Foraging behaviour of beef heifers and ewes in natural grasslands with distinct proportions of tussocks

Bremm, Carolina; Laca, Emilio A.; Fonseca, Lidiane; Mezzalira, J. C.; Elejalde, Denise Adelaide Gomes; Gonda, Horacio Leandro; Carvalho, Paulo César de Faccio

doi:10.1016/j.applanim.2012.08.008

Cited by 32 publications

(31 citation statements)

References 35 publications

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“…However, this is a misconception as it does not consider long‐term production sustainability, and mostly results from a poor understanding of the real use of tussock formations by cattle. Up to a moderate proportion, tussocks do not reduce individual animal performances (Bremm et al., ; Trindade et al., ). However, very low grazing intensity effectively reduces animal production per hectare (Cruz et al., ), once the levels of forage allowance are too high to be consumed by the small number of animals in the paddock.…”

Section: Discussionmentioning

confidence: 99%

“…Grazing can influence species distributions in plant communities by selective and differential removal of plant parts or species (Díaz et al., ; Milchunas et al., ; Zheng et al., ), trampling, and urine and dung deposition (Lezama & Paruelo, ; Weeda, ). The effect of grazing, considering all these associated factors, is not homogeneous across the landscape, as herbivore foraging is selective (Bailey et al., ) and selectivity can be affected by forage availability and by heterogeneity in the physical environment (Bremm et al., ).…”

Section: Introductionmentioning

confidence: 99%

“…Further, cattle selectivity and heterogeneous grazing behaviour (Bremm et al., ) affect vegetation patterns in a distinct way across the landscape, so that the effect of grazing disturbance depends on the observation scale (Chaneton & Facelli, ; Dorrough, Ash, Bruce, & McIntyre, ). In small patches, grazing disturbance might increase species richness, by decreasing competitiveness and allowing new species colonization (Adler, Raff, & Lauenroth, ; Dorrough et al., ).…”

Section: Introductionmentioning

confidence: 99%

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Long‐term effects of grazing intensity on strategies and spatial components of functional diversity in subtropical grassland

Fischer

Bonnet

Cezimbra

et al. 2019

Applied Vegetation Science

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Question: How does grazing intensity affect plant community functional traits and the spatial components of functional diversity in subtropical grasslands?Location: Long-term cattle grazing management experiment in subtropical Campos grassland, southern Brazil. Methods: Fourteen experimental units (paddocks) maintained under seven grazingintensity treatments for 26 years. In each paddock, we recorded plant species cover and species functional traits in nine systematically located plots of 1 m 2 . Nineteen functional traits were used in the ordination of species to identify main axes of trait variation. Functional diversity measured by Rao entropy was partitioned into alpha, beta and gamma components. We tested, by linear models, for the effects of grazing intensity on community-weighted mean traits and functional diversity components, using as traits the species scores on the PCA axes. Results:The two main axes of trait variation suggest a separation in species by their functional strategies (acquisition-conservation and tolerance-avoidance trade-offs).Acquisitive and tolerant species increased while conservative and avoidant species decreased with grazing intensity. Rao quadratic entropy, considering the three spatial components, decreased with grazing intensity, but this trend was more accentuated with beta-diversity. Conclusions:The long-term, strictly-managed grazing experiment allowed us to reveal the effect of not only grazing disturbance per se, but also of different grazing intensities. Under high grazing intensity, frequent and severe defoliation allows only the persistence of species similarly adapted to regrowth. Under low grazing intensity, the lack of frequent defoliation enables the development of species with high investment in strong and long-lived leaves. The partitioning of functional diversity revealed that the increase in functional diversity in areas with low grazing intensity is mostly due to an increase in heterogeneity among patches (beta-component). The double stratum vegetation structure: tussocks, which escape grazing control, and shortgrazed patches often overgrazed, is maintained by grazer selectivity.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Long‐term effects of grazing intensity on strategies and spatial components of functional diversity in subtropical grassland

