Rumen Degradation of Endosperm and Mesocarp Expellers from Acrocomia aculeata (Jacq.) Lodd. ex Mart. in Sheep Grazing Either Natural Pastures or Brachiaria brizantha cv. Marandu

Twenty-four ewes (eight fistulated in the rumen) were assigned to a 2 × 2 factorial design. The treatments included the pasture grazed (natural mixed swards—NMS or cultivated monophytic (Brachiaria brizantha cv. Marandu) swards—CMS) and the level of supplementation: without supplement or with a 1% supplement (dry matter (DM)/live weight). The supplement included one-third endosperm expeller (ENE) and two-thirds mesocarp expeller (ME) from Acrocomia aculeata (Jacq.) Lodd. ex Mart. In sacco rumen degradation of ENE, ME, NMS, and CMS was assessed in fistulated sheep, as were rumen fermentation variables. Average daily gain (ADG) was assessed in non-fistulated animals during a 7-week period. Potential degradability of the DM and crude protein of the expellers was not affected by the type of pasture grazed or the level of supplementation (p > 0.05), but the fractional rate of degradation (c) of DM was three times faster (p < 0.01) for ME than for ENE. The potential degradability of neutral detergent fiber was 34% higher (p < 0.0001) for ENE, with no differences in c (p > 0.1). Supplementation slowed down the c of the DM of the pastures, especially in animals grazing NMS (24% lower). Treatments affected rumen pH, concentration of volatile fatty acids, and proportion of valerate, in different ways. The use of the supplement increased ADG of sheep (six-fold in sheep grazing NMS and 40% in those grazing CMS). The use of a mixture of one-third ENE plus two-thirds ME as a protein supplement in sheep grazing either multi-species natural pastures or monophytic swards of Brachiaria brizantha cv. Marandu slows down the fractional rate of degradation of the pastures, the effect of which is more intense in animals grazing natural swards. This supplementation also increases average daily gain, more substantially with multi-species natural pastures.