Impact of rumen fluid source as inoculant taken from beef cows of varying productivity and at different times post-partum on in vitro digestion activity

An experiment was conducted to determine variation in digestion activity in vitro using rumen fluid from 10 multiparous Angus cows from a 104 cow-calf pair herd. Cows were selected as having relatively high or low productivity as assessed by their life time weaning weight ratio taken from AIMS records (American Angus Association, Saint Joseph, MO 64506). There was a productivity effect on certain VFAs, like acetate: propionate concentrations both in vivo (P < 0.1) and their 24 hour production rate in vitro (P < 0.1). There was, however, no productivity effect (P > 0.1) on in vitro fiber digestion activity. The interaction effect of productivity and season influenced (P<0.1) more digestibility measures in vitro than any interaction effects. Although there are some inferences that suggest these results are related to the diet fed and the intake of the cows, the cause and effect nature of this relationship requires further investigation.