SHORT COMMUNICATION Ruminal degradability of neutral detergent insoluble protein of selected protein sources A. F. Mustafa 1, D. A. Christensen 2, and J. J. McKinnon 2 1 Department of Animal Science, Macdonald College of McGill University, 2111 Lakeshore Road, Ste-Anne-de-Bellevue, Quebec, Canada H9X 3V9; 2 Department of Animal and Poultry Science, University of Saskatchewan, 72 Campus Drive, S7N 5B5, Saskatoon, Saskatcherwan, Canada Received 26 April 2001, accepted 1 August 2001. Mustafa, A. F., Christensen, D. A. and McKinnon, J. J. 2001. Ruminal degradability of neutral detergent insoluble protein of selected protein sources. Can. J. Anim. Sci. 81: 601 603. Ruminal degradability of neutral detergent insoluble protein (NDICP) for different protein sources was measured using two fistulated cows. Effective degradability of NDICP was highest (P < 0.05) for distillers grains, intermediate (P < 0.05) for canola meal heated at 125 C and lowest (P < 0.05) for canola meal heated at 145 C. Results showed variations in ruminal degradability of NDICP between protein sources. Key words: Neutral detergent insoluble protein, ruminal degradability Mustafa, A. F., Christensen, D. A. et McKinnon, J. J. 2001. Dégradation des protéines insolubles dans le détergent neutre de diverses sources dans le rumen. Can. J. Anim. Sci. 81: 601 603. Les auteurs ont mesuré la capacité de dégradation des protéines insolubles dans le détergent neutre (PIDN) de diverses sources dans le rumen de deux vaches fistulées. Les drêches de distillerie sont les PIDN les plus facilement dégradables (P < 0,05); viennent ensuite le tourteau de canola chauffé à 125 C (P < 0,05) et le tourteau de canola chauffé à 145 C (P < 0.05) Les résultats indiquent que la capacité de dégradation des PIDN dans le rumen varie avec l origine des protéines. Mots clés: Protéines insolubles dans le détergent neutre, capacité de dégradation dans le rumen 601 Ruminal kinetic parameters and degradability of protein sources are usually measured based on total CP rather than specific protein fractions. According to Sniffen et al. (1992), dietary true protein can be divided into rapidly, intermediately, and slowly degradable fractions based on rates of ruminal degradation. Degradation rates of these protein fractions are important inputs that will affect the ability of the National Research Council (NRC 1996) computer model to accurately predict animal performance. Neutral detergent insoluble protein is the main protein fraction in several plant protein sources. The NDICP is slowly degraded in the rumen and constitutes a major portion of the ruminal undegraded protein content (Sniffen et al. 1992; NRC 1996). Degradation rates and ruminal escape values of NDICP for some forages such as alfalfa and eastern gamagrass have been determined by Coblentz et al. (1999). However, such values for other protein sources with high levels of NDICP have not been determined. Three samples each of wheat wet distillers grains and heated canola meals were used. The wet distiller s grain samples were part of a previous study (Ojowi et al. 1997) and the heated canola meals were obtained by dry-heating commercially available canola meal at 125 and 145 C for 20 min. Moisture, Kjeldahl N and acid detergent fiber were determined according to the procedures of the Association of Official Analytical Chemists (AOAC 1990). Samples were also analyzed for neutral detergent fiber (NDF) without the use of sodium sulfite (Van Soest et al. 1991). This was done because sodium sulfite reduces the NDF content by solubilizing part or all of the NDICP (Hintz and Mertens 1996). Acid detergent insoluble protein (ADICP) and NDICP contents were determined by analyzing the acid detergent fiber and NDF residues, respectively, for Kjeldahl nitrogen (Licitra et al. 1996). Ruminal undegraded protein (RUP) for the protein sources was determined following 12 h (O Mara et al. 1997; Klemesrud et al. 1997). Duplicate samples of each protein source were weighed into nylon bags (9 12 cm; 41 µm pore size) and incubated in the rumen of a ruminally fistulated non-lactating Holstein cow for 12 h. Following removal from the rumen, the bags were rinsed in tap water and dried at 55 C for 48 h. To measure ruminal kinetic parameters and degradability of NDICP, equal portions (100 g) of the three samples from each protein source were composited to obtain a single sample. Duplicate samples of each protein source were then weighed into nylon bags and incubated in the rumens of two ruminally fistulated non-lactating Holstein cows for 6, 12, Abbreviations: ADICP, acid detergent insoluble protein; CP, crude protein; NDF, neutral detergent fiber; NDICP, neutral detergent insoluble protein; RUP, ruminal undegraded protein
