The rest period — the interval between two successive grazings on the same paddock — is the central variable in any rotational system. Setting it correctly determines whether plants have time to replenish root carbohydrate reserves, rebuild leaf area, and maintain competitive advantage over weeds. Set it too short, and stands weaken over seasons. Set it too long on a small farm, and excess forage matures and loses quality before livestock return.
Plant Physiology and the Grazing Cycle
After defoliation, a grass plant draws on stored carbohydrates in the root and stem base to push new leaf growth. This initial growth phase is energy-intensive for the plant. If livestock return before sufficient leaf area has regrown to support active photosynthesis, the plant is forced to draw down reserves again. Repeated early defoliation progressively reduces root mass and stand density.
Most temperate grasses — including timothy, orchardgrass, tall fescue, and bromegrass common in Canadian pastures — reach an inflection point in their recovery curve at roughly the three-leaf stage. At this point, the plant has rebuilt enough leaf area to photosynthesize surplus energy and begin replenishing root reserves. Returning livestock before this stage means the plant is still running a deficit.
Legumes Behave Differently
Legumes such as alfalfa and red clover store carbohydrates primarily in the crown and upper root rather than in stem bases. Their recovery depends on new shoot development from crown buds, which requires a longer rest period than many grasses under identical conditions. Alfalfa in mixed stands typically benefits from rest periods of 35 to 45 days in active growing conditions, longer if the paddock is under drought stress.
Rest Period Lengths Across the Canadian Season
Rest period requirements are not fixed. They shorten during peak spring flush, when warm temperatures and moisture accelerate growth, and lengthen in midsummer heat stress and again in the slower days of August and September. A useful framework for temperate Canadian regions:
| Period | Approximate Rest (days) | Notes |
|---|---|---|
| Early spring flush | 20 – 30 | Fast growth; may need to skip paddocks to allow cutting for hay |
| Late spring / early summer | 30 – 40 | Steady growth; primary grazing season |
| Midsummer (heat stress) | 40 – 60 | Slow growth; avoid over-resting to prevent over-mature forage |
| Late summer / early autumn | 35 – 50 | Recovery improves with cooler nights; build plant reserves pre-dormancy |
These figures apply broadly to southern Ontario and comparable temperate zones. In the Prairie provinces, the active season is compressed, and rest periods during the short peak growth window may be kept at 25 to 35 days to cycle through paddocks before frost.
Monitoring Recovery — Practical Methods
Two widely used field methods for assessing paddock readiness are visual assessment of plant growth stage and measurement of forage mass with a rising plate meter or pasture stick.
Visual Growth Stage Assessment
For grass-dominant paddocks, readiness corresponds to the period just before or at the boot stage, before seed heads emerge. Leaf blades should be fully extended and plants showing active new growth at the base. For legume-grass mixes, watch for the alfalfa to show one-tenth bloom — the point where a small proportion of plants show the first open flower. At this stage, digestibility is still high and regrowth will be vigorous.
Target Entry and Residual Heights
Entry height targets give a quick field guide:
- Orchardgrass / timothy mix: enter at 20 to 30 cm, leave at 8 to 10 cm
- Tall fescue: enter at 25 to 35 cm, leave at 8 to 12 cm
- Alfalfa-grass mix: enter at 25 to 35 cm (or at one-tenth bloom), leave at 8 to 10 cm
- Native prairie grasses (Prairie provinces): enter at 15 to 25 cm, leave at 10 to 15 cm
Leaving an adequate residual is as important as the rest period itself. Residual leaf area drives the speed of initial regrowth after each grazing event.
Impact of Rest Period Length on Sheep vs. Cattle
Sheep graze more selectively than cattle and can reduce sward height more uniformly. This selectivity means a sheep paddock that has been grazed to target residual has typically had more leaf area removed than a cattle paddock at equivalent residual height. As a result, rest periods following sheep grazing may need to be slightly longer, by five to ten days, to account for the more thorough defoliation of preferred plant species within the paddock.
Cattle, grazing less selectively, leave a patchier sward. Some areas within the paddock may be under-grazed, allowing those plants to mature faster and reduce overall sward quality at the next entry point. Occasional clipping of rank patches and strategic repositioning of water or mineral feeders can improve grazing distribution.
End-of-Season Rest Period Management
Plants entering winter dormancy need adequate root carbohydrate reserves to survive and produce strong spring growth. Grazing too aggressively in September and October, without allowing at least one full rest cycle before hard frost, can reduce stand persistence through winter. A common approach for small Canadian farms is to take the last rotation of the season at reduced stocking density, accepting slightly less-than-optimal forage utilization in exchange for better stand condition the following spring.
References
- OMAFRA. Pasture Management Guide for Ontario. ontario.ca
- Saskatchewan Ministry of Agriculture. Pasture Management. saskatchewan.ca
- National Research Council. Nutrient Requirements of Beef Cattle. National Academies Press (public reference).