Reproductive Performance of Triplet-Bearing Ewes on Commercial Farms and Research Priorities Identified by Sheep Producers to Improve the Survival of Triplet-Bearing Ewes and Their Lambs

Consultation with sheep producers was used to quantify the mortality of triplet-bearing ewes and their lambs, identify management practices adopted by producers to reduce these losses and prioritise future research needs to improve the survival of triplet-bearing ewes and their lambs. Surveys were completed by 64 producers across Australia who identified and separated triplet-bearing ewes from twin-bearing ewes in 2017 and/or 2018. On average, 5.9% of all ewes mated were identified as carrying triplets (6.6% of non-Merino ewes and 2.9% of Merino ewes). The average mortality of triplet-bearing ewes was 6.4%, and ewe mortality did not differ significantly between ewe breeds. The average survival of triplet-born lambs was 59%, and survival was significantly higher for lambs from non-Merino compared to Merino ewes (60.1 vs. 52.9%, p < 0.05). The key strategies adopted to reduce the mortality of triplet-bearing ewes and their lambs included management of condition score, feed-on-offer, mob size at lambing and use of shelter. There were no differences (p > 0.05) in the average mortality of triplet-bearing ewes or their lambs between producers that prioritised the adoption of certain management practices. However, significant variation existed between producers in their targets at lambing for ewe condition score (2.8 to 3.5), mob size (10 to 150 ewes) and feed-on-offer (800 to 2500 kg dry matter/ha). Overwhelmingly, the highest priorities for further research identified by producers from surveys, workshops and a webinar were ewe condition score, mob size, feed-on-offer at lambing and mineral supplementation. This study informs benchmarks for mortality of triplet-bearing ewes and their lambs under extensive grazing conditions in Australia, and the priorities for future research to reduce these losses.

Supplementary Feed Additives Can Improve Lamb Performance in Terms of Birth Weight, Body Size, and Survival Rate

To evaluate the effects of supplementation of feed additives in the last trimester of pregnancy on placental characteristics and offspring performance, this study was conducted with 48 estrous-synchronized Ghezel ewes that had randomly been assigned to one of the following six groups (n = 8): ad libitum feeding (AL); feed restriction (RF; 60% of ad libitum intake); feed restriction + propylene glycol (PG); feed restriction + propylene glycol + monensin sodium (MS); feed restriction + propylene glycol + rumen-protected choline chloride (RPC); feed restriction + propylene glycol + monensin sodium + rumen-protected choline chloride (PMC). Birth weight, body size, and rectal temperature of lambs were determined within 24 h of birth. The presence of lambs at 87 days of age was used as an index of survival to weaning. The outcome of this study was that the average placental weight of ewes in the AL and MS groups was the highest and lowest, respectively, among the treatment groups (p < 0.01). RPC ewes presented higher placental efficiency compared to AL, RF, and MS ewes (p < 0.05). The largest and smallest crown-to-rump lengths (CRLs) were observed in PMC and RF lambs, respectively (p < 0.01). In addition, lambs born from PMC, RPC, and PG ewes had a longer curved crown-to-rump length (CCRL) than those born from AL and RF ewes (p < 0.01). The concurrent administration of propylene glycol and rumen-protected choline chloride resulted in the highest birth weight among treatment groups (p < 0.01). Lambs born to PMC and RPC ewes had a higher survival rate and rectal temperature than those born to RF ewes (p < 0.05). It can be concluded that although dietary restriction does not have adverse effects on lambs’ performance compared with ad libitum intake, the combined administration of propylene glycol and rumen-protected choline chloride in the ewes’ restricted diet can improve placental characteristics and subsequently amend lambs’ birth weight and body size. Therefore, the combined administration of these additives can be practiced during feed restriction.

Factors Associated with Mortality of Lambs Born to Ewe Hoggets

Simple Summary

Pre-weaning lamb deaths limit the production performance from ewes that are bred as hoggets (at 6–9 months of age). The present study aimed to investigate factors that are associated with increased likelihood of lamb death and the cause of that death, in lambs and in ewe hoggets over the lambing period. This was also compared to rates in mature-age ewes and their lambs. Lambs with low birthweights or that were born as twins were more likely to die, as were lambs whose dams had greater live weight changes during pregnancy. Ewes deaths during the lambing period accounted for approximately 11% of lamb deaths. The most common cause of hogget lamb deaths was stillbirth (lamb born dead) but this was an uncommon cause of death in lambs born to mature-age ewes. Management tools to increase lamb birthweights, and supervision of ewe hoggets at lambing time, are recommended.

Abstract

The reproductive performance of ewe hoggets is poorer than that of mature-age ewes due to production of fewer lambs with poorer survival. Scant data are available on the risk factors for, and causes of, the mortality for lambs born to ewe hoggets, the impact of ewe deaths on lamb loss, and the causes of death for lambs born to ewe hoggets vs. mature-age ewes lambing in the same circumstances. In this study, 297 lambs born to 1142 ewe hoggets were necropsied along with 273 lambs born to 1050 mature-age ewes. Low lamb birthweight, multiple litter size, and increasing ewe hogget average daily gain from breeding to late pregnancy were risk factors for lamb mortality. The most common cause of mortality for lambs born to ewe hoggets was stillbirth and the risk factors for stillbirth were similar to those for lamb mortality generally. Approximately 11% of ewe hoggets’ lamb deaths were due to the death of the dam. Causes of mortality differed between lambs born to ewe hoggets vs. those born to mature-age ewes. Management practices to increase ewe hogget lambs’ birthweights (particularly those from multiple litters) and supervision of ewe hoggets at lambing time are recommended.

Quantifying the value of on-farm measurements to inform the selection of key performance indicators for livestock production systems

The use of key performance indicators (KPIs) to assist on-farm decision making has long been seen as a promising strategy to improve operational efficiency of agriculture. The potential benefit of KPIs, however, is heavily dependent on the economic relevance of the metrics used, and an overabundance of ambiguously defined KPIs in the livestock industry has disincentivised many farmers to collect information beyond a minimum requirement. Using high-resolution sheep production data from the North Wyke Farm Platform, a system-scale grazing trial in southwest United Kingdom, this paper proposes a novel framework to quantify the information values of industry recommended KPIs, with the ultimate aim of compiling a list of variables to measure and not to measure. The results demonstrated a substantial financial benefit associated with a careful selection of metrics, with top-ranked variables exhibiting up to 3.5 times the information value of those randomly chosen. When individual metrics were used in isolation, ewe weight at lambing had the greatest ability to predict the subsequent lamb value at slaughter, surpassing all mid-season measures representing the lamb's own performance. When information from multiple metrics was combined to inform on-farm decisions, the peak benefit was observed under four metrics, with inclusion of variables beyond this point shown to be detrimental to farm profitability regardless of the combination selected. The framework developed herein is readily extendable to other livestock species, and with minimal modifications to arable and mixed agriculture as well.

Genetic parameters and trends for lamb survival following long-term divergent selection for number of lambs weaned in the Elsenburg Merino flock

Context Mortality of new-born lambs is well known to have important implications for both animal production and welfare. Improving survival rates by genetic selection is very desirable, but the low heritability of survival traits challenges the prospect of useful genetic gain. Aim This study aimed to derive genetic and environmental parameters for lamb survival in the Elsenburg Merino resource flock. It also investigated correlations to possible indicator traits birthweight and birth coat score and reported genetic progress in breeding values for lamb survival following 33 years of divergent selection. Methods The flock was divergently selected for number of lambs weaned and was separated by the High (positive) and Low (negative) selection groups. The pedigree file identified 8138 lambs as the progeny of 273 sires and 2062 dams. The study considered total survival from birth to weaning (Tsv) that was also partitioned into perinatal survival to 3 days of age, and the remaining period. Variance components were derived by linear mixed models by using the ASREML® program. Genetic trends were derived by predicting mean breeding values for selection groups within each year and evaluated by fitting linear and broken-stick regression models. Results Predicted Tsv of H-line lambs (0.81 ± 0.01) was higher (P &lt; 0.01) than that of L-line lambs (0.68 ± 0.01). Heritability was significant but low for survival traits (0.03–0.07), moderate for birthweight (0.16) and high for birth coat score (0.54). Genetic trends of the H-line trended divergently (P &lt; 0.01) to the L-line for survival traits, but a changepoint (P &lt; 0.01) in trend suggested that the H-line reached a selection plateau following 19–22 years of selection. Preceding this period, the rate of genetic change equalled ~1% of the mean for Tsv. Conclusions Despite the low heritability of survival, the genetic trends reported in this study contradicted the premise that genetic selection is not a worthwhile method to reduce incidences of lamb mortality. Implications It is recommended that lamb survival phenotypes should be recorded and incorporated into indices individually where possible, but composite traits are a viable alternative.

