How cattle discriminate between green and dead forages accessible by head and neck movements by means of senses: reliance on vision varies with the distance to the forages.

Abstract

The ability of ungulates to discriminate among vegetation patches depends largely on the senses of vision, olfaction, tactility, and gustation. However, little is known about how ungulates rely on the respective senses in response to varying distances to discrimination targets. This study aimed to assess how cattle discriminate between patches of green and dead forages by means of senses, with a particular attention to the role of vision in relation to the distance to the forages. Thirteen Japanese Black cows were allowed to choose between the two forages from a distance of about 1m without (- BF) or with (+ BF) a blindfold. The green forage differed from the dead forage in color, texture, odor, quality, and animals' preference. Cows located and ate the green forage as the first choice (Type 1), or as the second choice after touching (Type 2) or further biting (Type 3) the dead forage in error. Overall, the proportion of [Type 1]/[Types 1 + 2 + 3] was above the chance for both - BF and + BF with a decrease by blindfolding. The proportion of [Type 2]/[Types 2 + 3] was above the chance for both - BF and + BF with no effect of blindfolding. The results indicate that cattle discriminating green forage against dead forage rely greatly on vision and to a lesser degree on olfaction when away from the forages, but rely no longer on vision and at least on tactility on the muzzle or in the mouth when in contact with a wrong choice.