Most farmers experience difficulties in determining the number of sheep per acre in rotational grazing. Rotational grazing is a system whereby more than one pasture area is used for grazing land and the sheep are moved to different pasture areas during the grazing season. Pastures would then be left to rest and recover from grazing. This practise allows the forage to regrow while sheep are grazing in another pasture land. The results are increased forage yields and controlled weeds. Since forages make up about 75% of the total sheep diet, they should be efficiently allocated to allow for the optimum and efficient usage of these grazing lands. Effective utilisation of this technique requires efficient planning on the pasture yield. Note that placing an increased number of sheep per acre in rotational grazing diminishes the quality of the forage. As such, farmers are advised to acquire the relevant knowledge on stocking densities to achieve successful management of the pasture land.
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Stocking Density Based on Available Resources
Stocking density generally refers to the number of animals that are kept on a given unit of area. The upside of this grazing technique is that it can allow an increased number of sheep per acre, depending on the type of rotational grazing in practise. The number of sheep per acre in rotational grazing is largely determined by the available resources. Although rotational razing is known for its superior forage quality, this often differs according to the type of grass. Hence, there is need for farmers to be aware of the nutritional value provided by the available pasture lands. This allows them to effectively meet animal dietary requirements which directly translate to increased productivity and profitability.
By knowing the percentage of grasses and legumes in the pasture, the maturity of the pasture, and its approximate nutrient composition, estimates of the number of sheep per acre in rotational grazing can be made. Sheep get a large portion of their nutrients from pasture than most of the other farm animals but forage must at times be supplemented with grains to boost their diet. The pasture lands chosen should therefore accommodate these needs. Poor quality pastures can accommodate 4 ewes and 8 lambs per acre so that sheep can acquire their required nutrients from the pasture lands. High quality pastures are required to have a carrying capacity of 10 ewes and 15 lambs per acre. Rotational grazing in these lands also allows the sheep to be interchangeable rotated between the high quality and poor quality pasture so that as one paddock is being grazed on, the other is given the opportunity and time to grow.
Stocking Density Based on the Rule of Thumb
The rule of thumb is basically a broad accurate guide or principle based on practical knowledge. The upside of using this technique in determining the number of sheep per acre in rotational grazing is that it is fairly easy. Unlike most methods, it uses minimal mathematical calculations. The rule of thumb is based on practical experiences which have proven to be effective hence its preference in the agricultural community. The rule of thumb states that 10 ewes and 15 lambs can be placed in an acre of land. Note that this technique assumes that the system of rotational grazing is well executed allowing sheep to graze, moving them in appropriate timeframes. Another point to note is that using the rule of thumb to determine the number of sheep per acre in rotational grazing is sometimes unreliable. The rule of thumb uses generalised algorithms that do not take into account the quality of available resources versus nutritional requirement and production stage.
Stocking Density Based on Nutritional Requirements
The number of sheep per acre in rotational grazing is also determined by the nutritional requirements of livestock. The dry sheep equivalents (DSE) is a standard unit that is use to compare the feed requirements of the sheep or the carrying capacity of the pasture lands in relation to determining the stocking density of the pasture lands. It works by ignoring the variations between the class of the animals which generally means that same units are calculated for lactating ewes, lambs, non- pregnant ewes and rams. The DSE represents the amount of feed needed for sheep to maintain their weight. The stocking density based on the DSE is therefore calculated as the total DSE divided by the total amount of the rotational grazing land available. In summary, the equation is as follows:
Stocking rate per acre = Total DSE’s / Total grazing hectares
The DSE after computation is the used to find the carrying capacity of the land to ensure the right amounts of feed is reached for the sheep growth rate. The carrying capacity of the pasture lands, the climate conditions of the grazing area, body weight of the sheep and the growth stage of the sheep are also used to determine the number of sheep per acre in rotational grazing. The upside of using this technique to determine the number of sheep per acre is that it is accurate therefore guarantees increased productivity as animal nutritional requirement are met.
Stocking Density Based on the Production Stage
The total number of sheep per acre in rotational grazing can be affected by the production stage of livestock (lactation or maintenance). Lambs and lactating sheep are usually given more grazing area. Early lambing sheep should be allowed to graze in the high quality pastures at the beginning of the grazing seasons to improve their growth rate and lactating rates. It is recommended to have 5 early lambing ewes on fairly good pastures and to increase this number as the grazing period proceeds. Overstocking the ewes at the beginning of the season will cause the farmer to run out of good pastures, therefore defeating the whole purpose of rotational grazing.
Pregnant sheep, especially twin bearing sheep, lactating ewes and lambs as well asill health sheep should be allocated good quality pastures. Pregnant sheep’s feed requirements change overtime as the period for giving birth nears. Therefore, they should be given fair amount of rations while in the 8 weeks of pregnancy and then after weaning the diet can be readjusted to normal. Under good pasture conditions, this class ofsheep per acre in rotational grazing is stocked at a ratio of 10 sheep to 1 acre and rotating them as the grazing season is progressing. Lactating sheep with lambs are given the better pastures to promote milk production and lamb growth. Non-lactating sheep and males are then given the lesser quality forages.This keeps a balance for forage utilisation and at the same time improves sheep growth and production. Non-pregnant sheep, mature lambs, sheep bred for meat and wool as well as rams do not require much pasture as the early lambing and the pregnant sheep. They therefore can be heavily stocked. However, an important aspect to note is that their daily nutritional requirements are met.