Frequent moving of grazing dairy cows to new paddocks increases the variability of milk fatty acid composition

The aim of this work was to investigate the variations of milk fatty acid (FA) composition because of changing paddocks in two different rotational grazing systems. A total of nine Holstein and nine Montbéliarde cows were divided into two equivalent groups according to milk yield, fat and protein contents and calving date, and were allocated to the following two grazing systems: a long duration (LD; 17 days) of paddock utilisation on a heterogeneous pasture and a medium duration (MD) of paddock utilisation (7 to 10 days) on a more intensively managed pasture. The MD cows were supplemented with 4 kg of concentrate/cow per day. Grazing selection was characterised through direct observations and simulated bites, collected at the beginning and at the end of the utilisation of two subsequent MD paddocks, and at the same dates for the LD system. Individual milks were sampled the first 3 days and the last 2 days of grazing on each MD paddock, and simultaneously also for the LD system. Changes in milk FA composition at the beginning of each paddock utilisation were highly affected by the herbage characteristics. Abrupt changes in MD milk FA composition were observed 1 day after the cows were moved to a new paddock. The MD cows grazed by layers from the bottom layers of the previous paddock to the top layers of the subsequent new paddock, resulting in bites with high organic matter digestibility (OMD) value and CP content and a low fibre content at the beginning of each paddock utilisation. These changes could induce significant day-to-day variations of the milk FA composition. The milk fat proportions of 16:0, saturated FA and branched-chain FA decreased, whereas proportions of de novo-synthesised FA, 18:0, c9-18:1 and 18:2n-6 increased at paddock change. During LD plot utilisation, the heterogeneity of the vegetation allowed the cows to select vegetative patches with higher proportion of leaves, CP content, OMD value and the lowest fibre content. These small changes in CP, NDF and ADF contents of LD herbage and in OMD values, from the beginning to the end of the experiment, could minimally modify the ruminal ecosystem, production of precursors of de novo-synthesised FA and ruminal biohydrogenation, and could induce only small day-to-day variations in the milk FA composition.     

Sheltering behaviour and lamb mortality amongst shorn Merino ewes lambing in paddocks with a restricted area of shelter or no shelter

A flock of 380 pregnant Merino ewes was shorn and randomised between two 12-ha paddocks. An area of shelter containing five grass hedges 90 m long, 0.5 m wide and 10 m apart was located in the middle of one paddock at a site that was not previously used as a preferred resting area (camp). The sheep in this paddock used the shelter extensively at night and also during the day when the weather was cold and windy. This use of shelter continued for seven weeks and subsequently some use of the shelter was made when the sheep were returned to the paddock after an absence of eight days. Sheep from the un-sheltered paddock given access to the shelter for these eight days made no use of it.Lamb mortality in the sheltered paddock (about 20%) was half that in the unsheltered paddock; about 50% of lambs born appeared to be twins. Deaths of lambs from apparent hypothermia were much more frequent during several days of windy weather than during calm weather, and were higher in the unsheltered paddock (12%) than in the sheltered paddock (5%). Significant wet weather was not experienced.It may be possible to train sheep to spend resting periods in sheltered areas by shearing during the cooler months; subsequently a high proportion may lamb in shelter, thereby reducing lamb mortality.     

Fine-scale spatial distribution of herbage mass,herbage consumption and fecal deposition by cattle in a pasture under intensive rotational grazing

Herbage mass, herbage consumption and fecal deposition by animals were monitored for 2 years in 182 fixed locations (0.5 × 0.5 or 1 × 1 m) in a sown pasture (1.1 ha) grazed rotationally by cattle (42–45 animals). Fecal deposition was more spatially variable (higher values of coefficient of variation) than herbage mass and consumption, with consistently significant bias from the normal distribution in both skewness and kurtosis. In terms of spatial pattern, herbage mass and consumption were always or almost always spatially heterogeneous (nonrandom spatial pattern), while fecal deposition was less frequently heterogeneous or usually homogeneous (random spatial pattern). The spatial heterogeneity in herbage mass was interpreted as being created in the early grazing season possibly through spatial heterogeneity in soil-related factors, and maintained until the late grazing season mainly by herbivory where the animals always left more herbage uneaten at locations with higher pre-grazing herbage mass. Even when cumulated for 2 years (56 days of grazing), herbage consumption and fecal deposition were still considerably spatially variable. Such nonuniform cumulation of animal impacts, however, is not likely to have a negative effect on the grazing system (paddock as the major grazing area) because (1) the animals almost always consumed more herbage from locations with higher herbage mass, resulting in a less variable degree of utilization (consumption/production) across the paddock; (2) fecal deposition on the paddock was not abundant, due to the concentration of feces in the resting area adjoined; and (3) fertilizer was regularly applied to the paddock as management.     

