Effects of different levels of corn silage and alfalfa hay on rumen pH, VFA and milk production in dairy cows
The present study investigated the effects of different levels of corn silage and alfalfa hay on rumen pH, VFA and milk production of Holstein cows. In this study 15 Holstein cows (39±9 kg milk yield/day; 37±10 days in milk) were used in a completely randomized design experiment. Animals were kept in individual tie-stalls for 9 weeks. Treatments included three levels of hay and corn silage: 1) 10% alfalfa hay -30% silage corn (CS), 2) 20% alfalfa hay -20% silage corn (AH- CS) and 3) 30% alfalfa hay -10% silage corn (AH); And the ratio of forage: concentrate was 60:40. Cows were fed the total mixed rations (TMR) twice daily. Individual DMI was measured daily. On 4 and 9 week of experiment, rumen fluid from the ventral sac was sampled using the rumenocentesis technique. Rumen fluid samples were taken 4 h after morning feed. Ruminal pH measured immediately after sampling using a pH meter. The rumen fluid was stabilized with sulfuric acid (1cc per 50 ml) and frozen at −20°C until VFA analysis by gas chromatography. Normality of distribution and homogeneity of variance for residuals were tested using PROC UNIVARIATE and adjust Tukey-Kramer (SAS Institute, 2003). Dry matter intake was higher (p<0.05) when cows were fed diets AH-CS (23.20 kg per day) and diet CS (22.95 kg per day) than diet AH (18.64 kg per day).Diet affected milk production with CS and AH-CS being higher (P < 0.01) than AH (34.88, 35.21 and 30.78 kg/day for diets CS, AH-CS and AH, respectively. Data from ruminal pH clearly showed replacing AH with CS had a quadratic effect on the rumen acidity (P<0.05). In contrast to ruminal pH, ruminal VFA concentration was not meaningfully affected by the treatments (P>0.05). It is concluded that feeding alfalfa hay more than corn silage reduced dry matter intake, therefore reduced milk production.
Dry matter intake