Food selection and preference in grazing cattle

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Pasturing is the most natural and welfare friendly way to feed dairy animals, and is a requirement in organic dairying. Products labelled as “grass-fed” are making an appearance in grocery stores, reflecting a growing demand from consumers conscious about the health benefits of milk from pastured cows, or concerned about animal welfare. Achieving high levels of animal performance and health from grazed forage is a key objective within most pasture-based, milk production systems. Over the last five years, supported by my NSERC Discovery Grant, I studied dairy cows and heifers in pasture-based production systems, with the intent of improving their welfare and efficiency, through better productivity and health. We investigated how grazing behaviour developed in young heifers, looking at the effect of age of introduction to pasture and studying the role of their social environment. We also investigated the effect of gastrointestinal parasites on animal preference for certain types of forages rich in beneficial tannins. The long-term objective of this research program is to advance our understanding of feeding preference and grazing behaviour of heifers and cows in a pasture-based production system. This long-term objective will be achieved through a series of short-term objectives, which aim to determine how feeding preferences and grazing behaviour 1) are related to animal health and productivity; 2) are influenced by forage characteristics; 3) can be modified by early experience and learning. In a first experiment, we will relate individual differences in grazing behaviour and herbage intake with health and productivity. In a second experiment, we will investigate whether the preference for high-tannin forages in response to infection with gastrointestinal nematodes is innate, or acquired following positive post-ingestive consequence. In a third experiment, we will explore voluntary intake and preference of dairy heifers for forages with potential nutraceutical properties, varying in their condensed tannin content. In a fourth experiment, we will investigate the effects of forage condensed tannin levels on cow preference, independently of other characteristics and chemical components, such as fibre, which has been shown to negatively affect preference. A fifth experiment will aim to confirm the existence of a sensitive period for the development of grazing behaviour and efficiency in heifers. Our last experiment will expose young animals to fresh plant species at various stages of development in an attempt to detect a sensitive period for learning plant characteristics. Providing cows with access to pasture is a privileged way to improve animal welfare and the image of the dairy industry. However, maintaining cow productivity and health in a more extensive pasture-based system necessitates an efficient use of forage resources, through an improved knowledge of feeding behaviour and dietary choices, and the development of effective solutions.