Ewe Hoggets Research Articles

Where do all the ewes go? Ewe culling and mortality in 34 sheep flocks in New Zealand

ABSTRACT Aims To describe rates of and reasons for culling and mortality of ewes between breeding and mid-lactation on New Zealand sheep farms; to investigate associations of these variables with farm demographic variables; and to describe rates of and reasons for culling of ewes at weaning. Methods Participants were a convenience sample of 34 farms from across New Zealand. Demographic data were initially collected for each farm via a questionnaire administered in-person to the flock owner or manager. During approximately 8 months from breeding to mid-lactation, ewe tally, culling and mortality data were collected and used to calculate various parameters related to flock performance and to investigate associations. During the main ewe-culling event at weaning, ewe-culling data were collected from 29/34 flocks participating in the study. Results There was considerable variation between flocks, but the between-flock mean replacement percentage was 29.2 (SD 5.0)%. Overall, a between-flock mean of 10.5 (SD 4.6)% of ewes presented for breeding were culled or dead/missing by mid-lactation and thus did not rear any lambs. Additionally, from 27 flocks that reported data on ewes’ success at rearing lambs, a between-flock mean of 3.9 (SD 2.5)% of ewes that remained alive at mid-lactation failed to rear any lambs, resulting in an overall between-flock mean loss of 23.1 (SD 6.3) potential lambs per 100 ewes. Two-thirds of ewe mortalities between breeding and mid-lactation occurred during the lambing period. Model results showed flocks with higher pregnancy scanning percentages had lower rates of culling and mortality between breeding and mid-lactation. However, apart from farm contour, from breeding to mid-lactation there were no associations for culling and mortality with farm size, flock size, number of ewes per labour unit, whether ewe hoggets (7–9 months of age) were presented for breeding, or duration of the breeding period. A between-flock mean of 16.5 (SD 8.3)% of ewes present at weaning were culled, and among mixed-age ewes, the most common reasons for culling at this time were age, incisor teeth defects and udder defects. Conclusions To reduce unnecessary ewe culling and mortality, attention should be focused on maximising conception rates, ensuring judicious culling decisions, optimising body condition score, and identifying farm-specific causes of death over the lambing period to facilitate targeted intervention strategies. Clinical relevance Identifying why and when ewes exit flocks, and comparing it with the data presented here, will facilitate the development of flock-specific interventions to reduce ewe culling and mortality. Abbreviations BCS: Body condition score; NI: North Island; SI: South Island

Evaluation and use of recently introduced sheep breeds to Uruguay

Sheep numbers in Uruguay have declined over the last 30 years. In the north and northeast there are extensive wool and dual-purpose systems, respectively, where both wool and meat impact on income. In the south, small-scale family sheep meat production systems have flourished. In this thesis I report work pertaning to production systems in the south (1) and northeast (2) regions. Corriedale (C) is the predominant breed in the country. Milchschaf (M) has been disseminated in the south but C still prevails in the northeast. There is a paucity of rigorous evaluations of these breeds or alternatives that could be more profitable, such as Highlander (H) for the south and Dohne Merino (DM) for the northeast. I experimentally assessed: in 1), wool production, reproduction and growth in C, H and M, and in 2), wool quality and body traits in ewe hoggets from rotational crossbreeding between C and DM. In 1), wool production was better in C, but H and M outperformed C in live weight and reproductive performance. In 2), genotypes with greater proportions of DM produced lower fleece weight, and those with greater proportions of C produced coarser fibre diameter, with no differences in wool quality or morphological traits related to meat aptitude. Gross margins (GM) integrate physical performance with product values and costs, allowing monetary comparison between genotypes. I calculated GMs for a number of production and market scenarios. In 1), most often GM was greatest for H, followed by M. The differences in favor of H and M over C decreased when I considered higher feed requirements for H and M. The GM of H and M increased by assuming they were wool-less (the cost of harvesting exceeds the value of the wool produced). In 2), I considered low and high prices for wool of different fibre diameter. GM was greatest for ¾DM and ⅝DM at low prices, and for ¾DM and ½DM at high prices. C had the lowest GM in all scenarios. I recommend H for southern systems and research on hair sheep breeds. In extensive dual-purpose systems, rotational crossbreeding between C and DM allows for improved wool income without losing meat potential. I formulate recommendations about future genotype evaluations, integrating them with current within breed genetic evaluations.

