ORCID Profile
0000-0002-0359-2297
Current Organisations
The University of Auckland
,
The Liggins Institute, University of Auckland
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Publisher: Elsevier BV
Date: 07-2012
DOI: 10.1016/J.YHBEH.2012.06.006
Abstract: Low food availability often coincides with pregnancy in grazing animals. This study investigated how chronic reductions in food intake affected feeding motivation, and metabolic and endocrine parameters in pregnant sheep, which might be indicative of compromised welfare. Ewes with an initial Body Condition Score of 2.7±0.3 (BCS 0 indicates emaciation and 5 obesity) were fed to attain low (LBC 2.0±0.0,), medium (MBC 2.9±0.1) or high BCS (HBC 3.7±0.1) in the first trimester of pregnancy. A feeding motivation test in which sheep were required to walk a set distance for a palatable food reward was conducted in the second trimester. LBC and MBC ewes consumed more rewards (P=0.001) and displayed a higher expenditure (P=0.02) than HBC ewes, LBC ewes also tended to consume more rewards than MBC ewes (P=0.09). Plasma leptin and glucose concentrations were inversely correlated to expenditure (both P<0.05) and appear to be associated with hunger in sheep. LBC ewes were in negative energy balance, with lower muscle dimensions, plasma glucose, leptin, insulin, cortisol, and insulin-like growth factor-1 concentrations and higher free fatty acids concentrations compared to HBC ewes metabolic and endocrine parameters of the MBC ewes were intermediate. The high feeding motivation and negative energy balance of low BCS ewes suggested an increased risk of compromised welfare. Imposing even a small cost on a food reward reduced motivation substantially in high BCS ewes (despite high intake when food was freely available). Assessment of a willingness to work for rewards, combined with measures of key metabolic and endocrine parameters, may provide sensitive barometers of welfare in energetically-taxed animals.
Publisher: Cold Spring Harbor Laboratory
Date: 30-04-2021
DOI: 10.1101/2021.04.29.441555
Abstract: Facial eczema (FE) in grazing ruminants is a debilitating liver syndrome induced by ingestion of sporidesmin, a toxin belonging to the epipolythiodioxopiperazine class of compounds. Sporidesmin is produced in spores of the fungus Pseudopithomyces chartarum , a microbe which colonises leaf litter in pastures. New Zealand has a high occurrence of FE in comparison to other countries as animals are fed predominantly on ryegrass, a species that supports high levels of Pse. chartarum spores. The climate is also particularly conducive for Pse. chartarum growth. Here, we present the genome of Pse. chartarum and identify the putative sporidesmin gene cluster. The Pse. chartarum genome was sequenced using single molecule real-time sequencing (PacBio) and gene models identified. Loci containing genes with homology to the aspirochlorine, sirodesmin PL and gliotoxin cluster genes of Aspergillus oryzae, Leptosphaeria maculans and Aspergillus fumigatus , respectively, were identified by tBLASTn. We identified and annotated an epipolythiodioxopiperazine cluster at a single locus with all the functionality required to synthesise sporidesmin. The whole genome of Pseudopithomyces chartarum has been sequenced and assembled. The genome is 39.13 Mb, 99% complete, and contains 11,711 protein coding genes. A putative sporidesmin A toxin (cause of facial eczema) gene cluster is described. The genomes of Pse. chartarum and the Leptosphaerulina chartarum teleomorph differ. Comparative genomics is required to further resolve the Pseudopithomyces clade.
Publisher: American Physiological Society
Date: 2005
DOI: 10.1152/AJPREGU.00357.2004
Abstract: In sheep, parturition is initiated by increased fetal hypothalamic-pituitary-adrenal axis (HPAA) activity leading to PGE 2 and PGF 2α production and a rise in the 17β-estradiol-progesterone (E 2 /P 4 ) ratio. Uteroplacental PG production can also increase fetal HPAA activity. Periconceptional maternal undernutrition accelerates fetal HPAA maturation resulting in preterm labor. We determined whether preterm labor was preceded by an increase in PG concentrations and E 2 /P 4 ratio and whether these increases preceded or followed the corresponding rise in cortisol concentrations. Singleton-bearing ewes were nourished ad libitum (N, n = 9) or undernourished (UN, n = 10) to reduce maternal weight by 15% from −61 days (d) to +30 d after mating with ad libitum intake thereafter. Paired maternal and fetal blood s les were collected from 126 d until delivery. Half the UN group delivered prematurely ( SD below mean gestation for the flock). PG and cortisol concentrations and E 2 /P 4 ratio increased before delivery in the same way in both groups. However, the increases occurred 7–10 d earlier in UN than in N animals. In both UN and N fetuses cortisol concentrations rose before fetal and maternal PG concentrations and maternal E 2 /P 4 ratio. Periconceptional maternal undernutrition induces preterm delivery in sheep by advancing the expected prepartum rise in cortisol and PG concentrations and E 2 /P 4 ratio. The rise in fetal cortisol concentration precedes the rise in fetal and maternal PG concentrations and maternal E 2 /P 4 ratio, suggesting that the underlying mechanism is likely to be acceleration of fetal HPAA maturation, resulting in initiation of the normal process of parturition.
