Abstract
Previous studies have focused on the rumen microbiome and enteric methane (CH4) emissions in dairy cows, yet little is known about steers, especially steers of dairy breeds. In the present study, we comparatively examined the rumen microbiota, fermentation characteristics, and CH4 emissions from six non-cannulated Holstein (710.33 ± 43.02 kg) and six Jersey (559.67 ± 32.72 kg) steers. The steers were fed the same total mixed ration (TMR) for 30 days. After 25 days of adaptation to the diet, CH4 emissions were measured using GreenFeed for three consecutive days, and rumen fluid samples were collected on last day using stomach tubing before feeding (0 h) and 6 h after feeding. CH4 production (g/d/animal), CH4 yield (g/kg DMI), and CH4 intensity (g/kg BW0.75) were higher in the Jersey steers than in the Holstein steers. The lowest pH value was recorded at 6 h after feeding. The Jersey steers had lower rumen pH and a higher concentration of ammonia-nitrogen (NH3-N). The Jersey steers had a numerically higher molar proportion of acetate than the Holstein steers, but the opposite was true for that of propionate. Metataxonomic analysis of the rumen microbiota showed that the two breeds had similar species richness, Shannon, and inverse Simpson diversity indexes. Principal coordinates analysis showed that the overall rumen microbiota was different between the two breeds. Both breeds were dominated by Prevotella ruminicola, and its highest relative abundance was observed 6 h after feeding. The genera Ethanoligenens, Succinivibrio, and the species Ethanoligenens harbinense, Succinivibrio dextrinosolvens, Prevotella micans, Prevotella copri, Prevotella oris, Prevotella baroniae, and Treponema succinifaciens were more abundant in Holstein steers while the genera Capnocytophaga, Lachnoclostridium, Barnesiella, Oscillibacter, Galbibacter, and the species Capnocytophaga cynodegmi, Galbibacter mesophilus, Barnesiella intestinihominis, Prevotella shahii, and Oscillibacter ruminantium in the Jersey steers. The Jersey steers were dominated by Methanobrevibacter millerae while the Holstein steers by Methanobrevibacter olleyae. The overall results suggest that sampling hour has little influence on the rumen microbiota; however, breeds of steers can affect the assemblage of the rumen microbiota and different mitigation strategies may be needed to effectively manipulate the rumen microbiota and mitigate enteric CH4 emissions from these steers.
Highlights
Holstein and Jersey are two major dairy breeds for milk production
The findings of the present study showed that the Holstein steers had a greater DMI and average daily gain (ADG) than Jersey steers when fed the same total mixed ration (TMR) diet
This is consistent with the heavier body weight (BW) and BW0.75 of the Holstein steers than the Jersey steers and the report by Flay et al (2019)
Summary
Holstein and Jersey are two major dairy breeds for milk production. Steers of these breeds contribute to beef production. To meet the ever-increasing demand for milk and beef by the growing global population and rising living standards, improvement of animal performance is required. O’Hara et al (2020) reviewed the association of the rumen microbiota and fermentation products and the effects of such association on valuable traits such as feed efficiency and CH4 emissions. In the rumen of most ruminant species, Firmicutes, Bacteroidetes, and Proteobacteria are the dominant bacterial phyla, and Prevotella, Fibrobacter, and Butyrivibrio are the dominant bacterial genera, which can ferment a wide range of dietary polysaccharides and protein (O’Hara et al, 2020)
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