Journal Articles
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Item Heritability estimates and genetic and phenotypic correlations of skin thickness and skin temperature with key production traits in FocusPrime, Texel, Romney and Highlander sheep(Oxford University Press on behalf of the American Society of Animal Science., 2025-06-16) Graña-Baumgartner A; Dukkipati VSR; Biggs PJ; Kenyon PR; Blair HT; Pickering NK; Van der Linden DS; López-Villalobos NSkin thickness was found to be moderately heritable and genetically associated with lamb survival in a previous study on Romney sheep. The aims of this study were to estimate the heritabilities of skin thickness and skin temperature at around five and 11 months of age, and determine genetic and phenotypic correlations between them and with production traits such as fat depth, loin-eye muscle depth and width, live weights at weaning, scanning, and 12 months, and 12-month fleece weight, in FocusPrime (n=2,088), Texel (n=732), Romney (n=825) and Highlander (n=1,801) sheep breeds. Heritability estimates of skin thickness at 5-month old were moderate in FocusPrime (0.39 ± 0.12) and low in Texel and Highlander (0.11 ± 0.15 and 0.13 ± 0.09, respectively). Heritability estimates of skin thickness at 11-month old were moderate in all breeds (ranged from 0.19 ± 0.07 to 0.29 ± 0.15). Heritability estimates of skin temperature were high in FocusPrime (0.39 ± 0.11), low in Texel (0.17 ± 0.11) and Highlander (0.12 ± 0.06) and almost zero in Romney (0.04 ± 0.03). A tendency in all breeds for negative and favourable correlations was found between skin thickness and skin temperature at 11-month old sheep. Skin thickness at 11-months tended to have a positive genetic correlation with fat depth in all breeds except in Texel where the correlation tended to be negative (-0.10 ± 0.34). Genetic correlations of skin thickness at 11-month old with the weight traits were variate. There tended to be a positive correlation with weaning weight in Texel (0.14 ± 0.34) and Highlander (0.29 ± 0.22). However, there tended to be negative correlations with live weight at scanning and at 12-month of age in FocusPrime (-0.03 ± 0.18 and -0.13 ± 0.22 , respectively) and tended to be positive in Romney (0.09 ± 0.25 and 0.10 ± 0.24, respectively) and Highlander (0.26 ± 0.22 and 0.39 ± 0.21, respectively). Moreover, genetic correlations of skin thickness at 11-month of age with FW12 tended to be positive in both Romney (0.20 ± 0.22) and Highlander (0.55 ± 0.19). Further studies on the genetic correlations of skin thickness and skin temperature with lamb survival in these breeds are warranted.Item Are native shrubs a sustainable alternative to radiata pine on steep slopes? Insights using bioeconomic model for hill country farms in New Zealand(Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2025-05-07) Wangui JC; Millner JP; Kenyon PR; Pain SJ; Tozer PRLimited data on native shrubs has hindered direct comparisons with pine radiata as afforestation options for steep slopes on New Zealand hill country sheep and beef farms. This study updated a native shrub sub-model (NSM) with new research data and developed a radiata pine sub-model (RPM) for integration into a bioeconomic model using STELLA Architect. The model assessed asynchronous afforestation of 10% of effective farm area with either option, comparing impacts on feed supply, sheep dynamics, and farm economics. NSM was updated with growth curve, foliage biomass, and carbon stock data from two New Zealand sites. RPM used literature for growth curve, carbon, and log production data. Simulations included a pasture-only (base) and afforestation with either species at 10% and 20% planting rates. Native shrubs reduced feed supply by 2.5% and 4.0%, while radiata pine reduced it by 7.0% and 7.4% at 10% and 20% planting rates. Reduced feed led to smaller flocks and lower cash flow. Radiata pine generated surplus through carbon and log income, offsetting reduced sheep flock cash flow, while native shrubs did not. Carbon prices of 64.2 and137.4 NZD/NZU would be needed for viability in the best- and worst-case scenarios. Native shrubs are potential land use option on steep slopes but require policy intervention to lower establishment costs and carbon prices.Item Bioeconomic Modelling to Assess the Impacts of Using Native Shrubs on the Marginal Portions of the Sheep and Beef Hill Country Farms in New Zealand (article)(MDPI (Basel, Switzerland), 2021-10-18) Wangui JC; Kenyon PR; Tozer PR; Millner JP; Pain SJNew Zealand hill country sheep and beef farms contain land of various slope classes. The steepest slopes have the lowest pasture productivity and livestock carrying capacity and are the most vulnerable to soil mass movements. A potential management option for these areas of a farm is the planting of native shrubs which are browsable and provide erosion control, biodiversity, and a source of carbon credits. A bioeconomic whole farm model was developed by adding a native shrub sub-model to an existing