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Dry matter intake, rumen fermentation and microbial nitrogen supply in Pelibuey sheep fed low-quality rations and different levels of corn oil.


Eight Pelibuey hair sheep (45 [+ or -] 2.2kg body weight), cannulated in the rumen and kept in metabolic stalls in a roofed building, were used to determine the effect of the incorporation of com oil in a concentrate upon dry matter (DM) intake, rumen fermentation of DM, organic matter (OM) crude protein (CP) and neutral detergent fiber (NDF), as well as microbial N supply to the small intestine, Sheep were fed low-quality Guinea hay (Panicum maximum) grass ad libitum and 300g daily of a commercial concentrate to which 0, 4, 8 and 12% of com oil was added. Voluntary DM intake was measured and rumen fermentation of DM, OM, CP and NDF neutral detergent fiber were estimated with the nylon bag technique, after hay incubation in the rumen for 6, 12, 24, 48, 72 and 96h. Urinary excretion of purine derivatives was determined. As oil concentration was increased, DM intake of hay decreased (P<0.05). Rumen fermentation (a, b and a+b fractions) of DM, OM, CP and NDF showed no significant differences (P>0.05) between treatments, but rates of digestion (fraction c) were higher for DM, OM and CP when oil was not included in the supplement (4.9, 14.5 and 10.4%/h, respectively). Digestion rate of NDF was higher (5.71%/h; P<0.05) with 8% com oil. Microbial N supply to the small intestine showed no significant differences (P>0.05) between treatments; however, addition of 8% oil decreased (5.11 [+ or -] 0.29 gd) microbial N supply with respect to 4% (6.18 [+ or -] 0.29), and N supply was lower when the oil was not added (4.73 [+ or -] 0.27) than when it was added at 4, 8 and 12% (6.18 [+ or -] 0.29, 5.11 [+ or -] 0.29 and 5.19 [+ or -] 0.29, respectively). Corn oil in the concentrate fed to sheep tended to decrease DM intake of low-quality tropical hay without effects on rumen degradability and microbial N supply to the small intestine.

KEYWORDS / Corn Oil / Rumen Fermentation / Pelibuey Hair Sheep / Microbial Nitrogen / Low-quality Grass /


Ocho ovinos de pelo de la raza Pelibuey (45 [+ or -] 2,2kg peso vivo) fueron fistulados y colocados en jaulas metabolicas para de evaluar el efecto de la incorporacion de aceite de maiz en el concentrado sobre el consumo de materia seca (MS), fermentacion ruminal de MS, materia organica (MO), proteina cruda (PC) y fibra detergente neutra (FDN), asi como el aporte de N microbial al duodeno. Los borregos fueron alimentados con una dieta base de heno de pasto Guinea (Panicum maximum) de baja calidad, a libre acceso, y 300g de un concentrado adicionado de 0, 4, 8 o 12% de aceite de maiz. El consumo voluntario de MS fue registrado y la fermentacion ruminal de la MS, MO, PC y FDN del heno fueron estimados mediante tecnica de bolsa de nylon, despues de incubacion en el rumen por 6, 12, 24, 48, 72 y 96h. La excrecion de purinas fue determinada. El consumo voluntario de MS del heno disminuyo (P<0,05), a medida que la concentracion de aceite se incremento (665,8 [+ or -] 35,1, 648,8 [+ or -] 35,1, 558,8 [+ or -] 36,3 y 525,3 [+ or -] 36,3 g/dia para 0, 4, 8 y 12% de aceite, respectivamente). La fermentacion ruminal (fracciones a, b y a+b) de la MS, MO, PC y FDN no mostraron diferencias significativas (P>0,05) entre tratamientos, pero la tasa de digestion (fraccion c), fue mayor en la MS, MO y PC cuando no se incluyo el aceite en el concentrado (4,9; 14,5; y 10,4%/h, respectivamente). La tasa de digestion de FND fue mayor (5,71%/h; P<0,05) cuando se incluyo aceite al 8%. El aporte de N microbial al duodeno no mostro diferencias significativas entre tratamientos; sin embargo, la adicion de 8% de aceite disminuyo el aporte de N (5,11 [+ or -] 0,29g/d), respecto a la de 4% (6,18 [+ or -] 0,29) y el aporte de N fue menor cuando no se anadio aceite (4,73 [+ or -] 0,27), que cuando fue adicionado en 4, 8 y 12% (6,18 [+ or -] 0,29; 5,11 [+ or -] 0,29 y 5,19 [+ or -] 0,29; respectivamente). El aceite de maiz en el concentrado dado a los ovinos tiende a disminuir el consumo de MS de heno, pero no mostro efecto sobre la degradacion ruminal ni en el aporte de N microbial al duodeno.


