Potential and effective degradation of mulberry clones in goats

Anita Schmidek & R. Takahashi
Faculty of Agrarian and Veterinary Sciences
São Paulo State University, Jaboticabal Campus
São Paulo, Brazil
A. Nuñes de Medeiros
Depto. Agropecuária-CFT- UFPB-Campus IV
Bananeiras-PB, Brazil
K.T. de Resende
Faculty of Agrarian and Veterinary Sciences
São Paulo State University, Jaboticabal Campus
São Paulo, Brazil

INTRODUCTION

Mulberry has been shown to have a considerable potential for feeding goats, both from the biological and economic points of view, since it is well accepted by these animals, has high contents of CP and TDN and a good green biomass production per unit area with a deep root system, which allows good production throughout the year including the dry period (Takahashi, 1998).

Currently the in situ degradation technique has been extensively used to determine the rate and dynamics of feed degradation in the rumen, enabling the soluble, microbial degradable and undegradable fractions to be identified as well as the time required for this to happen. From these data, potential degradability (PD) and effective degradability (ED) can be estimated.

Feed degradation rate can be used to predict nutritional value since it is related to voluntary feed intake (Aguiar et al., 1997). Feeds with higher degradation remain less time in the rumen allowing a greater intake.

The objective of this study was to analyse the potential and effective degradation and the fractions of the equation by Ørskov (1979) of three mulberry clones.

MATERIALS AND METHODS

Research was conducted in the Goat Husbandry Section of the Faculty of Agrarian and Veterinary Sciences, Jaboticabal Campus of São Paulo State University (Brasil), using mulberry cultivated by the Sericulture Section. Leaves with 90 days of regrowth from the clones Miura, FM Shima Miura and FM 86 were used.

For the incubation five two-year old Saanen wethers with a rumen cannula kept in a group pen were used. Their diet consisted of Tifton hay, mulberry hay and 300 g of a concentrate with 21 percent CP. After an adaptation period of 21 days, the ground leaves were incubated for 0, 6, 12, 24, 48 and 96 hours.

Analysis of DM, CP and TDN were made on the material to be incubated and on the residue (Silva, 1981). The estimation of fractions "A", "B" and "C" were based on the recommendation by Ørskov (1988) and were used to calculate degradation by means of the equations PD =A + B (1 - ect) and ED = A + (B * c)/(c + kp).

The experimental design was random blocks with split plots (mulberry clones) with five repetitions (animals) and five plots (incubation times). The various parameters were subjected to the Tukey test at 5 percent.

RESULTS AND DISCUSSION

Table 1 presents the values of the fractions studied. Compared to the commonly used forages for goats, mulberry clones showed a large soluble fraction (A) with a mean value of 31.4 percent and a large potential degradable fraction (B) with a mean value of 61.8 percent. There was only a small undegradable fraction (U) of 6.8 percent and a high degradation rate (c) of 15.0 percent/h. For the protein, mulberry leaves presented a smaller A fraction (17.7 percent) in relation to fraction B (79.3 percent), with a small undegradable fraction (U) of 3.2 percent, which indicates the importance of microbes in the degradation of the CP. In relation to the NDF, a large B fraction was observed (85.0 percent) with a reasonable fraction U (15.0 percent/hour) and a high fraction c (14.0 percent/h), indicating the large utilization potential of mulberry fibre.

For the estimation of the degradation potential of DM, CP and NDF, the results of the incubation for 48 hours were utilized, since the maximum degradation had been obtained by this time.

