Palm Kernel Extract is like ‘McDonalds for cows’ and serves a purpose when other feeds are in short supply – but is not a quality supplement, says Nutritech International’s animal nutritionist Stuart Lister.
“It’s like fast food for cows – it’s simple to feed out – you just have to ring up and have it delivered, and it can feed straight away, [be] fed today and not tomorrow as required.
“From a nutritional point of view, anything which can be broken down by the cow’s rumen bacteria is not a bad feed and when there’s a drought, PKE is better than fresh air.”
However, PKE is high in fibre and has a marked effect on the milk composition because it raises the fat in milk significantly, at the expenses of litres and protein.
“Fonterra’s payment for milk fat is worth up to two or three per cent less than protein and having high fat milk creates a lot of issues for processing.
“Fonterra’s call for farmers to voluntarily feed no more than 3kg of PKE per cow per day is all around the processing of milk.”
Stuart says the first rule of rumen nutrition is the cow gets only 20 per cent of the nutrition from the food she eats and 80 per cent of nutrition from what the bugs that eat that food produce.
“Looking after the bugs is paramount to the quality of the bacteria in the rumen.
“A lot of fibre in the cow’s diet causes bacteria to flood the fermentation process, producing a lot of acetic acid which in turn produces a lot of fat in milk. Cows fed on PKE also put on weight in the form of fat.”
Another down side is the fibre in PKE is short and so it can’t be returned to chew a second time – a process known as “chewing the cud”.
“That’s why only about 50 per cent of PKE is digestible because it goes in one end and out the other. “Long fibre, about the length of a cow’s mussel – the kind of mouthful she takes when grazing grass – is the ideal size.”
Chewing the cud is a vital part of the process because the cow gets more nutrients out the food by taking a “second bite”. While doing so she produces a huge amount of saliva, which Stuart says is the best thing to buffer the rumen helping keep the pH to the best level possible.
“The cow’s stomach is a fermentation tank and like any other fermentation system, it is a complex biological process.
“One teaspoon of rumen fluid contains more bacteria than all the humans who have ever walked the earth and science can probably identify only 40 to 50 per cent of those bacteria – there is still a lot of mystery in there.”
The effluent from cows fed on PKE definitely smells different from that of cows fed on grass. “It even look different. Grass-fed cows produce dark green effluent while PKE fed cows’ effluent is dull grey and effluent ponds it goes into get a fibre matting on them.”
Stuart agrees Fonterra’s voluntary limit of 3kg of PKE per cow per day is about right. His advice to farms is to feed up to 4kg for winter cows, but to withhold PKE from transitional cows three to four weeks before calving as can it can trigger metabolic issues.
“If you have Jersey cows eating high potassium grasses they can get milk fever if fed PKE as well. You can’t do anything about the breed or the grass; but you can do something about supplement to reduce the risks.”