Oito ovinos de pelo da raca Pelibuey (45 [+ or -] 2,2kg peso vivo), foram fistulados e colocados em jaulas metabolicas para avaliar o efeito da incorporacao de azeite de milho no concentrado sobre o consumo de materia seca (MS), fermentacao ruminal da MS, materia organica (MO), proteina crua (PC) e fibra detergente neutra (FDN), assim como o acrescimo de N microbial ao duodeno. Os borregos foram alimentados com uma dieta base de feno de mata-pasto Guine (Panicum maximum) de baixa qualidade, de livre acesso, e 300g de um concentrado no qual se adicionou 0, 4, 8 ou 12% de azeite. O consumo voluntario de MS foi registrado e a fermentacao ruminal da MS, MO, PC e FDN do feno foram estimados mediante tecnica de bolsa de nylon, depois da incubacao no rumem por 6, 12, 24, 48, 72 e 96h. A excrecao de purinas foi determinada. O consumo voluntario de MS do feno diminuiu (P<0,05) a medida que a concentracao de azeite se incrementou (665,8 [+ or -] 35,1; 648,8 [+ or -] 35,1; 558,8 [+ or -] 36,3; e 525,3 [+ or -] 36,3g/dia para 0%, 4%, 8% e 12% de azeite, respectivamente). A fermentacao ruminal (fracoes a, b e a+b) da MS, MO, PC e FDN, nao mostraram diferencas significativas (P>0,05) entre tratamentos, mas a taxa de digestao (fracao c), foi maior na MS, MO e PC quando nao se incluiu o azeite no concentrado (4,9; 14,5 e 10,4%/h, respectivamente). A taxa de digestao de FND foi maior (5,71%/ h; P<0,05) quando o azeite se incluiu ao 8%. O acrescimo de N microbial no duodeno nao mostrou diferencas significativas entre tratamentos; no entanto, a adicao de 8% de azeite diminuiu o acrescimo de N(5,11 [+ or -] 0,29g/d), em relacao a 4% (6,18 [+ or -] 0,29) e o acrescimo de N foi menor quando o azeite nao esteve presente (4,73 [+ or -] 0,27) que quando foi adicionado em 4, 8 e 12% (6,18 [+ or -] 0,29, 5,11 [+ or -] 0,29 e 5,19 [+ or -] 0,29; respectivamente). O azeite de milho no concentrado dos ovinos tende a diminuir o consumo de MS de feno, mas nao mostrou efeito sobre a degradacao ruminal nem no acrescimo de N microbial no duodeno.


Animal and vegetable fat and oil represent important energy sources in rations for domestic animals. They also contain essential nutrients, such as fatty acids, of which linoleic acid may be the most important for better reproductive efficiency. Recent evidence indicates that fat supplementation may be employed to modulate some physiological processes in the ovarium of the cow, regardless of energy intake (Thomas, 1994).

