“Seasons”, by definition, has various meanings. The concept of supplementing ruminants on natural grazing links back to seasons. This does not solely refer to climatic seasons but also the various production “seasons” of ruminant animals. The aim of supplementation has two broad objectives; the first is to correct the dietary deficiencies ruminant animals may be experiencing on grazing and the second is to stimulate intake. In addition, it is should be noted that incorrect supplementation (feeding unbalanced licks) practices could lead to nutrient imbalances, which may ultimately eliminate the potential advantages originally intended through supplementation.
Natural grazing varies in quality, due to species composition which will be influenced by (and is not limited to) the specific area and grazing practices employed. In addition, it also fluctuates with rainfall, which is not only linked to the seasonality thereof but also the frequency and intensity at which it occurs (for example droughts and floods). When considering the nutritional needs of sheep and cattle on natural grazing, levels of protein, energy, minerals and vitamins are adjusted in supplements to suit the production needs of the animal and to address the nutritional deficiencies of the grazing.
More noticeable during the drier months of the year, natural grazing limits the production of sheep and cattle, due to the nutrients it provides. For example; on sourveld, the quality of the veld (usually the low protein content) limits intake, whereas, on sweetveld, the reduced availability of veld usually limits animal production.
In response to the seasonal variation in forage quality and the nutritional requirements of ruminant animals in their various production “seasons”, farmers have opted to arrange breeding seasons on the farm so that calving and lambing seasons usually coincide with higher forage availability (during the wet season).
At the start of the dry season, grasses enter a dormant phase where nutrients are translocated to the plant’s roots. The limiting nutrient on dry grazing is nitrogen. Protein is a source of nitrogen and several forms are available, which all come at different costs. The first is urea (a non-protein nitrogen source) and the second, is natural protein sources such as oilcakes. The nitrogen is subsequently used by the microbes which reside within the rumen and in turn, they supply the ruminant with high-quality nutrients. Nitrogen is used by the ruminal microbes for the following;
- microbial growth,
- microbial multiplication and
- microbial protein (which is digested and absorbed in the small intestine) production.
By supporting the growth and multiplication of the microbes within the rumen, the intake of poor-quality roughage by sheep and cattle is stimulated. Through nitrogen (protein) supplementation, microbes can digest the poor-quality roughage to a greater extent, which results in elevated volatile fatty acid production, which serves as the main energy source for ruminants. Protein is required by cattle and sheep to prevent excessive weight loss (or a loss in body condition) and to reach optimal rates of reproduction. Protein supplements will be sufficient for those animals which are at maintenance or during their early stages of gestation.
As the dry season advances, the quality and availability of the natural grazing decline further; to the lowest degree, it will reach for the entire year. However, the majority of the calving or lambing seasons start just before the onset of the rainy season. Female animals during their last trimester of pregnancy and peak lactation have the highest nutritional requirements for the production year. This necessitates that production supplements be provided; which contain adequate levels of protein, energy and minerals.
When should one change between protein and production supplements on the farm?
When the intake of a protein supplement starts to increase, it demonstrates that the nutritional requirement of the sheep or cattle has changed and one needs to change over to a production supplement. Take care as to not change over too quickly from a production supplement to a wet-season supplement (those containing higher levels of minerals, such as phosphorus) as the quality of the grazing may be poorer than you think.
As the seasons change, so should the supplements we provide to the ruminants on the farm. This will be dictated by supplement intake and animal production stage, as well as veld quality and quantity.
