Supplementing Napier grass (P. purpureum) with Flemingia foliage (F. macrophylla) and rice bran improves mineral status and growth performance of goats

T Fujihara^{1, 2}, M Hayashida³, E M Cruz⁴ and E A Orden⁴

¹ Faculty of Life and Environmental Science, Shimane University, Matsue City, Japan
tfuji1943@yahoo.co.jp
² Philippine Carabao Center, Science City of Munoz, Nueva Ecija, the Philippines
³ Department of Bioproduction Technology, Junior College of Tokyo University of Agriculture, Setagaya-ku, Tokyo, Japan
⁴Small Ruminant Center, Luzon State University, Science City of Munoz, Nueva Ecija, the Philippines

Abstract

Sixteen (3-4 month-old) upgraded goats (25% Native X 75% Anglo-Nubian) with average weight of 10kg were used to determine the effects of two levels of rice bran (RB) on the body weight, dry matter (DM) digestbility and plasma mineral concentrations of goats fed with Napier grass (Pennisetum purpureum) alone or with Flemingia foliage (Flemingia macrophylla). The treatments in a Randomized Complete Block Design were: NG, 100% Napier grass; NG-FM, 70% Napier grass + 30% Flemingia foliage; RB10,  60% Napier grass + 30% Flemingia + 10% rice bran; RB20, 50% Napier grass + 30% Flemingia + 20% rice bran. Voluntary feed intake, body weight change, dry matter (DM) digestibility, blood and plasma mineral concentrations were determined.

The macro- and micro-mineral contents of the diet were mostly within the range recommended for growing goats except for Zn in NG and RB, and Se in FM and RB. Rice bran supplementation resulted in higher DM intake and digestibility and better weight gains of the goats after 120 day feeding period. The inclusion of 10 or 20% RB did not improve the mineral status of the animals although P, Mg, Fe and Cu in blood of goats were above the critical level.  The Se level in whole blood of goats was the most variable in response to changes in the amount of dietary Se intake. 

Key words: forages, plasma, Philippines, smallholder

Introduction

In the Philippines, goats are raised mainly by small-holder farmers. Feeding is mainly  with roughages, such as rice straw and/or natural grasses on the road side. Concentrate supplements are rarely given other than locally available rice bran (PCARRD 1985). Roughages in the tropics are generally low in protein, and also in minerals,  the levels of which vary markedly in the wet and dry season (McDowell 1985; Minson 1990). Feeding roughages with low protein and mineral content is one of the factors that influence animal productivity, and mortality of kids and young goats in the Philippines (Kanai et al 1987; Fujihara et al 1992a,b).  Supplementation with legume-tree leaves is an appropriate way to overcome these problems (Norton 1998). It has been previously reported that tree legumes and multipurpose tree species (MPTS) are good sources of crude protein (CP), readily degradable organic matter and essential minerals for goats in the farming villages of Central and Northern Luzon, in the  Philippines (Hayashida et al 2004, 2007; Orden et al 2005). Aside from Leaucaena leucocephala and Gliricidia sepium, another MPTS as a promising source of CP is Flemingia (F. macrophylla). However, it has been pointed out that the major limiting factor in the utilization of Flemingia as feed for goats is its fibrous characteristics that reduces its digestibility when used as feed for stall-fed growing goats (Orden et al 2005).

In the present study, nutrient digestibility, growth performance and blood mineral concentration of goats fed Napier grass (P. purpurium) and Flemingia were determined when fed as the sole diet or with supplementation of rice bran. The results obtained in this study were partly presented by Fujihara et al (2008).

Materials and methods

Location

The study was conducted at the Small Ruminant Center (SRC) of Central Luzon State University, Science City of Munoz, Nueva Ecija, Philippines, for 120 days (between September, 2006 and January, 2007),. The experimental site is located at 15°N, 121°E and the agro-climatic condition are classified as tropical monsoon type, consisting of two typical seasons: dry (December to May) and wet (June to November) with mean annual temperature of 28ºC and average rainfall of 1,900 mm, most of which falls during the wet season.

Experimental design, animals and feeding  

Sixteen 3-4-month-old upgraded female goats (25% Native X 75% Anglo-Nubian), housed in individual pens, were allocated to the following treatments in a Randomized Complete Block Design:

NG, 100% Napier grass (P. purpureum):

NG-FM, 70% Napier grass + 30% Flemingia foliage (Flemingia macrophylla);

RB10,  60% Napier grass + 30% Flemingia + 10% rice bran;

RB20, 50% Napier grass + 30% Flemingia + 20% rice bran.

The relative proportions of each dietary constituent were on DM basis. Each diet was offered at 3% of body weight as DM. The forage components were chopped and offered to the animals in equal proportions in the morning (08:00) and afternoon (16:00). Rice bran was fed in the morning prior to the feeding of Napier and Flemingia. Fresh water was made available at all the times.  A vermicide drench (Albendazole) was appplied to all goats before starting the experiment. At the middle of the feeding trial, a 7-day digestion trial was conducted,  when fecal excretion was individually collected to determine DM digesibility.

