THE performance of ruminants suffer when digestible energy becomes a limiting factor.
Fortunately, pellets containing essential proteins, carbohydrates, and fats provide a ready solution for cattle and sheep producers.
Carbohydrates are the main source of energy in diets. They are either non-structural (readily digested by all livestock) or structural (some are digested through fermentation that occurs in the rumen).
Ruminant animals have the unique ability to digest some structural carbohydrates in plant cell walls as a source of energy through microbial activity in the rumen.
Structural carbohydrates include cellulose, hemicelluloses, and lignin. Cattle can digest cellulose and hemicelluloses through rumen microbial action but cannot digest lignin.
As plants mature, cell walls become more lignified and less digestible. Forage digestibility declines tremendously when forages become over mature before cutting or grazing.
High ambient temperatures tend to increase plant lignification (production of the indigestible compound lignin), thus lowering digestibility in forages.
It is important to provide livestock with adequate amounts of digestible energy for optimal animal performance. Highly lignified forages are slower to digest than less lignified forages and feeds.
Increasing lignin levels in forages livestock consume increases time the forage spends in the rumen, decreases dry matter intake, and reduces animal performance.
Signs of energy deficiency include lowered appetite, weight loss, poor growth, depressed reproductive performance, and reduced milk production.
The most energy dense carbohydrate is found in cereal grains with corn, wheat, barley and sorghum the most readily available carbohydrate source.
The diets of cattle in Queensland are primarily forage based. Many factors affect digestible energy levels in forage, including forage maturity and species.
Cool-season grasses, such as fescues and annual ryegrass, are generally more digestible than warm season grasses, such as buffel grass and kikuyu.
Legumes like clovers and alfalfa generally are higher in digestibility than grasses. Energy is more likely than protein to be deficient in forage-based beef cattle diets.
Consider the nutrient demands of a typical 600kg beef cow. Assuming peak milk production of 10 litres/day, this average cow should consume just under 12kg of dry matter each day (DMI = dry matter intake = 12) in the first two months after calving. The animal's nutrient requirements will be about 10MJ DE and 11 per cent crude protein on a dry matter (DM) basis.
Five months after calving, this cow will need 9MJ DE and 8.5pc crude protein on a DM basis to support lactation. In many other production scenarios, energy content of forages will need supplementation to meet animal nutrient requirements.
Monitoring and providing acceptable energy in the entire diet is critical for good cattle performance.
The same cow will have much lower nutrient requirements once her calf is weaned. A dry (non-lactating) beef cow seven months after calving will need to consume just over 9kg of daily DM (DMI = 9) with about 8MJ DE and 6.5pc crude protein on a DM basis.
Energy supplements are available in many forms. High quality forages, commodity by-product feedstuffs, such as whole cotton seed and dried distillers grain, and molasses are some examples. The short falls with these supplements is they can price well on energy cost alone but often have low or imbalanced mineral content.
High producing and growing cattle need magnesium for calving, calcium and sodium for lactation and trace minerals such as zinc, selenium, copper and manganese for semen quality and cycling and conception.
Consider using high-quality suppliers of manufactured pellets to supplement energy in beef cattle diets when possible.
If the operation has facilities to store and handle bulk feed ingredients, pellets usually will be the best value for supplementing forage-based diets for calves and lactating cows.
The reason for this is the ability for the manufacturer to add minerals, vitamins, feed additives and buffers to the pellet to provide a balanced supplement that is safe to feed and can target different stages of production when mineral requirements change from pre-calving to lactating to dry cow requirements.
Manufactured pellets can have a range of rolled or hammered grains to provide the benefits of several cereal grain sources and protein meals.
Custom and personalised formulations can be made by feedsafe accredited mills to ensure confidence with consistency from load to load.
Progressive producers are now moving away from least cost formulations to more expensive pellets that are designed to reduce the cost of gain rather than targeting the cheapest price per tonne.
Advanced formulations will contain higher quality chelated trace minerals that have improved bioavailability and can be included for macro and micro minerals.
The use of feed additives in pellets is becoming more important and producers understand the benefits of feed technologies such as slow release nitrogen and live yeasts to improve energy yield and rumen fermentation.
Also becoming more popular is the use of pathogen binders to combat scouring and e-coli as well as mycotoxin binders for binding moulds found on pastures to target changing seasons and production goals.
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