Brewer's Grain as a Sustainable Feed Supplement: Reducing Methane Emissions in Goats and Cattle

Co-author: Ishaya Gadzama

Introduction

As the demand for livestock products rises, addressing the environmental impact of livestock production, particularly greenhouse gas emissions, becomes increasingly important (Hristov et al., 2013; Knapp et al., 2014). Methane (CH₄) emissions from ruminants, including cattle and goats, represent a significant environmental concern and a loss of valuable feed energy (Murray et al., 1976). In Zimbabwe, where smallholder farmers predominantly raise indigenous goat breeds like the Matebele, exploring sustainable feeding practices is crucial (Makombe, 2020). One such practice is the supplementation of diets with agro-industrial byproducts like brewer's grain, which holds the potential for mitigating CH₄ emissions. Brewer's grain constitutes about 85% of the total solid by-products generated in the brewing industry (Zeko-Pivač et al., 2022). During the brewing process, the soluble components of the grain are extracted, leaving behind the brewer's grain rich in insoluble materials. Brewer's grain typically contains 15–26% protein and 35–60% digestible fiber on a dry basis (Ikram et al., 2017). 

Brewer's spent grain (BSG) is an excellent source of high-quality bypass protein, making it particularly valuable in animal feed as it provides essential nutrients that are not easily broken down in the rumen, thus enhancing protein intake for livestock, particularly ruminants (Guermah et al., 2016). Research suggests that incorporating brewer's grain into goat diets can lead to a reduction in CH₄ emissions (Makombe, 2020). This reduction is likely due to altered rumen fermentation dynamics brought about by the unique composition of brewer's grain (Bhatta et al., 2008). This altered fermentation process can decrease the production of hydrogen, a key substrate for methanogenesis (Mackie et al., 2023). Additionally, diets containing brewer's grain can lead to lower proportions of readily fermentable carbohydrates, limiting microbial growth and protein synthesis, further contributing to reduced methane production (Mackie et al., 2023). 

Makombe (2020) investigated the effect of supplementing Matebele goat diets with brewer's grain and observed a significant reduction in CH₄ emissions compared to a control diet. These findings highlight the potential of brewer's grain as a viable strategy for mitigating methane emissions from Matebele goats, a crucial step towards sustainable livestock production in Zimbabwe. Brewer's grain has been the subject of several studies driven by the need to address environmental concerns and improve livestock production efficiency. Investigating the potential of brewer's grain is driven by the need to address environmental concerns and improve livestock production efficiency. 

Effects of Feeding Brewer's Grains to Goats

Sina et al. (2017) evaluated the effects of supplementing basal diets of fresh sweet cassava foliage or fresh water spinach with a low level (5-6% of diet DM) of ensiled brewer's grains on the performance and health of growing goats. The study found that brewer's grains improved growth performance and health indicators (reduced urine thiocyanate excretion) when included in the cassava foliage diet. No thiocyanate was detected in the urine of goats fed water spinach, regardless of brewer's grains supplementation. Feeding goats a mix of sweet and bitter cassava foliage, supplemented with biochar and brewer's grains, improves nitrogen retention and reduces methane emissions compared to feeding sweet cassava foliage alone (Phuong et al., 2019). Yanti et al. (2021) reported that supplementation of male Kacang goats with 9.7%, 14.5%, and 19.4% brewer's grain plus king grass and rice bran did not have any significant differences in gross energy intake, digestible energy, energy digestibility, or methane emissions. 

Effects of Feeding Brewer's Grains to Cattle

In cattle, brewer's grain supplementation has been shown to increase milk production, although it may reduce milk lipid content (Mussatto, 2014). Duthie et al. (2015) found that cows fed 226 g/kg brewer's grains (BG) and 763 g/kg barley straw produced significantly less daily CH₄ than those on the grass silage (GS) diet (131 g/day vs. 156 g/day, respectively). However, the two diets had no significant differences in daily dry matter intake (DMI) (9.92 kg/day for BG vs. 9.86 kg/day for GS). BG-fed cows had higher molar proportions of acetate and lower proportions of propionate and butyrate in rumen fluid than GS-fed cows. Moate et al. (2011) found that lactating dairy cows fed a BG diet significantly reduced CH₄ emissions when expressed as g CH₄/cow/day or g CH₄/L milk. However, BG had small positive effects on milk yield and negative impact on milk fat and protein concentrations. Hoffmann et al. (2021) did not find any significant differences in CH₄ production (treatments averaging 180 g/animal/day) when corn-dried distillers' grains were used as a replacement for cottonseed meal in the diet of young Nellore bulls grazing tropical pastures. 

Lasind cattle fed brewer's grains at 1% of live weight and rice straw at 0.9% of live weight (DM basis) for 56 days had improved dry matter intake, growth rate, and better rumen fermentation patterns compared to the control (sweet cassava foliage) (Binh et al., 2017). Keopaseuth et al. (2017) reported a quadratic relationship between the growth rate and the proportion of brewer's grains in the diet, with the maximum growth rate observed when brewer's grains constituted 9-17% of the diet DM. A similar quadratic relationship was found between the level of brewer's grains and DM feed conversion. Research suggests that adding spent craft brewer's yeast to rumen microbes can also reduce methane and ammonia production, with the reduction correlated with the amount of hop acids in the yeast (Bryant et al., 2021). 

Conclusion

Incorporating brewer's grain into the diets of ruminants, including goats and cattle, can significantly reduce methane emissions and improve animal performance. This strategy offers a sustainable approach to livestock production, addressing both environmental and nutritional challenges.

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