Gut content analysis to distinguish between seed feeding and mycophagy of a biphyllid beetle larva found on Acacia melanoxylon

In a search for potential biocontrol agents for Acacia melanoxylon R. Br. (Mimosaceae), larvae of the beetle Diplocoelus dilataticollis Lea (Coleoptera; Biphyllidae) were found within damaged seeds of A. melanoxylon. The gut contents of larvae and adults were examined to determine whether their diet included seeds, in apparent contradiction to the known mycophagous diet of members of this family of beetles. Calcofluor M2R White, a plant cell-wall staining optical brightener was used to differentiate between plant cell fragments and fungal tissue in the gut content smears. Gut contents of adults of a known seed predator of A. melanoxylon, a weevil of the genus Melanterius, were examined in the same way to provide a benchmark. The gut contents of D. dilataticollis differed from those of Melanterius sp. Fungal structures and microbes were found in the gut of D. dilataticollis, in contrast to plant cell fragments found in the gut of the weevil and from scrapes made directly from seeds. We conclude that larvae of D. dilataticollis feed primarily on fungi associated with damaged seed and therefore may not be the proximate cause of seed damage.

Cattle, crops and clearing: Regional drivers of landscape change in the Brigalow Belt, Queensland, Australia, 1840-2004

Landscape change occurs through the interaction of a multitude of natural and human driving forces at a range of organisational levels, with humans playing an increasingly dominant role in many regions of the world. Building on the current knowledge of the underlying drivers of landscape change, a conceptual framework of regional landscape change was developed which integrated population, economic and cultural values, policy and science/technology. Using the Southern Brigalow Belt biogeographic region of Queensland as a case study, the role of natural and human drivers in landscape change was investigated in four phases of settlement since 1840. The Brigalow Belt has experienced comparable rates of vegetation clearance over the past 50 years to areas of tropical deforestation. Economic factors were important during all phases of development, but the five regional drivers often acted in synergy. Environmental constraints played a significant role in slowing rates of change. Temporal trends of deforestation followed a sigmoidal curve, with initial slow change accelerating though the middle phases then slowing in recent times. Future landscape management needs to take account of the influence of all the components of the conceptual framework, at a range of organisational levels, if more ecologically sustainable outcomes are to be achieved. (c) 2006 Elsevier B.V. All rights reserved.

Feeding strategies for grain-fed cattle in a hot environment

Six Bos taurus (Hereford) steers (body weight 324 22 kg) were used in a 45-day study with a replicated 3 x 3 Latin-square design. Three treatments [ad libitum feeding (ADLIB); limit feeding, 85% of ad libitum (LIMIT); bunk management feeding where steers were only given access to feed from 1600 to 0800 hours the following day (BUNK)] were imposed over 3 periods, with 2 steers assigned to each treatment in each period. Cattle were managed in a temperature-controlled metabolism unit and were exposed to both thermoneutral (17.7degreesC-26.1degreesC) and hot (16.7degreesC-32.9degreesC) environmental conditions. By design, during the thermoneutral period, the ADLIB cattle displayed greater intake (P < 0.05) than the LIMIT group, with the BUNK group being intermediate. However, during the hot period, both the LIMIT and BUNK treatment groups increased feed intake 4-5%, whereas feed intake of the ADLIB treatment group declined nearly 2%. During both periods respiration rate (RR, breath/min) followed the same pattern that was observed for feed intake, with the greatest (P < 0.05) RR found in the ADLIB treatment group (81.09 and 109.55, thermoneutral and hot, respectively) and lowest (P < 0.05) RR in the LIMIT treatment group (74.47 and 102.76, thermoneutral and hot, respectively). Rectal temperature (RT) did not differ among treatments during the thermoneutral period or the first hot day, although during the thermoneutral period the ADLIB treatment group did tend to display a lower RT, possibly as a result of other physiological processes (pulse rate and RR) aiding to keep RT lower. During the hot period, differences in RT were found on Day 5, with the LIMIT cattle having lower (P < 0.10) RT (38.92degreesC) than the ADLIB (39.18degreesC) cattle, with BUNK cattle RT (39.14degreesC) being intermediate. However, when hourly data were examined, the ADLIB cattle had greater(P < 0.05) RT than the BUNK and LIMIT at 1800 hours and greater RT (P < 0.05) than the LIMIT group at 1400, 1500, and 1600 hours. Clearly, a change in diurnal RT pattern was obtained by using the LIMIT and BUNK feeding regimen. Both of these groups displayed a peak RT during the hot conditions, between 2100 and 2200 hours, whereas the ADLIB group displayed a peak RT between 1400 and 1500 hours, a time very close to when peak climatic stress occurs. Based on these results it is apparent that feedlot managers could alleviate the effects of adverse hot weather on cattle by utilising either a limit-feeding regimen or altering bunk management practices to prevent feed from being consumed several hours prior to the hottest portion of the day.

