BY ALEX ASHWOOD

BRAHMAN NEWS DECEMBER 2008 Issue #161

By-product feeds are generally available seasonally in large quantities, frequently vary in composition and often incur a high transport and storage cost. Often by-product feeds are nutritionally imbalanced and contain inadequate or too much of a particular nutrient.

Correcting nutritional imbalances and examining the unit costs of feeds are critical to the cost effectiveness of the feed and its efficient use in cattle rations both for production and drought survival feeding.

BREWERS GRAIN

This is an energy and protein supplement. Its high protein (20-25%) content, high moisture content (75%) and reasonable fibre content (17%) make it a suitable supplement in high grain-low roughage diets. At $60-$80 per net tonne, the price on a dry matter basis is between $250-$320 per tonne.

• With a metabolyzable content of 9-10 MJ/kg DM, brewers grain compares favourable to low energy content grains.
• Brewers grain is not recommended for stock under the age of 4 months.
• Poor storage can cause moulds which product toxins that cause scouring and digestive disorders.
• Brewers grain can, however, be successfully ensiled but may cause effluent problems.
• Both salt and calcium supplements are required to correct the main major mineral deficiencies.

MOLASSES

The energy content of 10-12 MJ/kg DM, virtually nil protein, reasonable calcium and low phosphorus means that in low quality roughage diets molasses needs to be supplemented with protein and phosphorus. Molasses is sticky and heavy and difficult to handle.

• It is a suitable carrier for unpalatable feeds (eg urea, minerals).
• Production responses to molasses fed at 25-30% of total dry matter intake (TDMI) are 70% that of grain.
• Molasses efficiency drops off at levels greater than 25-30% of the diet and in rations where there are inadequate levels of roughage and protein.
• Molasses provides an important source of sulphur in diets containing urea and has adequate levels of potassium, copper and calcium.
• High intakes of diluted and fermented molasses can lead to livestock fatalities due to molasses toxicity.

WHOLE COTTONSEED (WCS)

Commonly known as ‘white’ or ‘fuzzy’ cotton, WCS is a useful source of energy (14 MJ/kg DM) and protein (22% CP).WCS is a very good source of several nutrients but has certain properties which restrict its use in beef cattle diets to 3kg per cow per day.

• Fed in large quantities for extended periods, it is a potential source of gossypol poisoning which causes damage to the liver.
• With hungry stock fed imbalanced rations WCS should be restricted to 10% of total dry matter intake (TDMI).
• Maximum levels of feeding are 20% TDMI, ie 2-3kg for medium framed cows.
• WCS should not be fed to calves under 4 months of age.
• The high oil content of WSCS (19%) also restricts high levels of feeding.

SUGAR CANE

The actual availability depends on crops surplus to mill requirements or damaged crops (eg frosts). A major concern is the possibility of pesticide intake if the cane is harvested too low to the ground and the soil contains chemical residues.

Sugar cane diets have much in common with molasses based diets. The principle source of energy is sugar and the protein content is extremely low (2% CP). With high fibre (NDF) levels, low digestibility, an ME content of 6-8 MJ/kg DM and low levels of all major and minor minerals, the production benefits of feeding cane depend on the quality of the accompanying ration (eg feed lot diet).

• Basically, sugar cane is a source of low digestible fibre and sugar and if fed adequate levels of supplements can comprise 25-30% of TDMI.
• Since it has high levels of sugar, precautions are necessary when feeding high levels of molasses.
• Suitable levels of production depend on the amount of grain, protein and minerals fed to livestock.
• High intakes of sugar cane (particularly frosted cane) can modify rumen fermentation and reduce digestion.

BAGASSE

This is the fibrous residue remaining after the sugar juices have been extracted from sugar cane. It is widely used as a fuel in factory boilers and in the landscape industry.

Spraying bagasse with a 30% solution of sodium hydroxide increases its digestibility from 30 to 50%. Treated alkali bagasse fed at 10% of the TDMI and supplemented with high levels of protein and energy has been successfully fed in feedlot situations but weight gains have been lower than diets with better quality roughages.

• The cost effectiveness of rations comprising of 20-25% ensiled and pelleted bagasse depends on the amount and balance of additional supplements (ie energy, protein and minerals).
• Due to the corrosive nature of caustic soda, alkali bagasse availability depends on commercialisation and the capacity to transport and store the treated product.

RICE BY-PRODUCTS

Rice bran contains 12.5% crude protein, 12% crude fibre and 13.5% oil and is an attractive feed when fresh. Rice polishings is a finely powdered material with a similar energy and protein values but lower in fibre than bran.

Both bran and polishing can replace up to 25% of the grain supplement. In “fast” grain diets (eg wheat), polishings need to be fed carefully. Rice hulls are not recommended since they contain high levels of indigestible fibre and have a low energy content (3.5 MJ/kg DM). The hulls also have sharp edges that cause irritation to the digestive tract.

NUT BY-PRODUCTS

MILLED ALMOND HULLS

The outer shell of almonds are hammer milled to produce a product with high levels of non effective fibre, low crude protein (5%) and medium levels of ME (10.5 MJ/kg DM). Unlike macadamia meal, almond hulls have a low oil content (2%).