The effects of parasitism on ewes for prime lamb production in western Victoria

Context Internal parasites are estimated to cost the Australian sheep industry AUD436 million per annum (p.a.). Aims To assess the effects of parasitism in flocks producing prime lambs in the 500–700 mm p.a rainfall. area of Victoria. Methods Ewes on two farms that followed ‘best practice’ gastrointestinal parasite control programs (BP) and two farms that did not (regionally typical, TYP) were compared. Separate cohorts of ewes were monitored from pregnancy scanning to their subsequent joining each year for three consecutive seasons. Observations included worm egg count (WEC), bodyweight, condition score and presence of breech soiling (dag). These were compared between groups that were treated to suppress parasitism (SUP) and those treated according to the usual program used on that farm (NSUP). Data from individual ewes were analysed using a multivariable, mixed-effects regression model. Key results After adjusting for known confounders, SUP ewes were 1.2 (95% CI 0.80–1.6) kg heavier than NSUP ewes. Mature SUP ewes were significantly heavier than NSUP ewes at their next joining on 6 of 18 occasions, mostly following winters when ewes experienced nutritional stress. Ewe hoggets and Merino ewes were generally more susceptible to parasitism than mature non-Merino ewes; single-bearing ewes were less susceptible than those bearing twins. The effects of parasitism were reduced when peri-parturient ewes had an optimal condition score and grazed adequate pastures. Conclusions Ewes were more vulnerable to parasitism when immature, twin-bearing, or under nutritional stress. Some of the greatest differences between SUP and NSUP ewes occurred following periods of low feed availability and/or ewe condition score. The difference between the mean bodyweight of SUP and NSUP Merinos was not always greater than that of the non-Merinos. WECs are not a sole reliable indicator of the effects of parasitism in this class of sheep. Implications Immature or twin-bearing ewes, and those in suboptimal body condition, should be managed considering their increased vulnerability to parasitism, and WEC interpreted alongside other factors. Controlled release capsules were not cost effective in reducing production loss from gastrointestinal nematodes in most years but may be effective in reducing the effects of clinical parasitism in some cases.

Performance of sheep systems grazing perennial pastures. 4. Simulated seasonal variation and long-term production

Choice of sheep-management system alters both production potential and the production risk due to variability in seasonal conditions. This study quantified production and gross margins from systems based on Merino ewes and varying in stocking rate, time of lambing, and the proportion of ewes joined to terminal-breed or Merino rams. Simulation studies were conducted between 1971 and 2011 using the AusFarm decision-support tool for a grazing property in southern New South Wales. Joining between December and May resulted in higher gross margins than in other months because of higher numbers of lambs sold combined with a lower requirement for supplementary feeding. More ewes could be carried per hectare for April joining than February joining to achieve the same midwinter stocking rate and risk of feeding. Self-replacing systems could produce median gross margins similar to those with replacement ewes purchased, but gross margins were sensitive to the cost of replacement ewes. Of the systems compared, February joining to Merino rams produced the lowest gross margins at all stocking rates, but this system also had the lowest variability among years. The advantage of different systems was dependent on seasonal conditions, which altered lamb production and supplementary feeding. The median ranking of systems for gross margin generally did not alter with changes in feed, sheep or wool values. Large increases in gross margins can be achieved through use of terminal-breed rams, optimal stocking rates and time of lambing, but the superiority of any option depended on production system, price assumptions and seasonal conditions.

Decreasing the mob size but not stocking rate of ewes at lambing increases the survival of twin lambs born on farms across southern Australia

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 &lt;4 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 &lt;4 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 &lt; 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.

Pregnancy and Litter Size, But Not Lamb Sex, Affect Feed Intake and Wool Production by Merino-Type Ewes

Simple Summary

We examined whether feed intake and wool production are affected by pregnancy, litter size, or lamb sex on Merino genotype ewes. We observed that feed intake was influenced during pregnancy and lactation by litter size; whereas, wool production was influenced by litter size, but not by the sex of the lambs during pregnancy.

Abstract

Two experiments (Australia and Mexico) tested whether feed intake (FI) and wool production (WP) are affected by pregnancy (PRG), litter size (LZ), or lamb sex (LS) in Merino-type ewes. In Experiment-1, ewes were either not pregnant (NPR; n = 6), or carrying 1 (PR1; n = 7) or 3 (PR3; n = 11) fetuses, were studied in individual pens. NPR ewes had lower (p < 0.02) FI throughout PRG and lactation (LAC), except around lambing (p < 0.001). Following lambing, FI increased in PRG ewes (p < 0.001) to double the values in NPR ewes. PRG reduced WP (p < 0.001); in PR3, WP was lower than for both PR1 and NPR (p < 0.001). WP decreased during LAC and was lower in ewes rearing lambs than in NPR ewes (p < 0.001). Experiment-2 used 48 pregnant ewes (28 bearing singles and 20 bearing twins). Dam and lamb live weights (LW) and body condition (BC) were recorded from birth to weaning at 60 d, and dam fleece weight (DFW) was measured at weaning (12 months growth). WP was higher in ewes bearing and rearing single lambs than in ewes bearing twins (p < 0.001). DFW was positively (p < 0.01) related to LZ, dam LW, and BC, but not to changes in dam LW during LAC, or to lamb weight at birth or weaning, or LW gain, or LS. In conclusion, FI was affected during PRG and by LZ during LAC, whereas WP was influenced by LZ, but not LS, only during pregnancy.

Crossbred ewes gain more weight and are fatter than Merino ewes when managed together but similar coefficients predict lamb birthweight and survival

Current Australian ewe management guidelines are based on research from Merino ewes and have been transposed to crossbred ewes. It is unknown whether guidelines developed for Merino ewes are applicable to crossbred ewe production systems. To investigate this, the effect of ewe liveweight and condition score profile during pregnancy on lamb birthweight and survival for Border Leicester × Merino (BLM) crossbreds was compared with Merino ewes. Condition score profiles of 720 Merino and 680 BLM ewes were managed from 50 days after ram introduction to achieve one of four target condition scores at lambing. There were three replicates of the four target condition score treatments and both breeds of ewes were in each plot. By Day 140 after rams in, the BLM ewes were fatter (P &lt; 0.001) and heavier (P &lt; 0.001) than the Merino ewes, despite being managed in the same plots. Liveweight at conception and change in liveweight in late pregnancy of the Merino and BLM ewes had a similar effect on the birthweight and weaning weight of their lambs. However, birthweight and weaning weight of lambs from BLM ewes was less sensitive to ewe liveweight change in early pregnancy. Birthweight survival curves were similar in lambs from Merino and multiple-born lambs from BLM ewes, and the survival of lambs from multiple-bearing BLM ewes responded to manipulation of condition score in a similar pattern to lambs from Merino ewes. Therefore, managing liveweight or condition score of multiple-bearing BLM ewes is likely to improve lamb survival in a similar fashion to lambs from Merino ewes, although the absolute response in survival will be smaller than that achieved in Merino ewes at the same condition score. In addition, it is important to manage liveweight of both single and multiple-bearing BLM ewes during pregnancy to optimise weaning weight of their lambs, as those lambs born to BLM ewes of low liveweight were significantly lighter at weaning.