Reproductive and feeding ecology of parasitic gnathiid isopods of epaulette sharks (Hemiscyllium ocellatum) with consideration of their role in the transmission of a haemogregarine

Epaulette sharks Hemiscyllium ocellatum were surveyed on Heron Island, Great Barrier Reef, Australia for gnathiid isopods and protozoan (haemogregarine) parasites to determine the prevalence and intensity of infection and to investigate the potential role of gnathiids as vectors of these haemogregarines, the first such study carried out on elasmobranchs. Juvenile gnathiids were collected and quantified using a novel non-invasive and chemical-free technique and gnathiid squashes were examined for haemogregarine developmental stages. The feeding and reproductive ecology of the Gnathia spp. was investigated to better understand the relationship between gnathiids and haemogregarines. Gnathiids were found on all sharks and intensities ranged between two and 66. Only third-stage gnathiid juveniles were found, which fell into two size groups (A and B). These juveniles remained attached to H. ocellatum for up to 17 days, the longest period of attachment yet recorded for gnathiids. Group A female gnathiids produced broods of 45-187 (median = 120) first stage juveniles from between 54 and 82 days (median = 63 days) after detachment. First stage juveniles survived for an average of 15.8 +/- 0.1 (SEM) days without feeding. The prevalence (6.7%) and parasitaemia (usually

Wetting and the physiological responses of grain-fed cattle in a heated environment

A controlled crossover experimental design was used to determine the effect of altered water sprinkling duration on heifers subjected to heat stress conditions. Heifers were subjected to 3 days of thermoneutral conditions followed by 3 days of hot conditions accompanied by water sprinkling between 1300 and 1500 h (HOT1-3). Then on the following 2 days (HOT4-5), environmental conditions remained similar, but 3 heifers were sprinkled between 1200 and 1600 h ( WET) and 3 were not sprinkled (NONWET). This was followed by a 1-day period (HOT6) in which environmental conditions and sprinkling regimen were similar to HOT1-3. Rectal temperature (RT) was collected hourly, and respiration rate (RR) was monitored every 2 h on HOT Days 2, 4, 5, and 6. Dry matter intake and rate of eating were also determined. Sprinkling reduced RR and RT (P < 0.01) of all heifers during HOT1-3. During HOT4-5, WET heifers had lower (P < 0.05) RT than NONWET from 1300 to 700 h and lower RR from 1400 to 2000 h. Dry matter intake of NONWET heifers was reduced by 30.6% (P < 0.05) during HOT4-5 and by 51.2% on HOT6. On HOT4-5 the dry matter intakes of WET heifers were similar to intakes under thermoneutral conditions. During HOT6, RT was again reduced following sprinkling in all heifers. Comparison of RT and RR of NONWET and WET heifers on HOT1-3 v. HOT6 revealed that under similar environmental conditions, NONWET heifers had increased RT, partially due to carry-over from HOT4-5. However, NONWET heifers had 40% lower feed intake but tended to have lower RR on HOT6 v. HOT1-3. Only RR of WET heifers was greater on HOT6, possibly a result of switching from a 4-h back to a 2-h sprinkling period, while maintaining a 62% greater intake (5.80 v. 3.58 kg/day) than NONWET heifers during this time. Results suggest that inconsistent cooling regimens may increase the susceptibility of cattle to heat stress and elicit different physiological and metabolic responses.

Prevalence, severity, and heritability of Stephanofilaria lesions on cattle in central and southern Queensland, Australia

Observations of cattle in central and southern Queensland are collated to de. ne the prevalence and area of Stephanofilaria lesions associated with infestations of the buffalo fly, Haematobia irritans exigua. The observations were made on herds that were being used for other purposes. In a survey of similar to 1500 animals at Belmont in central Queensland in 1982, 98% of cows and 70% of calves had lesions. Most lesions were on the neck and dewlap and 10% were raw and weeping at the time of sampling. The total area of lesions per animal was strongly related to cattle breed and age. Old Bos taurus animals had the greatest area of lesions, whereas young Bos indicus had the least. Heritability estimates were low, averaging 0.01 for calves and 0.18 for cows. A smaller survey of cows and steers at Craighoyle in central Queensland in 1986 showed a higher numbers of lesions and positive correlations between the total lesion area and animal size. The lesion area increased with tick survival, suggesting that tick-resistant animals are also resistant to Stephanofilaria infection. Steers had smaller areas of lesions than cows, as found previously with cattle ticks. Long-term monitoring observations in central and southern Queensland between 1981 and 1986 showed that the total area of lesions was seasonal with a peak in late summer, consistent with the seasonal incidence of buffalo fly. Animals segregated into Low and High lesion herds maintained their differences over time. The lesions penetrated the dermis of the cattle hides and rendered the affected area unusable, but few lesions occurred on valuable parts of the hide so such economic effects are likely to be insignificant. One animal nearly died of a haemorrhage from a lesion on the dewlap and had to be treated. The results can inform policy on buffalo fly control, and biosecurity preparations in relation to the potential establishment of the OldWorld screw-worm fly, Chrysomyia bezziana, in Australia, which will be facilitated by the lesions. The results emphasise the significant animal welfare and biosecurity risks posed by the lesions in northern Australia.

Extent and economic effect of heat loads on dairy cattle production in Australia

Objective To investigate the extent of heat load problems, caused by the combination of excessive temperature and humidity, in Holstein-Friesian cows in Australia. Also, to outline how milk production losses and consequent costs from this can be estimated and minimised. Procedures Long-term meteorological data for Australia were analysed to determine the distribution of hot conditions over space and time. Fifteen dairy production regions were identified for higher-resolution data analysis. Both the raw meteorological data and their integration into a temperature-humidity thermal index were compiled onto a computer program. This mapping software displays the distribution of climatic patterns, both Australia-wide and within the selected dairying regions. Graphical displays of the variation in historical records for 200 locations in the 15 dairying regions are also available. As a separate study, production data from research stations, on-farm trials and milk factory records were statistically analysed and correlated with the climatic indices, to estimate production losses due to hot conditions. Results Both milk yields and milk constituents declined with increases in the temperature-humidity index. The onset and rate of this decline are dependent on a number of factors, including location, level of production, adaptation, and management regime. These results have been integrated into a farm-level economic analysis for managers of dairy properties. Conclusion By considering the historical patterns of hot conditions over time and space, along with expected production losses, managers of dairy farms can now conduct an economic evaluation of investment strategies to alleviate heat loads. These strategies include the provision of sprinklers, shade structures, or combinations of these.