PRODUCTION AND ECONOMIC EVALUATION OF THE CORRIEDALE BREED AND CROSSES WITH DOHNE MERINO GENERATED DURING THE ESTABLISHMENT OF A ROTATIONAL CROSSBREEDING SCHEME: EWE HOGGET RESULTS

Corriedale (C) is the predominant sheep breed in Uruguay, but prices for its medium fineness wool have been low. Dohne Merino (DM) has attracted interest because it has similar attributes to C, but finer wool. We evaluated wool and body traits of crossbred ewe hoggets generated during the establishment of a rotational crossbreeding scheme between C and DM. The program started with 400 C ewes. The first year 100 C ewes were mated to C rams, and the rest were mated to DM. Purebred C progeny were always mated to C rams. The crossbred progeny was randomly divided into two equal groups, one of which was mated to C rams and the other to DM rams. Subsequent progenies were mated to rams of the opposite breed to its sire. Performance was recorded from 2015 to 2020 in the ewe hoggets. Gross margin (GM) was calculated for each genotype. Differences among genotypes for subjectively assessed wool quality traits were non-significant. Genotypes with a greater proportion of C had higher fleece weight, whereas those with a greater proportion of DM had lower fibre diameter. Pure C had the lowest post-shearing live weight whereas DM C had the highest. Pure C had the lowest GM for the scenarios investigated (low and high wool price, adjustment for greater feed intake of heavier hoggets). Rotational crossbreeding takes advantage of the complementarity between these two breeds, allowing a rapid enhancement of the C producers’ income from wool without compromising the meat-producing attributes of the breed. The advantage could be greater by implementing some simple selection strategies.

Factors Associated with Mortality of Lambs Born to Ewe Hoggets.

Simple SummaryPre-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.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.

The effects of divergent selection for reproduction and sex on quantitative and qualitative slaughter traits in Merinos

The impact of selection of sheep for reproduction on meat traits are not evident, while genetic parameters for meat traits is absent for South African pure breeds. Quantitative and qualitative meat traits were therefore studied in progeny of two Merino selection lines that were divergently selected for number of lambs weaned per ewe joined (NLW) since 1986. The historic divergent selection resulted in two lines (High (H) and Low (L)) differing widely for NLW. Slaughter data were recorded during the routine slaughter of surplus 14-month-old ram and ewe hoggets from these lines and assessed for selection line and sex. Single-trait heritability estimates were derived for meat traits by average information restricted maximum likelihood methods. Depending on the trait, data were available for between 340 and 576 animals that were recorded between 2015 and 2018. Hoggets from the H line were heavier than their L line contemporaries, with a slightly lower ultimate pH after 48 h in the cooler and slightly darker meat. H line ewes had, on average, redder meat than the other selection line x sex groups. Single-trait heritability estimates amounted to 0.44 ± 0.16 for slaughter weight, 0.63 ± 0.15 for carcass weight, 0.34 ± 0.15 for dressing percentage, 0.25 ± 0.11 for fat depth at the 13th rib, 0.29 ± 0.11 for fat depth at the rump, 0.12 ± 0.11 for ultimate pH, 0.32 ± 0.12 for lightness, 0.11 ± 0.09 for redness, 0.04 ± 0.06 for yellowness, 0.05 ± 0.08 for cooking loss and 0.06 ± 0.07 for drip loss. Parameter estimates for initial pH and shear force of the meat went to the boundary of parameter space and were not estimable. It was concluded that selection for NLW did not compromise any of the meat traits and that most quantitative meat traits were heritable and variable, making selection for improvement of these traits feasible. Additional research is indicated on the qualitative meat traits studied.

