Journal Articles
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Item Measuring Herbage Mass: A Review(MDPI (Basel, Switzerland), 2025-10-01) Susruthan V; Donaghy DJ; Kenyon PR; Sneddon NW; Cartmill AD; Bellocchi GThe accurate measurement of herbage mass is essential for feed budgeting and the management of sustainable and profitable grazing systems. There are many techniques available to estimate herbage mass in pastoral systems, and these vary in accuracy, cost, and time taken to implement. In situ and remote sensing techniques are both associated with moderate to high error, as herbage mass is affected by a number of dependent and independent factors, including sward composition, soil structure, chemical characteristics and moisture levels, climatic conditions, and grazing management, which must be considered in the development of an accurate local calibration model for precise estimation of herbage mass. This review provides an overview of commonly used herbage mass assessment techniques and describes their limitations, synergies, and trade-offs, and also covers the integration of new technologies which have the potential to monitor pastures at scale. This review highlights the need for further research and to integrate new technologies for accurate and precise measurement of herbage mass, noting the lack of calibration with in situ methods, the need for development of new protocols for assessment, variance in equipment and software compatibility, and the need to evaluate the effectiveness of methods/techniques on a variety of livestock operations for extended periods.Item Increased growth rate post-weaning affects mammary gene expression of two-year-old ewes during their second pregnancy and lactation(Oxford University Press on behalf of the American Society of Animal Science., 2025-09-18) Haslin E; Herath HMGP; Pain SJ; Gedye KR; Sneddon NW; Wang B; Heiser A; Corner-Thomas RA; Kenyon PR; Morris ST; Blair HTThis study examined the long-term effects of increased growth rates between three and seven months of age on gene expression in the mammary gland of nondairy ewes during their second lactation. A total of 19 twin-bearing, two-year-old ewes that either had an increased growth rate between three and seven months of age (heavy; n = 9; 153 ± 2.2 g/d and 47.9 ± 0.38 kg at breeding) or did not have an increased growth rate (control; n = 10; 127 ± 1.9 g/d and 44.9 ± 0.49 kg at breeding) were selected. Mammary gland biopsies were collected at day 128 of pregnancy and day 30 of lactation to examine the expression of 37 genes involved in mammary cell development and milk fat metabolism using NanoString nCounter technology. Ewes in the heavy group tended to exhibit lower expression (P < 0.05) of acyl-CoA synthetase short-chain family member 1 (ACSS1), a gene critical for mitochondrial acetyl-CoA synthesis, energy production, and milk fat synthesis, and a trend toward (P = 0.11) lower expression of signal transducer and activator of transcription 5A (STAT5A), a regulator of mammary epithelial cell differentiation and survival. These lower expressions suggest potential carry-over effects of increased growth rate between three and seven months of age. However, no phenotypic differences were observed in lamb growth or live weight, and no differences were detected in the expression of downstream target genes or modulators of these pathways, suggesting limited functional impact on mammary gland development and lamb performance outcomes. Further investigations, including a functional assessment of lactation and use of comprehensive transcriptomic analyses, would be needed to understand the effects of increased growth rates between three and seven months of age on ewe mammary function and milk composition.Item An assessment of the accuracy of morphological techniques for identifying Lucilia cuprina and Lucilia sericata (Diptera: Calliphoridae)(Taylor and Francis Group on behalf of the New Zealand Veterinary Association, 2025-10-13) Brett PTJ; Lawrence KE; Kenyon PR; Gedye K; Fermin LM; Pomroy WAims: To assess the accuracy of the morphological identification of Lucilia cuprina and Lucilia sericata by using molecular analysis as a reference standard test, and to describe the seasonality of these species. Methods: A convenience sample of L. cuprina and L. sericata flies was caught on eight farms from across New Zealand and stored at room temperature in 70% alcohol. They were first morphologically identified using published keys and then molecularly identified using primers to amplify the 28S rRNA region of the nuclear genome. The accuracy of the morphological identification was then estimated for each species using the molecular identification as a reference standard test. The correctness of the published keys was also tested by