Effects of chestnut bark (Castanea spp.) tannin extracts on selectivity, dry matter intake, weight gain, and enteric methane emission from llamas (Lama glama) under grazing conditions in the high Andean grasslands
Introduction
Although Peru is one of the countries with low greenhouse gas production (GHG), it is estimated that livestock contributes 14.5 % of GHG (after land-use and energy changes of 53.1 and 23.3 %, respectively). It is worth mentioning that methane (CH4) from enteric fermentation and manure emissions from ruminants are the main contributors of GHGs in the livestock sector in Peru, representing 64 % of total GHG production in that sector (García et al., 2007)
Peru is the second-largest llama (Lama glama) producer worldwide, with 746,269 animals (representing approximately 27 %, of the World population). Approximately 70 % of the llama population in Peru is in Puno, Cusco, Arequipa, and Huancavelica (INEI, 2012).
Due to its rusticity and adaptability to various ecological zones, the llama provides an essential service as a pack animal within the small breeder's agricultural system, fulfilling an important role in Andean culture's economic and social context. Producers generally maintain these animals until an advanced age of 12–14 years. In addition, interest in llama breeding is increasing due to its peculiarities of adaptation to high altitudes and low-temperature conditions (Franco et al., 2017).
The puna grassland plays a key role economically, providing food security and several other goods and services to society. The structure and function of this ecosystem are threatened by land degradation and climate change. Ecological models predict changes in vegetation cover, productivity, and carrying capacity of pastures, a situation that will most likely affect the local economy and food availability. In this scenario, it is urgent to develop conservation policies and sustainable management of grasslands that contribute to mitigating GHG emissions generated by the livestock activity (Flores, 2016).
Methane is a GHG whose global warming potential has been 28 times greater than that of CO2 over a 100-year horizon (IPCC, 2014). In domestic ruminants, cattle and buffalo are the main emitters of CH4 (Monteiro et al., 2018). The CH4 generated in the rumen as a percentage of the energy of the feed consumed generally varies from 7 to 10% (Knapp et al., 2014), but variations from of 2–12% have also been reported (Johnson et al., 1993).
Camelids have unique digestive characteristics, such as longer feed retention, high rate of passage of the liquid phase, greater digestibility of fibrous feeds, and greater saliva production for buffering activity (San Martín and Bryant, 1989), characteristics that allow them to make more efficient use of high-Andean forage resources. However, the nutritional information available in these species is still scarce, and there are few studies dedicated to nutrient utilization and excretion of digestibility byproducts, such as CH4, under these conditions.
The production of CH4 by ruminants has received considerable attention from the scientific community, and it is expected that its reduction in animals should have positive effects on animal productivity (Moscoso et al., 2017b). For this purpose, several researchers are testing strategies for enteric CH4 emission reduction, by dietary manipulation (Muñoz et al., 2015; Moscoso et al., 2017b), ruminal microbiota manipulation, and animal selection (Pinares-Patiño et al., 2013).
Cattle in developing countries are primarily maintained on high-fibre diets with little or no concentrate, resulting in increased ruminal methanogenesis (Goel and Makkar, 2011). Therefore, the use of forage species rich in secondary plant metabolites (SPM) in many parts of the tropics is increasing to improve animal performance and reduce CH4 emission (Goel and Makkar, 2011).
Condensed tannins (CT), also known as proanthocyanidins, are secondary metabolites of plants (Waghorn, 2008) currently being investigated in several laboratories (Goel and Makkar, 2011). The term "tannin" derives from the tanning of skins to create leather; Tannins also contribute to the astringency of many popular drinks such as tea and wine (Waghorn, 2008).
The role of tannins in plant metabolism is largely unknown, although several hypotheses have been proposed; however, their effects on ruminant digestion are becoming more apparent. Condensed tannins bind to proteins in the rumen, reducing protein degradation, and when dietary crude protein (CP) concentrations exceed animal requirements for CP, these effects can improve performance. However, when dietary CP concentrations are low, and fibre concentrations are high, CTs are nearly always detrimental (Waghorn, 2008).
Forage sources containing CTs have shown significant effects in reducing CH4 emissions (Pinares-Patiño et al., 2003; Moscoso et al., 2017b). It has been postulated that CTs reduce ruminal methanogenesis by decreasing hydrogen formation and also by directly inhibiting the activity of methanogenic microorganisms (Patra and Saxena, 2011); levels of reduction were reported to be up to 23 % kg−1 DM consumed (Moscoso et al., 2017b)
Finally, it is worth noting that there are very few works measuring enteric CH4 emission from llamas under high Andean conditions, and the results are contradictory.
Section snippets
Location of the study
The field study was carried out at the South American Camelids CICAS "La Raya" Research Center located at an altitude of 4200 m above sea level in Maranganí district, Canchis, Cusco, Peru. Gas analysis (CH4 and SF6) was carried out in the Laboratory of Climate Change and Animal Production in the Faculty of Agrarian Sciences at the National University of San Antonio Abad of Cusco, and feed analyses were carried out in the Food Nutritional Assessment Laboratory in the Faculty of Zootechnics at
Estimation of diet quality
The composition of the forage selected for both treatments is presented in Table 1. No significant differences were observed between the treatments (P > 0.05). Although the control treatment had a slightly higher crude fibre content, NDF, and ADF than the tannin treatment, overall nutrient levels were similar in both treatments.
Estimation of selectivity of the diets for functional groups, plant parts and physiological state of the plants
The Steinhaus similarity index for diet selectivity of functional groups was considerably high (Table 2), suggesting that the preference for functional groups in both
Determination of diet selectivity
In the present study, the marked preference (P < 0.05) for grasses and graminoids was similar to that found by San Martín (1991) at 93 % and Achu et al. (2003) at 88.77 %, probably because both investigations were performed in humid puna conditions, where there are more plant species. Furthermore, the results were slightly lower than those found by Choquemamani (2017) at 98.4 %, most likely because these studies were conducted in dry puna conditions.
The marked preference (P < 0.05) for leaves
Conclusions
The use of tannins from chestnut bark did not affect the diet composition in llamas grazing on the high Andean grassland, with an average of 91.5 % of grasses and graminoids, 48 % of leaves, 36.5 % of stems, and 61.5 % of the green phenological stage. In addition, the use of tannins from chestnut bark did not affect the DMI of llamas grazing on high Andean grasslands at 1,614.6 and 1,624.7 g in the control and tannin treatment groups, respectively. Finally, tannins from chestnut bark reduced
Declaration of Competing Interest
All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version.
This manuscript is not under review at, another journal or other publishing venue.
The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript
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