Samantha Bickell

Australian perennial shrub species add value to the feed base of grazing livestock in low- to medium-rainfall zones

Australian native perennial shrubs that are adapted to drought and infertile soils contribute nutrients to grazing systems that would otherwise support limited ruminant productivity. In this study, we report the nutritive value of 39 Australian shrub species of the genera Atriplex, Rhagodia, Maireana, Chenopodium, Enchylaena, Acacia, Eremophila, and Kennedia. Edible foliage was sampled in winter and summer, and there was little difference in nutritive value between seasons. The in vitro organic matter digestibility of most shrub species was 40–70%. Most species contained medium to high levels of crude protein (12–22% of dry matter, DM) and high concentrations of sulfur (2–8 g/kg DM). In an 8-week grazing experiment in which Merino wethers grazed a ‘shrub system’ containing four shrub species and a sown inter-row of annual pasture, the sheep gained weight during autumn without supplementary feeding. By comparison, sheep fed senesced volunteer pasture and supplementary cereal grain only maintained weight. The forage shrubs provided up to 50% of the total DM intake of sheep grazing the ‘shrub system’ and made a modest contribution to the digestible energy intake of the animals and a large contribution to their crude protein and mineral intake. Considering the timely and predictable provision of limiting nutrients and benefits such as gut health and the provision of shade and shelter, we suggest that Australian shrub species can make a valuable addition to the feed base of low- to medium-rainfall zones in southern Australia.

Feed intake of sheep when allowed ad libitum access to feed in methane respiration chambers

The patterns of feed intake when animals are allowed ad libitum access to feed in a respiration chamber is not known, nor are the potential effects of the artificial environment of chambers on voluntary feed intake. The objectives of the study were to describe the pattern of hourly feed intake of sheep when fed for ad libitum intake in respiration chambers and determine the repeatability of this pattern and the correlation between feed intake and methane production calculated at hourly intervals. Daily and hourly measurements of methane production and feed intake of 47 Merino wethers were measured in respiration chambers twice, 4 wk apart. We found that hourly feed intake of sheep with ad libitum access to feed in respiration chambers showed a repeatable pattern over the 2 measurement periods (r = 0.89, P < 0.001). During both measurements, sheep ate continuously throughout the 23 h period, but most of the eating occurred during the first 8 h in the respiration chambers. There was a significant linear correlation (r = 0.22) between hourly feed intake and hourly methane production (P < 0.001). An unexpected result from this study was that despite using an accepted and published acclimatization procedure to habituate the animals to the respiration chambers, sheep had 15 to 25% lower feed intake in the respiration chambers compared with their feed intake during the previous week in the animal house pens. In addition, daily feed intake in the respiration chamber was not correlated with feed intake in any of the 7 d before entering the chamber (P > 0.05). Future methane research may consider using feed intake and changes in intake levels as a quantitative indicator of habituation to the methane measurement procedure and environment, which, given the tight association between feed intake and methane production, will be crucial in providing accurate values for methane production.

Temperament does not affect the overall establishment of mutual preference between the mother and her young in sheep measured in a choice test

Temperament influences maternal behavior and lamb survival in Merino sheep selected for calm or nervous temperament. The impact of this selection on mother-young recognition and early expression of temperament in lambs is unknown. We tested the ability of multiparous ewes selected for calm (n = 16) or nervous (n = 18) temperament to recognize their own lambs 6 hr after parturition, the ability of the lambs to display a preference for their own mother at 18 hr, and the temperament of the lambs at 1 and 16 weeks of age. Ewes and lambs from both genotypes showed a similar preference for their familiar kin. In contrast, differences in temperament were detectable at 1 and 16 weeks of age. Nervous lambs showed higher vocal and locomotor activity than calm lambs. Thus, temperament did not affect the early process of ewe-lamb bonding but might affect the quality of the mother-young relationship under more challenging situations.

