Agriculture and Food Systems - Research Publications
Now showing items 1-12 of 209
The effect of nano-chromium on growth performance and metabolism of pigs and sheep
Chromium (Cr) is an essential mineral element for humans and animals. Various forms of Cr have been used in farm animals in order to improve growth performance, insulin sensitivity, immune response, carcase traits and to reduce stress responsiveness. However, Cr is normally poorly absorbed and utilised even when supplemented in an organic form, perhaps in part because of the tendency to form large aggregates. Interestingly, the efficiency of uptake of 100 nm size particle by intestinal tissue was 15 to 250 fold higher compared to 1μm size particles. This thesis aims to develop a novel nano sized Cr tri-picolinate (nCrPic) and examined the effect of nCrPic on growth performance, body composition and physiological and metabolic response to dietary fat and heat stress in pigs and sheep. Four experiments involving different particles size Cr, different dose nCrPic and cinnamon were fed to gilts over the growing-finishing phase and sheep to evaluate the effect of nCrPic and cinnamon on growth performance, carcase trait, and glucose metabolism. In the first experiment, finisher gilts were allocated to eight treatment groups in a 2×4 factorial treatment structure. The respective factors were dietary fat (22 or 57 g/kg) and dietary Cr (0, 400 ppb normal size CrPic, 400 ppb 1μm CrPic (μCrPic) and 400 ppb nm CrPic (nCrPic)). Over the first 21 days, ADG was increased by dietary CrPic, although there was no difference between the different sized Cr. High dietary fat also increased ADG over this period. Dietary CrPic increased carcase weight and muscle depth with responses being greatest for nCrPic. Also, dietary CrPic decreased P2 back fat with the greatest response seen in pigs fed nCrPic and a high fat diet. Furthermore, dietary CrPic tended to decrease plasma insulin without changing plasma glucose indicating an improvement in insulin sensitivity. Moreover, work reported in this thesis further examined the changes occurring at the mRNA level in finisher gilts fed with nCrPic (0 or 400 ppb nCrPic) and fat (22 or 57 g/kg). Skeletal muscle and subcutaneous adipose tissue were collected 25 minutes post-slaughter. This experiment provided some strong evidence that dietary nCrPic can improve insulin sensitivity in pigs consuming a high fat diet. In particular, the expression of the insulin-signaling pathway genes PI3K and AKT were increased by dietary nCrPic. Furthermore, the expression of SOCS3 in skeletal muscle, which can aggravate insulin resistance, was reduced by nCrPic. Dietary nCrPic also increased UCP3 and IL-15 in skeletal muscle, both of which facilitate glucose metabolism. In subcutaneous adipose tissue, the expression of adiponectin was up-regulated by dietary nCrPic. These findings indicate the improvement in the insulin-signaling pathway by dietary nCrPic may be via decreased SOCS3 and increased UCP3 and IL-15 in skeletal muscle, as well as increased adiponectin in subcutaneous adipose tissue. The second experiment was designed to examine the effects of nCrPic on growth performance, carcase traits in finisher gilts under commercial pig production facility. Finisher pigs were allocated to either control or nCrPics treatment during the mid-summer (January-February, 2011). The average maximum temperature during the experiment was 29.7 oC, with a total of 24 days where the daily maximum temperature was above 28 oC. The data reported in this chapter indicated that dietary nCrPic supplementation at 400 ppb can increase feed intake in finisher gilts during mid-summer suggesting that nCrPic can ameliorate some of the negative effects of heat stress in pigs, possibly via decrease of circulatory cortisol. These results provided an interesting insight into the anti- heat stress response of nCrPic in farm animals. The third experiment investigated the effects of two different doses (400 ppb and 800 ppb nCrPic) in sheep. Additionally, the physiological responses to chronic heat stress were also examined. Animals were exposed to temperatures of either an average 22.3 °C ambient temperature for thermo-neutral control or peak at an average 40.4 °C for heated animals. The higher ambient temperature resulted in increased rectal and skin temperature, respiration rate, and reduced feed intake and weight gain. Dietary nCrPic ameliorated the increase in rectal temperature observed during heat load. Moreover, dietary nCrPic supplementation also increased feed intake and weight gain when animals were exposed to heat treatment. The metabolic and tissue responses to nCrPic are examined by subjecting these sheep to glucose, insulin and ACTH challenges to assess the metabolic responses to both heat and nCrPic. Tissue samples were also examined for the gene expression responses to heat and nCrPic. In response to the glucose tolerance