Effect of Leucaena leucocephala and Brassica napus on growth of pigs fed wheat bran diets

Effect of Leucaena leucocephala and Brassica napus on growth of pigs fed wheat bran diets

Five groups, each of six mixed breed weanling pigs, were each fed one of the following diets ad libitum for six weeks: commercial feed (CF), wheat bran (WB), WB with leucaena leaves (WB&LL), WB with forage turnip (WB&T) and WB with both leucaena and turnip (WB&LL&T). Average daily weight gains did not differ significantly (P>0.05) between the CF (244 g/day) and the WB&LL&T (194 g/day) diets; both these treatments as well as the WB&LL diet were superior (P<0.05) to the WB only (114 g/day) treatment. Feed conversion on the wheat bran diet was improved by the addition of the forages, 47% for WB&LL, 25% for WB&T and 59% in the WB&LL&T diet.

KEY WORDS: Leucaena leucocephala, Brassica napus, forage turnip, wheat bran, pigs, diet.

Pig production can be an alternative means of producing high quality proteins for human consumption but has been criticized as consuming feeds which could be more efficiently utilized in direct nutrition of people (Eusebio 1980). Use of agro-industrial by-products such as cereal brans unfit for human consumption or high-quality forages may avoid competition for human foods. In many regions of Africa where Glossina spp. preclude the effective exploitation of ruminant meat production, the need for viable husbandry methods for monogastric animals reinforces the importance of studying alternative feed resources for these animals.

Wheat bran is one agro-industrial product which is available in most tropical and sub-tropical countries, usually in considerable amounts even when 100% of the wheat consumed is imported. Godinho (1986) wrote that it may be added to swine diets in proportions of up to 30% and is usually fed, for its high fibre content, normally to growing/finishing animals and brood sows (Eusebio 1980). Crude protein and DE contents vary but the NRC (1988) gave 15.5% and 2,155 kcal/kg for these parameters (average values). Forage turnip, Brassica napus has been recommended for pig production due to its succulence and ease of digestibility (Godinho 1986) although lack of seed production in most warm climates (Pupo 1985) limits applicability. Its popularity among pig producers in Mozambique (Morgado 1978) may be due in part to high crude protein contents which can reach up to 18% on a dry matter basis (Pupo 1985).

Forages have been widely recommended for pig production due to their high vitamin and mineral contents, especially important to confined herds (Morgado 1978; Godinho 1986). One of the most widely grown warm-climate tree forages, leucaena (Leucaena leucocephala), has great potential for pig nutrition due to its succulent leaves and high protein content. Brewbaker et al (1985), however, caution that it may contain high percentages of toxic mimosine which may limit its use, especially for reproductive classes of monogastrics. Under some conditions, for example with ensiled material up to 20% of the diet (Hongo et al 1990) and leaf meal at 16% of the diet (Chen et al 1981), the leucaena supplemented diet was as good as or better than control diets in growing pigs.

The objective of this experiment, therefore, was to study the inclusion of forage turnip and fresh Leucaena leaves in a basal wheat bran diet fed to weanling pigs. Weight gain of animals fed these forages separately or together were compared to gains obtained by animals fed a commercially manufactured pig feed.

Forage turnip was seeded in mid cool-season 4 months prior to the experiment. Leucaena trees which were used to collect forage had been established for 4 years ago. Five groups, each of six recently-weaned pigs of mixed Large White and Landim (local) breeds, three females and three castrated males in each group, were selected from several local piggeries. An attempt was made to assign animals to groups such that average weight (8.3 kg) was similar among groups. This selection of mixed breeds and sexes was done in an attempt to parallel local conditions.

During mid-hot season, each of these groups was given one of the following diets (see Table 1 for component dry matter, mimosine and crude protein) ad libitum in a Completely Randomized Design.

CF: Commercial weanling feed
WB: Wheat bran
WB&LL: Wheat bran and fresh leucaena leaves
WB&LL&T: Wheat bran, fresh leucaena and fresh turnip
WB&T: Wheat bran and fresh turnip

The pigs were confined and given one week to adapt to the environment and diet and thereafter weighed weekly. Amounts of diet components consumed were measured. Water and salt blocks were constantly available. The experiment was terminated after six weeks. Four animals from each treatment (excepting the largest and the smallest since slaughtering facilities were limited) were then slaughtered and carcass (including skin but excluding head) and organ percentage of live weight were determined. Back fat was not measured since little or no fat was deposited on any animal in the five treatments.

Table 1: Partial analysis of dietary components

Analysis	Feed	Wheat bran	Leucaena	Turnip

DM (%)	88	87	27	10
Nx6.25 (% DM)		16.5	25.6	9
Mimosine (% DM)			0.5
2,3DHP (% DM)			ND*
3,4DHP (% DM)			0.9

Coefficients of variation were high for the trial, indicating high variability due perhaps to differences in animal age, breed and physical condition. The different origins of the pigs may account for this variability and might have been reduced by increasing the number of animals per diet. Analysis of covariance was therefore performed using animal weights as the covariant. Results shown in Table 2 were obtained using this analysis.

