Speerstra is very positive about feeding rumen bypass amino and fatty acids to dairy cows. “In pig and poultry farming, syn- thetic amino acids in feed are already used with considerable success. Feeding cows based on which specific amino and fatty acids they need concentrates the ration, improves nitro- gen efficiency, reduces methane emissions and contributes to more well-balanced milk fat. We’re not yet ready for this in the Netherlands. In the United States, however, they’ve been working with this for some time.”

Feed additive prices Feed additives are not cheap. Prices vary from € 125 to € 500 per 100 kilogrammes. “You can’t compare these prices with those of regular feed,” says Eric Heemskerk, director at Ingenieursbureau Heemskerk. “They’re used in very small quantities and they can save considerably on other expensive sources of protein, such as soy or rapeseed.” “By properly feeding a cow, you actually feed the rumen bac- teria,” says John Vonk, product developer at Ingenieursbureau Heemskerk. The company sells a slow releasing rumen nitro- gen in the Netherlands, Belgium, and Germany. “By keeping the amount of urea in the rumen constant and minimal, you synchronise the protein and carbohydrate supply, which

makes rumen bacteria grow better. This applies particularly to the bacteria that break down cellular walls, so that the cow digests the ration better. If there is enough available energy, the cow makes better use of the feed protein.” The minimal dosage of 100 grammes per cow per day can re- place 600 to 1,000 grammes of protein-rich feed, such as soy or rapeseed meal, and it reduces nitrogen excretion by at least 2.5%.

Controlling rumen processes “Controlling rumen processes is crucial for proper protein use,” says Speerstra. “The rumen is responsible for about 70% of a cow’s protein supply. The composition of a microbial pro- tein which is formed in the rumen is the most suitable for a cow to convert into milk protein. Essential oils inhibit the ac- tivity of hyper ammonia producing (HAP) bacteria and the di- gestion of protein in the rumen. This increases protein use and reduces ammonia emissions.”

Additional energy at the gut level Rumen bypass fats yield additional energy at the gut level and maintain the energy-protein balance in the ration. “This improves protein use,” says Robert Meijer, marketing and

Table 1 – Seven groups of feed additives with different effect to reduce N excretion. Type

What is it? saponins essential oils tannins

bio-active substances from plants

aromatic extracts from plants

tannins in plants such as clover or esparcette

rumen resistant rumen resistant lysine amino acids

and methionine yeasts

live or fermented single- celled microbes

slow release urea urea that is gradually released in the rumen

resistant fat How does it work?

work against protozoa that eat rumen bacteria and convert bacterial protein into ammonia


less ammonia and more microbial protein in the rumen leads to lower urinary N excretion

inhibit the activity of rumen bacteria that less ammonia in the rumen leads rapidly and quickly form ammonia

to lower N excretion

bind to proteins and thereby inhibit protein breakdown

more lysine and methionine available at the gut level

less protein breakdown and rumen ammonia leads to lower N excretion

with less protein in ration just as much milk production

improves rumen environment, growth of better digestion leads to more milk microbes and fermentation substrate in the rumen

and lower N excretion

provides extra N of microbes in the rumen with negative RDP in ration better digestion and more microbial protein

rumen resistant fatty acids supplies extra energy to the cow without extra N in the ration

more milk (protein) and lower N excretion in urine

Proof • works on a laboratory scale

• results between cows vary (depending on basic ration, dose and adaptation of microbes • works on a laboratory scale

• results in cow vary (adaptation of) microbes has been little researched • a lot of interest in the application of

tannin-containing products • a recent meta-analysis shows a positive result • variable results, most positive with

really low protein rations • methionine as such can also have positive health effects

• much studied in cows, effect varies from none to positive

• most positive with high-concentrate and/or low-structure ration

• positive result only in the event of a

shortage of rumen-degradable protein • no added value compared to feed urea if it can be provided several times a day • much studied in cows, mostly positive

result • most resistant fats increase saturated fatty acids in milk: negative for cheese quality

8 ▶ ALL ABOUT FEED | Volume 29, No. 1, 2021

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