Shiroma, S. and F. Hongo. College of Agriculture, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-01, Japan.

RUMEN CHARACTERISTICS OF OKINAWAN MEAT GOATS FED LEU CAENA LEUCOCEPHALA SEED MEAL

Introduction. Although many works on leucaena feeding and degradation of mimosine in the rumen have been reported, few papers concerning the effect of leucaena feeding on the parameters such as pH, temperature, numbers of bacteria and protozoa, and volatile fatty acids (VFA) production have been published (Dominguez-Bello 1989). Being different from single- stomached animals, ruminants utilize these VFAs produced from ingredients of diets by rumen microorganisms for gluconeogenesis, fatty acid synthesis, ATP or energy production, and various other metabolisms. Therefore, it is important to elucidate the effect of leucaena material feeding on the parameters involved in the fermentation or VFA production as well as degradation of mimosine or DHPs in the rumen. The objective of this experiment was to investigate the effect of elevated amounts of leucaena seed (LS) meal on these parameters when fed to Okinawan meat goats.

Materials and methods. Four two-year-old Okinawan meat goats (Saanen x native) with rumen fistula and average body weight of 40 kg were used as experimental animals. The leucaena seed meal (LS), ground through 60 mesh screen and administered via rumen fistula, was combined with various proportions of green herbage (GH). The animals received: (1) 0% LS + 100% GH, consisting of paragrass (Brachiaria mutica), napiergrass (Pennisetum purpureum ), tachiawa sendangusa (Bidens pilosa Scherff) and noasagawo (Ipomea indica); (2) 15% LS + 85% GH;(3) 30% LS + 70% GH; and (4) 45% LS + 55% GH. Each ration, divided into two portions, was fed twice daily at 0900 and 1900 hours. Amount of feed was determined according to the NRC feeding standard.

Results and discussion. Rumen pH and temperature are influenced by ingestion of feed and water and their fermentation. The fluctuation patterns of these two criteria were in the ranges of normal values. Rumen pH values (Figure 1, a) were lowest 2 or 4 hours after feeding with gradual increment in due course of time. Goats feed 30% LS and 45% LS rations gave lower pH values compared to GH and 15% LS groups, suggesting higher fermentation rates and concentrate characteristics of LS meal. No statistical differences were observed in rumen temperature (Figure 1, b) among treatments.

Approximately 1010 to 1012 of bacteria per ml of contents inhabit the rumen and produce VFAs, as end products of digestion, which are equivalent to glucose in the single-stomached animals. They also synthesize B vitamins and furnish bacterial protein well balanced in amino acids, rendering inclusion of any specific amino acids in the diet of ruminants unnecessary. Goats on 45% LS showed highest viable rumen bacteria numbers at all sampling times except at feeding time, and those on 15% LS and 30% LS rations also gave similar numbers as those on GH. This was reflected in the fluctuation of pH and suggests that fermentation or production of VFAs by rumen microorganisms, especially by bacteria, is not inhibited by LS meal.

Total and individual VFA values, other than n-butyric, showed a tendency of increase as LS level in the ration was elevated (Figure 1, b and c). Molar proportion of acetic was reduced as LS level increased, with the exception of 15% LS (Table 1), while propionic ratio was increased, eventually resulting in lower acetic:propionic ratio, especially in 45% LS. Together with all other VFA production patterns and those of pH, this indicates concentrate characteristics of LS meal similar to other beans.

Table 1. Molar proportion of individual VFA in the rumen of Okinawan meat goats fed _________ different levels of leucaena seed._____________________________________________

Volatile fatty acid (M/100M) TotalDiet C2 C3 n-C4 Iso-C5 n-C5 C2/C3 -mM/dl-

0% LS 71.6 19.5” 5.6* 1.8 1.5 3 T 14.115% LS 70.2 20.3* 5.2C 2.9” 1.8b 3.5* 14.230% LS 68.5“ 20.5a 6.0b 3.3b 1.8b 3.4* 16.445% LS 66.? 20.8a 6.8a 3.r 2.1a 3.2b 19.8“

SE1 1.4 0.6 0.9 1.4 0.6 0.4 2.9

1 Standard error of mean. Angle = arcsin [(sq. rt.) percentage] was used for statistical analysis.a'b’c Means among diets with a common superscript are not statistically different (P .01).

The number of cilliate protozoa is about 10s to 106 per ml of rumen contents. The roles of protozoa in the nutrition of ruminants are considered (Ogimoto and Imai 1981): to provide nutrients, especially protein better balanced in amino acids than that of bacteria, to slow down bacterial starch digestion by engulfing them, and to digest cellulose and produce VFAs (some large cilliates). Numbers of total protozoa were higher in 30% LS and 45% LS than 15% LS and 0% LS or GH groups. Numbers of Holotrichia, which is reported to be an active fermenter of soluble sugars such as glucose, fructose, and sucrose (Abe et al. 1981), were also higher in LS-fed animals compared to those found in 0% LS ration group, indicating abilities to adapt themselves or probably to utilize mimosine, 2,3 or 3,4 DHPs (Figure 1, d and e). In the genus of Spriotrichia, S. entodinium with no tail and S. epidinium with tail increased their numbers as LS level was raised (Figure 1, e). All these results about rumen parameters in this study support the finding (Shiroma and Akashi 1976) that fractions of rumen bacteria and protozoa obtained from Okinawan meat goats are able to degrade mimosine.

Summary. It is suggested that LSM can be used safely as a concentrate in the rations of Okinawan meat goats. This conclusion is based on increased numbers of live rumen bacteria and most protozoa, and VFA production. No abnormalities occurred in rumen pH, temperature, and health of the animals when dry matter of green herbage was replaced by leucaena seed meal as high as 45%.

References:

Abe, M., T. Iriki, N. Tobe and H. Shibui. 1981. Sequestration of holotrich protozoa in the reticulo-rumen of cattle. Appl Environ. Microbiol. 41:758.

Dominguez-Bello, M.G. 1989. Microbial ecophysiology in the rumen of sheep fed tropical forages. Leucaena Res. Reports 10:94.

Ogimoto, K. and S. Imai. 1981. Atlas of rumen microbiology. 9 Japan Scientific Societies Press, Tokyo.

Shiroma, S., and A. Akashi. 1976. Degradation of mimosine in Leucaena leucocephala de Wit by goat rumen microorganisms. Jap. J. Zootechnical Science 47(12):739.

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Figure 1. Effect of leucaena seed levels on rumen parameters of Okinawan meat goats, (a) pH; (b) temperature, total VFA, acetic and propionic; (c) n-butyric, n-valeric and iso-valeric; (d) total protozoa, Holotrichia and Spirotrichia; (e) entodinium having tail or not having tail, epidimum having or not having tail, dasytricha and isotricha. Values of X axes are hours after feeding.