Palmquist (1991) suggested that fat supplementation in ruminant rations should not exceed 5% of the dry matter (DM) since rumen microbial fermentation of some dietary components (i.e., crude fiber, crude protein) may be negatively affected. Fat is frequently added in ruminant rations to increase energy density, but unsaturated fatty acids inhibit rumen microbial activity and can decrease fiber fermentation (Jenkins, 1993). However, fat in oilseeds is more ruminally inert when fed whole than when given as crushed seeds or free oil, apparently because of the slower release of fat from the whole seed. Nonetheless, Glenn et al. (1977) indicated that fat supplementation may be an efficient method to reduce protein fermentation in the rumen. In some studies, the efficiency of microbial protein synthesis in the rumen was not affected by supplementary fat (Elliot et al., 1997). The present work was aimed at determining the effect of the level of incorporation of corn oil in the concentrate on DM intake, rumen fermentation and microbial nitrogen supply to small intestine of Pelibuey hair sheep fed low-quality Guinea grass (Panicum maximum) hay.

Materials and Methods Location and climate

The present work was carried out at the Faculty of Veterinary Medicine and Animal Science, University of Yucatan, Merida, Mexico, from June to August 1999. The local climate is hot-humid, or AW0 following the classification of Koppen as modified by Garcia (1987). The area has a mean annual rainfall of 953mm, mean annual temperature of 26.5[degrees]C and relative humidity of 66% during April and 85% during September (Duch, 1988).

Animals and feeding

Eight Pelibuey hair sheep with a mean live weight of 45 [+ or -] 2.2kg and cannulated in the dorsal sac of the rumen with flexible plastic cannulas of 7.5cm internal diameter (Bar Diamond Inc. Parma, Idaho, USA) were used in the experiment. Sheep were maintained in metabolic stalls throughout the experiment in a roofed building. Sheep were allowed ad libitum access to Guinea grass (Panicum maximum) hay and 300g/ day of a commercial concentrate with 16% of crude protein (CP). Corn oil was added at the levels of 0, 4, 8 and 12% of the amount of concentrate given. Fresh water was freely available at all times.

Experimental procedure

Sheep were randomly allocated (2 per treatment) and fed once daily (08:00h). The DM intake was determined as the difference between the amount offered and that refused the following morning. Experimental periods lasted 14 days, 7 days for adaptation and 7 days for measurements. Guinea grass hay was chopped in a hammer mill (2.54cm sieve) before feeding. During the first 7 days, DM intake was measured and from day 8 to 14, urinary purine derivative excretion was measured, During the last 4 days of the experiment, in situ rumen fermentation of Guinea grass was performed.

Chemical analysis

The chemical composition (DM, OM and CP) of Guinea grass was determined following AOAC (1980) procedures, and NDF by the detergent method of Van Soest et al. (1991).

Rumen degradation

The nylon bag technique (Orskov et al., 1980) was employed to estimate rumen degradation of dry matter (DM), organic matter (OM), crude protein (CP) and neutral detergent fiber (NDF) of Guinea grass. Nylon bags (7x5cm and 50mm; Bar Diamond Inc. Parma, Idaho, USA) were incubated in the rumen for 6, 12, 24, 48, 72 and 96h. Each bag contained 6g DM of grass. Bags were kept in the ventral sac of the rumen. All bags were inserted at the same time and were withdrawn sequentially from the rumen. After being withdrawn from the rumen the bags were frozen until analysis were performed. After thawing, bags were mechanically washed with tap water, left to drain excess water and introduced into forced-air and oven at 60[degrees]C for 48h. After 24h pellets formed during the drying process were destroyed manually and bags reintroduced into the oven to complete the 48h drying period. After drying was completed, bags were weighed in an analytical balance. Rumen degradation of DM, OM, CP and NDF was estimated as the difference between the material incubated in the rumen and the residue left after incubation. Rumen degradation data was fitted to the nonlinear model

p = a + b ([1-exp.sup.-ct])

as described by Orskov and McDonald (1979) to estimate degradation constants, where p: percent degradation at time t, a: intercept representing the immediately soluble fraction, b: insoluble but potentially degradable fraction, c: rate of degradation of b, and t: time of incubation in the rumen.

