Serina Hancock

In ruminants, water ingestion causes an immediate and measurable decline in rumen temperature. While this physiological response is well established, its application for estimating water intake has not previously been investigated. This study assessed the suitability of a thermodynamic modelling approach to predict water intake in sheep using intra-ruminal temperature data. A fluid calorimetry equation was first validated under controlled laboratory conditions, then applied to data from six sheep fitted with intra-ruminal temperature loggers. Animals were offered water of known volume and temperature, and intake predictions were calculated using the temperature drop, baseline rumen temperature, water temperature, and estimated rumen volume based on liveweight. To improve volume estimation, additional rumen volume and liveweight data from a separate group were used to generate a generalised prediction equation for rumen volume. The approach underestimated the volume of water consumed, and so we developed a correction factor to account for physiological variation in the effective rumen volume at the time of drinking. Using the effective rumen volume in calculations resulted in predicted intake volumes that generally aligned with the measured values (P < 0.01). Our results demonstrate that measured changes in intra-ruminal temperature can be used to estimate water intake, offering a promising tool for precision livestock monitoring in extensive grazing systems.

Mating ewes to lamb at 12 months of age can enhance lifetime productivity but is associated with lower reproductive performance and lamb survival compared to mature ewes. Melatonin, an antioxidant, has been shown to improve placental function and lamb health when mature ewes were supplemented during pregnancy. This study investigated the effect of supplementing one-year-old ewes with melatonin during mid-pregnancy on their survival and the live weight and survival of their lambs. Single- (n = 2711) and twin-bearing (n = 2605) ewes were randomly assigned to Melatonin or Control groups at seven farms across southern Australia. The Melatonin group received an 18 mg implant of melatonin at 90–100 days after the introduction of the rams, which releases melatonin for 60–80 days, and the Control group were not supplemented with melatonin. Seven farms recorded paddock level information including fetal number, lambs present 200 days after the introduction of the rams, ewes present pre-lambing and 200 days after the introduction of the rams and ewe pre-lambing live weight. Lamb survival and ewe mortality were analysed with analysis of covariance. Three of the seven farms also collected individual lambs’ information (n = 4303 lambs) including weight at birth and weaning of lambs, date of birth and weaning, lamb sex and birth type. Individual lamb live weights and growth rate to weaning were analysed with linear mixed models. Supplementation with melatonin had no effect (P > 0.05) on ewe or lamb survival. Melatonin supplementation did not impact (P > 0.05) individual lamb birthweight, growth rate, or weaning weight, consistent with the observed results in lamb survival. These findings suggest that maternal supplementation with melatonin mid-pregnancy is not an effective strategy to improve the survival or early growth of lambs, or the survival of one-year-old ewes.

Context
In the south-west of Western Australia, weaned lambs typically graze dry annual pastures and crop stubbles during late spring, summer and autumn (October–March). The low energy and protein content of these feeds typically means that lambs are supplemented with concentrates to achieve target growth rates. Fully mature, standing lupin crops that could be harvested may provide higher quality feed than dry pasture and crop stubbles over this period.

Aims
This study tested the hypothesis that the incorporation of standing lupin crops for grazing will increase whole-farm profitability. Furthermore, we aimed to quantify the relative contributions of stocking rate, sale value of lambs, weaner survival rate and ewe lamb reproduction to this increase in farm profit.

Methods
Whole-farm bioeconomic modelling was used to assess the profitability of grazing standing lupin crops in a mixed farming system. An analysis was conducted for a representative mixed farm in south-west Western Australia with a self-replacing Merino flock, and the profitability of grazing a lupin crop was assessed on the basis of whether it was harvested or grazed. A sensitivity analysis was then carried out to test the robustness of the results and understand the role of standing lupin crops in a mixed farming system.

Key results
Grazing lupins grown on 7% of the total farm area increased whole-farm profitability by almost A$30,000 or A$200/ha of standing crop. In this environment, across a range of assumed crop yields and prices, it was always more profitable to graze standing lupins rather than harvest the lupins. The increase in profit was primarily due to an increase in stocking rate of 1.2 dry sheep equivalent per hectare when able to graze the optimum area of standing lupins compared to when there was no standing crop. In addition to the increase in stocking rate, revenue from sheep sales increased, with the Merino wether and mixed sex crossbred weaners sold for an extra A$13 per lamb when stocking rate was constrained to the optimum for when there was no standing lupin crop.

