This is a summery of a presentation given by Janet McNally at the 2014 Grassfed Exchange..
Unfortunately the pictures did not copy over, so if you would like to see the accompanying pictures, let me know and I can forward you a complete pdf.
Unfortunately the pictures did not copy over, so if you would like to see the accompanying pictures, let me know and I can forward you a complete pdf.
How dealing with wolves led to more grass and fewer parasites.
I am about to explain how measures aimed to stopping depredation from a large wolf pack, led me to management changes that resulted in more grass, more drought resistant pastures, and improved carbon sequestration (building more organic matter in soils) and fewer parasites. But first, a little back ground is due. In 1991 I commenced lambing on pasture in a type of drift lambing system that changed little for a whole decade. Modeled after drift lambing in the deserts in the Western US, the idea was to move the pregnant ewes forward to the next paddock every morning, while leaving behind the ewes that had lambed in the past 24 hours. Those ewes that were left behind would stay in that paddock for the next 30 to 50 days. Doing so enhanced ewe and lamb bonds and minimized mis mothering and optimized lamb growth. At the end of the set stock period, paddocks full of ewes and lambs would be joined together to form one big mob, and rotational grazing began. Ewes and lambs would move once a week to a new pasture, and paddocks were given approximately 28 to 32 days to recover. My goal was to keep the pasture in a vegetative state for optimum nutrition.
In this system, a parasite load was to be expected and was dealt with by drenching the flock every three or four weeks through out the summer season. Coyotes were the primary predator, but also at that time, hunting coyotes with hounds was common, and a handful of LGDs scattered around the paddocks, one dog per paddock, was sufficient to keep predation under control. In the west, coyotes were dealt with through livestock associations that hired trappers ahead of lambing time to reduce the population. Meanwhile the wolf had gained protection in the early 70s and by the 90s had expanded to our area.
This all worked rather well up until 1999, at which time we were to experience a devastating encounter with wolves during lambing. Unknown to me, a pack of 23 wolves had moved into the area just prior to lambing. In one paddock alone, I lost 40 out of 80 lambs in just ten days time. In the other four paddocks I lost another 35 lambs, and nine ewes.
Shepherds have successfully used livestock guarding dogs for 6000 years, so just what was I doing wrong? Some investigation revealed that European shepherds often used 8 to a dozen dogs, and kept the whole flock together as a mob. It was the shepherd’s job to keep the flock tight together so the dogs could defend it. So I combined all of the sheep into one mob, fenced them in with portable electrified netting into a small one acre paddock, and put all four livestock guard dogs in with the group together. The ewes were still lambing and I was expecting a lot of mis mothering due to the crowded conditions, but the depredation stopped over night. I was also pleased to see that the new mothers coped with the crowded conditions, and mis mothering was insignificant.
Now that the sheep were combined into one mob, it was necessary to start rotational grazing right away. I could not afford to expose the flock to further depredation by spreading them out and set stocking. Hence began a system I refer to as ‘lambing on the fly’ where by the pregnant ewes move every day into a fresh paddock, leaving behind the ewes that have just lambed, and behind them in a third paddock, are the ewes that have lambed 3 or more days ago. Each day the older lambs are combined with the day old lambs, and the now empty fence leap frogs ahead to make a fresh paddock for the pregnant ewes. All three paddocks remain contiguous, so that all of the dogs can protect all three paddocks. When lambing is done, the three groups merge into one mob and continue rotationally grazing. What is remarkably different about this strategy, is that the ewes that have just lambed keep on moving right behind the pregnant group, and the paddock sizes are small, with the stocking density high (but not uber high, I will keep approx 150 ewes in a paddock that is 164 feet by 328 feet). This strategy is no doubt, challenging to new mothers, and I suspect that it might be a bit overwhelming to sheep or shepherds who are experiencing their first lambing season on pasture. But as my flock had been pasture lambing for a decade, I had already been selecting for ewes that were well adapted. Initially one or two ewes dropped out of the system each year, but by and large the flock was ready for the change.
