The evaluation of metabolizable protein content of some indigenous feedstuffs used in ruminant nutrition

Aim: To determine the metabolizable protein (MP) content of common indigenous feedstuffs used in ruminant nutrition using in situ method. Materials and Methods: Nine ruminant feeds such as maize grain (MG), groundnut cake (GNC), mustard oilcake (MOC), cottonseed cake (CSC), deoiled rice bran (DORB), wheat bran (WB), berseem fodder (BF), maize fodder (MF) and sorghum fodder (SF) were included in this study. Each test feed was dried, ground and chemically analysed for proximate principles (DM, CP, EE, OM, Total ash), fiber fractions (NDF, ADF, cellulose, hemicellulose, lignin), NDICP and ADICP. Two adult fistulated bulls were used for evaluating the protein degradation characteristics of each test feed using the nylon bag method. Metabolizable energy (ME) content of the test feeds were predicted from their chemical composition data using summative approach of NRC (2001) model. The equations of AFRC (1992) were used to predict the rumen degradable protein (RDP), digestible microbial protein (DMP), digestible undegraded feed protein (DUP) and MP content of test feeds. Results: The MP content of MG, GNC, MOC, CSC, DORB, WB, BF, MF and SF was found to be 95.26, 156.41, 135.21, 125.06, 101.68, 107.11, 136.81, 72.01 and 76.65 g/kg DM, respectively. The corresponding ME (MJ/kg DM) content of the test feeds was 13.66, 13.12, 13.65, 10.68, 9.08, 11.56, 9.64, 8.33 and 8.03, respectively. Among the test feeds, GNC contained the highest and MF contained the lowest MP per kg DM. Conclusion: It was concluded that the degradability of crude protein (CP) of the test feeds can be used in MP determination and diet formulation. Feed CP content is not available as such at intestinal level in ruminants as a definite part of it undergoes extensive microbial degradation in rumen. The pattern and extent of such degradation do influence the amount of protein presented to lower digestive tract (MP) for absorption and utilization in ruminants. It was also found that the MP content of a feed is not constant as that of its CP content as it entirely depends on the degradation characteristics in a given animal.


Introduction
estimates of available microbial and dietary escape protein [1,2] and are potentially more accurate than the In ruminants, ration balancing based on CP CP systems are.content of feedstuffs has been considered as obsolete The CP degradability can be measured by in vivo due to the activities of ruminal microorganisms such as and in vitro methods.In vitro methods are quicker for degradation of feed protein, synthesis of microbial screening of large number of feeds but do not give protein and passage of both undegraded feed protein protein degradability in absolute terms.In situ method and microbial protein to lower intestine.Therefore of Agricultural Research Council (ARC) using nylon protein evaluation system in ruminants is now based on bag is widely accepted to measure the degradability, RDP and RUP.Mere classification of feed protein into which is analysed by a computer model developed by RDP and RUP also could not solve the purpose of Orskov and McDonald [3].Several attempts were balancing ruminant diets for adequate protein as it did made to estimate the MP content of animal feeds by not provide any information regarding the protein various methods.Islam et al. [4] evaluated MP content available to the animals in the lower intestinal tract for of whole crop rice silage at different stages of harvest, productive purposes.In such a situation, the concept of which is usually not a common ruminant feed under MP content of ruminant feeds seems more logical and Indian conditions.Similarly MP content of Wolffia scientific as it represents the actual quantity of true meal was evaluated by Pooponpan et al. [5] in broilers.protein or amino acids that gets absorbed by the animal Rahbarpour et al. [6] used the nylon bag (in situ) [1].MP systems define the animal's requirement using technique to determine the MP value of tomato pomace.[3].MP content of the test ensure proper and complete drying of samples.The feeds were estimated using the equations of AFRC dried samples were ground through 1mm sieve using [15].The ruminal outflow rate of feed DM and CP were electrically operated willey mill.The ground samples assumed to be 5%/h as per Ramirez et al. [16].The were stored in bottles of 200 ml capacity, labeled factor 'y' for calculating the microbial yield was taken properly and stored for further analysis.
as 10 for growing animal as per AFRC.

Selection and feeding of fistulated animals: Two adult Statistical analysis:
The results obtained were fistulated bulls were selected from institute herd analyzed using software package SPSS version 16.0 (NDRI).They were fed a diet containing 40% concen- [17].Means were compared using one way analysis of trate, 40% green berseem and 20% wheat straw.The variance (ANOVA) test at 5% level of significance.feed was offered in equal proportion for every 8 h to

Results and Discussion
maintain a relatively constant rumen microbial environment.
Chemical composition: The chemical composition of test feeds is presented in Table-1.As expected, the oil In situ rumen incubation of feeds: Samples of total dry cakes i.e.GNC, MOC and CSC contained higher CP, matter, approximating 5 g were placed into nylon bags while among green fodders, berseem had highest CP (length 150x90 mm, 44 µm pore diameter and 350 because of its leguminous nature.CSC, DORB and WB mesh size) separately.Roughages were placed into contained higher NDF and ADF among concentrate nylon bags in 7 replicates and concentrates placed in 6 feeds, while MF and SF recorded higher NDF and ADF replicates.The bags were tied with nylon threads.Each among green fodders.The obtained chemical composample was taken in quadripulates and experiment was sitions of test feeds are different compared to reports of repeated twice.The bags were tied to an iron chain and NRC [14] and AFRC [15].These differences may be then suspended in the rumen of fistulated animals.related to variance in environmental conditions, variety Then the bags were taken out at 0, 2, 4, 8, 16, 24, 48 and of feeds, maturity during time of cut, oil extract assay 72 h interval for roughages and 0, 2, 4, 8, 16, 24 and 48 and other processing factors.h interval for concentrates.The bags were then washed thoroughly under running tap water until clear water TDN, ME and fermentable ME (FME) content: The

Table - 1
: The chemical composition of feedstuffs (% DM) DM degradability.The results for concentrate feeds are slightly higher TDN values for green fodders than the in accordance to the findings of Singh and Kundu [19].present results.Such differences in feed chemical Sampath et al. [20] reported similar values of maize composition again can be attributed to the variations in fodder.Among concentrate feeds, maize grains had

Table - 2
: TDN, ME and FME content of feedstuffs