Supplement feed efficiency of growing beef cattle grazing native Campos grasslands during winter: a collated analysis.

Autor:	Cazzuli F; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Pasturas y Forrajes, Estación Experimental INIA Tacuarembó, Tacuarembó, Uruguay., Sánchez J; Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada., Hirigoyen A; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Forestal, Estación Experimental INIA Tacuarembó, Tacuarembó, Uruguay., Rovira P; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Carne y Lana, Estación Experimental INIA Treinta y Tres, Treinta y Tres, Uruguay., Beretta V; Animal Science Department, Universidad de la República, Paysandú, Uruguay., Simeone A; Animal Science Department, Universidad de la República, Paysandú, Uruguay., Jaurena M; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Pasturas y Forrajes, Estación Experimental INIA Tacuarembó, Tacuarembó, Uruguay., Durante M; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Pasturas y Forrajes, Estación Experimental INIA Tacuarembó, Tacuarembó, Uruguay.; Estación Experimental Agropecuaria Concepción del Uruguay, Concepción del Uruguay, Argentina., Savian JV; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Pasturas y Forrajes, Estación Experimental INIA Treinta y Tres, Treinta y Tres, Uruguay., Poppi D; School of Agriculture and Food Sciences, The University of Queensland, Gatton, Australia., Montossi F; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Carne y Lana, Estación Experimental INIA Tacuarembó, Tacuarembó, Uruguay., Lagomarsino X; FCA-UDE, Facultad de Ciencias Agrarias, Universidad de la Empresa, Montevideo, Uruguay., Luzardo S; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Carne y Lana, Estación Experimental INIA Tacuarembó, Tacuarembó, Uruguay., Brito G; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Carne y Lana, Estación Experimental INIA Tacuarembó, Tacuarembó, Uruguay., Velazco JI; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Carne y Lana, Estación Experimental INIA Treinta y Tres, Treinta y Tres, Uruguay., Bremm C; Grazing Ecology Research Group, Federal University of Rio Grande do Sul, Porto Alegre, Brazil., Lattanzi FA; Instituto Nacional de Investigación Agropecuaria (INIA), Programa Pasturas y Forrajes, Estación Experimental INIA La Estanzuela, Colonia, Uruguay.
Jazyk:	angličtina
Zdroj:	Translational animal science [Transl Anim Sci] 2023 Mar 10; Vol. 7 (1), pp. txad028. Date of Electronic Publication: 2023 Mar 10 (Print Publication: 2023).
DOI:	10.1093/tas/txad028
Abstrakt:	Supplementing growing cattle grazing native subtropical Campos grasslands during winter improves the low, even negative, average daily weight gain (ADG) typical of extensive animal production systems in Uruguay. Nonetheless, to render the practice profitable, it is crucial to control supplement feed efficiency (SFE), that is, the difference in ADG between supplemented and control animals (ADGchng) per unit of supplement dry matter (DM) intake. Little has been studied specifically on how SFE varies in these systems. The objective of this study was to quantify the magnitude and variation in SFE of growing beef cattle grazing stockpiled native Campos grasslands during winter and assess putative associations with herbage, animals, supplements, and climatic variables. We compiled data from supplementation trials carried out in Uruguay between 1993 and 2018, each evaluating between one and six supplementation treatments. The average ADG of unsupplemented and supplemented animals were 0.13 ± 0.174 and 0.49 ± 0.220 kg/animal/day, respectively. In both cases, ADG decreased linearly as the proportion of green herbage in the grazed grassland was lower, but the ADG of unsupplemented animals was further reduced when winter frosts were numerous. Estimated SFE were moderately high, with an average of 0.21 ± 0.076 ADGchng/kg DM, resulting from average ADGchng of 0.38 ± 0.180 kg/animal/day in response to an average supplementation rate of 1.84 ± 0.68 kg supplement DM intake/animal/day (0.86%  ± 0.27% body weight). No association was found between SFE and supplementation rate or type (protein vs. energy-based; P  > 0.05), but forage allowance negatively affected it, and herbage mass positively affected it, yet in a smaller magnitude, suggesting that a balance is needed between the two to maximize SFE. Weather conditions during trials affected SFE ( P  < 0.05), with greater SFE in winters with lower temperatures and more frosts. Daytime grazing time was consistently lower in supplemented animals compared to their unsupplemented counterparts, whereas ruminating time during the day was similar, increasing as the proportion of green herbage decreased. Herbage intake estimated from energy balance suggested the existence of some substitution effect. This agrees with the moderately high SFE and with the total digestible nutrients-to-protein ratio of these subtropical humid grasslands being higher than in semi-arid rangelands and dry-season tropical pastures but lower than in sown pastures. Competing Interests: None declared. (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.)
Databáze:	MEDLINE
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