Rumen degradation of maize stover as influenced by Leucaena hay supplementation

M A Kabatange and C M Shayo

Livestock Production Research Institute, Mpwapwa, Tanzania

Summary

The nylon bag technique was used to study the rumen degradation characteristics of maize stover in Zebu steers as influenced by the rumen environment. The treatments were: chopped maize stover fed alone (MS); plus 2 (L2) or 3 (L3) kg/d of leucaena hay; plus 2 kg/d of leucaena hay and 1 kg/d maize bran (L2MB); and a control treatment (C) where the steers grazed on standing hay. A vitamin- mineral mixture was dissolved in drinking water and supplied free choice on all treatments.

Rate of degradation of maize stover was improved with all levels of leucaena hay supplement. After 24 hours incubation, more than 75% of the degradable fraction had been fermented in the supplemented diets while only about 50% was degraded in the control diet. This implied faster rate of passage and hence more feed intake.

KEY WORDS: Rumen degradation, maize stover, leucaena, rumen ecosystem, Tanzania.

Introduction

In Tanzania cereal crop residues assume great importance in ameliorating the feed deficit. Most stovers are fed to animals in situ (in the farm) but some farmers harvest and store these residues to feed to their animals later in the year. For the latter group it becomes easy to manipulate the feeding so that there is maximum utilization of the stover.

The grain stovers have feeding values equal to that of hay cut at the end of the rains (French 1983). The most limiting factor to animal performance fed on cereal stover appears to be that of dietary protein. Supplementation with high protein forages has been shown to increase the efficiency of utilization of crop residues by ruminants (Mosi and Butterworth 1985; Kang et al 1982, cited by Banda and Ayoade 1986). According to Preston and Leng (1987), part of this effect is due to enhancement of rumen function because small quantities of highly digestible green forage provide essential nutrients for the rumen microbes.

Leucaena leucocephala is a tropical forage legume which is rich in protein and minor nutrients, and therefore has potential as a supplement for ruminants fed nutritionally imbalanced and low digestibility roughages such as maize stover. It is gaining popularity in Tanzania and particularly in the semi-arid zone where it has been developed for multipurpose reasons. Many farmers have planted the trees and would benefit from a feeding programme in which leucaena was included.

The objectives of this study were to:

• Study the rate and extent of rumen digestion of maize stover when supplemented with various levels of leucaena meal.
• Determine optimum levels of leucaena in a maize stover diet.
• Establish if a high energy supplement would be an advantage when combined with the leucaena.

Materials and methods

Maize stover from individual farmer plots around the institute was collected after the grain harvest, stacked and kept in a shed. At the start of the experiment the maize stover was chopped using a cutlass and supplied ad libitum to two rumen fistulated steers. A salt mixture was sprinkled on the stover. The treatments were:

Chopped maize stover (MS); chopped maize stover + 2 kg/d leucaena leaf meal (L2); maize stover + 3 kg/d leucaena leaf meal (L3); maize stover + 2 kg/d leucaena leaf meal + 1 kg/d maize bran (L2MB); and a control diet of normal grazing (C). With all diets, salt and a vitamin mineral mixture was supplied. The two steers were maintained on each feeding regime for two weeks at the end of which milled samples of whole maize stover were incubated in nylon bags in their rumens and removed at 6, 12, 18, 24, 48 and 72 hours using the procedures recommended by Orskov et al (1980). Maize stover and leucaena leaf meal were analyzed for dry matter, nitrogen, ash and fibre content.

Results and discussion

The nitrogen content of leucaena was 2.22% while that of maize stover was 0.38% (Table 1). Rumen degradation rate of the maize stover is shown in Table 2.

Leucaena supplementation had a positive effect on the rate of degradation of the maize stover in all diets. There was no advantage when the level of leucaena was raised from 2 to 3 kg/d; while there was a suggestion that degradation of the maize stover was reduced when maize bran was also given.

Table 1: Chemical composition of maize stover and leucaena hay (ash, N and NDF as % in dry matter).
Feed	DM	Ash	N	NDF
Maize stover	91.9	7.9	0.38	73.3
Leucaena hay	90.7	16.8	2.22	33.5
Maize bran	95.0	—	2.00	—

Table 2: Degradation of maize stover incubated in the rumen of steers receiving leucaena hay alone or with maize bran
	Treatment
Time hours	Maize stover alone	Maize stover+2kg leucaena hay	Maize stover+3kg leucaena hay	Maize stover +2kgleucaena +1kg maize bran	Normal grazing
6	8	21.7	19.0	13.4	14.5
12	13.5	28.1	30.1	25.3	20.6
18	23.3	37.3	37.3	32.9	30.6
24	27.3	45.5	41.2	38.8	35.2
48	42.2	58.8	54.7	51.7	49.7
72	55.8	59.1	59.1	59.3	58.6
a	3.0	14	10	7.5	8
p	13.5	27	27	21.5	20.5
c	0.022	0.034	0.043	0.032	0.028

The greater rate of degradation of the maize stover incubated in the steers on the grazing treatment, compared with unsupplemented maize stover, indicates that either the hay was better balanced than the stover or the animals had an opportunity to select, hence creating a better rumen environment.

Voluntary intake of roughages in ruminants is affected by the rate at which digestion occurs. In this study the higher rate of digestion achieved by supplementation with leucaena implies that this would also be reflected in better animal performance.

Conclusion

Cereal stover and poor quality hay form the bulk of the diet of ruminants in Tanzania. Utilization of these feed resources can be optimized by supplementing them with small quantities of nutrient-rich forages such as those derived from legume trees, which are either inherent in the area or introduced.

Acknowledgement

The authors are greatful to M L Kusekwa for the leucaena leaf hay; and to R Kamate for stover collection. The laboratory staff R Mwassa, M Mpiri, V Mwiwula, G Chipanjilo and R Kasiga are thanked for their co-operation.

References

Banda J L L and Ayoade J A 1986 Leucaena leaf hay (cv. Peru) as protein supplement for Malawian goats fed chopped maize stover. In: Towards Optimal Utilization of Agricultural By-products for Livestock in Africa. Proceedings ARNAB workshop, Alexandria, Egypt. ILCA: Addis Ababa.

French M H 1983 Feeding values of stover from maize, millet and Bulrush millet. East African Agriculture Journal 9:88.

Mosi A K and Butterworth M H 1985 The voluntary intake and digestibility of diets containing different proportions of tef (Eragrostis tef) straw and Trifolium tembense hay when fed to sheep. Tropical Animal Production 10: 19-22

Orskov E R, Hovell F D DeB and Mould F 1980 The use of the nylon bag technique for the evaluation of feedstuffs. Tropical Animal Production 5:195-213

Preston T R and R A Leng 1987 Matching Ruminant Production Systems with Available Resources in the Tropics and Sub-Tropics. Penambul Books: Armidale.