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Many Phytophthora spp. have recently been isolated from native vegetation in Western Australia. As their pathogenicity is often unknown, it is not possible to provide advice to land managers on the impact of site infestation on native plants and how these infestations should be managed. We describe a rapid screening method based on sapwood invasion that has been used to compare the pathogenicity of Phytophthora arenaria, P. cinnamomi and P. multivora. Radial invasion into the xylem of six banksias and three eucalypts was assessed in an excised branch assay in summer and winter. Branches were wound inoculated and invasion was assessed by plating from a strip of tissue cut across the stem at the inoculation point and at 40 mm above and below. A symptomless infection had established in both the bark and sapwood within 6 days. P. arenaria was only isolated from the strip of tissue at the inoculation point. P. cinnamomi was isolated from the sapwood of Banksia attenuata, B. burdettii, B. menziesii and B. speciosa 40 mm above or below the inoculation point in some experiments. P. multivora was isolated from B. speciosa 40 mm below the inoculation point in one experiment. Hyphae of both species were seen in both ray parenchyma cells and xylem vessels. The invasiveness of the Phytophthora spp. was compared on the two groups of hosts using scores for sapwood invasion at the inoculation point. For banksias, P. cinnamomi and P. multivora had significantly higher invasion scores on banksias than P. arenaria but were not significantly different to one another. There was no significant difference between the three Phytophthora spp. on the eucalypt hosts. Assessing sapwood invasion provides a rapid, inexpensive and biologically meaningful way of screening the many Phytophthora spp. that have been isolated from native vegetation.

This experiment evaluated the productivity of 500 Angus cows that differed in genetic merit for either subcutaneous rib fat depth (Fat) or residual feed intake (RFI) based on estimated breeding values (EBVs) and managed under two levels of nutrition. Reproductive rate over four calving opportunities in mature cows and growth performance of progeny to weaning was assessed. Level of nutrition significantly affected all body composition traits for both Fat and RFI line cows. Cows on High-Nutrition were 14–16% heavier (P < 0.001) than those on Low-Nutrition. Differences in EBVs for fatness were reflected in phenotypic fatness at maturity. High-RFI line cows were fatter for both scanned rump (P8) and rib (RIB) fat depth relative to their Low-RFI contemporaries. Of those cows that were lactating, there was no significant effect of line or nutrition on pregnancy rate or days to calving (DC). There was, however, a trend (P < 0.1) in the Low-Fat line cows towards longer DC compared with the High-Fat line cows. There was no significant effect of either line or nutrition on calf birthweight. Calves with mothers on High-Nutrition were 8% heavier at weaning (P < 0.001) than those on Low-Nutrition. Lower EBVs for RFI was associated with higher 200-day growth EBV and heavier calves at weaning. Current carcass BREEDPLAN EBVs can be used to select for changes in cow body composition if desired. In this experiment, Angus cows selected for lower RFI or with below-average fatness EBV and had raised a calf at every previous opportunity were not compromised in pregnancy rate or DC at maturity under varying nutrition such as can be experienced during normal seasonal conditions in southern Australia. However, selection for lower RFI was associated with lower weaning rate (P < 0.05), which warrants further investigation to confidently predict the implications for commercial cattle production.

