Environmental Heat Stress Impairs Placental Function, Fetal Growth and Development, and Postnatal Performance in Livestock

Yates, Dustin T; Chen, Xiaochuan; Limesand, Sean W.

doi:10.1002/9781119949091.ch12

Cited by 7 publications

(8 citation statements)

References 101 publications

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“…), which we have postulated is due to skeletal muscle‐specific programming aimed at nutrient sparing (Yates et al . , ). In this study, we found that impaired glucose oxidative capacity was indeed muscle‐specific and persisted in IUGR lambs at 1 month of age, but was not improved by postnatal β adrenergic modifiers.…”

Section: Discussionmentioning

confidence: 99%

“…The three ADRβ isoforms are expressed in a tissue-specific manner, and as G-protein coupled receptors, their persistent activation lowers their own responsiveness (Collins et al 1991;Wettschureck & Offermanns, 2005). In near-term IUGR fetuses and in 3-week-old IUGR lambs, we have shown that expression of ADRβ2 mRNA is downregulated in adipose tissue and skeletal muscle Yates et al 2012a). This ADRβ2 deficiency could explain restricted growth and muscle accretion in IUGR offspring because stimulation with ADRβ2 agonists repartitions nutrients in growing animals to support anabolic protein accretion and energy-producing oxidative pathways (Byrem et al 1998;Consolo et al 2015;Cadaret et al 2017).…”

Section: Introductionmentioning

confidence: 88%

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Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle

Yates

Camacho

Kelly

et al. 2019

The Journal of Physiology

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Key points Previous studies in fetuses with intrauterine growth restriction (IUGR) have shown that adrenergic dysregulation was associated with low insulin concentrations and greater insulin sensitivity. Although whole‐body glucose clearance is normal, 1‐month‐old lambs with IUGR at birth have higher rates of hindlimb glucose uptake, which may compensate for myocyte deficiencies in glucose oxidation. Impaired glucose‐stimulated insulin secretion in IUGR lambs is due to lower intra‐islet insulin availability and not from glucose sensing. We investigated adrenergic receptor (ADR) β2 desensitization by administering oral ADRβ modifiers for the first month after birth to activate ADRβ2 and antagonize ADRβ1/3. In IUGR lambs ADRβ2 activation increased whole‐body glucose utilization rates and insulin sensitivity but had no effect on isolated islet or myocyte deficiencies. IUGR establishes risk for developing diabetes. In IUGR lambs we identified disparities in key aspects of glucose‐stimulated insulin secretion and insulin‐stimulated glucose oxidation, providing new insights into potential mechanisms for this risk. Abstract Placental insufficiency causes intrauterine growth restriction (IUGR) and disturbances in glucose homeostasis with associated β adrenergic receptor (ADRβ) desensitization. Our objectives were to measure insulin‐sensitive glucose metabolism in neonatal lambs with IUGR and to determine whether daily treatment with ADRβ2 agonist and ADRβ1/β3 antagonists for 1 month normalizes their glucose metabolism. Growth, glucose‐stimulated insulin secretion (GSIS) and glucose utilization rates (GURs) were measured in control lambs, IUGR lambs and IUGR lambs treated with adrenergic receptor modifiers: clenbuterol atenolol and SR59230A (IUGR‐AR). In IUGR lambs, islet insulin content and GSIS were less than in controls; however, insulin sensitivity and whole‐body GUR were not different from controls. Of importance, ADRβ2 stimulation with β1/β3 inhibition increases both insulin sensitivity and whole‐body glucose utilization in IUGR lambs. In IUGR and IUGR‐AR lambs, hindlimb GURs were greater but fractional glucose oxidation rates and ex vivo skeletal muscle glucose oxidation rates were lower than controls. Glucose transporter 4 (GLUT4) was lower in IUGR and IUGR‐AR skeletal muscle than in controls but GLUT1 was greater in IUGR‐AR. ADRβ2, insulin receptor, glycogen content and citrate synthase activity were similar among groups. In IUGR and IUGR‐AR lambs heart rates were greater, which was independent of cardiac ADRβ1 activation. We conclude that targeted ADRβ2 stimulation improved whole‐body insulin sensitivity but minimally affected defects in GSIS and skeletal muscle glucose oxidation. We show that risk factors for developing diabetes are independent of postnatal catch‐up growth in IUGR lambs as early as 1 month of age and are inherent to the islets and myocytes.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 88%

Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle

Yates

Camacho

Kelly

et al. 2019

The Journal of Physiology

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“…This is consistent with a study where in a dry-tropical environment, Brahman calves that died during neonatal life were on average 6.1 kg lighter than those that survived (Muller, 2007). Yates et al (2012) reported in their review that heat stress on the cow during gestation may lead to placental insufficiency, restricted foetal nourishment and consequently the birth of low-birth-weight, low-vigour calves. Bull et al (1974) reported that for a herd of Bos taurus cows, those on low and high levels of protein during the last 60 days of gestation, the percentage of weak calves born was 15% and 0%, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…In northern Australian beef breeding herds, the effects of maternal nutrition during pregnancy (including epigenetic effect) on calf vigour are poorly understood. Yates et al (2012) reported in their review that heat stress on the cow during gestation may lead to placental insufficiency, restricted foetal nourishment and consequently the birth of lowbirth-weight, low-vigour calves. A study in Brahmans showed that the relative frequency of low birth vigour varied from 3.5% to 11.8% over a number of years, and that birth-vigour was affected by sequence of birth in the calving season, temperature at birth and the occurrence of precipitation at birth (Wythe, 1970).…”

