ENERGY IS THE KEY
The secret of efficient milk production relies on satisfying cow requirements. Cow comfort, proper management and adequate nutrition will pay back producers with robust fertility, consistent milk output and minimal incidence of health problems. Each of these depends directly or indirectly on the cow’s energy status.
A positive energy balance relies on feedstuffs of the appropriate quantity and quality, along with the type of environment and good management of critical phases like dry and transition periods. Energy demands can in fact rise based on climate, walking distances inside the farm, adequate space at the feed bunk and animal density.
However, it is undoubted, that feed quality and its utilisation by dairy cows play main role in cow energy balance.
Ruminants are special
From the cow’s perspective, the energy issue is not primarily related to milk production but rather to her survival.
Cows naturally produce milk to feed their calves. However, in the case of an energy gap, they will discontinue reproduction first and then milk production in the attempt to improve the likelihood of their own survival.
This explains why fertility and milk production fall when a cow’s energy demands are not satisfied. Nowadays, this situation is becoming more and more dramatic, as genetic selection in favour of increasingly productive animals results in animals which can produce more milk, but with higher management and nutrition requirements—particularly in terms of energy and protein.
It is safe to assume that cows are often in negative energy balance –expending more energy than is consumed— especially during the first part of lactation. While it is relatively easy to fulfil protein requirements by optimising the amino acids profile at the intestinal level, satisfying the energy requirement of a cow is a real challenge.
Cows, being ruminants, are very special animals. Their diet composition needs to contain a minimum amount of fibre to ensure proper health and to avoid diseases such as acidosis. Unfortunately, fibre does not provide them the same amount of energy as other feedstuffs e.g. grains, sugars or fats.
Ruminants rely on the rumen, a special part of their gastrointestinal tract, for around 70% of their energy. More precisely, energy is produced through the fermentation of feedstuffs by rumen microflora, a complex ecosystem made of bacteria, fungi and protozoa. Working in synergy to ensure their growth, rumen bacteria produce large quantities of volatile fatty acids (VFAs), as by-products of their metabolic activities, and these VFAs are the main source of energy for the cow.
To ensure a healthy population of microorganisms, we need to provide grains which are the main energy source for bacteria and fibre to stimulate rumen motility, rumination and saliva production—activities that are necessary to keep animals healthy.
How is it possible to improve rumen function and fulfil a cow’s energy demands?
First, we need to enhance fibre digestion. Fibre occupies a certain amount of space in the rumen, but is less fermentable and has a lower energy production capacity than grains.
One suggestion is to use forages with high fibre digestibility and to feed them especially to transition and first lactation animals, as they have a higher energy demand. In addition, good quality fermented silage and mould-free forages will favour intake and sustain rumen fermentations.
Considering grains and by-products, we need to be generous with them in order to cover the space remaining in the rumen after having satisfied the fibre requirements. A cow producing 32 kg of milk with a feed intake of 22 kg of dry matter should be fed at least 6 kg of starch and 1.2 kg of sugar depending on the quality of forages. This corresponds roughly to 20 kg of corn silage and 7 kg of ground corn plus 0.7 kg of molasses.
Quality feedstuffs should not have anti-nutritional factors, e.g. mycotoxins, that can make energy production less efficient. Mycotoxins reduce feed quality.
During the 2016 BIOMIN World Nutrition Forum, experts reported that mycotoxin contamination can reduce the quality and nutritive value of feedstuffs.
Mycotoxins are secondary metabolites of fungi and mould that widely contaminate grains, forages and silages. They exert a negative effect on a cow’s health, fertility, rumen microorganisms and rumen function.
In recent research conducted in South Asia, Kiyothong et al. (2012) showed that feeding dairy cows a total mixed ration (TMR) naturally contaminated with multiple mycotoxins can reduce the rumen bacterial population, as well as protozoa and fungi. This translated into a reduction in volatile fatty acids, leaving less energy available for the cows. The application of a mycotoxin deactivating feed additive was able to resolve the situation and increase milk production and fat percentage.
Conclusions on rumen health
The rumen is the main organ of energy production in cattle and the quantity of outputs depends on feedstuffs’ quality, rumen health and microbial balance.
A healthy rumen will be able to squeeze more energy from both forages and grains, giving more values to feedstuffs (silages and hays) prepared by farmers and to concentrates offered by feed millers.
For this reason, there is the need to optimise rumen function to keep rumen microbiota healthy. Key actions are to avoid drops in rumen pH, to favour beneficial bacteria growth and to avoid any poisoning substance such as mycotoxins.
Bunk management (proper and homogeneous mixing, adequate fibre particle size, proper humidity) is fundamental for rumen equilibrium. Also, stimulating rumen bacteria with proper prebiotic strategy (like with autolyzed yeasts) can ensure a better rumen environment, a more controlled pH and a higher energy output.
This article originally appearing in Think Grain Think Feed, Volume 3, Issue 11 in Sep 2017