Assessment of rumen in vitro incubation (gas production) technique and chemical analyses by detergent system to predict metabolisable energy content in mixed diets of lactating cows

A study was conducted to assess the potential of rumen in vitro incubation for gas production (RIVIGP) and summative equations of detergent system (SEDS) to obtain estimates of energy values in mixed diets. The feeding experiments included digestion trials (DT) to obtain energy values and feeding trials (FT) to assess the potential of energy values obtained by DT, RIVIGP and SEDS to account for the observed performance in lactating cows. Six feeding experiments were conducted using six diets. Each experiment included four cows except the fifth, which included three cows. The FT lasted for 9–11 weeks and the DT for seven days during the FT. The diet was made from either finger millet straw (FMS) or chaffy-paddy hay (CPH) and compounded feed mixture (CFM). The metabolisable energy (ME, MJ kg−1 DM) content of total diet at maintenance level of intake obtained by DT for diets 1–6 were 11.0, 9.2, 10.5, 10.1, 8.8 and 7.6 respectively. The corresponding estimates obtained from RIVIGP and SEDS were 10.2 and 10.2, 9.1 and 9.2, 9.5 and 10.7, 9.4 and 10.5, 8.3 and 7.1, 6.6 and 6.9 respectively. The relationship of ME (DT) (y) with ME (RIVIGP) and ME (SEDS) were y=1.11+.95x (r 0.96, P <0.01) and y=3.5+0.66x (r 0.91, P<0.01) respectively. The mean ME output (Maintenance+4% FCM yield+gain) for the six experiments was 103.5±2.9. The ME intake estimated from ME obtained from DT, RIVIGP and SEDS were 112.7±5.3, 106.4±4.3 and 111.1±6.7 respectively. Thus the observed performance of lactating cows expressed in terms of the total ME output was accountable to the extent of 92, 97 and 93% of ME intake estimates obtained from ME values derived by DT, RIVIGP and SEDS respectively, indicating the potentials of ME values obtained from RIVIGP and SEDS in diet formulation for lactating cows.