Feed consumption and liveweight gain
The key variables affecting the profitability of feedlots are: store cattle purchase price; finished cattle sale price; cost of feed consumed; and liveweight gain. This fact sheet deals with feed consumption and liveweight gain.
Commodities used in feedlot rations vary considerably in dry matter content (DM). Hay and grain are approximately 90% DM, molasses 75% DM and silage 40% DM. A basic guide for estimating dry matter consumption of feedlot animals is to calculate 2.7% to 3.0% of their liveweight (in kilograms). Therefore, an animal consuming a grain based diet of 90% DM, would have an estimated intake of fresh feed between 3.0% (2.7% x100/90) and 3.33% (3.0% x100/90) of their liveweight.
For instance, heavy steers destined for the Japanese short fed market have an entry weight of approximately 450 kg and a finished weight of 600 kg, giving an average weight of 525 kg.
Estimated daily fresh feed consumption (if consuming 3.0% of liveweight):
= (450 + 600)/2 x (3.0/100) = 15.8 kg
Total fresh feed consumption for 100 days:
= 15.8 x 100 = 1580 kg
The dry matter content of a ration refers to the amount of dry material available in a given ration. A number of factors influence the average daily dry matter consumption of lot-fed cattle. These include, liveweight (their required maintenance energy requirements), body condition, energy concentration of the ration, health status, and ration palatability.
Young animals and animals of lighter body condition may eat greater than 3% of their body weight on a dry matter basis as they have a higher maintenance energy requirement, while older animals and animals in better body condition have a lower dry matter intake approximating 2.7%.
The energy of a ration is measured in megajoules (MJ) of metabolisable energy (ME) per kilogram of feed on a dry matter basis. Metabolisable energy content of a ration can also effect consumption, with extremes in ME content reducing consumption relative to the optimum ME content of the ration. Palatability of the ration also effects consumption. Very low DM content diets (less than 40%) can result in reduced dry matter consumption.
Feedlot managers usually find that cattle in backward store condition (drought affected) need to be held in the feedlot for extended periods to meet market requirements. However, these cattle often consume well over 3% of their liveweight on a fresh feed basis and have exceptional liveweight gain. These fast gainers invariably have high feed conversion efficiency (liveweight gain: feed intake).
Variation in gut fill can have a large effect on liveweight gain and therefore must be minimised. The normal procedure with lot-fed cattle, if measuring for liveweight gain, is to weigh before the morning feed. This gives a benchmark time to work from, as initial induction weights are taken with little or no gut fill. Standard weighing procedures need to be adopted when determining liveweight gain.
In addition to gut fill, many other factors can effect liveweight gain. The most important of these include age, sex, genetic merit, breed, body condition, health status, diet composition, diet nutrient content, diet intake, growth promotant and previous nutritional history.
Noticeable variation occurs between animals in relation to an optimum finish point. Older animals will achieve optimum finish faster than younger animals, as these animals are nearing the end of their growth period and will partition most of their nutrient intake into finishing. Younger animals will partition a proportion of their intake towards skeletal and muscle development. Because heifers mature earlier than steers, they will normally finish sooner and may require closer supervision to avoid excess fat.
As a rule, European breeds grow faster than British or Zebu breeds and tend to be leaner, but there can be as much variation within a breed as between breeds. There is a wide genetic variation in the ability of animals to put on liveweight. As cattle finish, their rate of liveweight gain diminishes slightly. Health problems, whether it be acidosis, respiratory disease or from other causes, can be reflected in poor liveweight gain of individual animals. Nutrient deficiency (energy, protein, minerals and vitamins) can also cause a reduction in liveweight gain.
Growth promotants and rumen modifiers have proven to enhance liveweight gain. Any restriction in feed or water intake, causes a reduction in liveweight gain.
The following table is a guide to likely daily liveweight gains for a number of lot-feeding systems.
|Market specification *||Average gain
|Domestic trade – steers||1.4||1.1 to 1.7|
|Domestic trade – heifers||1.3||1.0 to 1.6|
|Korea||1.5||1.2 to 1.8|
|Japan – short fed||1.5||1.2 to 1.8|
|Japan – long fed||1.3||1.0 to 1.6|
*It is important to know the market specifications for finished cattle to determine the specifications of the store cattle entering the feedlot.
The above data shows averages achieved for purchased store cattle, higher gains may be achieved with own cattle.
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