52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Proportion of C3 and C4 species in cattle dung in Brachiaria decumbens Stapf. pastures under monoculture
and silvopastoral systems1
Suellen Brandão de Miranda Costa2, Alexandre Carneiro Leão de Mello3, José Carlos Batista Dubeux Junior4,
Mércia Virginia Ferreira dos Santos3, Mario de Andrade Lira5, João Tiago Correia Oliveira6, Janerson José Coêlho7
1
PhD dissertation of the first author, funded by CNPq
PhD candidate, Programa de Pós-Graduação em Zootecnia – UFRPE, Brazil, CNPq scholar. e-mail:
[email protected]
3
Departamento de Zootecnia – UFRPE, BrazilCNPq fellow. e-mail: [email protected], [email protected]
4
University of Florida – North Florida Research and Education Center, Florida, USA e-mail: [email protected]
5
Instituto Agronômico de Pernambuco, IPA, Brazil e-mail: [email protected]
6
PhD candidate, Programa de Pós-Graduação em Zootecnia – UFRPE, Brazil, CNPq scholar. e-mail:
[email protected],
7
MS in Animal Science – UFRPE: [email protected]
2
Instructions for elaborating abstract of Annual Meeting of Animal Science Brazilian Association
Abstract: Silvopastoral System are characterized by a combination of trees, pasture and herbivores, in the same
physical area, in order to obtain diversified products. This study aimed to detect the percentage of C4 and C3 species
in the diet of cattle under Brachiaria decumbens Stapf. pastures in monoculture and silvopasture. The experiment
was carried out at the Instituto Agronômico de Pernambuco. The experimental unit was composed by paddocks of
1.0 ha. The experimental systems used were: Brachiaria decumbens in monoculture, SPS composed by mixed B.
decumbens + M. caesalpiniifolia and B. decumbens + G. sepium. Treatments were allocated in a complete randomized
block design. The δ13C ‰ values in cattle's dung indicated the predominance of C4 plants, probably B. decumbens,
in the diet of the cattle in all treatments. Treatment and cycle interaction affected the proportion of C3 species found
in the cattle’s dung. The greatest percentage of C3 species present in the dung was found in cycle 4 in the SPS B.
decumbens + G. sepium. This was the only cycle that presented significant differences among treatments. The δ13C
in cattle dung indicated little changes in the proportions of C3 and C4 species in the cattle diet during the year. During
the dry season cattle may increase the intake of C3 species, particularly Gliricidia sepium.
Keywords: δ13C, gliricidia, sabia, diet
Resumo: O Sistema silvopastoral são caracterizados por uma combinação de árvores, pasto e herbívoros, na
mesma área física, a fim de obter produtos diversificados. Este estudo teve como objetivo detectar a
percentagem de espécies C4 e C3 na dieta de bovinos em pastagens de Brachiaria decumbens Stapf. em
monocultivo e em e sistema de silvopastagem. O experimento foi realizado no Instituto Agronômico de
Pernambuco. A unidade experimental foi composta por piquetes de 1,0 ha. Os sistemas experimentais
utilizados foram: Brachiaria decumbens em monocultura, SSP composta por B. decumbens mistos + sabiá e
B. decumbens + G. sepium. Os tratamentos foram distribuídos em um delineamento de blocos ao acaso. Os
valores de δ13C ‰ em esterco de gado indicaram a predominância de plantas C4, provavelmente B.
decumbens, na dieta dos bovinos em todos os tratamentos. Interação tratamento e ciclo afetou a proporção de
espécies C3 encontrados no esterco do gado. O maior percentual de espécies C3 presentes no esterco foi
encontrado em ciclo de 4 no SSPS B. decumbens + G. sepium. Este foi o único ciclo que apresentaram
diferenças significativas entre os tratamentos. O δ13C em esterco de gado indicado pequenas alterações nas
proporções de C3 e C4 espécies na dieta de bovinos durante o ano. Durante à estação seca o gado pode
aumentar a ingestão de espécies C3, particularmente Gliricidia sepium.
Palavras–chave: δ13C, gliricidia, sabia, dieta
Introduction
Silvopastoral System (SPS) are characterized by a combination of trees, pasture and herbivores, in the same
physical area, in order to obtain diversified products. The introduction of legume species in SPS can improve the soilplant-animal system, through biological N2-fixation (BNF), increasing nutrients cycling, availability of different
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
sources of protein in animal diet under grazing and the reduction of the need to apply chemical fertilizers (CubillosHinojosa et al. 2011). Two species of arboreal legumes which have been used in SPS in Brazil are sabia (Mimosa
caesalpiniaefolia Benth.) and gliricidia [Gliricidia sepium (Jacq.) Steud]. These species have shown satisfactory
results in terms of animal performance and pasture characteristics (Mello et al. 2014). In addition, they provide other
benefits to the SPS. The study of the composition of animal diet under grazing in mixed pastures is quite complex.
