Abstract
Simple SummaryIn dry, mountainous areas, ewes are fed low-quality forages (hay or straw) indoors, although they also graze in high-quality pastures when available. Concentrate supplementation is recommended to cover high nutritional requirements during lactation. Condensed tannins (CT) of quebracho (Schinopsis balansae) can be included in the concentrate to reduce methane (CH4) emissions and ruminal degradation of protein, improving the fermentation’s efficiency. Furthermore, low levels of quebracho can improve some meat and milk quality traits. The effects of the inclusion of concentrate and CT in diets depend on the level of inclusion and the quality of forage. The aim of this study was to evaluate the in vitro fermentation characteristics of diets in order to identify the most suitable one to be fed to ewes under farming conditions. The diets examined differed in quality of the forage available, comparing hay versus fresh forage diets and forage alone versus 70:30 forage:concentrate with (quebracho) or without CT (control) in each type of forage. The fresh-forage-based diets had lower gas and CH4 production and greater in vitro organic matter degradability (IVOMD) than the hay-based diets. The inclusion of quebracho concentrate increased the IVOMD in hay-based diets and reduced ammonia content in fresh-forage-based diets.Ewes receive hay or graze on fresh pastures supplemented with concentrates to fulfil their lactation requirements. Quebracho (Schinopsis balansae) can be added to change the ruminal fermentation. Fermentation parameters of forages alone and 70:30 forage:concentrate diets with control and quebracho concentrate were compared after 24 h of in vitro incubation. Fresh forage diets produced less gas (p < 0.05) and had greater IVOMD (p < 0.001), ammonia (NH3-N) content, valeric acid, branched-chain volatile fatty acid proportions, and lower propionic acid proportion than the hay diets (p < 0.01). In the hay diets, methane production increased with control concentrate (p < 0.01) and tended to decrease with quebacho concentrate (p < 0.10). The inclusion of both concentrates increased the acetic:propionic ratio (p < 0.01), and only the inclusion of quebracho concentrate increased the IVOMD (p < 0.01). In the fresh forage diets, gas and methane production increased with the inclusion of the control concentrate (p < 0.05), but methane production decreased with quebracho concentrate (p < 0.01). The inclusion of quebracho concentrate reduced the NH3-N content and valeric acid proportion (p < 0.05). In conclusion, the inclusion of quebracho concentrate would be advisable to reduce the CH4 production and NH3-N content in fresh forage diets and to increase the IVOMD in hay diets in comparison with the forages alone.
Highlights
In dry, mountainous areas, ewes are usually stalled around parturition and fed cheap, low-quality forages supplemented with concentrates/grain throughout lactation to fulfil their maintenance and lactation requirements for energy
The forages fed to ewes in these systems differ greatly in their chemical composition, especially the contents of structural carbohydrates and protein, which increase or reduce the parameters of ruminal fermentation depending on chemical composition [6]
The fermentation parameters between both forage-based diets and the effect of the inclusion of control or quebracho concentrate within each forage with respect to the forage alone were compared
Summary
Mountainous areas, ewes are usually stalled around parturition and fed cheap, low-quality forages (hay or straw) supplemented with concentrates/grain throughout lactation to fulfil their maintenance and lactation requirements for energy. Ewes can raise their suckling lambs at pastures during spring [1,2]. The inclusion of quebracho in the concentrate of grazing and hay-fed Churra Tensina ewes decreased milk protein content [4], reduced lipid oxidation, and increased α-tocopherol content in the meat of the suckling lambs [5]. The forages fed to ewes in these systems differ greatly in their chemical composition, especially the contents of structural carbohydrates and protein, which increase or reduce the parameters of ruminal fermentation depending on chemical composition [6]. The fermentation of low-quality forages leads to high gas and methane (CH4 ) production [7], to the detriment of microbial biomass synthesis [8]
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