|Livestock Research for Rural Development 13 (4) 2001||
Citation of this paper
An experiment was conducted to determine the nutritive value of forage collected via oesophageal fistula with two cows that grazed two pastures: native grass (NP) and NP associated with Arachis pintoi CIAT 17434 (NP+Ap), both in the morning (between 7 and 8 AM) and in the afternoon (between 5 and 6 PM). Rumen degradation was expressed as y = a + b(1 - e-ct), where y, is the dry matter degraded at time t, a is the highly soluble dry matter when t = 0 (%), b is the insoluble but slowly degradable dry matter (%), a+b is the extent of degradation (%), c is the degradation rate of b (%/h) and t is the rumen incubation time (h).
Neither cow nor time of grazing had a significant effect upon the immediately soluble fraction (a) or the insoluble but rumen degradable fraction (b). However, the effect of pasture was significant upon c, the degradation rate of b, being the values 4.07 %/h and 7.66 %/h for NP and NP+Ap, respectively. Crude protein content (CP) was not affected by cow or time of grazing, but the effect of pasture was highly significant. The cows in NP harvested material with 9.8% CP while those in the NP+Ap selected forage with 13.5% CP in dry matter. The relationship between CP and percent A. pintoi in extrusa was not significant due to a limited number of observations (n=7). The NP and NP+Ap pastures showed 9.12 g of CP/MJ of ME and 11.84 g of CP/MJ of ME, enough to support maintenance, pregnancy and 4 and >6 kg of milk/cow/day, respectively.
It was concluded that the NP+Ap pasture presented a
higher nutritive quality than the NP pasture and, as a
consequence, a higher milk production potential.
The mixture of pasture legumes and grasses has been proposed
as an alternative to improve the nutritive quality of the diet of
the grazing ruminant in the tropics (Norton and Poppi 1995). If
the grass basal diet is limiting in nutrients for the microbial
population of the rumen, the inclusion of a legume increases the
digestibility and dry matter intake and thus leads to increases
in animal production. Also, if the diet is adequate in nutrients
and besides there is protein with a low rumen degradability
supplied by the legume, dry matter intake may not increase, but
animal production can increase due to the presence of by-pass
protein. Since cattle consume mostly leaves from the legume when
it is mixed with a grass, intake increases because rumen
retention time decreases (Poppi and Norton 1995). For these
reasons, it is necessary to know the nutritional characteristics
of the mixed pasture ingested by the grazing ruminant with the
aim of evaluating its animal production potential.
In general, it is recommended to use oesophageally fistulated
animals to obtain representative samples of the ingested forage (McManus
1981), because the grazing ruminant can select material of a very
different nutritive quality than that collected by hand, either
when clipped (Salman et al 2000) or when grazing is
imitated by the "hand plucking" sampling technique (Ibrahim
1994). However, sampling with oesophageally fistulated animals
also has its limitations. Short time grazing periods of
fistulated non-resident animals could lead to a higher proportion
of legume in the diet, in comparison to non-fistulated resident
animals (Jones and Lascano 1992).
The in situ or in sacco technique allows the
evaluation of characteristics such as the rate and extent of
digestion, which are highly related to the nutritive quality of a
forage (Marten 1981; Minson 1981).
The objective of the present study was to compare the rate and
extent of digestion, as well as the crude protein content, of the
oesophageal extrusa from native grass pastures and native grass
mixed with Arachis pintoi CIAT 17434, in order to observe
if the introduction of this legume into native grass pastures was
of benefit to the diet of F1 (Holstein x Zebu) cows.
The experiment was conducted at the Centro de Enseñanza,
Investigación y Extensión en Ganadería Tropical (Center for
Education, Research and Extension in Tropical Livestock
Production) of the Faculty of Veterinary Medicine and Zootechnics
of the National Autonomous University of Mexico. The Center is
located in the coastal plains of the Gulf of Mexico at 23° 04
N latitude, 97° 03 W longitude and 105 meters above sea
level. There are three climatic seasons: a) dry from
March to June (30.6 ± 1.7 °C and 19.9 ± 1.7 °C of maximum and
minimum temperatures, respectively, and 477 ± 343 mm of rainfall),
b) rainy from July to October (31.2 ± 1.3 °C and 20.5
± 1.8 °C of maximum and minimum temperatures, respectively, and
1032 ± 612 mm of rainfall) and, c) winter from
November to February (25.0 ± 2.1 °C and 15.1 ± 1.3 °C of
maximum and minimum temperatures, respectively, and 482 ± 268 mm
of rainfall). The soils are classified as Ultisols, acid (pH 4.1-5.2)
of low fertility (1-2 ppm of available P), with no Al toxicity
problems. Soils are shallow (1-20 cm) and the horizon A
overlays a hardpan that makes drainage difficult during the rainy
season. Native pastures are the main source of feed for grazing
ruminants. These pastures consist of a mixture of grasses from
the genera Paspalum, Axonopus, Cynodon and Setaria
and legumes of the genera Desmodium and Centrosema.