Maternal behaviour at parturition in outdoor conditions differs only moderately between single-bearing ewes selected for their calm or nervous temperament

Maternal and lamb behaviours play a major role in lamb survival and there is evidence that selection for calm temperament may help improve lamb survival by improving maternal behaviour. However, the apparent better maternal behaviour of calm ewes might be due partly to their lower reactivity to the presence of the human observer rather than to better maternal behaviour per se. The extent to which the selection for temperament influenced the behaviour of the ewe and lamb after parturition with minimal human disturbance was investigated in the present work. Single-bearing multiparous and primiparous ewes were observed to determine any interactions of temperament with maternal experience on ewe and lamb behaviours. Postpartum ewe-lamb interactions under outdoor lambing conditions were captured by continuous video recordings by a remote controlled recording device for up to 2 h postpartum. Calm ewes licked their lambs more and tended to stay longer on the birth site. Nervous lambs stood up earlier and were quicker to start performing exploratory behaviour. However, duration of suckling during the observation period did not differ between the calm and nervous lambs. There were no effects of maternal experience on the behaviour of the lamb and there were no interactions between temperament and maternal experience on the behaviour of the ewe or lamb. Our study indicates that temperament does influence the early postpartum behaviour of ewes and lambs under extensive field conditions.

Temperament and reproductive biology: emotional reactivity and reproduction in sheep

Reproductive capacity is controlled by a large number of factors such as season, social interactions and metabolic status. However, the influence of emotional reactivity on reproductive success has not been intensively investigated in farm animals. In this review, we define emotion reactivity and the expression of its inter individual variability named temperament. We briefly describe our protocol to measure temperament in sheep and discuss the heritability of temperament traits. Using the results obtained from our flock of sheep selected for calm or nervous temperament, we illustrate how this selection affects the reproductive biology from changing the inexperienced ewes response to the male effect to improving lamb survival and ovulation rate. We conclude that the mechanisms by which selection for temperament affects the different steps of the reproductive cycle are not yet understood but nevertheless this type of selection could have a great impact on reproduction efficiency of sheep and other domestic ruminants.

Challenge by a novel object does not impair the capacity of ewes and lambs selected for a nervous temperament to display early preference for each other

Novelty, a powerful fear-inducing and stressful stimulus, could be detrimental on the capacity of ewes and lambs to recognise each other. The effect of a novel object on the ability of ewes and lambs, selected for their calm or nervous temperament, to show a preference for each other was tested in a two-choice discrimination test. Both calm and nervous temperament mothers showed a preference towards their own offspring rather than the alien lambs. Nervous temperament ewes also looked at their own lamb more than the alien. In contrast, nervous lambs showed a greater preference and took less time to reach their own mother than calm lambs. Nervous temperament does not seem to impair the capacity of ewes and lambs to display an early preference for each other, and might be an advantage in some challenging postnatal situations because of the increased motivation of nervous lambs to reunite with their mother.

Maternal behaviour and peripartum levels of oestradiol and progesterone show little difference in Merino ewes selected for calm or nervous temperament under indoor housing conditions.

Temperament influences the expression of maternal behaviour in sheep under experimental field conditions. We investigated whether maternal behaviour between ewes selected for a calm or nervous temperament is independent from environmental conditions. In addition, the level of maternal behaviour expressed by mothers is correlated with the concentration of hormones during the peripartum period. Therefore, we investigated whether the selection for temperament had resulted in hormonal differences between the two lines with regard to the hormones that could be involved in the onset of maternal behaviour. Oestradiol, progesterone and cortisol concentrations from 4 days before parturition to 24 h after parturition were determined from blood samples collected from 10 calm and 12 nervous ewes. Behavioural interactions between ewe and lamb were also recorded for 2 h starting at parturition. Mothers of both temperament lines showed adequate maternal behaviour under the controlled conditions of the study. Therefore, the results of the study do not suggest that selection for a calm or nervous temperament has profoundly affected the intrinsic ability of mothers to display adequate maternal behaviour. Hormonal differences between the two temperament lines were generally small and their possible influence on the display of maternal behaviour in the two temperament lines would have to be demonstrated.