Investigation between Different Amount of Crude Fiber and Fermentation in the Rumen by Beef Suckler Cows

Body condition of suckler cows at the time of calving has an important effect on calving ease and mortality of calves. In the last eight weeks before calving the body condition should be reduced or at least not increased. Rations with a higher amount of crude fibre can be used (rations with straw or late mowed grass silage (GS)) to control the body condition score. Eight suckler cows (Charolais) were feeding a total mixed ration (TMR) in the last eight weeks before calving and GS after calving. By the addition of straw (30% in TMR1 vs 60% in TMR2 of dry matter) was varied the amount of crude fibre in the TMR (GS, straw, mineral) before calving. In the period after calving were GS feeding. Last measurement took place on the pasture (PS). Rumen fluid, plasma, body weight and back fat thickness were collected. Rumen fluid pH was assessed immediately after collection using an electronic pH meter. Volatile fatty acids (VFA), sedimentation, methylene-blue and amount of infusorians were measured. From four key figures an “index of rumen fermentation” (IRF) in the rumen was formed. Statistical analysis took place with analysis of variance (ANOVA) with fixed effects of treatment (TMR1, TMR2, GS and PS) and number of lactations (3-7 lactations) using SPSS Version 25.0 for Windows. Rumen fluid pH had significant differences between variants (TMR1 by 6.6, TMR2 by 6.9, GS by 6.6 and PS by 6.9), but was not affected by other effects. The IRF showed a disturbed fermentation in the rumen by feeding the TMR 1 + 2 with high amount of crude fibre (score: > 10.0 points) and a very good situation for fermentation during grazing the PS (score: 6.9 points). The long-term use of crude fibre-rich rations in the period before calving may cause deviations from undisturbed fermentation in the rumen and adversely affect the utilization of the feed in the rumen.