The content of native legumes is very low, from 2.5% to 15.4%
and, on the average, the legumes comprise only 5% of the native
pasture dry matter yield (Bosman et al 1990). In general terms,
the year-round carrying capacity of these pastures is about 1 cow/ha
(Aluja and Mc Dowell 1984).
The experiment took place between
September and November 1999. There were two pastures (P): native
pasture (NP) and NP associated with Arachis pintoi CIAT
17434 (NP+Ap), each one with an area of 2.5 ha pasture. Each
pasture had 21 sections for the rotational grazing with one day
of grazing and 20 days of recovery. The stocking rate was 2 cows/ha.
Two oesophageally fistulated
cows were used for 0.5 h periods from 7 to 8 in the morning (AM)
and from 5 to 6 in the afternoon (PM), in order to obtain
oesophageal extrusa samples. The NP+Ap mixture was sampled six
times on 26 and 29 September and 2, 8, 13 and 23 October, whereas
the NP pasture was sampled seven times on 4, 10, 11, 16, 19, 22
and 24 November. Sampling periods were confounded with pasture
treatment. However, it was considered that if the legume was
indeed ingested, it would lead to higher contents of crude
protein and digestible dry matter. Once the extrusa were
collected, the liquid portion was eliminated by applying gentle
pressure against a cheesecloth and then the sample was frozen (-20
°C) and stored until processed.
The rate and extent of the
digestion were estimated by rumen incubation in a fistulated bull
with a permanent cannula, using incubation times of 3, 6, 9, 12,
24, 48 and 72 h; 20 g of previously unfrozen extrusa were put
into a 10 cm x 20 cm dacron bag; triplicates of each incubation
time were used. The zero time was obtained by washing
the bag with the sample, in water at 39 °C for 30 min. Dry
matter degradation was described with the equation proposed by Ørskov
and McDonald (1979):
= a + b(1 - e-ct),
where y, is
the dry matter degraded at time t, a is
the highly soluble dry matter when t = 0 (%), b is
the insoluble but slowly degradable dry matter (%), a+b
is the extension of degradation (%), c is the
degradation rate of b (%/h) y and t is the rumen
incubation time (h). The parameters of the equations
corresponding to each available combination among pasture (P),
date (D), sampling time (S) and cow (C) were estimated with a
least squares iterative procedure devised by Chen (2000), which
is incorporated in the NEWAY software, provided on line by The
International Feed Resources Unit (IFRU), Aberdeen, Scotland.
The literature mentions
that the use of use of at least three animals do not compromise
accuracy when in situ degradability is estimated (Mehrez
and Ørskov 1977). However, studies conducted by our
research group indicated a non significant effect of the animal
on in situ degradability estimations of dried and ground
native legumes (Coutiño et al 2000) or proteinacious meals from
vegetal and animal origin (Ramírez et al 1999), when six rumen
fistulated bulls grazing African Stargrass (Cynodon
nlemfuensis) were used. This suggests that for our conditions
one bull is sufficient to estimate the rate and extent of
A portion of the extrusa
was not frozen but was dried at 60°C/72 h, ground in a Wiley
mill to pass a 2 mm screen and its crude protein determined in
duplicate according to the Kjeldahl procedure (AOAC 1980).
The equation parameters and the
crude protein content were analyzed by analysis of variance with
a model that included the main effects of P, S, and C, using the
variation among days (D) to generate the experimental error.
Interactions among P, S and C were not included because the
treatment design was not balanced; for the same reason, type 3
sums of squares were used. These analyses were performed with the
PROC GLM procedure of SAS (SAS 1982).
