Undegraded Dietary Protein Research Articles

Protein Supply from Undegraded Dietary Protein

A summary of in vivo estimates of the amount of dietary protein from individual feedstuffs that escapes microbial degradation in the rumen is presented. Values range from approximately 20% for protein in barley, oats, wheat, and alfalfa silage to 65 to 70% for protein in fish meal and animal by-products. In vitro or in situ methods for estimating protein degradation can be used, but at this stage of development, the methodology is more useful in providing a relative ranking of feedstuffs on the basis of protein degradation than in providing absolute estimates of protein degradation. A number of factors influence protein breakdown in the rumen, including extent of crosslinking in the protein (disulfide bonds), retention time in the rumen, protein solubility, and processing and storage effects on protein. It is important to consider the amino acid content of the undegraded dietary protein, particularly lysine and methionine, two amino acids likely to be limiting for milk production. Strategies for using protected proteins in dairy cattle diets are discussed.

A further trial of the use of fishmeal together with reduced concentrate in a commercial dairy herd

This experiment was designed to evaluate whether milk yields could be maintained while reducing concentrate feed intake, and therefore placing greater reliance on forage intake, and including sugar beet pulp as a source of highly digestible but non-starchy concentrate, and fish meal as a source of high quality, undegraded dietary protein. It was undertaken on a commercial farm as the continuation of similar experiments on two other commercial farms reported earlier (Pike et al 1984).

Performance of friesian bulls fed intensively with compound feeds

Over a period of 2 years from 1982 to 1984, six feeding trials were carried out on a total of 307 Friesian bulls to investigate the effects of energy and protein levels in compound feed. All animals were fed ad-lib compound diets with free access to barley straw and water. In four of the six trials the bulls were implanted with Ralgro (zeranol, Crown Chemical Company Limited), once at the start of the trial and again after 90 days. The various dietary treatments in the different trials are given below. Theoretical undegradable dietary protein was calculated using the known degradability of raw materials in the compound feed.

Influence of Dietary Protein Concentration and Degradability on Milk Production, Composition, and Ruminal Protein Metabolism

Four groups of cows in early lactation, each group containing one mature cow and three cows in first lactation, were in a 4×4 Latin-square arrangement of treatments for us to study influences of altering quantity of undegraded dietary crude protein and quantity of crude protein on milk production and composition. Diets supplemented with protein sources were 1) soybean meal positive control (22.7% crude protein), 2) whole cottonseed-corn gluten meal (14.7% crude protein), 3) extruded whole soybean (14.5% crude protein), or 4) soybean meal supplemented (15.7% crude protein). Concentrate and sorghum silage were fed in a ratio of 62:38 dry matter. Dry matter intake was not influenced by dietary crude protein concentration or source. Cows consuming diet 2 produced less milk, milk protein, total solids, and solids-not-fat than cows receiving diets 1 and 4. Efficiency of conversion of dietary crude protein to milk protein was highest for cows receiving diet 3 and lowest for diet 1.Trial 2, a 4×4 Latin-square trial for collection of abomasal digesta, had four ruminal and abomasal cannulated steers and the four diets from the lactation trial; the trial was to determine the influence of source and concentrations of protein on quantity of protein reaching the abomasum daily. Crude protein intake by steers fed diet 1 was greater than for the other three diets. Percentages recovery of dietary crude protein were 122 and 130 for treatments 2 and 3, intermediate for treatment 4 (107%), and lowest for diet 1 (88.0%); crude protein digestibility in the total tract was highest for steers receiving diet 1.

The response of store lambs to protein supplementation of alkali treated straw based diets

Factors affecting voluntary food intake (VFI) in ruminants are well documented and suggest that both physical and chemical factors are involved. An understanding of VFI controls is important for the formulation of economical diets to achieve maximum levels of production.The effect of protein supply on VFI is unclear. While the need for rumen degradable protein (RDP) to maximise microbial activity and consequently VFI is clearly established ARC (1960), the effect of undegraded dietary protein (UDP) on VFI is equivocal.

Use of fish heal to reduce compound feed usage in high yielding dairy herds

Compound feeds are frequently used at a fixed rate of 0.36kg to 0.40kg/kg milk produced, in addition to forage and other home-grown feeds. Such linear scales take no account of the curvilinear response of milk yield to concentrate feed intake, nor of the substitution effect of concentrate feed upon forage intake. In high-yielding herds, the use of fixed rate scales can result in the provision of concentrate feeds in excess of 10kg/d. An experiment was designed to evaluate whether milk yields could be maintained while reducing concentrate feed intake, and therefore placing greater reliance on forage intake, and including sugar-beet pulp as a source of highly digestible but non-starchy concentrate, and fish meal as a source of high quality undegraded dietary protein

Studies on the protein requirements of growing cattle. Effects of differing intakes of protein and energy on growth and nitrogen metabolism in young entire males.

