R.A. Champion

Diurnal patterns of intake rate by sheep grazing monocultures of ryegrass or white clover

The effects of time of day on the ingestive behaviour of groups of five sheep (Ovis aries L.), grazing monocultures of ryegrass (Lolium perenne cultivar ‘Parcour’) or white clover (Trifolium repens cultivar ‘Kent Wild White’), were measured over periods of 1 h starting at 07:30, 11:30, 15:30 and 19:30 h in August. Grazing behaviour was monitored with an automatic recording system and intake rate was measured by weighing animals before and after grazing. Over the day, for grass and clover respectively, prehension biting rates decreased linearly from 85 to 68 and from 62 to 57 ± 7.4 (SED) bites min−1 and masticating rate increased from 71 to 90 and from 78 to 91 ± 5.6 (SED) chews min−1. Total jaw movements remained constant over the day but were greater on grass than clover (P < 0.01) at 155 and 145 ± 3.4 (SED) jaw movements min−1. Bite masses also increased linearly from 30 to 51 for grass and from 56 to 107 for clover ± 15.2 (SED) mg dry matter (DM) per bite and differences between grass and clover were significant (P < 0.001). Intake rates were significantly lower for grass than for clover (2.8 vs. 4.5 ± 0.18 (SED) g DM min−1; P < 0.001). There was an interaction between time of day and herbage species with intake rate increasing over the day from 2.5 to 3.2 and from 3.5 to 5.5 ± 0.67 (SED) g DM min−1 for grass and clover respectively. These changes in ingestive behaviour were associated with diurnal changes in the chemical composition of the two herbages. Herbage DM percentage increased from 07:30 to 19:30 h to a greater extent on grass (15–24%) than clover (12–18%, P < 0.001). WSC increased linearly from 15.6 to 18.3% for grass and from 5.4 to 7.3% of DM for clover (P < 0.05). Starch content of the herbage also increased linearly from 3.0 to 4.1% for grass and 3.6–8.7% of DM for clover.

Intake and behaviour responses by sheep, in different physiological states, when grazing monocultures of grass or white clover

Abstract Monocultures of ryegrass (G; Lolium perenne cultivar ‘S23’) and white clover (C; Trifolium repens cultivar ‘Huia’) were maintained at sward surface heights (SSH) of 3 or 6 cm by continuous variable stocking with core groups of sheep ( Ovis aries L.) in different physiological states (physiology). Each group comprised four lactating ewes (L), and their twin lambs, plus two non-lactating, non-pregnant ewes (D). There were two plots each of G6 and C6 plus one plot each of G3 and C3. Each plot was 0.33 ha and was irrigated to maintain soil moisture deficit at −1 . The experiment ran from May to October. All lambs were weaned at 15 weeks of age on 8 August and removed from the experiment. Prior to weaning (spring/summer) measurements of ingestive behaviour were made on five occasions, using an automatic system to record jaw movements and by weighing animals before and after a 1 h period of grazing, to estimate herbage intake rate. One measurement of ingestive behaviour was made after weaning (autumn) on previously-lactating ewes and D ewes. Effects of physiology and herbage species on grazing behaviour were compared by regressing mean values for the groups of ewes on SSH. Generally ewes had higher intake rates of clover than grass and CL ewes had greater daily DM intakes than GL ewes (+ 0.56 kg). This gave rise to higher lamb growth rates (366, 312, 284 and 252 g day −1 , for treatments CL6, GL6, CL3 and GL3, respectively). It is suggested that sheep can eat clover faster than grass because less time is required to prehend and masticate a bite of a given mass (handling time) for clover than grass. However, ewes markedly altered their grazing time in relation to their physiological state and intake rate of herbage, and thus relationships between sward state and bite mass and intake rate, cannot be used to predict daily intake without an understanding of factors that control grazing time.

An automatic system to monitor lying, standing and walking behaviour of grazing animals

Abstract Sensors incorporating mercury tilt switches were used to measure lying, standing and walking behaviour of grazing cattle and sheep. The lying/standing sensor was suspended below the animal, whilst the walking sensor was fitted to the shin of the animals foreleg. Both switches gave a digital-low output when vertical or near vertical and a digital-high output when more than 45° from vertical. The lying/standing sensor was operated when the animal lay down and the walking sensor was operated by leg movement, and also by the animal lying down. The sensor outputs were connected to digital recorders mounted on the animals. Sheep fitted with lying/standing recording equipment were observed every 5 min during daylight over 24 h. The index of concordance between the automatic and manual observations of lying/standing was 0.953. Cattle and sheep, fitted with equipment to record walking, were filmed by video camera for at least 10 min each. The number of steps counted by observers of the video recordings were compared with results from the automatic system. Mean square prediction error (MSPE) analysis of the automatic-system results showed they had an error of 7.7% for both cattle and sheep. This error was a percentage of the mean of the actual observed results. Cattle fitted with equipment to record lying/standing and walking were observed every 10 min during daylight over 24 h. The concordance between automatic and manual observations of lying/standing was 0.990 using the lying/standing sensor and 0.996 using the walking sensor. The presence or absence of walking behaviour was also noted and the concordance for the automatic system results with this was 0.96. The automatic system described provides a reliable means of recording lying, standing and walking behaviour of cattle and sheep over 24 h periods.