CANOLA MEAL can be an important component of supplementary rations for grazing dairy cows and can play a role in increasing appetite, dry matter intake and milk yield compared to cows fed equivalent amounts of energy as cereal grain and conserved forage. That is one of the key messages from several experiments conducted by Agriculture Victoria researchers Martin Auldist and Bill Wales and their team at the Ellinbank Research Centre.
Dr Auldist said he was conﬁ dent that when relatively high amounts of supplement were fed, there was a milk production advantage to including components such as canola meal and maize grain in the ration, especially in early lactation. “When we feed less than about 8kg DM of grain, we don’t see any advantage to feeding a mixed ration or grain mix compared to feeding straight cereal grain and forage,” Dr Auldist said.
“Above that, though, we often see milk production advantages because higher producing cows have a greater requirement for nutrients other than the energy the cereal grains provide.
“We’re not saying that farmers should be feeding supplements at high levels. We recognise the importance of grazed pasture as a cheap feed source.
“This research is about ﬁnding better, more eﬃcient ways to feed supplements when grass is in short supply and farmers need to, or want to, feed increased amounts of supplements, even for a short time.”
As an example of the results Dr Auldist and his team have seen, he cites an experiment in which cows in early lactation were fed between 7.5kg and 12kg of a grain mix containing maize grain, canola meal and wheat grain, while receiving the rest of their diet as grazed pasture and conserved forage.
These cows each produced up to 5kg more milk per day than cows oﬀ ered equivalent amounts of cereal grain instead of the grain mix.
“Much of this milk response comes from additional dry matter intake,” Dr Auldist said.
“Cows consuming a diet containing canola meal appear more inclined to eat. Not only do they eat more supplement but they also graze harder when they get back to the paddock after milking. “Canola could be having these eﬀects because there is less propionate being produced in the rumen compared to when cereal grain is fed, which could partly remove satiety signals.
“Alternatively the canola could be providing a more balanced supply of amino acids, leading to more milk and an increased appetite.”
Canola probably isn’t the only component of the ration providing beneﬁcial eﬀects. Maize grain, in particular, is a source of starch that degrades more slowly than cereal grains such as wheat.
“A more slowly degradable starch source like maize leads to less accumulation of volatile fatty acids in the rumen, and a less variable ruminal pH that doesn’t drop as low. Low ruminal pH is known to interfere with both digestion and, indirectly, milk fat synthesis,” Dr Auldist said.
Despite the fact that canola and maize are more expensive supplements than cereal grain, there are times when it makes economic sense to feed them as part of a well-formulated grain mix, according to Agriculture Victoria researcher Christie Ho.
“Using long-term average milk and feed prices, these results show that feeding the grain mix is a proﬁtable thing to do in early lactation, compared to feeding cereal grain at grain intakes between 7kg and 12kg of grain per cow per day,” Ms Ho said.
All of the grazing experiments conducted by the team so far have been 28 days in duration. The next step is to extend that to a longer period.
“Most of the better responses have been in cows in early lactation,” Dr Auldist said.
“So we are currently running an experiment over the ﬁrst 100 days of lactation to see if we can maximise the response to these kinds of grain mixes over that time. After that the cows will go back to a common diet, but we’re hoping to see a carryover eﬀect in the rest of lactation.
“That’s what studies overseas have shown and if it happens in our system it will add to the economic beneﬁts of these rations.”