Shredding of grass-clover before ensiling: Effects on feed intake, digestibility, and methane production in dairy cows

Abstract

Shredding is a type of processing that mechanically treats forage in order to separate plant tissues apart and rupture the plant cell. This experiment aimed at investigating the effects of shredding grass-clover harvested at two developmental stages on feed intake, digestibility, and gas production. The grass-clover was harvested either at an early (May 14; ERL) or a late (May 29; LAT) developmental stage. Within each developmental stage, grass-clover was mown, wilted, and either baled and wrapped (CON) or shredded, baled, and wrapped (SHR). The four combinations of ensiled grass-clover (ERL-CON, ERL-SHR, LAT-CON, and LAT-SHR) was fed to four rumen, duodenum, and ileum cannulated primiparous Danish Holstein cows in a 4 × 4 Latin square design with four periods of 21 d duration. The silage was offered for ad libitum intake. Silage density was higher (P < 0.01) for SHR compared to CON. Silage concentrations of L-lactate and acetate were higher (P = 0.01 and P < 0.01, respectively) and the silage concentration of butyrate was lower (P < 0.01) for SHR compared to CON, whereas pH was lower (P = 0.02), which indicated silage quality improved from shredding. The dry matter (DM) intake (DMI), milk yield, and rumen digestibility of neutral detergent fibre (aNDFom) were not affected by shredding, whereas feeding SHR compared to CON resulted in lower (P = 0.05) total tract digestibility of aNDFom (714 vs. 727 g/kg) and lower (P = 0.04) methane (CH4) production (60 vs. 66 L CH4/kg organic matter (OM) digested in the rumen). Compared to CON, SHR had a higher (P = 0.02) proportion of butyrate in rumen fluid indicating that shredding had some effect on the dynamics of rumen fermentation. However, the effective degradability of CP and aNDFom in the rumen determined in situ showed no effect of shredding. Rumination and total chewing time were lower (P = 0.03 and P = 0.05, respectively) and the concentration of protein in the milk was higher (P = 0.02), when shredding LAT compared to ERL. Furthermore, concentrations of CP and purines in rumen microbes were lower (P = 0.04 and P = 0.01, respectively), when cows were fed LAT compared to ERL. In conclusion, shredding improved silage fermentation quality, reduced digestibility of aNDFom without affecting the digestibility of other nutrients, and reduced methane production per kg of rumen digested OM. Furthermore, we observed no benefits from shredding grass-clover harvested at a late compared to early developmental stage, except for increased concentration of protein in milk and reduced time spent for chewing during rumination and total chewing.