When calves refuse to eat: a question of behaviour or feed?

In livestock farming, there are many difficulties with ingestion, despite the efforts of manufacturers. This is linked to a phenomenon that has been clearly identified by scientists, but little reported on the ground: neophobia, in other words, reluctance towards an unrecognised feed. This physiological phenomenon is unavoidable and always disappears in the end.

Feed inappetence or neophobia: protection from an unusual feed?

It is very complex to predict the palatability of a feed for ruminants, and even more so for calves. We now know that calves dislike bitter and astringent tastes, as they are poison markers. Calves are particularly sensitive to sweet tastes, and manufacturers of calf products include this element.
Despite efforts to get a good combination of tastes on paper, frequent tests, a choice of sweet raw materials and farm trials to select a specific solution, consumption “accidents” do happen. The phenomenon of neophobia may disrupt the introduction of a new feed.
Neophobia is defined as the avoidance and reluctance to taste unfamiliar feed (Cooke et al., 2006). This phenomenon is well known among ruminants (Chapple and Lynch, 1986). It is the result of a physiological phenomenon in which the animal protects itself to avoid toxic feed and feed that is too rich in some nutrients.

What are the recommendations for dealing with feed neophobia in calves?

Gentle dietary transitions

It is best to introduce the new feed in progressive ratios into the calf’s diet.

Give the calf time to get accustomed to the new feed

When offered a new feed, ruminants test it by initially ingesting only small quantities (Chapple and Lynch, 1986; Chapple et al., 1987; Thorhallsdottir et al., 1987).
Each day, the calf’s consumption of the new feed increases. In Figure 1 (Launchbaugh, 1995), consumption of the new feed reaches the normal level of 20 g/d from day 6 onwards.
Squibb et al (1990) consider that neophobia, not to be mistaken for inappetence, is the main cause of lack of consumption of solid feed by inexperienced animals. While some feed are initially more accepted than others, there is no feed that is instantly acceptable to all ruminants, except perhaps the mother’s milk (Launchbaugh, 1995; Figure 1).

Farms with individual pens require more attention

Calves are influenced by the behaviour of their fellow calves. Social learning allows the inexperienced animal to avoid the risk of testing each new feed (Galef and Laland, 2005; Nicol, 2006). Costa et al (2014) presented two trials in which they offered a new feed for 30 minutes on 3 consecutive days. One group consisted of calves reared in individual pens from birth to weaning and the other of calves inserted from birth into a group of other calves and cows.
In the first trial, the cales in collective pens consumed twice as much feed as the calves in individual pens (Figure 2). In the second trial, the group in the collective pen consumed 4 times more feed than the group in the individual pens.

In this second trial, some calves even refused to touch the feed.
Similarly, the calves in the collective pen were quicker to taste the new feed than the calves in the individual pen: 1 min 23 s compared with 3 min 58 s for trial 1 and 3 min 09 s compared with 6 min 38 s for trial 2.