Effect of replacing concentrate by molasses urea blocks (mub) and Acacia mangium leaves for crossbred milking cows fed grasses of low nutritive value

An Xuan Bui and Hieu Trong Luu

University of Agriculture and Forestry, Ho Chi Minh City, Vietnam

Summary

Eighteen crossbred Holstein x Sindhi dairy cows in early lactation were fed a basal diet of grasses of low nutritive value ad libitum and 2 kg/d of cottonseed cake. The following supplements were compared:

C: 560 g concentrate/kg milk (Control).
MUB: Molasses-urea block (10% urea) ad libitum and 200 g of rice bran/kg milk.
AmMUB: Acacia mangium fresh leaves (1.5 kg/100 kg LWt), MUB ad libitum and 100 g rice bran/kg milk.

Milk yield during the first 26 days when cows were fed the control diet was used as covariant to correct the experimental yield measured during the next 30 days.

There were no significant differences (P>0.05 ) between average (corrected) milk yields for the three treatments (9.9, 9.8, 9.0 kg/d for C, MUB and AmMUB, respectively).

KEY WORDS: Crossbred dairy cattle, molasses-urea blocks, Acacia mangium, milk yield, rice bran

Introduction

In Vietnam as in most tropical developing countries, the major constraints to higher and more economical milk yields are: (i) the imbalance of nutrients in the basal diets (tropical grasses, sugar cane tops and/or rice straw) and (ii) the high price and scarcity of conventional cereal-based concentrate supplements.

Multinutrient blocks based on molasses and urea were introduced on private and state farms in Vietnam by Bui et al (1991) to improve the nutrient status of the traditional diet of grasses, sugar cane tops and rice straw supplemented with cereal byproducts and protein meals. Milk yield was increased both on the commercial farms and on the State Farm when the urea-molasses blocks were fed. The response was approximately 1 kg of milk per kg of MUB.

Legume trees are increasingly important components of farming systems in the tropics (Preston and Murgueitio 1989; AttahKrah 1991). In Latinamerica, Gliricidia sepium (Gomez et al 1992) and Erythrina poeppigiana (Esnaola and Rios 1990) have been used successfully to replace protein-rich oilseed meals in the diets of milking goats.

In Vietnam, the legume tree Acacia mangium is being grown extensively as a component of reforestation programmes. It is quick growing and valued as a source of lumber and fuel wood (Man et al 1993). Less is known about the nutritive value of the foliage. Early work by Bui et al (1992a) indicated that the rumen degradability of the dry matter and the protein in Acacia mangium leaves was low (<30% in 48hr) but could be improved substantially by pre-treatment involving ensiling with acetic acid for 7 days. Preliminary observations indicated that the fresh leaves were not well accepted by growing crossbred Sinhi x Holstein heifers but that intake increased when the leaves were wilted for 24hr prior to feeding (Bui et al 1992b).

Materials and methods

The experiment was carried out at An Phuoc state Farm in the dry season. Eighteen 18 Holstein x Sindhi, crossbred dairy cows giving an average of 10 litres/d milk between 30 and 70 days post calving, were allocated to 3 homogenenous groups according to milk yield. The milk yield during the last 26 days of the pre-experimental period was used as covariant to adjust the yields during the experiment.

The control diet was the same feeding system used at the farm. The basal diet consistd of native grasses (mainly Guinea grass) and 2 kg cottonseed cake/d.

The experimental treatments were:

C: 560 g concentrate/kg milk.
MUB: MUB ad libitum + 200 g rice bran/kg milk.
AmMUB: Acacia mangium leaves (fresh) at 1.5 kg/100 kg LWt + MUB ad libitum + 100 g rice bran/kg milk.

The milk yield during the experimental period was adjusted using the yield during the pre-experiment period as covariate. Milking was twice daily.

Table 1: Experimental design
		Treatments
Period	Days	C	MUB	AmMUB
Pre-experiment	1 - 26	C	C	C
Adaptation	27 - 33	C	MUB	AmMUB
Experiment	34 - 64	C	MUB	AmMUB

Table 2. Details of the experimental cows
	C	MUB	AmMUB
Number of cows	6	6	6
Age (years)	9.5±2.2	9±2.3	10±2.1
Liveweight (kg)	368±39	380±19	400±18

Table 3. Chemial composition of feeds
		% of drty matter
Feeds	DM	N x 6.25	CF	EE	Ash	NFE
Guinea grass	35	5.8	40.3	2.5	4.0	47.3
Cottonseed cake	90	26.6	24.0	7.6	6.2	35.6
Concentrate	87	14.1	12.1	7.3	13.0	53.4
Rice bran	89	11.6	19.0	10.6	13.8	45.0
Molasses-urea Block	80	33.2	7.6	4.0	23.6	31.6

Table 4: Composition of molasses-ureal block
Ingredient	%
"A" molasses	35
Urea	10
Rice bran	40
Salt	5
Quick lime	10

Results and discussion

The data for feed intake and milk production are in Tables 5 and 6.

There were no apparent differences in milk yield due to treatment. However, from the point of view of making greater use of local feed resources, the yields of the cows fed MUB and rice bran or MUB + Acacia mangium leaves + rice bran were achieved more efficiently and more economically than yields of cows fed the traditional "concentrate".

Conclusion

The results of this experiment are especially relevant for developiung strategies for feeding during the dry season when quantity and quality of grass is low in most tropical regions. The Acacia mangium tree maintains active growth during the dry season. In fact, as shown by Man et al (1993), it produces more leaf biomass in the dry than in the wet season, and is superior to other forage trees in this trait.

Table 5 Feed intake for the different treaments
	Treatments
	C	MUB	AmMUB
Feed intake (kg/d)
Grasses	14.0	18.2	14.3
Cottonseed cake	2.0	2.0	2.0
Concentrate	5.6
Rice bran		2.0	1.0
MUB		1.2	1.0
Acacia leaves			6.4
Total DM intake
kg/cow/day	12.3	11.8	11.1
kg/100 kg LW	3.4	3.1	2.8

Table 6. Mean values for milk yield in the pre-experimental and experimental periods
	Treatments
Periods	C	MUB	AmMUB	SD (Prob)
Milk yield (kg/day)
Pre-experiment	10.1	10.1	10.0	1.29 (0.995)
Experiment*	9.9	9.8	9.0	1.62 (0.18)

* Adjusted by covariance for yield in pre-experimental period

References

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Bui Xuan An, Ngo Van Man and Luu Trong Hieu 1992b Molasses-urea block (MUB) and Acacia Mangium as supplements for crossbred heifers fed poor quality forages. Livestock Research for Rural Development, Volume 4, Number 2:7-12

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(Received 1 October 1993)