G.W. Arnold

Behaviour of the ewe and lamb at lambing and its relationship to lamb mortality

Abstract A number of behavioural traits associated with the maternal instinct of sheep were studied under paddock conditions over a range of breeds, age, climate, nutrition and locations in five lambings in south Western and north Western Australia. There was very considerable variation between ewes in any group in the occurrence and timing of each trait. There were few differences due to breed, age of ewe, nutrition, climate or location in the behaviour of the ewe before and during parturition. Nearly all the differences that occurred were in the frequency of pawing the ground before and during labour. Fewer Southdowns and Merinos pawed the ground than ewes of other breeds. Also this trait occurred more in summer than in winter in south Western Australia, and less here than in north Western Australia. The behaviour of the ewe during the post partum period was highly predictable. She normally stood and commenced cleaning within 1 min of birth. Cleaning commenced at the head and progressed down the body. Desertions and other forms of aberrant behaviour were uncommon. There were no biologically significant differences in length of labour, time from birth to stand and time from stand to first drink due to breed, age, pre-lambing nutrition, climatic conditions or location. Second-born twins were delivered after a significantly shorter labour than first-born twins. In one series of observations twins took longer to drink than singles. Type of birth did not influence the time taken for the lamb to stand. Rectal temperature three hours after birth dropped significantly when rainfall exceeded 2 mm during the 3 h. Lamb mortality increased significantly in wet weather in winter and most lambs which died more than 3 h after birth had a depressed rectal temperature at 3 h. The ewes of lambs which died after standing tended to have longer than average labour. Poor maternal behaviour per se was the cause of 16% of lamb deaths and failure of the lamb to drink after standing caused 23% of lamb deaths in winter in south Western Australia. In summer in both environments heat stress was the primary cause of lamb deaths.

Effects of nutritional experience in early and adult life on the performance and dietary habits of sheep

Abstract In a series of four experiments, comparisons were made of the grazing preferences, food intake, live weight and wool production of sheep having experience of several contrasting nutritional environments. The environments ranged from semi-arid plant communities and sown pastures to hay fed in pens. The sheep were compared on sown pastures at Canberra, A.C.T., and at Bakers Hill, Western Australia. What appeared to be only small differences in experience resulted in marked differences in grazing preferences, which persisted for more than a year, despite attempts to remove them. Experience in different environments was also reflected in food intake. The differences in organic matter intake per kilogramme live weight were generally not as distinctive as differences in preferences. Seasonal patterns of live weight were significantly different in all experiments for sheep with different experience, and smaller differences were observed in wool production. An effect of previous nutritional experience of ewes on lamb birth weight and growth rates was evident. In general, sheep moved from pastoral areas to sown pastures took longer to adapt than did sheep moved from one type of sown pasture to another or from sown pastures to pastoral areas. Adult sheep took longer to adjust to a new environment than did lambs. Only in one experiment did there appear to be persistent effects of previous experience on production.

Some factors envolved in natural weaning processes in sheep

Abstract Two studies were done to define the factors influencing the time of natural weaning in sheep. The milk production of ewes was measured during four-hour periods each week at varying stages of lactation. Lambs were separated from the ewes during this period before being reunited and the behavioural responses of each to the other were recorded. The responses were classed according to an arbitrary system defined to gauge the current strength of ewe-lamb attachments. In the first study, measurements were made on Merino and Dorset Horn sheep. Whilst milk yield declined continuously during lactation, the nature of ewe-lamb bonds did not. They remained constant up to about 100 days after birth. Thereafter, the attachments weakened rapidly, with some differences between the two breeds. In the second study, Merino ewes on a high plane of nutrition had a higher milk yield throughout lactation than ewes on a low plane of nutrition. The ewe-lamb bond remained unchanged for 130 days in the high plane group but changed substantially in the low plane group. It is concluded that milk yield in the ewe is a major determinant of the strength of the ewe-lamb bond, with a threshold level below which weaning occurs.