Purine derivative excretion

Urinary excretion of purine derivatives was estimated as described by Chen et al. (1990a). Urine was collected quantitatively for seven days and conserved in 100ml of 10% [H.sub.2]S[O.sub.4] to keep pH between 2 and 3. The urine was filtered through 5 layers of cheesecloth and then diluted with tap water (5:1). A diluted urinary sample of 200ml was stored in a freezer until analysis. Urinary allantoin was assayed by the method described by Young and Conway (1942) and uric acid according to Chen et al. (1990b). Microbial nitrogen supply to the small intestine was estimated with the models proposed by Chen et al. (1990a) using the Newton-Rapshon procedure of STATGRAPHICS (1996). The amount of microbial purines absorbed (X; mmol/day) corresponding to the purine derivatives excreted (Y; mmol/day) was calculated as

Y = 0.84 X + (0.15 [BW.sup.0.75] [e.sup. 0.25X])

where X: amount of microbial purines absorbed (mmol/day), 0.15: factor which corrects for the contribution of endogenous purines, Y: purine derivatives excreted (mmol/day), and [BW.sup.075]: metabolic body weight

The amount of microbial nitrogen supplied to the animal was calculated as follows (Chen et al., 1992):

Microbial nitrogen (g/d) = =70X / (0.83 x 0.116 x 1,000) =0.727 X where 0.83: digestibility coefficient for microbial purines, 70: nitrogen content of purines (mg/mmol), 0.116: proportion of nitrogen in purines relative to total nitrogen in microbial mass.

Statistical Analysis

The results obtained for DM intake, rumen degradability of DM, CP, OM and NDF, and microbial N supply to the small intestine were processed in a spreadsheet (Microsoft, 1997) and analyzed as a Latin-rectangle design experiment using the General Linear Models Procedure (GLM) of SAS (1988). The differences between means of treatments were tested using the Tukey test.


The DM intake of Guinea grass hay decreased as the level of incorporation of corn oil in the ration was increased (Table I). However, statistical differences were only observed between treatments with 0 and 12% of corn oil in the ration. (665.8 [+ or -] 35.1 vs. 525.35 [+ or -] 36.3g of DM/day, respectively). There were no differences (P>0.05) regarding kinetics of rumen degradation of DM, OM, CP and NDF between treatments (Table I). It was evident that rate of digestion was numerically higher when corn oil was not included in the supplement (4.9, 14.5, and 10.4%/h for DM, OM and CP). The rate of digestion of NDF was higher (5.7%/ h; P<0.05) when 8% oil was incorporated in the concentrate. Microbial nitrogen supply to the small intestine showed no significant differences (P>0.05) between treatments; however, it was observed that addition of corn oil at 8% of concentrate DM, numerically decreased microbial nitrogen supply to the lower tract.


The reduction observed in dry matter intake from basal rations by sheep as a result of oil incorporation in the diet has been reported by several authors. Keady and Mayne (1999) fed cows with silage and increasing levels of fish oil, and observed a trend towards a decreased silage and total DM intake. Other studies (Choi et al., 2000) observed a similar effect and showed that the increased fat concentration in the ration (0, 30, 60, 90g/ kg) resulted in a linear decrease in dry matter intake. The reduction in DM intake recorded in the present study as corn oil was added may be due to metabolic control mechanisms related to the effect of some fatty acids on biohydrogenation in the rumen, as suggested by Doreau and Chilliard (1997), which may interfere with rumen function. Other studies report that dietary fat inhibits abomasal motility (Nicholson and Omer, 1983), which may limit food intake by distention of the reticulum (Grovum, 1979). Fat also stimulates the release of cholescystokinin (CCK; Choi and Palmquist, 1996), which may influence feed intake centrally. Choi and Palmquist (1996) reported that cows fed high fat diets had lower DM intake and higher plasma CCK and pancreatic polypeptide concentrations when compared with the control cows; they postulated that the elevated plasma CCK may have mediated the influence of fat on DM intake.

