What is GrassWatch?

GrassWatch is the weekly report compiled from Milk Yield from Grazing (MYFG) samples analysed through the Trouw Nutrition GB laboratory each week. The report includes information on grass growth data, grass quality, performance indicators and growing cattle, enabling advisors to discuss approaches to optimise health and performance.

Measuring Grass Growth

Weekly updates of regional and GB growth rates are collated from data supplied by AgriNet. This allows informed management decisions to be made throughout the season as grass growth rates vary.

Grass Quality

Samples submitted for MYFG reports are analysed by dry NIRS to determine a full nutrient profile, including NutriOpt parameters which can then be used to give informed nutritional advice.

Energy and Protein: The NutriOpt Dairy development on Metabolisable Energy (ME) and Crude Protein (CP) are Dynamic Energy (DyNE) and NutriOpt Digestible Intestinal Protein (NDIP). These are the total amounts available to the animal based on the products of fermentation and digestion, allowing precise determination of energy and protein supply from grass to maximise forage-rationing efficiency.

Rumen Balance: NutriOpt Fermentable and Energy Balance (NFEPB) is the balance of fermentable carbohydrates and proteins in the rumen. Understanding how and why the rumen is unbalanced means the diet can be modified effectively so that the rumen works more efficiently.

Rumen Health: Good rumen health means keeping a consistent rumen pH, which allows microbes to perform at maximum efficiency. The risk of acidosis increases during early spring because of both a high acid load and low fibre index, while the risk towards the end of the season is lower when acid load falls and fibre index increases (figure one). Rumen Unsaturated Fatty Acid Load (RUFAL) can be used to monitor the risk of decreased butterfat. High RUFAL levels alongside high acid load and low fibre index can increase the risk of decreased butterfat further.

Milk Yield From Grazing

Based on handfuls of grass submitted (to represent bite size)and spoilage a prediction of potential dry and fresh matter intake can be calculated, which when combined with energy, allows for a prediction of potential milk yield from grazing. This figure is determined by applying research from AFBI, Hillsborough into bite rate and hours at grazing into potential milk yield. Energy contribution from grazing is calculated from the current week’s average ME.

Performance Alerts

Butterfat factors

There are a number of factors that can contribute to decreased butterfat at grazing. GrassWatch utilises RFC (rapidly fermentable carbohydrate), acid load, fibre index and RUFAL intake to determine if cows are at risk. The individual nutrients are displayed in a traffic light system (low risk = green, moderate risk = yellow, high risk = red). This allows for knowledge of the cows and the system to be applied in order to determine the overall risk of decreased butterfat.

Temperature Humidity Index

The temperature humidity index (THI) uses average daily temperature and humidity values to calculate potential impact on cows throughout the season. As temperature and humidity increase these have adverse effects on behaviour, physiology and production potentially causing reduced DMI, poor conception rates and expression of oestrus and reduced milk yield.

Growing Cattle

Using the weekly average fresh grass ME, an estimate of the potential daily liveweight gain (DLWG) from grazing is calculated assuming that ad-lib grazing is sufficient to satisfy the daily DMI requirements.

GrassWatch Subscription

The current fee is: • If 20 or more MYFG samples per annum are submitted £0 • If less than 20 MYFG samples are submitted per annum £525+VAT

How to measure grass cover

A video explaining how to measure the grass cover in a field.


Contact Us

Our Ruminant team consists of:

Mark Hall - Technical Manager Ruminants

Alicia Wilson - Technical Sales Manager Feed Additives

Isabelle England - Technical Account Manager

Nacia Bonnick - Technical Advisor

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