Forty-eight Friesian entire male cattle, with an initial live weight (LW) of 135 kg, were used in two experiments to measure the response to increasing levels of dietary protein (9-11 and 7.5-10.5 g nitrogen X 6.25/kg LW0.75) at differing energy levels (800-900 kJ metabolizable energy (ME) kg LW0.75) over 120-d periods. Digestibility and N balance measurements were also made during the experiments. The diets, which were based on barley and soya-bean meal, were individually fed twice daily. In a third experiment, similar diets were given to four similar animals fitted with intestinal cannulas, at constant energy intake but with variations in dietary protein of 7.5-13.5 g N X 6.25/kg LW0.75. Chromic oxide paper was used as a digesta marker. Positive responses in LW gain and N balance to additional protein were found in both experiments but these were significant (P less than 0.05) only in the second experiment and were associated with significant (P less than 0.01) increases in the digestibility of modified acid-detergent fibre and ME intake. Mean values, which were not significantly different between treatments, for the degradability of dietary protein in the rumen and the efficiency of microbial protein synthesis were 0.57 and 31.3 g/kg organic matter apparently digested in the rumen respectively. Corresponding values obtained by regression analysis were 0.56 and 28.2. The results in general support the Agricultural Research Council (1980) proposals and suggest that undegraded dietary protein was not limiting in these experiments but that rumen-degradable protein levels were limiting on some treatments. Regression analysis indicated that the mean response to additional protein (g LW gain/g N X 6.25) per kg LW was 0.52 in Expt 1 and 0.51 in Expt 2. These responses could be largely explained by increases in ME intakes. Measurements of duodenal amino acid flow showed marked increases in essential amino acids (EAA) across the rumen. However, EAA flows, were not significantly increased at higher N intakes suggesting that protein per se was not limiting in these experiments.

The rate of addition of formic acid to grass at ensilage and the subsequent digestion of the silage in the rumen and intestines of sheep

AbstractThe main object of the experiment was to assess the effect of the relative proportion of non‐protein nitrogen (NPN) to total nitrogen in silage on digestion in the sheep. Four unwilted perennial ryegrass silages were made with the addition of formic acid at 0, 2·2, 4·2 and 5·2 litres t‐1 to provide foods with NPN proportions reducing from 0·26 to 0·20 of the total N. The digestion of the silages was studied in a 4 × 4 Latin Square experiment with sheep cannulated in the rumen, proximal duodenum and terminal ileum.Results for organic matter (OM), cellulose and N showed no major difference between silages in their digestion in the rumen, small intestine and caecum and colon, though small differences (P <0·25) in rumen fermentation pattern and in the proportion of digestible OM disappearing in the small intestine were observed. Concentrations of ammonia N in the rumen and rates of rumen bacterial protein synthesis did not differ significantly between silages and there were no treatment effects on the passage of individual amino acids to the small intestine. The results indicate that the proportions of NPN to total N in the silages examined had little influence on the efficiency of silage N utilization in the rumen or on the passage of undegraded dietary protein to the small intestine.

8.4 The Effect of the Quantity and Composition of Ruminally Degraded Nitrogen on Microbial Nitrogen Synthesis and Diet Formulation

Recent proposals (ARC, 1980) have clearly identified the need to supply adequate ruminally degradarle nitrogen (RDN) if rumen microbial protein yields are to be optimized and they provide a basis on which the required quantities of RDN can be calculated. However, apart from the suggestion that urea is used with only 80% of the efficiency of degraded protein N as a source of RDN in the synthesis of microbial protein, the present scheme fails to qualify the RDN composition (i.e. protein N (PN) vs. NPN) most likely to promote optimal microbial synthesis.Cottrill, Beever and Osbourn (1982) examined the isonitrogenous supplementation of maize silage fed to growing calves with four different NPN:PN ratios in the supplement and showed a 29% increase in total duodenal amino acid (DAA) flow at the first increment of PN (fish meal). Of this increase, almost 87% could be accounted for by an increased duodenal microbial protein (DMP) flow. Higher levels of PN inclusion did not promote any further increases in DAA, despite increases in undegraded dietary protein (UDP) flow, due to a significant reduction in DMP flow. From these data, a further examination of total RDN supply and its composition in relation to MP synthesis was undertaken and the results are presented in this paper.