The incorporation of corn oil in the ration did not affect rumen fermentation of DM and NDF. Similar results were reported by Keady and Mayne (1999). Oldick and Firkins (2000) showed that the addition of fat (4.85% partially hydrogenated tallow, tallow or animal-vegetable fat) did not affect intake or apparent digestibility of OM. In contrast, Whitney et al. (2000), observed that in vitro digestibility of DM decreased when 6% soybean oil was incorporated in forage-based diets with respect to the control group (61.1 vs 68.8%). Nevertheless, in previous studies with lactating cows (Pantoja et al., 1994), hydrogenated fat sources and tallow were fed at concentrations up to 5% of dietary DM without any adverse effect on rumen NDF fermentability. Similar results were reported by Aldrich et al. (1995) when steers were fed a diet containing 3.4% soybean oil in 12 meals per day.

Earlier work (Kowalczyk et al., 1977; Jenkins, 1993) suggested that when lipids are added in the ration at levels above 10%, rumen fermentation of structural carbohydrates may be reduced by 50%. This reduction occurs along with a reduction in C[H.sub.4], [H.sub.2], and volatile fatty acid production in the rumen. Protein metabolism in the rumen may also be altered as fat interferes with rumen fermentation. Lkwuegbu and Sutton (1982) observed a reduction in rumen protein fermentation when linseed oil (13, 26 or 40ml/d) was infused into the rumen of sheep. In the present work, the lack of effect of corn oil incorporation on kinetics of rumen fermentation may be attributed to the fact that the level of addition did not delay the rate of growth of bacteria and protozoa in the rumen.

Tesfa (1995) showed that a daily supplement of 0.5kg of rapeseed crude oil to a basal diet did not affect rumen pH bur decreased protozoa mass and depressed rumen carboxymethylcellulase and xylanase activities, which may explain partially the reduction observed in NDF degradability. When degradability of rapeseed oil-treated (basal diet plus 0.5 kg of rapeseed oil) was measured in saccco, degradability of DM of grass silage and NDF was lowered in cows fed with either rapeseed oil, crude rapeseed oil or treated rapeseed oil of grass silage prior to rumen incubation. However, treated rapeseed oil of grass silage was not as effective in fiber digestion as dietary crude rapeseed oil.

In another experiment, Palmquist (1991) worked with rumen fistulated cows fed diets with or without 500g/day of an animal-vegetable blend, calcium soaps of tallow fatty acids, or whole oilseeds (cotton, sunflower, soybean). There were no diet effects on digestibility; orchargrass acid detergent fiber digestibility was 26.3, 40.0, and 47.3% (SEM = 0.631) at 12, 24 and 48h post-incubation, respectively.

Rossi et al. (1999) used rumen fistulated dairy cows to determine the effect of fat or soybean meal on rumen degradation of crude protein. The addition of 10% or 25% fat resulted in lower DM degradation after 8 and 24h of incubation. Protein degradation was reduced by addition of 10% fat at 8 and 24h, while 25% fat addition considerably lowered crude protein disappearance after only 8h of incubation in the rumen.

In the present study, the level of oil supplementation did not affect the availability of microbial N at the small intestine of Pelibuey hair sheep. These results are comparable to those reported by Elliot el al. (1997) in steers supplemented with different types of fats. Fat supplementation has been reported to increase rumen microbial efficiency (Zinn, 1989; Klusmeyer et al., 1991; Pantoja et al., 1994), but this is believed to occur only when the source of fat decreases the number of protozoa and, subsequently, decreases recycling of ruminal bacteria (Jenkins, 1993). Other studies showed that feeding high amounts of free oils (unsaturated fats) to ruminants often caused defaunation and a marked increase in microbial protein supply to the lower tract (Dewhurst et al., 2000). Brodiscou et al. (1994) suggested that the increase in microbial protein supply to the small intestine in response to addition of vegetable oil is partly explained by defaunation. However, Murphy et al. (1987) fed full-fat rapeseed oil meal to dairy cows and noted an increase in microbial protein supply to the small intestine, though it was not clear whether defaunation was involved.

