Rumen undegradable protein

Wang and Johnson (2001) reported on test measurement methods that were major indicators of soybean oil quality. These tests included peroxide value, anisidine value, FFA content, phospholipid content, total tocopherol content, oxidative stability index, color, and moisture content. For soybean meal, they reported on urease activity, protein dispersibility index (PDI), rumen bypass or rumen undegradable protein, trypsin inhibitor activity, moisture content, residual oil content, protein content, fiber content, color, amino acid profiles, and protein solubility under alkaline (KOH) conditions. 

Not all dietary proteins are degraded by the microbial population, and some pass unaltered or with minimal alteration into the small intestine where they are digested much as in a nonruminant animal. Dietary proteins that are not degraded by the ruminal microbes are referred to as rumen-undegradable protein (RUP NRC, 2001). This fraction also is sometimes referred to as escape or bypass protein. The total amount of protein that reaches the intestine for digestion is the sum of microbial protein and RUP, and is called metabolizable protein (MP NRC, 2001). This is the actual supply of digested proteins that furnishes AAs to the animal. 

Calculation of intestinal digestibility values for rumen undegradable protein... 

The values for true intestinal digestibility (TId) of rumen undegradable protein (RUP) were calculated when possible using the results obtained by the technique of mobile nylon bags in the intestine (UMR INRA-ENSAR). In order to increase the diversity of the feed materials, these data were completed by measurements performed using a similar methodology by around 15 other laboratories renowned for their reliability. To be included, each laboratory had to have tested at least 10 feed materials. 

Post-ruminal casein infusions have often been used to study milk and protein yield responses to dietary protein. Casein infusion studies have some methodological benefits in examining potential MPY responses, since the change in input of rumen undegraded protein (RUP) can accurately be determined and the effects on rumen metabolism and feed intake are marginal. 

It is well known that methionine (Met) and lysine (Lys) are two of the most limiting amino acids (AA) for milk and protein production in lactating dairy cows fed corn-based diets (Schwab et al., 2003 Rulquin, 2004). The NRC (2001) suggested concentrations of Met and Lys of 2.4% and 7.2% on a metabolizable protein (MP) basis, respectively, in order to maximize the use of MP for milk and milk protein yield by lactating dairy cows. However, it should be taken in consideration that these concentrations are hardly achieved. Nutritionists have two methods to fed lactating dairy cows with AA balanced diets one is to incorporate feeds with a high level of rumen undegradable protein, and the other is to supplement the diet with ruminally protected (RP) synthetic AA (Schwab et al., 2003). The aim of this work was to assess the bioavadabUity of a RP D,L-Met and a RP L-Lys HCl products by a standardized blood test (Sudekum et al., 2004). 

Noftsger, S. and N.R. St-Pierre, 2003. Supplementation of methionine and selection of highly digestible rumen undegradable protein to improve nitrogen efficiency for milk production. J. Dairy Sci. 86. 958-969. 

Antoniewicz, A.M., A.M. van Vuuren, C.J. Van der Koelen and I. Kosmala, 1992. Intestinal digestibility of rumen undegraded protein of formaldehyde treated feedstufifs measured by mobile bag and in vitro technique. Anim. Feed. Sci. Technol. 39, 111-124. 

Boucher, S.E., S. Calsamiglia, C.M. Parsons, H.H. Stein, M.D. Stem, PS. Erickson, P.L. Utterback and C.G. Schwab, 2009. Intestinal digestibility of amino acids in rumen undegradable protein estimated using a precission-fed cecectomized rooster bioassay Soybean meal and SoyPlus. J. Dairy Sci. 92, 4489-4498. 

The rumen undegraded protein (%) (RUP) was calculated by applying 2 different rates of passage for insoluble (Icj) and soluble (tg) N ... 

Table 1. Degradation rates and rumen undegradable protein (RUP) of the samples. 

The chemical nature of crude protein in feedstuffs is the primary factor determining how rapidly it is degraded to ammonia or escapes microbial degradation. To compare feedstuffs, feed nitrogen can be divided into NPN, true protein, and unavailable fractions, which Pichard and van Soest (1977) labeled as the A, B, and C fractions, respectively (Fig. 18.3). The A fraction is rapidly attacked by rumen bacteria and converted to ammonia. Approximately 20% of the crude protein in SBM is in the A fraction and is degraded in the rumen at a rate of 300%/h (NRC, 1996). In contrast, a more undegradable protein source like distillers grains has 6% of the crude protein in the A fraction. 

The second type of supplement required for straw is one that provides the animal with additional protein that is not degraded in the rumen (digestible undegradable protein see Chapter 13). This often stimulates intake (see Chapter 17) and ensmes a... 

AA = amino acids, ADIN = acid detergent insoluble nitrogen, DUP = digestible undegradable protein, ERDN = effective rumen degradable nitrogen, LCFA = long-chain fatty acids,... 

Broderick, G. A, 1978. In vitro procedures for estimating rates of ruminal protein degradation and proportions of protein escaping the rumen undegraded. J. Nutr. 108, 181-190. 

Hvelplund, T, 1985. Digestibility of rumen microbial protein and undegraded dietary protein estimated in the small intestine of sheep and by in sacco procedure. Acta Agric. Scand. Suppl. 25, 132-144. 

Hvelplund, T, M.R. Weisbjerg and L.S. Andersen, 1992. Estimation of the true digestibility of rumen undegraded dietary protein in the small intestine ofruminantsbythe mobile bag technique. Acta Agric. Scand. Sect. A, Animal Sci. 42, 34-39. 

The extent to which dietary protein is degraded to ammonia in the rumen, and conversely the extent to which it escapes rumen degradation and is subsequently digested in the small intestine, is discussed in Chapters 10 and 13. At this point it is sufficient to emphasise that with most diets, the greater part (and sometimes all) of the protein reaching the ruminant s small intestine will be microbial protein of reasonably constant composition. The lesser part will be undegraded food protein, which will vary in amino acid composition according to the nature of the diet. 

The UK metabolisable protein system divides the requirement of an animal into that which is required for supplying the needs of the rumen microbes and that which is required at tissue level. After estimating the contribution of microbial protein to satisfying this demand, the requirement for undegraded dietary protein is calculated. 

---