Preliminary Investigation into a Novel Sustained-Release Formulation of Meloxicam in Sheep (Ovis aries)-Pharmacokinetic Profile.

Simple SummaryMeloxicam is an effective non-steroidal anti-inflammatory drug (NSAID) suitable for ameliorating pain in sheep. Pain caused by husbandry procedures and other inflammatory conditions in sheep can persist for an extended time beyond the duration of action of currently available formulations of NSAIDs. This study investigates a novel sustained-release formulation of meloxicam to determine its potential for extended pain alleviation. Compared to a conventional formulation of meloxicam, the sustained-release formulation provided extended half-life making it a suitable candidate for providing extended pain relief.This study is a preliminary investigation describing the pharmacokinetic profile of a novel subcutaneous sustained-release meloxicam formulation (SRMF) in sheep. Six merino ewe hoggets (41.5 ± 4.6 kg) were treated with a novel subcutaneous SRMF at 2 mg/kg bodyweight (BW). Blood samples were collected at t = 0, 2, 4, 6, 8, 10, 12, 24, 48, 96, 144, 168, 192, and 336 h following treatment, and interstitial (ISF) fluid samples were collected at periods of 8 to 12 h, 12 to 24 h, 24 to 48 h, 48 to 52 h, and 92 to 96 h following treatment. High-pressure liquid chromatography (HPLC) analysis with ultraviolet detection was utilised to determine the concentration of meloxicam in plasma and ISF. The SRMF exhibited the following mean (±SD) pharmacokinetic indices: Cmax of 1.58 μg/mL (±0.82 μg/mL) at a Tmax of 10.0 h (±1.79 h), and half life (t1/2) of 31.4 h (±13.17 h) in sheep plasma. Interstitial fluid samples were collected from three of the six sheep, with a decrease in meloxicam concentration exhibited over 52 h. This study demonstrates a variable extended t1/2, a delayed Tmax, and a lower Cmax of the SRMF, as compared to that of a conventional meloxicam formulation (CMF) in sheep, as previously referenced (t1/2: 14.28 h; Tmax: 5 h; Cmax: 15.94 μg/mL). Further research to determine the clinical efficacy and safety of the SRMF in sheep is warranted.

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.

206 Quantifying the effect of phenotypic factors on pedigree lamb performance using the Irish national database; Sheep Ireland

Abstract This study aimed to quantify the effect of phenotypic factors including birth type, rearing type, age at first lambing, lactation number and their interactions on pedigree lamb performance at 40days and 100days of age (weaning), where nutritional requirements were met at luxury levels. A dataset containing 644,330 lamb weight records from 2010–2017 were retrieved. Two datasets were created; 47,694 forty day weights (20–65 days of age and weighing 12-32kg) and 46,088 weaning weights (66–120 days of age and weighing 20-55kg). The PROC HPMIXED model (SAS 9.4) included gender, age, breed-class, contemporary group and interactions, i.e. birth type*rearing type, and lactation*age at first lambing, with dam as the random effect. At forty days and weaning respectively, lambs born and reared as singles weighed heaviest (20.95kg and 36.83kg) and lambs born and reared as triplets weighed lightest (16.83kg and 31.29kg). There was no difference between lambs born as twins and reared as twins and those born as triplets and reared as singles (18.11kg, 18.38kg and 33.00kg and 33.12kg). Lambs born as singles and reared as twins and those born as twins and reared as singles did not differ (19.01kg, 19.20kg and 34.30kg and 34.64kg), (Table 1, P < 0.01). In first and second lactation respectively, ewes that lambed for the first time as hoggets produced heavier lambs at forty days (18.12kg and 19.30kg) and at weaning (33.06kg and 34.58kg) than ewes who lambed as ewe lambs (16.88kg, 18.54kg and 31.40kg and 33.59kg). By third lactation, weights did not differ between progeny of ewes who first lambed as ewe lambs or hoggets (20.00kg, 19.41kg and 33.77kg and 34.64kg), (Figure 1 and 2, P < 0.05). In conclusion, rearing type significantly alters pedigree lamb performance at forty days and weaning regardless of birth type. By third lactation, production is similar regardless of age of first lambing.