Kowalski (1998) examined the effect of calcium soaps of rapeseed fatty acids (CSRFA) on rumen fermentation, nutrient and fatty acid (FA) flow to the duodenum. The treatments were a control with no fat, CSRFA at 2% DM, and soybean meal protein coated with CSRFA (1:1 w/w) at 4% of dietary DM. The treatments did no affect total N flow into the duodenum or efficiency of microbial protein synthesis in the rumen. In contrast, lkwuegbu and Sutton (1982) showed that protein metabolism in the rumen is altered as fat supplements interfere with rumen fermentation; infusion of linseed oil into the rumen of sheep decreased protein digestion in the rumen and was accompanied by decreased ammonia concentration in the rumen and increased N flow to the duodenum. Similar changes occurred when sheep were fed additional lipids as either corn oil or lecithin (Jenkins and Fotouhi, 1990).

Incorporation of corn oil in the concentrate fed to Pelibuey hair sheep tended to decrease DM intake of low-quality tropical hay without an effect on rumen degradability and microbial N supply to the small intestine. Additional research is needed to assess the maximum level of incorporation of corn oil in tropical rations fed to ruminant animals.


The authors thank CONACYT-Mexico for financial support through Project No 29366B. J. Herrera-Camacho thanks CONACYT-Mexico for a PhD scholarship at FMVZ-UADY, Merida, Mexico. G.L. Williams acknowledges the Academia Mexicana de Ciencias for financial support for a research visit to FMVZUADY, Mexico.

Received: 01/26/2006. Modified: 06/14/2006. Accepted: 06/16/2006.


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Jose Herrera Camacho. Doctor Universidad Autonoma de Yucatan (UADY), Mexico. Professor, Instituto de Investigaciones Agropecuarias y Forestales (INIFAP), Universidad Michoacana de San Nicolas de Hidalgo, Mexico. Address: Posta Zootecnia. Km 9.5 Carretera Morelia-Zinapecuaro, Morelia, Michoacan. Mexico. e-mail:

Jorge Alfredo Quintal Franco. Ph.D., University of Nebraska, USA. Researcher, INIFAP, Campo Experimental Mococha. Yucatan, Mexico.

Rosario Quijano Cervera. Chemist, UADY. Mexico.

Gary L. Williams. Ph.D., University of Arizona, USA. Re search Leader, A&M University Agricultural Research Station, Beeville, Texas, USA.

Juan Carlos Ku Vera. Ph.D., University of Aberdeen, UK. Professor, UADY, Mexico.

                              Level of corn oil addition in the
                                concentrate (% of dry matter)

                               0                         4

Voluntary DM        665.8 [+ or -] 35.1 (a)   648.8 [+ or -] 35.1 (ab)
  intake of Guinea
  grass hay

Rumen degradation constants

Dry matter (a)
Fraction a (%)      12.7 [+ or -] 1.9         13.3 [+ or -] 1.9
Fraction b (%)      41.3 [+ or -] 2.6         43.2 [+ or -] 2.6
Fraction a+b (%)    54.0 [+ or -] 3.0         56.5 [+ or -] 3.0
Fraction c (%/h)     4.9 [+ or -] 0.8          3.9 [+ or -] 0.8

