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In vitro ruminal fermentation of dairy diets including almond hulls.

Publicat a:ADSA 2023 Annual Meeting (. . 2023) - 2023-06-26 106(1), DOI:

Autors: Recalde, A., Carro, M.D., Jiménez, R., Calero, S., Barrero-Domínguez, B., García-Sánchez, B., and de Evan, T.

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Almond hulls (AH) are frequently used in dairy ruminant feeding, but information on the effects of this by-product on ruminal fermentation is scarce. The aim of this study was to assess the in vitro ruminal fermentation of diets for dairy ruminants including increasing amounts of AH. The AH sample contained (as feed basis) 7.70% ash, 7.37% crude protein (CP), 23.7% total sugars, and 14.3% crude fiber. The experimental treatments were 4 diets having similar CP and fiber content: a control diet without AH, and 3 diets including 8 (AH8), 16 (AH16) and 24% (AH24) of AH (fresh matter basis). All diets contained 40% of alfalfa hay, and the AH partially substituted corn, wheat bran and sugar beet pulp. Diets were fermented in vitro with buffered ruminal fluid from 4 sheep for 120 h to measure gas production kinetics, and for 24 h to measure fermentation parameters (pH, volatile fatty acids [VFA] and NH3-N). Data were analyzed as a mixed model (Proc Mixed of SAS) in which diet was a fixed effect and ruminal inoculum was a random effect. Linear and quadratic effects of including increased amounts of AH were tested by polynomial contrasts. Increasing AH level in the diet decreased (P ≤ 0.01; linear and quadratic) the time at which gas production started (lag time), with no effects on other gas production parameters. This indicates a more rapid start of fermentation of AH diets, possibly due to sugars content in AH. There were no differences between control and AH8 diets in any fermentation parameter at 24 h incubation, but increasing the AH level reduced (P ≤ 0.05; quadratic) total VFA production and NH3-N concentrations and increased final pH (P ≤ 0.01; linear and quadratic), all which suggest a reduction of diet fermentability. The use of AH did not affect VFA profile, excepting that butyrate proportions decreased (P = 0.05; quadratic) as the dietary level of AH augmented. These results indicate that AH could partially substitute conventional ingredients in dairy ruminant diets without negatively affecting their rumen fermentation. High inclusion levels of AH can reduce the ruminal degradability of the diet, but in the practice, this would depend on the nutritive quality of the AH used.

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