Roughage Value Index System Assessing Minimum ...

Assessing Minimum Amounts and Form of Roughages in Ruminant Diets: Roughage Value Index System E. M. Sudweeks, L. O. Ely, D. R. Mertens and L. R. Sisk J ANIM SCI 1981, 53:1406-1411.

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ASSESSING M I N I M U M A M O U N T S A N D FORM OF ROUGHAGES IN R U M I N A N T DIETS: R O U G H A G E V A L U E I N D E X SYSTEM ~ E. M. Sudweeks 2,4, L. O. Ely 2 , D. R. Mertens 3 and L. R. Sisk 2 University o f Georgia, College of Agriculture, Experiment Stations, Georgia Station, Experiment 2 30212 and College Station, Athens 3 30602

Summary Ruminants require adequate amounts of coarse-textured feeds to avoid metabolic disorders and, in the case of dairy cows, reduced milk fat production. Coarse-textured feeds help to maintain both proper muscle tone in the digestive system and proper rumen pH, both of which contribute to productivity and health. Texture of feeds is quantitatively reflected in the chewing activity of ruminants, and chewing stimulates saliva secretion. Saliva contains bicarbonates and other buffers that alter tureen environment and help avert disorders. Because chewing time reflects feed texture, a series of experiments were conducted in which feed intake, chewing time and milk and fat production were measured. Roughage value indexes (RVI) were partitioned for feed ingredients from regression equations. In addition, an equation was developed that predicts RVI from sieving and chemical data: RVI = 10.86 + PS (21.59) - DMI (1.91) + NDF (.541), where RVI is minutes/kilogram, PS is particle size in mean diameter, DMI is dry matter intake in kilograms and NDF is neutral detergent fiber percentage. The minimum RVI for the production of 3.5% fat milk was determined. By coupling an RVI requirement of 31 min/kg with feed RVI, one can formulate, by computer, diets for lactating cows that not only are nutritionally adequate, but also are adequate in

roughage value, and thus avert metabolic disorders. The RVI procedure is ready for field testing. (Key Words: Dairy Cows, Roughage Value Index, Forage, Chewing Time, Milk Fat, Roughage Requirements.)

Introduction

Ruminants have the capacity to utilize large quantities of roughages, but when roughage becomes limited in the diet because of the inclusion of grains or finely chopped forages, metabolic disorders often occur, even though the diet may be adequate in all known nutrients. Some of the disorders resulting from low roughage intake are the fat cows syndrome (Morrow, 1976; Clark and Davis, 1980; Fronk et al., 1980), abomasal ulcers (Bide and Dotward, 1975; Julien and Conrad, 1977), acidosis (Brent, 1976), rumen parakeratosis (Nocek and Kesler, 1980), displaced abomasums (Breukink and deRuyter, 1976), polioencephalomalacia (Brent, 1976), laminitis (Brent, 1976), ketosis (Fronk et al., 1980) and, in dairy cows, reduced milk fat percentage (Balch et al., 1955; Chalupa et al., 1970; Latham et al., 1974; Thomas, 1975; Murdock and Hodgson, 1979; Erdman et al., 1980). These disorders are due to both the texture of the diet and products of the digestive process. First, the lack of coarse material in the rumen reduces chewing activity (Balch et aL, 1955; Sudweeks et al., 1980). Reduced tureen motility diminishes muscle tone (Colvin et al., 1978; a Presented at the Symposium on "Potential ComNocek and Kesler, 1980; Nocek et al., 1980), plications Associated with Feeding Ruminants L o w Fiber Rations," held during the 72nd Annu. Meet. of contributing to abomasum displacement (Julien the ASAS, Cornell Univ., Ithaca, NY, July 27 to 30, and Conrad, 1977) and gastrointestinal epithe1980. lial degeneration (Nocek and Kesler, 1980). 2 Dept. of Anita. Sci., Experiment 30212. Second, diets containing large amounts of a Dept. of Anita. Sci., Athens 30602. 4present address: Professional Products, Inc., Sauk cereal grains with a preponderance of readily City, Wl 53583. fermentable carbohydrates tend to create a 1406 JOURNAL OF ANIMAL SCIENCE, Vol. 53, No. 5, 1981 Downloaded from jas.fass.org by guest on July 22, 2011