The present paper focuses on the economic evaluation of the observed differences in maternal productivity of different genetic lines in Angus cattle that were managed under contrasting nutritional regimes typical of southern Australia. Five hundred Angus cows were managed concurrently at two locations in southern Australia. On each site, the cows were managed under the following two different nutritional treatments: High and Low, to simulate different stocking rates. Cows selected for a divergence in either carcass rib-fat depth or residual feed intake based on mid-parent estimated breeding values for those traits, were allocated in replicate groups to either High- or Low-nutrition treatments. By design, the supplementary feeding regime was the same for the High and Low genetic lines to ensure genetic differences were not confounded with management differences. Animal productivity results from the experiment were used as input data to evaluate the economic performance of the four genetic lines under the two nutritional treatments. Two methods were used; the first was a gross-margin calculation of income minus variable costs as AU$ per breeding cow for a 1000-cow herd; the second was a whole-farm linear programming model maximising the gross margin. Stocking rates were optimised by matching the energy requirements for the whole herd with the energy available from pasture and supplementary feed on a representative 700-ha farm. Using the two methods of calculating gross margin (per cow and optimised per hectare), including examination of sensitivity to changes in prices of cattle and supplementary feed, the present study demonstrated that genetically leaner cows due to selection of low fat or low residual feed intake, had gross margins superior to those of genetically fatter cows. They generated more income by selling more liveweight due to heavier weights and higher stocking rates. The results are affected by the management system utilised and some confounding with growth (leaner genetic lines had higher growth estimated breeding values), but will assist producers to make more informed decisions about how to manage animal breeding and nutritional interactions.

The pregnancy rate of heifers affects the efficiency and profitability of beef herds. Heifers extreme in rib fatness (Fat) or post-weaning residual feed intake (RFI) estimated breeding values (EBVs) were evaluated for their pregnancy rates at two locations in the southern agricultural regions of Australia (Struan and Vasse) as part of the Beef Cooperative Research Centre Maternal Productivity Project. Heifers divergent in Fat (High-Fat and Low-Fat) had differences in fat depth pre-joining at the 12/13th rib (4.4 mm vs 3.5 mm) and P8 rump site (6.1 mm vs 4.8 mm). This was associated with significant differences in pregnancy rates over a 9-week joining period (91.5% vs 83.0%) and an even larger difference when calculated over a 6-week joining period (77.3% vs 65.0%). Heifers divergent in RFI (Vasse only) also differed in rib fat (7.6 mm vs 6.4 mm) and P8 fat (11.0 vs 9.2 mm), but not significantly in pregnancy rates between the two RFI (High-RFI and Low-RFI) genotypes following a 9-week (92.4% vs 88.5%) or 6-week (81.2% vs 73.7%) joining period. The phenotypic analysis of the Fat and RFI heifers together indicated that weight and fat depth were the largest contributing factors to variation in pregnancy rates, and age and pre-joining weight gain were not significant. These phenotypic characteristics indicated that producers can manage heifers to particular weight and fat combinations to improve heifer conception rates. Associations of BREEDPLAN EBVs with heifer fertility showed that a shorter days-to-calving EBV had the biggest impact (P < 0.001) on heifer pregnancy rates and rib fat and scrotal size EBVs were close to significant (P < 0.10).

Cow bodyweight gain, calf weaning weight, feed intake and maternal productivity of 500 Angus cows, in 64 replicate groups, were measured over three parities at two locations (Struan and Vasse) as part of the Beef CRC Maternal Productivity Project. The cows were sourced as heifers from the top and bottom 10% of BREEDPLAN Rib Fat EBV (High-Fat and Low-Fat), and from High and Low residual feed intake (RFI) selection lines (High-RFI and Low-RFI). Each of the four genotypes were run under High- and Low-Nutrition (measured as feed on offer) at both sites. The High-Fat cows were 7% more efficient at producing weaner calves under Low-Nutrition than were the Low-Fat cows. This was driven primarily by the 4% difference between the lines in weaning rate. When weaning rate differences were accounted for (as covariate), there was no difference between the Fat lines in the efficiency of weaner weight production. When the weight gain of the cow was included as an output in addition to calf weaning weight, there was also no difference between the Fat lines in efficiency. Low-RFI cows were always more efficient at producing weaner calves than were the High-RFI cows. This was primarily driven through a 7% reduction in annual feed intake (across both nutrition treatments). However, the Low-RFI cows were leaner, had 6.3% lower weaning rate and calved on average 5.4 days later than did the High-RFI cows. Furthermore, the largest differences in feed intake were in spring when feed availability is greatest. In the context of the results herein, a balanced breeding program should include selection for improved reproduction and low RFI.

