Optimising the grazing system of pasture-based dairy cows with virtual fencing technology

Project details

Status: Completed

Project background

This project is linked to the Tasmanian Government funded project 'Virtual fencing: A game changer for pasture-based livestock system'.

Intensive grazing management is widely used in pasture-based dairy systems to improve pasture utilisation and increase forage production per hectare. This typically involves restricting pasture availability and allocating fresh pasture in 12 or 24 hour periods using temporary electric fencing (strip-grazing). While effective, these systems are limited by practical constraints such as labour requirements and physical infrastructure, which restrict the frequency and flexibility of pasture allocation.

As a result, current grazing strategies may not fully optimise pasture use or align with the natural feeding behaviour of dairy cows. Research has shown that cows graze longer and consume more pasture when fresh allocations are provided in the late afternoon, particularly after milking. This timing coincides with higher pasture quality, including increased water-soluble carbohydrates and lower fibre content, which can improve intake, rumination, and milk production.

Despite this knowledge, conventional grazing systems make it difficult to adjust the timing and frequency of pasture allocation to match these behavioural patterns. Virtual fencing technology offers a potential solution by removing physical and labour limitations, enabling more precise and flexible grazing management.

The focus of this research was to explore how grazing strategies can be optimised using virtual fencing to better align pasture availability with cow behavioural needs. The problem being addressed was the current inability of traditional grazing systems to efficiently match pasture allocation timing with peak animal intake behaviour, which limits potential gains in pasture utilisation and productivity.

Project activities

This experiment was conducted over one month during Spring 2024 at the Tasmanian Institute of Agriculture’s Dairy Research Facility (TDRF) at Elliott, north-west Tasmania.

The milking herd of 240 cows was divided into four groups each containing  62-63 cows with more than six months  experience with Halter virtual fencing technology. Groups were balanced for parity, milk production, days in milk, breed, weight and body condition.

Cows were milked twice daily and offered 17 kg of pasture dry matter each day supplemented with 6 kg of concentrate in the dairy, evenly split over two milkings. The four groups were allocated pasture according to one of two feeding treatments.

Cows in the control herds were moved to a new perennial ryegrass-based allocation after each milking. Cows in the optimised grazing herd were offered pasture three times per day according to the following schedule:

• 65% of the daily pasture allocation was offered after the afternoon milking (11 kg)
• 10% of the allocation was offered 1 hour prior to the morning milking
• 25% was offered after the morning milking

Comprehensive data was collected over the course of the trial for both groups of cows including:

• Milk quality testing: Checking fat and protein concentrations (g/kg) and somatic cell counts (SCC).

• Grazing and rumination behaviour: Continuous monitoring by Halter devices, including recording how much time cows spent grazing and ruminating.

• Rumen testing: Indwelling rumen boluses were deployed in 5 cows per group (~8% of cows) to monitor the rumen environment. The boluses logged pH and temperature every 10 min for approximately 120 continuous days.

• Live weight and body condition score (BCS): Cow live weight and BCS was measured twice daily as animals exit the milking parlour using DeLaval automatic in race walk-over scales (AWS100) and body condition scoring systems. The BCS system takes a continuous video of cows as they pass under a mounted camera which is used to create a 3D image.

• Pasture composition and utilisation: Pasture samples were collected before grazing each paddock for compositional analysis. This will used as a post-hoc assessment of the energy delivered to cows in each treatment.