the ewe-lambs give birth at 12-15 months of age, on the one hand (i.e., more rapid genetic improvement), and the disadvantage, even the potential disaster, of having Suffolk ewe-lambs with high-prolificacy genes that break down metabolically during the third trimester. Late-pregnant Suffolk ewe-lambs that are still growing rapidly while gestating triplets may not be able to eat enough to avoid getting nudged over the line into pregnancy toxemia, nor to manage the Ca:P needs of their fetal lambs well enough to avoid deforming their own skeleton and even having spontaneous fractures. If your growthy Suffolk ewe-lambs are to be joined with the ram during their first year, fortify yourself with courage and take counsel with the wise heads in the industry.

PUSH THOSE LAMBS THAT ARE ON FEED

It’s July! Is it hot where you are? Are the wethers and the cull ewe-lambs still on the place? If so, are they eating well enough to meet your expectations for rate of gain? Do they have fresh water, shade, bunk space, and just plain space?

Good job! You’ve done well. Back to the hammock and your bottle of root beer.

REFERENCES:

1. Diseases of Sheep, 3rd Edition, by C.V. Kimberling, 1988. Lea and Febiger, Philadelphia.