The unintended outcome of mob stocking with higher stocking densities, and moving daily, when the lambs are so young, is that during the spring flush, it took quite a while before the sheep would munch their way back to the starting point. Thus the forage had six or eight weeks of rest before I would be back to grazing it again. This meant the forage was very tall and mature. Under my previous management of set stocking, I tried to maintain a forage height of 2 to 4 inches for optimum nutrition. Now forage was anywhere from one foot, to six feet tall when the sheep returned!
About the same time that wolves became a significant issue, another problem was growing, which is the development of parasite resistance to anthelmentics (sheep wormers). While participating in a study, I found out that valbazen for instance, was only removing 65% of the Haemonchus Contortus in my sheep. Haemonchus Contortus (barber pole worm) is one of the most economically significant parasites of sheep that can result in anemia, lost production, and death. The result was that deworming was less and less effective, and had to be done more frequently. A few short years later, my flock began to experience symptoms of resistance to Ivermectin as well. Parasite resistance can develop very rapidly, leaving no viable options for treating parasites. The writing was clearly on the wall that reliance on drenching with chemical dewormers was no longer a viable way to address parasitism in sheep. Meanwhile, I began to notice that the sheep that were managed in the mob stock fashion, moving every day, and by default, grazing taller grass, showed relatively few symptoms of parasitism. I also kept a smaller flock close to home, and set stock grazed that flock after lambing, then rotationally grazed with a more traditional four week rest period between grazings. This group continued to experience significant parasitism. In one particularly bad year I lost 1/3 of the lambs in the group that was in the four week rotation. This flock served as my ‘control’ demonstrating that the difference in grazing management was probably key.
The striking difference in parasite loads between management styles was not all too surprising. We know that parasite larvae tend to migrate up and down grass with the dew, migrating primarily in the first two inches. With the now taller grass, the sheep were eating above the zone where the parasite larvae habitate, where as in the previous management, the grass was kept 2 to 4 inches so that it would be vegetative. This meant in a more rapid rotation, grazing took place in the zone where the larvae hung out. But there could be another reason why the sheep managed as a mob were less bothered by parasites, and that is the longer rest periods. In favorable weather (hot and humid) HC larvae hatch 5 to 10 days after the egg hits the ground, with the peak hatch occurring about 21 days after the sheep entered the paddock. Under my previous rotational grazing management, sheep stayed in the paddock long enough to eat some of the first larvae that hatched, and returned to the paddock just in time to consume the peak larvae hatch. With the adult female Haemonchus Contortus producing 10,000 eggs per day in the sheep, the worm load in the sheep and the paddock would compound exponentially each time the sheep returned to the paddock. HC larvae live for two or three weeks, then if not consumed, begin to die off. About six weeks after eggs hit the ground, the die off is significant enough to render the paddock relatively safe. Eight weeks is even safer. What the mob stocking did, was force the ewes to move more frequently, such that they left the paddock before the first eggs hatched, and by using the small paddocks and high stocking densities, it took longer to return to the original paddock, thus giving the larvae time to hatch, and then die off before the sheep returned. Knowing this, I then began making a minimum six week rest between grazings my goal. This benefit is really not too surprising. Historically sheep and shepherds are migratory moving daily to fresh grass, and not returning to the contaminated ground for months, if not a whole year and thus naturally avoided ground that was heavily contaminated with parasites. In essence what I have created was a mini migration within my farm, using fence instead of shepherds to keep the sheep tight together, and to prevent them from returning to contaminated ground.
