In Colombia, the planting of leguminous trees in association with pasture for sustainable production of animal feed is a recent development. A trial was carried out in 1993 in an association of Erythrina fusca trees (600 to 1100 trees/ha) and African Star grass (Cynodon nlemfuensis) established in 1986 in the Arizona farm, Jamundi, Valle, Colombia. The upper branches of the trees were lopped at intervals of 90-120 days passed through a forage chopper and wilted for 24 hours before being fed to F1 Holstein*Zebu milking cows.

Initial observations were that intake of the foliage was relatively low (<2% of body weight, fresh basis) and variable. To test the hypothesis that crude palm oil might have a stimulating effect on intake, a series of mixtures was prepared with different combinations of palm oil, calcium hydroxide and the wilted foliage of Erythrina fusca. The following formula (% by weight) appeared to be the most satisfactory in terms of consistency of the final product and acceptability by cattle: Palm oil 7, final molasses 9.7, wilted Erythrina foliage 82, calcium hydroxide 1.3.

Three experiments were carried out to evaluate the erythina/palm oil mixture as a supplement for the milking herd. Twenty-seven cows were selected from the commercial F1 Holstein*Zebu milking herd in the Arizona farm the basal diet of which was rotational grazing of African star grass and a concentrate mixture of 42% poultry litter, 21% rice polishings, 21% Palm kernel cake, 15% of distiller's solubles (Vinaza) and 1% salt. Milk yield was measured daily for one week while the animals received the commercial concentrate supplement. These data were used as the covariate to correct yields during the experimental period of 14 days. The experimental supplements were then fed for a period of 21 days; seven days for the changeover and 14 days for collection of data.

In experiment 1, the control group received the standard concentrate allowance at the rate of 4 kg/cow/day. The second group (PM280C) received 2 kg of the control diet and 4 kg of the Erythrina-African palm oil mixture (provided 280 g oil/cow/day). The third group (PM560) was fed 8 kg of the Erythrina-African palm oil mixture (560 g oil cow/day). In experiment 2, the PM280C treatment was modified, leaving out the concentrate. In experiment 3, three levels of foliage/oil (4/280, 6/420 and 8/560) were evaluated.

In Experiment 1, the average production for both experimental treatments was 8% higher (P=0.001) compared with the control. In Experiment 2, the PM560 treatment supported a 5% higher milk yield (P=0.001) than the control. The PM280 treatment did not differ from the control. In Experiment 3, the PM280 supported a 10% lower (P=0.001) milk yield than the control; the PM420 and PM560 did not differ from the control.

It is concluded that a mixture of 4 kg wilted Erythrina foliage plus 280 g palm oil and 9 g calcium hydroxide could replace 2 kg of the conventional concentrate supplement used in the farm. The satisfactory performance of the commercial dual purpose F1 Holstein*Zebu cattle in the Arizona farm during 1994 and 1995, when 50% of the supplement of the milking cows was composed of the Erythrina/oil mixture supports this conclusion.

Agroforestry has been practiced for many decades in industrial plantations of coconuts, rubber and oil palm, primarily a means of controlling weed and grass growth. The traditional method was to plant an aggressive legume such as tropical kudzu (Pueraria phaseoloides), which improved the nutritional value of the herbage under the trees as well as supplying nitrogen to the trees. Sheep were usually the preferred animal species. The "Alley farming" system of agroforestry developed in West Africa (Attah Krah 1990), in which legume shrubs or trees (usually Leucaena leucocephala or Gliricidia sepium) were planted in rows at 5-10m distances, was intended primarily as a means of providing mulch and fertilizer for the associated arable crop, or for "cut and carry" management of livestock .

