ORCID Profile
0000-0002-4115-4642
Current Organisation
Murdoch University
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Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AN15085
Abstract: Functional deficiencies of the immune system are known to predispose human and animal neonates to death. Thus, immune competency may be a significant factor influencing the mortality of lambs. Vitamin D has been recognised to improve immune function and is transferred across the placenta. This study tested the hypotheses that (1) supplementation of Merino ewes with cholecalciferol during late pregnancy will increase the concentrations of vitamin D in the ewe and lamb at birth and (2) supplementation of Merino ewes with cholecalciferol during late pregnancy is correlated with an increase in innate phagocytic and adaptive antibody immune responses in the lamb. Merino ewes (n = 53) were injected intramuscularly with 1 × 106 IU cholecalciferol at Days 113 and 141 of pregnancy. A control group (n = 58) consisted of ewes receiving no additional nutritional treatments. The vitamin D status of ewes and lambs was assessed up until 1 month post-lambing. Lamb immune function was assessed by analysing the functional capacity of phagocytes, and the plasma IgG and anti-tetanus-toxoid antibody concentrations between birth and weaning. Maternal supplementation with cholecalciferol increased the plasma 25(OH)D concentrations of both ewes (137 vs 79 nmol/L P 0.001) and lambs (49 vs 24 nmol/L P 0.001) at birth compared with the controls. Supplementation with cholecalciferol had no significant effect on the phagocytic capacity of monocytes or polymorphonuclear leukocytes, the concentration of IgG in the colostrum or plasma of lambs, or the vaccine-specific antibody response against tetanus toxoid. Overall, the results support our first hypothesis, but suggest that maternal supplementation with 1 × 106 IU cholecalciferol does not improve innate, passive or adaptive immune function in lambs.
Publisher: Informa UK Limited
Date: 27-07-2016
Publisher: Springer Science and Business Media LLC
Date: 11-06-2021
DOI: 10.1186/S13567-021-00950-W
Abstract: Lamb survival is an important welfare and productivity issue for sheep industries worldwide. Lower lamb survival has been reported for primiparous ewes, but the causes of this are not well studied. The aim of this study was to determine causes of perinatal deaths for lambs born to primiparous ewes in Western Australia, and identify if infectious diseases are implicated. Lamb mortality from birth to marking were determined for 11 primiparous ewe flocks on 10 farms in Western Australia. Lamb mortality from birth to marking averaged 14% for single-born and 26% for multiple-born lambs. Lamb necropsies ( n = 298) identified starvation–mismosthering–exposure (34%), dystocia (24%) and stillbirth (15%) as the most common causes of perinatal lamb death. There was no evidence of exotic abortigenic pathogens in aborted and stillborn lambs ( n = 35). Chlamydia pecorum was detected by qPCR in 15/35 aborted and stillborn lambs on 5/6 farms. Preliminary molecular characterisation of C. pecorum detected in s les from aborted and stillborn lambs ( n = 8) using both Multilocus Sequence Typing and omp A genotyping indicated all strains were genetically identical to previously described pathogenic livestock strains, denoted ST23, and dissimilar to gastrointestinal strains. High frequency of detection of a pathogenic C. pecorum strains ST23 associated with ovine abortion and stillbirth on multiple farms located across a wide geographic area has not been previously reported. Chlamydia pecorum may contribute to reproductive wastage for primiparous sheep in Western Australia. Further investigation to understand C. pecorum epidemiology and impact on sheep reproduction is warranted.
