Feed intake, digestibility and N balance of goats fed Paper mulberry (Broussonetia papyrifera) or Muntingia (Muntingia calabura) foliages supplemented with NPN from potassium nitrate or urea

Phonevilay Silivong, T R Preston* and Ngo Van Man**

Souphanouvong University, Lao PDR
silipvl@yahoo.co.th
* Finca Ecologica, TOSOLY, UTA (Colombia) AA#48, Socorro, Santander, Colombia
** Department of Animal Physiology and Biochemistry, Nong Lam University,
Ho Chi Minh City, Vietnam

Abstract

Four weaned female goats, with an initial body weight of 10 ± 0.5 kg and 4-5 months of age, were assigned to 4 treatments on a 2*2 factorial design in a 4*4 Latin square. The treatments were: foliages of Paper mulberry or Muntingia and potassium nitrate or urea as the source of NPN.  

DM intake was higher for Paper mulberry than Muntingia but was not affected by NPN source. Coefficients of apparent digestibility of OM and crude protein, and N retention, were higher for Paper mulberry than Muntingia but were not affected by NPN source. N retention as percent of N digested did not differ between the two foliages, implying that digestibility of the crude protein, rather than its biological value, was the reason for the superiority of the Paper mulberry as a feed for goats. 

Key words: Biological value, N retention, protein, trees

Introduction

Livestock production plays an important role for the livelihood of farmers in rural areas in developing countries and this is also the case in Lao PDR. The main part of the cash income and the protein consumption in the households comes from livestock, and livestock can also provide organic fertilizer for crop production. Farmers in the lowland and upland areas keep many animal species such as cattle, buffaloes, goats, pigs and poultry (Phengsavanh 2003; Xaypha 2005). Ruminants provide a large part of the cash income for smallholder farmers and can also be used for draught power. The production of meat and milk from ruminants is generally based on traditional management methods using free range grazing systems.

Goats produce of meat, milk, skins and fiber for sale or family consumption. They have an ability to survive on low quality feeds or in difficult conditions on relatively small amounts of feed and they also have a higher reproduction rate compared to cattle (Steel 1996), with 1.4 to 1.9 litter per year and 1.7 to 1.9 kids per litter (Xaypha 2005). Goat production can be found everywhere in Laos at present, but the number of animals per household is small and the breeds used are local breeds with small body size, low growth rates and poor productivity (Phimphachanhvongsod 2001).

According to Simbaya (2002) and Phengsavanh (2003) the major feed resources for the ruminants in Laos are native grasses, legumes and fodder tree leaves that are available around the farms and in the forest. These feeds generally have a high content of fiber and low content of protein, minerals and vitamins. Many researchers have found that foliages from fruit trees and other trees, legumes and some crops are important protein sources, with high intake and digestibility and offering them as feeds results in good growth performance in goats (Daovy et al 2009; Phengvichith and Preston 2011; Kounnavongsa et al 2010). In almost all provinces in Lao PDR, the main constraints to ruminant production are diseases and lack of feed, especially in the dry season (ADB 2001; Phengsavanh 2003; Phimphachanhvongsod et al 2004; Xaypha 2005).

Paper mulberry (Broussonetia papyrifera) is a tree that is common in the northern area of  Laos growing to 15 meters (tall). The leaves of Paper mulberry have crude protein content of 19.7% in DM according to Sangkhom and Preston et al (2009). The leaves could be a potential feed resource for goats. Presently the bark of Paper mulberry is used in the handicraft industry to make paper and envelopes. The leaves would be a by-product from this process. Some farmers said the leaves can be used to feed to pigs. It is reported that the twigs and young leaves are consumed by deer  (http://en.wikipedia.org/wiki/Paper_Mulberry), so it should be palatable to goats also.

Muntingia calabura belonging to the family Elaeocarpacae grows everywhere (sandy land, humid areas, and high land area) and is well adapted to the dry season in Lao PDR. The farmers use it as shade tree around the homestead, and along the roadside. It is a tall tree with a large canopy of leaves but it is not normally fed to animals (Nguyen Xuan Ba et al 2003). Very little is known about the nutritive value of foliage from Muntingia for ruminant species. Pok Samkol (2003) reported that the foliage was palatable to goats; and that DM intake was higher when the foliage was offered hanging in the feed trough (33.5 g/kg LW) compared with giving the leaves alone (26.9 g/kg LW).

In an in vitro study (Phonevilay Silivong et al 2012), it was shown that gas production and methane produced per unit substrate solubilized was the same when leaves from Paper mulberry or Muntingia were the major sources of protein, and that with both foliages supplementation with potassium nitrate reduced methane production compared with urea as NPN source.

The hypothesis to be tested was:

• Feed intake, digestibility and N balance of goats fed Paper mulberry (Broussonetia papyrifera) or Muntingia (Muntingia calabura) foliages will be increased when the foliages are supplemented with potassium nitrate rather than urea

Material and methods

Location and duration

The experiment was carried out at the Animal Science farm of  Souphanouvong University, which is located about 7.5 km from Luang Prabang district, Laos at an altitude of 1.000 m above sea level. The experiment was conducted from April to June 2011.

