Foraging preferences of dairy cows grazing on contrasted multispecies swards

Abstract

Selective foraging has been reported in many wild and domesticated ruminants, yet modern livestock production systems rarely allow animals to express this natural behaviour. However, it is assumed that giving livestock the opportunity for forage selection positively influences their health and welfare. This study investigated the forage selection of individual dairy cows on pasture. Over one grazing season, a herd of 23 dairy cows was observed grazing on an experimental pasture in Switzerland, which consisted of different plant mixtures. The cows had unrestricted access to all mixtures and their individual foraging behaviour was documented by scan sampling. The four mixtures were rich in grasses (G), grasses and legumes (L), grasses and tanniferous plants (T), and grasses and herbs containing essential oils (E). The results revealed a partial preference for the L mixture at herd level across all grazing rotations (P ≤ 0.001). All mixtures were frequented, indicating that the herd utilized the array of available plants. Individual preferences varied and not all cows followed the herd's average pattern. Individual preferences shifted throughout the grazing season, but the pattern of this variability differed between animals. The findings demonstrate that dairy cows actively select from different pasture plants and that preferences vary between individuals and over time. Importantly, average herd preferences do not accurately represent the behaviour of all cows. Individual preferences should be considered when aiming to meet the foraging needs of all herd members.

Keywords: Botanical biodiversity; Dietary choice; Feeding behaviour; Pasture; Plant secondary compound; Ruminant.

Fig. 1

Map of the experimental site. The pasture was split into two blocks of eight plots each. Each of the four botanical treatments was replicated twice per block. During each grazing rotation, cows had daily alternating access to each block, where they had free access to each of the eight plots.

Fig. 2

Proportions of scans individual cows were observed foraging in each of the plant mixtures. Each boxplot is based on the averages of all cows present on pasture during the respective rotation.

Fig. 3

Proportion of scans the cows were observed foraging in the four plant mixtures across all grazing rotations. Each plot represents one individual. The graph is based on the average proportions of observations per treatment and rotation per individual (n = 6). The red asterisk indicates the mean value and the bold line the median. E Essential oil, G Grass, L Legume, T Tannin.

Fig. 4

A-C. Selected examples of the foraging preferences of individual cows changing throughout the grazing season: Cow #9 (A), cow #13 (B) and cow #3 (C). The figures illustrate the proportions of scans each animal was observed foraging in each of the four plant mixtures during each grazing rotation (numbers 1 to 6). The graphs are based on the daily average proportions of observations per treatment and rotation per individual. The red asterisk indicates the mean value and the line the median. The whiskers of the boxplots illustrate the range of datapoints with each value depicted as a separate point. E Essential oil, G Grass, L Legume, T Tannin.