ROUGHAGEVALUEINDEXSYSTEM more acid condition in the rumen, resulting in off-feed and reduced efficiency, primary lesions of rumen and abomasal ulcers, parakeratosis, liver abscesses and many secondary ailments including laminitis, polioencaphalomalacia and possibly ketosis and milk fever. The acid condition also causes marked changes in rumen microbial population and in the acetate to propionate ratio, the latter being highly correlated with reduced milk fat percentage (Latham et al., 1974; Allison et al., 1975; Thomas, 1975). In dairy cows, disorders usually occur during early lactation, when nutrient demands are greatest. Some of the disorders can be eliminated by proper conditioning of the c o w - b y the feeding of coarse-textured forage as the main part of the diet during the dry period (Hutjens and Otterby, 1978). Also, attempts have been made to account for the "roughage effect" in the formulation of diets for milking cows. McCullough (1976) used estimated roughage factors to formulate optimum diets, and effective fiber values were assigned in place of some crude fiber values (Chandler et al., 1977). The NRC (1978) recommends a minimum of 17% crude fiber for lactating dairy cows, while J orgensen et al. (1978) recommends that specific amounts of long hay be fed, especially in early lactation. These recommendations have only a cursory relationship to the physical form of the forages, which limits their use in the computer formulation of diets. Balch (1971) observed that chewing time reflected the physical properties of the diet and

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used this relationship to propose a rumination ratio or roughage index for feeds. The roughage index is expressed as minutes of chewing (both eating and ruminating) per kilogram of dietary dry matter. Review and Discussion

Saliva Secretion. Chewing activity affects saliva flow. Poutiainen (1966) determined that daily saliva production of two Aryshire cows ranged from 40 to 175 liters when dry matter intake ranged from 3 to 12 kg daily. The diet consisted of 50% hay and 50% concentrates, but when 80% of the hay was ground and substituted for long hay and the total diet was fed at 9 kg, salivary secretion decreased 40 to 50%. Bailey (1961) also determined that saliva flow in four cows ranged from 98 liters/day, when the animals were fed 18 kg of alfalfa silage, to 190 liters/day when they were fed 5.4 kg of dry matter from dry grass. Bailey and Balch (1961) studied the secretion rate and composition of mixed saliva from five dry Shorthorn cows and found that the saliva contained 125 mmoles bicarbonate/liter. They also found that the concentration of bicarbonate remained nearly constant at the different saliva secretion rates. This illustrates the large effect that physical form of the the diet can have on saliva secretion and buffering capacity. The significance is even more striking when the total composition of saliva is considered (table 1). The buffering action of the saliva when coarse diets are fed thus alters rumen pH,

TABLE 1. MEANCOMPOSITIONOF MIXED AND PAROTIDSALIVASECRETED DURING PERIODS OF HIGH RATES OF SECRETIONIN COWSFED ADEQUATESODIUMCHLORIDEa Constituent

Mixed saliva a

Parotid saliva c

Na, constituent, meq/liter K, constituent, meq/liter

161 6.2 7.1 126 26 167 159 1.02 .89

157 7.0 7.4 127 23 164 157 1.05 .91

Cl, constituent, meq/liter Bicarbonate, constituent, meq/liter Phosphate, constituent~ meq/liter Sum of cations, constituent, meq/liter Sum of anions, constituent, meq/liter Dry matter, constituent, %

Ash, constituent, % aBailey and Balch (1961a). bMeans for 48 samples from four cows fed diets of hay.

CMeans for 52 samples from one steer when secretion rate exceeded 12 ml/min. Downloaded from jas.fass.org by guest on July 22, 2011

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SUDWEEKS ET AL,

TABLE 2. ROUGHAGE VALUE INDEXES FOR CATTLE a Chewing time/ kg DM, rain

Item Hay and straws Alfalfa hay Chopped Dehydrated meal Long Pelleted

44.3 36.9 61.5 36.9

Bermudagrass hay Grass Dried Dried and pelleted Hay, mixed Finely ground and pelleted Good quality Medium quality Second cut

78.5 -+ 5.43 44.53 15.18 13.19 87.105 103.109 77.0

Oat straw Oat straw Finely ground and pelleted Orchardgrass Early cut #1 Late cut

160,0 18.0 74.0 90.0

By products Citrus pulp Corn cobs, pelleted Cottonseed hulls Hominy feed Rice hulls ground (max of 13% of DM) Soyhen hulls Sugarcane bagasse pelleted (max of 30% of DM)

30.9 +- 15.4 15.0 30.1 8.1 16.0 8.4 18.0

Silages Alfalfa silage Fine cut Medium cut Corn silage Coarse cut Fine cut Medium cut Grass silage Sorghum silage Wheat silage

66.1 40.0 59.6 99 to 120 67.3 -+ 1.7 68.9 +- 3.2

Grain and other concentrates Barley, ground Concentrates, pelleted Corn, ground (all grain mixes) Milo, ground Oats, ground Oil meals Wheat, ground

15.0 12.0 5.1 +-4.13 11.O 12.0 6.0 I0.0

22.3 26.0

Miscellaneous feeds ingredients Minerals Molasses Urea

.0 .0 .0

asudweeks and Ely (1979).