Prolonged exposure to sheep grazing reduces the palatability of Australian saltbush populations

This study examined the variability in palatability of populations of Atriplex vesicaria and the influence of past grazing history on mean palatability to sheep. Twenty saltbush plants (10 male, 10 female) were collected from each of six locations across chenopod shrubland of South Australia; three populations came from areas with long records of intensive sheep pastoralism and three from areas with negligible stock grazing in the past. The plants were transplanted into an experimental paddock at Middleback Station, near Whyalla, South Australia and the paddock was grazed by three sheep for nine days. Relative palatability of the populations was assessed by their rates of decline in bush biomass, as indexed by loss of tagged terminal shoots. Overall accumulated tag loss after 9 days was significantly different between populations. These differences were enhanced when dung drop in paddock subdivisions, flowering status of bushes, and leaf sodium and potassium concentrations were included as covariates in tag loss models. Although there was no clear separation of grazed versus ungrazed populations by tag loss alone, the covariate models demonstrated a significant difference between grazing history types, with grazed populations being less palatable. Examination of model residuals showed heterogeneity of palatability to be higher in the grazed populations. This study indicates that the piosphere is a gradient of variability in palatability as well as a gradient of floristic composition.     

The conservation value of paddock trees for birds in a variegated landscape in southern New South Wales. 2. Paddock trees as stepping stones

The use of paddock trees as stepping stones by birds was assessedin a grazing landscape in southern New South Wales, Australia. A totalof 70 paddock tree sites was surveyed for 20 min each inthe morning, and 36 sites were surveyed again in the afternoon in March2000. During the surveys, the presence, direction of arrival, anddirection of departure to and from sites was recorded for each bird. Astepping stone effect of paddock trees was examined in two ways: (1) byanalysing the arrival and departure direction of birds relative tosurrounding vegetation cover, and (2) by analysing the departuredirection of birds relative to their arrival direction. An arrivaldirection was obtained for 150 independently acting groups of birds, anda departure direction was obtained for 203 independently acting groupsof birds. Both arrival and departure direction were obtained for 87independently acting groups. Foliage-foraging birds tended to followrelatively densely vegetated areas. There was some indication thatgranivores and nectarivores also preferred to move along denselyvegetated areas. This trend was absent for open-country species. Allgroups of birds examined tended to return to their place of origin ormove in the opposite direction of their arrival. This trend was mostpronounced for nectarivores and the foliage-foraging White-plumedHoneyeater (Lichenostomus penicillatus), and lesspronounced for open-country species and parrots. The results arediscussed in relation to the biology and ecology of the various speciesof birds. We conclude that paddock trees have the potential to enhancelandscape connectivity by acting as stepping stones to assist movement.This further highlights their conservation value as demonstrated in thefirst paper of this series.     

Grassland dynamics under sheep grazing in an Australian Mediterranean type climate

Grassland dynamics in a degraded disclimax grassland dominated by Danthonia caespitosa Gaudich. are examined using both demographic and multivariate approaches in an experiment designed to determine the effect of grazing intensity and exclosure on pasture dynamics. The experiment ran for 20 years from 1949 to 1968, using permanent quadrats at 3 grazing intensities and within exclosures. Demographic studies of some perennial grass species demonstrated markedly different responses to grazing; Danthonia caespitosa was unaffected by grazing but responsive to seasonal rainfall differences. Enteropogon acicularis survived only on protected sites. Numerical classification of total species set (121 species) for six observation periods demonstrated that community types were sensitive to differences in winter rainfall, and time since the start of experiment. Principal component analysis of permanent quadrat observations for individual years demonstrates quadrat trajectories which confirm this and indicate progressive divergence of the successional trends of the grazed and ungrazed quadrats. Repeated analysis on grazed quadrats only, shows that three components of pasture dynamics can be recognized; these are trend (succession?) and seasonal differences, each of which account for about 20% of the variance, and differences due to soil heterogeneity in the experimental paddock (8% of variance accounted for). No effect of grazing intensity was detected. Multivariate techniques can provide a clear partitioning of types of dynamic behaviour present in grassland communities. It is concluded that partitioning of environmental heterogeneity prior to demographic studies would increase their sensitivity.

