Some factors affecting on nutritive value of whole plant corn silage

H.M.A. Gaafar

Animal Production Research Institute, Agricultural Research Center, Dokki, Egypt.

Email:  gaafar356@hotmail.com

INTRODUCTION

In Egypt, the total planted area of corn crop was about 1 million feddans (420,000 hectare), but only 140 thousand feddans cultivated with yellow corn hybrids, the area of corn crop used as a silage was about 250 thousand feddans (National Campaign of Corn Crop Rising, 2007). Whole plant corn silage is a popular forage source for ruminants due to its high yielding properties, energy content, relatively high palatability and incorporating easily into TMR (Cherney et al., 2004). Recently, agronomists, nutritionists, and dairy producers have placed increased emphasis on factors affecting the nutritive value of whole plant corn silage (Bal et al., 2000).

Stay-green hybrids have asynchronous ear and stalk dry-down rates, therefore their ears turn brown and their kernels dry-down and mature faster than their stalks and leaves which remain green. The presence of this characteristic implies that the traditional relationship between whole plant silage, moisture and kernel milk line may no longer hold because it probably results in silages that have milk lines that are more advanced relative to whole plant maturity (Bagg, 2001). High stay-green rankings are genetically correlated with high stalk and leaf moisture contents (Bekavac et al., 1998). The stay-green characteristic hinders prediction of corn harvest dates with the kernel milk line because kernels get very mature while whole-plant DM remains under 30% (Thomas, 2001). Therefore, using kernel milk line to predict harvest dates for stay-green corn destined for silage may result in greater seepage (Lauer, 1998).

Corn hybrids with high stay-green rankings were found to have higher moisture and protein concentrations and lower starch content than average stay-green hybrids, but the fermentation process was unaffected by stay-green ranking. Stay-green hybrids should be harvested at about 34% DM (66% moisture) as this maturity stage gave the best combination of yield, nutritive value and low fungal counts. Due to the higher moisture content of high stay-green hybrids, they should not be harvested at DM concentrations below 30% particularly during rainfall or in wet years because excess moisture can cause undesirable fermentations (Adesogan, 2006).

The present investigation was undertaken to study the effect of hybrid type, cultivation season, stage of maturity and plant density on yield, fermentation characteristics, chemical composition, nutrients digestion, nutritive values and nutrients yields of whole corn plant silage.

MATERIALS AND METHODS

The current work was carried out at Sakha Animal Production Research Station, Animal Production Research Institute, Agricultural Research Center, Ministry of Agriculture, Egypt.

Corn hybrids: Nine commercial corn hybrids included 6 white hybrids (single way  crosses 10, 124 and Watania-4 and three way crosses 320, Nema-47 and Pioneer-3057) and 3 and yellow hybrids (single way  crosses 158 and Pioneer-3062 and three way crosses Pioneer-Dahab) were cultivated at 20, 25 and 30 thousand plants / feddan, during summer and nili seasons, harvested at milk, dough and hard stages of maturity and used to study the effects of cultivation season, type of hybrids, stage of maturity and plant density on yield, composition, fermentation, digestibility, nutritive value, yield of nutritive values and output of whole corn hybrids plant silage. Three plots with an area of 4.2 m² for each hybrid were taken randomly to estimate the yield of whole plant corn forage crop per feddan. Representative samples from each plot were taken to estimate the yield of ear, grain, cob, fresh stover, stalks and leaves.

Making silage: Corn hybrids were chopped into pieces with 1.0-1.5 cm of length. Five hundred kg of each chopped hybrid was ensiled in double plastic bags with 50 kg weight for each, pressed by hand to exclude the air and ensiled for eight weeks. The bags were reweighed after ensiling period to determine the yield of silage crop and ensiling weight losses.

Silage quality: Color and odor of silages were examined and samples were taken for chemical analysis. Silage samples were extracted using 20 g homogenized wet material with 100 ml distilled water in warm blender for 10 minutes (Waldo and Schultz, 1956). The homogenized sample was filtered through a double layer of cheesecloth and then the solution refilterated through a filter paper until it becomes perfectly clear. Silage pH was determined directly using 680 Orian digital pH meter. The concentrations of lactic, acetic, propionic, isobutyric, butyric, isovaleric and valeric acids were determined using gas chromatography according to the method of Erwin et al. (1961) and ammonia-N according to the method of AOAC (1990).

Digestibility trails: Digestibility trails were conducted to determine the nutrients digestibility coefficients and nutritive value of different corn hybrids silages using barky rams with an average body weight of 50±0.50 kg and 3±0.05 years of age (3 in each). Rams were housed individually in digestible carts for 15 days as a preliminary period followed by 7 days as a collection period. Digestible carts permitted total collection and separation of feces and urine. Rams were fed corn silage ad libtium in almost two equal meals daily at 8 a.m. and 4 p.m. The water was available in plastic buckets all day round. Samples of silages were taken at the beginning, middle and end of digestibility trails. Total collection of feces from each ram was weighed daily during the collection period and samples (10% by weight) of each daily collection were taken.

Chemical analysis: Samples of silages and feces were dried in a forced air oven at 65^oC for 48 hours, thoroughly mixed and representative samples were ground and chemically analyzed to determine the contents of CP, CF, EE and ash according to the methods of AOAC (1990).

Statistical analysis: Data was statistically analyzed using general linear model procedure adapted by SPSS for windows (2004) for user’s guide with a one-way ANOVA. Also, Duncan test within program SPSS was done to determine the level of significance between means.