Grazing lambs: Key considerations for successful weaning

Strong and steady lamb prices create an even stronger incentive to optimize weaning strategies for lambs born and/or raised on pasture.

Strong and steady lamb prices create an even stronger incentive to optimize weaning strategies for lambs born and/or raised on pasture. Setbacks at weaning can add weeks to lamb finishing programs, which are expensive in terms of both feed and facility costs. This article will outline the major issues to consider in optimizing weaning programs for lambs born and/or raised on pasture.

Age at weaning

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The decision of when to wean lambs raised on pasture is based on several factors, including:

  • Quality and quantity of pasture forage supply
  • Parasite contamination level of pasture forage supply
  • Necessity to add body condition to ewes before rebreeding.

Producers with small inventories of quality, low parasite-contaminated forage are best advised to wean earlier than those who have lots of “clean” pastures. Maintaining lambs on highly contaminated pastures is counterproductive, and it would be best to wean these lambs and place them in a feeding program if clean grazing options (hay field regrowth or annual crops such as forage turnips, rape, chicory, etc.) are not available. Dry ewes can continue to graze parasite-contaminated areas with far fewer issues than lambs. Weaning grazing lambs earlier than 45 days of age is not advised, as these lambs will suffer large growth setbacks, whereas 60 day old lambs are much more capable of making a relatively seamless weaning transition.

Ewes will regain condition quickly following weaning, since the high requirements of milk production will be gone. Thus, the ewe can redirect these nutrients to replenish lost body reserves. It is important to replenish these reserves prior to breeding to optimize ovulation rate for the next lamb crop. In my accelerated lambing flock, I wean lambs from lactating ewes on pasture 3 weeks before the next breeding season in order to allow time for the ewes to replenish body condition. A 2-3 week period is the minimal time needed if pasture alone is used to replenish condition. Annual lambing programs will have a much more forgiving time frame to replenish condition, but they still should not ignore this need.

Annual lambing programs with large inventories of relatively clean grazing ground may find it more economical to delay weaning until lambs are over 90 days of age. In summary, the decision of when to wean pasture-raised lambs should be based on the relative availability of “clean” grazing ground and the need to replenish maternal body condition prior to breeding.

Nutrition program

Abrupt dietary changes are to be avoided at weaning. Obviously, this is hard to do when weaning lambs off grass and transitioning them to a grain-based finishing program. There are, however, strategies available to ease this transition which cover three main areas:

1)      Allowing lambs to “learn” about grain consumption from their moms in the final weeks leading up to weaning

2)      Formulating diets that are high in fermentable fiber during the initial transition phase

3)      Allowing adequate time (7-14 days) to transition from a forage to a grain-based diet.

The learning phase (strategy one) can be done simply by feeding a mix of whole and/or relatively unprocessed grains on the ground in the 7-10 day period leading up to weaning. Feeding ½ pound of grain per ewe in long thin rows on short grass will allow lambs to pick up some of the grain and learn this feeding behavior from their moms. This training program can be done every other day or so in the final week prior to weaning. Lambs that learn about grain consumption from moms and other lambs retain this knowledge at weaning and will seek grain in feeders on the first day of weaning more quickly than those without previous exposure. This also minimizes problems of variable grain intake commonly encountered during the early weaning phase. Variable grain intake occurs when some lambs learn more quickly than others. The quick learners eat too much and get sick (acidosis or worse) whereas the slow learners don’t receive adequate nutrition. “Schooling” lambs in the pre-weaning period is a way to minimize this problem.

Another important strategy is to provide a “safe” grain diet in the transition period so that lambs do not consume excessive starch before their gastrointestinal tract is adequately adapted to handle a high starch diet. This can be done by substituting energy in the form of highly fermentable non-forage fiber (soy hull feed/pellets) for cereal grains that are high in starch (corn or barley). An example diet might contain an equal proportion of corn and soy hull pellets. This would allow lambs be exposed to starch while maintaining the safety of a highly fermentable, high-energy feed (soy hulls). Pasture-raised lambs that are allowed sudden, unlimited access to soy hull pellets would likely have only mild digestive disturbance, whereas those allowed sudden, unlimited access to corn or barley could easily die from enterotoxemia (overeating disease) and almost certainly would develop massive digestive disturbance and metabolic acidosis. Soy hulls either in loose or pelletized form have a fiber component similar to highly digestible quality forage, and therefore, lambs can make a more seamless transition to this energy source than they can to high starch energy sources (corn and barley). Many producers have found that maintaining a soy hull component in lamb diets (15-25 percent of diet dry matter) following the transition period is also beneficial in minimizing metabolic issues of lambs on full feed. The exact proportion in a finishing diet might be best chosen based on the commodity prices of soy hulls vs. corn or barley. Feed: gain will be slightly higher in a soy hull-based diet, but rate of gain will scarcely be impacted. Overall, the costs incurred by the higher feed: gain will likely be offset by the reduced incidence of metabolic disturbances.

The final nutritional strategy is to provide adequate time for diet transition. In practice it works well to provide unlimited access to hay during the early weaning period of a type and quality that is very similar to the pasture they had been consuming. It is very important to stimulate feed intake during this period, so providing forage that they are familiar with is especially helpful. An effective strategy is to take lambs directly off pasture and start them on a high percentage soy hull diet (70-75 percent soy hulls) offered free choice along with free choice quality hay. This transition can be done by filling self feeders with a diet that is 60 percent soy hull feed and 40 percent of the transition diet (which should contain 20-30 percent soy hulls already so the composition of this mix would be approximately 70-75 percent soy hulls) on day 1 and then gradually “pulling out” the added soy hull fraction over a 7-10 day period. In this way, the lambs are only eating the transition diet which contains 20-30 percent soy hulls at the end of the 7-10 day period. Transition periods to high starch-based feeds should be slower (up to 3 weeks).