re-examining a sample of misidentified flies using enhanced magnification and photography. Results: The accuracy of the morphological identification for L. cuprina was 0.66 (95% CI = 0.58–0.73) and for L. sericata was 0.7 (95% CI = 0.62–0.77). There was no evidence for a difference in accuracy between species (p = 0.56), and re-examination of the misidentified flies found no faults in the published keys. The study confirmed that L. cuprina has a longer season of activity than L. sericata. Conclusions: These results emphasise the need to use molecular methods to confirm the identification of these species, especially when dealing with large, stored collections, rather than to rely on morphological identification alone. Clinical relevance: Without accurate fly identification and knowledge of insecticide resistance status, effective control and prevention of flystrike in New Zealand could be handicapped.Item The economic optimum mob size at lambing for triplet-bearing Maternal and Merino ewes across southern Australia(CSIRO Publishing, 2025-01-16) Young JM; Kenyon PR; Kubeil LJ; Thompson AN; Trompf J; Lockwood A; Greer AContext: Lambing triplet-bearing ewes in smaller mobs significantly increases lamb survival. Aims: This paper reports economic analysis to assess the optimum mob size for triplet-bearing ewes during lambing. Methods: The analyses considered scenarios for Merino and non-Merino (Maternal) flocks where producers subdivided lambing paddocks using permanent fencing or where ewes were re-allocated within existing paddocks on the basis of pregnancy status. Key results: The optimum mob sizes for triplet-bearing ewes during lambing were affected by ewe breed, stocking rate, lamb price and the target return-on-investment if subdividing paddocks. The optimum mob size for triplet-bearing Maternal and Merino ewes was between 27% and 40% of the optimum for twin-bearing ewes and this was similar for scenarios where paddocks were subdivided, or where ewes were re-allocated within existing paddocks. At the standard lamb price of AUD$7/kg carcass weight, the economic return from adjusting the relative mob size of triplet-bearing ewes was AUD$2.05 per multiple-bearing or AUD$14.20 per triplet-bearing Maternal ewe and AUD$0.54 per multiple-bearing ewe or AUD$5.70 per triplet-bearing Merino ewe. Conclusions: Overall, these analyses demonstrated that reducing mob size at lambing can be a profitable strategy for improving survival of triplet-born lambs, depending on the current size of lambing mobs. Implications: As reported previously for single- and twin-bearing ewes, it is difficult to provide generic recommendations to producers for the optimum mob size of triplet-bearing ewes at lambing because optimum mob size was dependent on several enterprise-specific factors.Item A comparison of three nutritional models for estimating total metabolisable energy requirements for a ewe, beef breeding cow, lamb, and a calf/yearling in New Zealand's pasture-only system(Elsevier B V, 2025-09-01) Adjabui JA; Morel PHC; Morris ST; Kenyon PR; Tozer PRIn New Zealand (NZ), the metabolisable energy requirements (MER) of ruminants can be estimated using nutritional models from Nicol and Brookes (2017), CSIRO (2007), and NZ's Agricultural Inventory Model (AIM) of the Ministry for Primary Industries [MPI] (2022). The aim in this study was to calculate the total MER of a ewe, beef breeding cow, lamb, and a calf/yearling in a pasture-only system in NZ under the same assumptions to assess the extent and reasons for variations among the three commonly used nutritional models, and the implications for a given farm/s. The study utilised MER models from the three sources above using a factorial method. This method determines the MER for each physiological phase of an animal, to estimate total MER for each animal. The AIM (MPI 2022) model relative to Nicol and Brookes (2017), and CSIRO (2007) models respectively, estimated 13.4 % and 8.0 % higher MER for a ewe, 16.3 % and 16.6 % for a cow, 1.1 % and 2.0 % lower for a lamb, and 9.2 % and 9.2 % higher for a calf/yearling mainly due to a higher maintenance MER compared to the other models. This has implications for feed budgeting and stocking rates (SR) for a given farm, as the AIM (MPI 2022) model leads to a lower SR than the other two models for a given level of feed available. Energy balances and productivity could be negatively impacted if a model underestimates MER. This also yields different greenhouse gas (GHG) profiles, especially enteric methane, for a given farm and could potentially have financial consequences for farmers if an Emissions Trading Scheme was introduced. For consistency in ME estimates and GHG reporting, further research (feeding trials) is required to compare these model estimates to actual requirements of ruminants under NZ conditions. This could help identify the model that most accurately reflects MER for ruminants in the country.