Offering maternal composite ewes higher levels of nutrition from mid-pregnancy to lambing results in predictable increases in birthweight, survival and weaning weight of their lambs

Management of nutrition during pregnancy for maternal composite ewes has the potential to improve lamb production and survival in prime lamb production systems but existing condition score (CS) guidelines developed for Merinos may not be appropriate for the optimum production of maternal ewes. To address this, three replicated experiments were conducted at two research sites in Victoria and one in Western Australia. Ewes (781–800 per site) were allocated to four CS treatments following pregnancy scanning (~Day 50) and differentially fed to reach approximate targets of CS 2.4, 2.8, 3.2 and 3.6 by lambing. Single and multiple bearing ewes grazed together, and nutritional treatments were applied until the end of lambing after which ewes and lambs were aggregated into management groups containing all treatments. At lambing, maternal ewe liveweight had a range between treatments of 13.7–19.1 kg (average 16.4 kg) and CS varied by 1.1–1.5 of a CS (average 1.24). Across site analysis indicated that lamb birthweight and weaning weight increased with application of higher CS treatments (P &lt; 0.001). There was also an improvement in survival of multiple born lambs with increasing CS at lambing (P &lt; 0.001). Birthweight was significantly related to survival (P &lt; 0.001) at all sites with no significant effect of birth type on lamb survival. Changes in birthweight and weaning weight could be predicted from ewe joining liveweight, ewe liveweight change to Day 90 and ewe liveweight change Day 90 to lambing. The coefficients derived for each of these effects were similar to those found in previous experiments examining Merino and crossbred Border Leicester Merino ewes. The optimum CS targets for multiple bearing maternal composite ewes may be higher than the industry recommended target for Merino ewes based on advantages in lamb survival and weaning weight.

Seed contamination in sheep: new investigations into an old problem

Seed contamination significantly affects production capacity and animal welfare in Australian sheep flocks and causes considerable financial loss to producers and processors across sheepmeat value chains. Seven grass-weed species contribute to seed contamination in Australia, with barley grass (Hordeum spp.) identified as a key perpetrator. Herbicide resistance and variable dormancy emerging in southern Australian barley grass populations are thought to enhance its capacity for successful pasture invasion, further exacerbating the potential for seed contamination in sheep. The present article reviews the current literature regarding the impact and incidence of seed contamination on sheepmeat production, with particular reference to key grass-weed species prevalence across Australia. Data are presented on a recent incidence of carcass contamination across years, where incidence varied between 11% and 80% from 2009 to 2013, contracting to between 2% and 60% during 2014 and 2015. Key areas requiring future research are defined. Understanding the biology of key grass weeds, historical influences and economic consequences associated with seed contamination in sheep may assist in defining future risks to sheep production and improve weed management. Furthermore, examining more recent data describing the current status of seed contamination across Australia and the associations with causal weed species may aid the development of critical weed-management strategies in highly infested regions, subsequently limiting the extent of future seed contamination.

Supplementation of Merino ewes with vitamin E plus selenium increases α-tocopherol and selenium concentrations in plasma of the lamb but does not improve their immune function

Vitamin E and selenium have been reported to improve immune function across a range of species. Ewes lambing on poor-quality dry pasture in autumn in Western Australia are at risk of being deficient in vitamin E and selenium at lambing thus predisposing their lambs to deficiencies and increasing the risk of infection and disease. This study tested the hypotheses that (i) supplementation of autumn-lambing ewes with vitamin E plus selenium in late gestation will increase the concentrations of vitamin E and selenium in plasma in the ewe and lamb and (ii) that the increased concentrations of vitamin E and selenium in plasma in the lambs will improve their innate and adaptive immune responses and thus survival. Pregnant Merino ewes were divided into a control group (n=58) which received no supplementation or a group supplemented with vitamin E plus selenium (n=55). On days 111, 125 and 140 of pregnancy ewes in the vitamin E plus selenium group were given 4 g all-rac-α-tocopherol acetate orally. On day 111 the ewes were also given 60 mg of selenium as barium selenate by subcutaneous injection. The concentrations of α-tocopherol and selenium were measured in ewes and/or lambs from day 111 of pregnancy to 14 weeks of age±10 days (weaning). Immune function of the lamb was assessed by analysing the numbers and phagocytic capacities of monocytes and polymorphonuclear leucocytes and plasma IgG and anti-tetanus toxoid antibody concentrations between birth and 14 weeks of age±10 days. Maternal supplementation with vitamin E plus selenium increased the concentration of α-tocopherol in plasma (1.13 v. 0.67 mg/l; P<0.001) and selenium in whole blood (0.12 v. 0.07 mg/l; P<0.01) of the ewes at lambing compared with controls. Supplementation also increased the concentration of α-tocopherol (0.14 v. 0.08 mg/l; P<0.001) and selenium (0.08 v. 0.05 mg/l; P<0.01) in lambs at birth compared with controls. There was no significant effect of supplementation on immune function or survival in the lambs.

Economic value of pregnancy scanning and optimum nutritional management of dry, single- and twin-bearing Merino ewes

The nutritional requirements of twin-bearing ewes are ~25% greater than those of ewes with single fetuses during late pregnancy and nearly twice those of non-pregnant ewes. Underfeeding ewes, resulting in liveweight loss during late pregnancy, can have adverse effects on the production and survival of both the lamb and the ewe, and improving twin-lamb survival is critical to improving the overall reproductive performance of the National Merino flock. Scanning for pregnancy status and litter size allows for more precise management of the nutrition of the ewe flock according to the different nutritional needs of dry, single- and twin-bearing ewes. In the present paper, we tested the hypothesis that it is profitable to identify pregnancy status and litter size, and the optimum nutrition profiles are different for dry, single- and twin-bearing ewes. We tested this by examining a range of nutrition strategies for flocks where only the dry ewes were identified, or for flocks where the single- and twin-bearing ewes were identified. A MIDAS model set up for the Hamilton region in south-western Victoria was used for this analysis as it represents the whole flock and it includes a powerful feed-budgeting module that optimises animal and pasture management across the whole farm. The survival and production of the single- and twin-born progeny was adjusted on the basis of the liveweight profile of the single- and twin-bearing ewes. Our hypothesis was supported and profitability was increased by approximately AU$4630/farm or AU$0.80/ewe, by scanning ewes for pregnancy status and litter size, and the optimum liveweight profiles were different for dry, single- and twin-bearing ewes. The majority of the increase in profit was due to identifying litter size and being able to differentially manage the single- and twin-bearing ewes. When ewes are scanned for pregnancy status and litter size, the most profitable combination of profiles involves all ewes losing 4 kg in early pregnancy and single-bearing ewes regaining the 4 kg to lamb at their standard reference weight, twin-bearing ewes gaining 8 kg to lamb above their standard reference weight and dry ewes losing a further 4 kg to be 8 kg lighter than their standard reference weight at lambing time.

Neonatal lamb mortality: factors associated with the death of Australian lambs

The objective of the present study was to examine the factors associated with the death of neonatal lambs. Postmortem autopsy data were collected from 3198 newborn lambs in the Sheep CRCs Information Nucleus Flock situated in various environments throughout southern Australia. The proportion dying by category from highest to lowest was starvation–mismothering (25%), stillbirth (21%), birth injury (18%), dystocia (9%), death in utero–prematurity (10%), predation (7%), cold exposure (5%), undiagnosed (4%), infection (1%) or misadventure (1%). Factors best explaining the probability of lambs falling into a death category included both birth type and birthweight for dystocia, stillbirth, starvation–mismothering and death in utero–prematurity. The probability of a lamb falling into any category was predicted at the mean birthweight, within birth type. Single-born lambs were more likely to die from dystocia and stillbirth, while twin lambs were more likely to die from birth injury, starvation–mismothering or from undiagnosed causes. Triplet lambs were more likely to die from starvation–mismothering or death in utero–prematurity. Sire type (Merino, maternal or terminal) did not affect the proportions of lambs within any category. The proportions lost to each cause of death were largely consistent among locations, despite the rate of death varying. Dystocia, stillbirth and birth injury, as evidenced by the presence of oedema around the head and neck or by lesions of the central nervous system, accounted for 48% of autopsied lambs. We conclude that for improvements to occur in the rates of lamb survival, the Australian sheep industry must focus on minimising losses due to dystocia, stillbirth, birth injury and starvation.