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ROUGHAGE VALUE INDEX SYSTEM favoring the synthsis of acetate over propionate, which, in turn, increases the fat percentage of the milk (Latham et al., 1974). However, saliva buffering must be coupled with chewing and other unidentified physiological activities to eliminate depressed milk fat percentage. The addition of plastic ribbon to the diet of cows producing low fat milk increased chewing activity, and presumably saliva production, but failed to increase milk fat percentage (Welch and Smith, 1971). Moreover, the addition of buffers to the diet will not totally correct milk fat depression. Roughage Value Index System. O n the basis of the observation that chewing time quantitatively reflects the physical characteristics of the ruminant diet (Balch, 1971), we fed mature dairy steers a series of diets at constant intake, varying the proportion of roughage and grain over three feeding periods. Chewing time was recorded with equipment developed at Georgia (Law and Sudweeks, 1975), and regression equations were developed by Sudweeks et al. (1975), that partition chewing time for each forage and grain into their respective roughage value indexes (RVI). Table 2 summarizes RVI from subsequent experiments and from the literature. D.etermining Roughage Value Indexes From Laboratory Data. To make the RVI system practical, we developed a method of generating RVI from laboratory data. First, representative samples of 28 diets of various physical textures were screened to equilibrium through a set of sieves with mesh openings ranging from .149 to 20 millimeters. Weight distribution on each screen was recorded, and the percentage weight

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was accumulated from the smallest sieve to the largest (table 3). Second, the mean diameter by weight distribution (sieve size at which 50% of weight occurs) were calculated by methods of the ADSA (1970), with the mean particle size of long hay remaining on the top sieve taken as 4.75 mm mean diameter. However, forage particles were not of a logarithmic normal distribution, and this method was not intended to be used for forages9 An imporved sieving method needs to be developed (Waldo et al9 1971 ), possibly through the use of the Oscilating Screen Particle Separator (Finner et al9 1977; Santini et al., 1980). Nevertheless, the following regression equation gave an acceptable fit in predicting RVI (R 2 = .78): RVI = 10.86 + PS (21.59) - DMI (1.91) + NDF (.541), where RVI is minutes/kilogram, PS is particle size as mean diameter in millimeters, DMI is dry matter intake in kilograms and NDF is neutral detergent fiber percentage. For this system to be useful, samples must be. sieved in a quantity great enough that long forages can be processed before the leaves are disturbed and the stems broken, making core sampling impractical. However, it might be possible to alleviate this sampling difficulty by assigning all long hays a mean diameter of 4.75 mm and letting chemical data alter the final RVI. Intake Affect. The RVI reported in table 2 were determined at or near maintenance intake for the most part; it was shown that as intake increased, RVI decreased (Sudweeks et al., 1979a,b). Therefore, an adjustment equation was developed by regressing RVI on kilograms intake9 The equation was: RVI = (130 + 47.22

TABLE 3. PARTICLE SIZE DISTRIBUTION OF THREE COMPLETE DIETS FOR DAIRY COWS

Sieve size, mm

Log, um

Long

20.000 8.000 4.000 2.000 .888 .417 .149 Pan Mean diameter, mm

4.3010 39 3.6020 3.3010 2.9206 2.6201 2.1732

99.44 65.55 59.21 28.76 13.51 3.58 1.09 .56 (3.495)

Hay type Chopped Accumulated % on each sieve

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... 99.12 80.49 33.23 11.27 2.05 19 .88 (3.286)

Pelleted

6:96

67.57 62.23 31.59 16.68 3.04 (2.832)

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SUDWEEKSET AL.

TABLE 4. THEE DIETS CALCULATED AS OPTIMAL FOR 600-KG DAIRY COWS PRODUCING 27 KG OF MILK/DAYa Diet

Ingredients

Low cost silage

Bermudagrass hay Corn silage Citrus pulp Cottonseed hulls Soybean hulls Corn Cottonseed meal Molasses Trace mineralized salt Urea Deflourinated rock phosphate Limestone Cost/kg, r Roughage value (RVI)

