The quality, nutritional profile and digestibility of all feedstuffs dictates an animal’s ability to maintain their health and condition and produce meat, milk or eggs.
Raw materials used in diet formulations can be a source of contamination, so care is needed to only use good quality feed materials from reliable sources. Care in the selection of feedstuffs is needed to provide the best possible diets, especially in times when raw materials are short.
Cereals and legumes are grown under highly variable weather and soil conditions, which dictate the plant’s ability to accumulate nutrients and mature appropriately ready for harvest. Soil conditions vary widely, due to pH, topsoil depth and fertiliser history on farm. Plants, like animals, need balanced nutrition to allow them to produce the best seeds, whether that be grain or legumes. Where chemicals, such as superphosphate, have been used extensively, this can cause soils to become acidic, which will lock up inorganic minerals, making them unavailable for uptake via plant roots and poorly expressed in feedstuffs. Poor root/nutrient interactions deplete topsoil and biological activity and the microbes involved are essential for transforming nitrate into a form that can be utilised by the plant to build protein.
Harvest conditions affect whether there is good yield as seed fill (starch plus protein) and the presence of mycotoxins and anti-nutritional factors. When determining quality of cereal grain, these are assessed by the uniformity of packing protein and starch into the seed. If weather is very dry pre-harvest, grain will lay down non-starch polysaccharides surrounding the nutrient-rich endosperm to prevent dehydration of the contents and protect the germ, but these act as anti-nutrients. In legumes, poor harvest conditions can lead to useful protein becoming bound to indigestible lignin, which makes it unavailable to the animal. There are many ways to assess nutritional value used in the human food and animal feed industry to ensure they are fit for use. For example, the starch/protein matrix in hard bread wheat is measured to ensure the loaf will rise properly.
Formulating stockfeed quality to meet animal nutritional requirements
Where feedstuffs are defined as ‘good quality’, they typically have uniform laydown of useful nutrients, giving better digestibility, but when harvests are poor this is drastically reduced. In addition, the variety grown (and there are many) all show variability in nutrient profiles and accessibility to the animal’s own breakdown mechanisms. So, both harvest conditions and genetics play a role. However, the use of technical feed ingredients can maximise both nutrient availability and their overall digestion. This allows higher nutrient values to be attributed to the feedstuff in formulation. Certainly, specific feed enzymes to remove anti-nutritional factors that interfere with digestion are routinely used in monogastric diets and have been shown (although remain under-utilised) to be beneficial in ruminants. Typical of these are the beta-glucanases and xylanases that increase access for the animal’s own enzymes. In legume meals, proteases are applied to assist with digestion and are especially effective where they have uneven nutrient laydown or are bound due to poor weather. Fibre fermentation (and concurrent vitamin production) can be enhanced by using live yeasts, pre and probiotics to balance and promote the rumen or hind gut microbial profile.
The presence of contaminants from the field can cause dramatic problems in animals which ingest them. The most obvious is the presence of mycotoxins from fungi. These are invisible and difficult to analyse accurately, as they form ‘hot spots’ within large volumes of raw materials that indistinguishable from unaffected areas and are easily missed. The toxins are found on pasture, preserved forage and all harvested feedstuffs and by-products from the food industry. There are several major mycotoxins that contaminate harvested grain and legumes, mostly in combination. The dairy industry uses aflatoxin residues in milk as an indicator of contaminated forage or feed, but this is variable and not always reliable. Such toxins cause oxidative damage to cells and tissues, inhibit reproduction, immunity and nutrient utilisation, especially in the liver. Fortunately, there are modern mycotoxin binders that prevent uptake from the gut, and these can be used to add ‘insurance’ to the diet to limit such problems.
All feedstuffs and diets should be stored in clean, dry, cool conditions, as, even if harvested or milled clean, contaminating entities are present all around us. Silos and storage areas must be cleaned and disinfected, ideally, to prevent subsequent contamination. Silos can harbour moisture which promotes spoilage, likewise augers and feeders. Using unsanitised water for cleaning can actually increase risks of contamination.
It is important to consider feed quality both at manufacture and on farm to make sure animals can derive the best they can from every mouthful.
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Author
Dr Lucy Waldron
Head of Nutrition and Technical Services