Table 2: Weekly average liveweight gain (g/d) for pigs fed a commercial feed (CF), wheat bran (WB) or wheat bran supplemented with turnip (WB&T) or leucaena (WB&LL) or both (WM&LL&T).

Week	CF*	WB	WB&LL	WB&LL&T	WB&T	P-value	CV

1	181	176	125	100	93	0.17	56
2	176b	71c	162b	324a	245ab	0.00	35
3	255a	74c	188ab	150bc	102c	0.00	40
4	254a	119b	167b	171b	133b	0.02	35
5	245a	110c	155bc	188ab	157bc	0.01	32
6	352a	136b	210b	231ab	129b	0.03	51

Mean	244a	114d	168bc	194ab	143cd	0.00	21

abc Values on the same line followed by different letters differ (P<0.05) according to Duncan's Multiple Range Test.

Differences among weight gains were observed in week two, with both turnip-containing diets showing the highest gains although not significantly different from CF and WB&LL.

Daily weight gain means for the full 6 week period tended to be highest for the commercial feed treatment although they were not significantly different from those on the wheat bran diet containing both turnip and leucaena forage. The wheat bran diet was the poorest but growth rate on this diet was almost doubled (from 114 to 194 g/d) when the turnip and leucaena were added. The results suggest a synergistic effect of the turnip and leucaena in a diet of wheat bran.

Hot (1989) indicated that in a commercial Mozambican piggery, the native Landim pig averaged 287 g/day up to 56 kg on commercial feed while European breeds averaged 340 g. Despite the fact that the animals in the trial were considerably smaller than 56 kg at slaughter and that the experiment took place in the hot season, the gains with the commercial feed are not much lower than Hot's data.

Feed intake (Table 3) was lower on wheat bran than on commercial feed and although either turnip or leucaena reduced slightly the intake of bran, the total dry matter intake was always higher, especially when both forages were fed simultaneously (treatment WB&LL&T), confirming the synergism between the two supplements.

Conversion rate was within the range considered normal for European (3.5) and native (4.8) breeds in the tropics (Eusebio 1980). The interesting result was with the combined forage supplements for which the conversion was better (4.44) than on the commercial feed (4.51) despite the lower rate of liveweight gain (194 vs 244 g/day). The poorest conversion was with wheat bran alone (6.23).

Table 3: Feed intake and conversion for pigs fed a commercial feed (CF), wheat bran (WB) or wheat bran supplemented with turnip (WB&T) or leucaena (WB&LL) or both (WM&LL&T)

	CF*	WB	WB&LL	WB&LL&T	WB&T

Feed intake
(kg/d)
Leucaena			0.333	0.357
Turnip				0.536	0.555
CF	1.26
WB		0.807	0.711	0.710	0.711
Total DM	1.10	0.710	0.803	0.861	0.766
DM feed
conversion	4.51	6.23	4.78	4.44	5.36

The dressing percentage (carcass as % of liveweight) tended to be highest on the commercial feed and the wheat bran fed with leucaena and lowest on the diet with both supplements but effects of the supplements were not consistent. The percentages of digestive tract were higher on wheat bran alone and wheat bran supplemented with turnip (Table 4).

Table 4. Average carcass component (% of liveweight at slaughter) for pigs fed a commercial feed (CF), wheat bran (WB) or wheat bran supplemented with turnip (WB&T) or leucaena (WB&LL) or both (WM&LL&T)




Component	CF*	WB	WB&LL	WB&LL&T	WB&T
----------------	--------	--------	-------	---------	-------
Carcass	46.8	45.4	47.2	44.8	47.2
Heart	0.37	0.48	0.46	0.48	0.51
Kidneys	0.47	0.52	0.55	0.51	0.54
Liver	3.3	3.3	3.2	3.0	3.3
Digestivetract	8.8	10.5	9.3	9.8	11.3

The results of this experiment indicate that the inclusion of both leucaena leaves and forage turnip in a wheat bran diet improved growth and feed conversion over a wheat bran only diet. The use of the combined supplements gave results not statistically different from those on the control commercial feed. Although the data were obtained in a trial of rather short duration, the tentative conclusions are that inclusion of the selected fresh forages can be useful in overcoming nutritional deficiencies in weanling pigs fed wheat bran-only diets.

The wheat bran costs 28% less than commercial feed and both leucaena and turnip can be grown on the farm, thus the results with the two diets containing leucaena are particularly interesting from the point of view of reducing both feed costs and the dependence on the feed mill.

Gratitude is expressed to J A Kategile at ILCA for the mimosine analysis of the Leucaena leucocephala material. Appreciation is also extended to J Teixeira who donated animals for this experiment.

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