The crude protein content of the
extrusa was related to the contribution of A. pintoi to
the botanical composition of the same extrusa, which was
estimated according to a technique adapted for microscopic
observation (Harker et al 1964), the model was:
= b0 + b1(CPTAP),
where CP = crude protein in dry
matter and CPTAP = contribution of A. pintoi to the
botanical composition, b0 is the intercept or the
value of CP when CPTAP=0 and b1 is the slope or units
of increase in CP per unit of increase in CPTAP. The model was
fitted with the SAS PROC GLM procedure (SAS 1982).
The metabolizable energy (ME, MJ/kg
of DM) of extrusa samples was calculated with the formula:
where ME is the metabolizable
energy in MJ/kg DM, GE is the gross energy of dry matter (18.5 MJ/kg
DM), D48 is the dry matter digestibility after 48 h of
rumen incubation, predicted from the equation of Ørskov and Mc
Donald (1979), and 0.81 is a conversion factor from digestible
energy (DE) to ME (AFRC 1993). The protein to energy ratio (P/E,
g CP/MJ of ME) was calculated from the CP and ME data, and the
resultant P/E values were compared to those given by Martin (1998)
for different levels of production of cattle grazing tropical
Only sampling time had a
significant effect upon a, being 12 percent points
higher for the AM sampling time. The effect of cow was close to
being significant (P=0.06). Cow A had a mean 11.3
percent points higher value than that of cow B (Table
1. Digestion parameters from oesophageal extrusa
samples obtained with two oesophageally fistulated cows
that grazed native grass (NP) or NP associated with Arachis
pintoi (NP+Ap), in the morning (AM) and the afternoon
(PM), between September and November, 1999. Values are
means ± standard errors.
Degradation equation parameters*
31.6 ± 3.37 a
46.9 ± 2.64 a
78.6 ± 2.41 a
-0.0407 ± 0.0090 a
2.54 ± 0.51 a
30.6 ± 3.51 a
44.6 ± 2.75 a
75.2 ± 2.51 a
-0.0766 ± 0.0094 b
2.69 ± 0.53 a
37.1 ± 3.25 a
42.0 ± 2.55 a
79.2 ± 2.32 a
-0.0532 ± 0.0087 a
2.54 ± 0.49 a
25.1 ± 4.05 b
49.5 ± 3.17 a
74.6 ± 2.89 a
-0.0640 ± 0.0108 a
2.69 ± 0.61 a
36.8 ± 4.04 a
43.2 ± 3.17 a
80.0 ± 2.88 a
-0.0536 ± 0.0108 a
2.52 ± 0.61 a
25.5 ± 3.32 a
48.4 ± 2.60 a
73.8 ± 2.37 a
-0.0636 ± 0.0088 a
2.71 ± 0.50 a
For each variable, means within column, followed by the
same letter are statistically the same (P>0.05).
** RSD is the residual standard deviation.
The effects of P, S and C were not
significant upon b and a+b. The
degradation rate c, was significantly affected
by P; the forage harvested by the cows in pasture NP+Ap was
degraded twice as fast as that harvested in pasture NP (Table 1;
Figure 1). Neither S nor C had a significant effect on c.
1. Dry matter degradation of oesophageal
extrusa from two oesophageally fistulated cows that
grazed native grass (NP, - - - - - ) or NP associated
with Arachis pintoi (NP+Ap, ________ ) sampled
between 26 September and 24 November of 1999. Equations
are described in Table 1.
The c values range from
3 to 6%/h for tropical grasses and are higher in young regrowth.
Alayón (1996) found that Stargrass (Cynodon nlemfuensis)
hay used in integral rations with foliage of Gliricidia sepium
plus molasses and minerals had a degradation rate of 3.6%/h. The
c value for Guineagrass (Panicum maximum)
harvested 90 days after planting was 2.9%/h, while the value for
a 33 day regrowth was 4.8%/h (Singh and Gupta 1996). Elephant
grass (Pennisetum purpureum) harvested when it reached a
height of 1 m, showed c values from 3.0%/h to 4.0%/h,
depending on whether the supplement used was Gliricidia sepium
or Leucaena leucocephala (Abdulrazak et al 1996).
There is no published information about degradation rates of
tropical native grass pastures of México. The 4.07%/h for NP of
this experiment (Table 1), lies within the typical values for
young grass regrowth and this was a product of the short recovery
period given to the pastures.
