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Ruminal Availability of Crude Protein (CP) for Microbial Growth and Digestion

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Ruminants have the ability to derive nutrients and energy from fibrous feedstuffs because of the microorganisms that inhabit the digestive tract, particularly those in the rumen and reticulum, consisting of bacteria, protozoa, and fungi. These microbes have nutrient requirements in some ways similar to those of the host animal. Notable among these requirements is the need for nitrogenous compounds or CP that can be degraded by the microbes. If the availability of ruminally degraded CP is low, then microbial growth and(or) digestion is limited, which indirectly limits protein and(or) energy available to the host animal.

The requirement for ruminally available CP has not been extensively studied with goats compared with other ruminant species. For beef cattle, without considering ruminal recycling of nitrogen, the requirement of consumed ruminally degradable CP, or degraded intake protein (DIP), has been suggested as 13% of total digestible nutrient (TDN) intake (NRC, 2000). If recycling is also accounted for, the requirement is slightly lower (e.g., 10% of TDN). It has been suggested that ruminal nitrogen recycling is more extensive in goats compared with other ruminant species (Silanikove, 2000), suggesting that the DIP requirement might be lower. In this regard, Soto-Navarro et al. (2003) did not observe limitations in digestion or microbial growth with dietary DIP levels as low as 7% of TDN intake. However, to be conservative and as a safety factor, this calculator estimates the DIP requirement as 9% of TDN intake.

In order to estimate the DIP requirement, it is necessary to know feed intake and concentrations of TDN or metabolizable energy (ME) in the diet. To evaluate whether or not the DIP level in the diet is adequate to allow unhindered microbial growth and digestion, it is also necessary to estimate the concentration of DIP. This is determined from concentrations of CP in dry matter (DM) and DIP in CP. DIP concentrations are listed in the table given below for various feedstuffs.

Use this DIP calculator to estimate the daily requirement of DIP for all classes of goats. Enter the data into the table below and then click the Calculate DIP Requirement button. The results will be displayed in the table at the bottom of the page. The requirements are given in the first set of three boxes and intakes are in the second set. If values in the second set of boxes are less than in the first, then there is a deficiency of DIP that might limit microbial growth and(or) digestion. Hence, the formulation of the diet should be altered to correct this deficiency.

As an example, let's assume 1 kg of DM intake and a dietary ME concentration of 10 MJ/kg DM, which equates to a TDN concentration of 63.8%. This results in a DIP requirement of 57.4 g (1000 g DM intake x 0.638 x 0.09) or 5.74% of DM intake. With 10% CP in the diet, and a DIP concentration of 75% of CP, actual DIP intake is 75 g or 7.5% of DM intake (1,000 g DM intake x 10% CP in the diet x 0.75). Hence, the dietary level of DIP is adequate. However, if the dietary CP concentration is 8% of DM and the DIP level is 50%, then DIP intake is inadequate (40 g DIP intake and 4.0% of DM intake).

1. Enter feed intake (DM; kg)
2.
Enter dietary ME concentration (MJ/kg DM)
or
You can use the TDN calculator below and the ME concentration will be entered automatically.
3. Enter dietary CP concentration (% DM)
4. Enter dietary concentration of DIP (% CP)
To convert from English to metric system,
enter your values here.
They will be automatically entered into the table to the left.
DM intake
(lbs)

    

To estimate the dietary ME concentration, often feed tags list the TDN concentration. Likewise, most commercial feed laboratories estimate the TDN concentration based on various analyses, such as for crude protein and fiber fractions.

The ME concentration can be calculated with these simple formulas:
ME (MJ/kg) = TDN (%) × 0.15104 and
ME (Mcal/kg) = TDN (%) × 0.0361.

