The relationship between social behaviour, feeding behaviour and stress in lambs in intensive finishing systems

© 2016 Maxine RiceThe production of lamb meat is a large and important agricultural industry in Australia. Variability and seasonality of the climate and the demand for a consistent product (in terms of weight and age) have led to an increase in the use of feedlot systems for finishing lambs. An estimated 5-20% of lambs in feedlots are prone to ‘shy-feeding’ or inappetance. Factors considered to contribute to the condition of shy-feeding include: neophobia (environment and concentrated feeds), acidosis and competition around feeding; however, little is known about the individual characteristics of these animals. The aim of this thesis was to examine the relationships between social behaviour, feeding behaviour and stress in lambs in intensive finishing systems. A preliminary study examined relationships between temperament, feeding behaviour, social interactions and cortisol concentrations in lambs in the first 2 weeks in an intensive finishing system (feedlot). Lambs in two 20-lamb feedlots (with 2 m2 floor space/animal) were studied. Prior to entry to the feedlot the lambs were subjected to a temperament test (Isolation Box Test) in which activity was measured. Weight gain, general activity, lying time, time at the feeder, number of feeding bouts, displacement at the feeder and plasma cortisol concentrations in weeks 1 and 2 in the feedlot were recorded. A parsimonious general linear model was developed to relate the logarithm of cortisol concentration to all other measurements. Cortisol was most elevated if the lamb’s activity in the feedlot (number of steps) was low (P=0.000025) and also for those lambs that fed more frequently (P=0.0010). Higher levels of activity in the temperament test were associated with higher cortisol concentrations in week 1 when the lamb was not displaced from the feeder. However there was an interaction with the number of displacements (P=0.0016), leading to little effect when a displacement occurred. A linear model could not be fitted for cortisol in week 2. A second study investigated some individual characteristics associated with shy-feeding. Forty lambs in a feedlot pen were studied in 3 cohorts (120 lambs total) over 16 months. This study focused on the behaviour of lambs in the first week in the feedlot. Lambs were provided with 2 m2 floor space per animal and 4 cm trough length each. Temperament and weights were recorded before entry to the feedlot and weights were recorded again at the end of the first week. Based on total time spent feeding over a 24-h period in week 1, lambs were categorized into two distinct groups: “Shy-feeders” (1 hour feeding, n=98). Accumulated analysis of variance was used to compare entry weights, temperament, growth (live weight change), and feeding behaviour of each group. Most of the Shy-feeders lost weight in the first week whilst most of the Feeders gained weight, however within each grouping there was no relationship between growth and time at the feed trough despite time at the feed trough varying from 1 to 5 h for Feeders. Shy-feeders were displaced less from the feed trough by other lambs than Feeders (P0.50). This thesis demonstrates that relationships exist between temperament, behaviour and stress in lambs early in the feedlot. Shy-feeders could clearly be classified by the time spent feeding over a 24-h period in week 1, although measures of temperament and entry live weight were not related to the condition of shy-feeding. A better understanding of these behavioural and stress relationships early in the feedlot may identify strategies to assist vulnerable animals to adapt to feedlots