Organic matter
Fraction a (%)      30.1 [+ or -] 3.2         25.1 [+ or -] 3.2
Fraction b (%)      36.1 [+ or -] 3.1         34.2 [+ or -] 2.5
Fraction a+b (%)    53.4 [+ or -] 4.2         59.3 [+ or -] 4.2
Fraction c (%/h)     5.8 [+ or -] 1.5          6.1 [+ or -] 1.5

Crude protein
Fraction a (%)      40.1 [+ or -] 2.8         32.6 [+ or -] 2.8
Fraction b (%)      31.9 [+ or -] 3.6         39.7 [+ or -] 3.6
Fraction a+b (%)    72.0 [+ or -] 4.0         67.4 [+ or -] 4.0
Fraction c (%/h)     5.3 [+ or -] 1.5          5.7 [+ or -] 1.5

Neutral detergent fiber
Fraction a (%)      15.3 [+ or -] 2.4         16.4 [+ or -] 2.4
Fraction b (%)      38.4 [+ or -] 3.4         40.1 [+ or -] 3.4
Fraction a+b (%)    53.7 [+ or -] 4.9         50.6 [+ or -] 4.9
Fraction c (%/h)     3.2 [+ or -] 0.7 (a)      3.5 [+ or -] 0.7 (ab)
Microbial N supply  4.73 [+ or -] 0.27        6.18 [+ or -] 0.29
  to small

                              Level of corn oil addition in the
                                concentrate (% of dry matter)

                               8                         12

Voluntary DM        558.8 [+ or -] 36.3 (ab)  525.3 [+ or -] 36.3 (b)
  intake of Guinea
  grass hay

Rumen degradation constants

Dry matter (a)
Fraction a (%)      12.6 [+ or -] 1.9          16.5 [+ or -] 1.9
Fraction b (%)      37.8 [+ or -] 2.6          41.1 [+ or -] 2.6
Fraction a+b (%)    50.4 [+ or -] 3.1          57.6 [+ or -] 3.1
Fraction c (%/h)     4.6 [+ or -] 0.8           3.3 [+ or -] 0.8

Organic matter
Fraction a (%)      28.7 [+ or -] 3.3          34.9 [+ or -] 3.3
Fraction b (%)      30.5 [+ or -] 2.9          30.2 [+ or -] 2.6
Fraction a+b (%)    56.1 [+ or -] 4.3          63.5 [+ or -] 4.3
Fraction c (%/h)     5.2 [+ or -] 1.5           3.5 [+ or -] 1.5

Crude protein
Fraction a (%)      29.7 [+ or -] 2.8          39.3 [+ or -] 2.8
Fraction b (%)      36.0 [+ or -] 3.6          31.3 [+ or -] 3.6
Fraction a+b (%)    64.9 [+ or -] 4.0         70.45 [+ or -] 4.0
Fraction c (%/h)     6.3 [+ or -] 1.5           4.6 [+ or -] 1.5

Neutral detergent fiber
Fraction a (%)       9.8 [+ or -] 2.5          12.5 [+ or -] 2.5
Fraction b (%)      34.7 [+ or -] 3.5          45.8 [+ or -] 3.5
Fraction a+b (%)    44.3 [+ or -] 5.0          58.4 [+ or -] 5.0
Fraction c (%/h)     5.7 [+ or -] 0.7 (ab)      2.7 [+ or -] 0.7 (b)
Microbial N supply  5.11 [+ or -] 0.29         5.19 [+ or -] 0.29
  to small

* Mean [+ or -] SE. P= a + b (1-[exp.sup.-ct]).
Means with different superscripts within the same
row differ significantly (P<0.05).

(1) Fractions of DM are a: immediately soluble fraction, b: insoluble,
but potentially degradable fraction, a+b: immediately soluble fraction
plus insoluble, but potentially degradable fraction, and c: rate of
degradation of b.
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Author:Herrera-Camacho, Jose; Quintal-Franco, Jorge A.; Williams, Gary L.; Quijano-Cervera, Rosario; Ku-Ver
Date:Jul 1, 2006
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