Enter TDN (%)
ME (MJ/kg)
ME (Mcal/kg)

DIP requirement (g):
DIP requirement (% DM):
DIP requirement (% CP):
DIP intake (g):
DIP intake (% DM):
DIP intake (% CP):

A number of measurements are necessary to most accurately determine the rumen undegraded protein concentration (UIP) in forages and supplemental concentrates. However, as noted for calculation of MP requirements, knowledge of the general type of feedstuff can allow a adequate estimate of the UIP concentration for most practical purposes. For example, many fresh forage diets would probably have a UIP concentration of 20% (on a total CP basis), which means that 80% of the CP is degraded in the rumen or is DIP. Dried forages would have a slightly higher UIP level (e.g., 30% for grasses). In general, as the dietary level of concentrate increases, the UIP level would increase and the DIP level decreases. Since not a large number of feedstuff UIP and DIP concentrations have been determined with goats, below is a table with DIP levels for cattle (Preston, 2000) that can be used until more values determined with goats become available. Typically, feed tags list the major ingredients, which then can be used along with the table below, to derive a reasonable estimate of the UIP concentration.

Show/hide feed table

Feedstuff Total CP, % DM DIP, % of total CPTDN, % DM
Alfalfa cubes 18 7057
Alfalfa, dehydrated,17% CP 19 4061
Alfalfa, fresh 18 8261
Alfalfa hay, early bloom 19 8459
Alfalfa hay, midbloom 17 8258
Alfalfa hay, full bloom 16 8054
Alfalfa hay, mature 13 7050
Alfalfa silage 18 8455
Alfalfa silage, wilted 22 7858
Alfalfa leaf meal 28 8569
Alfalfa stems 11 5647
Ammonium chloride 163 10057
Ammonium sulfate 132 1000
Bahiagrass hay 8 6351
Bakery product, dried 12 7090
Barley silage 12 8059
Barley silage, mature 12 7558
Barley straw 4 3043
Barley grain 12 7284
Barley grain, steam rolled 12 6084
Beet pulp, wet 9 6576
Beet pulp, dried 7 5675
Beet pulp, wet, with molasses 10 7577
Beet pulp, dried, with molasses 10 6676
Bermudagrass, Coastal, dehydrated 16 6062
Bermudagrass hay, Coastal 10 8056
Bermudagrass hay 10 8253
Bermudagrass silage 10 8550
Birdsfoot trefoil, fresh 21 8066
Birdsfoot trefoil hay 16 7857
Blood meal 92 2066
Bluegrass, Kentucky, fresh, early bloom 15 8069
Brewers grains, wet 28 4885
Brewers grains, dried 28 4284
Bromegrass, fresh, immature 15 7864
Bromegrass hay 10 7055
Bromegrass haylage 11 7457
Canarygrass hay 9 7453
Canola meal, solvent 40 7071
Citrus pulp, dried 7 6279
Clover, ladino, fresh 25 8069
Clover hay, ladino 21 7561
Clover, red, fresh 18 7964
Clover hay, red 15 7455
Clover hay, sweet 16 7053
Corn, whole plant, pelleted 9 5563
Corn fodder 9 5567
Corn stover, mature (stalks) 5 7059
Corn silage, milk stage 8 8265
Corn silage, mature, well eared 8 7472
Corn grain, whole 9 4287
Corn grain, rolled 9 4887
Corn grain, flaked 9 4393
Corn grain, high moisture 10 6293
Corn and cob meal 9 4882
Corn cobs 3 5048
Corn screenings 10 4891
Corn gluten feed 23 7581
Corn gluten meal, 41% CP 46 4085
Corn gluten meal, 60% CP 67 3889
Cottonoseed, whole 22 6295
Cottonseed, whole, delinted 23 6195
Cottonseed hulls 4 5545
Cottonseed meal, mechanical, 41% CP 45 4980
Cottonseed meal, solvent, 41% CP 48 6077
Diammonium phosphate 115 1000
Distillers grain, wet 28 4590
Distillers grain, barley 30 4477
Distillers grain, corn, dry 28 3890
