Composition and digestibility of indigenous grasses in the Hardveld of Botswana during the dry season (Composición y digestibilidad de gramíneas nativas de Bostwana en la estación seca)

A.A. Aganga

Description

Abstract
Available grass species in Sebele ranges were analysed in June, August, October and December of 1999. The mean DM contents were 61.28±1.346, 87.67±0.789, 76.46±0.534 and 64.73±0.453 percent with significance between species. The mean CP was 8.36±0.257, 4.58±0.189, 2.11±0.078 and 2.62±0.104 percent with significant difference between species for all the months.The NDF and ADF contents did not change in these months. The DMD was 50.77±0.258, 41.54±0.497, 44.09±1.586 and 49.14±0.145 percent. It was concluded that the DM, NDF and ADF of all grasses increased, while CP, DMD and mineral content reduced, during dry season.
Resumen
Las especies gramíneas de Sebele, fueron analizadas en junio, agosto, octubre y diciembre de 1999. Los contenidos de materia seca (DM) fueron 61,28±1,346
87,67±0,789
76,46±0,534 y 64,73±0,453 p.100, con diferencias entre especies. La proteína bruta (CP) fue 8,36±0,257
4,58±0,189
2,11±0,078 y 2,62±0,104 con diferencias significativas entre especies todos los meses. NDF y ADF no cambiaron en ese tiempo. La digestibilidad de la materia seca (DMD) fue 50,77±0,258
41,54±0,497
44,09±1,586 y 49,14±0,145 p.100. Se concluye que aumentó el contenido de DM, NDF y ADF y se redujo el de CP, DMD y minerales durante la estación seca.

Sujets

• Ranges
• Pastos

Informations

• Publié par: erevistas
• Publié le: 01 janvier 2005
• Nombre de lectures: 8
• Langue: English