     

Effects of grazing on plant species composition and spatial distribution in rangelands of the Sahel

The effects of grazing by livestock on plant species composition and spatial distribution have been studied at Sadoré, Niger. Herbaceous species were recorded in plots of increasing size from 1/64 to 1024 m² in ten fallow plots subjected to five different grazing treatments over the previous three years. Treatments consisted of three intensities of grazing, and of protection from grazing for either 3 or 14 years. For all treatments, the number of species fitted a normal distribution with the log (ln) of the area inventoried. However, the fit improved slightly when the model included two successive log-normal distributions respectively considered as species distribution within a patch and at the patch mosaic scale. Across treatments, the optimal sampling areas averaged 3.8 ± 1.1 m² for the within-patch and 725 ± 113 m² for the mosaic scale distributions. It is argued that similarity between treatments in the overall log-normal distribution resulted from compensations between the divergent trends that affected species distribution within and across patches depending on the grazing status. Long-term protection resulted in a regular spatial arrangement of highly contrasted, but internally homogeneous patches. Heavy grazing ensued the dominance of a few species in contagious patches but also left niches for scattered individuals of other species. Tests of the relative frequency of each plant species, together with the average area needed to record that species, were used to characterize specific response to grazing. A majority of species encountered in old Sahelian fallows were either fostered by grazing, indifferent or tolerant to grazing. However, more than a third of the species appeared sensitive to heavy grazing, and no relationships were found between species response to grazing and palatability.     

Diurnal activity patterns of elephant in the Sengwa Area, Rhodesia

Nine different diurnal activities of elephant—grazing, browsing, debarking, drinking, wallowing, resting in the shade, resting in the open or sun, certain social activities and walking—were monitored during the day. Possible reasons for seasonal differences in time spent per hour engaged in each of these activities are given.     

Comparison of biodiversity and ground cover between a commercial rotationally grazed property and an adjacent nature reserve in semi‐arid rangeland

Continuous livestock grazing can have negative effects on biodiversity and landscape function in arid and semi‐arid rangelands. Alternative grazing management practices, such as rotational grazing, may be a viable option for broad‐scale biodiversity conservation and sustainable pastoral management. This study compared ground cover, plant species composition and floristic and functional diversity along gradients of grazing intensity between a pastoral property rotationally grazed by goats and an adjacent nature reserve (ungrazed by commercial livestock) in semi‐arid south‐eastern Australia. Understorey plant species composition differed significantly between the rotationally grazed property and the nature reserve, with a greater proportion and frequency of palatable species recorded in the nature reserve. Understorey plant species richness, diversity, functional biodiversity measures and ground cover declined with increasing grazing pressure close to water points under commercial rotational grazing management. However, at a whole‐paddock scale, there were few differences in plant biodiversity and ground cover between the rotationally grazed property and the nature reserve, despite differences in overall plant species composition. Flexible, adaptive, rotational grazing should be investigated further for its potential to achieve both socio‐economic and biodiversity conservation outcomes in semi‐arid rangelands to complement existing conservation reserves.     

The effects of maternal influences on sheep: Breed differences in grazing,resting and courtship behaviour

Clun Forest and Welsh Mountain sheep were lambed over the same period and half the lambs were cross-fostered by the other breed. Two weeks after completion of lambing, half the female lambs were transferred from the lowland lambing area to fenced upland pastures (Clun-reared separate from Welsh-reared) until approximately 6 months of age, the dams being removed from the area entirely at weaning. The remaining lambs were also separately reared (according to breed of rearing ewe) on the lowland. In the latter case the male (entire) lambs were removed to an adjacent lowland paddock at weaning, the females remaining where they were.Subsequent observations when the lambs were six to seven months of age revealed differences in the pattern of grazing and resting amongst the upland reared stock which, in the case of early afternoon resting behaviour, was to a small extent related to breed of lamb but in the other patterns of behaviour studied was, to a large extent, determined by the breed of ewe that reared each lamb.At seven months of age, two mating groups were established from the lowland and upland reared ewe lambs, to which were allocated mother-reared rams in one case and fostered rams in the other. With one exception the rams were drawn from the flock separated from the lowland ewe lambs at weaning. Preferences of each ram were ascertained by the frequency with which they exhibited clear preferences but it was not established whether this reflected sexual preference. Analysis did not reveal any relationship between ewe preference and any of the factors influencing ram preference.     