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 Characterisation of the nutritional composition of plant components of a herb-clover mix during November to May in New Zealand(New Zealand Society of Animal Production, 2019-07-01) Ekanayake WEMLJ; Corner-Thomas RA; Cranston LM; Hickson RE; Kenyon PR; Morris STAnimal performance on herb-clover mixes (containing plantain, chicory, red clover and white clover) can be inconsistent. Potentially this could be due to variation in botanical and nutritional composition of plant components affecting animal selectivity and, thus, performance. Herbage samples were collected monthly from November 2016 to May 2017, from 3 paddocks located at Massey University’s Keeble farm, Palmerston North, New Zealand. Quadrat-cut samples were used to determine the herbage mass and botanical composition. Hand-plucked samples of each plant components were analysed for the nutritional composition. The botanical composition of the herb-clover mix differed over time (P<0.05). The percentage of chicory stems increased (9.2 to 16.2%) and plantain stems decreased (14.7 to 1.0%, P<0.001). Overall, the crude protein and metabolisable energy of white clover, red clover, plantain and chicory leaves were higher (P<0.05) than those of plantain and chicory stems in each month except in November. These data indicate that a higher proportion of chicory and plantain stems in a herb-clover mix would reduce overall metabolisable energy and crude protein. This information can be useful for farmers to manipulate both the botanical and nutritional composition of herb-clover mix to optimise animal performance.Item Weaned lambs from different litter size submitted to contrasting feeding systems on tropical pastures(Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), 2025-05-30) Madruga AM; Poli CHEC; Tontini JF; Deiss L; Correa GF; Fajardo NM; Hampel VDS; Farias MDS; Kenyon PR; Moraes JCFThe objective of this work was to evaluate the performance and ingestive behavior of singleton and twin lambs after weaning under different feeding systems on tropical pasture. Studies were carried out over three years with castrated and weaned males of Texel x Corriedale lambs. In the first year, the treatments were: grass; grass and supplementation with concentrate (1.5% or 2.5% of live weight); grass and controlled legume grazing. In the second and third years, the treatments were: either grass or legume; mixed, this is, contiguous area of both grass and legume. On tropical pasture system, twin lambs fed with high levels of concentrate can gain more live weight than singletons, showing a compensatory growth and reaching the singletons live weight. Sheep litter size does not affect weaned lambs’ grazing behaviour under different feeding systems on tropical grassland. The use of concentrate supplementation changes lambs’ ingestive behavior by reducing grazing time and increasing idling time. Pigeon pea, as a monoculture or associated with grass, can be an important source of nutrients for lambs; however, it is not sufficient to ensure the same performance of twin and singleton lambs.Item Preferences in traits and management characteristics for dairy-beef animals from a survey of New Zealand farmers(Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2025-05-19) Sneddon NW; Corner-Thomas RA; Kenyon PR; Brier DThere are three parties involved in the expansion of dairy-beef or beef-on-dairy within New Zealand, they are namely, beef breeders, dairy farmers and beef finishers. Within these three groups, there are different requirements for an animal within each those industries. In 2022, Beef + Lamb New Zealand conducted a survey to collect responses from 121 respondents across these 3 parties, to gauge farmer preferences. The survey contained questions relating to the management of young cattle from birth through to weaning or sale (depending on management practice), and then from weaning or purchase through to finishing. All farmers were asked what traits they selected for in bulls, and what they based purchasing decisions on. The results showed a series of trends, related to breed choice, price and perceived benefit to their farming system. Calves from dairy cattle that had some Jersey genetics were seen as a finishing risk and were less attractive to finishing operations. There appeared to be a disconnect between the preferences of dairy and beef finishing operations, with sire selection having opposite selection criteria. The results of this survey indicate that work needs to be taken to align the goals of both beef finishers and dairy farmers.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.