The objective of this study was to evaluate the nutritional quality of fresh corn plant and corn silage at two maturity stages; one third milk line and two third milk line of selected hybrid corn varieties; “Sampath”, Pacific, Super and Giant. Representative samples were obtained from different varieties at each maturity stage from fresh whole plant and silage for proximate analysis. Higher crude protein contents were recorded in varieties Super, “Sampath” and Pacific compared to Giant whereas, higher energy contents were recorded in varieties Super, “Sampath” and Giant compared to Pacific. Higher amount of crude protein was observed in fresh forage than silage. However, energy contents were higher in silage compared to forage. Milk line two-third kernel stage showed the highest crude protein contents while milk line one-third kernel stage had a higher energy and dry mater contents. Thus, it can be concluded that the nutrient contents in corn depend on variety, maturity stage and form of feeding.
Dairy industry in Sri Lanka is mainly comprised with cattle and buffaloes, and total milk production was 384 mill. L in 2016 (DCS, 2017). It is far below the potential production and local milk production is not sufficient to compensate the total demand of the country. In order to bridge the prevailing gap between local demand and supply, it is needed to improve the dairy cattle production in the country. Poor feeding management has been one of the major reasons for low milk production (Perera and Jayasuriya, 2008). Unavailability of high quality forages, seasonal abundance and unawareness of dairy farmers are some of the underlining courses. Forages are major component in the feeding rations for ruminants, especially for dairy. Corn, a food and a forage plant is the most widely cultivated cereal in the world after rice. However, unlike the other two major cereals, corn is mostly used as animal feed, with only 15% of grain used for food (Awika et al., 2011). It recently becomes one of the basic feed for ruminants, particularly cattle, in temperate countries. Corn silage is used to increase lactation length and stocking rates and manage risk (Bates, 2015). Feed products from corn are characterized as high energetic nutrient feed (CTA, 2012). Corn silage is easily ensiled and results in palatable feed with relatively consistent quality and higher energy content than other forages (Allen et al., 2003).
Corn is a most familiar, high yielding crop in Sri Lanka and cultivates during both Yala and Maha seasons. Major purpose of cultivating corn is to use as a feed ingredient and fresh cob for human consumption. Corn silage prepared with whole plant is highly palatable and can be used in cattle rations instead of expensive concentrates. Recently corn silage is becoming one of the basic feed for dairy cows in commercial farms in Sri Lanka. However, still it has not been identified the possible maturity stages to harvest the crop for silage preparation and nutritional qualities under Sri Lankan conditions. Therefore, this study was performed to evaluate the nutritional quality of fresh corn plant and silage at two maturity stages of selected hybrid corn varieties; Giant (Pioneer hybrid 30Y87), Pacific (PAC999), “Sampath” (local hybrid) and Super (Pioneer hybrid P4199) available in Sri Lanka.
Material and Methods
Experimental Design and Forage Management
The experiment was conducted at Faculty Agriculture, Rajarata University of Sri Lanka, during Yala season. The experimental design was Randomized Complete Block Design (RCBD) in factorial arrangement of treatments (four corn varieties × two harvesting stages x two forms of feeding) with four replicates. Each plot consisted of six rows of corn in 25 m length and 12.5 m width. Raised beds were prepared and each bed was separated by drains. Seeds were sown using 60 x 60 cm spacing. Three seeds were placed per hole and one plant was thinned out after 3 weeks. The four hybrid corn varieties used were Giant (Pioneer hybrid 30Y87), Pacific (PAC999), “Sampath” (local hybrid) and Super (Pioneer hybrid P4199). Fertilizer was applied according to the recommendation of Department of Agriculture (DOA, 2015). After 4 weeks of planting, fast growing weeds were removed manually. Adequate amount of water was provided with 5 – 7 days intervals. Recommended weedicides and fungicides were used to control shown symptoms. Corn were harvested at two stages of grain maturity; reduction of the milk line to one third of the kernel (1/3 ML) and two third of kernal (2/3 ML). Time of harvest was defined by visual evaluation of the milk line of the kernel in 1/3 ML and 2/3 ML for 75 days and 90 days after planting, respectively and the whole plants were harvested at 20 cm above the ground. Fresh and silage forms of corn were evaluated for nutritional aspects. Ten to twelve plants from each plot were randomly taken to compose fresh whole plant samples and same numbers of plants were taken for silage preparation.
Corn plants were cut in to 1 cm length and kernels were broken in to the multiple pieces and cores were broken in to the thumb nail size pieces. As quickly as possible, chopped particles were filled in to polythene bags and packed well to decrease the amount of air pockets in the silo. Bags were sealed tight to exclude outside oxygen which were kept for 45 days for proximate analysis.