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/AN17403
Abstract: Grazing vegetative wheat, barley and oats (both dual-purpose and traditional spring varieties) is becoming an important strategic and tactical grazing option on farms where crops and livestock coexist. However, metabolic disorders have been reported and many producers avoid grazing these crops with reproducing ewes because of the risk. A recent survey of 18 farms grazing crops with pregnant ewes indicated a high proportion of grazed crops had forage calcium (Ca), sodium (Na) and magnesium (Mg) below published requirements and potassium (K) above the published maximum tolerable level. Many ewes grazing these crops had concentrations of Ca in plasma and urine indicative of a low or marginal Ca status. The aims of the present study were to further investigate the changes in mineral status that occur in ewes grazing vegetative crops during late pregnancy and to measure the effectiveness of mineral supplements for improving Ca and Mg status. On each of six farms, a paddock growing cereals in the vegetative stage was sub ided into three plots. Three groups of 30 pregnant ewes were selected and each group allocated to one plot. Forage was provided as wheat on four farms, barley on one farm and oats on one farm. Ewes were mature (3–7 years), in the last third of pregnancy (between 108 and 129 days after the start of mating) and were mostly twin-bearing. They grazed the crops for 21 days. One group of ewes was given no supplement (Control), a second was provided with an industry standard supplement (Standard) [Causmag (MgO):limestone (CaCO3):salt (NaCl), 40:40:20] at 30 g/day, whereas the third group was provided with a low dietary cation-anion difference (DCAD) supplement (New) (MgCl2.6H2O:CaSO4.2H2O:NaCl, 12.5:32.5:55.0) also at 30 g/day. Both Ca supplements improved Ca and, to a lesser extent, Mg status. The supplemented ewes showed significant increases in Ca concentration in urine, plasma and Ca fractional excretion on all but one of the six farms. There were no consistent differences between the two supplemented groups of ewes. It is concluded that the Ca status of ewes grazing vegetative cereal crops in late pregnancy can be improved by providing supplements containing Ca, Mg and Na. As the literature indicates the relationship between Ca status and susceptibility to hypocalcaemia is still inconclusive, additional research on a commercial scale is required to determine if supplements decrease the incidence of metabolic disorders when pregnant ewes graze cereal crops.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AN17766
Abstract: During pregnancy, ewes graze pastures that may be marginal in calcium (Ca) and magnesium (Mg), and may also be low in sodium (Na) and high in potassium (K), with a high dietary cation–anion difference. Such pastures may increase susceptibility to hypocalcaemia and hypomagnesaemia, leading to lamb losses. Clinical hypocalcaemia and hypomagnesaemia do occur in Australian sheep however, it is unknown whether subclinical forms of these disorders compromise ewe or lamb health and survival. The present study monitored the Ca and Mg status of ewes in late pregnancy, so as to evaluate the risk of subclinical mineral disorders in ewes grazing typical southern Australian pastures. Calcium and Mg concentrations in pasture, ewe plasma and urine were monitored in 15 flocks in southern Australia. Mineral concentrations in pasture did not indicate a widespread risk of Ca or Mg deficiency however, urinary pH and Ca and Mg concentrations in the plasma and urine of the pregnant ewes were not entirely consistent with the expectations from pasture analysis. Urine pH was above 7 on all properties and 87.5% of properties had a mean Ca in urine below the adequate concentration of 1 µmol/mosmol. The mean plasma Ca concentration was below adequate ( mg/L) on only one farm but five farms had more than 20% of ewes with below adequate Ca in plasma. In addition, although average farm concentrations of plasma and urine Mg indicated adequate Mg status of the ewes ( mg/L), more than 20% of ewes on six farms had below adequate concentrations of plasma Mg. Only one-third of the farms had 100% of ewes measured with adequate concentrations of plasma Ca (4/15) or Mg (5/15). The mineral concentrations in pre-lambing blood and urine s les suggested that a significant number of animals grazing southern Australian pastures during winter may be at risk of subclinical hypocalcaemia and hypomagnesaemia.
Publisher: Elsevier BV
Date: 09-2007
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AN16530
Abstract: Grazing vegetative wheat, barley and oats (both dual-purpose and traditional spring varieties) is becoming an important strategic and tactical grazing option on farms where crops and livestock co-exist. The high winter growth rates of the crops offer an opportunity to fill the winter feed gap and the high nutritive value (metabolisable energy and crude protein) makes them well suited to meet the requirements of reproducing ewes. However, metabolic disorders have been reported and many producers avoid grazing these crops with reproducing ewes because of the risk. The present study aimed to establish the mineral status of both forage and of reproducing ewes grazing wheat, oats or barley. On each of 18 farms, a group of 50 pregnant ewes was monitored. The farms were located in Western Australia (6 farms) southern New South Wales (7 farms) and central New South Wales (5 farms). The average start of grazing was 118 days (range 97–133 days) after the start of mating. Crops grazed were wheat (8 farms), barley (4 farms) or oats (6 farms) and the average period of grazing was 20 days (range 14–24 days). S les of blood and urine were collected pre- and post-grazing from 11 to 17 ewes and s les of crop and soils were also collected for mineral analysis. A high proportion of farms had forage calcium (Ca, 70%), sodium (Na, 70%) and magnesium (Mg, 18%) below published requirements and potassium (K, 70%) above the published maximum tolerable level. Strong negative correlations were found between soil Colwell K and forage Ca, Mg and Na. Analysis of s les collected from the ewes at the end of the grazing period indicated that ewes on 94% of farms had alkaline urine and on 88% of farms Ca concentrations in the urine were in the marginal range. None of the flock-average Ca concentrations in plasma was in the deficient range, but 59% of the flocks contained some in idual ewes with plasma Ca in the deficient range. A small proportion of flock-average concentrations of Mg (6%) and Na (18%) in plasma were in the deficient range. In conclusion, the forages had a complex mineral composition meaning that grazing ewes may have an increased risk of direct or induced Ca (hypocalcaemia) or Mg (hypomagnesaemia) deficiency. The low Na and high K concentrations of these crops may also pose a direct risk to livestock production. Preliminary analysis indicated higher risks from grazing wheat and from grazing crops grown on high-K soils.
