Methane production by two non-ruminant foregut-fermenting herbivores: The collared peccary ( Pecari tajacu ) and the pygmy hippopotamus ( Hexaprotodon liberiensis )

Clauss

et al. 2018

Ecology and Evolution

Self Cite

Stable carbon isotope analyses of vertebrate hard tissues such as bones, teeth, and tusks provide information about animal diets in ecological, archeological, and paleontological contexts. There is debate about how carbon isotope compositions of collagen and apatite carbonate differ in terms of their relationship to diet, and to each other. We evaluated relationships between δ13Ccollagen and δ13Ccarbonate among free‐ranging southern African mammals to test predictions about the influences of dietary and physiological differences between species. Whereas the slopes of δ13Ccollagen–δ13Ccarbonate relationships among carnivores are ≤1, herbivore δ13Ccollagen increases with increasing dietary δ13C at a slower rate than does δ13Ccarbonate, resulting in regression slopes >1. This outcome is consistent with predictions that herbivore δ13Ccollagen is biased against low protein diet components (13C‐enriched C4 grasses in these environments), and δ13Ccarbonate is 13C‐enriched due to release of 13C‐depleted methane as a by‐product of microbial fermentation in the digestive tract. As methane emission is constrained by plant secondary metabolites in browse, the latter effect becomes more pronounced with higher levels of C4 grass in the diet. Increases in δ13Ccarbonate are also larger in ruminants than nonruminants. Accordingly, we show that Δ13Ccollagen‐carbonate spacing is not constant within herbivores, but increases by up to 5 ‰ across species with different diets and physiologies. Such large variation, often assumed to be negligible within trophic levels, clearly cannot be ignored in carbon isotope‐based diet reconstructions.

Section: Discussionsupporting

confidence: 85%

supporting

confidence: 87%

Within trophic level shifts in collagen–carbonate stable carbon isotope spacing are propagated by diet and digestive physiology in large mammal herbivores

Clauss

et al. 2018

Ecology and Evolution

Self Cite

“…Based on the chemical composition in our earlier work, the natural pastures from both sites had similar total digestible nutrients and energy content (Mapfumo et al 2017). Therefore, the enteric CH 4 output by the cows could have been influenced by the amount of feed consumed, digesta retention time and out flow rates and ultimately determined by inter-and intra-animal variation (Hammond et al 2014;Vendl et al 2016). Such a range and fluctuations in CH 4 production by the cows from both breeds could have come from the mode of foraging habits and availability of feed to the animals.…”

Section: Discussionmentioning

confidence: 99%

Enteric methane output from selected herds of beef cattle raised under extensive arid rangelands

et al. 2018

Extensively raised beef cattle contribute to the highest levels of enteric methane (CH 4 ) gas emissions among all livestock. Expensive techniques and logistics hinder monitoring of such gas. Therefore, the objective of this study was to use an inexpensive laser methane detector (LMD) apparatus to determine the enteric CH 4 levels from a herd of beef cows raised on semi-arid rangelands. A total of 24 cows were selected from Boran and Nguni cows (n = 12 per breed) from two different farms. The parities of the cows were as follows: parity 1 (n = 6), parity 2 (n = 6), parity 3 (n = 6) and parity 4 (n = 6). An observer used a hand-held LMD to measure enteric CH 4 emissions plumes during the late afternoon hours when the animals were resting (either standing or lying down). Point measurements (expressed in ppm/m) were taken for six consecutive days and repeated once after every three months. The ratio of CH 4 output per kilogramme DMI was not different in within-breed and between-breed in both seasons. Generally, the dry season recorded the highest CH 4 output per kilogramme of live weight of cow. For example, Boran cows in parity 2 produced the highest output of 1.0 ± 0.04 g CH 4 per kilogramme live weight of cow while Nguni cows in parities 1, 2 and 4 each produced 0.9 ± 0.04 g CH 4 per kilogramme live weight of cow in the dry season. All the animals maintained optimal body condition scores in both seasons (ranging between the lowest of 3.2 ± 0.01 and the highest of 3.4 ± 0.01). Based on the results of the study, it is concluded that cows from both herds produced higher CH 4 per kilogramme live weight of cow in the dry season while maintaining optimal body condition scores in both seasons.

“…Abandoning clear categories of CH 4 -producing digestion types raises the question whether other rules can be gleaned from the comparative dataset. There are well-established relationships between food intake or digesta retention and CH 4 yield in domestic ruminants (Okine et al, 1989;Lassey et al, 1997;Barnett et al, 2012;Hammond et al, 2014;Barnett et al, 2015) and in individual groups of nondomestic species (Frei et al, 2015;Vendl et al, 2015;Vendl et al, 2016a). In addition, the intra-individual variation in CH 4 emission in domestic ruminants is explained by differences in digesta retention, possibly linked to digestive tract capacity (Pinares-Patiño et al, 2003;Goopy et al, 2014;Cabezas-Garcia et al, 2017).…”

Section: Relationships With Intake and Digesta Retentionmentioning

confidence: 99%

Review: Comparative methane production in mammalian herbivores

Clauss

Dittmann

Vendl

et al. 2020

Animal

Methane (CH4) production is a ubiquitous, apparently unavoidable side effect of fermentative fibre digestion by symbiotic microbiota in mammalian herbivores. Here, a data compilation is presented of in vivo CH4 measurements in individuals of 37 mammalian herbivore species fed forage-only diets, from the literature and from hitherto unpublished measurements. In contrast to previous claims, absolute CH4 emissions scaled linearly to DM intake, and CH4 yields (per DM or gross energy intake) did not vary significantly with body mass. CH4 physiology hence cannot be construed to represent an intrinsic ruminant or herbivore body size limitation. The dataset does not support traditional dichotomies of CH4 emission intensity between ruminants and nonruminants, or between foregut and hindgut fermenters. Several rodent hindgut fermenters and nonruminant foregut fermenters emit CH4 of a magnitude as high as ruminants of similar size, intake level, digesta retention or gut capacity. By contrast, equids, macropods (kangaroos) and rabbits produce few CH4 and have low CH4 : CO2 ratios for their size, intake level, digesta retention or gut capacity, ruling out these factors as explanation for interspecific variation. These findings lead to the conclusion that still unidentified host-specific factors other than digesta retention characteristics, or the presence of rumination or a foregut, influence CH4 production. Measurements of CH4 yield per digested fibre indicate that the amount of CH4 produced during fibre digestion varies not only across but also within species, possibly pointing towards variation in microbiota functionality. Recent findings on the genetic control of microbiome composition, including methanogens, raise the question about the benefits methanogens provide for many (but apparently not to the same extent for all) species, which possibly prevented the evolution of the hosting of low-methanogenic microbiota across mammals.