PKE is a dry, gritty meal with a soapy smell and has low palatability until cows get a taste for it. However, PKE has reasonable levels of energy (ME) and protein, and is relatively easy to introduce to cows over a range of farm systems.
The profitability of PKE is dependent on the price of PKE relative to milk price and the utilisation of PKE and pasture.
Is palm kernel a low digestibility feed and should it matter?
There is no single, ideal measure of feed quality. However, in New Zealand, metabolisable energy (ME) is the factor limiting milk production in the majority of situations. Therefore, ME content (MJ/kg DM) is the best measure of feed quality for most farmers to use. It does not matter whether a supplement contains fibre, starch or sugar. The cost of each MJ ME should be how you decide which supplement to purchase.
Palm kernel extract contains about 11.0 - 11.5 MJ ME (mechanically extracted) and is, therefore, a reasonable quality feed for dairy cows when short of pasture.
Question: I have been told that palm kernel extract (PKE) should be avoided as a feed for dairy cows because it has a low digestibility (approximately 50%) and, as a result, will not promote the growth of rumen microbes. Should I buy a different supplement?
Answer: No, and here's why.
Cows survive and produce on:
a. The waste products of rumen fermentation (volatile fatty acids)
b. The micro-organisms that have grown during rumen fermentation, and
c. The feed that was not fermented (i.e. bypasses the rumen).
As a result, there are multiple measures of feed quality, including:
- How much is digested (digestibility)
- How much energy is available for production (metabolisable energy or net energy)
- How much protein is in the feed (crude protein, true protein, soluble protein)
- How much fat is in the feed
- Minerals and vitamins.
All of these are important to varying degrees, depending on what is lacking from the diet.
The digestibility of the feed refers to how much of the feed is digested in the rumen (rumen digestibility or rumen degradability) or along the entire digestive tract (dry mater digestibility). The rumen digestibility of a feed is important for determining the growth of rumen micro-organisms. These supply protein and some energy to the cow. However, there is a long digestive system after the rumen, in which proteins, fats and some sugars are digested and absorbed. Therefore, dry matter digestibility is a better measure of feed quality as it takes into account the whole digestive system and not just the rumen. Metabolisable energy is estimated from some measure of dry matter digestibility.
Protein is important because it provides the rumen micro-organisms with nitrogen to grow, the protein that bypasses the rumen is used directly by the cow, and because it also provides some energy.
Fats and oils cannot be used by the rumen micro-organisms and, therefore, do not promote microbial growth. They are instead used directly by the cow as an energy source.
What about PKE?
Palm kernel is not very digestible in the rumen. Estimates of rumen digestibility range from 50 to 60%. However, this does not accurately portray the feed value of PKE for dairy cows. The feed value in PKE comes from the ruminal digestion of fibre, some ruminal digestion of protein (55 to 60%), the protein digested in the small intestine (40 to 45%), and the fat, although the minerals are also important.
In the vast majority of situations, grazing dairy cows are short of ME. They are only rarely short of metabolisable protein (that is protein that reaches the small intestine). Therefore, changing supplement to increase the growth of rumen micro-organisms to further increase metabolisable protein will not be beneficial.
Metabolisable energy is the most important measure of feed quality for New Zealand farmers. Laboratory analyses indicate that PKE has an ME of around 11.5MJ/kg DM because of its relatively high fat content, its reasonably digestible fibre, and its protein content. However, as PKE is a by-product, this figure will vary and farmers are encouraged to have their feeds tested by a reputable laboratory. The practicalities of what supplement can be fed should be considered (e.g. liquid vs dry feed, in-shed feeding vs feeding in paddock). Supplements should only be offered to cows that do not have sufficient pasture (i.e. residuals are less than 7 to 8 clicks on the plate meter) and every effort must be made to minimise wastage.
What is the Fat Evaluation Index (FEI)?
A Fat Evaluation Index (FEI) Grading System was introduced by Fonterra in 2018. This index was designed to indicate the suitability of the milk fat composition for processing into a variety of products.
Below is information collated by DairyNZ to help farmers understand the FEI and manage their PKE feeding levels so that their milk is fit-for-purpose. For more information on the FEI, why it was developed and the demerit system visit the Farm Source website or contact your local Farm Source Team or 24/7 Helpline 0800 65 65 68.
What is the main driver of FEI?
The main driver of FEI is the amount of PKE fed and the PKE fat content. PKE fat content can vary from about 3 – 10% with region, origin, supplier, or shipment.
What other factors can affect FEI?
There are other factors that affect the FEI which is why one farmer may be able to feed more PKE compared with another without incurring a grading. In order of impact these are:
- Amount of PKE that is being fed as a proportion of the total diet. For example, there will be less chance of grading if 3 kg PKE is being fed to a cow eating 18 kg in total, compared with a cow eating 15 kg.
- Other feeds in the diet. Recent research suggests when high levels of fodder beet (5 kg DM) and potentially other feeds high in sugar/starch are fed along with PKE, this can increase FEI levels; however, the increase is small in comparison to the increase from PKE in the diet.
- Poor transitioning onto crops (e.g. turnips and fodder beet) can cause a short-term increase in FEI levels
- Stage of lactation (late lactation), breed of cow (Jersey) and OAD milking can all cause small increases in FEI.
How can I manage my FEI?
- Continually monitor your FEI graph. If you start to approach a B (orange band) check how much PKE is being fed (consider weighing feed when loading) and consider what else you are feeding your cows.
• Consider an alternative feed (e.g. more pasture or a different supplement/PKE blend). Be aware of pasture allocation and round length, and the economics of feeding different supplements.
• In winter/spring, feed PKE to dry stock and allocate more pasture/silage to lactating cows (NB. Avoid high levels of PKE close to calving. PKE is high in phosphorus and can increase the risk of milk fever).
• In summer/autumn, dry off stock and feed PKE to dry cows and/or remove cull cows earlier leaving more pasture/alternative supplements for lactating cows
- Be sure to check your FEI graph when a new load of PKE is bought on farm. The fat percent of PKE batches can vary and alters FEI levels.
- Be aware how much PKE is being fed as a proportion of the diet. A cow eating 3 kg PKE out of a total diet of 15 kg will have a higher FEI than eating 3 kg PKE out of 18 kg. Total intake can be affected by weather, and quality of other feeds in the diet.
- Transition onto crops following best practice management and avoid feeding high levels of fodder beet (e.g. 5 kg DM) if PKE is also being fed.
- Check FEI levels when switching cows to OAD or changing other feeds in the diet, particularly, if feeds high in sugar or starch are added.
DairyNZ's investment in research
As a farmer-funded, industry good organization, DairyNZ is tasked with helping farmers understand and respond to any changes in the dairy industry such as new guidelines and recommendations.