Effects of ensilage, added nitrogen and energy on the utilization of grain sorghum stover by beef cattle

M. B. Olayiwole and S. A. S. Olorunju
National Animal Production Research Institute
Ahmadu Bello University
Private Mail Bag 1096, Zaria, Nigeria

Summary
Introduction
Materials and methods
Results and discussion
Conclusions
References

Summary

Different combinations of urea, molasses and groundnut meal were individually fed to 60 Bunaji x Friesian crossbred heifers as a supplement to diets based on either dry sorghum stover or untreated/treated sorghum stover silages. Intake was increased by ensiling and by groundnut meal, and depressed by urea and molasses.

Introduction

More than 80% of the ruminant animals in Nigeria are located in the Guinea Savanna and Sahel zones in the north of the country where they are managed by the pastoral Fulani and agro-pastoralists. Cattle, sheep and goats increase their bodyweights during the wet season, but they lose a considerable amount of the gained weight during the subsequent dry season. Fodder conservation is not undertaken by the herdsmen while the excessively large numbers of livestock per family preclude the economic feasibility of supplementary feeding without government subsidy.

The Savanna and Sahelian zones are the major cereal (sorghum, Sorghum vulgare; millet; Pennisetum typhoides; maize, Zea mays) growing region of Nigeria. The grain is normally harvested by November leaving over 60% of the total dry matter in the field as crop residues. Traditionally, sorghum stovers are grazed as well as being used for fencing materials for dry season farm plots, and as part of the roofing structure for thatched houses. However, for several months, cereal crop residues, mainly sorghum stovers, constitute the principal source of fodder. They are so intensively grazed that by the end of March there is little or nothing left on the field (Van Raay et al, 1971).

Ways must be found to reduce considerably both livestock losses and the time taken to attain maturity or slaughter weight, even when only the cheapest feed resources, such as poor native pastures, crop residues and other roughages, are available. This might be achieved by utilizing the crop residues more efficiently so as to at least maintain animal body weight, and possibly obtain liveweight gains during the annual dry periods.

Animal performance on crop residues can be improved by chemical treatment and by supplementation (Sundstol and Owen, 1984). The objective of this study was to compare the effectiveness of different ways of ensiling dry sorghum stover, fed with and without nitrogen and energy supplementation, in increasing feed intake and cattle performance. Results from the investigation might pave the way for making recommendations for future use of sorghum residues in maintaining ruminants.

Materials and methods

The study was carried out at the headquarters of the National Animal Production Research Institute, Shika, Zaria, which is located at latitude 11°11' N and longitude 7°38' E at an altitude of 640 metres. It is within the northern Guinea Savanna zone with a 50 year annual rainfall mean of 1050 mm.

Sixty Bunaji (zebu) x Friesian/Holstein crossbred heifers and steers whose average age was 22 months, with a mean liveweight of 190 kg, were treated for both external and internal parasites. They were divided into six groups of 10 animals based on liveweight and age. Groups were randomly allocated to one of six diets. The diets were based on dry grain sorghum stover, untreated and treated grain sorghum stover silages, as listed below, and fed ad libitum, supplemented with or without different combinations of urea, molasses and groundnut meal, as follows:

1. Dry grain sorghum stover (93.4% dry matter) chopped with silage harvester;

2. Dry grain sorghum stover chopped as in treatment 1 and treated with calculated amounts of clean water to reduce the dry matter to about 62% before it was ensiled in a trench silo;

3. Dry grain sorghum stover was chopped as in treatment 1 and treated with calculated amounts of aqueous solution of 0.25% urea and 0.5% blackstrap molasses before it was ensiled as in treatment 2.

From the three sorghum stover-based diets, six rations were formulated and one group of animals was assigned to each of the following six treatments:

I. Control - ad libitum dry grain sorghum stover + mineral salts;
II. Ad libitum dry grain sorghum stover + groundnut meal + mineral salts;
III. Ad libitum dry grain sorghum stover + molasses + urea + mineral salts;
IV. Ad libitum untreated grain sorghum stover silage + mineral salts;
V. Ad libitum treated grain sorghum stover silage + urea + groundnut meal + minerals;
VI. Ad libitum treated grain sorghum stover silage + urea + molasses + mineral salts.

The animals were assigned to individual feeding pens in a latin square arrangement. Chemical composition of feed components is given in Table 1. Urea/molasses solution was administered by sprinkling the calculated amount on top of the dry sorghum stover and treated sorghum stover silage (treatments III and VI respectively) before feeding time. Groundnut meal (454 g) was given as a separate meal which was completely consumed before stover was offered ad libitum (about 120% of intake). Fresh water and a complete mineral lick (Table 2) were always available. Feeds offered and refused were recorded daily and samples taken for analysis according to the methods of AOAC (1970). There was a standardization period of 14 days followed by an experimental period of 60 days. Animals were weighed every 7 days.

Results and discussion

The chemical composition of the various rations used is given in Table 1. Ensilage significantly (P<0.05) improved dry matter intake (Table 3). This is attributable partly to texture, odour and palatability of the resultant silage from the stover and partly to the faster rate of digestion and passage of the silage digests compared with dry stover (Roes et al, 1974; Holmes, 1962). Addition of urea and molasses had a depressive effect on the intake of dry sorghum stover but this was not significant. On the other hand, urea and molasses had an associated non-significant effect on the intake of stover silage (Table 3). Pooled data for feed intake showed a highly significant (P<0.001) superiority for treatments containing groundnut meals over other diets, regardless of the form in which the stover was fed.