MACADAMIA MEAL (M/M)

Macadamia meal is the by-product of macadamia shell and nut waste and provides an additional source of energy when fed to beef cattle. Since macadamia meal has a high oil content (15-20%) it is best fed in restricted quantities to cattle. High levels of fats/oils in the ration can reduce the digestion and intake of roughages and lead to reduced levels of production.

It is suggested that the maximum level of intake with stock grazing pastures and roughages is 10-15% of the total dry matter intake/day (TDMI). For example:

• A 500kg steer has a TDMI of 10-12 kg dry matter per day (ie 2-2.5% of body weight), this means 1-1.2 kg m/m can be fed per day (ie 10-15% TDMI).
• If feeding 3kg of grain/protein supplement to a 500kg steer, m/m can provide 30% of the supplement, ie 1-1.2kg m/m per day (ie 10-15% TDMI).
• Should a 500 kg steer be fed 5-6 kg grain/protein meal then m/m can provide 15% of the supplement, ie 1-1.2 kg m/m per day (ie 10-15% TDMI).

Some supplements and by-products already have high levels of fats/oils (eg whole cotton seed, palm kernel meal, bakery waste). With these feeds m/m intake should be restricted depending on the level of fat intake of the feedstuffs in the ration.

With high molasses diets (ie greater than 20% TDMI) the inclusion of m/m in the diet can compound the possible reduction of roughage digestion and intake.

Macadamia meal (m/m) like most by-product feeds has benefits and limitations. In pasture/crop based diets which contain 2-4% fat, m/m is best fed at a maximum of 10-15% TDMI to provide additional energy to improve production and weight gains.

VEGETABLE BY-PRODUCTS

Unless obtained and transported at low cost these products may not be economically attractive. Vegetable by-products need to be introduced gradually to stock and special care has to be taken to prevent overfeeding and digestive disorders (eg scouring). Choking can also be a problem with some vegetables (eg potatoes and pumpkins).

• Chopped sweet potatoes can be fed as part of the grain ration or substitute for silage. 1kg of sweet potatoes equals 2.3kg of sorghum silage or ½ a kg of grain (ie on a DM basis).
• Potato slivers are washed pieces of sliced uncooked potato. Their protein content is 8.0% CP and energy 12.5 MJ/kg DM. Maximum intake should not exceed 20kg fresh (20% DM) weight per cow per day.
• Raw potatoes are high in moisture (80%) and have an ME content of 11.5-12.5 MJ/kg DM, 8% CP and 2% crude fibre. Cows can eat 15-20kg per day of raw potatoes on an as fed basis. Potatoes are best fed in conjunction with a chopped roughage. Sprouted and green potatoes should not be fed to stock and care is needed to prevent choking.
• Pumpkins have a high moisture content (90%) and low protein and energy values, ie about half that of sorghum silage (8.0 MJ/kg DM, 7% CP).

FRUIT BY-PRODUCTS

Pineapple and citrus pulp are useful feeds although low in protein (6-7% CP) and high in moisture (80%). They nevertheless have a high energy value (12-13% MJ/kg DM). Fed at up to 12kg fresh weight per cow per day they are very beneficial to rumen function and intake in high grain-low roughage diets.

• Grape pulp mainly comprises of skins and seeds and subsequently has high levels of indigestible fibre with low availability of relatively low levels of protein and energy.
• Banana pulp depends on the degree of ripeness. Low in protein (6.5% CP) green bananas are a suitable source of energy (11 MJ/kg DM). At maturity bananas rapidly ferment into sugars and the nutritive value decreases substantially.
• Tomato pulp largely comprises of skin and seeds and subsequently a high moisture content (80%). It is a palatable feed supplying both energy (11 MJ/kg DM) and protein (20% CP). Due to its high oil content (15%) is best fed in conjunction with low fat feeds at up to 10kg of wet material per cow per day.

CEREAL BY-PRODUCTS

Hominy meal is the co product of maize milling. It has a high energy value (14 MJ /kg DM), 10% oil and 11% CP. It is a high energy feed suitable for all stock but needs to be introduced gradually to prevent digestive upsets.

• Bran and Pollard are co products of flour production. They are highly palatable and act as a bulking agent in high grain diets. They are an excellent source of energy (10-12 MJ/kg DM) and protein (14-18% CP) and are best fed as a proportion (25%) of the grain supplement.
• Cereal stubble are suitable sources of roughage with moderate levels of energy (6-8 MJ/kg DM) and crude protein (7-8%). They are important sources of long fibre with a high chewing index, ie effective fibre.

BOTTOM LINE

The use of by-product feeds depends on their availability, cost, nutritional value, palatability and most importantly the absence of undesirable contaminants (eg pesticide residues).

As with all new feed products, by-product feedstuffs should be introduced gradually over a period of 10 days to improve acceptance by stock and reduce the problems associated with digestive disorders.

In general, the feeding of by-product feeds will require some degree of supplementation to balance nutritional deficiencies. It should also be noted that some by-product feeds when fed in combination (eg high oil and high sugar content feeds) can accentuate feed disorders and nutritional imbalances.