Grazing: Early weaning can help good pasture management. Weaning, by definition, creates two different flocks with wildly different nutritional needs: dry ewes and weaned lambs. Dry ewes need only maintenance levels of nutrition; growing lambs need high levels of protein and energy. We can choose to manage these groups as two separate units or as a single mob. If we don't wean, then we are really choosing to manage them as a single mob.
Keeping them together means that we will often underfeed and overfeed at the same time. As pastures mature, we will underfeed the lambs, who need more energy and protein for growth, but we will still allow too much feed for the ewes, who will simply gain weight.
A mob of dry ewes, however, gives us all sorts of good options:
The second item hits the checkbook even more directly. How much does it cost to worm a flock? What if we can save over 50% of that cost without compromising the health of the lambs?
As every shepherd knows, sheep on green pasture usually become infested with intestinal parasites (primarily roundworms, also called "nematodes"). Adult ewes generally resist the effects of these worms because they have developed some immunity, but lambs can be devastated - they don't develop immunity until they are older. Periodic doses of deworming medicine reduce that worm load. Veterinarians in most areas of the country currently recommend treating every three weeks (which is the length of the life cycle of some of the major nematode species), particularly in early season when the lambs are younger and the fresh pasture growth is ripe for worm larvae.
A basic principle of parasite control is to dose all the animals at the same time; we can't just treat the "wormy-looking" ones. This means that we must worm the lambs and the ewes in an unweaned flock. Otherwise, the ewes would just continue to release millions of viable worm eggs back onto the pasture.
And here's the rub: worming medicine is given by weight. Heavier animals receive larger doses than lighter animals. Worm medicine is not free. Ewes cost more to dose than lambs.
For example, let's say that we are pasturing 100 ewes with their 150 unweaned lambs (= 150% lamb crop before dogs). The ewes weigh 160 pounds and the lambs average 50 pounds. Our flock, therefore, consists of 16,000 pound of ewes (= 100 x 160) and 7,500 pounds of lambs (= 150 x 50), giving a total flock weight of 23,500 pounds - 68% ewe weight and 32% lamb weight. In an unweaned flock, therefore, 68% of our worm medicine goes to the ewes, which is an overhead expense.
Let's speak in dollars: I recently purchased a 960 ml bottle of Ivomec® (Ivermectin) for $55.00, which means that 1 ml of Ivomec® costs $0.057 (5.7¢). The label instructions are explicit: orally drench 3.0 ml of Ivermectin for each 26 pounds of sheep (= 0.115 ml of wormer per pound). Therefore, the dose for a 160-pound ewe would be 19 ml, costing $1.05 (= 160 x 0.115 x $0.057). This adds up to $105.00 for all our ewes. In contrast, a 50-pound lamb would receive 6 ml, costing $0.33 (= 50 x 0.115 x $0.057), which adds up to $49.50 for 150 lambs. Each worming of this unweaned flock costs us a total of $154.50 for drugs, which includes over $100 just for overhead.
But dry ewes really don't need worming medicine until late autumn or winter (local veterinarians can help with the details). In general, dry ewes won't pick up many parasites if they are grazed on parking lots or other poor-quality pastures. For our sample flock, we can save $100 direct costs at worming by simply moving the ewes away from the lambs - i.e. weaning.
And these calculations don't include any time savings due to having fewer animals for handling and drenching.
Good businesses try to find ways to cut overhead without hurting their products. Early weaning can be a business strategy for reducing that overhead.
Woody Lane is a nutritionist in Roseburg, Oregon. He teaches Nutrition, Sheep, and Forage courses at Umpqua Community College, and operates an independent consulting business "Lane Livestock Services." His email address is email@example.com