Fischer

Bonnet

Cezimbra

et al. 2019

Applied Vegetation Science

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“…In Experiment 1, Gonçalves et al (2009) determined the relationship between inter-tussock sward heights (4, 8, 12 and 16 cm) on beef heifer intake rate in areas without tussocks. Bremm et al (2012;Experiment 2) evaluated the effect of controlled tussock-cover treatments (0%, 25%, 50% and 75%). Finally, in Experiment 3, Neves (2012) quantified short-term intake rate in representative subareas of the main FA experiment (4%, 8%, 12% and 16% BW).…”

Section: Short-term Experimentsmentioning

confidence: 99%

“…Bite depth was estimated as half of H (Cangiano et al 2002;Carvalho 2013). BkD (g/m 3 ) was estimated with an empirical model developed with data from short-term experiments (Experiments 1 and 2; Gonçalves et al 2009;Bremm et al 2012) as follows. First, an exponential decline of bulk density with horizon height, modulated by total sward height, was fitted to average horizon bulk density, as follows:…”

Section: Factors Explaining Adgmentioning

confidence: 99%

Can animal performance be predicted from short-term grazing processes?

Carvalho

Bremm²,

Mezzalira

et al. 2015

Anim. Prod. Sci.

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Despite all the biotic and abiotic factors affecting foraging by ruminants, there is a common and fundamental process, which is bite gathering. We hypothesised that because the mechanics of bite formation dominate the foraging process, changes in short-term bite mass are reflected in longer-term animal performance across a wide range of sward conditions. We focus at the meal level of foraging, using experiments in which the effect of abiotic factors and digestive constrains are minimised, making intake rate the main currency. We estimated bite mass across a wide range of structural challenges to large-herbivore foraging in a long-term experiment with heterogeneous native grasslands. A conceptual model was developed for average daily gain, where energy gain and energy costs were proximate causal variables. Energy gain was a function of diet quality and components of daily intake rate, where bite mass was the main component estimated. In turn, components of intake rate were determined by sward structure and bodyweight. Energy costs were a function of bodyweight and abiotic conditions. Finally, sward structure, bodyweight and abiotic conditions were determined by experimental treatments, seasons and years. Then, the conceptual model was translated into statistical models that included variables measured or estimated, and coefficients representing all links in the conceptual model. Weight gain was a function of bite mass, forage characteristics, and animal and abiotic conditions. Models were set up to test whether forage and stocking conditions affected monthly gain beyond the effects through bite mass, after correcting for abiotic factors. Forage mass, height and disappearance did help predict monthly gain after bite mass was included in the model, which supported our hypothesis. However, stocking treatments and season had significant effects not incorporated in bite mass. Although the model explained 77.9% of liveweight gain variation, only 35.2% was due to fixed effects, with 10.8% accounted by bite mass and its interactions. Concomitant experiments showed that sward structure (first with sward height and the second with tussock cover) does determine bite mass and short-term intake rate in the complex native grasslands we studied. Yet, other temporal varying components of monthly gain not correlated with bite mass, temperature or wind, added most of the observed variation in monthly animal performance. Part of the model failure to account for variation in performance may be related to a significant and temporally variable grazing of tussocks. We used a bite mass model that assumed no tussock grazing. In light of these results and a parallel experiment, we conclude that tussock grazing must be incorporated in future versions of the model.

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Plant‐Herbivore Interactions

Sollenberger

Wallau

2020

Forages

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Foraging behaviour of beef heifers and ewes in natural grasslands with distinct proportions of tussocks

Cited by 32 publications

References 35 publications

Long‐term effects of grazing intensity on strategies and spatial components of functional diversity in subtropical grassland

Long‐term effects of grazing intensity on strategies and spatial components of functional diversity in subtropical grassland

Can animal performance be predicted from short-term grazing processes?

Plant‐Herbivore Interactions

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