According to Bahar et al. (2005), the use of stable isotope technique can be another tool to assist in the research
related to animal nutrition, when conventional methods cannot predict with accuracy. The stable isotope technique is
an alternative method to the use of internal indicators. In the pastures of the SPS in the tropics, where predominate
the use of combinations of warm-season grasses (C4) and legumes (C3), the measurement of C stable isotopes (δ13C)
can be a useful tool to estimate the proportion of C3 and C4 species consumed by grazing animals. This study aimed
to detect the percentage of C4 and C3 species in the diet of cattle under Brachiaria decumbens Stapf. pastures in
monoculture and silvopastoril system.
Material e Methods
The experiment was carried out at the Instituto Agronômico de Pernambuco, in the city of Itambé - Pernambuco State,
Brazil. The experimental unit was composed by paddocks of 1.0 ha (43.5 x 230.0 m). The experimental systems used
were: Brachiaria decumbens in monoculture, SPS composed by mixed B. decumbens + M. caesalpiniifolia and B.
decumbens + G. sepium. Treatments were allocated in a complete randomized block design, with three replications
per treatment. In the SPS treatment, sabiá seedlings were implanted in 14 double rows, spaced by 15.0 x 1.0 x 0.5 m,
totaling approximately a population of 2,500 plants ha-1, with B. decumbens in the strips between double rows. Cattle
dung were collected, directly from the rectum of eighteen male cattle half-blood (Bos tauros / Bos indicus), during a
period of five consecutive days, and composite samples were obtained from the daily samples. The sampling intervals
consisted of three months, totaling 4 cycles/year. The samples were pre-dried (55°C), and milled in a ball mill. Stable
isotopic composition (δ13C) of composite samples were analyzed at the Centro de Energia Nuclear na Agricultura
(CENA) – USP. Percentage of C3 and C4 plants presented in the dung were calculated according to Jones et al. (1979).
For the estimative of the calculations of the final percentage of 14C were used the following values (braquiária: 25,5;
gliricídia: 25,5 and Sabiá: 32,04) Statistical analyzes were performed using PROC MIXED in SAS 9.1 statistical
package, and means were compared by the probability of the difference (pdiff) with T test adjusted by Tukey-Kramer
(P≤0.05).
Results and Discussion
The δ13C ‰ values in cattle's dung, presented in (table 1), indicate the predominance of C4 plants, probably
B. decumbens, in the diet of the cattle in all treatments. According to Vogel (1993) the δ13C ‰ ranges from -9 to 16 ‰ in plants with C4 metabolism and from -22 to -34 ‰ in C3 plants. The predominance of C4 species in the dung
from cattle in SPS, may be related to the preference of these cattle in consuming the grass instead of the legume.
Species mixture and cycle interacted and affected the proportion of C3 species found in the cattle’s dung (P <0.0001)
(Table 2). The greater percentage of C3 species found in cattle dung occurred in cycle 4 for the SPS B. decumbens +
G. sepium (27.25%). This was the only cycle that presented significant differences (P <0.05) among treatments.
Expected increments in C3 percentage in cycle 4 may be explained by the fact that this cycle occurred in the dry
season, a period where B. decumbens herbage mass was reduced considerably, which probably led the cattle to seek
for others feed sources in the pasture. No increments in C3 percentages in B. decumbens + M. caesalpiniifolia may
be explained by the fact that the sabia is less palatable due to its relatively high concentration of tannins (Beelen et
al., 2006). Lourenço et al. (1984) analyzing carbon isotopes in the cattle dung in the Southeast-Brazil, found
preference for grass (C4) than legumes (C3) in January, and better preferences for legume in April (early dry season)
in mixed pasture. This result was explained by the nutritional quality of the grass that fell during the dry season,
causing increments in the intake of legumes, due to greater protein concentration.
Table 1. Carbon isotopic ratio (δ13C; ‰) in the cattle dung under grazing in Brachiaria decumbens pastures
monoculture and silvopastoral systems.
δ13C (‰)
Cycle
Treatment
B. decumbens
1
2
3
4
-14.781 Aa
-14.105 Aa
-14.015 Aa
-13.527 Ba
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
B. decumbens + G. sepium
-15.265 Aa
-14.266 Aa
-14.633 Aa
-16.405 Aa
B. decumbens + M. caesalpiniaefolia
-14.760 Aa
-14.283 Aa
-14.778 Aa
-14.581 Ba
Standard-error = 0,092
Means followed by the same uppercase letter in the column and lowercase in the line did not differ by Tukey test at
(P>0.05).
Table 2. Percentage of C3 species in the cattle dung under grazing in Brachiaria decumbens pastures monoculture and
silvopastoral systems.
% C3 species
Cycle
Treatment
1
2
3
4
B. decumbens
14.3 Aa
8.9 Aa
8.2 Aa
4.4 Ba
B. decumbens + G. sepium
18.2 Aa
10.2 Aa
13.1 Aa
27.2 Aa
B. decumbens + M. caesalpiniifolia
9.3 Aa
6.8 Aa
9.4 Aa
8.4 Ba
Standard-error = 5.4
Means followed by the same uppercase letter in the column and lowercase in the line did not differ by Tukey test at
(P>0.05).
Conclusions
Cattle dung isotopic composition (δ13C) indicated little changes in the proportions of C3 and C4 species in the cattle
diet during the year. During the dry season cattle may increase the intake of C3 species. Greater crude protein
concentration found in legumes during the dry season might have influence in the diet fluctuation along the season.
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