Some legumes, particularly the
leaves, show a high ruminal degradation, which is independent of
age. Berseem clover (Trifolium alexandrinum) showed a
c value of 10.8%/h for material harvested 79 days
after planting, and for 26 day regrowth it was 10.5%/h, (Singh and
Gupta 1996). Respective degradation rates for stems were 10.1 and
8.9%/h. Abdulrazak et al (1996) found that c
values of foliage from G. sepium and L.
leucocephala fluctuated from 5.2 to 7.6%/h and from 4.0 to 5.2%/h,
respectively, when these legumes were given as supplements to
steers with a basal diet of Elephant grass. However, if the basal
diet was corn stover, the values went from 9.2 to 12.0%/h for G.
sepium and from 7.2 to 9.4%/h for L. leucocephala (Abdulrazak
et al 1997). Alayón (1996) estimated a degradation rate of 10.7%/h
for G. sepium foliage.
There is no known published
information on degradation rates of forage harvested by
oesophageally fistulated cows from tropical grass/legume mixtures.
Hess et al (1999) found that dried leaves of A. pintoi had
a c value of 6.02%/h. In the present case, a value of
c of 7.66%/h for NP+Ap was inferior to that of most
legumes mentioned above, but it was almost two times that
estimated for NP. This indicated that the addition of A.
pintoi to the diet of the cow, increased the rate of
degradation of dry matter (Figure 1).
The effect of P upon CP content was highly significant (P<0.01). The CP of the NP pasture was 3.7 percent points lower than that of the NP+Ap pasture (Figure 2). The effects of S and C were not significant (P>0.05; Figure 2).
2. Effect of pasture (NP, NP+Ap),
sampling time (AM, PM) and cow (A, B) on crude protein
content of oesophageal extrusa. Bars are means and
vertical lines are standard deviations.
data indicate that the CP of the oesophageal extrusa from the NP+Ap
pasture increased due to the inclusion of A. pintoi in the
diet. Nevertheless, both pastures showed CP contents above the
critical value of 7% (Milford and Minson 1966). It has been shown
that when CP falls below this value, the dry matter intake of
stalled animals eating forages only is reduced in response to a N
deficit in the rumen (Siebert and Kennedy 1972; Humphreys 1991).
though the difference was not significant, the CP content of
extrusa collected in the morning was higher than that from the
afternoon sampling, which was probably due to the fact that the
cows entered into a new pasture every morning, and for this
reason they had a higher dry matter availability which allowed
them to choose forage of higher quality. By the afternoon
sampling, the cows had already ingested the most nutritious
portion of the pasture and therefore, the CP was lower. The
reduction in pasture quality with progressed grazing has been
reported by other researchers (Chacón and Stobbs 1976; Ibrahim
1994). Therefore, our finding justifies sampling two times during
the day (AM and PM) if we expect to collect representative data
on forage ingested by grazing cows (Chacón and Stobbs 1977).
periods were confounded with pasture treatments and this could
have lead to significant differences among treatments. However,
standing dry matter (SDM, kg/ha) before grazing was high: 6200
and 7202 kg/ha for NP and NP+Ap, respectively. Thus, grazing
pressure was very lenient: 29.3 and 35.1 kg of SDM/100 kg of live
weight/day. Respective pasture utilization rates were 11.4% and
13.6% of SDM before grazing (Monsalve 2000). Therefore, it was
unlikely that sampling period was a factor responsible for
differences in the nutritive quality of ingested forage.
In this experiment, the relationship between the CP content of the extrusa and the contribution of A. pintoi to the botanical composition of the extrusa was not significant (P>0.05). The equation: CP = 11.8 +0.077(CPTAP), R2 = 0.43, n = 7, predicted that without a legume, the CP content would be 11.8% and that for a unit of increase of the legume in the botanical composition (range from 2% to 56%), the CP would increase by 0.077 percent points (Figure 3). This result was not very different to that of Ibrahim (1994) in spite of the fact that he did find a highly significant relationship between extrusa CP and percent A. pintoi in the botanical composition (range from 5% to 76%). His equation was: CP = 12.0 + 0.11(CPTAP), R2 = 0.89, which indicated that for each unit of increase in A. pintoi, the CP increased by 0.11%. In our case, the lack of significance for the regression was due to the scarce number of observations, but also to a tendency to have high CP values with intermediate A. pintoi contents (Figure 3).
3 Relationship between the contribution of Arachis
pintoi to the botanical composition of the extrusa
and crude protein content of the extrusa. Equation is
described in text.