The influence of three herbage types on the liveweight change of twin-bearing hoggets and their lambs

ABSTRACT The use of alternative herbage types such as herb-clover mixes and lucerne can improve the weaning weight of twin and triplet lambs born to mature ewes and single lambs born to ewe hoggets. The aim of this study was to compare the live weights of twin bearing ewe hoggets and their progeny grazed on either ad libitum permanent pasture (ryegrass white clover), lucerne or plantain-clover during lactation over two years. In both years of the study, twin bearing hoggets and their lambs grazed on lucerne or plantain-clover were heavier at weaning than those on pasture. Lambs grazed on lucerne had greater live weights at weaning than plantain-clover, however, among ewe hoggets differences were seen only in the first year of the study. In conclusion, both lucerne and the plantain-clover resulted in increased mean live weights of ewe hoggets and their lambs at weaning compared with those on pasture.

Sheep from low-methane-yield selection lines created on alfalfa pellets also have lower methane yield under pastoral farming conditions1,2

Selection lines of sheep with low and high CH yield (g/kg DMI; CH/DMI) are being developed on the basis of feeding pelleted alfalfa hay at 2.0 times maintenance ME requirements in respiration chambers, but their divergence under predominant grazing conditions, as in New Zealand, is not known. The objectives of this study were to determine CH emissions and rumen fermentation characteristics in sheep from low and high CH/DMI selection lines while grazing pasture. Two grazing experiments were conducted with 42 selection line ewes in March 2013 (Exp. 1) and 98 selection line progeny ewe hoggets in October/November 2014 (Exp. 2), with CH emissions estimated by the SF tracer technique and DMI estimated by titanium oxide in combination with natural long-chain -alkanes. Total daily CH production (g/d) was similar between high and low CH/DMI selection line sheep in Exp. 1 and lower for low CH/DMI progeny compared with high CH/DMI progeny in Exp. 2 ( < 0.05). The CH/DMI tended to be 20% lower for low CH/DMI line sheep compared with high CH/DMI selection line sheep in Exp. 1 ( < 0.10) and was 15% lower for the low CH/DMI line in Exp. 2 ( < 0.01). Total VFA concentration and concentrations (m) of acetate, butyrate, and isobutyrate plus isovalerate were lower ( < 0.05) for low CH/DMI line sheep compared with high CH/DMI selection line sheep in both experiments. The current study indicates that differences in CH/DMI and VFA concentrations in selection line sheep, previously established on alfalfa pellets, are also present to a similar magnitude when grazing pasture.

Sheep from low-methane-yield selection lines created on alfalfa pellets also have lower methane yield under pastoral farming conditions.

Selection lines of sheep with low and high CH yield (g/kg DMI; CH/DMI) are being developed on the basis of feeding pelleted alfalfa hay at 2.0 times maintenance ME requirements in respiration chambers, but their divergence under predominant grazing conditions, as in New Zealand, is not known. The objectives of this study were to determine CH emissions and rumen fermentation characteristics in sheep from low and high CH/DMI selection lines while grazing pasture. Two grazing experiments were conducted with 42 selection line ewes in March 2013 (Exp. 1) and 98 selection line progeny ewe hoggets in October/November 2014 (Exp. 2), with CH emissions estimated by the SF tracer technique and DMI estimated by titanium oxide in combination with natural long-chain -alkanes. Total daily CH production (g/d) was similar between high and low CH/DMI selection line sheep in Exp. 1 and lower for low CH/DMI progeny compared with high CH/DMI progeny in Exp. 2 ( < 0.05). The CH/DMI tended to be 20% lower for low CH/DMI line sheep compared with high CH/DMI selection line sheep in Exp. 1 ( < 0.10) and was 15% lower for the low CH/DMI line in Exp. 2 ( < 0.01). Total VFA concentration and concentrations (m) of acetate, butyrate, and isobutyrate plus isovalerate were lower ( < 0.05) for low CH/DMI line sheep compared with high CH/DMI selection line sheep in both experiments. The current study indicates that differences in CH/DMI and VFA concentrations in selection line sheep, previously established on alfalfa pellets, are also present to a similar magnitude when grazing pasture.

