Influence of Gliricidia sepium, multinutritional blocks and fish meal on live-weight gain and rumen fermentation of growing cattle in grazing conditions

Influence of Gliricidia sepium, multinutritional blocks and fish meal on live-weight gain and rumen fermentation of growing cattle in grazing conditions

Facultad de Agronomía, Universidad Central de Venezuela, Apartado 4579, Maracay, Venezuela

Three feeding trials were carried out to evaluate the influence of Gliricidia sepium and other nitrogen (N) supplements on the live- weight (LW) gain of growing cattle grazing Cynodon nlemfuensis. In all experiments gliricidia offered for three hours daily increased LW gains by 110 to 180 g/day above those of control animals (P<0.05). LW gains were related to the frequency of gliricidia feeding, increasing from 0.43 to 0.51 kg/day when it was raised from 2 to 7 days per week. The fish meal supplementation evaluated in the same trial had no influence on LW gain. A comparison between supplementation with gliricidia and multinutrient blocks (MB) in another trial resulted in a larger response with the legume. LW gain increments in relation to a control group without supplements were 80 g/day with MB and 160 g/day with gliricidia. A digestion trial using the same supplements as in the latter trial on rumen fistulated animals grazing a mixture of Cynodon nlemfuensis and Panicum maximum did not result in improvements in the rate or extent of digestion of the roughage in situ. The positive influence of gliricidia on LW gain in these conditions seems to be more related to the energy quality of the legume than to its supply of N to the animal or its rumen microorganisms.

KEY WORDS: Gliricidia sepium, cattle, grazing, live-weight gain, multinutrient blocks, fish meal.

Gliricidia sepium is a tree legume extensively used in live fences in tropical America. However, it is rarely used in cattle feeding in spite of some recent reports where large responses in live- weight (LW) gain have been observed from its use as a supplement to basal diets of cut forage in growing cattle (Preston and Leng 1987). Other feeds and technologies, such as by-pass protein sources and multinutrient blocks, are being recommended and adopted in this region (Combellas 1991) even when they usually require external inputs to the farm. Grazing systems are predominant in the area, and nitrogen (N) is not necessarily the primary factor limiting animal responses in these conditions.

A series of trials was carried out with growing animals on dual- purpose farms to evaluate the influence of supplementation with gliricidia on LW gain and compare the results with the effects of other supplements such as fish meal and multinutrient blocks (MB). A rumen digestion trial was also carried out with grazing heifers supplemented with gliricidia and MB to evaluate some aspects of rumen fermentation.

Three feeding trial (Experiments 1, 2 & 3) were carried out on two commercial farms located in the Aroa river valley, near the north coast of Venezuela, with an average monthly temperature ranging from 27.8 to 29.2°C and an annual rainfall of 855 mm. Dual-purpose farms are the predominant system in the area and feeding is based mainly on pastures of star grass (Cynodon nlemfuensis).

The feeding trials were carried out with weaned calves from crossbred herds with variable proportions of zebu and European breeds.

In Experiment 1 twelve males were used to compare the daily offer of gliricidia against a control treatment without this supplement using a Student "t" test.

Experiment 2 was carried out with 30 animals, 27 females and 3 males, using a completely randomized design with a factorial 3 x 2 arrangement to compare three frequencies of gliricidia offer: 0, 2 or 7 days per week, with and without 0.3 kg/day fresh weight of fish meal.

Twenty females in a completely randomized design with a factorial 2 x 2 arrangement were used in Experiment 3 to evaluate supplementation with gliricidia and MB in the field.

The duration of Experiments 1, 2 and 3 was 84, 92 and 84 days and initial LW's were 113 kg (SE=±3.8), 158 kg (SE=±18.3) and 155 kg (SE=±12.6). The animals were balanced according to initial weight between treatments and weighed every week afterwards until the end of each experiment.

All animals grazed together in four 0.25 ha paddocks of star grass (Cynodon nlemfuensis) rotated at weekly intervals in Experiment 1 and in four 0.5 ha paddocks of the same grass rotated every 1 to 2 weeks in Experiment 2. The animals of Experiment 3 were divided in two groups according to the MB treatment and grazed separately in four paddocks of 0.5 ha rotated every 1 or 2 weeks, alternating the groups in different paddocks.