Spatial variation in the demography and population dynamics of a perennial shrub (Atriplex vesicaria) under sheep grazing in semi‐arid Australian rangelands

Atriplex vesicaria Heward ex Benth. (Chenopodiaceae) is a widespread perennial shrub in southern Australia's chenopod rangelands but is sensitive to grazing. A detailed investigation of the demography and population dynamics of A. vesicaria under sheep grazing was conducted over 6.5 years at a range of sites across a typical paddock to assess the long‐term effects of grazing on the species and elucidate the mechanisms of population change under grazing. The effects of rainfall on recruitment and mortality were also examined. Six‐monthly censuses of all A. vesicaria individuals were conducted in permanent grazed and ungrazed plots at sites located across an 1100‐ha paddock. Grazing increased adult shrub mortality close to water and reduced recruitment over a broader area of the paddock, but seedling survival did not appear to be affected by grazing. As a result of these changes, the population declined on grazed plots up to 2200 m from water during the study, but the decline was greatest closer to water. The population was most dynamic at the sites furthest from the water point where it was unaffected by grazing because of the greater recruitment and mortality of young plants, but because these processes balanced out over time, population density was effectively unchanged by the end of the study. Although statistical models indicated that six‐monthly rainfall did not explain temporal variation in recruitment or mortality, rainfall nevertheless has a central role in both processes. In particular, longer periods of favourable rainfall and drought appear to have an important influence on recruitment and mortality, respectively, with heavy grazing during a drought period increasing mortality. Occasional shortages of seed or rains occurring during the warmer months when seed germination is limited possibly explain poor recruitment at sites unaffected by grazing following good rainfall.     

The influence of environment on daily maintenance behaviour of free-ranging Shorthorn cows in central Australia. III. Detailed analysis of sequential behaviour patterns and integrated discussion

This is the third of a series of three papers which report on maintenance behaviour of individual Shorthorn cows observed over 24-hour periods at fortnightly intervals for two years in central Australia. In this part, sequences of activities are analysed using Markov chain methods, and this is followed by an integrated discussion of the results of all three papers in the series. Temporal grazing patterns, distance travelled, elimination and watering frequencies, and distribution of the cattle in the available plant communities at daybreak were examined in Part I. The continuously-recorded data on grazing, walking, ruminating, resting, and drinking were analyzed in Part II using multivariate and univariate statistical techniques to relate duration and incidence of activities to several environmental factors.The sequences of activities of cows exhibit five basic patterns: summer day and night, autumn night, winter/spring night and autumn/winter/spring day. Kinetograms, diagrams showing activity sequences, were used to give a graphical representation of the dynamic way in which the activities are structured under each of these conditions. A major feature was that during the day, standing resting is a “pivotal” activity and many of the other activity changes pass through this; in particular an occurrence of standing resting of considerable duration tends to separate active behaviours (grazing, walking) from passive behaviours (especially those involving lying). At night, in contrast, bouts of grazing perform this pivotal role. The seasons differed largely in the way activities following grazing were performed, with cattle in summer being more likely to go directly from grazing to ruminating rather than from grazing to standing to ruminating as they do in other seasons.The overall discussion brings out the way in which the animal structures many different aspects of its behaviour in coping successfully with the periodically stressful environment of central Australia. All analyses showed that there was some adjustment of activity as seasons changed, but that no single environmental factor had a major influence. Behavioural patterns differed from day to night, but moonlight nights were not used differently from those without moonlight. Somewhat surprisingly, little influence of forage condition on behaviour was found. In particular, it appeared that, within the range of conditions observed in the study, the cows did not need to adjust the length and number of bouts of grazing to cope with varying forage quantity and quality, although they did seem to have to graze more widely as forage became scarcer. The main behavioural adjustment seemed to be an increase in frequency and length of bouts of ruminating in summer. Comparison with other studies suggests that cattle behaviour is particularly robust under a wide variety of conditions.Several management recommendations follow from the discussion; in particular the use of smaller paddocks and possibly of breeds which have less energy loss due to rumination in summer are suggested.     