Australian seedstock cattle breeders have expressed concerns that while there has been genetic improvement in feedlot and abattoir performance of cows, it could have led to a decline in maternal productivity, especially under variable nutritional conditions. This paper describes a substantial project with two components designed to address these issues. The first sub-project was to monitor bodyweight and composition of 7760 young Angus and Hereford cows as they experience variable physiological states (pregnancy and lactation) and seasons. This was conducted on large numbers in seedstock herds. The second sub-project was to monitor more regularly bodyweight, body composition, and calf rearing performance of 500 Angus cows that are genetically divergent for either fat or residual feed intake at two research centres. This also included two levels of nutrition and recording of weekly feed intake of small groups of cows for at least three parities to allow reporting of genotype × nutrition effects on maternal productivity and efficiency. Results from the project are reported in a series of papers with each one having a defined focus.

This paper reports a subset of results from the Beef Cooperative Research Centre-funded Maternal Productivity Project. This research aimed to describe the response of Angus cows of different and divergent genotypes to variable nutritional environments over five breeding seasons. Cows selected for a divergence in either fat depth (HFat vs LFat) or residual feed intake (RFI: HRFI vs LRFI) based on mid-parent estimated breeding values (EBV) for those traits were allocated in replicate groups to either high or low nutritional treatments at two different sites, namely the Vasse Research Centre in Western Australia and the Struan Research Centre in South Australia. The traits reported in this paper include output traits (birth and weaning weight of calves, liveweight change of cows), change traits (change in Rib Fat, P8 fat, eye muscle area and liveweight between specified time points) and reproductive traits [pregnancy rates, percentage calves born alive and days to calving at the days to calving at the second calving opportunity (DC2)]. Having had their first calf, the vulnerability of these young cows to nutritional restriction and how it may adversely affect rebreeding was examined. HFat and HRFI cows were fatter, heavier and had greater eye muscle area than LFat and LRFI, respectively, at all times during the breeding cycle on both levels of nutrition. There was no difference in either days-to-calving or pregnancy rates after the second mating between genotypes. Equally, nutritional treatment had no effect on these traits in this cohort of cows. There was evidence for an implied genetic correlation between Rib Fat EBV, DC2 and pregnancy rates of –0.38 that suggests that selection for leanness may result in reduced fertility of the herd but the effect was not significant herein. As long as producers record the phenotype for both traits and select cows with favourable DC2 as well as low fatness, these problems can be avoided, owing to only 22% of variation in pregnancy rates being explained by DC2 and Rib Fat EBV. Producers can largely be confident that selection for leanness, or increased feed efficiency, has little impact on productivity as long as cows are in adequate body condition to remain healthy and productive.

The effects of corynetoxins (from Lolium rigidum) and tunicamycins on hepatocyte viability and morphology were indistinguishable providing further evidence that these 2 related toxins have equivalent bioactivity and continue to support use of the tunicamycins-based experimental model. In both the cell viability and the cell morphology studies, the treatments fell into 2 distinct groups. The first group included the 2 control treatments and the 5 nM corynetoxins and tunicamycins treatments, and it was not possible to distinguish between the treatments in this group. The second group included all the toxin treatments of 50 nM or greater, and it was in this group that toxic effects of the treatments were very evident. In this group, there was some evidence of a dose rate effect, but corynetoxins treatments could not be distinguished from tunicamycins treatments at each dose rate. There was a good correlation between the results of the 2 studies. Both identified the division of treatments into 2 groups, and in the group in which toxic changes were evident the time sequence of the morphological changes fitted well with the live and dead cell counts. In the morphology study, cell loss commenced at approximately 36 h, was extensive by 76 h and peaked at approximately 96 h.