Digestion of a ground and pelleted diet in the stomach and intestines of young sheep from two breeds

Some aspects of digestion were studied in small groups of fistulated wether lambs from two breeds, Dorset Horn and Corriedale. The Iambs were given a ground and pelleted diet of equal parts hay and concentrates once daily at two levels of intake. At the same liveweight (25 kg), the higher intake was associated with reduced digestion of organic matter (OM) and fibre in the whole gastro-intestinal tract; rumen mean retention times were also reduced, as was the proportion of OM digestion which occurred in the rumen. An increase in the amount of protein entering the intestines appeared to be composed of both undegraded dietary protein and microbial protein. Despite a reduction in the digestibility of non-ammonia nitrogen in the intestines, more crude protein was digested there per unit of digestible OM intake (25.9 v..23.6%; P < 0.05). Differences between the breed groups were smaller than those associated with level of feeding. Nevertheless, particularly at lower relative intakes, rumen mean retention times were longer, rumen digesta content was greater, and rumen OM and fibre digestion tended to be greater in the Dorset Horn lambs; crude protein digestion in the intestines per unit of digestible OM intake also tended to be less at the low intakes. More than three-quarters of the cellulose digestion but less than half the hemicellulose digestion occurred in the rumen. The proportion of the urea synthesized that was degraded in the gastrointestinal tract (0.24-0.30) was consistently lower in these lambs than has been reported for adult sheep.

The application of modern concepts of ruminant protein nutrition to sheep-production systems

New systems for estimating the requirements of ruminants for dietary protein involve separate estimates of the extent to which microbial and undegraded dietary protein meet the animal's net requirements for amino acids. The paper provides a brief review of the factors influencing both the synthesis of microbial protein and the amounts of dietary protein that escape the rumen undegraded. Although quantitative data on many of these factors are now emerging, the extensive nature of most sheep-production systems makes their application in a precise quantitative manner difficult. It is suggested that considerable improvements in production could be achieved by using the principles in a qualitative sense. For low-producing animals such as dry ewes, pregnant ewes up to a few weeks before lambing, and ‘store’ lambs, microbial protein will meet the animal's net requirements for amino-acid nitrogen provided that the animals have not been previously subjected to a specific protein deficiency. In contrast, the maximal yield of microbial protein will not meet the net requirements of high-producing animals, such as young, fast-growing lambs, and ewes in the final few weeks of pregnancy and during early lactation. These animals require protein supplements which at least in part escape degradation in the rumen.

The application of new ideas on the protein requirements of the dairy cow.

The intake of undegradable dietary protein in a cow's early lactation may be a major factor in determining peak yield. The natural degradability of proteins varies with different feedstuffs. Maturity of crop, use of additives, drying or grinding all affect the degradability. Time spent in the rumen is an important factor in the amount of protein degraded.

Capacity for Digestion and Effects of Composition of Absorbed Nutrients on Animal Metabolism

The capacity for ruminal fermentation and postruminal digestion have been briefly discussed. From the available data it would seem that, provided the diets are highly digestible and easily degradable, the capacity for rumen fermentation far exceeds the energy needs of the host ruminant animals, though, as is well known, this is not so with many roughage diets. For most types of animal production, microbial protein and undegraded dietary protein provide sufficient or excess protein for the need of the host animal. For some systems, however, (e.g., early weaned lambs and calves and high producing dairy cows) the need is not met and protein must be given, which in order to be effective, must at least partly escape the rumen undegraded. The capacity for postruminal digestion would probably also be sufficient to meet the energy needs of the growing ruminant. Severe constraints are imposed on diet composition if the method is used alone; the diets could not consist of carbohydrates and protein alone but would have to include substantial quantities of lipids. Apart from influencing fermentation losses (see previous papers) the composition of energy yielding nutrients abosrbed, expressed as proportions of glucose or glucose precursors, can influence host animal metabolism in two distinct ways. It can influence the obligatory heat losses associated with metabolism. It can affect the partition of energy into different types of animal products. Possibilities of using both the ruminal and postruminal capacity for digestion to achieve the optimum quantity and composition of absorbed nutrients for different types of production have been discussed. It is concluded that there is a pressing need for more information which will enable nutritionists to define more clearly the optimum composition of absorbed nutrients for different types of production in order to achieve the most efficient utilization of energy, and — possibly more important — to achieve the optimum proportions of desired products.