Methane emissions changed nonlinearly with graded substitution of alfalfa silage with corn silage and corn grain in the diet of sheep and relation with rumen fermentation characteristics in vivo and in vitro.

Feeding grain and corn silage have been proposed as practices to reduce enteric methane (CH) emissions per unit of intake from ruminants, but the inclusion level required in the diet is normally not specified. The objectives of the current study were to determine the CH emission factor (g/kg DMI) of sheep fed alfalfa silage substituted with increasing levels of corn silage or corn grain at a fixed DMI level (2% of BW) and determine its relationship with rumen fermentation characteristics and microbial community composition and with in vitro fermentation characteristics of the same diets incubated using a standard laboratory method. Romney ewe hoggets (approximately 14 mo old; = 64) were randomly allocated to 8 dietary treatments, which included chaffed alfalfa silage alone or substituted with either 25, 50, 75 or 100% corn silage or 25, 50 or 65% rolled corn grain on a DM basis. After acclimatization to the diet, DMI and CH emissions were measured from individual sheep for 2 consecutive days in open-circuit respiration chambers and a rumen sample was collected at 3 h after feeding. The same diets were also incubated in an automated in vitro gas production system for 48 h using rumen liquid of fistulated nonlactating dairy cows grazing pasture. Increasing the substitution of alfalfa silage with corn silage or corn grain in the diet of sheep resulted in a quadratic response ( < 0.01) in CH emissions per unit of DMI (CH/DMI) with either supplement. For both supplements, CH/DMI increased in mixtures of up to 50% supplement inclusion and then decreased with greater supplement inclusion, especially with corn grain inclusion, but the level did not fall below that for 100% alfalfa silage. The ratio of acetate + butyrate to propionate + valerate and the propionate proportion alone in rumen liquid were the strongest single predictors for CH/DMI in the overall data set and explained 37.1 and 32.5%, respectively, of the variation in CH/DMI. Methanogens of (21.1% of total methanogens; = 0.247) and (10.7% of total methanogens; = -0.411) clades had weak to moderate correlations with in vivo CH/DMI. There was a weak quadratic relationship ( < 0.35) between in vivo CH/DMI and the in vitro parameters of gas and CH production and total VFA, whereas there was a moderate relationship ( = -0.50) between in vivo CH/estimated rumen degradable carbohydrates and in vitro CH/DM. In conclusion, CH/DMI changed in a nonlinear fashion with increasing supplement inclusion in the alfalfa forage diet when fed at 2% of BW to sheep; however, implications on predicting its influence on greenhouse gas emissions per unit of animal product, for whole farm emissions in life cycle analysis or total national emissions in the national inventories, should be determined.

Evaluation of perennial lupin/cocksfoot pasture relative to lucerne pasture under summer dry conditions

The productivity of a perennial lupin/cocksfoot mix was compared to that of lucerne in summer dry conditions at Lincoln University, Canterbury, New Zealand. The pastures were planted in December 2013 and rotationally grazed by ewe lambs in autumn 2014 (Year 1), and by ewe hoggets in spring-summer and ewe lambs in autumn of 2014/2015 (Year 2) and 2015/2016 (Year 3). For lupin/cocksfoot relative to lucerne in Years 1 to 3, sheep liveweight gains were 54% of 107 kg/ha, 68% of 1134 kg/ha and 50% of 1347 kg/ha; herbage dry matter yields were 122% of 3520 kg/ha, 64% of 10 230 kg/ha and 59% of 9680 kg/ha; and in Years 2 and 3, the water use efficiency of sheep liveweight gain was 76% of 2.0 kg/ha/mm and 49% of 2.7 kg/ha/mm, respectively. The lupin content in the pre-grazing herbage in Years 1 to 3 averaged 42, 22 and 12%, whereas the lucerne content averaged 78, 95 and 98%, respectively. This showed that perennial lupin was not persistent at this lowland site. Keywords: Lupinus polyphyllus, Dactylis glomerata, Medicago sativa, dryland, sheep liveweight gain, water use