Treatments and experimental and design 

Four growing goats were used to compare four treatments arranged in a 2*2 factorial design within a 4*4 Latin square with 10 days per period: 5 days for adaptation and 5 days for collection of feed refusals, feces and urine.  

The factors were:

Source of NPN:

• Urea (U) or potassium nitrate (KN)

Source of foliage:

• Paper mulberry (PM) or Muntingia (MG)

Individual treatments (Table 1) were: 

• MG-U:  Urea (1.83% of diet DM) + Muntingia

• PM-U: Urea (1.83% of diet DM) + Paper mulberry

• MG-KN:  Potassium nitrate (6% of diet DM) + Muntingia

• KN-PM: Potassium nitrate (6% of diet DM) + Paper mulberry

Animals and housing  

Four female weaned goats (local breed) with initial live-weight of 10 ± 0.5 kg and 4-5 months of age were used. These animals were purchased from farmers around the Luang Prabang district.  They were housed individually in metabolism cages made from bamboo (dimensions of width 0.8 m, length 0.9 m and height 0.9 m) and designed to collect separately feces and urine (Photo 1). The goats were vaccinated against Pasteurellosis and foot and mouth disease and treated with Ivermectin (1ml/33 kg live weight) to control internal and external parasites. They were gradually introduced to the cages and diets over 7 days before beginning the experiment.

Feeding and management 

Molasses diluted to a Brix (content of sugars) of 40 was used as the carrier for the NPN sources. The diluted molasses was fed in a plastic bucket and hung above the feed trough and was given ad libitum. The Muntingia and Paper mulberry foliages (Photo 2 and Photo 3) were collected daily from natural stands in the University campus and were fed at 3% of live weight on DM basis. They were hung in bunches above the feed trough. Feeds offered and residues were weighed every morning. 

Measurements 

Live weight was recorded in the morning before feeding at the beginning and at the end of each period. Feeds offered and refusals were collected daily during the 5 days of the collection period. Urine was collected in buckets with 20 ml of a solution of sulphuric acid (10% sulphuric acid concentrate + 90% distilled water). Feces were collected daily and stored at -18ºC and at the end of each period, sub-samples were mixed together and ground with a coffee grinder.

Chemical analyses 

The sub-samples of feed offered, refused and of feces were analysed for DM, N and ash according to AOAC (1990) methods. Urine was analysed for nitrogen by AOAC (1990) procedure.  

Statistical analyses 

The data were analyzed by the General Linear Model option in the ANOVA program of the Minitab (2000). Sources of variation in the model were: goats, treatments, periods, NPN source, foliage source and error.  

Results and discussion

Leaves and stems were higher in crude protein and lower in DM in Paper mulberry than in Muntingia (Table 2). Compared to other published data, the DM and crude protein of Muntingia in the leaves and stem were higher than the value (33.3% and 34.8% DM and 13% and 5% CP in DM) reported by Sitone et al (2011). DM and crude protein levels of Paper mulberry leaves and stems were higher than the values (28.4% and 17.7% for DM and 16% and 8.4% for CP) reported by Sangkhom and Preston et al (2009).

Intakes of Paper mulberry and Muntingia foliages were not affected by NPN as potassium nitrate or urea. Total DM intake as g/kg LW was higher when nitrate rather than urea was the NPN source (Table 3). The foliages represented 60-70% of the total DM intake (Figure 1).

Apparent coefficients of digestibility of OM and crude protein were higher for Paper mulberry than Muntingia, but there was no difference in DM digestibility (Table 4). Digestibility coefficients did not differ between the two sources of NPN.  Daily N retention and N retention as percent of N intake were higher for Paper mulberry than Muntingia but  there was no difference for N retained as percent of N digested (Table 4). Daily N retention and N retention as percent of N intake did not differ between sources of NPN but N retention as percent of N digested was higher for potassium nitrate than urea.

The higher ash content of the Paper mulberry compared with Muntingia would seem to explain the lack of difference between the foliages in apparent DM digestibility and the higher value for the former when the criterion was the apparent digestibility of the OM. The differences between the two foliages in daily N retention and N retention as percent of N intake, in favour of Paper mulberry, appears to be the result of the higher crude protein digestibility in this foliage. When N retention was expressed as percent of N digested there were no differences between the two foliages, implying that the biological value of the protein was the same in both.  

Conclusions

• DM intake as g/kg LW, and coefficients of apparent digestibility of OM and crude protein of goats fed Paper mulberry were higher than those of goats fed Muntingia but were not affected by NPN source
  
  
• Daily N retention and N retention as percent of N intake of goats fed Paper mulberry were higher than these of goats fed Muntingia; however, N retention as percent of N digested between the two foliages was similar. It seems that Paper mulberry has overall superior nutritive value because of higher OM digestibility and higher crude protein content.

Acknowledgements

This research was done by the senior author with support from SIDA MEKARN program as part of the requirements for the MSc degree in Animal Production "Specialized in Response to Climate Change and Depletion of Non-renewable Resources". The authors acknowledge support for this research from the MEKARN project financed by Sida. Special thanks to Mr Thongxay who provided valuable help in the farm. We also thank the staff of the Department of Animal Science, Faculty of Agriculture and Forest Resource, Souphanouvong University for providing the facilities to carry out this research. 

References

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Received 25 February 2012; Accepted 7 March 2012; Published 7 May 2012

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