Poster 4.1: Silages from tropical forages: nutritional quality and milk production - A. Aminah, C. Abu Bakar and A. Izham

INTRODUCTION

There is a need for silage making technology under local conditions, especially in those areas experiencing drier months or where monsoonal conditions restrict the routine cutting of forages. The need for silage making is even more significant for dairy cattle feeding, where the demand for uniform and high quality feed is of great importance. The tedious daily harvesting of green forages throughout the year also poses problems for small-scale producers, particularly when family labour is insufficient.

The objective of this paper is to evaluate the performance and suitability of six tropical grasses and three forage crops for silage making and a feeding trial for milk production.

METHODS

Nine species were planted for the first experiment: six grasses, namely setaria (Setaria sphacelata var. splendida); signal grass (Brachiaria decumbens); B. humidicola; MARDI Digit (Digitaria setivalva); Napier (Pennisetum purpureum); and three crops, namely maize (Zea mays); forage sorghum (Sorghum bicolor); and Sorghum almum. The grasses were cut at six-weekly intervals. Maize was harvested at 75 days, forage sorghum at 70 days and S. almum at 63 days after planting. Fresh samples were taken for analysis of DM and WSC (Dubois et al., 1956) and for silage making in the laboratory. The silage samples were analysed for pH, lactic acid (MAFF, 1973) and physical characteristics.

In the second experiment, six multiparous Sahiwal-Friesian cows in mid-lactation were used to test three dietary treatments in a double switch-over experiment (Cochran et al., 1941). Treatments were three levels of silage in the diet in direct substitution for cut fodder, as follows:

(a) fodder ad libitum;
(b) fodder+silage (1:1) ad libitum; and
(c) silage ad libitum.

In addition, each animal received 6 kg of concentrate once daily. Feed samples were taken once weekly and composited by cow-period. Feed intake and milk production were recorded daily.

RESULTS AND DISCUSSION

The mean values for WSC and DM in the crops and the quality of silage produced (pH and lactic acid content) are shown in Table 1. Maize and forage sorghum produced good silage with pH <4.0 and lactic acid levels of 2.72 and 3.7%, respectively (Table 1). For the grasses, it was found that, without additives, setaria and Napier could be turned into acceptable silage with pH 4.07 and 3.96, respectively. The pH of the grass silage was reduced with the addition of 4% molasses.

The nutritional composition of sorghum silage and guinea grass used in the second experiment are shown in Table 2. Treatment means for feed DM intake, milk yield and feed efficiency are given in Table 3. Intake of DM from roughage was highest (P<0.05) in treatment (b). The higher roughage intake of treatment (b) was attributed to a stimulatory effect of silage on intake. The difference in the total DM intake reflected differences in roughage DM intake. Expressed as percent body weight, total DM intakes in the respective treatments were within the range 2.0 to 2.4%. Average daily milk yield was higher (P<0.5) for cows fed sorghum silage compared with the control. The difference in milk yield was 13% between treatments (c) and (a). Mean feed efficiency value for cows on the silage-based diet was nearly twice as good as either treatment (b) or the control group (a) (Table 3).

Of the crops, forage sorghum and maize can be made into excellent silage without additives. It is suggested that grasses are cut at about six-weeks regrowth. Napier and setaria can be ensiled into reasonable silage, but the quality can be improved with the addition of 4% molasses before ensiling. From the second trial, sorghum silage appears to be a better feed than the average guinea grass commonly fed to lactating cows in Malaysia. This is reflected in its effect on milk yield and feed efficiency.

Table 1. Silage made from tropical grasses and forage crops

Notes: n.d. = not done

Table 2. Percentage chemical composition of feedstuffs

Table 3. Feed intake and efficiency and milk yield for the different treatments

Notes: The values within rows with different letters are significantly different (P<0.05)

REFERENCES

Dubois, M., Gilles, K.A., Hamilton, J.K., Rebers, P.A., & Smith, F. 1956. Calorimetric method for determination of sugars and related substances. Anal. Chem. 28: 350-356.

MAFF [Ministry of Agriculture Fisheries and Food (UK)] 1973. The determination of lactic acid in silage juice. Manual of Analytical Methods. Technical Bulletin 27.

Cochran, W.G., Autrey, K.M., & Cannon, C.Y. 1941. A double changeover design for dairy cattle feeding experiments. J. Dairy Sci., 24: 937-951.