Effect of treating alfalfa silage with pistachio by‐products extract on S aanen dairy goats performance and microbial nitrogen synthesis

Summary A lactation experiment was conducted to determine the influence of addition of pistachio by‐products extract ( PBE ) to alfalfa silage ( AS ) on performance, rumen fermentation, milk yield and composition, and microbial nitrogen synthesis. Eight multiparous dairy goats (1.8 ± 0.25 kg of milk yield) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments to compare two types of AS (supplemented with or without PBE ) with two levels of dietary crude protein (14% vs. 16% CP ). Dietary treatments were (i) AS with 14% CP of DM diet without PBE (14% CP − PBE ), (ii) AS with 14% CP of DM diet with PBE (14% CP  +  PBE ), (iii) AS with 16% CP of DM diet without PBE (16% CP − PBE ) and (iv) AS with 16% CP of DM diet with PBE (16% CP  +  PBE ). PBE was sprayed on fresh alfalfa at a ratio of 500 ml/kg alfalfa DM to get the final concentration of 1% tannin as tannic acid equivalent on DM basis. Intake of CP was greater (p < 0.01) in goats fed 16% CP diets than those fed 14% CP diets, regardless of PBE supplementation. Supplementation of PBE tended to decrease (p = 0.09) rumen NH 3 ‐N concentration regardless of the level of CP in the diet. Supplementation of PBE tended (p = 0.09) to decrease total purine derivatives regardless of the level of CP in the diet with no significant change in microbial nitrogen supply. Efficiency of microbial nitrogen synthesis ( EMNS ) had a tendency (p = 0.07) to decrease in PBE supplemented diets. There was also a tendency (p = 0.10) for more EMNS in 14% CP fed goats than those fed 16% CP diets. Therefore, AS supplemented with PBE may lead to less concentration of ruminal NH 3 ‐N because of decreased degradation of CP by rumen micro‐organisms in response to pistachio by‐products tannins.