Memory and food intake in sheep: Effects of previous exposure to straw on intake and behaviour later in life

Abstract

The ban on open-air burning of agricultural by-products by the European Union created disposal problems on many farms. Success was limited in attempts at feeding agricultural by-products like cereal straws to previously grazed livestock. This initial reluctance to accept unfamiliar feeds was also reported when livestock were fed whole-grain cereals in drought, or when grazed on new pastures and shrubs. It is suggested that previous exposure to feed might speed up the rate at which it is accepted, particularly if such experiences take place at pre-weaning. This study aimed at establishing the veracity of this assertion, and whether an early learning experience is carried over into adulthood. Two feeding trails were carried out with lambs not exposed (NE) to straw and those given access to straw at 12 weeks of age for either 10 (E-10) or 28 (E-28) days. At 24 weeks (Experiment 1), 10 lambs from each of the three treatment groups were tested, over 21 days, on their readiness to accept straw as feed. At 36 weeks (Experiment 2), another batch of lambs (from the E-28 and NE groups only) were similarly tested. For each, the lambs were penned individually (in view of lambs from their own treatment group) and also offered a concentrate supplement to meet daily nutrient requirements. In both experiments, intake of straw OM, N and DOM, as well as leaf to stem ratio in reject straw, were assessed for each penned lamb. Animal behaviour pattern was monitored once every 5 min, over an 8-h period, immediately after first confinement. Frequency of eating, idling, ruminating, or drinking were all found to be significantly greater (P<0.001) for previously exposed lambs. Intakes of OM, N, DOM, and leaf fraction in straw were also significantly greater (P<0.01) over the 1st week of assessment. However, the differences (P>0.05) between lambs exposed for 10 or 28 days were not significant in all the parameters measured. Results from these trials support the belief that animals exposed to feeds, pre-weaning, recognize such feeds and accept them later in life more readily than those given such feeds for the first time. The study implies that production systems that expose animals to a wide range of feeds early in life may be advantageous to them later. Research protocols may need to look more into the feeding history of experimental animals, particularly those assembled from different backgrounds. It may also be possible to exploit this observed behavioural pattern to “prepare animals” early in life to either accept or reject particular feeds they may meet later in life