The Effects Of Different Quality Forage (GI) And Concentrate To Roughage Rations On Performance, Nutrient Digestion And Metabolism In Dairy Cows

In order to improve GI technical standard system, and establish concentrate supply model of dairy diet based on forage GI value and milk yield, The objective of this paper was to determine the effects of different quality roughage (GI) and concentrate to roughage rations on production, apparent digestibility, blood parameter and chewing behavior in lactating dairy cows.Thirty six healthy Chinese Holstein cows with similar milk yield, lactation period and parity in middle lactation were selected, the cows were allocated into three dietary treatments, each big group had3small groups, and each small group includes4cows. In the first big group, silage corn straw was used, and concentrate to roughage ratio were55:45,57.5:42.5and60:40respectively, and denoted by A1, A2and A3; In the second big group, silage corn straw and L. chinensis were used, and concentrate to roughage ratio were55:45,57.5:42.5and60:40respectively, and denoted by B1, B2and B3; In the third big group, silage corn and L. chinensis were used, and concentrate to roughage ratio were55:45,57.5:42.5and60:40respectively, and denoted by C1, C2and C3. The experiment will last30days consisting of10days of adaption period and20days of the treatment period, the feeding and management were conformed to the dairy pasture.The results showed that:(1) milk yield increased significantly with the increasing of concentrate to roughage ratio (P<0.05), while milk proteins and lactose showed an increasing trend and milk fat showed an decreasing trend (P>0.05). With the improvement of roughage quality (GI), milk yield increased significantly (P<0.05) and milk fat increased insignificantly (P>0.05), while milk proteins and lactose decreased insignificantly (P>0.05).(2) Rumen pH could be revealed by the blood endotoxin concentration, urea nitrogen can be used a response of body protein metabolism, and P-hydroxybutyric acid and free fatty acid can reflect the balance of energy supply. In this experiment, the blood concentration of β-hydroxybutyric acid, endotoxin, urea nitrogen and free fatty acid increased significantly with the increasing of concentrate to roughage ratio (P<0.05). There is a quadratic curvilinear correlation between the improvement of roughage quality (GI) and above four blood index, the concentration which received the yellow corn silage＋chinensis were highest, and the other treatments were lower insignificantly (P>0.05).(3) For the apparent digestibility of NDF、ADF、CP-、Ca、P, there were no significant difference among all treatments with the increasing of concentrate to roughage ratio and with the improvement of roughage quality (GI)(P>0.05).(4) There were no significant difference for feed intake and rumination time in all treatments (P>0.05), but masticatory time decreased significantly with the increasing of concentrate to roughage ratio and with the improvement of roughage quality (GI)(P<0.05).Considering the above indexes, milk yield and milk quality reached higher level and physiological status was in better condition when silage＋chinensis was used and the concentrate to roughage ratio was57.5:42.5.