Figure 2 - Average daily feed intake of pigs fed a control diet (Control), and a control diet supplemented with common bitter feed additives (Bitter), including essential oils and antimicrobials. 950


Control


900 850 800 750 700 650 600


Bitter


No additives 0 12 Source: Lucta internal data.


Bitter additives added


34 Days


56 7


Lupins grown on a field to be used in pig nutrition. Lupins have a moderate decreasing effect on feed acceptability.


• Variability between life stages and breeds: Thresholds of bitterness tolerance vary with life stages as a result of dietary adaptation. For piglets, especially at wean- ing, it is crucial to avoid bitter compounds in feed in order to maximise intake. There are also significant variations in sensi- tivity among breeds because of polymorphisms in bitter taste receptors that vary with genetic background. As a conse- quence, acceptability of formulations containing certain bitter tastants can be quite variable and unpredictable. • Increased use of functional ingredients: The majority of drugs and functional additives used as alternatives to anti- microbials have bitter compounds. However, their usage is often necessary and, therefore, unavoidable.


Overcoming bitterness Bitter compounds present in commercial feed decrease feed intake and, consequently, growth performance. One possible solution is to allow pigs to adapt to bitter compounds, but this takes time (see Figure 2) and usually involves a high risk of weight loss. Alternatively, it is possible to minimise the inclusion of bitter compounds in feeds. However, due to the dynamic nature of commercial feed for- mulation, driven by market price fluctuation and ingredient availability, and the great complexity of bitter taste sensing, this strategy is extremely time-consuming, expensive, and has a limited success rate. It is, therefore, critical to find alternative solutions that allow a quick response to reduce bitterness perception and maximise feed acceptability.


Table 1 – Bitter components in feed and their impact on feed intake.


Non-toxic bitter compounds Main source


Plant derived ingredients Lectins and Kunitz Trypsin inhibitor Soybean (raw) Lectins Tannins


Fibre components (lignin?) Gossypol


Cyanogens Cassava Glucosinolates Alkaloids


Non-starch polysaccharides Chlorogenic acid Saponins


Feed additives* Antibiotics


Essential oils Plant extracts Plant-secondary metabolites


Sucrose octaacetate * Lucta internal data


Decrease in feed acceptability


High Beans – phaseolus (raw) Cottonseed meal Rapeseed meal


Potato protein, lupins Lupins


Sunflower meal Soybeans, beans, alfalfa Pharmaceutical compounds


Antimicrobial/anti- inflammatory/ antioxidant additives


Antimicrobial/anti- inflammatory/ antioxidant additives


Antimicrobial/anti- inflammatory/ antioxidant additives Pesticide/Herbicide


Very high


Sorghum High Oats


Very high Very high High


Very high Very high Moderate High


Low or not consistent High High High


High High


▶ PIG PROGRESS | Volume 34, No. 5, 2018


9


Average feed intake (g/pig)


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