I had followed this mob stocking plus six week rest model for several years, with great success in preventing depredation from wolves, including a pack of 8 to 10, as well as eliminating the need to drench my flock all summer long. Instead I would drench ewes and lambs only after the first frost in the fall, primarily to remove liver flukes which are spread by white tailed deer in this area. In 2006 we encountered a drought that was said to be a 100 year drought (occurred once in 100 years). The ditches on our farm dried up, stock ponds dried up for the first time in 50 years, and the forage turned brown by the end of June. I continued with my mob stocking and six week rest. What this means is that many paddocks were rested during that very sensitive stage where the grass is going dormant. I even resisted the urge to graze the shriveling grass because the rest time was not yet up, and instead fed hay for several weeks mid summer so as to stay off the paddocks until they were totally dormant. When the paddocks were finally dormant, I brought the sheep in and grazed them off. That September, we had a four inch rainfall event. Ten days later, the grass in the rested paddocks was ten inches tall! But what really struck me, was how the pasture across the fence, that was continuously grazed by cows throughout the drought, and never given a rest, was not even one inch tall. It turned green, but there was really nothing there. So here I had two pastures, basically sitting on the same geology, side by side. One continuously grazed, the other mob stocked and rested six weeks between grazings. Ten days after a four inch rain fall, the mob stock side had ten inches of forage, the continuously grazed side had scarcely one inch of forage. Wow, the difference was astounding. It was economically significant too. The neighbor with the set stocked cows began feeding hay in July, and had to feed straight through to the following spring. I fed hay for 3 weeks that summer, but then was able to defer grazing in enough pastures, to continue grazing until December 1. That is five months of hay feeding I did not need to do, because I rested my paddocks for six weeks between grazings.
This intrigued me and I became interested in learning more about what is going on beneath the soil surface. I already knew that the more plant growth above the soil surface, the more root mass below the surface. A rough idea is that pasture plants will tend to have as much below the ground, as they do above the ground. So it made sense maybe my paddocks had more root area ready to receive the rain. Rested plants also have a chance to store energy, where as continuously grazed plants are constantly using up their energy stores to regenerate. Logically then, the rested grass had more roots, more stored energy, and was able to reach the moisture once it rained, but there is more to the story than just root depth and stored energy.
A rain fall demonstration at the 2013 Grassfed Exchange Conference showed how rotationally grazed pastures had a more permeable soil structure which allowed greater water penetration, and less run off than continuously grazed pastures. I decided to dig up some soil samples of my own to look at what was going on below the ground. The area is a clay/sand mix with clay dominating. There is a hard pan about a foot down. Not surprisingly, the continuously grazed side (sample on far left below) lacking any root structure and showed a well defined hard pan which was saturated (this was a wet year). The rotationally grazed side (far right) had a more porous soil structure, deeper root penetration, and while the hard pan was visible, it was less well defined and not nearly as saturated. The real surprise was the middle sample, which was taken from an area where a bale of hay had sat during the winter (bale grazing is our winter feeding strategy) just 30 feet from the rotationally grazed sample (also managed as rotational grazing). There was 3 inches of organic matter above the area where the bale sat (note twine), and the soil below the bale was much darker, more porous, and the hard pan was not present. So the great response to the four inches of rain that I saw on my mob stocked pastures was probably more than just the benefit of deeper roots and stored energy. Most likely more rain percolated into the soil profile and less of it ran off or evaporated after the rain.
But the benefits of long rest periods do not end here. A study by Christine Jones in Australia compared a paddock that had been cropped and grazed in a manner to ‘enhance photosynthetic capacity’ where no super phosphate had been applied to a paddock that was continuously grazed with regular applications of super phosphate. The differences in root depth and soil structure were considerable, favoring the paddock managed for enhanced photosynthetic capacity. The implications for this go beyond soil productivity and plant vigor. Christine Jones goes on to measure soil carbon sequestration in each layer of soil, and what she has to say in her paper: Not just any carbon - and not just anywhere
“The surface increment, 0-10cm, generally contains the highest levels of labile carbon, indicative of rapid turnover. This ‘active’ carbon is important to landscape function and the health of the soil food-web. But the surface increment is not where one would be looking to safely ‘store’ atmospheric CO2. The deeper that carbon is sequestered, the better. The level of non-labile soil carbon (i.e. the humic fraction) in the LHS profile has doubled in the 10-20cm increment, tripled in the 20-30cm increment and quadrupled in the 30-40cm increment. Over time, it is anticipated that the most rapid sequestration of stable soil carbon will be in the 40-50cm increment, then later still, in the 50-60cm increment. That is, fertile, carbon-rich topsoil will continue to build downwards into the subsoil. Carbon sequestered below 30cm indicates good root penetration and high levels of
microbial activity. Deeply sequestered carbon alleviates subsoil constraints, enhances landscape hydrology and improves mineral density in plants, animals and people.
