SR9200 -Timing of herbage allocation in a strip grazing organic system: Effects on grazing pattern, performance and health of lactating dairy cows and on milk quality.

The Ministry funded this project through the New Directions Research Program in 2008.

Lead researcher

Dr Gaston Raggio, Organic Dairy Research Centre, University of Guelph - Campus d'Alfred

Objectives

The objective of this work is to assess the effect of grazing management, more specifically AM or PM strip grazing allocation of pasture, on:

• botanical & chemical composition of herbage
• daily grazing pattern
• dry matter intake
• cow liveweight change
• cow health
• milk production
• milk composition

Expected Benefits

• Through the development of simple pasture management strategies to better match the diurnal variation in forage quality with animal nutritional requirements, this project will reduce organic milk production cost, environmental impact, improve animal health and milk composition.

Results

This project contributes to a larger research program which seeks to provide simple tools that Ontario farmers can use to produce forages with better energy to protein balances. Farmers could achieve these forage improvements by better managing their existing resources.

Plant - animal interactions were studied using an integrated, multidisciplinary approach. By offering grazing dairy cows a new strip of pasture in the PM as compared to the AM, provided herbage with higher total non-structural carbohydrates (TNC) content. This type of mixed pastures, however, when offered with a partial Total Mixed Ration [TMR] (partial TMR 50 % of Total Dry Matter Intake)., had no impact on DMI, milk yield, composition, N balance, and had a minimum or negative impact on body weight gain.

Grazing behaviour was not affected by allocating the new pasture strip in the PM, as opposed to AM, but offering a fresh strip of pasture either after AM or PM milking increased dairy cows bite rate and the percentage of time grazing. The dry matter intake (DMI) from pasture in the PM treatment was negatively affected by environmental conditions and diurnal changes in herbage chemical composition.

Even though herbage offered to the PM treatment cows contained 2.5% more TNC, DMI from pasture was not improved. The high ambient temperature during the grazing period, reduced day length, and a slight increase in the nutrient detergent fibre concentration of herbage in the PM treatment appeared to have offset the positive impact of higher herbage TNC on DMI and weight gain. In August and early September, when day length decreases, PM allocation becomes unfavourable since it reduces pasture dry matter and nitrogen intake due to reduced grazing activities.

Related information

• Other projects funded through the New Directions Research Program in 2008
• New Directions Research Program