Distillers grain, corn, wet 29 4590
Distillers grain, corn with solubles 29 4790
Distillers corn stillage 22 4592
Distillers grain, sorghum, dry 32 3885
Distillers grain, sorghum, wet 32 4585
Distillers grain, sorghum with solubles 31 4785
Distillers dried solubles 29 10088
Fat, animal, poultry, vegetable 00205
Feather meal, hydrolyzed 86 2569
Fescue, Kentucky 31, fresh 15 8064
Fescue hay, Kentucky 31, early bloom 18 7865
Fescue hay, Kentucky 31, mature 11 7052
Fish meal 66 4074
Grass hay 10 7058
Grass silage 11 7661
Hominy feed 11 5289
Lespedeza, fresh, early bloom 16 5060
Lespedeza hay 14 4054
Linseed meal, solvent 39 6276
Meadow hay 7 7750
Meat and bone meal, porcine/poultry 56 7672
Molasses, beet 9 10075
Molasses, cane 5 10075
Molasses, cane, dried 10 10074
Molasses, citrus 10 10077
Molasses, wood, hemicellulose 1 10076
Monoammonium phosphate 70 1000
Oat hay 10 7554
Oat silage 12 7960
Oat straw 4 6048
Oat grain 13 8176
Oat groats 18 8591
Oat middlings 17 8090
Oat hulls 4 7540
Orchardgrass, fresh, early bloom 14 7765
Orchardgrass hay 10 7359
Peas, cull 25 7886
Peanut meal, solvent 50 7277
Potatoes, cull 10 10080
Potato waste, wet 7 10082
Potato waste, dry 8 10085
Potato waste, wet with lime 5 10080
Potato waste, filter cake 5 10077
Poultry byproduct meal 62 5179
Poultry litter, dried 25 10064
Poultry manure, dried 28 7838
Prairie hay 7 6350
Rice grain 8 7079
Rice bran 14 7068
Rice hulls 3 5513
Rye grass hay 10 6058
Rye grass silage 14 7559
Rye grain 12 7982
Sanfoin hay 14 4061
Sorghum silage 9 7059
Sorghum grain (milo), ground 11 4382
Sorghum grain (milo), flaked 11 3891
Soybeans, whole 40 7293
Soybeans, whole, extruded 40 6593
Soybeans, whole, roasted 40 5293
Soybean hulls 12 7277
Soybean meal, solvent, 44% CP 49 6884
Soybean meal, solvent, 49% CP 54 6887
Spelt grain 13 7375
Sudangrass hay 9 7057
Sudangrass silage 10 7258
Sunflower seed, meal, solvent 38 7365
Sunflower seed, meal with hulls 31 6557
Sunflower seed hulls 4 3540
Timothy, fresh, pre-bloom 11 8064
Timothy hay, early bloom 11 7859
Timothy hay, full bloom 8 7057
Timothy silage 10 7559
Triticale grain 14 7585
Turnip roots 12 10086
Urea, 46% N 288 1000
Vetch hay 18 8658
Wheat, fresh, pasture 20 8471
Wheat hay 9 7557
Wheat silage 12 7959
Wheat straw 3 4042
Wheat straw, ammoniated 9 7550
Wheat grain 14 7788
Wheat grain, hard 14 7288
Wheat grain, soft 12 7788
Wheat grain, flaked 14 7189
Wheat grain, sprouted 12 8288
Wheat bran 17 7370
Wheat middlings 19 7882
Wheat mill run 17 7275
Wheat shorts 20 7580
Wheatgrass, crested, fresh, early bloom 11 7560
Wheatgrass, crested, fresh, full bloom 10 6655
Wheat grass, crested, hay 10 6654
Whey, dried 14 8582

Sources used in this calculation method are:

NRC. 2000. Nutrient Requirements of Beef Cattle, 2000 Update. National Academy Press, Washington, DC.

Preston, R. L. 2000. Typical composition of feeds for cattle and sheep. In: Beef 36(10), 10-20. Intertec Publ. Co. Overland Parks, KS.

Silanikove, N. 2000. The physiological basis of adaptation in goats to harsh environments. Small Ruminant Research 35:181-194.

Soto-Navarro, S. A., A. L. Goetsch, T. Sahlu, R. Puchala, and L. J. Dawson. 2003. Effects of ruminally degraded nitrogen source and level in a high concentrate diet on site of digestion in yearling Boer x Spanish wether goats. Small Ruminant Research. 50:117-128.