Extrait

COMPOSITION AND DIGESTIBILITY OF INDIGENOUS GRASSES IN
THE HARDVELD OF BOTSWANA DURING THE DRY SEASON
COMPOSICIÓN Y DIGESTIBILIDAD DE GRAMÍNEAS NATIVAS DE BOSTWANA EN LA
ESTACIÓN SECA
Aganga, A.A., U.J. Omphile and N. Mojaditlhogo
Department of Animal Science and Production. Botswana College of Agriculture. Private Bag 0027.
Gaborone.
ADDITIONAL KEYWORDS PALABRAS CLAVE ADICIONALES
Ranges. Nutrient composition. Sebele. Pastos. Composición nutritive. Sebele.
SUMMARY
Available grass species in Sebele ranges rencias significativas entre especies todos los
were analysed in June, August, October and meses. NDF y ADF no cambiaron en ese tiempo.
La digestibilidad de la materia seca (DMD) fueDecember of 1999. The mean DM contents were
61.28±1.346, 87.67±0.789, 76.46±0.534 and 50,77±0,258; 41,54±0,497; 44,09±1,586 y
64.73±0.453 percent with significance between 49,14±0,145 p.100. Se concluye que aumentó el
contenido de DM, NDF y ADF y se redujo el de CP,species. The mean CP was 8.36±0.257,
4.58±0.189, 2.11±0.078 and 2.62±0.104 percent DMD y minerales durante la estación seca.
with significant difference between species for
all the months.The NDF and ADF contents did not
change in these months. The DMD was INTRODUCTION
50.77±0.258, 41.54±0.497, 44.09±1.586 and
49.14±0.145 percent. It was concluded that the The greater part of the Sebele
DM, NDF and ADF of all grasses increased, while rangeland is covered with grasses in
CP, DMD and mineral content reduced, during dry combination with forest trees, woodland
season. trees, or shrubs or as open savanna
grassland areas. Numerous factors
affect the type of grassland to be found
RESUMEN in a given area; the annual rainfall,
which in Botswana is generally lessLas especies gramíneas de Sebele, fueron
than 750 mm; the soil type, which foranalizadas en junio, agosto, octubre y diciembre
the most part is sub-desert sand or atde 1999. Los contenidos de materia seca (DM)
least of a sandy nature, and thefueron 61,28±1,346; 87,67±0,789; 76,46±0,534
influence of man, such as the veldy 64,73±0,453 p.100, con diferencias entre es-
burning and overgrazing (Field, 1976).pecies. La proteína bruta (CP) fue 8,36±0,257;
4,58±0,189; 2,11±0,078 y 2,62±0,104 con dife- Cattle kept by traditional farmers in
Arch. Zootec. 54: 587-598. 2005.
ChemicalAganga.p65 587 23/01/2006, 9:58AGANGA, OMPHILE AND MOJADITLHOGO
Botswana relies almost solely on et al., 1963). In general therefore, the
production of fodder from the natural composition of pasture dry matter is
rangelands, and is likely to do so for very variable (Ferguson, 1963).
many decades to come. Thus to Limited work on chemical compo-
maintain a viable cattle industry it must sition, nutritional value, intake and
be first maintained rangelands in a extremely limited work on palatability
good condition. Due to overstocking of grasses is available, so the main
and mis-management, large areas of asset of this study is to include data on
Botswana's grasslands are now in poor the nutritive value of a wide range of
conditions. native range grasses.
The nutritive value of a forage refers
to its chemical composition, digestibility
and the nature of digested products; MATERIALS AND METHODS
the amount of forage consumed by an
Grass species shown in table IIanimal affects the total nutrient intake
were sampled (3 replicates) every twoand therefore the animal response.
months from June to December 1999Various factors such as acceptability,
(table I shows meteorological data).presence of undesirable substances,
The samples were hand clipped atrate of passage and availability of
grazing height from the Sebele ranges,forage, influence consumption by
collected in brown sampling bags,animals. Thus assessment of herbage
oweighed and oven dried at 60 C for 72quality involves an integrated evalua-
hours. The dried samples were weighedtion of its nutritive value and its level of
(to determine DM), milled through aconsumption (Chheda and Cowder,
2.5 mm screen, labelled and stored.1982). The chemical composition of
Chemical analysis (ash, crude proteingrass is greately influenced by the
and detergent fibre) were done in threestage of growth of the plants, the
replicates using procedures of AOACbotanical composition of the sward,
(1995). Crude protein was determinedthe nutrient status of the soil, the climate
