ARTICLE FEED & ADDITIVE MAGAZINE July 2025 93 Long Rye Grass Hay Long Rye Grass Hay (chopped to 50 mm) Rye Grass Hay Retain on top screen of PSPS (>19mm) Rye Grass Hay Retain on second screen of PSPS (>8mm) Rye Grass Hay Retain on third screen of PSPS (>1.18mm) Grass Silage Corn Silage TMR % of DM 57.1 58.6 57.9 59.1 54.2 53.1 48.1 37.7 mm N/A 42.2 43.5 25.1 9.7 13.8 12.0 13.1 mm 10.3 9.9 10.7 10.8 8.1 11.6 11.2 12.5 1.5 2.1 1.3 1.0 1.0 0.2 0.3 0.3 2.6 3.6 2.2 1.8 1.9 0.5 0.7 0.7 Feed Feed Mean particle length Bolus (Cud) Chews Kg of DM Kg of NDF NDF Table 1. Particle size reduction from feed to bolus Note: PSPS = Penn State Particle Separator - Schadt et al., 2012; Journal of Dairy Science largely through an increase in eating time. This resulted in a decrease in resting time that reflected the increase in total rumination time (Figure 1). Why is this important? Analysis from Rick Grant (Miner Institute, 2007) identified a relationship between resting time and milk production - each hour increase in resting time resulted in a gain of 1.7 kilograms of milk production. Poor quality forages (higher uNDF240) may increase eating time due to the inherent difficulty in reducing particle size while high quality forages (lower uNDF240), due to the potential fragility of the plant, may break down more quickly – thus reducing eating time. A study conducted at the Miner Institute examined the digestibility of the diet (uNDF240) and the physically effective fiber in the diet (peNDF and peuNDF240). The study examined four diets that contained the same amount of corn silage and chopped wheat straw. The particle size and uNDF240 Image 1. Picture of bolus (cud) chemically treated, dyed and separated into individual particles to determine mean particle size. Photo: Courtesy of Iris Schadt, PHD Researcher at CoRFiLaC, Ragusa, Sicily, Italy
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