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- It is important that livestock producers plan thoroughly for periods when the waning quality of natural pastures can negatively impact animal production.
- Livestock can easily lose 10 to 15% of their summer weight.
- Bridging a nutrient reduction will differ from farm to farm, based on the availability of irrigation water and arable land.
- One must consider whether the pastures must be annual or perennial, legumes or grass, or a mixture of both.
- Be sure to ask for a lick supplement that is specifically balanced for the available pasture.
Seasonal differences in feed production are a given and it is therefore important that livestock producers plan thoroughly for periods when the waning quality of natural pastures can negatively impact animal production.
“While the nutrient content and quality of feed varies throughout the year, a decline is often more noticeable in the summer rainfall areas during autumn, winter, and spring,” says Gideon Jordaan, a grazing specialist from Cradock in the Eastern Cape. “When the nutritional value of grazing starts to decline during the latter part of the year, livestock can easily lose 10 to 15% of their summer weight. Unfortunately, there is no quick fix to bridge this nutritional low, which is why producers need to plan.”
Good management measures
The secret to bridging or partially eliminating these deficiencies lies in a combination of one or more of the following measures: Maintaining conservative long-term grazing capacity on the farm, optimal use of cultivated winter pastures, storage of high-quality summer crops, and putting out licks.
Bridging a nutrient reduction will differ from farm to farm, based on the availability of irrigation water and arable land. By shortening or eliminating these low-nutrient phases, one can even increase animal production and reproduction, which will have a positive effect on the overall enterprise. The purpose of cultivated pastures is to increase animal production through increased feed production and improved feed quality.
“Currently no single crop can meet animal requirements in all circumstances. Choosing the right grazing pasture to achieve the desired outcome depends on certain factors that include the climate in the area, the availability of irrigation, and the availability of suitable land for feed production.
“One must also consider whether the pastures must be annual or perennial, legumes or grass, or a mixture of both,” says Jordaan. “Legumes such as lucerne and clover can potentially create huge savings on nitrogen fertilisation. Also keep in mind that autumn, winter, and spring feed forms part of a well-planned animal health programme. While the number of internal parasites are usually lower during the colder months, it is worth keeping in mind that high livestock numbers on cultivated pastures may potentially create problems in growing young animals.”
The foundation of forage needs
Gisela Bisschoff, a ruminant nutritionist at ADM, says any supplementation given to animals must balance their needs as opposed to what they can obtain from grazing and water. Only the difference should be provided through correct supplementation. “Keep in mind the following simple equation when considering supplementation through various periods of production and grazing variation: Animal maintenance requirements plus production/reproduction requirements minus pasture supply minus water supply equals supplementation needs.
“This is why the market offers a wide range of supplementary feed and licks,” she says. “A supplement provided in the summer is different from one provided in winter. A lick provided in the Limpopo bushveld region will differ from a lick given on the mixed grassveld of the Free State. And different supplements are needed when animals graze cultivated, fertilised green grazing.”
The main components to be balanced on cultivated green pastures are protein, energy, minerals, and vitamins. Annual cultivated pastures are mostly high in moisture and protein, lower in metabolisable energy, and have a different mineral, trace element, and vitamin composition than perennial grasses. Physical aspects of the total daily ration intake affect how efficiently nutrients are digested and utilised by the animals.
Fibre considerations
Low-fibre components of cultivated pastures cause a shorter retention time in the rumen, and therefore a very quick passage rate, leaving little time for nutrients to digest in the rumen. Some minerals are only absorbed in the rumen and these elements must therefore be supplemented at higher rates compared to when animals graze normal perennial veld grass. Hence, it is crucial that an animal receives enough fibre throughout the day. This can be achieved by rotating grazing of cultivated pastures and natural veld.
“Roughage sources in the form of a hay bale can also be added, but always ask yourself: Will the animals really ingest any of the dry brown bale if they have palatable green pasture available?”
Building blocks of protein
All animals require amino acids (AAs), the building blocks of proteins required for maintenance, cell growth, and production. Bischoff explains how it works: “In ruminants, proteins and AAs are first subjected to microbial degradation in the rumen. The absorbed AAs come from microbial protein synthesis in the rumen and bypass dietary AAs that are undegraded in the rumen. The bacteria utilise the ammonia as a nitrogen (N) source, producing amino acids and peptides necessary for growth.
“Urea and ammonium chloride are non-protein nitrogen (NPN) feeds. Urea is quickly hydrolysed by ureolytic bacteria in the rumen. It is important to note that energy is needed for the breakdown of ammonia from NPN sources, as well as the rumen-degradable part of true protein to microbial protein. It is therefore very important that the total protein intake is balanced with the energy supply.”
All ruminal microbes contribute to protein breakdown to some extent. The final step in the breakdown of dietary proteins is the breakdown of AAs to ammonia. Ammonia nitrogen is the major source of N for protein synthesis. Ingested dietary proteins and endogenous proteins are digested in the small intestine. Several studies have shown that supplements from rumen fermentable energy sources increase the transfer of urea into the rumen and therefore the capture of dietary N. Energy sources may also improve utilisation of dietary and urea-N by less direct means such as energy-sparing effects within the cells of the gut tissue rather than alteration of rumen fermentation.
In a nutshell
“For optimal results, we can conclude that the main lick supplementation groups such as a winter, summer and production licks – typically formulated to supplement perennial veld grazing and containing NPN sources to assist with digestion and utilisation of the higher fibre containing veld grass – won’t be sufficient to balance out the need-supply effectively when animals are grazing cultivated green pastures.
“When planning to successfully grow out young animals on these pastures, be sure to ask for a lick supplement that is specifically balanced for the available pasture.” – Carin Venter, Plaas Media
For more information, contact Gideon Jordaan on 082 927 6779 or gideon.jordaan01@gmail.com, or Gisela Bisschoff on 066 485 6747 or gisela.bisschoff@adm.com.
