KLAAS-JAN LEEUW, ARC-ANIMAL PRODUCTION INSTITUTE: IRENE
Oil seed plants, oil seeds, plant oils and oil seed cakes provide essential natural protein and to a lesser extend, energy, in livestock diets. Sunflower plants can provide all these components, in the form of silage, oil or cake meal, which is the remainder after the oils have been removed through processes such as cold pressing or extruding.
Substituting other cake meals (i.e. cotton, soy) with sunflower meal for livestock, are practices that is being done, but is limited by available amino acids and more importantly, by price.
Increasing demands for plant oils (consumption or biofuels) is leading to increased availability of oil cake meals; although not locally as yet, as can be seen by continued imports of oil cake. Research on the levels at which sunflower meal can be utilised into livestock diets is limited and is currently more driven by the price (R/ton) and nutrient composition (% protein/amino acid profile) of final diets.
Modification to sunflower meal through heat treatment, chemical methods (formaldehyde, enzymes) or saponification has been reported with varying degrees of success. Usage of all oil cake meals is also changing due to improved oil extraction methods; the lower fat/oil content in the cake will allow for higher inclusion into ruminant feeds. The availability of certain manufactured amino acids (i.e. lysine) will help address amino acid imbalance in sunflower meal. The methionine content of sunflower is almost double than that of soybeans.
Whole sunflower plant usage as silage is an alternative that can be used, but oil and cake prices are prohibitive. Sunflower silage does compare well with lucerne silage, with higher dry matter intakes and daily gains, but with similar feed conversion ratios.
To an even lesser extend, sunflower oil or other fats have been used to increase energy supplementation in ruminant diets. This is especially true for dairy diets, but the much lower milk production and dry matter intake of a beef cow might indicate that the results of dairy research might not be applicable to beef cattle.
The use of whole sunflower seeds to provide energy did not improve reproductive functioning in heifers and even resulted in lower ADG, probably due to the oil inhibiting fibre digestion.
Substituting barley with sunflower seeds in high concentrate diets can improve performance, but substitution in maize type diets showed no benefit or negative effect. With pressures to decrease the methane production of livestock in mitigation of global greenhouse gas levels, the addition of sunflower oil (as energy source) to cattle diets can reduce methane production by 22%, but it decreases NDF (neutral detergent fibre) total tract digestibility by 20%.
Oil content in sunflower seeds can vary greatly between dryland (34% to 39%) and irrigated lands (38% to 43%). Oil content in oil cake meals differs between oilcake producers and may be caused by a variety of factors, type of sunflower, press settings and processes.
The oil content of sunflower meal is, after price, the single biggest restrictor of inclusion into ruminant diets. If the total fat in a ruminant diet exceeds 7% of the diet, the fats/oils will intervene with fibre digestion and therefore negatively affect animal performance. For sunflower meal producers it will be important to supply cake with low oil contents, as this can lead to increased usage into diets for ruminants.
Sunflower meal has a low level of rumen by-pass protein as compared to cotton and soymeal. Sunflower meal can be treated chemically or by heat to reduce protein degradation in the rumen. Formaldehyde treatment of sunflower meal reduced N content in the urine but increased N content in the faeces.
Heat treatment of sunflower by drum roasting also reduces rumen digestibility of sunflower meal proteins. Saponification of high fat sunflower meal can aid in increasing the usage of sunflower meal in ruminant feeds. Levels of high fat or oils in ruminant feeds will intervene in fibre digestion and cause digestive problems for the ruminant.
Sunflower protein was of equal value to cottonseed protein in steer fattening rations. It also indicated that sunflower protein is only equal to urea as a supplementary N source for wethers fed corn silage rations.
Added to low quality grasses, sunflower meal does increase the quantity of all essential amino acids in the small intestine of sheep and microbial synthesis was increased with adding sunflower meal, but not with urea and this can be due to a lack of available energy in the rumen to utilise urea. In high concentrate diets, the rate of digestion might influence the type of protein source used, as the digestion rates differ between the different types of oil cake meals.
Sunflower meal can replace soybean meal in diets fed to growing goats, but may be further improved by the addition of fibrolytic enzymes. Recent work indicates that in vitro results show the principle very well, i.e. synchronised level of digestibility of energy and protein sources. However, in vivo trials showed no effect on ruminal fermentation.
Cotton seed meal in ruminant diets (CP between 10% and 12%) could be replaced by sunflower meal. Similar interchange between oilcake meal sources had no effect on performance in ruminants.
Work done on soybean meal in this context will illustrate some possibilities for sunflower meal. In work done at the ARC Irene, four diets with increasing levels of soybean meal (control: 6% cotton oil cake meals; 6% soybean meal; 13% soybean meal and 20% soybean meal in a high concentrate feedlot diet) were fed to steers.
The steers fed the 13% diet performed better than the other diets, while there was no difference between the other diets. Results indicated that more soybean meal can be included in ruminant concentrate diets (i.e. feedlot rations) without affecting animal performance. The CP content was 13,5%; 13,65%; 13,3%; and 14,8% respectively.
The supplement most commonly used with sunflower meal is L-lysine HCl. Other limiting amino acids in sunflower meal might be supplemented, but this will depend on: amino acid composition of sunflower meal, profile of total ration amino acids, and target group of the final feed (monogastric, ruminants and aquaculture). Further possibilities include promoting of high lysine maize cultivars.
Cost and availability are beyond the control of research, however by increasing research an increase in demand might be created which will influence cost and availability. As oil content is lowered in sunflower meal through improved extraction processes, processes such as saponification may become obsolete.
It should also be noted that the new high oil cultivars for use as a silage crop, do require new research. We are basically having a new product which will have different interactions with other feed components and will require research to quantify those. Heat and formaldehyde treatments increase the level of by-pass protein of sunflower meal in ruminant rations and plant breeding research can play an important role.
Reduced oil contents of sunflower meal caused by improved extraction processes, will result in a different oil cake which needs to be quantified in new research.
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