In Colombia, the planting of leguminous trees in association with pasture for sustainable production of animal feed is a more recent development (FAO 1992; Molina et al 1995 and unpublished data; Rodriguez and Cuellar 1994, unpublished data). In this system trees such as Gliricidia sepium, Leucaena leucocephala and Erythrina fusca are planted at densities in the range 600 to 1100/ha (E fusca), 10,000 to 20,000 (G sepium, L leucocephala) and 25-50/ha (Prosopis juliflora), in association with gramineas such as Star grass (Cynodon nlemfuensis) and Argentina grass (Cynodon dactylon). The trees are lopped at intervals of 90-120 days in the case of E fusca and G sepium, browsed at intervals of 40-60 days for L leucocephala or left for the fruits to fall and be consumed in situ or collected (P juliflora).

Erythrina fusca is a leguminous tree found in Colombia in areas of high humidity. EDIT In "Hacienda Arizona", located 25 km from Cali, Erythrina trees have been used for more than 20 years as components of "live" fences. In 1986 the first observations were made to determine the effects of cutting back the branches of mature trees to stimulate regrowth of immature foliage. The results were promising and it was decided to establish protein banks with this species in order to evaluate its use as a source of high-protein leaves and as a component of an agro-forestry system based on African Star grass (Cynodon nlemfluensis). Three areas were established.

Protein bank

A small block of trees planted from seed and cuttings at a high density (area 231 m², 249 trees, row distance 0.9m and space between trees 0.9m). The first harvest was made at 16 months and subsequently at approximately 3-4 month intervals. Average yield of foliage (leaves, petioles and small branches) was 10 kg/tree/harvest.

Agroforesty system

Two fields were planted from a combination of cuttings and seed. The first had an area of 1 ha, with 1,102 trees at distances between them of 3m. The second was 9,913 m², with 512 trees at a distance of 4m between trees. The original vegetation in both fields was African Star grass which quickly re-established itself to form a stable association with the trees. Management consisted of rotational grazing with 6 divisions in each area using electric fences. Occasionally the milking herd of dual purpose Holstein-Zebu F1 cows grazed the pasture but mainly this was with calves both pre- and post-weaning. The foliage of the trees was cut from branches 2m above ground level. The first harvest was 16 months after planting and subsequently at 3-4 month intervals. The shade effect of the trees ranged from zero, immediately after harvesting, to 100% after 3-4 months of regrowth when the next harvest of the foliage was due. Estimations of biomass production of the star grass (by cutting 1 m squares prior to grazing) were of the order of 90-100 tonnes/ha/year. The mean yields of erythrina foliage were: 13.3 and 15.7 kg/tree/harvest for the 3*3 and 4*4 spacings, respectively. Annual yields averaged: 51 and 28 tonnes fresh foliage/ha/year.

With these yields it was estimated that the legume foliage used as a supplement (9 kg/day for animals of 300 kg live weight) would support 8-13 animals/ha/year; and that the capacity of the pasture was 3 animal units (400 kg live weight)/ha/year.

The harvesting procedure resulted in considerable quantities of branches considered to be inedible (>2cm diameter) being left in the field to be recycled. The amounts were estimated, on the basis of spot weighings, to be of the order of 30-40 tonnes/ha/year.

Erythrina fusca foliage as protein supplement

The Erythrina foliage (leaves, petioles and green stems) was passed a forage chopper prior to feeding. With this system the spines on the stems were sufficiently broken as not to cause physical damage to animals in the course of eating.

The first observations were that the intake of the foliage by lactating and growing animals was extremely variable but generally was low, and less than 2 kg per 100 kg live weight. However, when the foliage was sprinkled with molasses, sugar cane juice or "vinaza" (distiller's solubles), the intakes increased. To obtain more precise information on the effect of different forms of presentation on intake an experiment was carried out with growing heifers fed a basal diet of pressed sugar cane stalk (offered at 2-3 times intake; see Vargas 1993), 500 g/day of rice polishings and free access to a solution of "vinaza" with 10% urea. The treatments were: Erythrina foliage fed fresh, after 24 hours wilting or fresh and sprinkled with a mixture of "vinaza" and sugar cane juice. The control was chopped pangola grass (Cuellar et al 1992). Intakes of Erythrina foliage were high on all treatments (>4 kg/100 kg llive weight and weight gains were best for the wilting and sprinkling treatments.