5618 . . ... . _. 9.6 21.3 10.0 .5 .5 .6 .7 9.0 41.0

asilage costs: low 6.6r

dry matter; high 19.8r

x)/x, where x is intake in kilograms (Sudweeks et al., 1980). This equation allowed RVI measured at any intake to be adjusted to maintenance intake level, because the roughage requirement was calculated from maintenance values. Roughage Requirement. To establish the minimum roughage requirement for the maintenance of normal milk fat production, three experiments were conducted in which lactating cows were fed diets with various RVI, and chewing rate, milk production and milk composition were monitored (Sudweeks et al., 1979 a,b). Separate regression equations were developed by regressing milk fat percentage and daily fat production on minutes of chewing time per kilogram of dietary dry matter (RVI). The equation for fat percentage was, % fat = 2.46 + .039 x - .00018x 2, where x = RVI, but this equation lacked fit (R 2 = .38), and it will require verification through field testing. The required RVI for milk of 3.5% fat was 31.1, while the RVI for maximum fat production per day was 49.3. Diet Formulation. Toillsutrate the utility of the RVI system, we formulated diets with and without RVI values and requirements, using the Optimum Ration Computer Program (McCullough, 1976); compositions are shown in table 4. The first diet consisted primarily of corn silage, and because this silage had adequate

.

. .

.

High cost silage

High cost silage with RVI

... 10.0

17.1 17.9 40.0 .9 2 .4 22.8 .4 .5 .5 .6 ... 13.7 31.1

. .

20.0 . 42.1 20.5 4.8 .5 .5 .2 1.4 12.0 17.5

.

dry matter. Roughage requirement is 31.1 min/kg.

RVI, both nutrient and roughage requirements were met, even though the computer program had no roughage requirement for this diet. In practice, this diet might not be adequate in roughage value over an extended period of time. This question needs to be answered in field tests. The second diet resulted from the selection of mostly cottonseed hulls because the price of corn silage was artificially increased. The diet was also formulated without a roughage requirement, and although it satisfied nutrient requirements, it did not meet the roughage requirements. This would probably cause depressed milk fat percentage initially and possibly some metabolic disorders if the diet were fed for an extended period. Diet 3 was formulated from the RVI requirement for 3.5% fat milk. The diet met all nutrient requirements and satisfied the roughage requirement with the proper balance of corn silage, citrus pulp and a specific amount of hay. This diet would meet all known nutrient needs and also would be adequate in roughage, which would prevent depressed fat percentage and digestive disorders. Literature Cited

ADSA. I970. A report: Committee on classification of particle size in feedstuffs. J. Dairy Sci. 53:689. Allison, M. J., I. M. Robinson, R. W. Dougherty and J. A. Bucklin. 1975. Grain overload in cattle and sheep: Changes in microbial populations in the

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ROUGHAGE VALUE INDEX SYSTEM cecum and rumen. Amer. J. Vet. Res. 36:181. Bailey, C. B. 1961. Saliva secretion and its relation to feeding in cattle. 3. The rate of secretion of mixed saliva in the cow during eating, with an estimate of the magnitude of the total daily secretion of mixed saliva. Brit. J. Nutr. 15:443. Bailey, C. B. and C. C. Balch. 1961. Saliva secretion and its relation to feeding in cattle 1. The composition and rate of secretion of paratid saliva in a small steer. Brit. J. Nutr. 15:371. Balch, C. C. 1971. Proposal to use time spent chewing as an index to the extent to which diets for ruminants possess the physical property of fiberoushess characteristic of roughages. Brit. J. Nutr. 36:383. Balch, C. C., D. A. Balch, S. Bartlett, M. P. Bartrum, V. W. Johnson, S. J. Rowland and J. Turner. 1955. Studies on the secretion of milk of low fat content by cows on diets low in hay and high in concentrates. VI. The effects on the physical and biochemical processes of the reticulo-rumen. J . Dairy Sci. 22:270. Bide, R. W. and W. J. Dorward. 1975. Clinical chemistry of grain-fed cattle. II. Liver functions. Can. J. Anim. Sci. 55:23. Brent, B. E. 1976. Relationship of acidosis to other feedlot ailments. J. Anita. Sci. 43:930. Breukink, H. J. and T. deRuyter. 1976. Abomasal displacement in cattle: Influence of concentrates in the ration of fatty acid concentrations in ruminal abomasal and duodenal contents. Amer. J. Vet. Res. 37:1181. Chalupa, W., G. D. O'Dell, A. J. Katches and R. Lavaker. 1970. Supplemental corn silage or baled hay for correction of milk fat depressions produced by feeding pellets as the sole forage. J. Dairy Sci, 52:208. Chandler, P. T., A. H. Rakes and T. H. White, Jr., 1977. User's manual for dairy cattle feeding formulation. Pub. 760, Extension Division System, Virginia Polytechnic Inst. and State Univ., Blacksburg. Clark, J. H. and C. L. Davis. 1980. Some aspects of feeding high producing dairy cows. J. Dairy Sci. 63:873. Colvin, H. W. Jr., R. D. Digesti and J. A. Louvier. 1978. Effect of succulent and nonsucculent diets on tureen motility and pressure before, during and after eating. J. Dairy Sci. 61:1414. Erdman, R. A., R. L. Botts, R. W. Hemken and L. S. Bull, 1980. Effect of dietary bicarbonate and magnesium oxide on production and physiology in early laction. J. Dairy Sci. 63:923. Finncr, M. J., J. E. Harzinski and L. L. Page. 1977. Measuring particle length of chopped forages. Internat'l Grain and Forage Harvesting Conf., Iowa State Univ., Ames, Sept. 25 to 29, 1977. Fronk, T. J., L. H. Schultz and A. R. Hardie. 1980. Effect of dry period over-conditioning on subsequent metabolic disorders and performance of dairy cows. J. Dairy Sci. 63:1080. Hutjens, M. J. and D. E. Otterby. 1978. Transitional nutritional management-The dry and fresh cow. Proc. 39th Minnesota Nutr. Conf., p. 55. Jorgensen, N. A., M. J. Finner and J. P. Marquardt. 1978. Effect of forage particle size on animal performance. ASAE Summer Meet. 5, Paper 78-1048.