Population dynamics of Trichostrongylus colubriformis in sheep: computer model to simulate grazing systems and the evolution of anthelmintic resistance

A computer model was developed to simulate Trichostrongylus colubriformis populations, their level of resistance to the common anthelmintics, host mortalities and acquired immunity. Predictions were based on sheep management practices such as lambing, weaning, sheep/paddock rotation, anthelmintic treatment, the use of controlled release devices (capsules) for anthelmintic delivery and daily meteorological records to determine the development and survival of infective larvae (L3) on pasture. Evolution of drug resistance was determined by a simple genetic system which allowed for up to three genes, each with two alleles, to give a maximum of 27 genotypes associated with one drug or three genotypes for each of three drugs. The model was validated against egg counts, L3 counts on pasture and host mortalities observed in a grazing trial, however, aspects of the model such as the development of drug resistance and use of the model in a variety of climatic zones have yet to be tested against field observations. The model was used to examine the impact of grazing management and capsule use on anthelmintic resistance and sheep production over 20 years using historical weather data. Predictions indicated that grazing management can play a dominant role in parasite control and that capsule use will reduce sheep mortalities and production losses, and in some circumstances will not cause a substantial increase in anthelmintic resistance for up to 5 years.     

Seasonal changes in circadian grazing patterns of Kerry cows (Bos Taurus) in semi-feral conditions in Killarney National Park, Co. Kerry, Ireland

Domestic cattle generally graze during the day although some night-time grazing also occurs. However, questions remain as to the effect of management on circadian grazing patterns. This study provides for the first time a quantification of seasonal, circadian and animal variation in grazing behaviour and grazing time in cattle in semi-wild conditions.The objectives of the study were to examine how daily grazing times and the temporal distribution of grazing activity changed with season and to examine the extent to which grazing patterns were influenced by day-length. A group of 12 heifers of the Kerry breed continuously grazed a lowland field of 4.7ha. The old permanent pasture sward was dominated by Holcus spp. and Agrostis spp. Feed availability was never limiting. Length and periodicity of grazing were recorded using vibracorders attached to the necks of seven animals.Results showed that daily grazing times remained constant over most of the grazing season (circa 10-11h per day), however, some variation occurred late in the season. The temporal distribution of grazing activity changed as the season advanced so that by October grazing patterns became significantly different to those of July. The time interval between grazing bouts at dawn and dusk decreased with decreasing day-length. An increased percentage of night-time grazing occurred at shorter day-lengths.It is concluded that there is a significant seasonal effect of day-length on temporal distribution of grazing activity with night-time grazing featuring more as day-length decreases. The maintenance of similar total daily grazing times in the face of changing day-length (with the exception of late in the season) suggests that daily grazing times are a function of the attainment of a relatively constant nutritional requirement by the animal.     

Regional productivity mediates the effects of grazing disturbance on plant cover and patch‐size distribution in arid and semi‐arid communities

Patch‐size distribution and plant cover are strongly associated to arid ecosystem functioning and may be a warning signal for the onset of desertification under changes in disturbance regimes. However, the interaction between regional productivity level and human‐induced disturbance regime as drivers for vegetation structure and dynamics remain poorly studied. We studied grazing disturbance effects on plant cover and patchiness in three plant communities located along a regional productivity gradient in Patagonia (Argentina): a semi‐desert (low‐productivity community), a shrub‐grass steppe (intermediate‐productivity community) and a grass steppe (high‐productivity community). We sampled paddocks with different sheep grazing pressure (continuous disturbance gradients) in all three communities. In each paddock, the presence or absence of perennial vegetation was recorded every 10 cm along a 50 m transect. Grazing effects on vegetation structure depended on the community and its association to the regional productivity. Grazing decreased total plant cover while increasing both the frequency of small patches and the inter‐patch distance in all communities. However, the size of these effects was the greatest in the high‐productivity community. Dominant species responses to grazing explained vegetation patch‐ and inter‐patch‐size distribution patterns. As productivity decreases, dominant species showed a higher degree of grazing resistance, probably because traits of species adapted to high aridity allow them to resist herbivore disturbance. In conclusion, our findings suggest that regional productivity mediates grazing disturbance impacts on vegetation mosaic. The changes within the same range of grazing pressure have higher effects on communities found in environments with higher productivity, markedly promoting their desertification. Understanding the complex interactions between environmental aridity and human‐induced disturbances is a key aspect for maintaining patchiness structure and dynamics, which has important implications for drylands management.     