Prenatal origins of postnatal variation in growth, development and productivity of ruminants

This review provides an update on recent research into the effects of maternal nutrition on fetal biology and the growth, development and productivity of progeny in postnatal life of ruminant livestock. Evidence is summarised for effects on postnatal growth and body composition, feed intake and efficiency, carcass characteristics and meat quality, wool production, reproduction and lactation performance. In general, these demonstrated effects are not large in relation to the effects of postnatal nutrition and other environmental influences. The mechanisms underpinning the above production outcomes are briefly discussed in terms of systemic endocrine and metabolic responses, and cellular and molecular effects in skeletal muscle, bone, adipose tissue, wool follicles and brain of fetal, neonatal and adult progeny. Treatments observed to elicit tissue responses include maternal under- and overnutrition at various stages of pregnancy and placental insufficiency caused by increased litter size, chronic maternal heat stress and premating carunclectomy in sheep. The as yet meagre evidence for epigenetic mediation of intergenerational effects in ruminants is considered, as is the likelihood that other, more conventional explanations may suffice in some cases. Finally, evidence is summarised for the proposition that the placenta is not merely a passive conduit for nutrient transfer from dam to fetus, but plays an active role in buffering the effects of variations in maternal nutrition on fetal growth and development, and thence, postnatal outcomes.

Effect of previous reproductive performance on current reproductive rate in South Australian Merino ewes

Reproductive performance of ewes in the current year may be influenced by their performance in the previous year and by the ability of seasonal and management conditions to facilitate full recovery before the next breeding cycle. This possibility was tested by analysing reproductive data from 2100 South Australian Merino ewes mated to Merino rams annually from 1991 to 1997. The model fitted to the data included the fixed effects of previous reproductive performance (PRP) (no lambs born; single or multiple lambs born, none reared; single lambs born, singles reared; multiples born, singles reared; multiples born, multiples reared), age of ewe (2.5, 3.5, 4.5 years), year (1992–1997), bloodline (A, B, L, X) and all two-way interactions. Current-year parameters were net reproduction rate (NRR, lambs weaned of ewes joined) and its components of fertility (ewes lambing of ewes joined), fecundity (lambs born of ewes lambing) and lamb survival (lambs weaned of lambs born). Other parameters were lamb liveweight at weaning per ewe joined and pre-mating liveweight. In addition, repeatability values were calculated across ages for these parameters. NRR was higher in the current year for those groups of ewes that reared lambs in the previous year; this was associated with the highly productive multiple-bearing and -rearing groups having a liveweight at the next mating similar compared to that of groups that did not rear lambs. Repeatability values of 0.27 for NRR and 0.40 for fertility suggest there are genetic and permanent environmental components contributing to the differences observed among the PRP groups for NRR, particularly so for fertility. Selecting ewes after their first lambing opportunity on fertility alone at a rate of 90% would give a non-cumulative increase in fertility of 3.4% at subsequent lambing opportunities. Hence, improvements in the current ewe flock for NRR by graziers managing flocks of the South Australian Merino strain are likely to come from (1) identifying and selecting those ewes of high fertility from early records and (2) attending to management factors impacting on fecundity and lamb survival.

Whole-body fatness is a good predictor of phenotypic feed and liveweight efficiency in adult Merino ewes fed a poor-quality diet

Weight loss due to poor nutrition in adult ewes over summer–autumn is economically expensive due to immediate costs such as feed and labour but also due to ongoing costs to reproductive success and ewe health. We predicted that adult Merino ewes with a higher proportion of fat would be more efficient, both through lower intake and reduced weight loss. Four-year-old Merino ewes (n = 64) were held in single pens and fed a chaff-based diet either ad libitum, with the aim of achieving liveweight maintenance, or a restricted amount to achieve liveweight loss of 100 g/day. Liveweight change and feed intake were measured, and residual liveweight change and residual feed intake were used to indicate efficiency. There was a difference of 2 MJ of metabolisable energy per day between the most efficient and least efficient ewes for residual feed intake, and a difference of 90 g per day between the most efficient and least efficient ewes for residual liveweight change. There was a significant association between blood plasma concentrations of leptin and both liveweight and feed efficiency, so that ewes with high concentrations of leptin had a lower daily intake, and/or lost less weight than did those with low concentrations of leptin. Managing adult Merino ewes to maximise fat-tissue accretion during spring via genetics and/or nutritional management could be a useful strategy to reduce feed requirements during summer–autumn because the ewes will be more efficient and have larger fat reserves to lose before achieving a lower critical limit.

Grazing crops: implications for reproducing sheep

Integration of crops and livestock has been revitalised in Australia, initially as an opportunity to increase cropping within the high-rainfall grazing zones, and more recently, to improve enterprise diversification and profitability across the low-, medium- and high-rainfall, and mixed-farming zones. Young crops are highly digestible (>80% dry matter digestibility, DMD) with a high energy density (>12 MJ/kg DM) and, in much of southern Australia, fill a winter feed gap. The quality and time of feed availability also coincide with the high nutrient requirements of ewes in late pregnancy and lactation. In Western Australia and South Australia, young crops are available for lactating ewes and young growing lambs (autumn lambing). For the smaller proportion of growers who lamb later in winter, young crops are available for the last 1–2 months of pregnancy. In the later-lambing states of New South Wales and Victoria, crops may be grazed by ewes at any stage of pregnancy and lactation and/or by young lambs. In Tasmania, crops are more likely to be available during early–mid-gestation. Limited studies on feed budgeting with grazing crops have indicated that ewes can maintain or even increase liveweight, with a much lower level of feed on offer than would be required with traditional pastures (<500 kg DM/ha). This has the potential to increase whole-farm stocking rates and/or reduce fetal mortality, increase lamb birthweight and survival and improve lifetime production. Maintaining or increasing ewe liveweight during pregnancy and lactation may also result in heavier ewes the following year and higher ovulation rates. Pregnancy and lactation are also periods of increased susceptibility to metabolic disturbances. The composition of young crops increases this susceptibility. Pregnancy toxaemia, hypocalcaemia and hypomagnesaemia can influence ewe health and fetal survival. Chronic acidosis and excessive ammonia absorption from rapid introduction of pregnant ewes onto young crops may risk appetite loss and increase susceptibility to pregnancy toxaemia. Low magnesium and sodium combined with high potassium increases the risk of grass tetany. Most young crops (except canola) also have a tetany index >2.2, indicating a high risk of grass tetany. The elevated potassium also contributes to a high dietary cation–anion difference of approximately +49 mEq/100 g DM and this may cause metabolic alkalosis and hypocalcaemia. Pregnancy toxaemia, hypocalcaemia and grass tetany are all potential causes of increased ewe mortality. Pregnancy and/or lactation outcomes will also be influenced by a deficiency of trace elements. Grazing young crops in areas with a history of selenium, copper, iodine and cobalt deficiency will increase susceptibility to deficiency by increasing growth and feed intake. In conclusion, the grazing of young growing crops presents new opportunities for increased production and stocking rates in the mixed-farming zones. The value of this feed source is well recognised by some producers. While growing crops have a highly productive potential, they also come with an increased risk of a range metabolic disturbances and nutritional imbalances. These risks can be minimised by regular monitoring of livestock and crop biomass and the provision of mineral supplements.

Monitoring liveweight in sheep is a valuable management strategy: a review of available technologies

Liveweight is a widely accepted proxy for the energy status of sheep at a particular point in time. Fleece- and conceptus-free ewe liveweight and liveweight change influence the productivity of the ewe and optimisation may increase whole-farm profitability. Despite this, it is uncommon for producers to monitor ewe liveweight regularly and objectively. The current review discusses why ewe liveweight is important, identifies and assesses available technologies for monitoring sheep liveweight, and highlights future research priorities. The common theme in the literature is that while there are options that could possibly be used to monitor the liveweight of sheep in extensive grazing systems, few of them offer realistic solutions, especially in regard to timeliness of data collection. Thermal and stereo imaging, body measurements and plasma hormonal assays are unlikely to be commercially viable, while visual assessment, although widely practised, offers a surprisingly poor indication of sheep liveweight. Alternatively, assessment of body condition (condition scoring) or fat (fat scoring) offers viable methods of assessing sheep energy status; however, like conventional static weighing, they are performed infrequently and therefore contribute little to the day-to-day tactical management of sheep flocks. Walk-over weighing systems offer a feasible alternative for regular monitoring of sheep liveweight. Such systems are fully automated, and may be operated remotely. Currently, there are challenges associated with monitoring the liveweight of individual animals using such systems and hence there is little commercial opportunity for individual animal management. Mob-based walk-over weighing, which generates flock average liveweight estimates, offers greater potential in the short term, although the technology would benefit from further research and development, primarily to increase the frequency and repeatability of liveweight capture.

