Forage selection of dairy cows grazing contrasting multispecies swards is influenced by cow characteristics

Artificial pastures for dairy cows often comprise a small number of plant species, which limits the animals' opportunity for forage selection. Despite being a natural behaviour observed in many ruminants, little is known about the factors influencing forage selection in domestic cattle. In this study, a herd of dairy cows was observed grazing on an experimental pasture, which was composed of four distinct swards of different botanical and chemical composition. The cows' forage choices were recorded and it was tested whether there were statistical associations with cow characteristics, such as age, lactation status, days in milk (DIM), body condition score (BCS) or somatic cell count (SCC). The results revealed that with increasing age, cows consumed forage lower in grasses (P = 0.001), but higher in legumes (P = 0.002) and species diversity (P = 0.009). Lactating cows consumed forage higher in legumes (P = 0.007) and total extractable phenols (TEP, P = 0.009) than dry cows. With increasing DIM, cows consumed forage lower in grasses (P = 0.001) and higher in legumes (P = 0.002), TEP (P = 0.023) and condensed tannins (P = 0.029). With increasing SCC levels, cows consumed forage with less grasses (P = 0.017), a higher proportion of medicinal herbs (P = 0.030) and higher species diversity (P = 0.012). There were no associations between pasture choices and BCS. The results indicate that dairy cows show complex forage selection based on their physiology, age and health status. Giving cows the opportunity to select from a diverse array of pasture plants may increase their performance, health and wellbeing.