TABLE 1

Soluble (A), potentially degradable (B) and undegradable (U) and degradation rate (c) of dry matter (DM), crude protein (CP) and neutral detergent fibre (NDF) of the mulberry clones

Parameter	Clone	Fractions
		A (%)	B (%)	U (%)	c (%/h)
	Miura	34.0	59.4	6.8	0.16
DM	FM Shima Miura	29.3	64.0	6.8	0.13
	FM 86	31.0	62.0	7.0	0.16
	Miura	24.3	73.3	2.7	0.18
CP	FM Shima Miura	11.3	85.7	3.0	0.14
	FM 86	17.4	78.9	3.8	0.16
	Miura	0.0	86.8	13.2	0.17
NDF	FM Shima Miura	0.0	84.9	15.1	0.12
	FM 86	0.0	83.4	16.7	0.14

There were no differences (P >0.05) for PD and ED of the DM at the passage rates (kp) considered, but they were all high (Table 2). This can be explained by the fact that only leaves were used. There were no differences either among clones on CP (P >0.05). The values observed in this study were a little smaller than those found by Vasconcelos (1994), which obtained a value for PD of 96.7 percent and ED of 71.1 percent of DM for kp 4.4 percent, which could be explained by the lower "c" value found by this author. At the same time when the values of PD for DM and CP are compared with the published in vivo and the in vitro digestibility coefficients, it is clear that there is an overestimation of the in situ method. The PD values for NDF in this study are close to the ones found by Hara (1993) and Basaglia (1993).

TABLE 2

Potential (PD) and effective degradation (ED) of DM (DM), crude protein (CP) and neutral detergent fibre (NDF) of mulberry clones

Parameter	Clone	PD	ED
			kp 0.02	kp 0.05	kp 0.08
	Miura	93.3	86.4	85.8	85.4
DM	FM Shima Miura	97.2	84.0	77.6	76.9
	FM 86	86.7	85.8	71.6	70.8
	Miura	92.7	89.3	80.2	72.7
CP	FM Shima Miura	95.8	84.3	71.7	63.0
	FM 86	83.5	87.5	77.5	70.1
	Miura	93.0	76.8	65.7	57.5
NDF	FM Shima Miura	96.2	71.3	58.1	49.2
	FM 86	83.2	72.6	61.0	52.67

The NDF was not different (P >0.05) among clones, neither in PD and ED, values considered acceptable for the fibre fraction. This parameter did not have an A fraction, since it does not dissolve in water and depends exclusively on the microbes for its disappearance from the bags.

CONCLUSIONS

Considering the high values of the soluble and potentially degradable fractions, as well as the potential and effective degradation of leaves of the mulberry clones studied, it is confirmed that this feed shows a high nutritive value with large potential for feeding goats.

BIBLIOGRAPHY

Aguiar, R. S., Maldonado, H., Da Silva, J. F. C. et al. 1997. Degradabilidade in situ da matéria seca, da proteína bruta e da fibra em detergente neutro do capim-furachão (Panicum repens L.) em diferentes idades de corte. In Reunião Anual DA SBZ, 34, 1997, 67 pp. Juiz de Fora. Anais.

Basaglia, R. 1993. Eficiência de utilização da proteína da amoreira (Morus alba). Jaboticabal. Trabalho de Graduação (Graduação em Zootecnia) FCAV-UNESP. 45 p.

Orskov, E. R. 1988. In: Nutrición proteica de los ruminantes. Saragossa, Acribia.

Hara, C. H. 1993. Produção e digestibilidade in vitro da matéria seca e proteína bruta em cultivares de amoreira (Morus alba L.). Jaboticabal. 1993. Trabalho de Graduação (Graduação em Zootecnia). FCAV-UNESP. 43 pp.

Silva, D.J. 1981. Análise de alimentos. Viçosa, Imprensa Universitária, 166 pp.

Takahashi, R. 1998. Sericicultura: Amoreira (Morus alba L.) Bicho da Seda (Bombyx mori L.). Jaboticabal: FCAV UNESP, 135 p. (Apostila).

Vasconcelos, V. R. 1994. Degradação ruminal da amoreira (Morus alba L.) em caprinos. Jaboticabal. Dissertação (Mestrado em Zootecnia) - FCAV-UNESP. 86pp.