Using genes differentially expressed in bulls to classify steers divergently selected for high and low residual feed intake

Feed efficiency is an economically important trait in livestock and residual feed intake (RFI) is a commonly used measure of the trait in beef cattle. Residual feed intake is the difference between the actual feed intake recorded over a test period and the expected feed intake of an animal based on its size and growth rate. It is a heritable trait, and efficient animals have lower RFI values. Several genes have been identified as being differentially expressed in the liver of Angus bulls that have been divergently selected for RFI. The objective of this study was to use genes that are differentially expressed in bulls to classify Angus steers from the same divergent RFI selection lines. Liver samples were collected at slaughter from 40 high RFI and 40 low RFI steers that were ≈23 months old, and had just completed a 251-day feedlot feeding period. RNA samples from the livers were assayed by quantitative real-time PCR for 14 genes, which have been identified previously in bulls. Steers were not measured for RFI, hence the estimated breeding values (EBV) for RFI of their parents were used to calculate their mid-parent (average of the two parents) RFI-EBV. Correlation and discriminant analyses were conducted on the normalised quantitative real-time PCR data from the steers. Discriminant analysis was also conducted on the bull data for comparison. In the steers, 8 out of the 14 genes were significantly (

The Influence of mixtures of parapheromone lures on trapping of fruit fly in New South Wales, Australia

Tephritid fruit flies of economic importance are monitored using traps containing either cuelure (CL) or methyl eugenol (ME) as an attractant. There would be potential economic advantages if both lures could be combined in a single trap without compromising trapping efficiency. This study presents results from two trials testing combinations of cuelure (4.4 mL) and methyl eugenol (0.5 mL and 2.2 mL) in Lynfield traps near Griffith, NSW and in Sydney. For the Griffith trial, the addition of 2.2 mL of methyl eugenol to the standard cuelure wick quadrupled the overall capture of sterile Queensland fruit fly (Qfly) although significant differences were detected in only one of four trials. Traps were placed between 5 and 55 m from the release point, and distance had no significant effect on the number of flies trapped. Time after trap deployment and all time interactions were significant. The proportion of sterile Qfly trapped within three weeks in the first three releases was >91% of total flies trapped in the CL-ME combinations while the CL only treatment recaptured <83% in the same period. Newman fruit fly were trapped with all treatments but not analysed. In Sydney, the combined lure trapped fewer Qfly, although overall the treatments were not significantly different. There was a seasonal effect with cuelure alone attracting more flies than the combination lure in February and August and less in March and April. The combined lure lowered the capture of fruit fly attracted to methyl eugenol by 88%. Reasons for the discrepancies between the trials are discussed, as well as the potential advantages for surveillance for Qfly and exotic fruit flies. Two additional species attracted to the lure combination are noted.5 page(s

Liver microRNA expression revealed the difference in fat metabolism from cattle divergently selected for residual feed intake

MicroRNAs (miRNAs) are short non-coding RNAs that post-transcriptionally regulate expression of mRNAs in many biological pathways. The liver plays a critical role in the synthesis of molecules that are utilized elsewhere to support homeostasis, in converting molecules of one type to another, and in regulating energy balances. We sequenced 48 liver microRNAome from young Angus bulls divergently selected for residual feed intake (RFI). In total we obtained 135 million high quality short sequence reads and more than 93 million unique mapped sequence reads. The top 10 most abundant miRNAs families expressed in liver, represented on average 46-90% of total expressed miRNAs. We did not observe any significant miRNA expression profile for low RFI animals. However, there are distinct miRNA expression patterns separating the animals into two groups that differ significantly in P8 and rib fat thickness. This is consistent with previous finding where high RFI animals had an up-regulated AHR signalling pathway, which plays an important role in fat metabolism. This suggested that some animals have a high RFI value due to excess fat metabolism

Using gene expression information obtained by quantitative real-time PCR to evaluate Angus bulls divergently selected for feed efficiency

Residual feed intake (RFI) is a measure of feed efficiency in beef cattle. Young Angus bulls from lines of cattle divergently selected for RFI were used in a gene expression profiling study of the liver. Quantitative real-time PCR (qPCR) assay was used to quantify the differentially expressed genes and the information was used to examine the relationships between the genes and RFI and to classify the bulls into their respective RFI group. Gene expression of 21 genes in liver biopsies from 22 low RFI and 22 high RFI bulls were measured by qPCR. Gene expressions of 14 of the 21 genes were significantly correlated with RFI. The expression of the genes was used in a principal component analysis from which five components were extracted. The five principal components explained 70% of the variation in the dependency structure. The first component was highly correlated (correlation coefficient of 0.69) with RFI. The genes of the glutathione S-transferase Mu family (GSTM1, GSTM2, GSTM4), protocadherin 19 (PCDH19), ATP-binding cassette transporter C4 (ABCC4) and superoxide dismutase 3 (SOD3) are in the xenobiotic pathway and were the key factors in the first principal component. This highlights the important relationship between this pathway and variation in RFI. The second and third principal components were also correlated with RFI, with correlation coefficients of -0.28 and -0.20, respectively. Two of the four important genes of the second principal component work coordinately in the signalling pathways that inhibit the insulin-stimulated insulin receptor and regulate energy metabolism. This is consistent with the observation that a positive genetic correlation exists between RFI and fatness. The important genes in the third principal component are related to the extracellular matrix activity, with low RFI bulls showing high extracellular matrix activity

Use of garden organic compost in a long-term vegetable field trial : biological soil health

Alternative management practices need to be developed to improve the sustainability of intensive vegetable production in peri-urban areas. A field trial was established in 2005 at Camden, near Sydney, Australia to evaluate the effect of garden organic compost on vegetable production and soil quality relative to conventional practice and under low and high soil P status. The trial comprised seven treatments; compost (garden organic), conventional practice (fertiliser and poultry manure) and a mixture of compost and inorganic fertiliser, all replicated at high and low soil P, plus a nil control. Compost was applied once at the beginning of the trial and again before the 6 th crop (125 dry t/ha/application). Results are reported for 7 consecutive vegetable crops: broccoli, eggplant, cabbage, capsicum, leek, capsicum and broccoli. Production and crop quality parameters were recorded. Soil samples were collected and chemical, physical and biological properties analysed at the time of planting all crops and prior to harvest for crops 4 to 6. Soil biological indicators measured include basal respiration, microbial biomass carbon, hydrolysis of fluorescein diacetate (FDA) and fungal DNA. Compost application significantly increased soil respiration in the first crop but the benefit was diminished in subsequent crops. The response was more pronounced in the crop soils following the second compost application with respiration, biomass and FDA higher in the compost treatments. Preliminary DNA analysis of soil samples collected in the second capsicum crop found a greater diversity of fungal organisms in the low P compost treatment. Future work will look at expanding the assessment of soil biological indicators and the potential for pathogen suppression.10 page(s