As part of my Nuffield Farming Scholarship I have been travelling the globe to research, first hand, my topic of ‘Increasing Rumen Nitrogen Efficiency in UK Dairy Production’. It has taken me to the United States, Canada, the Netherlands, Dubai, Australia, New Zealand and Ireland.
This blog follows my travels through North America, visiting New York State, Wisconsin, Colorado and finishing off in Ontario, Canada. During the trip I met some great farmers, farm consultants and researchers who gave me a brilliant insight into how they ration dairy herds.
New York State and Wisconsin
On my trip to NY state and Wisconsin I was lucky enough to travel to Ithaca and Madison, visiting two of the best dairy nutrition institutes in the world: Cornell University and the University of Wisconsin. Here I spoke at length to some of the key researchers about my topic, gaining great insight.
As well as research institutions I visited many dairies, quickly realising that every farm had both similar diets and high performance levels. The dairy diets in these regions are fully TMR based, made up of maize silage and alfalfa haylage/silage. Forage makes up 60-70% of forage of the diet, with 60-70% of this coming from maize silage. The herds were constantly performing at 40-45 litres/cow/day, with many boasting the 100lb/day figure. In the past, we have used the excuse that the US achieved these results using BST, but with public pressure many farms have stopped its use and retained high outputs.
The US can grow vast, consistent crops of maize silage – these are predominantly GM, but their digestibility traits allow for higher starch and fibre availability in the rumen. Brown mid-rib corn silage (BMR) was often selected for its lower lignin and stalk percentage, making it more concentrated. This homegrown corn, combined with high quality alfalfa makes a palatable and highly fermentable diet with ample structure.
So what can we learn from their diets?
The key to increasing rumen nitrogen efficiency is reducing the cow’s nitrogen (protein) and increasing fermentable carbohydrates in the rumen to increase microbial protein synthesis. To effectively increase dietary starch and sugars, fibre must also be accurately managed to prevent acid loading.
Fibre and NDF
Firstly, we must understand the NDF fraction of our forages better. The US have great quality Lucerne, however, whilst speaking to researchers over in the states it became clear that they were envious of our perennial ryegrass silages. When we produce high quality grass silages, they are far more digestible than Lucerne, with faster pool of NDF digestibility. These high quality silages should be treated more as a concentrate, with diets balanced accordingly. We are lucky to have a large supply of rumen degradable protein within our grass silages, and ought to take advantage of this rather than purchasing additional mid-quality protein sources.
Through maintaining ruminal NDF levels and rumen fill, SARA can be prevented. This can be achieved through slowing the passage rate and adding to the slow pool NDF – nutritionally improved straw (NIS) offer a solution. To successfully reduce acid loading, we must reduce lactic acid levels within out silages. Making drier, younger silage is key, yet the addition of additives including Buchneri offers an opportunity to convert some lactic acid to acetate and propylene glycol.
In most UK diet scenarios, rumen fermentable carbohydrates are a common limiting factor. To overcome this, we need to increase dietary starch and sugar levels without increasing acid loading. In the States high moisture corn and steam flaked corn are used on top of their maize silage. Whilst maize silage is a brilliant crop that should be grown wherever possible in the UK, most of our dairies would still have limited/no maize silage within their diet. Wheat remains our core starch source, seen as a highly fermentable carbohydrate that we should more actively exploit. Feeding more rolled/ground wheat is key, as ground maize offers an option in some scenarios but is relatively indigestible and passes through the rumen too quickly.
US diets are run at lower crude protein (CP) levels, averaging approx. 16% CP. Their milk ureas are between 140-180 mg/l, indicating far higher nitrogen capture within the rumen and increased conversion to milk protein. Dietary CP can be decreased without adverse impact to milk production and increase nitrogen efficiency, as long as the cows metabolizable protein requirements are met. To meet MP requirements, the targets are as follows:
- Feed the rumen sufficient RDP and fermentable energy to maximise microbial protein synthesis
- Increase DUP in the form of protected proteins e.g. protected soya
- Balance amino acids and supplement the shortfall
In summary, there is a great deal to learn from how the North Americans feed their cows. Whilst we don’t have the climate to grow the forages they do, we can adapt our own forages to their techniques. For this to be successful, however, we must model these diets correctly and gain a better understanding of dietary components.
Read Iwan’s next blog where he asks ‘Do we have the correct cow in the UK?’