hill country sheep and beef enterprise model to assess the impacts on feed supply, flock dynamics, and farm economics of converting 10% (56.4 hectares) of the entire farm, focusing on the steep slope areas, to native shrubs over a 50-year period. Two native shrub planting rates of 10% and 20% per year of the allocated area were compared to the status quo of no (0%) native shrub plantings. Mean annual feed supply dropped by 6.6% and 7.1% causing a reduction in flock size by 10.9% and 11.6% for the 10% and 20% planting rates, respectively, relative to 0% native shrub over the 50 years. Native shrub expenses exceeded carbon income for both planting rates and, together with reduced income from sheep flock, resulted in lower mean annual discounted total sheep enterprise cash operating surplus for the 10% (New Zealand Dollar (NZD) 20,522) and 20% (NZD 19,532) planting scenarios compared to 0% native shrubs (NZD 22,270). All planting scenarios had positive Net Present Value (NPV) and was highest for the 0% native shrubs compared to planting rates. Break-even carbon price was higher than the modelled carbon price (NZD 32/ New Zealand Emission Unit (NZU)) for both planting rates. Combined, this data indicates planting native shrubs on 10% of the farm at the modelled planting rates and carbon price would result in a reduction in farm sheep enterprise income. It can be concluded from the study that a higher carbon price above the break-even can make native shrubs attractive in the farming system.Item Determining the Impact of Hogget Breeding Performance on Profitability under a Fixed Feed Supply Scenario in New Zealand(MDPI (Basel, Switzerland), 2021-05-01) Farrell LJ; Kenyon PR; Tozer PR; Morris STHoggets (ewe lambs aged 4 to 16 months) can be bred from approximately 8 months of age for potentially increased flock production and profit, however most New Zealand hoggets are not presented for breeding and their reproductive success is highly variable. Bio-economic modelling was used to analyse flock productivity and profit in four sets of scenarios for ewe flocks with varying mature ewe (FWR) and hogget (HWR) weaning rate combinations. Firstly, hogget breeding was identified to become profitable when break-even HWRs of 26% and 28% were achieved for flocks with FWRs of 135% and 150%, respectively. Secondly, relatively smaller improvements in FWR were identified to increase profit to the same level as larger improvements in HWR. Thirdly, a high performing flock with FWR and HWR both ≥ the 90th percentile currently achieved commercially, was the most profitable flock modelled. Fourthly, a FWR was identified with which a farmer not wishing to breed hoggets could have the same profit as a farmer with a flock achieving current industry average FWR and HWR. Overall, the relative profit levels achieved by the modelled flocks suggest that more farmers should consider breeding their hoggets, though improvements in FWRs should be prioritised.Hoggets (ewe lambs aged 4 to 16 months) can be bred from approximately 8 months of age for potentially increased flock production and profit, however most New Zealand hoggets are not presented for breeding and their reproductive success is highly variable. Bio-economic modelling was used to analyse flock productivity and profit in four sets of scenarios for ewe flocks with varying mature ewe (FWR) and hogget (HWR) weaning rate combinations. Firstly, hogget breeding was identified to become profitable when break-even HWRs of 26% and 28% were achieved for flocks with FWRs of 135% and 150%, respectively. Secondly, relatively smaller improvements in FWR were identified to increase profit to the same level as larger improvements in HWR. Thirdly, a high performing flock with FWR and HWR both ≥ the 90th percentile currently achieved commercially, was the most profitable flock modelled. Fourthly, a FWR was identified with which a farmer not wishing to breed hoggets could have the same profit as a farmer with a flock achieving current industry average FWR and HWR. Overall, the relative profit levels achieved by the modelled flocks suggest that more farmers should consider breeding their hoggets, though improvements in FWRs should be prioritised.Item Genomic Regions Associated with Wool, Growth and Reproduction Traits in Uruguayan Merino Sheep(MDPI (Basel, Switzerland), 2023-01-07) Ramos Z; Garrick DJ; Blair HT; Vera B; Ciappesoni G; Kenyon PRThe aim of this study was to identify genomic regions and genes associated with the fiber diameter (FD), clean fleece weight (CFW), live weight (LW), body condition score (BCS), pregnancy rate (PR) and lambing potential (LP) of Uruguayan Merino sheep. Phenotypic records of approximately 2000 mixed-age ewes were obtained from a Merino nucleus flock. Genome-wide association studies were performed utilizing single-step Bayesian analysis. For wool traits, a total of 35 genomic windows surpassed the significance threshold (PVE ≥ 0.25%). The proportion of the total additive genetic variance explained by those windows