Sampling of feed, excreta and blood

Samples of feed offered and refused, and of feces were collected, dried (60～70 ^oC for 48 h) ground to pass through 2mm mesh screen using Wiley mill and stored in a refrigerator for chemical analysis. Bi-weekly blood samples (about 10ml) were collected from the jugular using heparinized syringe during the course of the feeding trial. From the 10ml blood sample, 1ml whole blood was taken and transferred to 10ml capacity test tube and dried before Se assay while the remaining blood samples were centrifuged at 1600 g for 20 minutes (4 ^oC) to separate plasma from courpo cells. Thereafter, 1ml of plasma was taken and placed in an acid-washed test tube, dried and stored before macro and micro mineral analysis. All the 1ml whole blood and plasma samples were dried at 150 ^oC for about 6 hours. Dried samples were sealed and stored at -20ºC until analysis.

Analytical methods

Measurement of DM in the feed and feces was done according to the AOAC procedure (Hoitz 1960). Prior to mineral analysis, all plasma and whole blood samples were subjected to wet ashing with nitric and perchloric acid (3:1 v/v). Selenium contents of the feeds and whole blood were determined by the fluorometric method of Watkinson (1966). Other macro and micro minerals were analyzed using Inductively Coupled Plasma Emission Spectrometer (ICPS-2000, Shimadzu, Kyoto, Japan). All the glassware used during the mineral analysis were soap and acid washed with nitric acid to avoid any contamination.

The data were subjected to ANOVA (Yoshida 1975) using the SAS computer program (Statview 1999).

Results and discussion

Diet ingredients

The high crude protein content in Flemingia is offset by the levels of NDF and ADF which are similar to those in Napier grass. The rice bran was of high quality as reflected in the content of ether extract, indicating litttle or no contamination with rice husk.

Mineral content in the feeds

The Ca content in Napier grass was within the range (2.1-5.2g/kg DM) recommended by McDowell (1985). In contrast, the Ca supply from Flemingia was two-times more than the higher limit of the requirement while RB appeared to be lacking in Ca. Except for the excessive amount of Mg (15.8g/kgDM) from RB, all the feeds provided sufficient amounts of P and Mg relative to the recommended levels (McDowell 1985).

The Fe content in Napier grass, Flemingia and RB were from 1 to 5 times higher than the recommended values of 30-100 mg/kg DM) (McDowell 1985). The value for Napier grass was slightly higher than the maximum tolerable level (50 0mg/kgDM) suggested by NRC (1980), probably arising from soil contamination. All of the feeds had Cu levels higher than recommended values.  Zinc appeared to be deficient as the concentrations inNapier, Flemingia and RB were extremely low compared to the required level. Likewise, the Se in Flemingia and RB was inadequate to meet the daily requirement of growing goats. However, the Se in Napier appeared to be sufficient compared to the critical lower level of 50 µg/kg  DM. 

Macro-mineral concentrations in plasma

Plasma Ca concentrations on all diets (Table 2) were above the the critical value of 70g Ca/L (McDowell 1985). Effects of diet on P concntrations were similar, with values on all diets superior to the critical level of 40 g/ recommended by McDowell (1985). This result is consistent with the earlier findings of Hayashida et al (2004) that minimal supplementation of growing Anglo Nubian crosses with concentrate was reflected in improved mineral status.

Plasma Mg concentrations were above 18mg Mg/L of blood considered as the critical level (McDowell 1985). These findings indicate that basal diets of Napier grass,  with or wthout Flemingia , provide enough Mg for growing goats and that additional supplementation with rice bran may not be needed, as originally proposed by Hayashida et al (2004). 

Micro-mineral concentrations in plasma

Plasma Cu concentrations were above the critical level of 0.6mg/L (McDowell 1985) in all the dietary treatments. The effect of RB supplementation on Zn values were inconsistent with higher values for 10% RB supplemention but not on 20% RB. All values were above the levels of 1.0mg/L recommended by McDowell (1985).  Moreover, there was no clinical manifestation of effect of Zn deficiency. The Se levels in whole blood of goats fed NB and NB-FM diets were below the critical level of 20μg Se/L proposed by McDowell (1985), due apparently to the low Se content of these diets. However, no clinical deficiency symptoms were observed among the experimental animals.  Moreover, the higher offer level of Se in the rice bran was not reflected in higher Se values in blood. 

Dry matter digestibility and growth performance

Addition of RB to the NG and NG-FM diets increased by 10% the apparent DM digestibility but there were no differences between the NG and NG-FM diets (Table 4). Previous data showed that from a group of  8 MPTS evaluated at the SRC, Flemingia had the lowest in-situ rumen degradability (Orden et al 2005).

The increase in DM digestibility with rice bran supplementation was reflected in increased growth rates but the effect was not linear as 20% rice bran was no better than the 10% level. The benefits of adding rice polishings to a roughage diet, apparently adequate in fermentable nitrgen in the form of urea, was attributed to the presence of the oil protecting the protein from rumen fermentation and heance facilitating its escape for enzymic digestion in the lower gut (Preston et al 1976).

Conclusion and implications

• The increase in diet digestibility and live animal growth rate from rice bran supplementation of diets based on Napier grass were not mirrowed by changes in mineral status which, with the possible exception of Se, were above critical levels even on the NG and NG-FM diets.
  
  
• There were no apparent benefits from adding foliage of Flemingia macrophylla to a basal diet of Napier grass.

Acknowledgements

The authors are very grateful to Ms T Mita, Dr M E M Orden and Mr A S.Galamgam for their cooperation during the course of the experiment.

References

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Received 25 November 2014; Accepted 26 December 2014; Published 1 January 2015

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