Browsing by Author "Oliveira BA"

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18O isotopic labelling and soil water content fluctuations validate the hydraulic lift phenomena for C3 grass species in drought conditions
(Elsevier B.V., 2024-02-29) Oliveira BA; López IF; Cranston LM; Kemp PD; Donaghy DJ; Dörner J; López-Villalobos N; García-Favre J; Ordóñez IP; Van Hale R
Hydraulic lift is a functional characteristic observed in some plant species, often associated with their ability to withstand drought conditions. It involves capturing water from deep soil layers and redistributing it to shallower soil layers through the plant's roots. Bromus valdivianus Phil., Dactylis glomerata L., and Lolium perenne L. may perform hydraulic lift at varying rates. Using both direct (isotopic labelling - δ18O) and indirect (soil water content sensors) techniques, the study assessed and validated the hydraulic lift under extreme drought conditions on the soil top layer (below permanent wilting point), maintaining the bottom layer at high (20–25% filed capacity [FC]) and low (80–85% FC) levels of soil water restriction. Above- and below-ground biomass growth and morpho-physiological responses were evaluated. All species displayed some degree of hydraulic lift, with significant differences observed in the isotopic analysis and soil water content (p > 0.05). This illustrates that water was redistributed from the deep to shallower soil layer and validates that the hydraulic lift phenomenon is occurring in these C3 grasses. Bromus valdivianus presented the highest δ18O values (25.05‰) and highest increases in soil water content (µ=0.00626 m3 m−3; five events). Bromus valdivianus had a dry matter ratio of approximately 4:1 (0–20cm:20–40 cm). In contrast, L. perenne and D. glomerata had approximately 6:1 and 5:1, respectively. This difference in root morphology may explain the higher rate of hydraulic lift observed in B. valdivianus relative to L. perenne and D. glomerata. This paper validates the occurrence and provides initial insights into the hydraulic lift process occurrence of temperature grass species.
Animal behaviour and dietary preference of dairy cows grazing binary and diverse pastures under the leaf regrowth stage defoliation criterion
(Elsevier B.V., 2024-11-05) Oliveira BA; López FF; Cranston LM; Poli CHEC; Kemp PD; Donaghy DJ; Draganova I; López-Villalobos N
In New Zealand, intensively managed pasture-based dairy systems rely on binary pastures mostly comprised of Lolium perenne L. and Trifolium repens L. More frequent and extreme climatic events have been negatively affecting the persistency and production of these pastures, which now present increased seasonality, with marked peaks and troughs of production throughout the year. Diversification of plant species offers a solution to deal with increased seasonality. However, little is known about animal behaviour and dietary preferences of dairy cows grazing diverse pastures. The present study aimed to assess the grazing preferences of dairy cows when unrestrictedly offered binary (L. perenne and T. repens; Bi) and diverse pastures (L. perenne, Bromus valdivianus Phil., Dactylis glomerata L. and T. repens; Mix) subjected to three different leaf regrowth stage (LS) defoliation criteria. Secondarily, the study aimed to determine the main plant-related drivers for any potential animal preference. The treatments were MixLp (defoliated at L. perenne LS), BiLp (defoliated every time MixLp was defoliated), MixBv (defoliated at B. valdivianus LS) and BiBv (defoliated every time MixBv was defoliated), MixDg (defoliated at D. glomerata LS) and BiDg (defoliated every time MixDg was defoliated). Dairy cattle were evaluated over five agricultural seasons. The response variables were grazing time and location, bite rate, animal behavioural activity, pre-grazing herbage mass, undisturbed sward height, lamina:stem ratio, crude protein, metabolisable energy, organic matter digestibility, non-structural carbohydrates, neutral detergent fibre and lignin. Where significant differences were found, binary pastures presented lower sward height and higher non-structural carbohydrate content in comparison to the diverse pastures under the same LS defoliation criteria. However, no significant differences were found in the percentage of time that cows spent grazing both pastures. Season was the greatest contributor to the proportion variation found in all response variables, with values ranging from 47.55 % up to 88.77 %. In winter and spring, cows modulated their grazing behaviour (proportional time spent grazing, ruminating, or idling), investing more time actively grazing pastures under L. perenne LS interval of defoliation (2.5–3.0 LS), the criterion which resulted in shorter grazing rotations. This study allowed us to understand the suitability of diverse pastures from an animal perspective, and highlighted that independent of the pasture type, the positive productive and nutritional effects of defoliation management based on the LS may also extend themselves to positive outcomes in animal preference, interpreted as the percentage of time dairy cows spend grazing rather than ruminating or idling across and within seasons.
Productive and nutritional parameters in diverse pastures composed of complementary species (Lolium perenne L., Bromus valdivianus Phil., Dactylis glomerata L., and Trifolium repens L.) under the leaf regrowth stage defoliation criterion
(Elsevier B.V., 2026-01) Oliveira BA; López IF; Cranston LM; Kemp PD; Donaghy DJ; López-Villalobos N
The diversification of plant species within intensively managed pastures has been proposed as an alternative to conventional pure sward systems in an effort to address climatic-driven issues of pasture-based livestock production. In a diverse pasture composed of complementary species (DPCS), individual species fulfil different agroecological niches and complement each other. It is expected that DPCS have a greater capability to tolerate and perform under increasingly extreme climate events; however, appropriate grazing management strategies for diverse pastures still need to be fully elucidated. In the present study, DPCS comprised Lolium perenne L., Bromus valdivianus Phil., Dactylis glomerata L., and Trifolium repens L. The leaf regrowth stage [LS; L. perenne (2.5–3.0LS), B. valdivianus (3.5–4.0LS) and D. glomerata (3.5–4.0LS)] is proposed to be an applicable method of defoliation management for DPCS due to a potential overlapping of their optimal defoliation intervals. The productive, morpho-physiological, and nutritional parameters of DPCS and their respective single-grass and T. repens pastures were assessed for two years under the LS criterion for defoliation. Within the DPCS, the three grass species presented a temporal overlapping of their respective LS intervals. Significant differences were found in the dry matter seasonal accumulation; DPCS exhibited seasonal asynchronous growth among species and presented an enhanced ability to withstand the ingress of volunteer species. In all pastures, the nutritional parameters were mostly influenced by season and LS criterion. Lolium perenne, B. valdivianus, and D. glomerata were shown to be complementary grass species, presenting growth asynchrony and an overlapping defoliation interval that optimised production. In this study, grazing management that focuses on the morpho-physiological development of grasses within a diverse pasture was successfully applied, with B. valdivianus LS optimal interval for defoliation being the most appropriate criterion for determining a grazing regime for DPCS.