Sheep may safely graze

When the price of lamb dropped in the 1990s, Janet McNally had to make changes in the way she raised sheep.

McNally spoke recently at the Pennsylvania Forage Conference in Lancaster, PA. She decided to focus on grazing when she found her income was less than desirable after deducting feed, vet supplies and other expenses. Although she raises sheep on her Minnesota farm Tamarack Lamb & Wool, her challenges and results translate to Northeast sheep operations.

“In the 1990s, I used a drift lambing system,” said McNally – New Zealand and UK models claimed the system optimized bonding and lamb survival. “Lambs are born in a paddock, and every day the remaining pregnant ewes are moved out of that paddock. Ewes that lambed are left behind and stay the paddock for 30 to 50 days to mother up and raise their lambs.”

The system worked – sort of.

“We were running into a problem,” she said. “We had tremendous parasite issues and were starting to see losses. At the same time, I learned that South Africa lost one-third of their sheep population due to drench resistance.”

Barber pole worm (Haemonchus contortus) is a major economic problem in sheep, and it’s the parasite McNally was dealing with. This worm’s reproductive cycle, combined with three- to four-week paddock rotations, optimized H. contortus infection, and losses were due to that rotation.

One option was to switch to mob stock grazing – the practice of short-duration grazing on tall grass at high animal density with long intervals between paddock use.

“We had been putting sheep back into a paddock at peak larval hatch,” said McNally, “but I was resistant to mob stock grazing because of the tall grasses.”

In 1991, the wolves arrived. Their presence created a challenge that would further change the farm’s management model. McNally saw sporadic lamb losses at first, but in 1999 a pack of 23 wolves moved to the area.

McNally had been expecting 300 lambs when the wolves attacked her flock. The devasting encounter and subsequent loss of 75 lambs in 10 days was a big hit that took several years to recover from.

At a meeting where a wolf biologist was present, McNally told him what had happened. “His words were ‘We were expecting that,’” she said. “He already knew about the pack in our back yard.”

McNally’s livestock guardian dogs were doing their best. “The four dogs were spread on four properties, which worked fine with coyotes,” she said. “Now dogs were leaving their sheep to join another dog with sheep. They needed reinforcements so they could work together against wolves.”

Throughout Europe and Asia, sheep were commonly raised in herded flocks: shepherds take flocks to the mountains and travel with them. She also learned from a Colorado shepherd that he moved sheep every three days, at least three miles, to a new grazing area.

“If the move is less than three miles, the sheep might go back to the bedding grounds they used the night before,” said McNally. “Three miles is far enough away that the sheep bedded down in a new place. I learned that the shepherd’s job is to keep the sheep together in a tight mob so predators don’t pick them off on the peripheral of the grazing area. They’re moving every few days and they don’t come back to where they were for the whole season.”

McNally realized that wolves were leaping over the top of the hot wire fence and not getting shocked. Although she had previously used electric netting, McNally had given up on it due to issues such as lambs becoming entangled in it. Now her only option was to use netting again – this time for mob stock grazing.

The new fencing system for McNally’s 180 ewes involved two rolls of electric netting, which created a paddock measuring 164 square feet. The ewes and lambs were packed together but moved, on average, daily.

“This happened during lambing,” said McNally. “Instead of having them on 20 acres, they now had only half an acre. Sometimes I had to move them multiple times throughout the day to keep them fed. My initial decision was that if we were losing lambs to wolves daily, I would take my chances with mismothering due to them being in a congested area.”

Once the lambs learned that they moved daily, it wasn’t difficult to move them.

McNally also had to modify her lambing system. Leaving lambs and ewes behind in the drift lambing system for 40 to 50 days made them vulnerable to predators. She divided sheep into new groups and back-fenced the area with each move.

One outcome with mob stock grazing is taller grass. McNally dreaded having to deal with out-of-control growth but noticed that sheep’s rear ends were clean despite grazing on turnips and not having been dewormed all summer.

“Parasite larvae crawl up and down the grass about four inches,” said McNally. “Before, sheep were grazing below four inches, and now we’re grazing at a foot or two high – taller than the larvae crawl.”

Parasite egg levels peak about three weeks after sheep are in a paddock. When sheep stay in a particular paddock, they are consuming larvae at the most infective stage.

“Is better parasite control due to grazing higher or is it due to resting the paddocks longer?” said McNally. “I say it’s both. We aren’t grazing down so low, and we’re allowing parasite larvae to die off before sheep come back to it.”

McNally no longer had to drench her sheep in summer – a long-time goal that was achieved accidentally when she was trying to keep the flock safe from wolves.

“Wolves forced me, kicking and screaming, into mob stock grazing,” McNally admitted. “I didn’t think this was a good way to take care of my sheep, but it stopped depredation problems and eliminated having to drench for parasites in summer.”

by Sally Colby