Rapeseed oil cake feed: properties and applications

Rapeseed oil cake is a product obtained by pressing vegetable oil on screw presses from pre-treated rapeseed. It is a valuable protein supplement which, due to its high content of protein and residual oil, is successfully used in feeding farm animals. Rapeseed oil cake has high energy value and can partially replace more expensive protein sources in rations, but its use requires consideration of the content of anti-nutritional substances — glucosinolates and erucic acid.

Chemical Composition and Nutritional Value

Rapeseed oil cake is characterised by a high content of protein and fat. The content of crude protein in it is about 35–40%, crude fat — 10–18%, crude fibre — about 15–20%. The energy value of 1 kg of rapeseed oil cake is approximately 1.16 feed units and 11.34 MJ of metabolisable energy. The high residual content of rapeseed oil, rich in oleic acid, increases the metabolisable energy of the feed and allows additional vegetable oil supplementation in rations to be reduced.

The protein of rapeseed oil cake is well balanced in amino acid composition, although it is inferior to soybean meal in lysine content. Nevertheless, rapeseed oil cake is a cost-effective source of protein, especially for ruminants.

Regulatory Framework

Requirements for rapeseed oil cake as a feed product are established by GOST 11048-95 "Rapeseed oil cake. Specifications". The standard applies to rapeseed oil cake obtained by pressing vegetable oil on screw presses and establishes norms for the mass fraction of moisture and volatile substances (6–9%), as well as requirements for product safety. Indicators of the mass fraction of crude protein, crude fibre and ash are determined periodically in accordance with test methods.

Anti-nutritional Factors and Limitations

The main limiting factor for the use of rapeseed oil cake is the content of glucosinolates — sulfur-containing compounds which, under the action of the enzyme myrosinase, decompose to form isothiocyanates and other toxic products. These compounds can irritate the intestinal mucosa, suppress thyroid function and reduce weight gain in young animals. In addition, erucic acid may be present in rapeseed oil cake, an excess of which adversely affects the cardiovascular system of animals.

The content of isothiocyanates in rapeseed feeds must not exceed 0.8% calculated on an absolutely dry and fat-free basis. Modern rapeseed varieties of the "00" and "canola" types are characterised by low content of glucosinolates and erucic acid, which allows the inclusion rates of cake in rations to be expanded.

Feeding Rates

Cattle. Rapeseed oil cake is most appropriately used in cattle feeding. The small amounts of glucosinolates contained are inactivated in the rumen, so they are less significant for ruminants than for monogastric animals. The amount of cake from "00" varieties must not exceed 2 kg per animal per day, or 20–25% of the ration. Daily feeding rates of rapeseed oil cake are 0.5–1.2 kg for dairy cows, 0.4–0.6 kg for dry cows, and 0.4–0.6 kg for young stock over one year old.

Pigs. Rapeseed oil cake is used in pig rations to a limited extent — up to 5% due to sensitivity to glucosinolates, especially in young animals.

Poultry. Rapeseed oil cake from "00" varieties can be included in broiler feed in an amount not exceeding 12%, since above this level poultry meat acquires an unpleasant odour. For adult poultry, rates may be somewhat higher but are limited by low energy value and high fibre content.

Calves and Sheep. The share of rapeseed oil cake in feeds for calves and sheep is permitted up to 15%.

Usage Features

When using rapeseed feeds, sufficient iodine content in the ration must be ensured, since glucosinolates can disrupt thyroid function. The moisture content of rapeseed oil cake must not exceed 10%, otherwise fat oxidation occurs, toxic mould develops and the enzyme myrosinase is activated. In some cases, it is recommended to subject rapeseed oil cake to prolonged boiling for 1–2 hours to reduce the content of anti-nutritional substances.

Storage

Rapeseed oil cake is stored in dry, well-ventilated areas. The storage period of rapeseed oil cake is limited and amounts to about 2 months from the date of manufacture, due to the rapid oxidation of residual fat. During storage, moisture content must be controlled and mould development prevented.