How to optimise pasture production off uncultivatable hill country

Around 70 percent (guesstimate) of New Zealand's sheep and beef population is farmed on uncultivatable hill country. There are large areas where individual farms have less than ten percent available for cultivation. Wairere is such a property. Originally the southern end of the "seventy mile bush", the soils are poor, derived from sandstone and clay, with pHs of 4.9-5.2 and phosphorus (P) levels of 1-2. Following initial land clearing there were several rounds of reversion to Manuka until the mid 1960s when my father John embarked on a programme which included large inputs of lime, at 5 t/hectare, super at 1 t/hectare, and DAP at 100 kg/hectare, all flown on in the first 28 months. This programme took from 1965 to 1982. I personally spent nine months cutting scrub—more recently I have been a shareholder in a manuka honey company planting scrub, how things go round! This programme was accompanied by subdivision and provision of stock water by the construction of dams. There were invasions of porina and manuka beetle following development, and porina control is still required on a regular basis. Wairere has run performance recorded sheep since 1967, based on a registered Romney stud started by my grandfather in 1929. We winter around 9500 sheep and 340 cattle on 1070 effective hectares. The 5300 ewes wean 145 percent average; the 2000 ewe hoggets (all in lamb) wean around 1700 lambs. All hoggets have been mated for the past 50 years; the 1800-2000 ram hoggets are culled lightly in late winter, and taken through to private sale in November; the 300 cows (replacements bought in) calve from mid October, with most wearers sold in April.

Comparison between the reproductive performance of ewe hoggets and mature ewes following a progesterone-based oestrus synchronization protocol

Two experiments were conducted to compare the reproductive performance of ewe hoggets and mature ewes. All ewes were synchronized by an intravaginal progesterone-releasing device and bred together over a 5-day period. In Experiment 1, of those joined with the ram, more mature ewes ovulated (99% vs 68%; P < 0.05) with a higher ovulation rate (1.82 vs 1.14; P < 0.05) than ewe hoggets. Mature ewes had a higher pregnancy rate (98% vs 47%; P < 0.05) and lower early pregnancy loss (13% vs 41%; P < 0.05) than ewe hoggets. In Experiment 2, the ovulation rate (1.84 vs 1.44; P < 0.05) and pregnancy rate (86% vs 7%; P < 0.05) was higher in mature ewes compared with ewe hoggets. Combined, these studies help to quantify the difference in reproductive performance during breeding and pregnancy between ewe hoggets and mature ewes, and help to direct further research.

A heat challenge model for animal welfare assessment

The scientific study of livestock management issues that have a significant animal welfare component has long included the measurement of both behavioural responses and physiological effects. One of the recurring problems in this area of research is a failure to adequately link these 2 fields of measurement. In order to do this, a model is required that allows incremental increases of the intensity of the stressor so that adaptive reactions can be monitored at the different levels. Therefore, the aim of this experiment was to define the physiological effects of incremental changes in heat challenge, with the intention of developing a model whereby animal motivation to avoid certain levels of heat stress could be assessed. Merino ewe hoggets were randomly assigned to each of 4 levels of heat challenge (n = 12 for each treatment in 2 replicates of 6 animals): 20, 25, 30 or 35 o C with 70% relative humidity across all temperatures. Each animal underwent 2 weeks of habituation to pelleted feed and handling in an animal housing facility, followed by 2 weeks in climate controlled rooms (1 week baseline, 1 week heat challenge), and then 1 week of recovery back in the animal house. The sheep were catheterised and had intravaginal temperature loggers inserted that logged body temperature every 5 minutes during the baseline and heat challenge weeks. Feed and water intake was measured daily for all animals. Respiration rates were recorded twice daily during the heat challenge period. The data were analysed by analysis of variance using a linear model, with the baseline week used as a covariate.