All animals were taken out of the field daily at 0700h for about three hours to partially covered stalls separated according to treatments and the supplements offered. The feeds were given in groups, except in Experiments 1 and 2 where the animals were tied to consume gliricidia in individual troughs in the first trial and fish meal in separated buckets in the second. Branches of gliricidia were cut daily from live fences, weighed and offered by hanging them over feeding troughs for three hours. The residuals were weighed after feeding and removed. The fish meal was locally produced from by-products of the canning industry. The composition of MB (% fresh weight) was: molasses 35, sesame meal 30, urea 10, lime 10, common salt 5, mineral mixture (VENEFOSTRACAL) 5 and chopped grass hay 5.

The animals always had water available in the field and a mixture of equal parts of common salt and mineral mixture. The mineral mixture (VENEFOSTRACAL, FONAIAP, Maracay) is formulated mainly with calcium diphosphate and sodium chloride and has smaller amounts of other elements. The mineral mixture and MB were offered in covered feeders in the field.

The herbage on offer per unit area was estimated throwing quadrants of 1.0 x 0.5 m six times just before and after grazing each paddock. The samples were mixed and a subsample was frozen for analysis. The samples of herbage, gliricidia and fish meal were dried at 65 ?C for 48h, ground through a 1mm screen and analyzed for ash and N (AOAC 1984), calcium (Fick et al 1979) and phosphorous (Harris and Popat 1954). Herbage and gliricidia were also analyzed for neutral detergent fiber (Goering and Van Soest 1970).

The digestion trial was carried out at the Faculty of Agronomy in Maracay, which has a range in monthly average temperatures from 23.4 to 26.5°C and a mean rainfall of 989 mm.

A 4 x 4 Latin square with 21 day periods and 4 rumen fistulated growing heifers of 305 kg (SE=±4.2 kg) was used to evaluate the influence of the same treatments of Experiment 3 on pH, ammonia N concentration, volatile fatty acids (VFA) proportions in rumen liquor and rate and extent of DM digestion in nylon bags. One kg of fresh gliricidia was introduced daily between 0800 and 0900h in the animals on this treatment through the rumen cannula, instead of offering it for voluntary consumption during a restricted period of time as in the feeding trials. The animals were weighed every 21 days.

The animals grazed two paddocks of 0.1 ha with a mixture of Panicum maximum and Cynodon nlemfuensis. Every paddock was grazed by two animals and in one of them MB were available in a covered feeding trough. Both groups had access to the mineral mixture described before, and its consumption was evaluated weighing the offers and the refusals weekly. Measurements of herbage on offer were carried out as in feeding trials at days 13 and 21 of each period, and samples of herbage, gliricidia and MB were analyzed following the procedures described before. Rumen liquid samples were taken at 0800h and every 3h until 2300h on day 19 of each period, filtered through cheese cloth, pH measured and two samples of 30 ml acidified with eight drops of 97% sulphuric acid and stored in a freezer. The samples were analyzed for VFA and ammonia N following the methodology described by FAO (1986). The methodology of Orskov et al (1980) was used to estimate the rate and extent of herbage DM digestion, drying a sample at 65°C for 48h; grinding it through a 3 mm screen and introducing 5g in nylon bags. Ten bags were introduced in each animal at 0800h of day 19 of each period, and two bags were taken out at 6, 12, 24, 48 and 72h. The half time of DM digestion (T½) was calculated using the procedure described by Kempton (1980).

The samples of herbage on offer taken at ground level just before grazing in the feeding trials had an average crude protein (N x 6.25) content varying from 5.9 to 8.8% of DM and a high concentration of NDF (Table 1). The quality of herbage on offer slightly decreased at the end of grazing periods. Mean crude protein contents of gliricidia samples used in all trials varied from 19.5 to 24.0%. The chemical composition of the fish meal and MB used in Experiments 2, 3 and 4 is shown in Table 1.The average herbage on offer per unit area at the beginning and end of grazing is shown in Table 2. At the end of grazing, the average weight of standing forage was over 2000 kg DM/ha in all trials. The average intake of gliricidia and MB is presented in Tables 3, 4 and 5. The standard error of the mean was calculated with gliricidia in Experiment 1 only, because in the other trials the individual consumptions of neither the legume nor the MB were measured. In these trials the standard deviation of average daily intake was calculated to present an estimate of intake variations in the course of time. The range of gliricidia consumptions in feeding trials was between 0.46 and 0.63 kg DM/day. The intake per unit LW was greater in Experiment 1, where the animals received the legume in individual troughs.