602 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 1. Chemical composition and ruminal undegraded protein content of selected protein sources CP NDF Corrected NDF NDICP ADICP RUP (g kg 1 ) (g kg 1 ) (g kg 1 ) z (g kg 1 of CP) (g kg 1 of CP) (g kg 1 of CP) Wet distillers grains 259b 724a 588a 528b 58b 415c Heated canola meal y 394a 435c 255c 452c 69b 751b Heated canola meal x 398a 577b 291b 725a 363a 876a SEM w 5.2 4.5 4.4 7.6 4.3 10.2 z Corrected for associated NDICP. y Heated at 125 C for 20 min. x Heated at 145 C for 20 min. w SEM = pooled standard error of the mean. a c Means in the same column followed by different letters are different (P < 0.05). Table 2. Ruminal kinetic parameters and effective degradability of neutral detergent insoluble protein for selected protein sources Ruminal kinetic parameters Soluble Slowly degradable Degradation rate Effective degradability (% of CP) (% of CP) (% h 1 ) (%) Wet wheat distillers grains 15.3a 80.4a 1.3 31.5a Heated canola meal (125 C 20 min) 2.7b 50.9b 2.0 11.9b Heated canola meal (145 C 20 min) 1.3b 27.1c 1.8 5.9c SEM z 0.47 2.61 0.28 0.52 z SEM = pooled standard error of the mean. a c Means in the same column followed by different letters are different (P < 0.05). 24 and 48 h. The animals were fed twice daily a 50:50 forage:concentrate diet (dry matter basis). The forage consisted of 50% barley silage and 50% alfalfa hay. Care for the cows was according to the guidelines of the Canadian Council on Animal Care (1980). Bags removed from the rumen were handled in a similar manner as described previously. Zero hour disappearance was estimated by rinsing duplicate bags of each protein source in tap water. Nylon bag residues were analyzed for moisture and NDICP as described previously. Disappearance of NDICP at each incubation time was determined by subtracting residual NDICP from original NDICP. Soluble, slowly degradable and rate of degradation of the slowly degradable NDICP were estimated using the equation of Ørskov and McDonald (1979). These kinetic parameters were estimated using an iterative nonlinear regression procedure of the SAS Institute, Inc. (1999). Effective degradability of NDICP was estimated using the equation of Ørskov and McDonald (1979) assuming a rumen outflow rate of 5% h 1. Chemical composition and RUP data were analyzed as a completely randomized design using the General Linear Model of the SAS Institute, Inc. (1999). Data of the NDICP kinetic parameters and effective degradability were analyzed as a randomized complete block design where cows served as blocks. Means were separated with the Student- Newman Keul s test. Neutral detergent insoluble protein ranged from 452 g kg 1 of CP for canola meal heated at 125 C to 725 g kg 1 of CP for canola meal heated at 145 C (Table 1). Acid detergent insoluble protein level was higher (P < 0.05) in canola meal heated at 145 C than in wet distillers grains or canola meal heated at 125 C, which had a similar ADICP level (64 g kg 1 of CP). Ruminal undegraded protein ranged from 415 g kg 1 of CP in wet distillers grains to 876 g kg 1 of CP in canola meal heated at 145 C (Table 1). The rapidly degradable NDICP fraction was higher (P < 0.05) for wet distillers grains than for heated canola meal (Table 2). Because NDICP is associated with the cell wall, the proportion of the rapidly degradable fraction NDICP is generally small. Coblentz et al. (1999) determined in situ NDICP degradation characteristics for different plant tissues of alfalfa and gamagrass. The authors reported values for rapidly degradable NDICP ranging from 1.1% of NDICP for alfalfa stems to 10.7% of NDICP for gamagrass stems. The slowly degradable NDICP fraction was highest (P < 0.05) for wet distiller s grain, intermediate for canola meal heated at 125 C and lowest (P < 0.05) for canola meal heated at 145 C (Table 2). These results suggest that NDICP from canola meal heated at 145 C is potentially less available for ruminal degradation than the other protein sources. The high ADICP likely contributed to the smaller slowly degradable NDICP fraction of the canola meal heated at 145 C relative to the other two protein sources. The rate of degradation of the slowly degradable NDICP fraction was similar for the three protein sources (average 1.7% h 1 ). Rates of degradation of NDICP reported in this study are higher than those reported by the NRC (1996) for the slowly degradable true protein (B3) fraction. According to the NRC (1996), the rate of degradation of the B3 true protein fraction for distiller s grains and canola meal averages 0.10 and 0.20% h 1, respectively. In accordance with our results, Coblentz et al. (1999) also reported a higher degradation rate for the NDICP of alfalfa than the value reported by NRC (1996) for the B3 true protein fraction. Effective degradability of NDICP was highest (P < 0.05) for wet distillers grains, intermediate (P < 0.05) for canola meal heated at 125 C and lowest (P < 0.05) for canola meal heated at 145 C (Table 2). The higher ruminal degradability of NDICP for wet distillers grains is likely a reflection of their high soluble NDICP fraction. These results suggest