Publisher: Elsevier BV
Date: 03-2022
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/AN17588
Abstract: High lamb mortality continues to be a significant economic and welfare problem within the Australian sheep industry, with 20–30% of lambs born in commercial flocks dying mostly within 3 days of birth. Clinical hypocalcaemia and hypomagnesaemia cause ewe mortality, and, subsequently, either fetal or lamb death, but it is not known whether subclinical deficiencies of calcium (Ca) and magnesium (Mg) compromise lamb survival. This review considers the potential mechanisms through which Ca and Mg deficiencies may influence lamb survival, and factors influencing the risk of deficiency. Pastures grazed by lambing ewes may be marginal in calcium (Ca & g/kg DM) and magnesium (Mg & .9 g/kg DM) but also have a high dietary cation–anion difference (& meq/100 g DM) and high concentrations of potassium (K & g/kg DM) and nitrogen. In young cereal crops, sodium concentrations are also often low (& .9 g/kg DM). This combination of minerals and other nutrients creates an imbalance in supply and increases susceptibility to acute Ca (hypocalcaemia) and Mg (hypomagnesaemia) deficiency. Calcium is required for smooth muscle function and has a direct role in uterine contraction, so may influence the duration of parturition. Low Ca and Mg intake both influence insulin release and sensitivity, low Mg results in poor glycaemic control and insulin resistance by impairing both insulin secretion and its action on peripheral tissues, also potentially altering the duration of parturition as well as risk of metabolic disease. Magnesium is also a neuroprotectant that slows the neuronal damage during hypoxia and has been linked with thermogenesis in offspring and increased immunoglobulins in colostrum. These functions indicate potential importance in improving the ease of parturition and improved ability of the newborn lamb to thermoregulate and survive after birth. Subclinical Ca and Mg deficiencies commonly occur in 20% of lambing ewes grazing temperate pastures, so further studies are warranted to investigate whether correction of these deficiencies can improve lamb survival.
Publisher: Springer Science and Business Media LLC
Date: 06-2017
Abstract: Twins are often born small and early and have increased risk of obesity and diabetes later in life. Twin conception in sheep, regardless of whether the pregnancy continues as twins or is reduced to singleton in early gestation, alters offspring growth trajectory and body composition in young adulthood. We hypothesized that twin conception would result in insulin resistance in adulthood, with insulin-resistant adipose tissue and skeletal muscle phenotypes. At 3 years of age, body weight was not different among singletons, twins, and reductions females weighed less than males. Singletons were leaner than reductions, with twins intermediate. Twins and reductions had decreased insulin sensitivity compared with singletons (singletons: mean [standard error of the mean]: 4.75 [0.4], twins: 3.34 [0.3], reductions: 3.67 [0.2] mg·I μU
Publisher: Elsevier BV
Date: 2008
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 2010
Publisher: MDPI AG
Date: 09-06-2012
DOI: 10.3390/ANI13121936
Abstract: Industry consultation in Australia revealed that the potential impact of the mob size of ewes during lambing on the survival of triplet-born lambs was an important research priority. Previous research has demonstrated that smaller mob sizes at lambing improve the survival of single- and especially twin-born lambs, regardless of ewe stocking rate. Therefore, we hypothesised that lambing triplet-bearing ewes in smaller mobs, regardless of stocking rate, will increase the survival of their lambs. Research sites were established on 12 commercial sheep farms across southern Australia between 2019 and 2021. One farm used Merinos whilst the remainder of the farms used non-Merino breeds, consisting of composite ewes joined to composite or terminal sires. Three of the farms were used in two years of the experiment. Adult, triplet-bearing ewes were randomly allocated into one of two treatments, ‘High’ or ‘Low’ mob size, at an average of 135 days from the start of joining. Ewe and lamb survival were assessed between allocation to treatments and lamb marking. Lamb survival was significantly greater for lambs born in the Low (65.6%) compared with the High (56.6%) mob size treatments (p 0.001). There was no effect of mob size at lambing on the mortality of triplet-bearing ewes. Analysis of the effect of the actual mob sizes showed that reducing the mob size at lambing by 10 triplet-bearing ewes increased the survival of their lambs to marking by 1.5% (p 0.001). This study has shown that the survival of triplet-born lambs can be improved by lambing triplet-bearing ewes in smaller mobs regardless of stocking rate when ranging from 0.7–13 ewes/ha.