Table 1: Chemical composition of foodstuffs (% of DM)

	CP	NDF	Ash	Ca	P

Experiment 1
Herbage before grazing	8.4	80.9	6.8	0.26	0.16
Herbage after grazing	8.7	81.2	7.3	0.20	0.10
Gliricidia	23.4	47.7	8.9	1.24	0.25

Experiment 2
Herbage before grazing	5.9	78.6	9.9	0.52	0.29
Herbage after grazing	4.8	82.9	10.0	0.46	0.20
Gliricidia	22.5	40.7	13.0	2.37	0.21
Fish meal	58.0	-	23.7	6.15	3.50

Experiment 3
Herbage before grazing	8.8	82.6	8.2	0.38	0.29
Herbage after grazing	5.9	84.0	6.8	0.35	0.24
Gliricidia	24.0	43.2	8.6	1.63	0.22
Multinutrient blocks	49.2	18.5	32.2	8.22	0.98

Experiment 4
Herbage during measurements	10.3	74.6	11.7	0.40	0.30
Gliricidia	19.5	39.5	11.9	2.80	0.20
Multinutrient blocks	48.6	20.8	31.8	8.00	1.00

Table 2: Weight of standing forage

	Weight of standing forage (kg DM/ha)

Experiment 1
Before grazing	4720
After grazing	2440

Experiment 2
Before grazing	5053
After grazing	3508

Experiment 3
Before grazing	3918
After grazing	2443

Experiment 4
Last week of periods	4403

Table 3: Live-weight (LW) gain and intake of gliricidia by growing cattle grazing Cynodon nlemfuensis with Gliricidia (G) or without (0) foliage in Experiment 1.

	0	G	SD

Gliricidia daily intake
DM (kg)		0.60
DM (g/kgLW)		4.23

LW gain (kg/day)	0.47	0.65	±0.048**

The daily offer of gliricidia increased LW gain in all feeding trials (Tables 3, 4 and 5). The average daily increases in LW gains in animals receiving gliricidia daily compared with control groups without supplements were 0.18, 0.11 and 0.16 kg in Experiments 1, 2 and 3. The offer of this legume twice a week in Experiment 2 (Table 4) raised LW gain in relation to the control treatment from 0.40 to 0.43 kg/day, but the difference did not reach significance (P>0.05). The use of fish meal in this trial did not influence LW gain, and the interaction gliricidia x fish meal was not significant (P>0.05). The supplementation with MB in Experiment 3 (Table 5) had a small non-significant effect (P>0.05) on LW gain and there was no interaction between gliricidia and blocks in this trial. Animals supplemented with MB alone gained 0.08 kg/day more than animals without supplements.

Table 4: Live-weight (LW) gain and intake of gliricidia by growing cattle grazing Cynodon nlemfuensis supplemented with the legume 0, 2 or 7 times a week, with or without fish meal in Experiment 2

	Gliricidia offer (days/week)			Mean	SE
	0	2	7

LW gain (kg/day)
Without fish meal	0.44	0.39	0.46	0.43
					0.025
With fish meal	0.35	0.46	0.55	0.45

Mean	0.40	0.43	0.51
SE	0.030*

Gliricidia intake on day of offer
DM (kg)	-	0.49	0.63

DM (g/kgLW)	-	2.73	3.43

Table 5: Live-weight (LW) gain and intake by growing cattle grazing Cynodon nlemfuensis without supplement (0) and with gliricidia (G) and/or multinutrient blocks (B) in Experiment 3

	Treatment					Signif. of effects
	0	G	B	GB	SE	G	B

LW gain (kg/day)	0.20	0.36	0.28	0.40	0.055	*

Gliricidia daily intake
DM (kg)		0.46		0.51
DM (g/kgLW)		2.67		2.79

Blocks daily intake
DM (kg)			0.28@
DM (g/kgLW)			1.63@

The rumen fermentation characters evaluated in Experiment 4 are shown in Table 6. Neither gliricidia nor blocks influenced rumen pH and molar proportions of VFA (P>0.05). The use of blocks increased rumen ammonia N concentration (P<0.05) from 184 to 255 mg/litre and slightly, but not significantly (P>0.05), reduced the rate of digestion and the amount of DM disappearance at 48h in nylon bags. The use of gliricidia had no effect on these functions (P>0.05).