Grazing without grasses: Effects of introduced livestock on plant community composition in an arid environment in northern Patagonia

Question: How does grazing intensity affect plant density, cover and species richness in an Patagonian arid ecosystem? Location: Monte steppe ecoregion, SW Argentina. Methods: I analysed the effect of grazing on plant density, cover and species richness using a stocking rate gradient within the same habitat. Six paddocks were used with stocking rates ranging between 0.002 – 0.038 livestock/ha. Plant density, species richness, plant cover and percentage of grazed branches were determined by sampling plots within each paddock. The percentage of grazed branches was used as an independent measurement of grazing intensity. Results: Higher stocking rates were related to lower plant density, species richness and plant cover. The paddock with the lowest grazing intensity had 86% more plants per unit area, 63% more plant cover and 48% higher species richness. The percentage of grazed branches and the quantity of dung increased with stocking rate. Conclusions: Introduced livestock seriously affect native vegetation in the Patagonian Monte. The damage observed in this xerophytic plant community suggests that plant adaptations to aridity do not provide an advantage to tolerate or avoid grazing by vertebrate herbivores in this region. Plant degradation in this arid environment is comparable to the degradation found in more humid ecosystems.     

Effect of grazing on plant patterns in arid ecosystems of Patagonian Monte

Our objective was to assess the relationship between the spatial patterning of perennial grasses (total, grazed, and non‐grazed) and shrub patches in rangelands under different grazing pressures of the Patagonian Monte. We selected three grazed paddocks with the usual stocking rate for the area, where previous studies showed that a piosphere formation is common. At each paddock, we analysed the grain of heterogeneity at sites located at two distances from the single watering point (near, far), using high‐resolution aerial photographs. At these sites, we also assessed in the field the density, size, cover, and spatial patterning of grazed and non‐grazed perennial grasses and shrub patches. The grain of heterogeneity of shrub patches was coarser in sites near the watering point than in those distant from it, as a consequence of the increase in size of both, bare soil and shrub patches. Field sampling showed that a coarse grain of heterogeneity relative to fine‐grained sites resulted from changes in species composition, increased bare soil areas and reduced perennial grass cover. In coarse‐grained sites, lower perennial grass cover resulted from lower density and/or smaller size of grass bunches than in fine‐grained sites. We did not find significant differences among sites in the proportion of perennial grazed grasses. Since the density and cover of perennial grasses was higher in fine‐ than in coarse‐grained sites, we suggested that fine‐grained sites are more important as feeding stations than coarse‐grained sites. The consequences of this differential use could lead to degradation of fine‐grained sites and to higher homogeneity in spatial plant structure and floristic composition within paddocks with respect to the condition observed at present, increasing the size of the highly degraded zone within the piosphere. At the patch level, we found that at about one third of the sampled transects, both total and non‐grazed perennial grasses were spatially aggregated with shrub patches. However, in most transects grazed perennial grasses were indifferently distributed in relation with shrub patches, showing that grazers display high selectivity of foraging sites at macro level (i.e. high and low grazing pressure sites at the paddock level), but random occupancy of vegetation units (randomness in the distribution of grazed perennial grasses at the patch level). The intensity of the positive association between non‐grazed grasses and shrub patches was higher in fine‐grained than in coarse‐grained sites and may be attributed to higher protection against herbivores associated to denser shrub patches in fine‐ relative to coarse‐grained sites. We concluded that a feedback exists between the spatial distribution of species preferred by grazers and the spatial patterning of use of these species.     

Fan cooling of the resting area in a free stalls dairy barn

This summer study evaluated the effect of providing additional fans (cooling) in the resting area within a free-stall dairy barn that had fans and sprinklers in the feeding area and paddock availability. Thirty cows were divided into two homogenous groups and kept in two pens: one had the resting area equipped with two fans (FAN) while no fans were added to the other resting area (CON). Microclimatic parameters, rectal temperature (RT), breathing rate (BR), milk yield, and milk pH traits were recorded. Time budgeting and the behaviour of the cows (time spent in the feeding area, standing and lying in other areas) were also recorded using digital video technology. Two slight-to-moderate heat waves were observed. During the hottest period the daily maximum temperature recorded was 33.5 °C and the daily maximum THI was 81.6. During this period, the BR and RT increased only slightly in both groups, with lower BR (n.s.) in FAN compared with CON. Milk yield was better maintained (n.s.) in FAN compared with CON during the hottest period. The FAN cows showed a greater (P?<?0.05) lying time in the free stalls (9.5 and 8.6 h/day in FAN and CON, respectively), whereas CON cows made greater (P?<?0.05) use of the paddock during evening and late evening hours. Consequently, the total daily lying time was 13.5 h/day in both groups. In conclusion, the results suggest that using fans in the resting area improves cow comfort, which increases use of the resting area. The lying time results also suggest that the benefits of providing ventilation in the resting area might be more evident in barns where there is no paddock.     