Publisher: Wiley
Date: 03-2012
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 2011
Publisher: MDPI AG
Date: 21-12-2021
DOI: 10.3390/ANI12010010
Abstract: The contribution of abortions to the overall mortality of lambs born to maiden (primiparous) ewes in Australia remains unclear. This cohort study aimed to quantify abortion and lamb mortality for ewe lambs and maiden Merino two-tooth ewes. Lamb mortality from pregnancy scanning to marking were determined for 19 ewe lamb and 11 Merino two-tooth ewe flocks across southern Australia. Average lamb mortality from scanning to marking was 35.8% (range 14.3–71.1%) for the ewe lambs and 29.4% (range 19.7–52.7%) for the two-tooth ewes. Mid-pregnancy abortion was detected in 5.7% of ewes (range 0–50%) in the ewe lamb flocks and 0.9% of ewes (range 0–4.4%) in the two-tooth ewe flocks. Mid-pregnancy abortion affecting ≥2% of ewes was observed in 6/19 ewe lamb flocks and 2/11 two-tooth ewe flocks. Lamb mortality from birth to marking represented the greatest contributor to foetal and lamb mortality after scanning, but mid-pregnancy abortion was an important contributor to lamb mortality in some ewe lamb flocks. Variability between the flocks indicates scope to improve the overall reproductive performance for maiden ewes by reducing foetal and lamb losses. Addressing mid-pregnancy abortion may improve the reproductive performance in some flocks.
Publisher: Elsevier BV
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 08-2011
Publisher: MDPI AG
Date: 18-02-2022
DOI: 10.3390/ANI12040513
Abstract: Suboptimal reproductive performance of maiden (primiparous) ewes remains a source of inefficiency for the Australian sheep industry. However, the extent and causes of the poorer reproductive performance of maiden ewes on Australian sheep farms are not well understood. Here, we show the reproductive performance of maiden ewes relative to their multiparous counterparts on the same farms across Australia using a cohort survey. The difference in marking rate for non-Merino maiden ewe lambs compared to multiparous ewes was 58% (74 vs. 132% p 0.001), and this was attributable to a 50% difference in reproductive rate (109 vs. 159% p 0.001) and 16% difference in lamb survival to marking (67 vs. 83% p 0.001). The difference in marking rate for maiden Merino two-tooth ewes lambing at approximately 2 years-of-age compared to mature multiparous ewes was 22% (80 vs. 102% p 0.001) and this was attributable to a 24% difference in reproductive rate (108 vs. 132% p 0.001) and 3% difference for lamb survival (75 vs. 78% p 0.05). Positive correlations for reproduction traits (reproductive rate, lamb survival and marking rate) between maidens and multiparous ewes were observed for maiden Merino two-tooth ewes (p 0.001), but these correlations were weak or non-existent for non-Merino ewe lambs. Strategies to improve both reproductive rate and lamb survival can address the poorer and more variable reproductive performance of maiden ewes.