A second experiment was initiated to establish the effect of varying the offer level of the Erythrina foliage presented after 24 hours wilting, since this appeared to be the most appropriate system based on the results of the previous experiment. The levels were 2, 2.5, 3, 3.5 and 4 kg/100 kg llive weightand were given to five groups of F1 Holstein-Zebu heifers fed a basal diet of pressed sugar cane stalk, vinaza enriched with 10% urea, 500 g/day of rice polishings. It soon became evident that the animals were unable to consume the indicated quantities of the legume foliage. This was in marked contrast with the earlier trial (Cuellar et al 1992) when intakes of 4 kg foliage/100 kg llive weightwere achieved. The only explanation for this difference was the poorer quality of the legume foliage which was derived from trees that had not been harvested regularly and had a high proportion of woody stems and over-mature leaves. The experiment was suspended as due to management problems it was not possible to secure foliage of the required quality.

African palm oil

A major outcome of the economic liberalization initiated by the Colombian Government in 1992 was the elimination of most price supports to the major agricultural crops. The effect was especially dramatic on production and prices of locally grown soya beans and African oil palm. Soya bean cultivation was practically eliminated as it was uneconomic to produce this crop at prevailing world prices and much more attractive to import both the oil and the meal. The producers of African Oil Palm faced direct competition from imports of palm oil from Malaysia which was being landed in Colombian ports at much lower prices than had been established under the previous price support system. However, because of the greater efficiency of the African Oil Palm in using the natural tropical resources, the cultivation of this crop continued to be profitable, even at the prevailing world price of approximately US$400/tonne (cif Rotterdam). The oil palm producers were also favoured by the fact that the industry was established in a period of strong Government support and had reached full production at the time when this support was withdrawn.

The implications of palm oil being available locally at prices of US$450-500/tonne were that it became competitive with cereal grains as a source of energy. Because of this development it was decided to evaluate the use of crude palm oil as a component of the supplement traditionally fed to the milking animals. It was hypothesized that: (i) reacting the oil with calcium hydroxide would make it inert at the level of the rumen (Palmquist 1984); (ii) that a legume foliage would be a suitable complement for the oil providing the required protein from a locally available resource; and (iii) the oil might improve the intake of the foliage.

A series of mixtures was prepared with different combinations of palm oil, calcium hydroxide and wilted (24 hours) foliage of Erythrina fusca. The following formula (% by weight) appeared to be the most satisfactory in terms of consistency of the final product and acceptability by cattle: Palm oil 7, final molasses 9.7, wilted Erythrina foliage 82, calcium hydroxide 1.3. Surprisingly, intakes were much higher (>2 kg/100 kg live weight) and the rate of consumption was markedly increased compared with all previous experiences.

Three experiments were carried out to evaluate the erythina/palm oil mixture as a supplement for the milking herd.

Twenty-seven cows were selected from the commercial F1 Holstein*Zebu milking herd in the Arizona farm. They were divided at random into three groups taking account of parity and stage of lactation. Milk yield was measured daily for one week while the animals received the commercial concentrate supplement. These data were used as the covariate to correct yields during the subsequent experimental period of 21 days. The experimental supplements were then fed for a period of 28 days; seven days for the changeover and 21 days for collection of data. The control group received the standard concentrate allowance (Poultry litter 42, Rice polishing 21, African Palm Meal 21, Vinaza 15, Salt 1) at the rate of 4 kg/cow/day. The second group (PM280C) was fed with 2 kg of the control diet and 4 kg of the Erythrina-African palm oil mixture (provided 280 g oil/cow/day). The third group (PM560) was fed with 8 kg of the Erythrina-African palm oil mixture (560 g oil cow/day). The supplements were given in four feeds: 25% prior to milking in the morning (07.00) and again in the afternoon (14.00); and 25% during each milking.