The chemical composition of the herbage samples analyzed (Table 1) showed low values of N and high levels of fibre in all trials. However, the stargrass used in the feeding trials is a stoloniferus plant, and samples taken at ground level include a high proportion of stems usually not consumed in large amounts by the cattle when herbage availability is abundant. This was the case in these experiments, where large herbage allowances per animal (Table 2 ) permitted the selection of a better quality diet than the samples analyzed and described in Table 1 and explains the moderate LW gains obtained in control groups without supplements in all trials (Tables 3, 4 and 5). The daily offer of gliricidia for three hours resulted in significant LW gain increments in all feeding trials similar to those obtained in CIPAV (1987) with similar animals consuming cut forage. These responses were obtained with relatively low levels of supplementation. If it is assumed that total DM intake was 25 g/kg LW, the legume intakes in relative terms (Tables 3, 4 and 5) were between 10 and 15 % of the diet.

Table 6: Rumen fermentation indices of growing cattle grazing Panicum maximum and Cynodon nlemfuensis without supplement (0) and with gliricidia (G) and/or multinutrient blocks (B) in Experiment 4

	Treatment				SE	Signif. of effects
	0	G	B	GB		G	B

Rumen pH	7.1	7.1	7.1	7.2	0.05
Ammonia N (mg/litre)	184	196	255	249	21.9		*
Molar proportions of VFA:
Acetic	70.9	70.8	70.5	70.7	0.82
Propionic	17.3	17.1	17.1	17.4	0.65
Butyric	9.4	9.6	9.9	9.2	0.35
Iso-valeric	1.4	1.5	1.5	1.5	0.06
Valeric	1.1	1.0	1.0	1.2	0.13

DM disappearance at 48h (%)	61.2	61.6	59.7	58.8	1.68

Rate of DM digestion (T½, h)	65.2	60.9	70.0	64.9	3.15

The positive relationship between LW gain and the frequency of gliricidia offer found in Experiment 2 (Table 4), was also observed by Dixon et al (1991) with stall-fed sheep and goats receiving a basal diet of hay. These authors also observed a residual increase in rumen ammonia N concentration a few days after the legume was given, and pointed out that it could partially explain the positive influence of this supplement. The increments of LW gain with gliricidia in Experiment 2 do not seem to be related to its supply of N for two reasons. First, the addition of fish meal resulted in very small animal responses. The protein of this supplement was earlier shown to be 0.36 degradable (Marquez 1990) and would have provided both degradable N and by-pass protein. Secondly, there was a linear relationship between the frequency of gliricidia feeding and live weight gain, instead of the unvarying response which would otherwise have been expected when the legume was offered seven versus twice a week. The absence of residual effects on LW gain in the latter treatment, is an indication that degradable N was not deficient in the diet. Probably, as was mentioned before, the diet selected by these animals grazing cultivated pastures, such as star grass, is sufficient to fulfil their degradable N requirements.

The main effect of the legume seems therefore to be through an increase in the energy concentration and intake of the diet. This effect also explains the higher LW gains when the legume was offered daily instead of twice a week, and where larger consumptions of gliricidia occurred.

The small response to fish meal compared with the results obtained with cereal straws (Preston and Leng 1987) has also been observed in other trials with tropical forages or forages and concentrate, where sufficient N and adequate LW gains were achieved in control treatments without fish meal (Combellas et al 1993).

The results of Experiment 3 are in line with those of Experiment 2, because the LW gains obtained with MB are small and about half of those observed with gliricidia (Table 5), in spite of similar crude protein consumptions of 138 and 110 g/day with MB and the legume. The low animal responses to blocks contrast with the large effects observed in other regions (Preston and Leng 1987; Habib et al 1991; Sadullah et al 1991) where the basal diet was usually fibrous agricultural by-products with a very low content of N.

The levels of ammonia N observed in the digestion trial (Table 6) were within the values required to maximize the utilization and intake of low quality roughages (Leng 1990). The supplementation with blocks increased these levels, but did not improve the rate and extent of digestion of grass samples in nylon bags or other parameters evaluated. The introduction of gliricidia through the rumen cannula had no influence on these measurements. Experiment 4 was not carried out in the same location as the previous experiments and the quality of the pastures used was slightly higher than those observed in the feeding trials (Table 1). Consequently, lower levels of rumen ammonia N are to be expected in the latter trials. But as was observed by Dixon et al (1984) and Mata and Combellas (1992), probably the concentrations of this metabolite required to obtain adequate rumen function are lower with medium quality tropical forages than with roughages which are very low in N.

From the results obtained in these trials it may be concluded that better LW gain responses are obtained with gliricidia under these conditions than with other N supplements, such as multinutrient blocks or fish meal. The main influence of gliricidia seems to be through an increase in the level of energy intake and not through the supply of degradable N to rumen microorganisms or protein to the animal.

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