| Abstract | Silaža kukuruza zauzima veliki dio obroka mliječnih krava i tovnih goveda u RH, odnosno,
znatno pridonosi podmirenju dnevnih potreba životinja za hranjivim tvarima i energijom.
Hranjivost biljke kukuruza teško se procjenjuje zbog vrlo različitog morfološkog i kemijskog
sastava glavnih dijelova, te vrlo različite razgradljivosti hranjivih tvari u buragu. Zrelost
biljke kukuruza i njezina zrna, prinos zrna i dijelova biljke, te ukupni i pojedinačni sastav i
struktura vlakana čimbenici su koji utječu na razgradljivost, te posljedično i na ukupnu
hranjivu vrijednost silažnog kukuruza. Navedene promjene osobina kukuruza povezane su s
različitim vremenom sjetve i košnje, te je cilj istraživanja utvrditi promjene u kemijskom
sastavu, razgradljivosti i energetskoj vrijednosti kukuruza za silažu u različitim stadijima
zrelosti, utvrditi promjene u masenom udjelu i hranjivosti dijelova biljke kukuruza, te odrediti
optimalni stadij zrelosti za spremanja silaže cijele biljke kukuruza, obzirom na njen najveći
potencijal za proizvodnju mlijeka. Korišten je hibrid kukuruza Bc 304 (BC Institut, Zagreb)
sijan u dva perioda 01.05. i 17.05 na parceli Fakultetskog dobra Maksimir. Uzorci kukuruza
su uzimani u tri stadija zrelosti, prema vizualnoj procjeni po "mliječnoj crti" (1/3, ½, 2/3).
Uzgoj kukuruza različitih stadija zrelosti uzrokovao je povećanje udjela zrna sa zrenjem
biljke, uz istovremeno opadanje udjela vegetativnih dijelova; stabljike i njenih dijelova
(donjeg i gornjeg dijela) i listova (donjih i gornjih), dok su kod ostalih vegetativnih dijelova
kukuruza promjene samo relativne (p≥0,05). Samim porastom zrna u ukupnoj masi silažnog
kukuruza dolazi samo do relativnog povećanja NEL-a (p≥0,05). Starije biljke obično imaju i
nešto veći sadržaj škroba, bez negativnog djelovanja na razgradljivost vlakana (NDV), te se
stoga omogućava farmerima da odgode vrijeme košnje kukuruza do 2/3 (do 40% ST)
mliječne linije čime dobivaju zreliji kukuruz s više škroba, ali bez štetnog utjecaja na
razgradljivost vlakana, a s druge strane silažna masa je još uvijek dovoljno vlažna za
odvijanje optimalne fermentacije, koja rezultira kvalitetnom silažom. Osim utjecaja na
navedene parametre hranjivosti biljke kukuruza za silažu, kasnije košenog kukuruza, pri
zrelosti od 2/3 mliječne linije, potencijalno osigurava i najvišu proizvodnju mlijeka hranimo
li krave silažom od takvog kukuruza. |
| Abstract (english) | The introduction points to the importance of corn silage in the diet of dairy cows and
heifers, and gives a brief overview of the factors, which influence the nutritional value of
whole plant silage corn. One of the main factors on which it depends nutrition and
fermentation of corn silage is the stage of maturity of the crop at harvest time. Under field
conditions, stage of maturity is usually determined by the development „milk line” of grain
since it is robust and reliable indicator of accumulation and dry matter content in the crop of
maize intended for the production of silage from the whole plant.
Literature Review provide us a detailed overview of the results of domestic and
foreign research on the influence of stage of maturity on the yield of silage mass and
nutritional value of silage maize. From these results it is clear that the harvest at different
stages of maturity of crops leads to significant changes in nutrient contents of corn silage, but
the mechanism underlying these changes is relatively poorly understood. Nutritional value of
the whole plant corn silage is difficult to determine because of the very different chemical
compositions in major parts of the maize plant (stem, grain and cob). Furthermore, relatively
well researched impact of stages of maturity on the nutritional value of the whole plant corn
stalks and grain somewhat, but there are almost no data on changes in other parts of the plant
such as leaf blades and leaves sleeves, cobs, husks and shank of corn cobs.
Materials and Methods are appropriately selected and fully integrate the hypotheses
testing. In the research are used standard and modern methods for the analysis of plant
material, which makes this research repeatable and verifiable. Material and methods are
described in accordance with established objectives and research hypotheses. Original
research results are obtained by conducting a two factorial experiment for one year at test
field Maksimir. Factors study were periods of sowing (optimal and subsequent) and stage of
maturity of corn grain. Due to organizational and technical reasons, field trial instead of
randomized complete block design was set up by split-plot with three replicates. For research
purposes maize hybrid Bc 304 was grown under intensive cropping. Samples of corn to
determine the nutritional and other studied traits were taken at three stages of maturity: at 1/3
stage of the milk line, 2/3 stage of milk line and at physiological maturity. Representative
dissection samples of plants are separated into sections as follows: the lower part of the stem
(part of the stem below the node from which emerges the uppermost cob), the upper part of
the stem, the leaf blades of the lower leaves (leaf blades of leaves below node from which
emerges cob), the leaf blades of upper leaves, sleeves of lower and upper leaves, leaf husks,
cob shank, cob and grain. On these parts as well as on samples of the whole plant was
determined structural fiber content, dry matter, ash, crude fat, crude fiber, crude protein and
calculative soluble carbohydrates, neutral and acid detergent fiber and acid detergent lignin
according to AOAC standards. Starch content in the grain and dry matter digestibility are
determined of plant parts as well as the whole plant. Net energy for lactation is calculated and
estimated overall nutritive value expressed in kilos of milk produced per ton of corn silage
and kilos of milk per unit area. Data processing was performed by appropriate model of
analysis of variance and post hoc tests to compare means after a significant F-test.
The results are logically discussed in relation to the hypothesis and research goals
without unnecessary repetition of results. The results are compared with the results of other
domestic and foreign researchers. The author in the discussion pointed to the advantages and
disadvantages of the applied methodology for sampling corn silage. The results are consistent
with previous research and critically explained with those results that are in contradiction
with them that is explained by the specific environmental conditions in which is performed
field experiment. Finally, it is concluded that the chemical composition, digestibility and
energy value of the parts and the whole plant maize were not significantly changed for silage
maize grown in two planting. In contrast, in the later stages of grain maturity, there is a
significant increase in the content of lignin in the stalk and cob, and increased content of fiber
fractions in most parts of the maize plant, especially in the stalk and leaf sleeves, the cob and
husks. With the maturing plants had a decrease ash content, crude fat and proteins in the leaf
blades of the upper and lower leaves, while expected changes in fiber fraction are not
statistically significant. Consequently, there was a major reduction in dry matter digestibility
of leaf sleeves, husks and cob. However, this decline in digestibility of most vegetative parts
did not affect the digestibility of whole plant corn due to the compensatory effect of
increasing the content of highly digestible grain in the plant and starch in the grain. With
maturing plants expected to increase the yield of the whole plant as a result of increased
weight and grain yield. Despite the increase in weight of grain and starch accumulation in
grains in the later stages of grain maturity, there was not found an increase of the energy
value. This is because at the same time there was increased content of non-degradable lignin
in the lower part of the stem. Significant growth of potential milk production per unit area
was determined for silage maize in the later stages of maturity, but not as a result of changes
in nutritional plants but due to the increased yield of whole plant corn. |