Publisher: Elsevier BV
Date: 06-2006
Publisher: The Endocrine Society
Date: 23-07-2015
DOI: 10.1210/EN.2015-1095
Abstract: Adults born preterm are at increased risk of impaired glucose tolerance and diabetes. Late gestation fetuses exposed to high blood glucose concentration also are at increased risk of impaired glucose tolerance as adults. Preterm babies commonly become hyperglycemic and are thus exposed to high blood glucose concentration at an equivalent stage of pancreatic maturation. It is not known whether preterm birth itself, or complications of prematurity, such as hyperglycemia, alter later pancreatic function. To distinguish these, we made singleton preterm lambs hyperglycemic (HYPER) for 12 days after birth with a dextrose infusion and compared them with vehicle-treated preterm and term controls and with HYPER lambs made normoglycemic with an insulin infusion. Preterm birth reduced β-cell mass, apparent by 4 weeks after term and persisting to adulthood (12 mo), and was associated with reduced insulin secretion at 4 months (juvenile) and reduced insulin mRNA expression in adulthood. Hyperglycemia in preterm lambs further down-regulated key pancreatic gene expression in adulthood. These findings indicate that reduced β-cell mass after preterm birth may be an important factor in increased risk of diabetes after preterm birth and may be exacerbated by postnatal hyperglycemia.
Publisher: Elsevier BV
Date: 2010
Publisher: Elsevier BV
Date: 2010
Publisher: Public Library of Science (PLoS)
Date: 22-05-2012
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/EA07033
Abstract: This experiment was conducted to determine the effect of two different feeding levels on ewes during mid and late pregnancy on lamb birthweight and growth to weaning. Twin- and triplet-bearing Romney ewes (n = 80 and 56, respectively) were allocated to one of two feeding regimes and provided pastures with an average sward height of less than 2 cm (~700 kg dry matter/ha) or greater than 4 cm (~1300 kg dry matter/ha). Ewes were allocated to these feeding regimes during mid pregnancy (day 70–107 of pregnancy P70–P107) and were reallocated in late pregnancy (P108–P147). This resulted in four sward height treatments: 2–2, 2–4, 4–2 and 4–4. During mid pregnancy, ewes provided with -cm-high swards had liveweight gains of 262–290 g/day compared with 12–31 g/day for ewes provided with -cm-high swards. In late pregnancy, ewe liveweight gains were influenced by the ewes’ previous nutritional treatment. Ewes in the 2–4 treatment had higher daily gains (538 g/day) than 4–4 ewes (343 g/day). In addition, 4–2 ewes gained 90 g/day compared with 247 g/day for 2–2 ewes. Throughout pregnancy, triplet-bearing ewes were heavier (P 0.05) than twin-bearing ewes, but during lactation ewe weights were similar. On P130, ewes provided with -cm-high swards (4–2 and 2–2) had greater β-hydroxybutyrate (P 0.05) and lower glucose (P 0.05) plasma concentrations than ewes provided with -cm-high swards (2–4 and 4–4). On P139, however, ewes provided with 4–4 swards had higher plasma non-esterified fatty acid and β-hydroxybutyrate concentrations than ewes in all other treatments. Lambs born to ewes in the 4–4 treatment had the greatest birthweights (P 0.05), whereas lambs born to 2–2 ewes had the lowest birthweights. The birthweight of lambs born to 2–4 ewes was similar to that of lambs born to ewes provided with 4–2 and 4–4 swards. At weaning, ewe weights were similar between ewe nutritional treatments and ewes bearing twin or triplet fetuses. These findings suggest that when pasture growth is inadequate to provide pasture sward heights of 4 cm throughout pregnancy, restricted intake in mid-pregnancy may be partially compensated by providing additional pasture in late pregnancy.
Publisher: Public Library of Science (PLoS)
Date: 25-05-2012
Publisher: Elsevier BV
Date: 04-2007
Publisher: Cambridge University Press (CUP)
Date: 20-11-2021
DOI: 10.1017/S2040174420001063
Abstract: Maternal periconceptional undernutrition (PCUN) affected fetal pancreatic maturation in late gestation lambs and impaired glucose tolerance in 10-month-old sheep. To examine the importance of the timing of maternal undernutrition around conception, a further cohort was born to PCUN ewes [undernourished for 61 d before conception (PreC), 30 d after conception (PostC), or 61 d before until 30 d after conception (PrePostC)], or normally fed ewes (Control) ( n = 15–20/group). We compared glucose tolerance, insulin secretion, and sensitivity at 36 months of age. We also examined protein expression of insulin signalling proteins in muscle from these animals and in muscle from a fetal cohort (132 d of gestation n = 7–10/group). Adult PostC and PrePostC sheep had higher glucose area under the curve than Controls ( P = 0.07 and P = 0.02, respectively), whereas PreC sheep were similar to Controls ( P = 0.97). PostC and PrePostC had reduced first-phase insulin secretion compared with Control ( P = 0.03 and P = 0.02, respectively). PreC was similar to Control ( P = 0.12). Skeletal muscle SLC2A4 protein expression in PostC and PrePostC was increased 19%–58% in fetuses ( P = 0.004), but decreased 39%–43% in adult sheep ( P = 0.003) compared with Controls. Consistent with this, protein kinase C zeta (PKC ζ) protein expression tended to be increased in fetal ( P = 0.09) and reduced in adult ( P = 0.07) offspring of all PCUN ewes compared with Controls. Maternal PCUN alters several aspects of offspring glucose homeostasis into adulthood. These findings suggest that maternal periconceptional nutrition has a lasting impact on metabolic homeostasis of the offspring.
Publisher: Elsevier BV
Date: 11-2007
Publisher: Wiley
Date: 03-2012
Publisher: Public Library of Science (PLoS)
Date: 08-10-2012
No related grants have been discovered for Mark Oliver.