Beef cows graze pasture for nutrients needed to maintain good body condition, nurse a hungry calf and get ready for the upcoming breeding season. The importance of meeting this higher plane of nutrition after calving cannot be understated, because its failure may lead to poor calf weaning weights and a poor future calving season. Therefore, it is vital that producers prepare for each pasture season by assuring all cows eat enough nutritious grass as well as be provided with dietary supplements for any lacking nutrients that do not grow out of the ground.
To initiate a good pasture foundation, first get a good idea as to the carrying capacity of all usable pastures; defined as the average number of cattle whose nutrient requirements can be taken from the fields without doing any serious damage. Most carrying capacities are based upon soil type and condition, annual rainfall, and plant species (both native and tamed pastures) within its fencelines. Ideally, the carrying capacity of most pasture can be determined by past experience of running specific cattle numbers or by estimating the forage yields for the season.
In the latter case, one practical method to measure forage production uses one-metre diameter hoop, clippers and collection bags. The hoop is thrown out into the field, and all the plants within its area are clipped, dried and weighed. The weights of these forage samples are then extrapolated onto a large field scale. From this estimated available forage yield, regrowth and cattle selection/wastage factors are implemented to determine the usable forage cattle may actually consume.
Getting a good idea of the carrying capacity and amount of usable forage of all pastures is a good start in the preparation of meeting the nutrient expectations of a cow herd. Next it is also important to know, differentiate and encompass the concepts of stocking rate and stocking density into a grazing plan. Although used interchangeably, stocking rate and stocking density are not necessarily the same thing, but should be used side-by-side in pasturing cattle.
Stocking rate & density
The stocking rate is the number of cattle on the entire grazing unit for the entire grazing season. For example, 100 beef cows and 100 acres = a stocking rate of one cow per acre. If we divide the 100 acres into 10 x 10-acre paddocks and place all the cows in one paddock for 10 per cent of the time, before moving them onto another paddock, then our stocking rate does not change, but stocking density is increased by 10 times.
Given the estimated carrying capacity of the pasture and number and type of cows, most beef producers should be able to calculate with reasonable accuracy, the number of cattle that can be stocked on any grazed field, given present pasture conditions.
Case in point: A beef cow after calving will largely meet the nutrient demands of maintaining a desirable body condition score (BCS), milk reasonably well, return to estrus cycling and get in-calf during the breeding season, if she gets about 12 kg of moderately nutritious forage (DMI, basis) daily. If a pasture yields 100 tonnes of estimated usable forage in a four-month growing season, it should support about 70 cows. A final stocking rate (and density) of the cows can be determined by dividing the actual number of cows by the number of available pasture acres.
Often conditions change as the grazing season progresses. Prepared ranchers should be able to effectively alter the calculated stocking rate/density because of changing growing conditions. If it rains the pasture may support more cattle, and if it is dry, then fewer cattle.
Regardless of pasture quality, there are a few “housekeeping” exercises that beef producers should consider:
- Provide an adequate and good water source — most beef cows drink between 40-50 litres of water per day.
- Provide commercial cattle mineral — Pasture grass is notoriously deficient in essential minerals such as phosphorus, copper, zinc, manganese and selenium. These elements are required by all beef cows and necessary for strong heat cycles and successful conception during the breeding season. Most of the time producers provide 50-70 grams per head per day of loose cattle mineral and salt blocks, near the water source.
- Use cattle lick blocks as a pasture tool — These blocks are either corn distillers or molasses-based products. They can be a good source of good nutrition, but they can also be placed in areas of pasture that cattle normally do not travel in order to increase pasture utilization. One block (90-114 kg) should be rolled out to 25-30 grazing animals. †