Maximising Fibre Digestibility is Crucial to Improving Performance
With Jonathan Huxtable, Zinpro; Dr Dana Tomlinson, Zinpro and Professor Michael Van Amburgh, Cornell University
The more dairy farmers and nutritionists can improve fibre digestion and rumen microbial growth, the better cows will perform. This will be particularly important this year, with diets likely to be based on variable, often higher fibre first cuts, according to Jonathan Huxtable from Zinpro, opening a recent nutrition event organised by the company.
“Farmers will need to challenge their nutritionists to focus on fibre digestion to increase intakes and production,” he comments.
Professor Michael Van Amburgh from Cornell University suggests that nutritionists are only as good as the forage they are feeding. “They have to be able to work with both good and poor-quality forage and keep the rumen full of something digestible,” he explains, adding that low digestibility silage fills clamps but does not produce milk.
Professor Van Amburgh explains that NDF describes the material in the cell walls principally cellulose, hemicellulose and lignin with each digesting at different rates in the rumen. The higher the proportion of rapidly digestible material, the faster it will pass through the rumen thus promoting better intakes.
“NDF figures for forages can be artificially increased if there is soil contamination in the crop which increases ash content when analysed. In grass silages, this increase may be as much as 2-3% which is enough to impact digestibility and the overall dietary NDF. If cows don’t seem to be milking, it is best to get NDF assessed and to exclude the ash element and this might be worth considering, especially after a wet growing season.”
Professor Van Amburgh explains that digestibility drives rumen function and the formation of the rumen mat. He explains that while particle size is important, what matters is how fast those particles are digested.
When particles enter the rumen, they are colonised by bacteria which digest them, producing volatile fatty acids (VFAs) and gas. Particles of feed rise to the top of the rumen on this gas. As particle size declines due to rumination and digestion, gas production reduces, particles sink and move out of the rumen.
“What nutritionists need to ensure is that the diet provides sufficient NDF and that this is digestible. If we can increase the rate of digestion, several things happen.
“Firstly the rate of passage through the rumen increases which leads to higher dry matter intakes. Secondly, we see nutrient supply to the cow increase, both energy and metabolisable protein (MP). Faster digestion means there are more bacteria, and it is these bacteria that are the source of the higher MP and VFA production.
“As a guide, a 750kg cow needs 8.2kg NDF in the diet, about 1.08% of bodyweight, to ensure effective rumen fill. Remember that a significant proportion of NDF may come from high fibre ingredients other than forages. It is not forage that is important but NDF.”
All digestion in the rumen is carried out by the rumen microflora – particularly bacteria, fungi and protozoa. In general terms, the higher the population, the more effective and faster the digestion will be.
All micro-organisms perform key roles thus all are needed. By increasing the understanding of rumen function it is possible to influence performance, specifically by meeting the requirements of rumen microbes more accurately.
“If we can directly fuel the rumen microbes, we can improve fibre digestion and also protein utilisation,” explains Dr Dana Tomlinson from Zinpro. “One way we can do this efficiently is by increasing a product of digestion called Branch Chain Volatile Fatty Acids (BCVFAs) or Isoacids.
Dr Dana Tomlinson, Zinpro
“BCVFAs are essential nutrients required by the fibredigesting bacteria. They are needed to produce the essential microbial protein that is utilised by the cow to produce milk and muscle. As much as 25% of microbial protein comes from BCVFAs. If we can increase this supply it will increase rumen efficiency, reducing the need for higher dry matter intakes to support higher production.”
Normally, fibre-digesting bacteria are supplied BCVFA through the digestion of rumen degradable proteins such as soya and rapeseed which are digested by the starch and sugar-digesting
bacteria. In essence, the fibre digesters rely on the starch digesters to break down protein and release the BCVFAs.
Dr Tomlinson says that this is an inefficient process as amylolytic bacteria can compete with fibre-digesting bacteria for the released BCVFAs, and quite often there are simply too few BCVFA available to meet the requirements of the fibre-digesters thus reducing fibre digestion and feed efficiency.
“If we can supply additional BCVFAs direct to the rumen we can ensure they are sufficient to meet the needs, so improving fibre digestion and rumen performance. Zinpro® IsoFerm® is a unique blend of these isoacids which is proven to significantly enhance the performance of fibre-digesting bacteria, increasing the efficiency of fibrolysis and NDF digestibility. By better supplying the requirements of the fibre digesters we can increase the digestion of NDF, improving intakes and MP supply.”
In a study multiparous cows were supplemented with Isoacids from 27 days pre-calving until day 90 of lactation, receiving the equivalent of 20g/cow/day of Zinpro IsoFerm when dry and 40g/cow/ day when in milk. Control cows received no Zinpro IsoFerm.
“The supplemented cows had a lower dry matter intake bit higher milk yield, higher fat percent, elevated protein yield and energycorrected milk (Figure 1). Despite eating less and producing more milk, cows receiving Zinpro IsoFerm were better able to maintain body weight in early lactation (Figure 2).
Field observations involving 70,000 cows in over 50 herds show cows fed Zinpro IsoFerm for 60 days or more had an average 2% reduction in DMI with a 4.3% higher energy-corrected milk yield, resulting in a 5.5% improvement in feed efficiency.
“...If we can supply additional BCVFAs direct to the rumen we can ensure they are sufficient to meet the needs, so improving fibre digestion and rumen” performance...”
Dr Tomlinson stresses that it is not a universal solution and that the benefits of Zinpro IsoFerm are better in diets where RDP is limiting and therefore BCVFA supply is limited. It also has a better effect where the diet is highly fermentable which leads to increased activity by starch and sugar digesters increasing demands for BCVFAs.
To optimise the effect of feeding Zinpro IsoFerm, Dr Tomlinson advises starting feeding during the transition period, feeding 40g/ cow/day. He explains that this is required to allow the cow to adapt its rumen and metabolism.
Figure 3: Effects of feeding Zinpro IsoFerm at different lactation stages on production parameters
“Figure 3 indicates the responses seen in cows fed when dry. We see better dry matter intakes in close up and early lactation cows when we want to achieve high intakes. In late lactation, we see DMI reduced as cows are meeting their requirements more efficiently.
“With heifers, we see less of a yield response, but animals are still growing, and we see improved bodyweight gains throughout lactation.
“Milk yields are better throughout lactation due to rumen bacteria working more efficiently. We are seeing 12-15% higher peaks and improved persistency. Body Condition is also better which has benefits for fertility.
“Zinpro IsoFerm is designed to be used strategically. It’s not for everyone, as some diets are not a good fit, there’s just little or no need for it. But where the conditions are right the responses can be significant.”
Fuel the cow by feeding her rumen. Zinpro® IsoFerm® is a breakthrough –the essential nutrient your herd needs.
Designed to enhance rumen function by directly feeding the fibre digesting microbes, Zinpro IsoFerm improves fibre digestion and protein utilization while ensuring on-farm sustainability. This proprietary isoacid technology increases milk yield, production efficiency and profitability.
To embrace the new frontier in dairy nutrition, scan the QR code or contact Jonathan Huxtable : jhuxtable@zinpro.com
