Progressive inclusion of pearl millet herbage as a supplement for dairy cows fed mixed rations: Effects on methane emissions, dry matter intake, and milk production

Abstract

The inclusion of grazing in dairy feeding systems can improve animal welfare and reduce feed costs and labor for animal care and manure management. This work aimed to evaluate the effects of including pearl millet herbage (Pennisetum glaucum 'Campeiro') as a supplement for dairy cows fed total mixed rations (TMR). The treatments included 100% TMR offered ad libitum (control, TMR 100 ), 75% TMR ad libitum intake + access to grazing of a pearl millet pasture between the morning and afternoon milkings (7 h/d; pTMR 75 ), and 50% TMR ad libitum intake + access to grazing of a pearl millet pasture between the morning and afternoon milkings (7 h/d; pTMR 50 ). Nine multiparous Holstein and F 1 Jersey × Holstein cows were distributed in a replicated 3 × 3 Latin square design with 3 periods of 21 d (a 16-d adaptation period and a 5-d measurement period). Cows in the TMR 75 and TMR 50 groups stripgrazed a pearl millet pasture with pre-and postgrazing sward height targets of 60 and 30 cm, respectively. The herbage dry matter intake (DMI) increased with decreasing mixed ration supplies, and the total DMI decreased linearly from 19.0 kg/d in the TMR 100 group to 18.0 kg/d in the pTMR 50 group. Milk production decreased linearly from 24.0 kg/d in the TMR 100 group to 22.4 kg/d in the pTMR 50 group, and energy-corrected milk (ECM) production decreased linearly from 26.0 kg/d to 23.6 kg/d. Enteric methane (CH 4 ) emissions decreased linearly from 540 g/d in the TMR 100 group to 436 g/d in the pTMR 50 group, and CH 4 yields (g/kg of DMI) tended to decrease linearly. The CH 4 intensity was similar between treatments, averaging 20 g of CH 4 / kg of ECM. The inclusion of pearl millet herbage in the dairy cow diets decreased the total DMI and milk production to a small extent without affecting CH 4 intensity (g/kg of ECM).

Production performance, nutrient use efficiency, and predicted enteric methane emissions in dairy cows under confinement or grazing management system

“…Neither CH 4 yield (g/kg of DMI) nor CH 4 intensity (g/kg of ECM) changed ( P ≥ 0.23) in response management system ( Table 4 ). We detected a more pronounced reduction in CH 4 production (i.e., –19%) in grazing (mean = 368 g/d) versus confinement (mean = 453 g/d; data not shown) when using data from selected studies ( n = 4; O’Neill et al, 2011 ; Civiero et al, 2021 ; Brito et al, unpublished) whereby enteric CH 4 production was directly measured. Furthermore, CH 4 yield (–7.2%) and CH 4 intensity (–6.2%) were both lower in cows under grazing than confinement management in these 4 studies (data not shown).…”

“…Milk yield was 9.3% lower ( P < 0.01; Table 3 ) in grazing versus confined dairy cows likely in response to a 9.5% drop in DMI leading to decreased energy intake. In 3 studies used in the data set (i.e., Fajardo et al, 2015 ; Soutto et al, 2020 ; Civiero et al, 2021 ), grazing cows received less concentrate than those in confinement, while in 2 other experiments (i.e., Kolver and Mullen, 1998 ; O’Neill et al, 2011 ), herbage was not supplemented with concentrate (100% grazing; Table 1 ). Therefore, decreased or no concentrate supplementation also contributed to the milk yield reduction in grazing dairy cows ( Table 3 ).…”

“…Effect of management system on ECM yield, feed efficiency, milk N efficiency, and predicted enteric CH 4 production evaluated through WMD between confinement and grazing is presented in Table 4 . Response variables shown in Table 4 were all calculated or predicted to standardize comparisons between management systems and to obtain additional data such as enteric CH 4 production, which was reported in only 4 out of 10 studies [ O’Neill et al, 2011 ; Civiero et al, 2021 ; Brito et al, unpublished (2 experiments)]. Therefore, the intercontinental equation [CH 4 (g/d) = 33.2 (13.54) + 13.6 (0.33) × DMI + 2.43 (0.245) × neutral detergent fiber] published by Niu et al (2018) was used to predict CH 4 production.…”

“…Only 4 studies (2 published and 2 unpublished) included in our data set reported enteric CH 4 production ( O’Neill et al, 2011 ; Civiero et al, 2021 ; Brito et al, unpublished). Therefore, we used the intercontinental equation proposed by Niu et al (2018) , which is based on DMI and dietary neutral detergent fiber concentration to predict enteric CH 4 production for all selected studies including those that measured CH 4 production.…”

Strategies of maize silage supplementation of grazing dairy cows: Effects on milk production, pasture intake, grazing behaviour and methane emissions

“… The data may be useful for researchers and nutritionists who study dairy cow nutrition at grazing in order to simulate and/or predict intake regulation of individual cows. Few published studies have investigated different strategies of maize silage supplementation of grazing dairy cows that combine supplementation level and herbage allowance or combine the timing of supplement distribution and the daily access time to pasture [ 1 , 2 , 3 ]. This study provides individual daily data on methane emissions estimated using the Laser Methane Detector [ 4 , 5 ].…”