Tropical beef cattle growth performance and meat quality in response to backgrounding on Desmanthus spp. pastures

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Experiment 1 evaluated the change in nutritive value and in situ degradability of desmanthus cultivars JCU2, JCU4 and JCU7 harvested at varying maturity stages to test the hypothesis that the nutritive value and in situ degradability of desmanthus differ between cultivars and with maturity stage at harvest, and was carried out in two stages: Stage 1 was a completely randomized study where desmanthus was harvested at 11, 38, 72 and 103 days of regrowth, separated into the leaf and stem portion, dried and analysed for dry matter and chemical composition. In Stage 2, ‘grab’ samples of desmanthus were harvested 78, 122 and 168 days after planting. Samples were dried and dry matter, crude protein and fibre degradation were determined using the in situ technique with three fistulated Droughtmaster steers in a randomized split-plot design with steers as the whole plots and cultivars as sub-plots. The degradability data was fitted to the Ørskov and McDonald (1979) equation using the SAS procedure (PROC NLIN). The statistical analysis was carried out using SAS version 9.4 and R version 4.0.1.

Experiment 2: The study aimed to evaluate the effect of desmanthus inclusion in buffel grass (Cenchrus ciliaris) pastures on the plasma metabolite profile and growth performance of grazing beef cattle during the dry season. Four hundred tropical crossbred steers were assigned to buffel grass only (n = 200) or buffel grass oversown with desmanthus (11.5% initial sward dry matter) pastures (n = 200) and grazed for 147 days during the dry season. Details of this study are published in Animals Journal (Link: https://doi.org/10.3390/ani11082355). After backgrounding 312 steers were finished on nutrient dense diets in the feedlot, slaughtered and graded in a commercial abattoir to determine the effect of desmanthus on carcass traits of beef cattle. Data were statistically analysed using the SAS software version 9.4 (SAS Institute, Cary, NC, USA).

In experiment 3, loin-eye muscle biopsies were collected from steers reported in the published journal article (PLoS ONE https://doi.org/10.1371/journal.pone.0260918) to determine the fat melting points and intramuscular fat composition of steers fed increamentental desmanthus proportions. Fat melting points were determined using the 'slip' point method and fatty acid composition was measured using the gas chromatography. Data were analysed using the SAS software version 9.4 (SAS Institute, Cary, North Carolina, USA). Details of this study were published in Metabolites Journal (https://doi.org/10.3390/metabo11120804).

Software/equipment used to create/collect the data: Automatic weighing scale (Gallagher 65 Scanlon Drive, Epping, Victoria 3076, Australia) Tub grinder (Roto Grind model 760, Burrows Enterprises, LLC, Greeley, CO, USA) Christy and Norris grinder (Christy Turner Ltd, Suffolk, England) Unity Spectrastar 2500X rotating top window system (Unity Scientific, Milford, MA, USA) Gas chromatography (Shimadzu Corporation, Kyoto, Japan) AU480 chemistry analyzer (Beckman Coulter, Inc. California, USA)

Software/equipment used to manipulate/analyse the data: SAS software version 9.4 (SAS Institute, Cary, North Carolina, USA) R software version 4.0.1. (R Foundation for Statistical Computing, Vienna, Austria)