Study on ruminal fermentation of the sheep in three nitrogen diets supplied niacin in vitro

[Objective] The research was done to study rumen fermentation in three different nitrogen source diets added niacin in vitro to provide a theoretical basis for the practice.[Method] The rumen fluid derived from 9 sheep installed permanent rumen fistula in the experiment were randomly divided into 3 groups,3 sheep/group,and were fed soybean meal,linseed meal and urea-linseed meal type basic diet,respectively.Then the concentration of NH3-N,bacterial N concentration,protozoa,total volatile fatty acids(VFA) and acetic acid,propionic acid and acetic acid/propionic acid value were studied in the culture medium of the three nitrogen sources after culturing 0,0.5,1,2,4,8,12,16,20,22 h in vitro when these diets were added niacin.[Result] After adding nicotinic acid,concentration of NH3-N,bacteria N concentration and protozoan numbers in the culture medium of urea-linseed meal diet were higher than those in soybean meal diet,while the soybean meal diet was higher than linseed meal based diets,significant difference changed with culture time.The NH3-N concentration increased to a maximum at 2 h after the culture then decreased,stabiled after 4 h in the medium urea-linseed meal diet;The bacterial N concentration increased 0-12 h after culturing,12-22 h decreased,but no significant difference existed(P0.05).The NH3-N concentration increased 2 h after culturing,decreased to a minimum at 4 h after culturing,then slowly increased;The bacterial N concentration increased in 0-8 h,decreased in 8-22 h in the medium of soybean meal diet.The concentration of NH3-N,bacterial N concentration were not significantly different in the whole culturing process of linseed meal based diet(P0.05).The protozoa numbers in the three kinds of diets reached the maximum in 4 h,respectively,then decreased.The total volatile fatty acids(VFA),acetic acid,propionic acid and acetate/propionate didn't show significant difference in different cultures(P0.05).[Conclusion] After adding nicotinic acid,the utilization of NH3-N was the highest in the medium of urea-linseed meal diet,produced more bacteria and protozoa,hence the urea-linseed meal diet was better than the soybean meal diet,and linseed meal based diet was the worst.