Although ensilage significantly improved dry matter intake, there was no corresponding benefit in animal productivity. This might indicate that the silage-based rations were used less efficiently than the dry stover. Similarly, dry stover supplemented with groundnut meal supported a higher average daily gain than the corresponding stover silage-based diet (80 vs 10 gm).

Analysis of variance showed that these small differences in weight gain were not significant and there were no significant interactions between added nitrogen and energy.

These results indicate that there is no economic merit in ensiling sorghum stover before it is fed. The addition of urea, however, may have a relative advantage over dry sorghum in maintaining liveweight while supplementing the stover with a protein source, such as groundnut meal, may increase daily gain. The effects of oilseed meal could be attributable to a contribution of by-pass or escape protein which would increase the yield of rumen microbial protein (Van Soest, 1982).

Conclusions

It may be concluded that crossbred cattle can, at the very least, be maintained, and possibly even obtain liveweight gains, during the annual dry periods by feeding cereal crop residues, such as sorghum stover, with limited additional protein and a complete mineral lick. These means are within the reach of the average livestock farmer in this part of Africa. However, it is desirable that if such a feeding system is adopted, the animals should be kept under either intensive or semi-intensive management, otherwise the levels of energy and protein available in the feed intake would not meet the animals' requirements for extensive grazing, with resultant losses in liveweight and even livestock.

Table 1. Composition of rations on dry matter basis.

Items	Treatments
	1	2	3	4	5	6
Dry matter	92.81	9.00	76.00	56.90	67.22	54.10
Crude protein (N x 6.25) %	4.75	8.20	6.75	4.43	7.50	6.57
NDF %	82.82	62.57	65.99	82.63	74.68	63.94
Non-CWC %	17.18	37.48	34.01	17.32	25.32	36.06
Hemicellulose %	28.75	24.43	24.22	28.68	27.22	22.00
ADF %	54.07	38.07	41.77	54.00	47.46	41.94
Cellulose %	46.36	32.16	35.81	45.98	40.29	35.83
Lignin %	7.72	5.91	5.96	8.01	7.17	6.11
Ash %	6.11	13.12	7.01	6.22	10.77	7.71

1 = Dry sorghum stover
2 = Dry sorghum stover + groundnut cake
3 = Dry sorghum stover + urea + molasses
4 = Untreated stover silage
5 = Untreated stover silage + groundnut cake
6 = Treated stover silage + urea + molasses

Table 2. Mineral composition of ration fed.

Treatments	Concentration (ppm)
	Na	Ca	K	Mg	Mn	Cu	Co	Zn	Fe	P
1	127.5	4100	11000	2100	59.58	4.0	4.0	120	300	140
2	137.5	5650	10600	3050	34.83	11.5	2.5	140	720	2875
3	187.7	6950	14000	2400	45.83	4.0	3.0	135	465	260
4	140.0	6400	10000	2150	96.25	5.0	2.0	115	740	300
5	132.5	4200	10400	3050	82.50	12.5	2.5	145	1165	2525
6	177.5	5950	13600	2350	73.33	4.5	3.0	140	525	1315

1 = Dry sorghum stover
2 = Dry stover + groundnut cake
3 = Dry stover + urea + molasses
4 = Untreated stover silage
5 = Untreated stover silage + groundnut cake
6 = Treated stover silage + urea + molasses

Table 3. Performance of cattle fed sorghum stover based diets.

Item	Treatments
	1	2	3	4	5	6	S.E.
Number of animals	10	10	10	10	10	10	10
Total DM intake/animal/day (kg)	2.50a	3.40b	2.27a	3.45b	4.65c	3.12b	0.51
Mean initial liveweight (kg)	187.13	186.25	190.75	191.75	188.62	188.25	7.64 n.s.
Mean final liveweight (kg)	184.25	191.00	188.00	185.62	189.00	184.75	7.94 n.s.
Average liveweight gain or loss/animal/day (g)	50.0a	80.0c	-50.0a	-111.0a	10.0b	-60.0a	26.96

Means within the same column with different superscripts are significantly different (P<0.05).

1. = Dry sorghum stover
2. = Dry sorghum stover + groundnut cake
3. = Dry sorghum stover + urea + molasses
4. = Untreated stover silage
5. = Untreated stover silage + groundnut cake
6. = Treated stover silage + urea + molasses

References

AOAC, 1970. Official methods of analysis. (11th edition). Association of Official Agricultural Chemists,
Washington DC.

Holmes W. 1962. A summary report on work on cattle nutrition carried out at Wye College. A report on work supported by the Milk Marketing Board.

Koes R M and Pfender W H. 1974. Increased utilization of bluestem hay with the addition of water or certain protein sources. Journal of Animal Science 38:662.

Sundstol and Owen, 1984.

Van Raay J G T and de Leeuw P N. 1971. The importance of crop residues as fodder: a resource analysis in Katsina Province, Nigeria. Samaru Research Bulletin 139.

Van Soest, 1982.