test, basal plasma glucose was decreased by heat treatment and dietary nCrPic. Sheep fed nCrPic had a lower glucose response as assessed as area under the curve (AUC) and insulin AUC in response to glucose infusion. Animals under heat treatment had a lower NEFA AUC response to glucose infusion. Dietary nCrPic also down regulated the expression of JNK in skeletal muscle tissue. Together, the results from this experiment indicated that nCrPic can improve insulin sensitivity when animal under heat stress and the improvement of insulin sensitivity may be via decrease the expression of JNK in skeletal muscle tissue. A large number of endocrine and inflammatory pathways have been shown to be dysregulated in obesity. These endocrine and inflammatory factors that reduce body fat deposition are usually associated with an improvement in insulin sensitivity. Data from the first experiment showed that dietary nCrPic can decrease body fat and improve insulin sensitivity. Furthermore, cinnamon has been reported to have similar effects to Cr. The fourth experiment reported in this thesis examined the impact of oral supplementation with nCrPic and cinnamon on body fat deposition and insulin resistance in a high fat fed pig model. Data from this experiment provided evidence that dietary nCrPic and cinnamon have effects on glucose and fat metabolism. In particular, dietary nCrPic and cinnamon can improve insulin sensitivity metabolically and via the insulin signaling gene AKT and GLUT4 mRNA expression. Some of these effects may be mediated, at least in part, by alterations in fatty acid oxidation as the evidence showed that UCP3 and CPT-1B mRNA expression in skeletal muscle were up-regulated by dietary nCrPic and cinnamon supplementation. The results presented in this thesis conclude that heat stress is able to impact nutrient partitioning and metabolism. Dietary nCrPic supplementation can improve growth performance and carcase traits as well as amelioration of the negative effect of heat stress is possibly via improved insulin sensitivity. Both nCrPic and cinnamon activate insulin receptors by up-regulating insulin signaling gene expression such as PI3K, AKT, and GLUT4, and genes involved in fatty acid oxidation such as UCP3 and CPT-1B.
The social dimensions of on-farm change to improve water quality and biodiversity. A report prepared for Dairy Australia
Natural resource management issues such as water quality and biodiversity have come to the fore in the Australian dairy industry. A number of projects have been initiated that aim to facilitate on-farm change for improved environmental outcomes. Dairy Australia, the organisation responsible for national dairy industry research and development, recognised that it was important to develop an understanding of the social aspects of the on-farm change process in order to unlock some of the constraints to change in the context of natural resource management issues. This paper outlines the findings of a Dairy Australia funded research project that explored the social dimensions of farm management change for improved environmental outcomes. A diagnostic framework outlining five social dimensions was developed and this framework provides a practical checklist that can be used in the development, implementation and evaluation of projects that seek to facilitate improved natural resource management on farm.The paper identifies the most appropriate methods to explore the social dimensions of the on-farm change process.
A novel predictor of multilocus haplotype homozygosity: comparison with existing predictors
(Cambridge University Press, 2009)
The patterns of linkage disequilibrium (LD) between dense polymorphic markers are shaped by the ancestral population history. It is therefore possible to use multilocus predictors of LD to infer past population history and to infer sharing of identical alleles in quantitative trait locus (QTL) studies. We develop a multilocus predictor of LD for pairs of haplotypes, which we term haplotype homozygosity (HHn) : the probability that any two haplotypes share a given number of n adjacent identical markers or ‘runs of homozygosity’. Our method, based on simplified coalescence theory, accounts for recombination and mutation. We compare our HHn predictions, with HHn in simulated populations and with two published predictors of HHn. Our method performs consistently better across a range of population parameters, including populations with a severe bottleneck followed by expansion, compared to two published methods. We demonstrate that we can predict the pattern of HHn observed in dense single nucleotide polymorphisms (SNPs) genotyped in a cattle population, given appropriate historical changes in population size. Our method is practical for use with very large numbers of individuals and dense genome wide polymorphic DNA data. It has potential applications in inferring ancestral population history and QTL mapping studies.
