During the late fifties, an Australian livestock specialist summarized the results of a multi-year pasture study involving three cattle ranches. The weaning weight of the calves on one ranch consistently outweighed those from adjacent ranches by 70 to 100 pounds per head. The differences inweaning weights could not be explained by variability associated with breeds, dates of calving, soil types, forage species, etc. However, the reancher with the heavier calves practiced "topping" his pastures. This practice was the only variable identified that might explain the variation in weaning weights. Topping was explained as clipping the pasture with a rotary mower at early heading to prevent further flower stalk development. If flowering stems are not consumed prior to seed head emergence, they become woody and unpalatable. With timely clipping, while the grass is still palatable, livestock will readily consume the residues.
How does topping relate to the variation in weaning weight? Grass physiologists have shown that disruption of seed head development triggers production of new shoots (aftermath) from basal buds in crown tissue. Timely, topping of pastures results in earlier aftermath production. The lush aftermath provided a higher quality ration than was available on the adjacent ranches.
In summary, the nurse cow gained a two-fold benefit from the above practice; they consumed flowering stems that would otherwise been rejected, and they enjoyed a higher quality mid-summer ration comprised of lush aftermath shoots.