Evaluation of dry matter yield, chemical composition and in vitro dry matter digestibility of silage from different maize hybrids

A Kamalak*, A Erol, Y Gurbuz, O Ozay, O Canbolat* and R Tumer

Kahramanmaras Sutcuimam Univercity, Faculty of Agriculture, Kahramanmaras, Turkey
*Bursa Uladag University, Faculty of Agriculture, Bursa, Turkey
a_kamalak@hotmail.com

 

Abstract

In this study four maize silages from different hybrids were evaluated in terms of chemical composition, dry matter yield (DMY), metabolizable energy (ME) and in vitro dry matter digestibility (IVDMD).

Crude fibre (CF) of the silages ranged from 23.0 to 25.4%.  There were no differences between silages in terms of dry matter (DM), crude protein (CP) and ether extract (EE). Dry matter yield (DMY) ranged from 16425 to 19577 kg/ha^-1.
 

 It was concluded that there were significant differences in crude fibre, ash, DMY, IVDMD and ME between four the hybrids. The rank order in terms of metabolizable energy yield (MEY) or digestible dry matter yield (DDMY) was the same and as follows: Otello> Golden>Broskov>Maverik. 

 

Otello had a high index value. Therefore it can be recommended for silage production. However,  feeding trials with ruminants are required to see how these differences can affect animal performance such as milk or meat production.

 

Key Words: Digestibility, dry matter yield, maize hybrid
 

Introduction

 

Maize silage is used extensively in diets for dairy and beef cattle in most part of the world. Maize silage is normally a high energy forage with high dry matter yield relative to the other forage crops (Coors 1996). Hybrid selection is one of the most important management decision which farmers have to decide every year.

 

The introduction of new maize hybrids has provided new raw materials with a range of nutritional characteristics. Large differences in nutritional value may exist between silage made from different maize hybrids (Hunt et  al 1993).  In addition to the dry matter yield the digestibility and metabolizable energy value of silages are important parameters in ration preparation in practice. The two stage rumen inoculum-pepsin method (Tilley and Terry 1963) and Menke gas production method (Menke et  al 1979) have been established as accurate predictors of IVDMD and ME value of forages respectively.

 

The aim of this study was, therefore, to evaluate the dry matter yield, chemical composition, in vitro dry matter digestibility and metabolizable energy value of silage from different maize hybrids.

 

Materials and Methods

 

Silage production procedure

 

Four commercial maize hybrids were planted in 2002 in Osmaniye, Turkey. Plot sizes were 10*10 m. Planting density was 70 000 ha^-1 for all hybrids. The fertilizers used were: 100 kg/ha^-1 P₂O₅ and 180 kg/ha^-1 nitrogen.

 

A representative sample of the maize plants was harvested and weighed to determine dry matter yield (DMY) (kg/ha^-1). All plants were passed through a commercial silage chopper, and a representative sample of the fresh material was ensiled in mini experimental silos (plastic jars) with a capacity of 5 kg (Photo 1). After approximately two months storage, the silos were opened. Representative samples were dried at 60 ^°C in a forced-air oven and ground to pass a 1 mm screen for chemical analysis.

 

 

Photo 1: The plastic jars used as mini-silos

Chemical analysis

 

DM contents of silages were determined by drying the samples at 105 ^°C overnight. Ash was determined  and ash by igniting the samples in a muffle furnace at 525 ^°C for 8 h. Nitrogen (N) content was measured by the Khjeldal method (AOAC 1990). CP content was calculated as N*6.25. Crude fibre (CF) and ether extract (EF) were determined by the method of AOAC (1990). The buffering capacity was determined by titration of a 10 ml of water extract with 0.1M HCl and 0.1 MNaOH (Playne and McDonald 1966). The pH was determined using a combination electrode of a pH meter ( Pye UNICAM, PHILLIPS).

 

Gas production procedures

 

For the determination of ME and IVDMD rumen fluid was obtained from two fistulated sheep fed twice daily with a diet of alfalfa hay (60%) and concentrate (40%). The samples were incubated with rumen fluid in calibrated glass syringes following the procedures of Menke and Steingass (1988). The sample (0.200 g dry weight) was weighed in triplicate into calibrated glass syringes of 100 ml. The syringes were pre-warmed at 39 ^°C before the injection of 30 ml rumen fluid-buffer mixture into each syringe followed by incubation in a water bath at 39 ^°C. The syringes were gently shaken 30 min after the start of incubation and every hour for the first 10 h of incubation. Gas production was recorded 24 h after incubation. The estimated ME value (MJ/kg DM) was calculated using the equations of Menke and Steingass.(1988) as follows:

ME (MJ/kg DM) = 2.20 + 0.136*GP + 0.057*CP + 0.0029*(CP⁾²

Where:    GP is 24 h net gas production (ml/200 mg),

               CP = Crude protein

 

Metabolizable Energy Yield (MEY) (kg) = DMY*ME

 

In vitro dry matter digestibility

 

Samples of dry forages (0.5 g) were subjected to a 48 h digestion period with the McDougall's buffer/rumen fluid mixture in sealed glass bottles followed by 48 h digestion with pepsin in weak acid (Tilley and Terry 1963).

 

IVDMD (%) = (DM input -DM remaining undigested) / (DM input)*100

Digestible DM yield (DDMY) (kg/ha^-1) = DMY*IVDMD

 

Statistical analysis

 

Analysis of variance (ANOVA) was carried out on chemical composition, DMY, IVDMD, ME, MEY and DDMY values using the General Linear Model (GLM) of "Statistica for Windows" (Statistica 1993). Significance of differences between individual means were identified using the Tukey's multiple range test (Pearse and Hartley 1966).

 

Result and discussion

 

There was a considerable variation between silages in terms of chemical composition and estimated parameters of nutritive value (Table 1). The crude fibre and ash contents of the silages were similar to those obtained by Stallings et  al (1982). CP and pH, values obtained in this study were in agreement with those reported by Meeske et  al (2000). All silage samples had a low pH and were well preserved. 

The IVDMD and ME values obtained in this study (Table 2) were in agreement with those reported by Meeske et  al (2000). Silage DMY varied between 16425 and 19577 kg/ha^-1. Generally the differences between silages from different maize hybrids were small in terms of chemical composition whereas the differences between silages in terms of DMY, ME and IVDMD were large.

High yields of maize biomass are necessary to reduce production cost and forage requirements. However, for dairy cattle small increases in milk production due to higher digestible energy content and (or) intake may have a greater economic importance than yield differences among maize hybrids (Allen 1996). It may be advantageous to sacrifice some yield potential for increased maize silage digestibility.

 

Conclusion

 

It was concluded that there were significant differences in crude fibre, ash, in vitro dry matter digestibility and estimated ME content among four maize hybrids available in Turkey. 

 

 

References

 

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Meeske R, Basson H M, Pienaar J P and Cruywagen C W 2000 A comparison of the yield, nutritional value and predicted production potential of different maize hybrids for silage production. South African Journal of Animal Science 30(1):18-21.

 

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