Rethinking environmental enrichment for dairy calves: improvements for basic biological needs?

An appropriate rearing environment for calves in dairy farms is essential for their healthy development and welfare. However, in the dairy industry, calf environments are often barren and lack sufficient stimulation. Environmental enrichment is commonly defined as modifications to animal environments that improve biological functioning, yet many so-called enrichment practices for calves are responses to basic needs rather than environmental improvements. This study aimed to critically discuss the environmental enrichment approach versus the fulfillment of basic needs, advocating that essential provisions for natural behaviors should be viewed as fundamental requirements rather than enrichment. Natural behaviors, such as social interaction, suckling, and grazing, are behaviors that calves are highly motivated to perform. When deprived of the opportunity to express these behaviors, calves may develop abnormal behaviors like non-nutritive sucking. Offering milk through teats is often considered nutritional enrichment compared to systems that conventionally offer milk through buckets. For instance, when milk is not offered through teats, calves may engage more frequently in compensatory non-nutritive sucking, such as sucking on pen structures or cross-sucking (when pair- or group-housed). Similarly, restricted access to grazing can lead to oral stereotypies like tongue rolling. Given that cattle are gregarious animals, social isolation is unthinkable and has been shown to negatively impact their welfare. Environmental enrichment should go beyond satisfying these basic needs, providing additional environmental stimuli to enhance exploration and well-being for calves whose basic biological needs are already met. This distinction underscores that meeting the full spectrum of natural behaviors is crucial, and only after addressing these needs should further enrichment strategies be implemented to promote optimal welfare in dairy calves.