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Julien, w. E. and H. R. Conrad. 1977. Influence of dietary protein on susceptibility to alert downer syndrome. J. Dairy Sci. 60:210. Latham, M. J., J. D. Sutton and M. E. Sharpe. 1974. Fermentation and microorganisms in rumen and content of fat in the milk of cows given low roughage rations. J. DairySci. 57:803. Law, S. E. and E. M. Sudweeks. 1975. Electronic transducer for ruminant research. J. Anita. Sci. 41:213. McCullough, M. E. 1976. Optimum Feeding of Dairy Animals. The University of Georgia Press, Athens. Morrow, David A. 1976. Fat cow syndrome. J, Dairy Sci. 59:1625. Murdock, F. R. and A. S. Hodgson. 1979. Effects of roughage type and texture on milk fat by lactating dairy cows. J. Dairy Sci. 62:505. Nocek, J. E., K. A. Cummins, C. E. Polan and J. H. Herbein. 1980. Influence of ration physical form and nitrogen availability on growth, ruminal fermentation, rumen morphology and in vitro acetate and propionate transport rates. J. Dairy Sci. 63 (Suppl.):131. Nocek, J. E. and E. M. Kesler. 1980. Growth and rumen characteristics of holstein steers fed pelleted or conventional diets. J. Dairy Sci. 63 : 249. NRC, 1978. Nutrient Requirements of Domestic Animals, No. 3. Nutrient Requirements of Dairy Cattle. National Academy of Sciences-National Research Council, Washington, DC. Poutiainen, Esko. 1966. The proportion of saliva in the fluid flowing through the reticulo-rumen of the cow. Ann. Agr. Fenniae 5:342. Santini, F. J., N. A. Jorgensen, A. R. Hardie and M. F. Finner. 1980. Effect of forage particle size on total chewing time in lactating dairy cows. J. Dairy Sci. 63 (Suppl.):133. Sudweeks, E. M., M. J. Anderson, R. C. Lamb, S. E. Law, L. O. Ely, M. E. McCullough and L. R. Sisk. 1979a. Development and application of a roughage value index for formulating dairy rations. Georgia Exp. Sta. Res. Bull. 238. Sudweeks, E. M. and L. O. Ely. 1979. Evaluating the physical form of the diet in ruminant nutrition. Proc. Dist. Feed Res. Council 34:60. Sudweeks, E. M., L. O. Ely, J. R. Loften and D. R. Mertens. 1979b. Effects of hay type, hay form and fiber level on production and chewing time of lactating dairy cows. J. Anim. Sci. (Suppl. 1) 49:411. Sudweeks, E. M., L. O. Ely and L. R. Sisk. 1980. Effect of intake on chewing activity of steers. J. Dairy Sci. 63:152. Sudweeks, E. M., M. E. McCullough, L. R. Sisk and S. E. Law. 1975. Effects of concentrate type and level and forage type on chewing activity of steers. J. Anita. Sci. 41:219. Thomas, P. C. 1975. Diet and milk secretion in the ruminant. World Rev. Anita. Prod. 11 (4):33. Waldo, R. W., L. W. Smith, E. L. Cox, B. T. Weinland and H. L. Lucas, Jr. 1971. Logarithmic normal distribution for description of sieved forage materials. J. Dairy Sci. 54:1465. Welch, J. G. and A. M. Smith. 1971. Physical stimulation of rumination activity. J. Anim. Sci. 33: 1118.

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