Section: Calf Ability To Sucklementioning

confidence: 99%

Dehydration as a risk factor for calf mortality in northern Australia

Muller¹

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It is estimated that approximately one million calves die in Australia every year, with the majority unexplained. This thesis reviews losses associated with dehydration-mediated mortality during neonatal life, when there is highest risk of mortality, and reports three studies of neonatal calf dehydration.For 12 neonatal Brahman calves at Spyglass research site (northern forest land type, Queensland), variation in hydration status was investigated (Experiment 1). Change in live-weight from birth was used as the primary measure of hydration. Half of this cohort had low live weight gain between birth and day 3 of life (p = 0.01) compared to calves growing at 0.95±0.24 kg/day from birth. Low growth and associated reduced plasma protein (p = 0.04) in 6 calves indicated reduced colostrum, milk uptake and therefore reduced body fluid replenishment compared to other calves. This positions them at high risk of mortality under adverse environmental conditions. Urea space was tested as a measure of body water; however, percentage body water estimates were unrealistically elevated (> 80% of live weight) and therefore not representative of actual calf percentage body water.Descriptive analysis of risk factors for calf mortality was conducted for 478 and 378 tropically adapted newborn calves, respectively at Spyglass and Brian Pastures (southern forest land type, central Queensland) research sites (Experiment 2). The incidence risk of neonatal mortality in the southern forest of Queensland and northern forest of Queensland was 3.1% and 4.7%, respectively. Some risk factors and the percentage of calves exposed to high mortality risk included: dam body condition score ≤2 (8%), birth weight ≤28 kg (18%), low birth vigour (2%), large udder size (1%), at least two large teats (2%) and poor maternal protectiveness (5%). The low proportion of cows in poor body condition and good nutritional management limited the opportunity for dehydration-mediated neonatal mortality. There were no cases of prolonged heat stress around calving at the level previously associated with foetal and calf mortality. Experiment 2 indicates that low calf mortality may be achieved in any country type, provided that a low proportion of calves are exposed to high risk of mortality. A simple mechanistic model was developed to describe milk uptake volumes and ambient temperature (heat stress) impacts on neonatal hydration. This model provided clarification for the possible risk of dehydration mediated mortality across breeding herds of northern Australia.This thesis demonstrated variation in milk delivery, modelled that low milk delivery is associated with dehydration-mediated mortality and demonstrated that risk of mortality is low at a herd level when the risk factors associated with reduced milk delivery have low frequency.3

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“…Riley et al (2004) reported this trait to be heritable in Brahmans. Yates et al (2012) in their review suggested that heat stress may also cause this outcome, in association with reduction in birth weight. Fordyce et al (1993) previously showed that calf birth weight can be 25% lower in years with low pasture quality.…”

Section: Univariate Associationsmentioning

confidence: 99%

Risk factors affecting the reproductive outcome of beef breeding herds in North Australia

McCosker¹

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Approximately half of Australia's beef breeding herds are located in northern Australia with reproductive performance being identified as having a significant impact on the profitability of these businesses. Although many of the risk factors affecting the reproductive performance of beef cattle have been previously identified, the relative contribution of major risk factors to key measures of performance, after partitioning the effects of other confounding variables, is lacking, particularly for extensive tropical rangeland systems typical of northern Australia.The overall objective of the research described in this thesis was to, i) describe the reproductive performance of commercial beef breeding cattle in northern Australia and, ii) determine, and quantify the effect of the major risk factors associated with three key measures of reproductive performance (lactating cows becoming pregnant within 4 months of calving, cows failing to become pregnant within an approximate 12 month reproductive cycle, and foetal/calf loss between confirmed pregnancy and weaning). It was hypothesised that the major risk factors determining the probability of lactating cows becoming pregnant within four months of calving are similar to those determining the probability of foetal/calf loss between confirmed pregnancy and weaning. To address these objectives, a prospective population-based epidemiological study was conducted between 2007 and 2011 involving 78 commercial beef properties located across northern Australia.Attainable and typical levels of reproductive performance for cow-age cohorts were described using a dataset containing 114,154 annual production cycles of performance data that represented approximately 78,000 heifers and cows managed in 142 breeding groups. Properties were assigned to one of four broad country types following a subjective assessment of the production potential of the grazing land and cross-referencing with pasture and vegetation descriptions reported by the herd owners/managers.The typical overall reproductive performance of cows in the Northern Forest (57 live calves at muster per 100 surviving mature cows), was considerably lower than that for the other country types (71-83 live calves at muster per 100 surviving mature cows). This was due to typically much lower percentage of cows becoming pregnant within 4 months of calving, higher foetal and calf loss and higher estimated mortality of pregnant cows in the Northern Forest compared to the other genotypes. These findings are consistent with the generally poorer quantity and quality of pasture, ii harsher environment and higher disease risk of cattle managed in the Northern Forest compared to the other country types.Country type and predicted calving period were top-order determinants of pregnancy within 4 months of calving while lactating. The effect of cow-age class cohort was dependent on country type with the expected occurrence of lactating cows pregnant within 4 months of calving estimated to be 23. 1-53.8, 38.1-61.6, 35.4-56.5 and 38.5...

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Environmental Heat Stress Impairs Placental Function, Fetal Growth and Development, and Postnatal Performance in Livestock

Cited by 7 publications

References 101 publications

Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle

Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle

Dehydration as a risk factor for calf mortality in northern Australia

Risk factors affecting the reproductive outcome of beef breeding herds in North Australia

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