Effect of cassava hay supplementation on milk production in lactating goats

Ngo Tien Dung*, Dinh Van Binh, Nguyen Thi Mui and T R Preston**

Goat and Rabbit Research Center, Sontay, Hatay, Vietnam, National Institute of Animal Science, Hanoi, Vietnam
* Present address: THmilk Joint Stock Company, 4th Floor, Bac A Building, No 9 Dao Duy Anh, Dong Da Dist, Hanoi, Vietnam
dzungvbdp@gmail.com
** TOSOLY, AA48 Socorro, Colombia

Abstract

Twenty-four lactating goats (F1 of Bachthao*Jamnapary or Barbary) were used to investigate supplementation with cassava foliage hay (Manihot esculenta Crantz) of a low-protein based on rice straw sprayed with urea, a molasses urea block (MUB) and dried cassava root. The treatments were offer levels of  0, 100, 200, 300, 400 and 500 g dry matter (DM) of cassava hay. with corresponding reduction in the offer level of the urea-rice straw. 

The milk yields increased linearly from 880 to 1532 ml/day as cassava hay was increased from zero to 25%  of the diet DM. Milk quality was improved slightly and growth rates of kids suckled for restricted periods after milking were increased.

Keywords: Cassava root, feed intake, growth, kids, MUB, rice straw, urea

Introduction

Cassava or tapioca (Manihot esculenta, Crantz) is a highly productive tropical crop. Besides the root yield,  each hectare of cassava can produce a large amount of leaves. The potential yields of cassava leaves as by-products at root harvesting may amount to as much as 4.64 tonnes dry matter (DM) per hectare and fresh cassava forage (Ravindran and Rajaguru 1988). Ffoulkes and Preston (1978) showed that fresh cassava foliage as the sole source of fibre and protein in a diet of liquid molasses and urea (3% urea) supported growth rates of almost 900 g/day and there was no advantage in providing additional soybean meal. Cassava foliage has been made into cassava hay which  proved to be an excellent feed either as the sole diet or as a supplement in diets based on crop residues (eg. urea-treated straws/sugarcane tops) (Wanapat et al 1997). Cassava leaves are known to contain variable levels of condensed tannins (0.26% in DM, Wanapat et 2000;  3.2% in DM, Netpana et al 2001; 3.2% in DM, Bui Phan Thu Hang and Ledin 2005).  Condensed tannins at moderate levels are known to have positive effects on the nutritive value of the feed by forming insoluble complexes with dietary protein, resulting in "escape" of the protein from the rumen fermentation (Barry and McNabb 1999). A five-fold increase in N retention of goats fed ammoniated rice straw (by ensiling with urea) to intake of fresh cassava leaves at 1% of live weight (DM basis) was reported by Ho Quang Do et al (2002).

The objective of the present study was to determine the response in milk yield of goats to increasing levels of cassava hay as a source of protein in diets based on rice straw sprayed with urea, a molasses-urea block and dried cassava root.
 

Materials and methods

Location

The study was conducted at the Goat and Rabbit Research Centre, Sontay, Hatay, Vietnam.

Treatments and design

Twenty-four lactating goats, F1 crosses between Bach Thao and Barbary or Jumnapary, with initial weights between 30 and 35 kg, were housed in individual pens with raised slatted floors, and allocated to six treatments consisting of levels of cassava hay of 0, 100, 200, 300, 400 or 500 g DM/day, replacing urea-sprayed rice straw.   The other components of the diet were rice straw spayed with urea, a molasses-urea block (MUB) and dried cassava root. of urea-sprayed rice straw.