was 4.85 and 9.06% for FD and CFW, respectively. There were 42 windows significantly associated with LWM, which collectively explained 43.2% of the additive genetic variance. For BCS, 22 relevant windows accounted for more than 40% of the additive genetic variance, whereas for the reproduction traits, 53 genomic windows (24 and 29 for PR and LP, respectively) reached the suggestive threshold of 0.25% of the PVE. Within the top 10 windows for each trait, we identified several genes showing potential associations with the wool (e.g., IGF-1, TGFB2R, PRKCA), live weight (e.g., CAST, LAP3, MED28, HERC6), body condition score (e.g., CDH10, TMC2, SIRPA, CPXM1) or reproduction traits (e.g., ADCY1, LEPR, GHR, LPAR2) of the mixed-age ewes.Item Productivity and Reproductive Performance of Mixed-Age Ewes across 20 Years of Selection for Ultrafine Wool in Uruguay(MDPI (Basel, Switzerland), 2021-08-01) Ramos Z; Blair HT; De Barbieri I; Ciappesoni G; Montossi F; Kenyon PRThis study reports the phenotypic trends for wool, growth, and reproductive traits in mixed-age ewes after twenty years of genetic selection. Data were obtained from the Merino nucleus flock in Uruguay between 1999 and 2020. Overall, the aim of this selection flock was to reduce the fiber diameter (FD) and increase both the clean fleece weight (CFW) and live weight (LW). Data on ewe wool traits, LW, body condition score (BCS), the total number of lambs weaned (TLW), and the total LW of lambs weaned (TWW) across all lambing opportunities (1–8 mating seasons) were analyzed. Between 1292 and 2063 ewes were measured, depending on the trait considered. Ewe FD decreased by approximately 3 µm (19–16 µm), whereas greasy fleece weight (GFW) increased by 0.2 kg. This improvement in wool traits was accompanied by increases in LW at mating (3 kg), decreases in BCS at mating (approximately by 1 unit), and a small positive change in TWW across years. This study demonstrated that increasing farmer income by selecting for finer wool, heavier fleeces, and heavier animals can be obtained without compromising ewe lifetime reproduction.Item Phenotypic Responses to Selection for Ultrafine Wool in Uruguayan Yearling Lambs(MDPI (Basel, Switzerland), 2021-02-22) Ramos Z; Blair HT; De Barbieri I; Ciappesoni G; Montossi F; Kenyon PRThis study evaluated the phenotypic trends for wool and growth traits of the fine Merino genetic nucleus in Uruguay. Data were collected from one-year-old lambs over a twenty-year period (1999–2018). The overall aim of the selection flock was to reduce fiber diameter with concomitant increases in fleece and live weights. Traits analyzed included fiber diameter (FD), greasy fleece weight (GFW), coefficient of variation of FD (CVfd), staple length (SL), scoured yield (SY), live weight post-shearing (LW), eye muscle area (EMA) and fat thickness (FAT). Data from approximately 5300 one-year-old male and female lambs were analyzed. During the study period, FD decreased by approximately 3 µm, whereas GFW and LW increased by at least 0.5 and 3.0 kg, respectively. There were interactions between the sex of the individual and the year for all wool traits. Except for FAT, all other traits were affected by the dam age. This study indicates that the selection program applied in the fine Merino genetic nucleus over a twenty-year period resulted in reductions in FD and increases in GFW and LW. Therefore, the results indicate it is possible to produce ultrafine wool in semi-extensive grazing systems without compromising other economically relevant traits in one-year-old lambs.Item Modelling a Transition from Purebred Romney to Fully Shedding Wiltshire-Romney Crossbred(MDPI (Basel, Switzerland), 7/11/2020) Farrell LJ; Morris ST; Kenyon PR; Tozer PRConsidering the current low prices for coarse wool (fibre diameter > 30 µm), a grading up transition to a shedding flock may eliminate wool harvesting costs and increase sheep farm profit. This transition could be achieved by breeding non-shedding ewes with Wiltshire rams. A bio-economic system-dynamics model of a pastoral sheep farming enterprise was used to simulate this grading up transition from 2580 Romney ewes to a similarly-sized flock of fully shedding third or fourth cross Wiltshire-Romney ewes. The total annual sheep feed demand was constrained within a ±5% range to minimise disruption to the on-farm beef cattle enterprise. Wool harvesting expenses were eliminated after seven years of transition, and with reduced feed demand for wool growth, the post-transition shedding flocks had more ewes producing more lambs and achieving greater annual profit compared with the base Romney flock. The net present values of transition were 7% higher than the maintenance of the base Romney flock with a farmgate wool price of $2.15/kg. Results suggest that coarse wool-producing farmers should consider a grading up transition to a shedding flock, and the collection of data on the production of Wiltshire-Romney sheep in New Zealand would improve the accuracy of model predictions.