Conclusions
This analysis demonstrated that in the south-west of Western Australia, grazing standing lupin crops was always more profitable than harvesting the grain.

Implications
If lupins are included in crop rotations in this environment, profit will be increased if they are grazed, but it is also clear that stocking rate should be increased to fully capitalise on potential gains in farm profit.

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 individual 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.

Shade and shelter may provide protection from cold and heat stress, a source of feed during prolonged or seasonal drought, specific essential nutrients, increased pasture and crop production and improved landscape health. Cold stress contributes to the average of 8% (single) and 24% (twin) of lambs that die within 3 days of birth in Australia and the estimated 0.7% of the Australian flock that die post-shearing during extreme or unseasonal weather. Shelter has resulted in an average reduction in mortality of 17.5% for twin-born lambs and 7% for single-born lambs according to Australian studies and decreases the susceptibility of ewes to metabolic disease and possibly dystocia. Because many of the published studies are from research areas where cold stress is expected, they are not indicative of industry-wide responses, a research priority is to determine the probability of lamb and ewe deaths from cold stress across different sheep production areas. Although shelter may improve lamb survival, ewes do not always choose to lamb in a sheltered location. For this reason, there is a requirement for research into the voluntary use of shelter in commercial-sized paddocks and the role that nutritive value of shelter plays in attracting and holding ewes to shelter, and to their lambs. Heat stress may also result in lamb deaths and influences feed conversion efficiency, appetite, reproduction, wool growth and disease susceptibility. The consequences of heat stress may go unnoticed over a yearly production cycle, although there is some evidence that shade may increase weaning rates and feed intake of grazing sheep. There are ancillary benefits from shade and shelter. Trees may improve crop production through reducing wind damage and evapotranspiration and provide timber. Shrubs provide feed during the summer-autumn feed gap or drought, are useful for the management of land degradation and provide habitat for native fauna. It is clear that shade and shelter in the correct locations provide a range of benefits to livestock and the landscape; nevertheless, adoption appears low. Research that focuses on defining the benefits on a farm or landscape scale is required to support extension programs.

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.

Context: Clinical deficiencies of calcium and magnesium may result in the metabolic disorders hypocalcaemia and hypomagnesaemia, resulting in ewe and lamb mortality. However, the contribution of subclinical deficiencies to perinatal lamb mortality in grazing flocks is unclear.

Aims: To test the hypothesis that calcium and magnesium supplementation during the lambing period would increase lamb survival to marking age.

Methods: In 2017, an on-farm study used five flocks across New South Wales, South Australia and Western Australia. On each farm, twin-bearing mature Merino ewes (n = 400–600) grazing pasture were allocated to two replicates of control and supplemented treatments. The supplemented groups were offered 30 g/ewe per day of a loose lick containing magnesium chloride (MgCl2(H2O)6), calcium sulfate (CaSO4·(H2O)2, and salt (NaCl), in the ratio 12.5:32.5:55.0, designed to have a low dietary cation–anion difference (−390 meq/100 g). A second study was conducted in 2018 on one farm to test the form of supplement. This study used two replicates of three treatments: control; a low-dietary cation–anion difference supplement as used in 2017; and a standard lime, Causmag (calcined MgO) and salt loose mix (ratio 1:1:1). Mature twin-bearing composite ewes (n = 600) were allocated to groups and those supplemented were offered minerals for the last month of pregnancy and during the lambing period. Blood and urine samples were collected in both experiments for analyses of mineral concentrations.

Key results: In the 2017 study, only two flocks consumed >10 g/ewe of supplement per day, and supplementation did not increase lamb survival to marking age in these flocks. In the 2018 study, the mean consumption of supplement was 18 or 20 g/ewe per day. Of non-supplemented ewes, 61% were deficient in plasma calcium (≤90 mg/L) and 17% were deficient in magnesium (≤18 mg/L) at Day 140 after the start of joining. Lamb survival was not increased by supplementation and was 77 ± 3.8% in both treatments.

Conclusions: Calcium and magnesium supplementation did not increase lamb survival.