The critical control points for increasing reproductive performance can be used to inform research priorities

Improving the reproductive performance of sheep is a national research priority, but identifying which components of the reproductive process should be the highest priority for further research is complex. The analysis reported in this paper tested the hypothesis that research areas can be prioritised using knowledge of potential gains and bio-economic modelling of critical control points. The analysis was carried out in two parts and the control points included increasing conception, increasing survival of single- or twin-born lambs, increasing survival of ewes at lambing, increasing weaner survival and increasing early reproductive success. For each control point, four productivity levels were examined and the average change in profit per unit of change in the control point per animal was calculated for three flock types. The second component quantified the potential industry gain from the change in profit per unit in each control point, the potential for change (number of units) and the potential adoption (number of ewes or weaners). On the basis of the assumptions used, increasing survival of twin-born lambs was the area with the highest pay-off and had an estimated value of AU$515 million. The value of increasing twin-lamb survival compared with single-lamb survival was affected by the proportion of single- and twin-bearing ewes in the flock. In a flock based on maternal ewes, there are relatively more twin-bearing ewes, so increasing twin survival was a higher priority than for flocks based on Merino ewes in which the proportion of twins was lower. The analysis suggested that the second most important area for future research was improving reproduction from ewe lambs with a pay-off of AU$332 million, followed by improving survival of ewes AU$303 million, improving survival of single born lambs AU$285 million, improving the number of lambs conceived AU$235 million, improving reproduction from 2-year-old ewes AU$221 million and, finally, improving weaner survival AU$52 million. The priorities determined using this method were robust and varying the assumptions of the bio-economic analysis had little impact on the priorities. There was no change in the overall ranking of the critical control points from either increasing the meat or wool price by 20% or altering the flock structure of the Merino flock. Therefore, we can be confident that the priorities determined in the present analysis with current prices and production systems will be valid in to the future.

Vitamin E status and reproduction in sheep: potential implications for Australian sheep production

Vitamin E concentrations in dried pastures, stubble and most grains are below the recommended requirement of 10–25 mg/kg dry matter (DM). Sheep grazing in an environment when dry pastures and cereal crop stubbles are their primary source of nutrients for a few months have a high risk of developing vitamin E deficiency. If the low vitamin E status coincides with late gestation, the neonate is likely to have a deficiency of vitamin E. Some of the consequences of this are well known, with nutritional myopathy (with high mortality) a risk in young growing sheep unless vitamin E supplements are provided. Vitamin E plays an important role in the management of oxidative stress. Sperm are subject to oxidative damage due to high metabolic rate and high concentration of polyunsaturated fatty acids in their membranes. Oxidative stress may also compromise follicular development and ovarian activity. Vitamin E is also involved with improvement in immune response. For these reasons, vitamin E status is important for reproductive efficiency in both males and females and in the survival of lambs and weaners. In addition, vitamin E deficiency is potentially exacerbated by a lack of other nutrients involved in the management of oxidative stress and immune function, such as selenium (Se) and sulfur amino acids. A Se concentration of 0.1 mg/kg DM in feedstuffs is required to maintain immune competency in sheep. In considering possible consequences for reproduction, further investigation is justified into: (i) effects of low vitamin E, in combination with low levels of other natural antioxidants, on the quality and quantity of sperm produced before and during mating; (ii) follicle development, fertilisation and embryonic mortality in Se-supplemented ewes; (iii) assessment of supplementing formulated antioxidants to rams and ewes during the mating season; (iv) managing oxidative stress in the newborn – consequences of large doses of vitamin E to ewes before parturition to boost lamb reserves; (v) potential benefits to lamb survival through boosting maternal innate immunity; (vi) choices for boosting antioxidant and immune function in ewes and lambs through ‘immune pack’ nutrient options that may target nutrients lacking in dry grass pastures; (vii) the potential role of heat stress in modifying the requirements for, and responses to, vitamin E in extensive grazing systems.

Increasing weight gain during pregnancy results in similar increases in lamb birthweights and weaning weights in Merino and non-Merino ewes regardless of sire type

Birthweight is the single largest determinant of survival in lambs and can be predicted from ewe liveweight at conception and liveweight changes during pregnancy. These prediction equations are known for Merino ewes, but it is unknown if they are applicable to non-Merino breeds. We tested the hypothesis that increasing conception weights of ewes will increase the birthweights, survival to weaning and weaning weights of their lambs, irrespective of ewe or sire breed, but that non-Merino lamb birthweights would be less responsive than Merino lamb birthweights, to changes in ewe liveweights during pregnancy. Ewe liveweight, lamb birth and weaning weight records from Merino sires mated to Merino ewes (MM), Border Leicester Merino (Maternal) sires mated to Merino ewes, Poll Dorset or Suffolk (Terminal) sires mated to Merino ewes (TM), and Terminal sires mated to Border Leicester Merino ewes (TMAT) were analysed from the 2007 to 2011 lambings of eight information nucleus flocks. Lamb birthweights increased by 0.032 ± 0.0012 kg from MM ewes and 0.024 ± 0.0026 kg from TMAT ewes with every 1-kg increase in conception weight (P < 0.001). Irrespective of breed, for every 1-kg increase in liveweight change during early and late pregnancy, lamb birthweights increased by 0.021 ± 0.0019 kg and 0.034 ± 0.0019 kg and weaning weights by 0.26 ± 0.013 kg and 0.09 ± 0.011 kg, respectively (P < 0.001). Survival to weaning of single, twin and triplet lambs was highest for lambs from TMAT ewes (89.3% ± 1.25, 84.6% ± 1.49 and 73.4% ± 2.35) and lowest for TM ewes (80.2% ± 1.89, 72.8% ± 2.09 and 57.4% ± 2.98; P < 0.001). Coefficients relating ewe liveweight change during pregnancy to lamb birthweights are similar for Merino and Maternal ewes, however conception weights of Maternal ewes are significantly heavier than Merino ewes when run together, and lamb birthweights from Maternal ewes are less responsive to ewe conception weights. The coefficients reported in this paper will enable development of optimum management guidelines for single-, twin- and triple-bearing Maternal ewes.

Plantain (Plantago lanceolata L.) and perennial ryegrass (Lolium perenne L.) as pregnancy and lactation feed for ewes joined at 8 months of age

Ewe nutrition during pregnancy and lactation is a key determinant of ewe and lamb performance. A paddock-scale field experiment in western Victoria, Australia, tested the hypothesis that grazing maiden ewes on plantain (Plantago lanceolata L.) from mid-pregnancy until lamb weaning (July 2010–January 2011) would increase ewe liveweight and condition score during this period, reduce worm egg counts, and increase lamb liveweights at birth, marking and weaning, relative to tetraploid perennial ryegrass (Lolium perenne L.), but that further increases would be achieved by offering a spatially arranged sward of plantain and perennial ryegrass. The experiment tested three treatments: plantain (PL), perennial ryegrass (PR), and a 50 : 50 (by area) spatially separated mixture of perennial ryegrass and plantain (PR + PL). Plots were ~1 ha in size arranged in a randomised complete block design with four replications. The ewes were Coopworth composites joined at 8 months of age. Feed-on-offer levels (kg DM/ha) did not differ (P > 0.05) between treatments, with 2.3–3.0 t DM/ha being available pre-grazing. Twin-bearing ewes had higher (P < 0.05) liveweights when offered PR + PL compared with PR or PL at late-pregnancy and higher (P < 0.05) liveweights than PR but not PL (P > 0.05) at lamb marking. At weaning, single-born lambs were heavier (P < 0.05) on PR than PR + PL, with the PL being intermediate. There were no other significant differences (P > 0.05). This experiment has found that feeding plantain to ewes during pregnancy and lactation, or offering ewes spatially separated mixes of plantain and perennial ryegrass, offers no clear liveweight or worm egg count improvement for ewes and lambs relative to a tetraploid perennial ryegrass under Western Victorian conditions.

