Experiments were made with lactating rabbits using (i) ensiled groundnut tops or dried pressed cane stalk, as a substitute for hay, and (ii) the fresh peeled sugar cane stalk, supplemented with toasted soybean seed and Canada bean foliage, as the basal diet replacing concentrate and grass. The peeled cane stalk diet was also used for fattening rabbits (iii).

Ensiled groundnut foliage gave the best reproductive performance and pressed sugar cane stalk was superior to dried pangola grass. There was an indication of greater loss of body weight during lactation and of slightly lower weights of the offspring at birth and at 21 days for the treatment in which the does were given the peeled sugar cane. However, costs were considerably less since fewer purchased inputs were needed.

Liveweight gain was 56% higher and feed conversion tended to be improved for the growing rabbits given the peeled sugar cane stalk supplemented with soya bean seed and Canada bean foliage compared to the concentrate fed control group.

The traditional feed resources for rabbits in intensive systems in experimental stations in Vietnam have been grasses and concentrates from cereal grains or cereal grain by-products. These feeding systems have had little impact with farmers because the green grasses are difficult to grow in winter and cereal grains and their by-products are steadily increasing in cost and are in competition with the nutritional needs of people. Earlier reports from this centre (Bin van Dinh et al 1993) showed the potential of molasses, incorporated into multi-nutritional blocks, as an alternative to cereal grains.

Sugar cane grows throughout Vietnam and is a highly productive and low cost resource useful for food, feed and fuel purposes (Mui et al 1995). Most importantly the yield and the quality are highest in the winter period which is when conventional feeds are scarce. Preliminary reports from Colombia (Solarte et al 1990) and Haiti (Bien-aime and Denaud 1989) investigated the use of fresh sugar cane juice as a replacement for concentrates. The system, although technically feasible, required too much infrastructure (eg: a sugar cane press) and was not attractive to small scale farmers. More recently, observations have been made at this centre on the use of the freshly peeled cane stalk. It was noted that rabbits ate readily the cane stalk, either freshly peeled or as the residue after partial extraction of the juice.

The objectives of the present experiments were to study the utilization of the dried pressed cane stalk, as a substitute for hay, and of the fresh peeled sugar cane stalk as the basal diet, supplemented with toasted soya bean seeds and Canada bean foliage, replacing concentrate and grass in the diet of lactating and growing rabbits, compared with the traditional system of concentrate and grasses.

In the first experiment, 30 pregnant New Zealand White female rabbits were divided into 3 groups. Three treatments were compared as forage supplements to traditional concentrates: sun- dried pressed sugar cane stalk; ensiled foliage of groundnut; and the control of dried pangola grass.

The pressed cane stalk was the residue from extraction of the juice obtained by passing whole sugar cane stalks three times through a simple buffalo-driven two-roll crusher. They were sun- dried before feeding. Whole cane stalk contains 30% of dry matter comprising 50% soluble sugars (a mixture of sucrose, glucose and fructose) and 50% fibre. The extraction rate in the crusher was 50% (50 kg juice from 100 kg cane stalk). The juice on average contains 20% sugars therefore approximately one third of the original sugars remains in the residual pressed stalk equivalent (DM basis) to: [(15-10)/20] x 100 = 25%. The pangola grass was cut at the pre-flowering stage and sun-dried. The concentrate was a commercial pelleted feed containing 17% crude protein.

In the second experiment 20 does were allocated to: an experimental diet based on peeled sugar cane stalk supplemented with roasted whole soybean seed and foliage of Canada bean; the control group which concentrates and grass. Fresh sugar cane stalks were peeled to remove the outer rind, cut into lengths of 20-30 cm and split longitudinally before being offered ad libitum to the rabbits. Whole soya beans were roasted on a metal surface over an open fire for 20 minutes before fed whole. The canada bean foliage was obtained from the whole plant at the stage of formation of the grain. The concentrate mixture was a commercial pelleted feed with 17% crude protein. The grass was Panicum maximum harvested at the pre-flowering stage.