Implications: Lamb survival was not increased by calcium and magnesium supplementation; however, evaluation under a wider range of grazing conditions with adequate supplement intake is required.

This case-control study investigated associations between Campylobacter fetus or Campylobacter jejuni titre and reproductive outcomes in 22 flocks of Merino and non-Merino maiden ewes aged 1–2 years old. Campylobacter titres were also determined for multiparous ewes aged 3 years or older on the same farms. C. fetus ‘positivity’ (titre ≥1:80) was detected for 12% (57/462; 95% confidence interval [95% CI] 9.6 to 15.6) of maiden ewes and 31% (65/210; 95% CI 25.0 to 37.4) of mature ewes. The odds for failing to rear a lamb in C. fetus-‘exposed’ maiden ewes (titre ≥1:10) was 2.01 times that of seronegative ewes (95% CI 1.09 to 3.77; P = 0.027), but there was no association between C. fetus-‘positivity’ (titre ≥1:80) and failure to rise (OR 1.69; 95% CI 0.77 to 3.76; P = 0.191). C. fetus abortions were confirmed with microbial culture in one maiden ewe flock. In this flock, C. fetus titres fluctuated and often waned by lamb marking, highlighting the value of necropsies during abortion investigations. C. jejuni-‘positivity’ (titre ≥1:80) was detected for 44% (204/462; 95% CI 39.7 to 48.7) maiden ewes, but odds of failing to rear were decreased for C. jejuni-‘positive’ ewes (OR 0.52; 95% CI 0.32 to 0.83; P = 0.007). The association between Campylobacter serology and the reproductive outcome was inconsistent in these flocks. Serology should be considered in the context of other risk factors and used in conjunction with other strategies to investigate the impact of Campylobacter exposure on ewe reproductive performance such as monitoring for abortions and lamb necropsies to determine aetiological diagnosis, and vaccination trials.

The role of infectious diseases including coxiellosis in causing poorer reproductive performance of primiparous ewes are not well studied. The aims of this study were to determine if natural exposure to Coxiella burnetii is widespread in breeding ewes and whether seropositivity is associated with poor reproductive performance of primiparous ewes. Seropositivity to Coxiella burnetii was 0.08% (CI95% 0.01, 0.36) in primiparous ewes and 0.36% (CI95% 0.07, 1.14) in mature ewes. Coxiella burnetii was not detected in aborted or stillborn lambs using qPCR. These findings suggest C. burnetii infection was unlikely to be an important contributor to abortion and perinatal mortalities observed for primiparous ewe flocks, and exposure to C. burnetii was not widespread in ewes on farms located over wide geographical region of southern Australia. Whilst ewes on these farms were not an important reservoir for C. burnetii, sporadic zoonotic transmission from sheep is reported and has public health implications.

Background Toxoplasma gondii causes reproductive losses in sheep worldwide, including Australia. The reproductive performance of primiparous ewes is typically lower than for mature, multiparous ewes, and younger ewes are more likely to be immunologically naïve and therefore more susceptible to reproductive disease if T. gondii infection occurs during pregnancy. The aim of this study was to assess the impact of infection with T. gondii on the reproductive performance of primiparous ewes in southern Australia using a prospective cohort study. This will inform the need for targeted control strategies for T. gondii in Australian sheep. Results Toxoplasma gondii seropositivity using indirect ELISA was detected at 16/28 farms located across southern Australia. Apparent seropositivity to T. gondii was lower in primiparous ewes (1.1, 95% confidence interval (CI) 0.6, 1.8) compared to mature, multiparous ewes (8.1, 95% CI 6.0, 10.5; P < 0.001). Toxoplasma gondii seroconversion during the gestation and lambing period was confirmed for 11/1097 (1.0, 95% CI 0.5, 1.7) of pregnant primiparous ewes that failed to raise a lamb, and 1/161 (0.6, 95% CI 0.1, 2.9) primiparous ewes with confirmed mid-pregnancy abortion. Conclusions Low frequency of detection of T. gondii seroconversion during gestation and low frequency of seropositivity to T. gondii suggests that toxoplasmosis was not an important contributor to reproductive losses in primiparous ewes on farms located over a wide geographical area in southern Australia.