The roles of sight and hearing in the lamb in the location and discrimination between ewes

Abstract The ability of Merino lambs to find and discriminate their dams when separated by 6–10 m and having the choice of three ewes was examined over the first 4 weeks of life. In the first experiment the techniques were validated and comparisons made between normal lambs and lambs deprived of visual or auditory cues. The proportions of lambs recognizing their dams in 2 min were increased over the first week of life and were similar in all groups. There were no further changes with age up to 4 weeks; values in this period were 0.78, 0.64 and 0.44 respectively for normal lambs and lambs deprived of visual and auditory cues. Similar results were obtained in the second experiment. Normal lambs had to be 8 days old before a high proportion (0.90) could find and recognize their dams in 2 min. The effects of depriving the lambs of visual cues decreased in the second week of life whereas the effects of depriving the lambs of auditory cues increased in the second week of life. When both visual and auditory cues were absent no more than 10% of lambs found their dams. When deprived of auditory cues most lambs actively sought their dams but failed to recognize them, whereas when deprived of visual cues a proportion of lambs failed to seek their dams at all and those that did were slower to start doing so.

Ethogram of agonistic behaviour for thoroughbred horses

Abstract Social interactions between individual horses were observed in two herds each comprising a stallion and a number of mares. In one herd, the animals were observed whilst grazing and resting; in the other, nearest neighbours were recorded when the animals were grazing, and social interactions were noted when the animals were feeding on hay. In both herds, the horses showed marked preferences for the company of specific individuals when they were grazing. In one herd, the associations were mainly between individuals that had been associated prior to being put in the herd. In the other herd, this was not the case. A new statistic was produced for testing for specific company preference. In both herds, the stallion was dominant over all mares and never received any aggression. The complete social hierarchy could not be determined for the herd which was observed only when grazing because social contact was restricted to that within groups or pairs that associated together. In the herd to which hay was fed, a non-linear hierarchy existed. Statistics were produced to quantify both the general level of dominance of a horse and its specific dominance or subordination to every other horse. It is suggested that these statistics, and one for quantifying the general aggressiveness of a horse, could be widely used. A principal component analysis allowed the horses to be characterised socially according to aggressiveness, their attitude to other horses and their attractiveness to other horses.

Associations between individuals and home-range behaviour in natural flocks of three breeds of domestic sheep

Abstract The associations formed between individual sheep in natural flocks of Dorset Horn, Merino and Southdown sheep were studied. In these flocks, the sexes were not separated and little culling was carried out; breeding occurred naturally. The locations of individuals were mapped when the sheep were grazing and when they were camped. The breeds differed in their tendency to disperse. Merinos rarely formed sub-groups, Southdowns usually formed a few sub-groups and Dorset Horns always formed many sub-groups. All Dorset Horn and Merino sheep of both sexes formed associations with other sheep at some time. Associations, which varied in frequency, were relatively short-lived, being present for one three-week study-period but not often being present three months later. When an association involved two sheep, the animals were relatives only on 22% of occasions, but in larger associations, two or more related animals were present in 50% of Dorset Horn and 36% of Merino associations. The association in Merinos meant that animals grazed close to one another in the flock since no sub-groups were formed. Single linkage cluster analysis, principal coordinate analysis and the technique of Grassia (1978) were used to compare the general propensity of Southdown and Dorset Horn sheep to form associations. The Southdowns formed very close associations when grazing but not when camping, whereas the Dorset Horns formed less close associations but did so during both grazing and camping. In both breeds, the associations were mostly between sheep of similar age and sex, with males > 2 years old forming the strongest associations and keeping apart from the older females; these females also tended to associate together. When the Dorset Horns were grazing, the associations between individuals were within “feeding” home ranges. In the Southdowns, the individuals associating together used widely dispersed areas of the paddock, rather than one general area. Merinos dispersed into sub-groups only under extreme food shortage and then the sex and age groups segregated as in the other two breeds. Thus, there appears to be a wide variation between these breeds of sheep in their social organisation.

