Plasma Metabolites, Productive Performance and Rumen Volatile Fatty Acid Profiles of Northern Australian Bos indicus Steers Supplemented with Desmanthus and Lucerne

Abstract

The hypothesis tested was that tropical steers supplemented with the Desmanthus legume and lucerne, a widely characterized temperate legume of high nutritive value, would elicit similar responses in plasma metabolite profiles, productive performance, nitrogen retention, and volatile fatty acids (VFA). The tannin-binding compound, polyethylene glycol-4000 (PEG), was added to the diets (160 g/kg Desmanthus dry matter) with the objective of further exploring nitrogen (N) utilization in the animals supplemented with Desmanthus relative to lucerne. From February to June 2020, sixteen yearling Brangus steers (average liveweight of 232 ± 6 kg) were fed a background diet of Rhodes grass (Chloris gayana) hay for 28 days, before introducing three Desmanthus cultivars (Desmanthus virgatus cv. JCU2, D. bicornutus cv. JCU4, D. leptophyllus cv. JCU7) and lucerne (Medicago sativa) at 30% dry matter intake (DMI). Relative to the backgrounding period, all supplemented steers exhibited similar growth performance. Steers supplemented with Desmanthus recorded a lower DMI and animal growth performance, but higher fecal N concentration than animals supplemented with lucerne. Among the three Desmanthus cultivars, there were no significant differences in N concentrations, VFA, and plasma metabolite profiles. The addition of PEG induced higher rumen iso-acid concentrations and fecal N excretion. However, feeding Desmanthus spp. to tropical Bos indicus steers could be a valuable means of increasing N utilization, which is attributable to the presence of tannins, and, consequently, improve animal productive performance. Since supplementation with lucerne resulted in higher liveweight, daily liveweight gains, and overall animal performance than supplementing with Desmanthus, the tested hypothesis that both supplements will elicit similar animal performance does not hold and must be rejected. Further in vivo investigation is needed to better understand the impact of tannins in Desmanthus on N utilization.

Response to Climate Change: Evaluation of Methane Emissions in Northern Australian Beef Cattle on a High Quality Diet Supplemented with Desmanthus Using Open-Circuit Respiration Chambers and GreenFeed Emission Monitoring Systems

“…In JCU4, Suybeng et al [ 7 ] reported CP and NDF concentrations of 14.6 and 58.3% DM, respectively, after six weeks regrowth. The Desmanthus in our present study had a CP concentration of 10.3% DM and 13.0% DM for JCU2 and JCU4, respectively, and a NDF concentration of 57.5% DM and 53.1% DM for JCU2 and JCU4, respectively, after four to six weeks regrowth [ 26 ]. These data collectively demonstrate that the nutritive value of Desmanthus can vary widely depending on the cultivar/species, stage of growth, edaphic and climatic conditions.…”

“…The increase in DMI observed in the lucerne diet can be attributed to the higher digestibility of lucerne (65.2%) compared to Desmanthus spp. (49.6%) [ 26 ]. Kennedy and Charmley [ 48 ] reported an increase in both dry organic matter intake (DOMI) and CH 4 production in steers fed lucerne compared to cattle on tropical grasses such as speargrass ( Heteropogon contortus ), buffel grass ( Cenchrus ciliaris ), bisset grass ( Bothriochloa insculpta ), Mitchell grass ( Astrebla lappacea, Astrebla elymoides ), Rhodes grass ( Chloris gayana ) or tropical legumes such as Burgundy bean ( Macroptilium bracteatum ) or Stylo ( Stylosanthes hamata ).…”

“…The experimental design of Experiment 1 was described by Suybeng et al [ 26 ]. Briefly, a completely randomized block design was used to allocate sixteen yearling Brangus steers weighing 232 ± 6 kg on average, into four treatments of four animals each based on similar liveweight (LW).…”

“…A scanning monochromator (model 6500, NIRSystem, Inc., Silver Spring, MD, USA) was used to determine the chemical composition of the feed samples by near-infrared reflectance spectroscopy (NIRS) and calibration equations developed by CSIRO Agriculture [ 30 ] using ISI Software (Infrasoft International, Port Matilda, PA, USA) as described by Durmic et al [ 6 ]. Nutritive value of diets was presented in a previous paper [ 26 ] and are reported in Table 1 .…”

Genetics and nutrition impacts on herd productivity in the Northern Australian beef cattle production cycle

“…Northern Australian native pastures are characterized by poor nutritive value, low digestibility and high fibre content ( Suybeng et al., 2019 ; Suybeng et al., 2020 ; Suybeng et al., 2021a ; Suybeng et al., 2021b ). McCosker et al., (2020) monitored the reproductive performance of commercial northern Australia beef breeding herds and found that substantial opportunities to increase reproductive performance exist, if the causes of variation are able to be identified and alleviated.…”