Experiment 2:

The procedure described in Experiment 1 was repeated with the following modifications:

The same procedure as in previous experiments was applied. The supplements were:

Table 1: Mean values for supplement intake and milk production* of F1 cows rotationally grazed on African Star grass and given supplements of fresh foliage of Erythrina fusca mixed with palm oil
Experiment 1:
Supplement (kg/d)
Concentrates	4	2	0
Foliage/oil	0	4/0.25	8/0.5
Milk yield (litres/d)	10.4	11.3	11.2
SE/Prob	--------- ±0.16/0.001 ------
Experiment 2:
Concentrates	4	0	0
Foliage/oil	0	4/0.25	8/0.5
Milk yield (litres/d)	9.68	9.60	10.2
SE/Prob	---------- ±0.15/0.001 --------
Experiment 3:
Concentrates	4	0	0	0
Foliage/oil	0	4/0.25	5.6/0.35	8/0.5
Milk yield (litres/d)	9.45	8.48	9.23	9.08
SE/Prob	------------ ±0.17/.001 ---------------

* Milk yields adjusted by covariance according to yields prior to introducing the experimental supplements

Mean values for corrected milk yields during the experimental periods are given in Table 1. In Experiment 1, the average production for both experimental treatments was 8% higher (P=0.001) compared with the control. In Experiment 2, the PM560 treatment supported a 5% higher milk (P=0.001) than the control. The PM280 treatment did not differ from the control. In Experiment 3, the PM280 supported a 10% lower (P=0.001) milk yield than the control; the PM420 and PM560 did not differ from the control.

There were slight variations in response to the erythrina/palm oil supplement which may have been due to differences in the composition of the tree foliage which came from different trees harvested on different days during the course of the three experiments. A reasonable conclusion is that the PM280 (4 kg erythrina foliage with 280 g palm oil) treatment is probably inferior to the 4 kg of conventional concentrates; and that the PM420 and PM560 treatments are as good as the control and may even be slightly better.

It is interesting to speculate on the reasons for the improvement in intake and satisfactory milk yield response as a result of mixing low concentrations of palm oil (plus calcium hydroxide)with the Erythrina foliage. According to the farmer, thorough mixing of the three ingredients in a horizontal paddle mixer was an essential feature of the preparation of the supplement. It can be hypothesized that the synergistic effect of the oil on intake was because it acted as a sink for the volatile compounds that appear to act as a detriment when the Erythrina foliage is fed fresh. This is in line with the practical observation concerning the importance of thorough mixing.

Table 2: Mean values for performance traits in a commercial herd of F1 Holstein*Zebu cattle during 1994 and 1995 (Source: Arizona farm records)
	1st lactation		Total
	1994	1995	1994	1995
Number of cows	15	10	57	52
Age 1st calving,mths	35	32
Milk yield, kg	2626	2627	2686	2613
Lactation days	336	317	297	257
Calving interval, mths			12.3	12.3

In practice the farmer opted for the PM280C system: 4 kg erythrina foliage, 280 g oil, 9 g calcium hydroxide plus 2 to 4 kg/day of concentrates, the latter according to yield. The production data for 1994 and 1995 using this feeding system are shown in Table 2. The parameters for both production and reproduction can be considered as highly satisfactory for this particular farming system.

The experimental findings indicated that a mixture of 4 kg wilted Erythrina foliage plus 280 g palm oil and 9 g calcium hydroxide could replace 2 kg of the conventional concentrate supplement used in the farm. The satisfactory performance of the commercial dual purpose F1 Holstein*Zebu cattle in the Arizona farm during 1994 and 1995, when 50% of the supplement of the milking cows was composed of the Erythrina/oil mixture supports this conclusion.

The hypothesis that the oil acts as a sink for volatile compounds, which in the fresh foliage inhibit intake, should be tested with other leguminous trees where palatability is a problem.

This research was partially financed by the International Foundation for Science through the grant (B/2082-1) awarded to the senior author. The interest and encouragement, and many valuable practical observations, received from Sr Alfonso Madriñan, owner of the Arizona farm, were an important contribution to the successful outcome of the trials.

(Received 10 March 1996)