A review of the genetic and epigenetic factors affecting lamb survival

Poor lamb survival pre-weaning is a major source of reproductive inefficiency in Australian sheep flocks. While nutrition and management options have been extensively researched and promoted to improve lamb survival, the present review focuses on the prospects for obtaining genetic gain and helps identify selection strategies for boosting such gains to improve overall reproductive efficiency in the Australian sheep industry. Estimated heritability for lamb survival using linear model analysis is low, although use of threshold models suggests that heritability could be higher, which, if true, could help explain the substantial genetic gains obtained in long-term selection experiments. Epigenetic mechanisms may hinder selection and quantitative trait-loci identification through confounding and/or masking genetic variances and co-variances. With sufficient information, these effects could be considered in genetic evaluations by identifying those components that are amenable to selection. Regarding indirect selection, finding effective criteria for improving lamb survival has proved elusive. Most measures of maternal behaviour, temperament and lambing difficulty researched are poorly correlated genetically with lamb survival. Of lamb behaviours and thermo-genic indicators studied, latency to bleat following handling by humans is moderately genetically correlated with lamb survival, as is neonatal rectal temperature. Industry application remains to be adequately explored for the more promising of these measures. Finally, in lieu of direct selection for lamb survival, there is merit in selecting for multiple-rearing ability or its equivalent, possibly with additional selection criteria for lamb survival and reproductive efficiency.

The economic benefits of providing shelter to reduce the mortality of twin lambs in south-western Victoria

Achieving higher lamb weaning percentages by reducing lamb mortality can improve the profitability of sheep enterprises. In this paper we estimated the financial benefits from providing shelter to reduce the mortality of twin lambs in self-replacing Merino or dual-purpose Merino flock enterprises in south-west Victoria. A whole-farm bio-economic model (MIDAS) was initially used to estimate the increase in profit from reducing mortality of twin lambs and a second analysis included the costs of using perennial grass hedges to provide the shelter during lambing. The economic value of providing shelter was tested at three rates of twinning (10, 30 and 50%), three rates of mortality without shelter (70, 50 and 30%) and two levels of reduction in lamb mortality by providing shelter (25 and 50% reduction). A sensitivity analysis to wool and lamb prices, costs of establishing the grass hedges and stocking rates in the shelter area were also tested. Overall, more than 2500 scenarios were tested. Across the range of twinning rates and levels of twin mortality tested, at standard wool and meat prices, providing shelter to the dual-purpose Merino ewe flock was always profitable ($0.05 to 11.35/ewe) and the profits from providing shelter to the self-replacing Merino ewe flock were generally lower ($0.15 to $6.35/ewe). The impacts of changing wool and lamb prices depended on enterprise type, whereas the costs of establishment of the hedges or stocking rate of ewes in the hedge area during lambing had little impact on profitability. The main factor that determined the economic return from shelter was the reduction in mortality provided by the shelter but the proportion of twin-bearing ewes in the flock and the base rate of lamb mortality without shelter was also important. Overall, based on the assumptions used, we conclude that the profitability of many sheep enterprises lambing during frequent high chill weather conditions in temperate areas of south-eastern Australia could be improved by providing low cost shelter for twin-bearing Merino ewes lambing from July to September.

A survey of post-weaning mortality of sheep in Australia and its association with farm and management factors

A cross-sectional telephone survey of post-weaning sheep management and mortality was conducted involving 1410 farmers from across Australia. The average reported post-weaning mortality was 4.6%. Mortality was greatest in Queensland and Western Australia, and least in New South Wales, Victoria, and South Australia. Weaner mortality was also greater in the pastoral zone than in the sheep–cereals or high-rainfall zones. Overall, 44% of farms had mortality identified as ‘high’, exceeding the suggested benchmark of ≤4% per annum. High mortality was reported on 50% and 32% of farms with predominantly Merino and crossbred weaners, respectively. There was no statistically significant association between high mortality and the main month of lambing for a flock. Larger sheep flocks, flocks with a smaller proportion of weaners, and farms of smaller area were associated with a greater likelihood of high weaner mortality. The odds of high mortality in weaner flocks that were routinely separated according to bodyweight or condition score was half that of flocks that were managed as one group. Overall, 84% of farmers regularly provided supplementary feed to weaner sheep, but the kind of supplement offered and the proportions of farms routinely supplementing differed between states and sheep production zones. Only high-protein supplementary feeding was associated with lower odds of high mortality. This survey confirms that poor post-weaning survival remains a widespread issue for the Australian sheep industry but identifies farm and management factors associated with reduced weaner mortality.

Effects of three whole-farmlet management systems on Merino ewe fat scores and reproduction

As part of the Cicerone Project’s whole-farmlet experiment on the Northern Tablelands of New South Wales, Australia, the fat scores and reproductive performance of ewes were measured to assess the effect of different management systems on these important production parameters over time. The three farmlets (each of 53 ha) included one (farmlet B) subjected to ‘typical’ district management consisting of moderate levels of inputs and a target stocking rate of 7.5 dse/ha, with flexible grazing management across eight paddocks. A second farmlet (A) was managed in a similar fashion to farmlet B with respect to number of paddocks and grazing management, but modified by high rates of pasture renovation and higher levels of soil fertility, with a target stocking rate of 15 dse/ha. The third farmlet (C) was managed at the same level of moderate inputs as farmlet B but employed intensive rotational grazing over 37 paddocks and also had a high target stocking rate of 15 dse/ha. The experiment was conducted over 6.5 years from July 2000 to December 2006. In spite of the fact that target levels of stocking rate were chosen at the beginning of the experiment, stocking rate, together with fat scores and reproduction were treated as emergent properties of each farmlet system. Joining took place in April–May and lambing occurred in September–October of each year. Over the first 2 years of the experiment, there were few differences among farmlets in ewe fat scores or reproductive performance. From 2003 onwards, while the percentage of ewes pregnant was similar between farmlets, the average proportion of multiple births (ewes scanned in late July, with twins) was 30%, 16% and 12%, respectively, on farmlets A–C. However, lamb losses were greater on farmlet A, with average lamb mortalities recorded on farmlets A–C of 29%, 10% and 19%, respectively. Over the duration of the experiment, ewes on farmlets A and B were more often above a fat score level of 3, and less often below 2.5, than were ewes from farmlet C. Differences among farmlet ewes in fat score were found to be significant in 7 of the total of 13 assessments over the duration of the experiment. A generalised additive model applied to whole-farmlet data showed that green digestible herbage, legume herbage, stocking rate, the amount of supplement fed and especially the proportion of each farmlet grazed at any one time all influenced fat scores of ewes. While fat scores and conception rates tended to be highest on farmlet A, farmlet B had slightly better reproductive outcomes due to less lambing losses, whereas ewes on farmlet C tended to have somewhat lower fat scores and levels of reproduction. These farmlet-scale findings highlighted the importance for livestock managers to focus not only on grazing management, stocking rate and stock density during lambing, but also on the availability of sufficient green, and especially legume herbage, and the difficulty of overcoming a deficit in quality herbage with supplementation.

Evaluating seasonal risk and the potential for windspeed reductions to reduce chill index at six locations using GrassGro

The death of newborn lambs is a major factor influencing the reproductive efficiency of sheep enterprises. Adverse weather conditions (wind, precipitation and low temperature), either alone or in combination (chill index), can increase the level of newborn lamb mortality to over 50% of births for short periods through increased heat loss. The provision of shelter to reduce wind speed and therefore chill index (heat loss) has been shown to reduce lamb mortality; however, the reduction in mortality has been variable. This study used the decision support tool GrassGro to determine the likelihood of adverse weather conditions occurring at six locations across south-eastern Australia which varied widely in climate. Data were extracted for 24 consecutive weekly periods between May and October over 39 years (1968–2006) to evaluate daily precipitation, temperature, radiation, wind speed and chill index. The minimum, maximum and median values were calculated for all climatic factors for every week and year combination. The effectiveness of reducing wind speed to reduce the occurrence of a high chill index was also evaluated. The severity of these weather events varied between locations with the median weekly chill index rarely exceeding 1000 kJ/m2.h at Temora, but at both Hamilton and Orange this occurred in over two-thirds of the weeks examined. Reducing wind speed by 50% reduced the number of weeks with a median chill index exceeding 1000 kJ/m2.h in twice as many weeks at Hamilton and Yass compared with Orange. These results show that the potential for shelter to reduce chill index will vary according to the location and time of year. In locations where another climatic factor, such as low temperature or rainfall, has a greater influence on the chill index, shelter which only reduces wind speed, will be less effective than at locations where wind speed is the driver of chill index.

