Improving feed and water palatability for poultry
Through the addition of flavours, more palatable feed is more easily digested than less palatable feed and thus will have greater conversion efficiency. The addition of feed flavours also helps to prevent ‘starve outs’ in very young chicks and keep chickens ‘on feed’ until they gradually increase their consumption of feeds that they initially avoided.
Although chickens have fewer taste buds than other animals – 316 in chickens compared to 20,000 in pigs and cows – they still have a well-defined sense of taste and will accept or reject certain ingredients, such as blood meal, fish solubles and fermentation byproducts, or dusty ground grains, like wheat and sorghum.
Certain natural feedstuffs are relatively unsuitable for chickens because they are not palatable. For example, chickens tend to avoid diets high in barley, rye or buckwheat compared with similar diets containing yellow corn. They also tend to avoid diets containing unusual ingredients, such as single-cell proteins, fruit processing waste, marine flora, etc., compared with diets providing the basic nutrients from natural feed materials.
Even with natural feeds known to be highly palatable, there may still be spoilage factors that adversely affect palatability due to fat rancidity, sugar moulding and protein putrefaction, particularly when the feed is used after a long storage period. A deterioration of these important nutrients will produce flavours and odours that are not acceptable to the birds, representing a key factor in poor feed performance.
Flavour problems may also exist in freshly-produced feeds. Oftentimes it is impossible to produce highly uniform palatability in different feed batches without the use of flavouring aids. This is due to varying by-products, different soil and crop conditions, and varying manufacturing processes. Feed additives used in different batches may also contribute to a change of flavour. The fats, for example, may have been provided from inedible animal grease with various impurities resulting in contamination and feed vapidity. Similarly, vitamins and minerals may be provided in premixes having off-flavour carriers and bases, all factors that are conducive to ‘taste shock’ changes in feed intake.
Natural vs chemical
Flavouring agents may be either natural, like garlic, anise and black cumin, or artificial, such as fruit extracts and chemical products, including vanillin and sodium glutamate, etc. Most of these substances are provided in a dry powder form contained in free-flowing, non-electrostatic matter which may be pre-mixed and added to feed along with other trace ingredients.
Flavours are usually included in the diet at levels ranging from 0.5-1.5%. These levels may be adjusted, however, according to the type of feed ingredient used in the diet, how long feed has been stored, water quality and disease outbreaks – all of which require special flavour treatments.
Effects on GI tract
Flavouring products that contain sweeteners, such as Pollstress and Metostim, were found to reduce inflammation in intestinal cells and offered intestinal antioxidant properties, in addition to their roles in energy supply and osmotic balancing. Other flavours, such as garlic powder, may interact with the gut endocrine system and hence are able to stimulate a selective population of intestinal cells and cause enlargement of the intestinal villi, particularly in the duodenum section, with a resultant increase in absorptive capacity.
Further studies have shown that the addition of a natural flavour, such as black cumin, to the broiler diet at 10 g/kg can stimulate digestive enzymes in the intestinal mucosa and pancreas that improve the digestion of dietary nutrients and feed efficiency, subsequently increasing the growth rate. With other spice-based feed flavours, it was reported that protein retention and energy utilisation for productive purposes can be improved in diets formulated with 2.5% less protein and energy.
Heat stress, immunity and fertility
Studies have shown that black cumin also plays an important role in alleviating heat stress in birds, improving immunity to infections such as Newcastle disease and coccidiosis, and stimulating the thyroid gland, thereby increasing the fertility of male chickens.
Some feed flavours were found to improve egg production. In a study with garlic powder, for example, hens fed 1% garlic powder produced 9% more eggs compared with those in the control group. They also demonstrated an increase of 3.5, 0.6, 0.3 and 2.7 g in egg weight, yolk weight, shell weight and albumen weight, respectively, with the elimination of the off-flavours that are usually detected after long storage periods, even at low temperatures. Garlic powder may also lower the cholesterol level due to the release of the compound allicin, which alters the metabolism of egg yolk cholesterol, in addition to its roles as an antioxidant, antimicrobial and immune regulator.
Meat quality
Feed flavours appear to have beneficial effects on reducing the formation of undesirable cholesterol in the carcass. Studies with garlic powder, for example, indicated that its addition to the diet resulted in increased activity of the enzymes that convert cholesterol into bile acids, eventually being catabolised in the body so that a negligible amount is deposited in the carcass. The fishy smell in chicken meat can also be eliminated by feeding diets mixed with garlic powder at 0.2% of the diet, with no adverse effect on chicken growth.
Recently, black cumin was incorporated in rations for broiler chickens at 500-2,000 ppm. The results indicated that adding black cumin to the feed was effective in controlling infection of the carcass with bacteria species such as salmonella, streptococci and staphylococci. Besides, the seeds contain considerable quantities of tocopherols and allied bioactive compounds, such as phytosterols and thymoquinone, which are important in enhancing the overall antioxidant capabilities of the body and act against various stresses, immune dysfunctions and other complications.
Feeding a mixture of seasoning spices, such as cloves, ginger, sweet pepper, etc., at 0.2-0.5% in the diet of broilers twice daily for 10-15 days before market not only stimulates the appetite of the chickens but also improved the quality of the chicken, making it taste better and keeping it fresher for longer. Owing to the dual antiseptic and disease-prevention effects of these spices, they can improve the quality of the meat and extend its shelf life.
Water flavouring
Studies suggest that birds are much more sensitive to flavours in water than in feed because they consume almost twice as much water as feed. Generally, birds prefer water that is slightly acidic or supplemented with thiamine and sugars, for example, while rejecting other flavours, such as xylose and saccharine.
Some flavours, such as strawberry, alfalfa, nutmeg, honey, molasses, mushroom and wild cherry, were rejected outright, while birds would drink certain other flavours, including butter pecan, butterscotch, raisin, coconut, grenadine, patchouli oil and colocynth pulp – sparingly at first, but gradually they accepted the flavour. It should be noted, however, that products with a given flavour may not always be compatible with a bird’s taste preferences. This suggests the need to try different products to ensure that they do not lead to a reduction in water consumption or an unwanted decline in production.
