Effect of replacement of soybean with mulberry leaves in diets on performance of lactating cows

Pham Kim Cuong, Nguyen Thanh Trung, Vu Chi Cuong

National Institute of Animal Science,
Chem - Thuyphuong - Tuliem - Hanoi - Vietnam
trung0475@yahoo.com

Abstract

Four crossbred Holstein Frisian (75% HF blood, 553 to 578 kg) cows in mid actation (90d in milk) were used to determine the effect of replacement of dietary soybean meal with mulberry leaves on milk yield and quality. Cows were assigned to diets in a Latin square design with 2 week experimental periods. Diets were formulated to provide 4 concentrations of dietary substitution of soybean meal with mulberry leaves of  0, 33, 66, and 100% (crude protein basis). Dry matter intake decreased linearly by substituting mulberry for soybean meal but the rate of decline was quite low. .Replacing the mulberry for soybean meal in diets for dairy cows did not affect milk yield or quality. It is concluded that mulberry leaves may be used to replace soybean meal to decrease feed costs.

Key words: Crossover, Holstein crossbred, Latin square, milk composition, milk yield

Introduction

Natural grasses and agro-byproducts are major feed sources for ruminant production in the tropics, especially in the dry season (Koakhunthod et al 2001). These feedstuffs are often low in both protein and digestible energy, which results in a low intake and hence poor animal performance (Wanapat 1995). To overcome this constraint, foliages of some trees and shrubs whose protein content and digestibility are moderate to high, have been exploited (Egan 1997; Shayo 1998). Among these unconventional feed sources, mulberry (Morus spp.) appears to be an exceptional forage for the ruminant due to its high yield of biomass, high protein content of leaves and high DM digestibility as well as high palatability (Boschini 2002; Sanchez 2000; Shayor 2000; Yao et al 2000).

The use of mulberry leaves as a feed for ruminants has been investigated extensively in both beef and dairy cattle with excellent results (see Sanchez 2000). Olivedo (1995, cited by Benavides et al 2002), for example, reported similar milk yields in grazing dairy cows supplemented with either mulberry or commercial concentrate. Similarly, Benavides et al (2002) observed no difference in milk yield and quality among groups of grazing dairy cattle supplemented with either 100% concentrate, 60% concentrate 40% mulberry, or 25% concentrate 75% mulberry supplements.

In Vietnam, mulberry has been traditionally used for silk worms. The residue left over by the worms, however, is used for feeding animals. In recent years, workers from Hue University of Agriculture and Forestry and National Institute of Animal Science have investigated the nutritive value of mulberry as a ruminant feed (Vu Chi Cuong et al 2005; Nguyen Xuan Ba et al 2005). Nguyen Xuan Ba et al (2005) reported that mulberry foliage silage could be safely used as the sole feed for growing goats. Vu Chi Cuong et al (2005) used mulberry leaves to replace cottonseed so that fresh mulberry leaves accounted for 0, 5, 10, and 15% of dietary DM for finishing steers and concluded that inclusion of mulberry leaves in the diet improved growth rate and feed conversion rate.  With dairy cattle, there is a belief in the farmer community that mulberry would reduce milk formation and thus it is not fed to milking cows. This paper describes research aimed to disprove that belief.

Material and methods

Location and climate of the study area

The experiment was conducted on the Bavi Cattle and Forage Research Centre. The centre is located in the buffer zone between a mountainous area and the delta at E 105^o 25 longitude and N 21^o 06 latitude, with a mean altitude of 220 m above sea level. The climate is tropical monsoon with a wet season between April and November and a dry season from December to March. Average annual rainfall is 1850 mm.  

Experimental animals, feeds and management

Four cross bred Holstein Friesian milking cows (75% HF) were used. The cows were at around the third month of lactation with a milk yield of approximately 15 kg/day. Body weights ranged from 553 to 578 kg. The feeds used in the trial were elephant grass, alfalfa hay, dried sliced cassava roots, maize meal, soybean meal, mulberry leaves, molasses and mineral blocks. The diets offered to the cows during the experimental period were formulated so that the protein from soybean meal of the diet were substituted by that of mulberry leaves at 0, 33, 66, and 100%. The quantities of mulberry leaves needed for the experiment were collected from one harvest and dried before being ground through a 6 mm screen.

The concentrates were fed in equal portions just before milking in the morning and afternoon. After feeding concentrates, the cows were given elephant grass and alfalfa hay. Drinking water was available at all times. The cows were let out for exercise for 1 hour daily in the morning after milking. They were milked by hand twice daily at 05.00 in the morning and 16.00 in the afternoon.

Experimental design

The experiment was conducted using a single 4*4 Latin Square Design. The experiment was run for four consecutive periods of 28 days each. Each period consists of 14 days of adaptation and 14 days of data collection. The four experimental diets were formulated to have the same content of metabolisable energy (ME) and crude protein (CP).

Measurements, sampling and chemical analysis

Total milk yield was recorded and milk samples were analysed for fat, solids non-fat and protein using EKOMILK Ultrasonic Milk Analyzers (VEREA PLAST AD, Stara Zagora, Bulgaria). During the entire period of the experiment, daily samples of feeds offered and feed refusals were measured and were analysed for DM, ash and crude protein by AOAC (1990) procedures.  

Statistical analysis

DM intake, daily milk yield and milk composition data were analysed using Minitab Statistical Software (Minitab Version 14.12, 2004) using the GLM opruion in the ANOVA program. The model was:

     Y_ijk= m +T_i+P_j+A_k+e_ijk

where Y_ijk is the dependent variable, T_i is the effect of treatments, P_j is the effect of period, A_k is the effect of animal and e_ijk is the random error effect. 

Results and discussion

There was a linear decrease in DM intake when soybean was replaced with mulberry leaf meal (Table 1; Figure 1), although the degree of the decrease was relatively small. Intakes of ME and CP followed the same trend as for DM, as the diets were arranged to have similar concentrations of these components. . 

Figure 1. Relation between DM intake and replacement rate of soybean CP by mulberry CP

There were no differences in milk yield and quality due to replacement of soybean by mulberry leaf meal (Table 4). This agrees with the findings of Oviede (1995; cited by Benavides et al 2002) and Benavides et al (2002) in experiments with grazing cows, where mulberry leaves replaced commercial concentrates.

Conclusions

• In a short-term (Latin square design), replacing soybean meal with mulberry leaf meal did not affect milk yield or quality in Holstein-Friesian crossbred cows fed in confinement on elephant grass as the basal diet.
   

Acknowledgements

The authors gratefully acknowledge the support from the MEKARN project, financed by Sida, and the NIAS for facilitating the study at the Bavi Cattle and Forage Research Centre.

References

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