Combining Marandu grass grazing height and supplementation level to optimize growth and productivity of yearling bulls

Abstract

Two experiments were conducted to determine the effects of grazing height and supplementation levels of Marandu pastures on average daily gain (ADG), gain per hectare (GPH) and methane (CH 4) emissions during the wet season under continuous stocking by Nelore yearling bulls. Exp. 1: three grazing heights were evaluated: 15, 25 and 35 cm, combined with 0.3% of BW of a supplement (161 g crude protein (CP)/kg and 20.1 MJ gross energy (GE)/kg on dry matter basis (DMB)). Experimental design was completely randomized (three paddocks per treatment), and the effects were analyzed by polynomial orthogonal contrasts. Exp. 2: grazing heights were combined with decreasing supplementation levels as grazing heights increased: short height (15 cm) and high supplementation (0.6% of BW of a supplement: 142 g CP/kg and 18.9 MJ GE/kg on DMB) (SHHS); moderate height (25 cm) and moderate supplementation (0.3% of BW of a supplement: 161 g CP/kg and 20.1 MJ GE/kg on DMB) (MHMS) or tall height (35 cm) without supplementation) (THWS). Experimental design was completely randomized (three paddocks per treatment), and treatment means were compared by Tukey test (P < 0.05). In Exp. 1, ADG increased linearly (P = 0.02), and GPH decreased linearly (P = 0.0002) as grazing height increased. Methane emission was not affected (P = 0.64) by grazing height. In Exp. 2, ADG was not influenced (P = 0.14) by treatments. However, GPH was the greatest (P < 0.0001) for the SHHS treatment. In addition, CH 4 emissions were lower (P < 0.0001) in SHHS and MHMS bulls compared to THWS. The SHHS Abbreviations: ADF, acid detergent fiber (expressed inclusive of residual ash); aNDF, neutral detergent fiber (assayed with a heat stable amylase and expressed inclusive of residual ash); ADG, average daily gain; AU, animal unit; BW, body weight; CP, crude protein; DM, dry matter; DMB, dry matter basis; DMI, dry matter intake; GPH, gain per hectare; ha, hectare; GE, gross energy; IVOMD, in vitro organic matter digestibility; IVDMD, in vitro dry matter digestibility; MHMS, moderate height and moderate supplementation; ME, metabolizable energy; OM, organic matter; SHHS, short height and high supplementation; THWS, tall height without supplementation.

Performance and methane emissions of Nellore steers grazing tropical pasture supplemented with lipid sources

“…These values are far higher than those found in this study. Barbero et al (2015) found emission values between 10.8 to 19.5 g/kg DMI in accordance with treatment (short height (15-cm grass grazing), high supplementation (0.6% of BW), or tall height (35-cm grass grazing), without supplementation).…”

Challenges of beef cattle production from tropical pastures

“…In Australia, high-cost supplements are often uneconomic and unless they are required within the growth path to a profitable end point, are best not used except for minimal low-cost supplements such as urea. In Brazil, where supplements are much cheaper and a wider range is available, the result appears be very different (Dórea, 2010;Detmann et al, 2014;Barbero et al, 2015;De Oliveira et al, 2016).…”

“…There has been a collation of data from Brazil (Dórea, 2010;Detmann et al, 2014;Barbero et al, 2015;De Oliveira et al, 2016) and these generally outline the same features: CP ranged from 3.4-21.0% and live weight gain ranged from −0.36-1.2 kg/day. Data from Brazil more closely aligned with that from the endowed zone of Queensland and not as harsh or challenging as that from the dry tropics of Australia.…”

“…McLennan (1997) defined the response to supplement type by season in northern Australia, Poppi et al (1997) collated responses to supplements for basal forages of high and low quality, and Dórea (2010), Detmann et al (2014), Barbero et al (2015), and De Oliveira et al (2016) collated or developed response curves over the wet and dry seasons of Brazil (Figure 5). …”

“…In Brazil, supplements seem to be used widely and at low levels and the basis for the response and need is not clear in all cases. Similarly, the basal pasture is of higher CP than the dry season in Australia or has a much shorter period when CP is low (Dórea, 2010;Detmann et al, 2014;Barbero et al, 2015;De Oliveira et al, 2016), and once again, the need for a supplement in all cases must be questioned. Winks and Laing (1972) showed that urea supplements did not increase live weight gain until faecal CP fell below 8% CP.…”