HvNax3--a locus controlling shoot sodium exclusion derived from wild barley (Hordeum vulgare ssp. spontaneum).
Previous work identified the wild barley (Hordeum vulgare ssp. spontaneum) accession CPI-71284-48 as being capable of limiting sodium (Na(+)) accumulation in the shoots under saline hydroponic growth conditions. Quantitative trait locus (QTL) analysis using a cross between CPI-71284-48 and a selection of the cultivated barley (H. vulgare ssp. vulgare) cultivar Barque (Barque-73, a moderate Na(+) excluder) attributed the control of the Na(+) exclusion trait from CPI-71284-48 to a single locus on the short arm of chromosome 7H, which was named HvNax3. The locus reduced shoot Na(+) accumulation by 10-25% in plants grown in 150 mM NaCl. Markers generated using colinearity with rice and Brachypodium, together with the analysis of introgression lines and F(2) and F(3) families, enabled HvNax3 to be mapped to a 1.3-cM interval. Genes from the corresponding rice and Brachypodium intervals encode 16 different classes of proteins and include several plausible candidates for HvNax3. The potential of HvNax3 to provide a useful trait contributing to salinity tolerance in cultivated barley is discussed.
A SOS3 homologue maps to HvNax4, a barley locus controlling an environmentally sensitive Na+ exclusion trait.
Genes that enable crops to limit Na(+) accumulation in shoot tissues represent potential sources of salinity tolerance for breeding. In barley, the HvNax4 locus lowered shoot Na(+) content by between 12% and 59% (g(-1) DW), or not at all, depending on the growth conditions in hydroponics and a range of soil types, indicating a strong influence of environment on expression. HvNax4 was fine-mapped on the long arm of barley chromosome 1H. Corresponding intervals of ∼200 kb, containing a total of 34 predicted genes, were defined in the sequenced rice and Brachypodium genomes. HvCBL4, a close barley homologue of the SOS3 salinity tolerance gene of Arabidopsis, co-segregated with HvNax4. No difference in HvCBL4 mRNA expression was detected between the mapping parents. However, genomic and cDNA sequences of the HvCBL4 alleles were obtained, revealing a single Ala111Thr amino acid substitution difference in the encoded proteins. The known crystal structure of SOS3 was used as a template to obtain molecular models of the barley proteins, resulting in structures very similar to that of SOS3. The position in SOS3 corresponding to the barley substitution does not participate directly in Ca(2+) binding, post-translational modifications or interaction with the SOS2 signalling partner. However, Thr111 but not Ala111 forms a predicted hydrogen bond with a neighbouring α-helix, which has potential implications for the overall structure and function of the barley protein. HvCBL4 therefore represents a candidate for HvNax4 that warrants further investigation.
Risk of psychiatric illness from advanced paternal age is not predominantly from de novo mutations
(NATURE PUBLISHING GROUP, 2016-07-01)
The offspring of older fathers have higher risk of psychiatric disorders such as schizophrenia and autism. Paternal-age-related de novo mutations are widely assumed to be the underlying causal mechanism, and, although such mutations must logically make some contribution, there are alternative explanations (for example, elevated liability to psychiatric illness may delay fatherhood). We used population genetic models based on empirical observations of key parameters (for example, mutation rate, prevalence, and heritability) to assess the genetic relationship between paternal age and risk of psychiatric illness. These models suggest that age-related mutations are unlikely to explain much of the increased risk of psychiatric disorders in children of older fathers. Conversely, a model incorporating a weak correlation between age at first child and liability to psychiatric illness matched epidemiological observations. Our results suggest that genetic risk factors shared by older fathers and their offspring are a credible alternative explanation to de novo mutations for risk to children of older fathers.