Publisher: Wiley
Date: 03-11-2020
DOI: 10.1111/AVJ.13038
Publisher: Elsevier BV
Date: 06-2010
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/AN19632
Abstract: Context Data collected from producers in south-eastern Australia found that the survival of twin-born lambs decreased by 3.5% for each extra 100 ewes in the mob at lambing. Increasing stocking rate by 1 ewe/ha decreased lamb survival by a further 0.7%. These survey findings suggest that lamb survival could be improved by optimising the allocation of ewes to mobs and paddocks at lambing. Aim The present paper reports two experiments. Experiment 1 tested the hypotheses that (1) the survival of twin-born lambs would be greater when ewes lamb in smaller mobs and at lower stocking rates, and (2) the effects of mob size and stocking rate would be greater in Merinos than in non-Merino breeds. Experiment 2 tested the hypothesis that the survival of twin-born Merino lambs would be greater at lower mob sizes when ewes lambed at stocking rates & ewes/ha. Methods Experiment 1 investigated a 2 × 2 factorial combination of mob size (high or low) and stocking rate (high or low) on the survival of twin-born Merino and non-Merino lambs at 70 on-farm research sites across southern Australia. Experiment 2 investigated the effect of high or low mob size on the survival of twin-born Merino lambs when ewes lambed at stocking rates of & twin ewes/ha at 15 on-farm research sites. In both experiments, adult twin-bearing ewes were randomly allocated into a treatment and lambing paddock on Day 140 from the start of joining at each farm. Lamb survival in each mob was calculated based on lamb losses between pregnancy scanning and lamb marking. Key results In both experiments, the effect of mob size on lamb survival was found to be linear, with survival of twin-born lambs decreasing by between 1.9% and 2.5% per additional 100 ewes in the mob at lambing, regardless of breed (P & 0.001). In Experiment 1, there was no effect of stocking rate or mob size by stocking rate on lamb survival. Conclusions The present research demonstrated that reducing mob size but not stocking rate will improve the survival of twin-born lambs to marking for extensive enterprises in Australia where ewes lamb at stocking rates of up to 12 ewes/ha. Implications These findings will contribute to guidelines for optimising ewe nutrition and resource allocation to improve lamb survival.
Publisher: Informa UK Limited
Date: 03-02-2019
Publisher: MDPI AG
Date: 22-06-2018
DOI: 10.3390/ANI13132057
Abstract: This study evaluated the impacts of management of body condition score (BCS) between pregnancy scanning and lamb marking on the mortality of triplet-bearing ewes and their lambs at 19 research sites across Southern Australia. Triplet-bearing ewes of Maternal (crossbred or composite) or Merino breed were randomly allocated to treatment at pregnancy scanning at an average of 97 days from the start of joining: High or Low BCS. The BCS of in idual ewes was assessed at pregnancy scanning, pre-lambing (average of 137 days from the start of joining) and marking (average of 165 days from the end of joining), and ewe and lamb mortality to marking, recorded for each mob. The average BCS at pregnancy scanning was 3.4 for Maternal ewes and 3.3 for Merino ewes. There were no breed by BCS treatment effects on the BCS of ewes at pregnancy scanning or lamb marking or on the change in BCS between pregnancy scanning and pre-lambing or between pre-lambing and marking. The change in BCS differed between the High and Low BCS treatments, between pregnancy scanning and pre-lambing (0.12 vs. −0.33 p 0.001) and between pre-lambing and marking (−0.39 vs. 0.07 p 0.001) but did not differ between breeds. The average BCS at marking for ewes managed at the High and Low BCS treatments was 3.1 and 3.0 for Maternals and 3.0 and 2.8 for Merinos. Survival of triplet-bearing Merino ewes (p 0.01) and their lambs (p 0.001) was greater when ewes were managed at the High BCS compared to the Low BCS. The BCS treatment did not impact the survival of Maternal ewes or their lambs. The survival of Merino but not Maternal lambs was higher when ewes were in greater BCS pre-lambing (p 0.01) and when ewes gained BCS between pregnancy scanning and pre-lambing (p 0.01). Ewe mortality was lower when ewes gained BCS between pregnancy scanning and pre-lambing (p 0.05). Merino ewes were more likely to die than Maternal ewes for a given change in BCS between pregnancy scanning and pre-lambing (p = 0.065). Overall, our findings demonstrate that producers should manage the nutrition of triplet-bearing Merino ewes so that ewes are in greater BCS at lambing and/or to gain BCS between pregnancy scanning and lambing to improve ewe and lamb survival. Triplet-bearing Maternal ewes should be managed to gain BCS between pregnancy scanning and lambing to improve ewe survival.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 2019
Publisher: Cambridge University Press (CUP)
Date: 11-2009
No related grants have been discovered for Serina Hancock.