The P/E ratio was 9.12 and 11.8 g of CP/MJ of ME
for NP and NP+Ap pastures, respectively. Martin (1998) found that
the mean P/E ratios for a group of grasses were: 12.30 and 9.74
for young and mature grasses, respectively. For the rainy and dry
seasons the values were 12.0 and 11.5, respectively. According to
this author, even mature grasses had enough nutritive quality to
support maintenance, pregnancy and a milk production of 4 to 6 kg/cow/day.
Our data indicate that the potential production for NP
pastures is enough to give a milk yield of 4 kg/cow/day, besides
maintenance and pregnancy. On the other hand, the potential
production for the NP+Ap pasture appears to be well beyond that
of 6 kg/cow/day plus maintenance and pregnancy, cited by Martin (1998).
Therefore the grass/legume association had a higher estimated
potential for milk production than that of the NP pasture.
However, it should be considered that the nutrient requirements
are covered not only with nutritive quality but with dry matter
intake also. Thus, two forages can have the same P/E ratio, but
their intakes can be widely different (Martin 1998). For this
reason, in this type of study the measurement of dry matter
intake is also advisable.
It was concluded that the native grass/introduced legume association showed a higher nutritive quality than that of the native grass/native legume pasture, and that as a consequence, the former has a higher estimated production potential.
Financial support received from the Consejo Nacional de
Ciencia y Tecnología (National Council for Science and
Technology - CONACYT) through the Sistema de Investigación del
Golfo de México (Gulf of Mexico Research System - SIGOLFO)
through the research grant 97-01-014-V Improving a native
pasture with the legume Arachis pintoi CIAT 17434 is
gratefully acknowledged. The authors also thank the provision of
facilities by the Faculty of Veterinary Medicine and Animal
Production of the National Autonomous University of México.
Abdulrazak S A, Muinga R W,
Thorpe W and Ørskov E R 1996 The effects of supplementation
with Gliricidia sepium or Leucaena leucocephala
forage on intake, digestion and live-weight gains of Bos
taurus x Bos indicus steers offered napiergrass.
Animal Science 63: 381-388.
Abdulrazak S A, Muinga R W,
Thorpe W and Ørskov E R 1997 Supplementation with Gliricidia
sepium and Leucaena leucocephala on voluntary food
intake, digestibility, rumen fermentation and live weight of
crossbred steers offered Zea mays stover. Livestock
Production Science 49:53-62.
AFRC 1993 Energy and Protein
Requirements of Ruminants. Agricultural and Food Research Council-Technical
Commitee on Responses to Nutrients. CAB International, UK.
Alayón J A 1996 Evaluación
de métodos de siembra y del efecto de la inclusión de Gliricidia
sepium (Jacq.) Steud en dietas de heno de Cynodon
nlemfuensis en ovinos Pelibuey. Tesis de Maestría en
Ciencias. Facultad de Medicina Veterinaria y Zootecnia,
Universidad Autónoma de Yucatán. Mérida, Yucatán, México.
Aluja A and Mc Dowell R E 1984 Decision making process
of livestock/crop small holders in the State of Veracruz, México.
Cornell University International Agriculture Mimeographs. pp 105.
AOAC 1980 Official Methods of Analysis. 13th
ed. Association of Official Analytical Chemists, Washington, DC
Bosman H, Castillo E, Valles B y De Lucía G R 1990
Composición botánica y nodulación de leguminosas en las
pasturas nativas de la planicie costera del Golfo de México.
Pasturas Tropicales 12:2-8.
Chacón E and Stobbs T H 1976
Influence of progressive defoliation of a grass sward on the
eating behavior of cattle. Australian Journal of Agricultural
Chacon E and Stobbs T H 1977
The effects of fasting prior to sampling and diurnal variation on
certain aspects of grazing behavior in cattle. Applied Animal
Chen X B 2000 NEWAY: Curve fitting programme software
for Orskovs model (DOS version). International Feed
Resources Unit, Macaulay Land Use Research Institute, Aberdeen,
Coutiño O, Castillo G E, Keilbach B N M, Aluja S A y
Jarillo R J 2000 Digestibilidad in vitro e in situ
de cuatro leguminosas nativas colectadas en pasturas de Misantla,
Veracruz. Memorias de la XXXVI Reunión Nacional de Investigación
Pecuaria en México. INIFAP, México. Página 86.
Harker K M, Torell D T and Van
Dyne G M 1964 Botanical examination of forage from
oesophageal fistulas in cattle. Journal of Animal Science 23:465-469.
