Rumen metabolites in crossbred calves fed graded levels of rumen degradable protein and undegraded dietary protein

Abstract

Crossbred calves (4) each fitted with a rumen cannula, were fed on 4 types of concentrates, varying in CP (%) and also the RDP: UDPratio, viz. 23,4 and 79: 21 foy,T1,21.0 and 68: 32 for T2, 18.4 and 59: 41 for and 15.9 and 48: 52 for T4 groups along with wheat straw ad lib. and green maize @ 0.5 kg/I 00 kg body weight, in a 4 x 41alin square design to study the rumen metabolites, Calves in Tl, T2, T3 and T4 were fed CP, respectively, 20% higher, normal, 10 and 20% lesser than the recommendations, After 21 days duri'ng each switch over, the rumen liquor samples from each animal were drawn at 0, 2,4,6 and 8 hr offceding and pH, TYFA, individual VFA, total N, NH, N, urea N and non ammonia nitrogen (NAN) were assessed. The variation in pH and TYFA because of hours of feeding and treatments was significant. The ruminal pH decreased over the period of sampling from 0 to 8 hr of feeding, except in T4 whete the minimum value was seen at 6 hr. The TYFA concentration showed a significant decreasing trend by decreasing the CP and RDP content and incteasing the UDP content in the diet. Similarly, the molar concentration of individual YFAs (acetate, propionate and butyrate) also decreased from T1 to T4 as the UDP content increased in that order. However, the A/P ratio progressively increased (P<0.0 1) ftom T1 to T4, Among the treatments, the concentrations of toral N, NH3 N and urea N differ significantly due to quantity and quality of dietary protein, these were higher in T1 followed by T2, T3 and T4, The concentration of NAN was higher (P<0.01) in T1 than that in T2, T3 and T4, however, it did not differ in T3 and T4. It is concluded that by increasing the quantity of UDP and by decreasing the quantity of total CP even up to 20% of NRC (1989) in the diet of ruminants, the rumen pH and nitrogen fractions remained optimum, while the volatile fatty acid concentration was below the normal due to decreased rumen fenmentation rate, This has an importance in the tropics where the limited proteinaceous feeds for ruminants are to be utilized efficiently.