The aim of this study was to determine the feasibility of: (i) using the growing point of sugar cane (sugar cane tops) as the basal diet for lactating goats; and (ii) replacing the concentrate supplement with a combination of leaves of Acacia mangium, a molasses-urea block and rice bran.

Twelve dual purpose goats (Bac Thao breed) were fed the standard diet of the experimental station (ad libitum guinea grass Panicum maximum and 500 g/day of concentrate) for the first 4 weeks of lactation. The does suckled their kids 24 hours/day for the first 3 weeks after which the kids were separated and once daily hand milking in the morning was introduced, with suckling for 30 minutes after milking and again in the afternoon (no milking). Milk yield was measured from the 4th week as the total of milk produced at milking plus that consumed by the kids (by weighing before and after suckling). These data were used as the covariate to correct milk yield during the subsequent 3 weeks (weeks 5 to 7) when the experimental diets were fed. The experimental diets consisted of: (i) Guinea grass (Panicum maximum) ad libitum and 500 g/day of concentrate (control); (ii) Guinea grass ad libitum, 200 g/day of molasses-urea block (10% urea), Acacia mangium foliage ad libitum, 200 g/day of rice bran; (iii) Sugar cane tops (the growing point) ad libitum and concentrates; (iv) Sugar cane tops, Acacia mangium, molasses-urea block and rice bran.

Adjusted milk yields (for yield during the standard 4th week) during the 7th week (after 3 weeks on the experimental diets) were: 998, 1218, 1278 and 1325 ml/day (SE±90; P=0.11). Sugar cane tops were a more economical basal diet for lactating goats than guinea grass and supported slightly higher milk production and growth in the kids. Supplements of Acacia mangium leaves, a molasses-urea block and rice bran, designed to supply rumen and bypass nutrients, were cheaper and supported higher milk production than conventional cereal-based concentrates.

The mountainous and hilly areas of Vietnam make up two thirds of the total area. In these regions, the farmers raise cattle, buffaloes and goats, and plant sugar cane and cassava as cash crops. Sugar cane is a highly productive source of biomass in these regions with potential yields of fresh matter of between 70 and 120 tonnes/ha/year (Nguyen thi Mui et al 1995). Sugar cane tops are by-products making up 18-20% of the total biomass of the plant and have been widely studied as a basal diet for fattening and milking cattle (Ferreiro et al 1976; Boodoo et al 1990).

The annual yield of sugar cane in Vietnam is about 5.4 million tonnes, and the quantity of sugar cane tops is about 1.1 million tonnes (Anon 1991). Traditionally, farmers use part of the sugar cane tops for planting, some for animal feeding in the dry season, while the remainder is often wasted.

Up to now little research on using sugar cane tops for dairy goats has been done. Since 1992 the Goat and Rabbit Research Centre as been working with dual purpose goat production based on use of local feed resources.

The aim of this study was to determine the feasibility of: (i) using the growing point of sugar cane (sugar cane tops) as the basal diet for lactating goats; and (ii) replacing the concentrate supplement with a combination of leaves of legume tree Acacia mangium, a molasses-urea block and rice bran. This latter form of supplementation takes into account the separate nutritional needs of rumen micro-organisms and the animal (Preston and Leng 1987).

Twelve dual-purpose goats (Bach thao breed) were used in the trial. Each doe suckled one to three kids. During the first three weeks milking was not practised, all the milk being taken by the kids by suckling. From the fourth week onwards the management was changed to once per day milking (by hand) followed by restricted suckling (30 minutes) in the morning, and suckling in the afternoon (30 minutes) without milking.

The control diet of Guinea grass (ad libitum) and concentrate (500 g/day) was fed throughout the first four weeks. The milk yield at milking and by suckling (weighing the kids before and after suckling) was estimated daily from the fourth week onwards. The yield during the fourth week was used as covariate to adjust milk yields during the experimental periods in weeks 5, 6 and 7.

The experimental diets were introduced in week 5 and consisted of:

• Guinea grass (Panicum maximum) ad libitum and 500 g/day of concentrate (control).
• Guinea grass ad libitum, 200 g/day of molasses-urea block (10% urea), Acacia mangium foliage ad libitum, 300 g/day of rice bran.
• Sugar cane tops (the growing point) ad libitum and concentrates.
• Sugar cane tops, Acacia mangium, molasses-urea block and rice bran.

Results for milk production are presented in Table 1.

Table 1: Mean values for milk production by goats fed basal diets of Guinea grass or sugar cane tops supplemented with either concentrates or molasses-urea block, Acacia mangium and rice bran (3 does per treatment)
Milk yield, g/day	Guinea grass		Sugar Cane Tops
	Conc	MU/Am	Conc	MU/Am	SE/P
Standard diet
(covariate)
4th week	1288	1283	1232	1144	34/0.02
Experimental diet*
5th week	1182	1212	1197	1309	57/0.55
6th week	1108	1232	1264	1205	52/0.16
7th week	998	1218	1278	1325	90/0.11

*Adjusted by covariance for yield in the standard period (week 4)

There was a tendency for milk production to be higher on the basal diet of sugar cane tops than on guinea grass and for the supplement of Acacia mangium, molasses-urea block and rice bran to be better than the concentrates (P=0.11 in week 7).

Feed costs were least on the diet of sugar cane tops, Acacia mangium, molasses urea block and rice bran (Table 2).

Table 2: Mean values for feed intake during weeks 4 (standard period) and 7 (3rd week on the experimental diets).
	Guinea grass		Sugar cane tops
Feed intake, kg/day	Conc	MU/Am	Conc	MU/Am
Week 4
Guinea grass	5.22	5.26	4.92	4.88
Concentrate	0.42	0.42	0.42	0.42
Dry matter	1.62	1.48	1.58	1.54
Week 7
Guinea grass	4.96	4.04
Scane tops			3.62	2.96
Concentrate	0.42		0.40
Acacia mangium		0.84		0.83
MUB		0.19		0.20
Rice bran		0.20		0.20
Dry matter	1.52	1.58	1.11	1.23

The mean values for liveweight gain of the kids are given in Table 4. Growth rates were higher for kids from does fed the basal diet of sugarcane tops than for those from does fed guinea grass.

Table 3: Feed costs per kg milk production (VND)
	Guinea grass		Sugar cane tops
	Conc	MU/Am	Conc	MU/Am
Week 4 (Standard)	930	930	940	1020
Experiment (5-7 wks)
Mean	1063	630	856	550
Comparison (%) with Control	100	59	81	52

Table 4: Mean values for liveweight gain (g/day) of the kids being suckled by does fed guinea grass or sugarcane tops and concentrates or urea-molasses block, Acacia mangium leaves and rice bran (12-13 kids per treatment)
	Guinea grass		Sugarcane tops
	Conc	MUAm	Conc	MUAm	SE/P
Standard period
Week 4	97.5	96.5	99.8	96.7	1.70/0.05
Experimental:
Week 5	102	97.6	97.6	103	0.94/0.03
Week 6	98.8	101	106	106	1.65/0.05
Week 7	101	102	108	108	1.37/0.04

Sugar cane tops were a more economical basal diet for lactating goats than guinea grass and supported slightly higher milk production and growth in the kids. Supplements of Acacia mangium leaves, a molasses-urea block and rice bran, designed to supply rumen and bypass nutrients were cheaper and supported higher milk production than conventional cereal-based concentrates.

(Received 15 September 1995)