Forage turnip (Brassica rapa) harvested in different phases of vegetative stage and ensiled with the additives of molasses and barley and the effects of additives on silage quality, in vitro digestibility, and energy content

Authors: SERHAT YILDIZ, SUPHİ DENİZ, FATMA ÖZKAN, ÇAĞRI KALE

Abstract: This study was conducted to determine the silage quality, in vitro digestibility and energy content of forage turnip (Brassica rapa) ensiled with molasses or ground barley. Forage turnip was harvested at three different stages: the beginning, middle and end of the flowering period, and it was ensiled with no additive (control), 5% molasses or 4% ground barley. In the trial, pH, nutrient contents, ammonia nitrogen (NH$_{3}$-N) contents, volatile fatty acid (VFA) contents, Fleig scores, in vitro digestibility and energy content were determined. It was observed that the effect of the vegetative stage on the difference between the groups was significant (p < 0.05). Accordingly, with the progression of the vegetative stage, the contents of dry matter (DM), organic matter (OM), ether extract (EE), neutral detergent fiber (NDF) and acid detergent fiber (ADF) showed an increase while a decrease was observed in crude protein (CP). The effects of the additives on the difference between the groups were found to be significant except for the CP parameter (p < 0.05). Molasses and barley addition to the silages increased DM, OM and EE contents and reduced the levels of NDF and ADF. With the progression of the vegetative stage, lactic acid (LA) and acetic acid (AA) values decreased while pH values and Fleig scores increased. The effects of additives were found to be insignificant for all parameters except for AA and Fleig scores. As the vegetative stage progressed, the dry matter digestibility (DMD), organic matter digestibility (OMD), digestible energy (DE), metabolic energy (ME) and net energy for lactation (NEL) values of the silages decreased significantly (p < 0.05). The addition of molasses or barley, compared to the control, resulted in a significant increase in the levels of DMD, OMD, DE, ME, and NE$_{L}$ (p < 0.05). In conclusion, in parallel with the progression of the vegetative stage, the DMD, OMD, DE, ME, and NE$_{L}$ values of the silages decreased, increasing with the addition of the additives, and the obtained silages were of high-quality as alternative quality roughage in ruminant feeding.

Keywords: Forage turnip (Brassica rapa), silage, digestibility, energy content

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