MUSTAFA ET AL. NEUTRAL DETERGENT INSOLUBLE PROTEIN AND RUMINAL DEGRADABILITY 603 that in some protein sources such as wet distillers grains, a considerable amount of NDICP is susceptible to microbial degradation in the rumen. However, in other protein sources such as canola meal heated at 145 C, the NDICP fraction is almost completely undegraded in the rumen. Differences in ruminal escape NDICP values have also been reported for forages (Coblentz et al. 1999). Assuming a ruminal flow rate of 6% h 1, Coblentz et al. (1999) reported a ruminal escape NDICP value of 57% for alfalfa and 48 to 64% for gamagrass. It is clear that more NDICP from the two heated canola meals than from wet distillers grains will escape ruminal degradation and become potentially available for postruminal digestion. Intestinal digestibility of ruminal escape NDICP has not been determined in the present study. However, the intestinal availability of heated canola meal has been related to the ADICP level (Moshtaghi Nia and Ingalls 1992; McKinnon et al. 1995). McKinnon et al. (1995) found that while canola meal heated at 145 C had a higher ruminal escape protein value than canola meal heated at 125 C, its postruminal availability was compromised by high ADICP level. The results of this study show variations in ruminal kinetic parameters and degradability of NDICP among protein sources, suggesting that the contribution of NDICP to the ruminal microbial N pool varies from one protein source to another. Association of Official Analytical Chemists. 1990. Official methods of analysis 15th ed. AOAC, Arlington, VA. Canadian Council on Animal Care. 1980. Guide to the care and use of experimental animals. Vol. 1. CCAC, Ottawa, ON. Coblentz, W. K., Fritz, J. O., Fick, W. H., Cochran, R. C., Shirley, J. E. and Turner, J. E. 1999. In situ disappearance of neutral insoluble nitrogen from alfalfa and eastern gamagrass at three maturities. J. Anim. Sci. 77: 2803 2809. Hintz, R. W. and Mertens, D. 1996. Effects of sodium sulfite on recovery and composition of detergent fiber and lignin. J. AOAC. Int. 79: 16 22. Klemesrud, M. J., Klopfenstein, T. J., Lewis, A. J., Shain, D. H. and Herold, D. W. 1997. Limiting amino acids in meat and bone meal and poultry by-product meals. J. Anim. Sci. 75: 3294 3300. Licitra, G., Hernandez, T. M. and Van Soest, P. J. 1996. Standardization procedures for nitrogen fractionation of ruminant feeds. Anim Feed Sci Technol 57: 347 358. McKinnon, J. J., Olubobokun, J. A., Mustafa, A. F., Cohen, R. D. H. and Christensen, D. A. 1995. Influence of dry heat treatment of canola meal on site and extent of nutrient disappearence of canola meal. Anim. Feed Sci. Technol. 56: 243 252. Moshtaghi Nia, S. A. and Ingalls, J. R. 1992. Effect of heating canola meal protein degradation in the rumen and digestion in the lower gastrointestinal tract of steers. Can. J. Anim. Sci. 72: 83 88. National Research Council. 1996. Nutrient requirements of beef cattle. 7th rev. ed. National Academy Press, Washington, DC. Ojowi, M. O., McKinnon, J. J., Mustafa, A. F., Christensen, D. A. 1997. Evaluation of wheat-based wet distillers grains for feedlot cattle. Can. J. Anim. Sci. 77: 447 454 O Mara, F. P., Murphy, J. J. and Rath, M. 1997. The amino acid composition of protein feedstuffs before and after ruminal incubation and after subsequent passage through the intestines of dairy cows. J. Anim. Sci. 75: 1941 1949. Ørskov, E. R. and McDonald, I. 1979. The estimation of protein degradability in the rumen from incubation measurements weighed according to rate of passage. J. Agric. Sci. (Camb.). 92: 499 503. SAS Institute, Inc. 1999. SAS/STAT user s guide. Version 8. SAS Institute, Inc., Cary, NC. Sniffen, C. J., O conor, D. J., Van Soest, P. J., Fox, D. J. and Russell, J. B. 1992. A net carbohydrate and protein system for evaluating cattle diets. II. Carbohydrate and protein availability. J. Anim. Sci. 70: 3562 3577. Van Soest, P. J., Robertson, J. B. and Lewis, B. A. 1991. Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74: 3583 3597.
This article has been cited by: 1. A. Velásquez, G. Pichard. 2010. Effects of rumen fluid pre-incubation on in vitro proteolytic activity of enzymatic extracts from rumen microorganisms. Animal Feed Science and Technology 162:3-4, 75-82. [Crossref]