Short communication: Divergent selection for reproduction affects dag score, breech wrinkle score and crutching time in Merinos

Merino lines that were divergently selected from the same base population from 1986 to 2009 for their ability to rear multiples were assessed for dag score in autumn and spring, breech wrinkle score, and crutching time. Animals in the Low (L) line had higher dag and breech wrinkle scores and took longer to be crutched than High (H) line contemporaries. Expressed relative to H line least squares means, means of L line individuals were respectively 54%, 65%, 42% and 40% higher for autumn dag score, spring dag score, breech fold score, and crutching time. Gender effects for dag score were inconclusive, as ewe hoggets were more daggy than rams in autumn, with an opposite trend in spring. Shearer (n = 6) also affected crutching times, with an almost twofold difference in mean crutching time from the quickest shearer (27.7 &#177; 3.1 seconds) to the slowest shearer (49.4 &#177; 3.7 seconds). The inclusion of dag score and breech wrinkle score as linear covariates in an analysis on crutching time eliminated the effect of selection line. It thus seems that the quicker crutching times of H line animals may be related to line differences for dag score and, to a lesser extent, for breech wrinkle score.Keywords: Reproduction, selection lines, shearing time, wrinkle

The management of risk in a dryland environment

A group of 24 Hawke's Bay hill country farmers are working with service providers to improve the resilience of their farming systems. An important step in the process was to undertake an inventory of their risk management strategies. Farmers were interviewed about their farming systems and risk management strategies and the data was analysed using descriptive statistics. There was considerable variation in the strategies adopted by the farmers to cope with a dryland environment. Importantly, these strategies had to cope with three types of drought and also upside risk (better than expected conditions), and so flexibility was critical. Infra-structure was important in managing a dryland environment. Farmers chose between increased scale (increasing farm size) and geographic dispersion (owning a second property in another location) through to intensification (investing in subdivision, drainage, capital fertiliser, new pasture species). The study identified that there may be scope for further investment in infra-structural elements such as drainage, deeper rooting alternative pasture species and water harvesting, along with improved management of subterranean clover to improve flexibility. Many of the farmers used forage crops and idling capacity (reduced stocking rate) to improve flexibility; others argued that maintaining pasture quality and managing upside risk was a better strategy in a dryland environment. Supplementary feed was an important strategy for some farmers, but its use was limited by contour and machinery constraints. A surprisingly large proportion of farmers run breeding cows, a policy that is much less flexible than trading stock. However, several farmers had improved their flexibility by running a high proportion of trading cattle and buffer mobs of ewe hoggets and trade lambs. To manage market risk, the majority of farmers are selling a large proportion of their lambs prime. Similarly, cattle are either sold prime or store onto the grass market when prices are at a premium. However, market risk associated with the purchase of supplements and grazing was poorly managed.

Effects of grazing willow fodder blocks upon methane production and blood composition in young sheep