by using the Kjeldahl method: digestionand the management of the sward (Tribe
for six hours with 20 ml of concentrated
sulphuric acid plus selenium mixture
Table I. Meteorological data, 1999. (Datos and then allowed to cool for 40-60
meteorológicos de 1999). minutes. 100 ml of distilled water were
added to each digest and then left
Mr Rh T max T min overnight. The samples were then
distilled and titrated to get the nitrogen
June 0.0 67 24.4 6.3 content. The protein content was
August 0.0 57 26.6 8.1 calculated as N multiplied by 6.25.
October 2.8 54 30.9 15.4
Minerals were determined with flame
December 43.4 69 34.1 19.2
photometer (K, Na) or atomic spectro-
meter (Ca, Cu, Mg, Fe, Zn, Mn). DryMr= Month rainfall (mm); Rh= Relative humidity
o matter true digestibility was determined(percent); T= Temperature ( C).
by the in vitro method: the samples
Archivos de zootecnia vol. 54, núm. 208, p. 588.
ChemicalAganga.p65 588 23/01/2006, 9:58NUTRITIVE VALUE OF INDIGENOUS GRASSES IN THE HARDVELD OF BOTSWANA
were put in the bottles with 400 ml of thus ranging from 32.64 for C.ciliaris
rumen liquor from a fistulated steer to 78.38 percent for H.contortus. The
and a mixture of buffer solutions A and crude protein ranges from 4.87 for H.
B, and heated in a daisy incubator at contortus to 16.03 percent for C.
o39 C for forty-eight hours. Acid ciliaris (p<0.05). The NDF and ADF
detergent fibre (ADF) and neutral were not different between the species.
detergent fibre (NDF) were determined The IVTD is ranging from 39.6 for D.
by methods of Goering and Van Soest cinerea to 60.4 for B. insulpta. The
(1970). Ash content was determined two species are significantly different
oby ashing in a muffle furnace at 550 C from each other and to other species.
for 6 hours. Ash content averages at 9.94 percent.
The data were subjected to analysis It seems (table III) to have high
of variance using SAS and the means content of K, the highest being E.
within and between grass species were rigidor with 42.29 and lowest being H.
compared using the Duncan's New contortus with 4.81 g/kg, there is
Multiple Range Test. significant difference between the
species. The Na content is almost the
same for all grasses and it is generally
RESULTS low. The Ca content is fairly high, D.
cinerea being the highest with 14.02 g/
In June 1999 (table II), the dry kg and E. rigidor being the lowest with
matter content shows some difference 1.05. The Mg content ranges from
Table II. Nutritive composition (percent) of locally available grasses collected in June 1999.
(Composición nutritiva (p.100) de las gramíneas locales disponibles en junio de 1999).
Samples DM CP NDF ADF ASH IVTD
b a a a a bPanicum maximum 49.8±0.35 9.72±1.83 68.8±0.66 39.3±1.40 11.38±0.38 52.2±0.39
a b a a b bEragrostis rigidor 72.40±0.74 5.11±0.35 74.3±0.17 43.4±0.76 7.00±0.92 45.6±0.82
a a a a a bSchimidta pappophoroides 63.45±0.52 8.97±1.02 73.3±0.23 43.7±0.13 10.05±1.12 47.6±1.32
a a a a a bBrachiaria nigropedata 63.78±0.53 8.35±0.93 74.5±1.28 39.0±0.62 13.95±0.62 55.0±0.57
b a a a a bUrochloa trichopus 51.00±0.43 8.50±0.12 67.6±0.47 42.1±0.07 16.58±0.48 58.0±0.79
a a a a b bDigitaria milangiana 63.28±0.49 7.25±0.10 70.2±0.63 44.5±0.67 7.70±0.41 50.2±1.05
b a a a a bCenchrus ciliaris 32.64±0.27 16.03±0.42 64.2±0.02 35.5±0.78 11.04±0.67 57.6±0.63
b a a a a bEragrostis lehmanniana 51.98±0.44 7.76±0.19 72.9±0.77 44.5±0.51 10.68±1.37 50.2±0.48
b a a a a bEragrostis superba 53.11±0.47 8.36±1.53 76.4±0.52 42.5±1.27 9.51±0.74 50.2±0.78
a b a a b bRhyncelytrium repens 68.07±0.36 5.23±0.57 76.1±0.89 49.5±0.92 8.28±0.20 53.4±1.82
a b a a b bHeteropogon contortus 78.38±0.85 4.87±0.65 76.0±1.52 47.8±0.78 7.50±0.54 44.6±0.89
a a a a a bCynodon dactylon 69.54±0.37 8.05±1.25 75.6±0.38 39.4±0.35 9.19±0.94 43.4±0.56
a a a a a aBothriochloa insculpta 66.83±0.55 7.73±0.83 74.6±0.65 48.7±0.52 9.86±1.47 60.4±0.83
a a a a a bAnthephora pubescens 70.40±0.45 7.88±0.37 72.2±0.52 43.8±0.73 9.37±0.28 53.6±0.17
abcKey: means with different superscripts along the same column are significantly different at p<0.05.
Archivos de zootecnia vol. 54, núm. 208, p. 589.
ChemicalAganga.p65 589 23/01/2006, 9:58AGANGA, OMPHILE AND MOJADITLHOGO
Table III. Mineral composition of locally available grasses collected in June 1999. (Compo-
sición mineral de las gramíneas locales disponibles en junio de 1999).
Major minerals (g/kg) Minor minerals (