Growth, carcass characteristics and meat quality of the steer and heifer progeny of autumn (AC: March–April) and winter (WC: June–July) calving cows following weaning in January in each of 3 years (2003–05) were measured. The cows were mated to sires with a high estimated breeding value for either retail beef yield (RBY), intramuscular fat (IMF) or both RBY and IMF. After weaning, the progeny entered one of three growth paths until slaughter at an average steer liveweight of 500 kg: (i) fast – fast growth from weaning on a high concentrate feedlot diet; (ii) slow – slow growth from weaning (~0.6 kg/day) to 400 kg liveweight followed by growth at over 1 kg/day on high quality pasture; or (iii) comp. – 10% weaning weight loss, immediately after weaning followed by compensatory or rapid growth of over 1 kg/day on high quality pasture. Steers on the fast growth path had higher (P < 0.001) P8 fat thickness than those on the slow or comp. growth paths whereas heifers on the fast growth path only had higher (P < 0.001) P8 fat thickness than those on the slow growth path. Animals on the fast growth treatment had higher (P < 0.001) levels of IMF% than the slow animals which were higher (P < 0.001) than the comp. growth treatment. AUS-MEAT and US marbling scores were not different among growth paths. Animals finished on the fast growth path had a lower (P < 0.001) RBY% than those on either the slow or comp. growth paths. The RBY-sired progeny had higher (P < 0.001) finishing liveweight and hot standard carcass weight than either RBY and IMF or IMF-sired animals. IMF-sired progeny had higher (P < 0.01) rib fat thickness than either RBY or RBY- and IMF-sired animals. There was also a similar trend for P8 fat thickness but the effects were not significant. The RBY-sired animals had lower AUS-MEAT marbling scores (P < 0.01), US marbling scores (P < 0.001) and levels of IMF% (P < 0.01) than either of the other two sire treatments. RBY-sired animals also had higher (P < 0.001) estimated RBY% than those from the IMF sires while those by RBY and IMF sires were intermediate and not significantly different from either. Calving time had little influence on most carcass characteristics. However, WC animals tended to be fatter and have higher marbling scores than AC animals. The IMF% was higher (P < 0.01) in WC animals from RBY and IMF sires than in the corresponding AC animals. Heifers had lighter slaughter liveweight, carcass weight, were fatter and had higher marbling scores than steers. Heifers also had lower (P < 0.001) RBY% than the steers. Ossification scores for heifers were higher (P < 0.001) than for steers by ~30 units in AC calves and by 20 units in WC calves. The results of this experiment confirm the effectiveness of using sires with high estimated breeding value for the required characteristics in producing the desired improvements in the progeny. The absence of any interactions of sire type with growth path indicates that differences between sire types will be similar regardless of environmental conditions. Animals raised on a faster growth path after weaning produce carcasses with more fat and more IMF% than those grown on slower growth paths.

Myxomycetes on the bark of dead Banksia attenuata and B. menziesii from the Perth metropolitan area of Western Australia were surveyed by the moist chamber technique, to determine whether the flora was similar on both hosts and what were the most important variables that determined the distribution of the most common species. Twenty-seven species of myxomycetes were recovered, including six new records for Australia (Comatricha rigidireta, Echinostelium elachiston, Paradiacheopsis cf. cribrata, P. rigida, Stemonitopsis amoena and S. cf. hyperopta). Members of the order Stemonitales comprised the largest number of species, whereas members of the Liceales occurred on the most bark pieces. The most common species were Licea kleistobolus, Echinostelium minutum, Comatricha elegans, Cribraria minutissima and Paradiacheopsis fimbriata. Overall, B. menziesii and B. attenuata had very similar myxomycete productivity, diversity and species assemblage, as did the tops and bottoms of the logs. It was concluded that they provided very similar microhabitats for myxomycetes. Both pH and the relative moisture content of the bark had an effect on myxomycete productivity. Bark decomposition level, pH and bark surface (top or bottom) were the most important variables determining the distribution of the most common myxomycete species.