ABSTRACT
Reversing climate change requires broad, cohesive, and strategic plans for the mitigation of greenhouse gas emissions from animal farming. The implementation and evaluation of such plans demand accurate and accessible methods for monitoring on-field CH4 concentration in eructating breath. Therefore, this paper describes a longitudinal study over six months, aiming to test a protocol using a laser methane detector (LMD) to monitor CH4 emissions in semi-extensive dairy farm systems. Over 10 time points, CH4 measurements were performed in dry (late gestation) and lactating cows at an Azorean dairy farm. Methane traits including CH4 concentration related to eructation (E_CH4) and respiration (R_CH4), and eructation events, were automatically computed from CH4 measured values using algorithms created for peak detection and analysis. Daily CH4 emission was estimated from each profile's mean CH4 concentration (MEAN_CH4). Data were analyzed using a linear mixed model, including breed, lactation stage, and parity as fixed effects, and cow (subject) and time point as random effects. The results showed that Holsteins had higher E_CH4 than Jersey cows (p < 0.001). Although a breed-related trend was found in daily CH4 emission (p = 0.060), it was not significant when normalized to daily milk yield (p > 0.05). Methane emissions were lower in dry than in lactation cows (p < 0.05) and increased with the advancement of the lactation, even when normalizing it to daily milk yield (p < 0.05). Primiparous cows had lower daily CH4 emissions related to R_ CH4 compared to multiparous (p < 0.001). This allowed the identification of periods of higher CH4 emissions within the milk production cycle of dairy cows, and thus, the opportunity to tailor mitigation strategies accordingly.
ABSTRACT
Using invasive plants in animal production can provide an economical and eco-sustainable competitive advantage in a globalized market. The Opuntia ficus-indica and the Agave americana L. are invasive plants historically used by Azorean farmers as an alternative ruminant water source in the summer. This study aims to better understand their properties and how they vary throughout the year, so their use to complement animal diets can be optimised. Six samples of each species were collected on the Terceira Island during 2 growth seasons: winter (January 2021) and summer (September 2021), and their chemical composition, in vitro digestibility, and gas production, were determined. Significant (p < 0.05) differences were found in all parameters between the summer and the winter, with larger variations in both fibre (NDF and ADF) and digestibility parameters found between the Opuntia and the Agave. Gas production was greater in the summer for Opuntia and in the winter for Agave. Even though the digestibility was lower in the summer, we found that both plants offer a viable ruminant feed complement in both seasons, providing a cheap and eco-sustainable alternative water source, that can be associated to dry forage and compound feeding stuff with a high crude protein content when designing ruminant diets.