The Kyoto Protocol, which relates only to carbon sequestered in the 0-30cm increment, completely overlooks this ‘sequestration of significance’ in the 30-60cm portion of the soil profile. “ From: “Carbon that counts” Christine Jones PhD http://www.grassfednetwork.com/wp-content/uploads/2011/04/JONES-Carbon-that-counts-Jan2011.pdf
Whether one subscribes to global warming or not, laws are being made to reduce methane emissions of livestock based upon their potential warming effect upon the earth. In 2011 the IPCC commissioned a study by the Environmental Working group to look at the ‘cradle to grave’ carbon foot print of different protein sources in our diet. The report is titled “the 2011 Meat Eater’s Guide to Climate Change and Health” The report was very thorough counting every ounce of carbon emitted in the process of growing, transporting, slaughter, and cooking of every major protein source including grass fed lamb and beef, as well as chicken, pork, tofu, rice, beans, and a variety of other vegetable sources.
There are two major problems with the report. One is that they did not actually measure the carbon output of grass fed lambs. Instead, feedlot beef was the actual measured model, and the results for lamb was extrapolated from the beef model. But the other major issue with the report, can be found under the ‘methods and methodology’ section. From the EWG report: 8. Soil carbon sequestration is not accounted for in this model based on the IPPC guidance and generally accepted assumption used in LCA that all production systems under consideration have reached steadystates where the net carbon flux from the soil is zero on average (spatial/temporal average). it should be
pointed out that assumptions about steady state remain the subject of considerable scientific debate.
So, here we have a report that is being used as the world’s guide to the carbon footprint of our food supply, and they did not take into account the other half of the picture, which is the impact grazing animals have on carbon sequestration. As we saw above in the Christine Jones “Carbon That Counts” there can be large differences in how much carbon is sequestered depending upon how the land is managed, so to write off carbon sequestration as ‘in equilibrium’ is a gross assumption especially considering how carefully every ounce of carbon emitted was counted. That is kind of looking at the profit loss statement of a business, and counting every penny that was spent to run the business, but then blowing off deposits from income as irrelevant, and calling the business a loss. I don’t think the IRS would approve of that kind of accounting. It is this one sided accounting that is being used as the justification to tell the world it needs to eat less beef.
According to the USDA up to 4.8 metric tons of CO2/acre is sequestered each year on properly managed pasture, which equals 5 U.S. tons per year. Compare this to the EWG’s report that says 39.2 kg. of CO2 is produced per kilogram of lamb consumed. If we assume that 107.4 kg. lamb produced on one acre (see image) x 39.2 kg. CO2 produced per kilogram of lamb consumed = 4.209 kg. CO2 produced per acre, or 9,261 lbs., or nearly 5 tons/acre.
In other words, it’s a wash. The amount of carbon equivalent produced by the production and consumption of grass fed lamb, is negated by the carbon sequestered from the pasture itself on a well managed pasture. This moves grass fed lamb (and probably grass fed beef as well) to the bottom of the chart for carbon foot print (meaning the carbon foot print of grass fed lamb and beef is the lowest of all dietary sources of protein). We can all eat grass fed lamb knowing we are not contributing to global warming, and grass fed lamb and beef, may in-fact, provide a solution to reducing green house gasses.
So there we have it. A 6000 year old grazing management strategy aimed at keeping sheep safe from wolves and parasites, has the added benefits of improving pasture productivity, vigor and drought tolerance as well as sequestering more carbon deeper into the soil profile, where it is more effective at storing carbon.
It would be unjust to end here, and leave the impression that mob stocking and long rotations is easy. There is a down side. Waiting six to eight weeks to return to a paddock means that the forage is considerably more mature than it is with a 4 or 5 week rotation, so the level of nutrition goes down. When I looked at the western migratory flock model, the flock moved up in elevation to be continually chasing grasses that were still in a vegetative state. Moving up in elevation is not an option here. I’ve had to think on this long and hard looking for solutions. A trip to the Kansas City area to a dairy sheep producer Jacquelin Smith helped uncover the answer for flat landers. Plant diversity, especially some warm season grasses and legumes help keep the quality high through the summer. That, combined with leaving enough residual, so that we do not push animals to clean up lower quality leaves and stems.