Feeding and management

The cassava hay was made from cassava foliage (leaves, petioles and fine green stems) of a local variety harvested at an average age of 56 days. The foliage was chopped into small pieces mechanically (1 to 2 cm) and dried in the sun.  Rice straw was chopped and sprayed with urea (XX% DM basis) before feeding. The amounts offered of the cassava hay and rice straw were 115 and 130%, respectively of the planned amounts. In addition, all the goats received daily 125 g MUB (45% rice bran, 40% molasses, 6% urea, 3% lime, 4% minerals and 2% salt) and 600 g fresh cassava root. A mineral block with a composition of 70% Ca₃(PO₄)₂, 15% NaCl and 15% cement as a binding agent was supplied to each pen. The feeds were offered in separate feed troughs. The animals had free access to fresh water.

The goats were hand-milked twice daily 07.00 h and 17.00 h followed by restricted suckling of the kids for 1 hour after each milking. The milk yield was estimated as the milk obtained by hand milking plus the quantity consumed by the kids (determined by weighing before and after suckling). The experimental period started at the 5th week of lactation and finished after the 12th week, a total of 8 weeks.

Feeds offered and feed refusals were analyzed by standard methods (AOAC 1990). Condensed tannins were determined by the Vanillin-HCl method (Burns 1971) and HCN by the method of Ikediobi et al. (1980). The data from the experiment were analysed as a Completely Randomised Design using the General Linear Model option of the MINITAB software (Minitab 2000).  Observed trends in responses to the cassava hay were described by fitting regression equations using the Minitab software.
 

Results and discussion

 Spraying 5% ureaon the straw appeared to be effective in raising the fermentable N to an appropriate level (Table 1). The condensed tannins in the cassava hay were at the low end of the range considered to be appropriate for the formation of complexes with protein (Barry and McNabb 1999).

The rice straw sprayed with urea was not consumed completely, being from 43 to 52% of the amount offered (Table 2).

Increasing the level of cassava hay in the diet led to increases in total DM intake up to the level of 22% of the diet DM as cassava hay. At offer levels of 400 and 500 g/day of  cassava hay, the intake of cassava hay was considerably lower than planned. Thus the response of DM intake to the proportion of the diet as cassava hay was curvilinear (Figure 1) with the maximum intake at between 0.2 and 0.25 of the DM intake as cassava hay.

Figure 1.  Relationship between DM and proportion of diet DM as cassava hay in lactating goats fed a basal diet of urea- sprayed rice straw, a molasses block and cassava root	Figure 2.  Relationship between milk yield and proportion of diet DM as cassava hay in goats fed a basal diet of urea-sprayed rice straw, a molasses block and cassava root

By contrast, milk yield was linearly related with cassava hay intake, being almost double when cassava was consumed at 25% of DM intake compared with the zero level of cassava hay (Table 3 and Figure 2). Milk quality was also improved with cassava hay supplementation (Table 3).

Figure 3. Relationship between  rate of loss of live weight of the does and the proportion of diet DM as cassava hay	Figure 4. Relationship between  rate of live weight gain of the kids and the proportion of diet DM as cassava hay in the diet of the does

The beneficial effects on milk production and milk quality, and on the live weight changes of the does and the kids,  mirror the responses in growth rate when cassava foliage has been used to supplement ruminant diets low in true protein (eg: in cattle, Ffoulkes and Preston 1978, Wanapat et al 1997, Keo Sath et al 2008, Ho Tham et al 2008, Sypraseuth Khonglalien et al 2008; and in goats, Ho Quang Do et al 2002).  It would appear that the presence of low levels of condensed tannins act to protect the proteins in the cassava leaves from being fermented in the rumen, thus conferring "bypass protein" characteristics to this forage and in so doing enhancing its value as a supplement in ruminant diets low in true protein (Preston and Leng 2009).
 

Conclusions

• Cassava hay at 25% of the diet DM increased milk production by 70% (from 900 to 1500 ml/day) in goats fed a basal diet of urea-sprayed rice straw, dried cassava root and a molasses-urea block.
  
  
• There were associated improvements in milk quality and better growth rates in kids reared in a restricted suckling system.

Acknowledgments

The authors wish to thank the MEKARN project, financed by Sida/SAREC, for supporting this research.

References

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Received 30 December 2009; Accepted 14 February 2010; Published 1 March 2010

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