Factors influencing the grazing behaviour of sheep in a Mediterranean climate

Abstract The diurnal pattern of grazing of sheep was studied in summer in 2 Mediterranean environments in 3 experiments. In the first experiment with Border Leicester × Merino sheep, it was found that in a given day the times of beginning and ending the major morning and afternoon grazing periods and the time spent grazing, were influenced by time of dawn or dusk, temperature, humidity and the time spent grazing the previous night. The temperature was found to influence the timing of events throughout the day but humidity mainly had an effect in the midday and afternoon. Six breeds of sheep were compared in a second experiment (Romney, Dorset Horn, Cheviot, Suffolk, Southdown and Border Leicester). There were significant differences between the breeds in the diurnal pattern of grazing, in grazing times and in responses to environmental conditions. The Cheviots and Suffolks differed from the other breeds because they began earlier in both the morning and afternoon. The Suffolks grazed for longer in all the grazing periods and differed significantly in grazing time from sheep of all other breeds. In a third experiment, sheep reared in a dry tropical environment (Abydos) behaved differently over 3 summers to sheep raised in a Mediterranean environment with dry summers (Bakers Hill). The main differences were in response to temperature and humidities in the morning and to length of day in the afternoon. The differences diminished with time. Generally, afternoon (pm) activity was more influenced by immediate grazing activity (night grazing time and morning (am) grazing time) than was the morning behaviour, but there were exceptions.

An analysis of spatial leadership in a small field in a small flock of sheep

Abstract The individuals in a flock of 12, 9-month-old Dorset Horn X Border Leicester X Merino sheep could be characterized according to the amount of independence they showed in terms of time spent “alone”. The frequency with which a sheep was first of a group to enter the paddock to graze was positively correlated with its initiation or “leadership” of activities in the paddock. There was a significant correlation between “leadership” in pair tests and in groups of six. The time spent alone by individuals in a group of six was positively correlated with a “leader”/follower ratio and negatively correlated with frequency of joining other sheep when grazing. The larger the leader/follower ratio, the less time a sheep spent with others when grazing in a group of 12. The observations suggest that “leadership” in activities is not a positive expression but a consequence of independence and being followed by other individuals.

Social interactions amongst beef cows when competing for food

Abstract Social interactions between 12 North Devon cows were recorded when competing for hay distributed in 4 heaps 15 m apart. Following threats or butts, or without any apparent aggression, cows frequently left one heap and joined another group, or found a vacant heap. The diallel analysis of Grassia, and principal component analysis were used to determine the social characteristics, or profiles, of each individual, and the strength of its contacts with each other individual. These analyses showed that dominance and aggressiveness were separate characteristics and that individuals could be characterised also for activeness and social altitude to other cows. Aggressive acts were not unidirectional, and for only 11 pairings of the cows (out of a possible 66) were there statistically significant dominance rankings. However, the diallel analysis allowed 6 of the 12 cows to be separated on their general dominance rank. Spearman rank correlations between more traditional estimates of dominance rank and that from the diallel analysis were statistically highly significant. The advantage of the diallel analysis is that each animal can be quantitatively compared with each other animal. This, coupled with the principal component analyses, allowed a detailed analysis of the pattern of social interactions in a competitive situation, and the role played by each individual cow.

A NOTE ON CHANGES IN INGESTIVE BEHAVIOUR OF SHEEP FOLLOWING SHEARING

Abstract The grazing behaviour and herbage intake of sheep grazing at four stocking rates were recorded before and after shearing in winter in Southern Australia. Following shearing, grazing time was reduced but intake of organic matter per hour increased at all stocking rates even though the amount of feed available was very low at the highest stocking rate. Energy balance was maintained at the three lowest stocking rates. At the highest stocking rate, the sheep were in poor condition and spent more time sheltering; time spent grazing was greatly reduced, energy balance was not maintained and 40% of the sheep died.