Bull selection and use in northern Australia. 5. Social behaviour and management

Calf output of bulls was derived using DNA typing for paternity following multiple-sire mating at two sites in northern Australia. At Swan's Lagoon Beef Cattle Research Station, 12, mixed-age, Brahman cross bulls were continuously mated with an average of 325 females in a 22km2 open-savannah paddock. Water was available in two troughs. Behaviour of the bulls and location of cows were monitored. At Kamilaroi Station, 2- to 2.5-year-old Brahman bulls were introduced to the study. Twenty-four bulls (HIGH%) were mated in an 84km2 paddock for 3.5 months to 411 heifers in 1995/1995 and for 4.5 months to 350 heifers and 320 first-lactation cows in 1995/1996. A second group of 10 bulls (LOW%) selected on reproductive soundness was mated concurrently in a neighbouring 60km2 paddock to 411 heifers in 1995/1995 and to 350 heifers and 298 first-lactation cows in 1995/1996. In each paddock in both years, 300-350 females were expected to cycle during mating. Both paddocks were flat and semi-forested and water was available only at troughs. At both sites, detailed physical and reproductive examinations of all bulls were conducted prior to and post-mating.Calf output of individual bulls was highly variable but repeatable (r=0.6-0.7) between years. Up to 90% of the 270-380 calves resulting from each mating were sired by between 6 and 8 bulls. Reducing from 3.7 to 2.8% bulls:females at Swan's Lagoon did not delay conceptions. At Kamilaroi, reproductively sound bulls achieved an estimated 5-6 conceptions per week over the peak mating period when sufficient cycling females were available. Differences in pregnancy rates between paddocks appeared due to differences in nutrition and it appeared that conceptions were not delayed with LOW% vs. HIGH% bulls. Variance between bulls in calf output was substantially lower when fewer bulls were used. Bull attrition occurred each year in the HIGH% paddock but not in the LOW% paddock. Calf output was unrelated to body condition of bulls.Seven of the 12 bulls in one 2-year period at Swan's Lagoon appeared to restrict their movement range to 250-750ha for 90-100% of the time. These ranges expanded when the bull:female ratio was reduced. Only one of the nine bulls remained within a 500ha home range for at least 85% of the time during peak mating in 1998 at 2.8% bulls:females. In previous years with 3.7% bulls:females, up to eight of the 12 bulls had remained within a 500ha home range for 85% of the time. Bull behaviour related to high calf output included restricted movement range, grazing with females at a majority of observations, stable social behaviour, and social dominance.These observations demonstrate that multiple-sire mating of reproductively sound Brahman and Brahman-derived bulls at 2.5% of cycling females will not jeopardise herd fertility under extensive management in northern Australia.     

Climate‐mediated habitat selection in an arboreal folivore

The decisions that animals must make to achieve a balance between quantity and quality of resources become more difficult when their habitats are patchy and differ greatly in quality across space and time. Koalas are a prime subject to study this problem because they have a specialised diet of eucalypt leaves and need to balance nutrient and water intake against toxins in the leaves, all of which can change with soil type and climate. Koalas are nocturnal and spend most of the day resting and therefore choose trees for reasons other than feeding, particularly for thermoregulation. We GPS‐tracked 40 koalas over 3 yr to determine their shift in tree selection between day and night, and in relation to daily maximum temperature, in a patchy rural landscape in north‐western NSW, Australia. The species, degree of shelter, diameter, height and elevation of each visited tree were recorded. We used generalised linear mixed effects models to compare tree use between day and night and maximum daily temperature. Koalas used more feed‐trees during the night, and more shelter‐trees during the day. They also selected taller trees with more shelter in the day compared with night. As daytime temperatures rose, koalas increasingly selected taller trees at lower elevations. Our results demonstrate that koalas need taller trees, and non‐feed species with shadier/denser foliage, to provide shelter from heat. This highlights the need both for the retention of taller, mature trees, such as remnant paddock trees, and the planting of both food and shelter trees to increase habitat area and connectivity across the landscape for arboreal species. Retaining and planting trees that provide optimum habitat will help arboreal folivores cope with the more frequent droughts and heatwaves expected with climate change.