Participation in Lifetime Ewe Management results in changes in stocking rate, ewe management and reproductive performance on commercial farms

Lifetime Ewe Management is an extension program designed to assist sheep producers to improve their understanding of ewe nutrition and to develop the skills and confidence to improve their management. The course is based on a small-group extension model and was developed by the Lifetimewool project as a way to incorporate the research findings, economic modelling and producer guidelines developed by the project. Lifetime Ewe Management commenced in Victoria in the spring of 2006 and by the end of 2010, 221 producers had completed the 2-year program. The changes in knowledge, attitudes, skills, aspirations and management practices of 182 of these participants were examined. Participants of the Lifetime Ewe Management program increased their whole-farm stocking rates by 14%, increased lamb marking percentages by 11–13% depending on enterprise type, and decreased ewe mortality rates by 43%. These improvements resulted from a significant change in the perceived importance of managing ewes to condition-score targets to improve profitability and increases in the ability of participants to condition score ewes, assess pasture quantity and quality and feed budget. These changes were consistent regardless of how innovative the participants were at the beginning of the program. The appeal and success of the program was attributed largely to the small-group model where producers worked with their own flock under the guidance of a skilled facilitator and with access to effective decision-making tools. The Lifetime Ewe Management program design provides a blueprint for future extension programs striving to achieve widespread practice change.

The birthweight and survival of Merino lambs can be predicted from the profile of liveweight change of their mothers during pregnancy

The single largest influence on the survival of lambs in the first few days of life is their birthweight. Fetal growth and birthweight are regulated by genotype of the fetus, maternal genotype, maternal nutrition and the external environment. In this paper we report the extent to which the changes in maternal liveweight during pregnancy and lactation (liveweight profile) of Merino ewes can be used to predict the birthweight and survival of their progeny to weaning. At two sites [Victoria (Vic.) ~700 ewes and Western Australia (WA) ~300 ewes] in each of 2 years, a similar experiment used adult Merino ewes to explore effects of nutrition from joining to Day 100 of pregnancy and from Day 100 of pregnancy to weaning. The average difference between extreme treatments at Day 100 of pregnancy were 7 kg in ewe liveweight and 0.7 of a condition score (CS) and at lambing 11.9 kg and 1.3 of a CS. This resulted in average birthweights of progeny from different treatments ranging from 4.0 to 5.4 kg and survival to weaning ranging from 68 to 92%. Across the four experiments between 68 and 85% of all lamb deaths to weaning occurred within 48 h of birth. Lambs born to ewes in CS 2 at Day 100 of pregnancy were lighter (P < 0.05) in both years at the Vic. site than those from ewes in CS 3 at Day 100 of pregnancy. Lambs born to the ewes grazing a feed on offer of 800 kg DM/ha during late pregnancy were also lighter than those from other levels of feed on offer between 1100 and 3000 kg DM/ha at the Vic. site in both years and at the WA site in 1 year (P < 0.001). Lambs from the 800 kg DM/ha treatment during late pregnancy at the Vic. site had a lower survival than other treatments, especially in the second year. There were no significant effects of treatments on lamb survival at the WA site; however, the results were in the same direction. The birthweight of individual lambs was significantly related to the liveweight profile of their mothers. Their liveweight at joining, change in liveweight to Day 100 of pregnancy and change in liveweight from Day 100 to lambing all contributed (P < 0.05) to the prediction of the birthweight of their lambs. The responses were consistent across experimental sites and years, lamb birth rank and sex, and confirmed that the effects of poor nutrition up until Day 100 of pregnancy could be completely overcome by improving nutrition during late pregnancy. At the Vic. site, survival to 48 h was most influenced by the birthweight of the lamb and survival was significantly higher in single- than twin-born lambs and female than male lambs after adjusting for differences in birthweight. A higher chill index during the 48 h after birth reduced survival of both single and twin lambs to a similar extent, but reduced survival of male lambs more than female lambs. There were no effects of birthweight or chill index on lamb survival at the WA site where most lambs weighed more than 4 kg at birth and climatic conditions during lambing were less extreme. Overall, these results supported our hypothesis that improving the nutrition of Merino ewes during pregnancy increases birthweight and this leads to improved survival of their progeny.

The wool production and reproduction of Merino ewes can be predicted from changes in liveweight during pregnancy and lactation

Defining the nature of the relationship between change in liveweight throughout a breeding cycle and ewe wool production and reproduction would be useful for developing management guidelines for Merino ewes. In this paper we tested the hypotheses that (1) feed on offer has variable effects on liveweight profiles of individual ewes; and (2) liveweight profiles of individual ewes can be used to predict their fleece wool production and reproductive performance. At sites in Victoria and Western Australia in 2001 and 2002, pregnant Merino ewes were exposed to 10 nutritional treatments. In each of the four experiments, ewes in average condition score 3 at artificial insemination were fed to achieve either maintenance or loss of a condition score over the first 100 days of pregnancy before grazing one of five levels of feed on offer between Day 100 and lamb weaning. Across all four experiments, the average difference in ewe liveweight between extreme treatments was: 7.0 kg (range 4.7–8.7 kg) at Day 100 of pregnancy; 11.9 kg (range 4.9–17.8 kg) at lambing; and by weaning was 13.9 kg (range 8.8–22.7 kg). Liveweight at joining and liveweight change during pregnancy and lactation of individual Merino ewes were significantly related to their clean fleece weight, fibre diameter and staple length and thus the second hypothesis was supported. Heavier ewes at joining produced more wool that was longer and broader and this effect was consistent across both sites and years. A 10-kg loss in ewe liveweight between joining and mid pregnancy, mid pregnancy and lambing or during lactation reduced clean fleece weight by 0.4–0.7 kg and fibre diameter by 0.5–1.4 um. At the Victorian site, where ewes were shorn in summer, a loss of 10 kg in liveweight between joining and Day 100 of pregnancy reduced staple strength by 5 N/ktex. As expected the influence of food on offer on changes in ewe liveweight was different between years and sites and between late pregnancy and lactation due to a complex group of pasture and animal factors. Therefore, managing changes in ewe liveweight itself rather than feed on offer will achieve more predictable outcomes. A higher liveweight at joining resulted in a predictable improvement in ewe reproductive rate and liveweight at joining was more important than the liveweight profile leading up to joining. This paper has shown that it is possible to predict the differences in wool production and reproductive rate of flocks of Merino ewes if ewe liveweight records at key times are known.

Whole-farm profit and the optimum maternal liveweight profile of Merino ewe flocks lambing in winter and spring are influenced by the effects of ewe nutrition on the progeny's survival and lifetime wool production