In the third experiment, there were 8 cages with 3-5 New Zealand White rabbits recently weaned (age of 5 weeks) per cage. Four cages were allocated to the same treatments as in Experiment 2.

Feed intake was measured daily. Live weight of the does was recorded at parturition and at weaning, and of the growing rabbits at the beginning of the trial (35 days) and at 10 day interals during the 4 week growing period.

The results of experiment 1 (Table 1) show that the ensiled groundnut foliage promoted highest weaning weights and milk yield and that the pressed sugar cane stalk was superior to pangola hay.

Table 1: Mean values for perfomance of lactating rabbits fed different forages as supplements to concentrates
	Pangola	Pressed	Ground	SE/Prob
	hay	cane stalk	nut foliage
Forage intake
(g/day)	25	35	193
Change LW of
doe (kg)*	-0.23	-0.18	-0.15	±.07/0.69
Litter size at
weaning (n)	5.13	4.67	4.83	±.43/0.74
Mean LW of
offspring (g/head)
Birth	53.5	49.0	53.7	±0.11/0.47
21 days	176	212	262	±13/0.03
Milk yield (0-21
day)(g)**	1191	1386	1818	±96/0.002

* From parturition to weaning
** Adjusted by covariance for numbers weaned

The results of experiment 2 are shown in Table 2. There was an indication of greater loss of body weight during lactation (P= 0.03) and of lower weights of the offspring at birth (P=0.13) and at 21 days (P=0.15) for the treatment in which the does were given the peeled sugar cane. However, costs were considerably less for the cane stalk system, since fewer purchased inputs were needed (24 g/rabbit/day soyabean seed compared to 94 g/day of concentrate per head eaten by the control group).

Table 2: Mean values for weight change of does during lactation and growth of offspring to weaning at 21 days
	Control	Expt	SE/P
Number of does	9	10
Change of LW of does (g)*	-200	-310	±32/0.03
Litter size at birth	5.40	5.10	±0.032/0.47
Mean weight of offspring (g)
at birth	52.4	48.6	±3.0/0.13
at 21 days	204	192	±11/0.13
Feed intake (g/day/doe)
Concentrate	94.1
Guinea grass	548
Sugar cane stalk		276
Soya bean seed		24
Canada bean foliage		421
Total DM	214	270
Total N x 6.25	17.3	19.0
Cost of production
(VND/kg of offspring wt)	6,800	5,600

Liveweight gain was 56% higher (P = 0.02) and feed conversion tended to be improved (P = 0.21) for the growing rabbits given the peeled sugar cane stalk supplemented with soya bean seed and Canada bean foliage compared to the concentrate fed control group (Table 3).

Table 3: Mean values for performance of fattening rabbits fed peeled sugar cane stalk as the basal diet
	Control	Exptl	SE/P
	(conc)	(sug cane)
Live weight (g/head)
Initial	459±41	468±53
Final	770±70	873±178
Daily gain (g)	11.2	17.1	±1.30/0.02
Feed intake (g/head/day)
Concentrate	36.2	6.01
Grass	124	9.41
Sugar cane stalk		91.9
Soyabean seed		23.9
Canada bean foliage		68.7
Total DM	53.6	62.6	±7.3/0.42
Feed conversion (DM)	4.85	3.75	±0.57/ 0.21

The main conclusions of the study were:

• Dried pressed sugar cane stalk can be used as a source of forage in lactation diets for rabbits in winter instead of the traditional dried pangola grass.
• Peeled sugar cane stalk, supplemented with protein-rich feeds (soyabean seed and Canada bean foliage), can replace concentrates and grass for lactating and fattening rabbits.
• The utilisation of sugar cane to feed rabbits and other animals is suitable in Vietnamese conditions for both commercial systems and the household sector. Sugar cane is an important source of fibre and energy for the rabbit.

This study was carried out with financial support from the SAREC Project S/2 VIE 22.

(Received 1 August 1995)