Hess H D, Florez H, González E
y Avila M 1999 Efecto del nivel de nitrógeno amoniacal en el
rumen sobre el consumo voluntario y digestibilidad in situ de
forrajes tropicales. Pasturas Tropicales 21:43-48.
Humphreys L R 1991 Tropical Pasture Utilization.
Cambridge University Press, UK.
Ibrahim M A 1994
Compatibility, persistence and productivity of grass-legume
mixtures for sustainable animal production in the Atlantic Zone
of Costa Rica. Ph. D. Thesis. Wageningen Agricultural University.
Wageningen, The Netherlands.
Jones R J and Lascano C E 1992
Oesophageal fistulated cattle can give unreliable estimates of
the proportion of legume in the diets of resident animals grazing
tropical pastures. Grass and Forage Science 47:128-132.
Marten G C 1981 Chemical, in vitro and nylon bag
procedures for evaluating forage in the USA. In Wheeler J L and
Mochrie R D. Forage Evaluation: Concepts and Techniques. CSIRO,
Australia and AFGC, USA. Pages 249-260.
P C 1998 Valor nutritivo de las gramíneas tropicales.
Revista Cubana de Ciencias Agrícolas 32:1-10.
McManus W R 1981 Oesophageal fistulation technique as
an aid to diet evaluation of the grazing ruminant. In Wheeler J L
and Mochrie R D. Forage Evaluation: Concepts and Techniques. CSIRO,
Australia and AFGC, USA. Pages 39-55.
Mehrez A Z and Ørskov
E R 1977 A study of the artificial fibre bag technique for
determining the digestibility of feeds in the rumen. Journal of
Agricultural Science (Cambridge) 88:645-650.
Milford R and
Minson D J 1966 Intake of tropical pasture species. Proc. 9th
Intern. Grassland Congress. Sao Paulo, Brazil, Pages 815-822.
Minson D J 1981 An Australian view of laboratory
techniques for forage evaluation. In Wheeler J L and Mochrie R D.
Forage Evaluation: Concepts and Techniques. CSIRO, Australia and
AFGC, USA. Pages 57-73.
Monsalve L R A 2000 Composición botánica del forraje
ingerido por vacas F1 (Holstein x Cebú) que pastaron gramas
nativas y gramas nativas asociadas a Arachis pintoi,
durante la transición entre las épocas de lluvias y nortes en
un sitio con clima Af(m) del estado de Veracruz, México. Tesis
de Licenciatura en Medicina Veterinaria. Facultad de Medicina
Veterinaria, Universidad de Ciencias Aplicadas y Ambientales,
Santa Fé de Bogotá, Colombia y Facultad de Medicina Veterinaria
y Zootecnia, Universidad Nacional Autónoma de México. México,
D. F. México.
Norton B W and Poppi D P 1995 Composition and
nutritional attributes of pasture legumes. In DMello J F P
and Devendra C. Tropical Legumes in Animal Nutrition. CAB
International, UK. Pages 23-47.
Ørskov E R and Mc Donald I 1979
The estimation of protein degradability in the rumen from
incubation measurements weighted according to rate of passage.
Journal of Agricultural Sciences Cambridge, 92:499-503.
Poppi D P and Norton B W 1995
Intake of tropical legumes. In DMello J F P and Devendra C.
Tropical Legumes in Animal Nutrition. CAB International, UK.
Ramírez R E, Jarillo R J, Castillo G E, Ku J C y Ramírez
A L 1999 Degradación ruminal de la proteina cruda y materia
seca de harinas proteicas en toros bajo condiciones de pastoreo
en el trópico. Memorias de la XXXV Reunión Nacional de
Investigación Pecuaria en México. INIFAP, México. Página 248.
Salman A K D, Berchielli T T, Silveira R N, Soares W V B,
Nogueira J R e Kronka S N 2000 Degradabilidade in situ
do capim Panicum maximum cv. Tanzania incubado cortado ou
na forma de extrusa. Revista Brasileira de Zootecnia 29:2142-2149
SAS 1982 SAS Users
Guide: Statistics. SAS Institute, Cary, NC, USA.
Siebert B D and Kennedy P M 1972 The utilization of
spear grass (Heteropogon contortus). 1. Factors limiting
intake and utilization by cattle and sheep. Australian Journal of
Agricultural Research 23:35-44.
Singh M and Gupta B K 1996 In sacco degradability of dry matter of Berseem and Guineagrass forage at different stages of growth. Indian Journal of Dairy Science 49: 81-86.
Received 28 June 2001
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