Profitability of sheep production systems in southern Australia is optimised at a stocking rate that provides adequate nutrition for breeding ewes and enables efficient utilisation of grown pasture and supplements. In this paper we used bio-economic modelling to develop optimum liveweight1 profiles for spring-lambing Merino ewes in different environments. The modelling included the impacts of the ewe liveweight profile on the production of the ewe and the survival and lifetime wool production of her progeny. Fifteen ewe liveweight profiles were analysed for each region to determine the profitability of varying ewe liveweight at joining, varying rate of loss of liveweight after joining and the rate of gain in liveweight from the minimum to lambing. The analyses support the hypotheses that whole-farm profitability is sensitive to the liveweight profile of Merino ewe flocks and that there is a liveweight profile that maximises whole-farm profit. The variation between the most and least profitable ewe liveweight profile was $69 0002 per farm ($14.30/ewe) for south-west Victoria, $51 000 per farm ($8.70/ewe) for Great Southern Western Australia and $33 300 per farm ($9.70/ewe) for southern New South Wales. The changes in profit were due to differences in costs of feeding to achieve the ewe liveweight profile and its influence on the production of both the ewes and their progeny. Failure to include the impacts of liveweight profile on progeny survival and lifetime wool production incorrectly identifies the optimum ewe liveweight profile and provided inaccurate estimates of profitability. The optimum liveweight profiles for ewes lambing in spring were similar for all three regions and insensitive to changing commodity prices, pasture productivity and management. The optimum profile was to join ewes at ~90% of the standard reference weight of the genotype, lose a small amount of weight after joining and regain weight in late pregnancy to return to the joining weight by lambing. Regaining the liveweight lost in early pregnancy by lambing is the most important target to achieve. The cost per farm of missing this liveweight target by 1 kg was $13 000 ($2.60/ewe) for south-west Victoria, $8900 ($1.45/ewe) for Great Southern Western Australia and $5500 ($1.65/ewe) for southern New South Wales. By contrast, the cost per farm of missing the joining target by 1 kg was $5500 for south-west Victoria and less than $2000 across the other two regions. Whole-farm profit increased with increasing stocking rate up to an optimum and regardless of stocking rate there is an additional opportunity to increase whole-farm profit by up to 15% by managing ewes to achieve the optimum liveweight profile. This indicates that the optimum liveweight profile should be achieved by increasing the level of grain feeding and altering the timing of utilising the farm feed resources rather than manipulating stocking rate.

Improving the nutrition of Merino ewes during pregnancy increases the fleece weight and reduces the fibre diameter of their progeny's wool during their lifetime and these effects can be predicted from the ewe's liveweight profile

Nutrition of ewes during pregnancy can have permanent impacts on the production potential of their progeny. The hypothesis tested in the experiments reported in this paper was that improving the nutrition of Merino ewes during pregnancy and lactation increases the fleece weight and reduces the fibre diameter of their progeny’s wool during their lifetime. In addition, that these effects on the progeny’s wool production can be predicted from the ewe’s liveweight profile. At sites in Victoria and Western Australia in each of 2 years, a wide range in the liveweight and condition score profiles of Merino ewes was generated by varying the amount of supplements fed from joining to Day 100 of pregnancy and the amount of feed on offer grazed from Day 100 to weaning. The site in Victoria was based on perennial pastures and included both single- and twin-bearing ewes whereas the site in Western Australia was based on annual pastures and included single-bearing ewes only. The production and characteristics of wool from the progeny were measured until 51 months of age at the site in Victoria and 33 months of age at the site in Western Australia. The nutritional treatments and the resulting changes in ewe liveweight had significant impacts on the fleece weight and to a lesser extent the fibre diameter of wool produced by their progeny, but there were no consistent effects on other characteristics of progeny fleece wool. The fleece weight of the progeny was related to the liveweight change during pregnancy of their mothers (P < 0.05) and the relationships were similar for the two experiments at each site. At the site in Victoria, a loss of 10 kg in ewe liveweight between joining and Day 100 of pregnancy reduced fleece weight by ~0.2 kg at each shearing until 51 months of age whereas gaining 10 kg from Day 100 of pregnancy to lambing had the opposite effect. The effect of changes in ewe liveweight during late pregnancy on the fleece weight of their progeny at each shearing was of similar magnitude at the site in Western Australia. When evident, the effect of the ewe liveweight profile on the fibre diameter of progeny wool was opposite to the effect on clean fleece weight and the effect of poor nutrition in early to mid pregnancy could be completely overcome by improving nutrition during late pregnancy. Twin-born and reared progeny produced ~0.3 kg less clean wool at each shearing (P < 0.001) that was 0.3-μm broader (P < 0.001) than that from single-born progeny at the site in Victoria. However, the effects of varying ewe nutrition and ewe liveweight change during pregnancy on fleece weight and fibre diameter of progeny wool were similar (P > 0.05) for both single- and twin-born or reared progeny. Overall, these results supported our hypothesis and it is clear that the nutritional management of Merino ewes during pregnancy is important for optimal wool production from their progeny during their lifetime.

The merit of condition score and fat score as alternatives to liveweight for managing the nutrition of ewes

The liveweight profile of Merino ewes is related to the production and profitability of the sheep enterprise, but few producers measure liveweight to manage the nutrition of Merino ewes. In this paper we examine the relationship between changes in liveweight and condition score using data from the Lifetimewool project and compare condition score and fat score as alternative monitoring tools. Analyses of liveweight and condition score data from 15 flocks of Merino ewes representing a range of different genotypes and environments showed that the relationship between change in liveweight and condition score was on average 9.2 kg per unit change in condition score or 0.19 times the standard reference weight of the flock. In two experiments experienced operators were used to estimate the condition score and fat score in over 200 ewes and accredited ultrasound scanners measured the eye muscle and fat depth at the C site in the same ewes. All assessments were repeated several times in random order. Within 24 h of the assessments the sheep were slaughtered at local abattoirs where the tissue depth at the GR site was measured on the hot carcasses. Both condition score and fat score were highly repeatable though subject to operator bias. They were related to each other and to the objective measures of fat and eye muscle depth at the C site. However, 95% of sheep below condition score 2.5 had a tissue depth (muscle and fat) at the GR site ≤3 mm, by definition equal to fat score 1. As the condition score of ewes on commercial properties often fluctuates between scores 2 and 3, and small changes in condition score within this range can have large effects on welfare and profit, we conclude that condition score is the most appropriate alternative to liveweight for managing the nutritional profile of ewes.

The national Lifetimewool project: a journey in evaluation

The national Lifetimewool project commenced in 2001 and was funded until 2008. The objective of this project was to develop practical grazing management guidelines that would enable wool growers throughout Australia to increase lifetime production of wool per hectare from ewes. The project achieved its ambitious target of influencing 3000 producers to change their management of ewe flocks by adoption (or part thereof) of Lifetimewool messages and guidelines by 2008. The present paper focuses specifically on the evaluation work that was conducted on the project between 2003 and 2008. It is a noteworthy journey because it provides a case study of the effective implementation of an evaluation plan. The Lifetimewool project used ‘people-centred evaluation’ to help guide the creation of an internal evaluation plan. The six core principles followed were: participation; program logic, a people-centred focus; multiple lines of evidence; reflection and learning and a clearly documented and resourced evaluation plan. These principles were applied from the onset of the project. The Lifetimewool team used the evaluation findings to refine the initial design. Based on learnings from their evaluation journey, they created and modified the extension and communications components of the project. The present paper contends that the evaluation process itself enabled the project team to plan and adjust the course of the project through evidence-based reflection and that this helped ensure that the targets were achieved and demonstrated.

Managing the nutrition of twin-bearing ewes during pregnancy using Lifetimewool recommendations increases production of twin lambs

The effect on ewe and lamb production by differential management of single- and twin-bearing Merino ewes during pregnancy and lactation was examined. The hypothesis that the survival and productivity of single- and twin-born progeny is not affected by differential management of single- and twin-bearing ewes was tested. To test this hypothesis, two ewe flocks were monitored on a commercial property in the south-east of South Australia. The body condition score of one flock of ewes was managed according to Lifetimewool recommendations for southern Australian (Lifetimewool flock; n = 464). Lifetimewool recommendations are that body condition score should be 3.0 at mating and then allowed to decline to an average of 2.7, which is maintained until lambing. Twin- and single-bearing ewes were managed as separate mobs after pregnancy scanning to meet their energy requirements. The second flock was managed similarly to the commercial ewe flock and was representative of ewe management practices in the region (normal-practice flock; n = 464). At lambing, the condition score of the Lifetimewool flock was 0.7 condition scores units greater than the normal-practice flock. Ewe clean fleece weight and fibre diameter were greater in the Lifetimewool flock and their lambs had higher survival rates to weaning. Over three shearings, progeny from Lifetimewool ewe flocks produced more clean wool (P < 0.0001) but there was no consistent effect on fibre diameter, staple length or staple strength. Twin-born lambs from ewes managed to Lifetimewool guidelines had a similar liveweight and produced similar quantity and quality of wool to single-born lambs managed to Lifetimewool guidelines, but still suffered higher rates of mortality to weaning. This suggests that it is possible to manage ewes pregnant with twins to ensure that their surviving progeny perform at a level similar to single-born progeny managed under similar targets.