Lactating ewes and growing lambs need to eat a diet that is 80% digestible dry matter in order to support milk and growth. As can be seen by chart (see chart)
only new green leaves have enough digestible dry matter (75%) to support lactation and lamb growth. To some extent sheep can meet their nutritional needs on pasture due to the rapid rate of passage through the GI tract; however, this can only go so far. As digestibility decreases, and lignin increases, the rate of passage slows down. As soon as sheep start biting the tips of stems, they are eating a diet that is only 50% digestible dry matter. Clearly part of my strategy had to be aimed at paying attention to what has been eaten, and what I left behind, as I did not want to force the sheep to eat stems and dead leaves as doing so would cause performance to suffer greatly, something I was already painfully aware of. So I began to pay more attention to what the sheep were eating, and making a point of moving them on before they started biting stems and old leaves. An important part of achieving this was to also pay attention to the animals themselves, noting how full their rumens appeared. If sheep were to develop that ‘hungry triangle’ (see photo below):
The hungry triangle is the area behind the last rib and before the hip. If this is hollow, animals are lacking a full rumen, or need water.
then I was past the optimum time to move. At a glance, the pasture might appear to have plenty of grass in it, but as closer inspection was to reveal, all the new leaves were gone, and the sheep had already bitten the tops of the green stems and old leaves. In other words, the remaining pasture mass was only 35 to 45% DDM.
Being the thrifty person that I am, I had a hard time leaving this much residue behind, until I learned that the plant residue was important to the soil by shading the soil and reducing soil temperatures so as to support a healthy population of soil fungi. Trampling some green into the ground feeds the soil and enhances the biological activity leading to better soil structure. Seeing the benefits of residue I became more comfortable with trampling the stems and old leaves, rather than being compelled to graze it all in the name of ‘cleaning up the plate’.
So one solution to the more mature state of pastures that have been rested longer, is to only graze the new leaves and then move on. This entails leaving (and trampling) considerable more material than I was accustomed to with more rapid rotations. Some estimates of intake and residual suggest that approximately 40% of the plant material should be consumed, and 60% should be trampled. At times the flock only grazed 30%. That is a lot of trampled material!
But another solution to the forage quality issue began to emerge. It so happens that the land I was grazing at one time supported a dairy herd, which once had been fed birdsfoot trefoil hay. The birdsfoot seed was scattered by the cows throughout the pasture in their manure 2 or 3 decades ago. As I opened up the canopy through grazing, the birdsfoot began to emerge, and expand through out the pasture. Among the unique qualities of Birdsfoot Trefoil, are that you can stock pile Birdsfoot Trefoil for a considerable length of time without loosing quality, or digestibility. Another redeeming feature of Birdsfoot Trefoil is that it contains tannins that are considered anti parasitic, so it can also reduce the worm load in sheep. Birdsfoot Trefoil needs six weeks of rest to set seed to perpetuate itself. These qualities make Birdsfoot Trefoil a perfect fit. So the birdsfoot provided a solution to my forage quality issue. Warm season grasses also began to show up, further improving forage quality during the ‘summer slump’ when the cool season grasses have gone dormant.
So the solutions to the forage quality issues that long rotations presented lay in leaving enough residual behind so that I do not force animals to eat lower quality plant parts, and in a species mix that includes Birdsfoot Trefoil and warm season grasses so that the mid summer pastures have some younger, more nutritious plants available. It seems species diversity increased rapidly in just a few years time of using long rotations, thus solving the problem naturally.
Wolves forced me into grazing as a mob which led to moving frequently and resting paddocks longer. Long rests meant the grass was taller when the sheep returned, and as a consequence, parasite burdens were reduced. Longer rests and taller forage meant less drenching, better root systems, more drought resilient pastures, and more grass. Better root systems means more carbon sequestration, especially deeper into the soil profile, perhaps enough to make lamb at worst carbon neutral, and quite possibly carbon negative. I have not even begun to mention the nutritional benefits of lamb produced this way. That is for another day.
Now my problems are not wolves or parasites, but too much grass.