It is important to monitor lambs closely during the transition period. The transition may need to slow down (less grain) if the incidence of diarrhea is too high (>10 percent of lambs). Adjustments to the speed of the diet transition program may need to be made along the way. Mild diarrhea is hard to avoid as the rate of passage of feed through the lamb’s body will be increasing as they consume a greater proportion of grain in their diet, but severe diarrhea is a clear sign to slow down. It is sometimes difficult to distinguish between nutritional scours and scours due to coccidiosis during the early weaning period, so a program for coccidiosis control at this time is important (as explained next).

Health program

The stress of weaning creates a very vulnerable time in life of the lamb. Weaning stress makes lambs very susceptible to coccidiosis and other stomach and intestinal parasites. The immune system of the lamb is compromised at weaning, which provides an opportunity for parasites to thrive. Accordingly, preventative and treatment measures are advised. Lambs weaned off pasture into the feedlot are notoriously susceptible to coccidiosis. Coccidiosis outbreaks can be controlled in these lambs by treatment with amprolium or sulfa drugs. These products can be administered by drench, in feed, or in drinking water. Administering these treatments in grain is a poor idea because grain consumption is low and variable. Amprolium is the product of choice for treatment if administered in drinking water, as it does not create a bitter taste like sulfa drugs. Amprolium, however, can also induce polioencephalomalacia in lambs if over-dosed, so the proper therapeutic dose much be administered. Sulfa drugs have the advantage of also controlling certain respiratory diseases, but I would advise against sulfa treatments in drinking water because it is important to maximize water intake during the transition period. Consult with a veterinarian on the use of either sulfa drugs or amprolium since their use in sheep is off-label. Coccidiostats should also be fed in grain diets during this period to prevent major outbreaks. Decoquinate (Deccox®) included in the total diet at 13.6 gallons per ton provides effective coccidiosis control. Coccidiostats are helpful, but care should be taken to provide adequate dry bedding, clean feeders, and waterers as part of a comprehensive prevention program.

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It is also very important to consider gastrointestinal nematode infection levels in lambs at weaning. Even at relatively low levels of infection, the stress of weaning can advance these infections quickly even when lambs are weaned into a dry lot. Caution must be given in prescribing a blanket treatment strategy for all sheep in a population with a deworming drug, as these practices will accelerate drug resistance. However, if there is one time when a blanket treatment is warranted, it would be at weaning in lambs exposed to contaminated pastures. It is becoming a more common practice to administer 2 or more of these drugs sequentially at weaning to ensure an effective treatment because this combination approach assures the best efficacy and minimizes build-up of larvae resistance to a single class of drugs.

Drugs chosen for combination therapy should represent different chemical classes. In the USA, there are approved drugs for sheep in the macrocyclic lactone family (moxidectin [Cydectin®] is generally the most effective in this class), one in the benzimidazole family (many members, only albendazole [Valbazen®] is approved for sheep) and one in the imidazothiazole family (levamisol [Prohibit®]). When applied correctly, this combination approach is highly effective and will eliminate gastrointestimal nematodes and tapeworms. The economic significance of tapeworm infection is debatable, but a single treatment of benzimadazole is generally highly effective. Efforts to minimize pasture infection with alternating grazing bouts of high-risk sheep (ewes and lambs) with lower-risk sheep (dry ewes), cattle, or machine harvest is also a critical point of control and must be practiced in high risk climates to minimize the need to use drugs. If a blanket treatment is chosen for weaned lambs, be sure to maintain other animals in the farm without treatment on these pastures to provide a refugia population. Generally speaking, only a fraction of the ewes will need to be treated at weaning, so leaving population ewes untreated will help to maintain a refugia population.

Vaccination of lambs against Clostridium perfringens types C and D is advised for lambs weaned off pasture and onto grain. It is thought that these lambs are particularly susceptible to enterotoxemia (overeating disease) because they have not consumed much starch in their diets and therefore have had little exposure to the toxins produced by the disease organism (which thrives on starch in the intestines). Low-level exposure of lambs to the deadly toxin is thought to confer some resistance. Effective antibody titers (blood concentration) will not exist until after the second booster injection (it is best to give booster 2 weeks following primary immunization), so even vaccinated lambs will experience a period of vulnerability, particularly if their mothers were not vaccinated.

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Adequate ventilation is also very important to newly-weaned lambs. They are prone to respiratory disease, so adequate air exchange is an important preventative measure. Good ventilation will also help dry the bedding and minimize the potential for coccidiosis outbreaks. Other facility considerations include waterers and feeders. It is critical that newly-weaned lambs consume lots of water at weaning, so it is best to provide the same type of watering troughs/tubs/tanks indoors as they had experienced on pasture for the first few days until they learn about the new indoor water sources. Feeder space should be ample to allow all lambs access to grain when they are being limit-fed.

Finally, care should be taken to avoid stressful handling and movement of newly-weaned lambs. Treat lambs calmly and gently at feeding and avoid disturbances. These lambs are accustomed to a pasture environment, and care should be taken to minimize stress as they adapt to an entirely new environment. Paying attention to the issues discussed here will allow your lambs to make a fast and safe transition during a stressful period.

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