A 79-day rotational grazing experiment was conducted over the summer and autumn of 2007 to compare effects of grazing willow ( Salix spp.) fodder blocks, a combination of small trees ( i.e., 1.0 m) and herbage, or perennial ryegrass ( Lolium perenne)/white clover ( Trifolium repens) control pasture on breath methane (CH 4) emissions, concentrations and solubility of CH 4 and sulphur hexafluoride (SF 6) tracer gas in blood, and haematology variables in young growing female sheep ( i.e., hoggets). Measurements of gases in blood followed a double equilibration technique with two ( n = 20) replicate per treatment. Ten ewe hoggets in each replicate were dosed on day 22 with intraruminal slow release SF 6 capsules, an inorganic tracer gas used to calculate CH 4 emissions. Breath samples were collected over 5-day periods in weeks 5 (period 1) and 11 (period 2). Total condensed tannin (CT) concentrations calculated in the diet selected by the willow fodder block sheep was 12 g CT kg/dry matter intake, with negligible amounts in control pasture hoggets. Compared to control pasture, grazing willow fodder blocks reduced CH 4 emission/kg metabolic body weight (BW 0.75) by 20% in period 1 ( P<0.01), but not in period 2. Blood CH 4 concentrations (ng/mL blood) were similar for both groups on day 36, but higher ( P<0.001) on day 76 for hoggets grazing willow fodder blocks, while a different trend was observed for SF 6 blood concentration being higher ( P<0.01) on day 36 in hoggets grazing willow fodder blocks, but similar in both groups on day 76. Repeatability of blood CH 4 concentration was 75% in period versus 84% in period 2. Methane and SF 6 Ostwald solubility coefficients in blood were similar in both periods for sheep grazing willow fodder blocks and the control pasture. Hoggets grazing willow fodder blocks had lower BW gain (65 g/day), carcass weight (16.1 kg) and carcass fatness (9.2 mm) than hoggets grazing control pasture (102 g; 18.3 kg; 11 mm). Hoggets dosed with SF 6 capsules had lower ( P<0.05) red blood cells, haemoglobin and haematocrit concentrations when grazing either willow fodder blocks or control pasture, while neutrophil ( P=0.063), platelet ( P=0.073) and monocyte ( P=0.072), white blood cell and total lymphocyte counts ( P<0.05) were higher for willow fodder block-fed hoggets than those fed the control pasture. Differences in the reduction in CH 4 emission between periods from grazing willow fodder blocks may be due to more willow leaf being eaten during the CH 4 measurement period in period 1 than in period 2.

The effect of the maturity and prior breeding activity of rams and body condition score of ewe hoggets on the reproductive performance of ewe hoggets

AIM: To determine the effect of age and prior use of mature rams at a given ram-to-ewe ratio, and the effect of body condition on breeding performance and pregnancy rate of ewe hoggets. METHODS: Ewe hoggets (n=733) aged 7–8 months were weighed and their body condition scored, then randomly assigned to one of three treatment groups (Day 0) and joined with either four two-tooth rams (20 months of age) not used previously (n=244; Two-tooth), four mixed-aged mature rams that had not been used earlier in the season (n=244; Mature-fresh), or four mixed-aged mature rams that had been used with mature ewes immediately prior to joining with hoggets (n=245; Mature-used). The breeding period was 34 days. Ewe hoggets were identified as having been marked during the first 17 days only, during both 17-day periods, during the second 17 days only, or not marked. Hoggets were re-weighed on Day 34, and pregnancy status determined using ultrasound on Day 92. The breeding soundness of the rams was assessed on Days −34 and −1. RESULTS: Semen samples obtained from the rams did not differ significantly in any of the parameters measured (p>0.05). Ewe hoggets joined with Mature-fresh rams were less likely (p<0.05) to be marked in the second 17 days of breeding only than those joined with either Two-tooth or Mature-used rams. No other breeding parameters were affected by breeding group (p>0.05). Hoggets marked in the first 17 days only were heavier (p<0.05) at Day 0 than those marked in the second 17 days only or not marked. Hoggets diagnosed as twin-bearing were heavier (p<0.05) than non-pregnant or single-bearing hoggets. Those hoggets marked in the first 17 days only had a greater (p<0.05) body condition score (BCS) than those marked in the second 17 days only or not marked at all. These differences were no longer apparent after correction for liveweight (LW).Correction for LW at Day 0 or change in LW during the breeding period did not affect the results for breeding performance. CONCLUSIONS: Under the conditions of this study, two-tooth rams and mature rams that had been used previously were just as suitable as mature rams that had not been used previously for breeding with ewe hoggets. Further studies are warranted to verify this result. The re-use of rams without reducing breeding performance would reduce breeding costs and may make breeding hoggets a more viable option for farmers. The BCS of ewe hoggets affected breeding performance, and can thus be used to identify those animals most suitable for breeding.