Accurate estimations of total dry matter intake (DMI) and pasture DMI (PDMI) are fundamental aspects in determining the performance of livestock on grazing systems.
Grazing systems increase the difficulty in estimating DMI compared with confinement feeding systems.
Several models have been developed to predict DMI based on animal characteristics alone or with feed nutritive factors. However, most of these models have been developed under confinement feeding conditions, where forage selection is limited.
The estimation of PDMI has been a subject of much research, and many factors have been identified that influence intake, including pasture allowance, herbage mass, supplementation, herbage digestibility and animal body weight, among others.
Starting from the consideration that grazed pasture is the cheapest source of nutrients for the animal so that it should form the basis of profitable and low-input animal production systems, and given that, at least in most countries where the milk price is low, the management of efficient grazing systems allows to achieve low production costs, the development group at RUM&N designed and developed a new tool called NDS Grazing Assessment Tool.
The tool is designed to combine theoretical and empirical equations developed to predict the daily DMI for cattle grazing either grass, legume or mixed based-pastures, and offered differing levels of partial TMR (pTMR) with or without concentrate and/or extra-forages supplementation, thus can be useful for management and nutritional evaluations in different countries.
An upper limit to potential herbage DMI at grazing is set, which is considered to be the lower of two limits set by either physical (rumen fill) or grazing restrictions. Potential herbage DMI at grazing and the herbage allowance are then used to predict herbage DMI of cattle fed only pasture, using an empirical algorithm.
If pTMR or supplements are fed, substitution rate is predicted to calculate actual herbage DMI.
The NDS Grazing Assessment Tool should be useful for applied research, teaching and extension purposes, allowing a quick and practical understanding of the effects of feeding level, that is, pasture and supplements offered, on herbage DMI and related performance. It is also a tool to aid decision making around management strategies for the different cattle type.
Getting started
The NDS Grazing Tool is available through the Grazing tab that is located in the tabs line of the recipe screen:
In order to enable the Grazing tab the prerequisite is to define Grazing as location type in the Activity tab:
- Grazing for lactating dairy cow
- Intensive grazing or Continuous grazing for the other cattle types
Without the definition of the Activity such as Grazing, the tool will not work, that is the tab is not enable.
Another key step to be considered in order to get the tool working properly, is the inclusion of one Pasture Feed among the feeds included in the recipe.
To achieve this, you need to include into the recipe feed list, one forage classified in the Feeds section as green chop forage (fresh forage).
Then, the check box at the left of feed name have to be unchecked. This procedure allows the system to automatically invoke grazing calculations when you are accessing the Grazing tab.
As unique for the NDS platform, all the feeds included in the feed recipe list and marked with the check at the left of feed’s name are considered as delivered by the mixer wagon (TMR), while the unchecked feeds are defined as the feeds offered separately.
Through this feature, it is therefore allowed to set recipes for grazing animals in combination with TMR and/or separately supplemented with concentrates and/or extra-forages.