Samples of fresh forage and silage were dried in an oven at 60°C until constant weight and ground firmly to pass a 2 mm sieve. Dried, ground samples were stored in labeled glass bottles for further analysis. Samples were analyzed for dry matter (DM), crude protein (CP), crude fiber (CF), crude fat and ash contents according to AOAC procedures (2005). Gross energy contents of samples were determined by bomb calorimeter.
Data were analyzed using two way Analysis of Variance (ANOVA) procedure of Statistical Software for Data Analysis ver. 9.0 (SAS, 2002). Mean separation was done by Tukey’s Studentized Range Test (TSRT) and statistical significance was declared at P < 0.05.
Results and Discussion
Proximate Compositions of Fresh Forage and Silage
There was a significant association (P < 0.05) among the factors namely variety, harvesting stage and form of feeding on CP, CF, ash and GE contents (Table1).
Table 1: Interactions among corn variety, maturity stage and feeding form on proximate composition
|DM %||CP %||CF %||NFE %||Ash %||GE kcal/kg|
|Variety x Stage x Form||NS||S||S||NS||S||S|
|Variety x Stage||NS||S||S||NS||NS||S|
|Variety x Form||S||S||S||NS||S||S|
|Stage x Form||S||S||NS||NS||NS||S|
S – Significant (P < 0.05), NS – non-significant (P > 0.05)
Two way associations between variety and stage was significant (P < 0.05) for all analyzed proximate components except NFE. Interaction between variety and form was significant (P < 0.05) for DM, CP, CF, ash and GE contents. Two way associations between stage and form was significant (P < 0.05) for DM, CP and GE contents.
Nutritional Composition Changes among Corn Varieties
Ullah et al. (2010) stated that corn varieties vary greatly in term of nutritional composition. Dry matter and NFE contents were similar (P > 0.05) among varieties (Table 2).
Table 2: Nutritional composition changes among varieties
a, b Means within the same row with different superscripts are significantly different (p < 0.05)
*SEM – Standard error of means
However, significantly higher (P < 0.05) crude protein contents were recorded in varieties Pacific, “Sampath” and Super compared to variety Giant. The highest (P > 0.05) crude fiber content was observed in variety “Sampath” compared to varieties Giant and Super. There were no differences (P > 0.05) in ash contents among varieties; Giant, Pacific and “Sampath”, though the highest ash content was observed in variety Super compared to Pacific and “Sampath”. Gross energy contents were significantly higher (P < 0.05) in varieties Giant, “Sampath” and Super compared to Pacific. The variation of nutritional composition observed may be due to genetics which may influence the individual chemical composition and weight distribution of the endosperm and hull of the kernels and leaf and stem characteristics.
Nutritional Composition Changes between Harvesting Stages
Nutrient compositions were (P < 0.05) changed with harvesting stages (Table 3). Higher (P < 0.05) DM and GE contents were recorded in corn harvested at 1/3 milk line stage compare to 2/3 milk line stage. However, the CP contents were significantly higher (P < 0.05) when corn was harvested at 2/3 milk line stage compared to 1/3 milk line stage. Crude fiber, NEF and ash contents were not significantly different (P > 0.05) between two harvesting stages.
Table 3: Nutritional composition changes between harvesting stages
|Nutritional Composition||Harvesting Stage||SEM*|
|1/3 ML||2/3 ML|
|CP %||7.21a||7.67 b||0.12|
a,b means within the same row with different superscripts are significantly different; (P < 0.05); *SEM – Standard error of means
Forage quality depends on climate and plant maturity. Proceeding with maturity, proportion of vegetative components are decreased hence quality will be reduced. Grain filling also decreased with decreased leafy materials (Ma et al., 2006). Hence silage prepared with correct maturity stage enhance the nutritional quality (Allen et al., 2003). As Wiersma et al. (1993) stated the nutritional quality of silage depends upon the stage of maturity at the time of harvest. Amodu et al. (2014) also reported that harvesting the two maize accession at different maturity stages make significant differences in nutritional composition.
Nutritional Composition Changes between Forms of Feeding
Nutritional composition was significantly different (P < 0.05) with form of feeding (Table 4).
Table 4: Nutritional composition changes between fresh whole plant and corn silage
|Nutritional Composition||Form of Feeding||SEM*|
|Fresh Whole Plant||Silage|
a,b means within the same row with different superscripts are significantly different ; (P < 0.05) ; *SEM – Standard error of means
Dry matter, CF and GE contents were significantly (P < 0.05) higher in corn silage compared to fresh forage. However, significantly higher (P < 0.05) CP content was recorded in whole corn plants compared to corn silage. Nitrogen Free Extract and ash contents were similar (P > 0.05) between two forms. Amodu et al. (2014) also observed some changes in nutritional composition of forage and silage of the two maize accessions.
Nutrient contents in corn depend on variety, harvesting stage and form of feeding. Nutritional value is higher in fresh corn plants compared to corn silage. Harvesting corn at 1/3 ML stage gives nutritionally better feed compared to 2/3 ML stage.