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THE UTILISATION OF WHITE AND YELLOW MAIZE BY SHEEP

 

J H HOON, M J HERSELMAN & B R KING

 

Grootfontein Agricultural Development Institute, Middelburg EC, 5900



INTRODUCTION

Maize, a carbohydrate-rich feed, is not only comparatively low in protein (8.5-10.5%), but incomplete in respect of its amino-acid balance for ruminants (Groenewald & Boyazoglu, 1980). It contains about 65% starch, is very low in fibre (2-3%) and has a high metabolisable energy value. Maize is also very palatable, owing to its relatively high content of fat (3-5%) and its crisp, flinty nature. A number of different types of maize exists and appears in a variety of colours of yellow, white and red. Yellow maize contains a pigment, cryptoxanthin, which is a precursor of carotene, and thus of Vitamin A. In the USA the yellow varieties are preferred for animal feeding. In the United Kingdom, however, white maize varieties are generally preferred for feeding animals as the pigmented grain tends to colour the carcass fat (McDonald, et al., 1966). According to Bull (1928) there is no difference between white and yellow maize regarding their chemical composition and feeding value. According to Morrison  (1936) yellow maize is more valuable than white maize for continuous feeding to animals not otherwise receiving sufficient Vitamin A. On the other hand, he reported that white maize is equal to yellow maize for all stock on green, actively-growing pasture or well-cured hay. Analysis by the Maize Board over many years revealed that very little or no differences exist in the chemical composition of South African white and yellow maize (Groenewald & Boyazoglu, 1980).

In South Africa mainly the yellow varieties are used for animal feeding. In years of over-supply of white maize, the lower prices increase its use as an animal feed. Observations by farmers indicated that there might be differences between the utilisation of white and yellow maize by sheep. The objectives of this study were to determine whether differences in intake and animal performance exist between sheep receiving white or yellow maize respectively, and also to determine whether sheep prefer one or the other when they have a choice.

 

EXPERIMENTAL PROCEDURES

The experiment was carried out in two phases. In Experiment 1, 40 young Merino wethers (± 24kg body weight) were randomly divided into eight groups of five animals each. Four groups received white maize and four groups yellow maize on an ad libitum basis in feeding troughs. All the groups also received 400g of milled lucerne hay/sheep/day in a self-feeder and were adapted on their respective diets for a period of two weeks prior to the commencement of the experiment. Maize intake per group was determined daily while the body weight of individual animals was recorded weekly. The experiment was carried out over a period of eight weeks.

In Experiment 2, 24 Merino wethers were randomly divided into four groups of six animals each. All four groups received both white and yellow maize in separate feeding troughs, as well as 400g of milled lucerne hay/sheep/day in a self-feeder. Intake of yellow and white maize for each group was determined daily. The white and yellow maize were switched daily between the two feeding troughs in each kraal in an attempt to eliminate a positional effect on intake. The chemical composition of white and yellow maize used in both trials were also determined.

Statistical analysis were performed using the GLM procedures of SAS (Littell et al., 1991). Data were analysed as a split-plot repeated measures design. In Experiment 1 the model statement included colour, day and colour x day interaction. The colour effect was tested using group within colour as error term. In Experiment 2 the model statement included colour, group and position of feeding trough, as well as all two-way interactions. The colour effect was tested using group as error term.

 

RESULTS

The chemical composition of the white and yellow maize used in both Experiments 1 and 2 are presented in Table 1.

 

Table 1. Chemical composition of white and yellow maize on a natural moisture basis

%

White maize

Yellow maize

Protein

8.94

8.81

Fibre

1.77

1.76

Ash

1.31

1.33

Calcium

0.02

0.02

Phosphorus

0.18

0.20

The chemical analysis confirmed that little or no differences exist in the composition of white and yellow maize.

The results obtained in Experiment 1 are presented in Table 2.

 

Table 2. Average daily maize intake, initial and final body weight and ADG of sheep receiving white and yellow maize respectively

 

White maize

Yellow maize

SE

P

Average daily maize intake/sheep (g)

622

732

9.47

0.0344

Initial body weight (kg)

23.31

23.46 

0.63

0.8706

Final body weight (kg)

31.55

33.05 

0.94

0.2677

ADG (g/day)

147

171

9.82

0.0927

These results indicated that the daily intake of yellow maize was significantly higher (P<0.05) than that of white maize. The final body weight and average daily gain (ADG) of sheep receiving yellow maize were also higher (P>0.05) than that of sheep receiving white maize. 

During the earlier part of Experiment 2, where the sheep had a choice between the two types of maize, differences in intake between white and yellow maize were relatively small and is reflected by intakes of 358 and 421 g/sheep/day respectively for the first week. During this period, however, the position of the feeding troughs had a large effect on intake, as reflected in intakes of 544 and 235 g/sheep/day for the near and far troughs respectively. During the last six weeks of the experiment, differences in intake of white and yellow maize were larger and were 329 and 508 g/sheep/day respectively. During this period the effect of the position of the trough was smaller, as reflected in intakes of 441 and 396g/sheep/day for the near and far troughs respectively. From the data it is evident that, as the experiment progressed, the sheep learned to select the feeding trough with the yellow maize, irrespective of its position. In Fig. 1 the average daily intake of white and yellow maize over the seven week feeding period, relative to the position of the feeding troughs, indicate that the intake of white maize on the days when it was supplied in the near trough (388g/sheep/day) was significantly higher (P<0.05) than from the far trough (277g/sheep/day). In the case of the yellow maize, however, the intake from the near (524g/sheep/day) and far troughs (473g/sheep/day) did not differ significantly (P>0.05).

 

Figure 1.  Average daily intake of white and yellow maize in relation to the position of the feeding troughs

 

The results from Fig. 2 indicate that, irrespective of the position of the feeding troughs, the intake of yellow maize (498g/sheep/day) was significantly higher (P<0.05) than that of white maize (332g/sheep/day).

 

 

The position of the feeding troughs in the kraal also had a significant effect (P<0.05) on intake, irrespective of the type of maize,  as indicated by intakes of 456 and 375g/sheep/day from the near and far troughs respectively (Fig. 3).

 

 

CONCLUSIONS

From the results of both Experiment 1 and 2 it is clear that the intake of yellow maize was significantly higher than that of white maize. These results support the belief of, and observations by, farmers that sheep preferred yellow maize to white maize. The higher intakes of yellow maize also had a positive effect on the performance of sheep, although it was not significant. The reason for the differences in preference is, however, still unclear but it is most probably linked to factors like palatability, texture, etc. It is also evident that the position of the feeding troughs in the kraal had a significant effect on intake, especially in the earlier part of the experiment.

In practice, when maize is included as a component of a diet and where no selection is possible, the differences in acceptability that occurred between white and yellow maize would most probably not have any effect on the intake of the diet. However, if maize is supplied separately as supplementary feeding to sheep, the differences in acceptability will have an effect on intake, animal performance and therefore on the economy of this feeding practice.  

 

REFERENCES

BULL, S., 1928. The Principles of Feeding Farm Animals. New York

GROENEWALD, J.W. & BOYAZOGLU, P.A., 1980. Animal Nutrition. Concepts and Applications.

LITTELL, R.C., FREUD, R.J. & SPECTOR, P.C., 1991. SAS System for Linear Models, Third Edition. SAS Institute Inc, Cary, NC.

MCDONALD, P., EDWARDS, R.A. & GREENHALGH, J.F.D., 1966. Animal Nutrition.

MORRISON, F.B., 1936. Feeds and Feeding. 20th Edition, Ithaca, New York