Alvaro Garcia
The artichoke (Cynara cardunculus var. scolymus) consists of a variety of a species of thistles cultivated as a food. The edible portion of the plant consists of the flower buds before the flowers bloom. Once the buds bloom, the structure changes into a coarse and barely edible form. Artichokes are cultivated in several parts of the world. In Europe they contribute to the agricultural economy of the Mediterranean region, accounting to nearly 60% of the world production.
Broccoli is an edible green plant of the cabbage family (family Brassicaceae, genus Brassica) with a large edible flowering head. Broccoli is a cultivar of the species Brassica oleracea with large flower heads usually dark green in color, surrounded by leaves and arranged in a tree-like structure branching out from a thick light green stack. It resembles cauliflower which is a different cultivar group of the same Brassica species. It is native to the Mediterranean where more than 40% is produced together with Southeast Asian regions.
Use of artichoke and broccoli coproducts to feed livestock
Once artichoke flower-heads are harvested (20% of the biomass) for human consumption, what’s left in the field are leaves, stems and some inflorescences (80% of the biomass). This byproduct has been used to feed livestock in Europe, Asia, and America.
When fed to ruminants these underutilized resources reduce the land base needed for forage production, while also reducing feed costs, which are the main individual cost associated with livestock production.
In addition, since these are byproducts not used for human nutrition, they do not compete with land used for this purpose. One of the drawbacks however is their high seasonal availability which requires to find methods for their conservation. Their high-water content however can pose a challenge to obtain an adequate fermentation during the ensiling process.
On the other hand, the changes operated during the ensiling process like the acidity for example, can exert a positive influence in reducing anti-nutritional factors (i.e. polyphenols) present in these feedstuffs. So far there have been several studies done with micro silos but none on a farm scale, particularly during a prolonged period of conservation.
A recent study (Paula Monllor et al. 2020) characterized the silage process of broccoli and artichoke coproducts and artichoke plant stubble in commercial size silos (300 kg round bales) over 200 days to determine shelf life and quality and suitability of these silages as a ruminant feed. The study included changes in silage fermentation, microbial population dynamics, nutrient composition, fermentative components, and in vitro digestibility. The treatments were three different silages (7 round bales each) as follows:
- Ensiled artichokes
- Ensiled broccoli
- Ensiled artichoke stubble
The average ambient temperatures during the trial were 15â—¦C with a relative humidity of 68%. Artichokes were cut and chopped to 2 cm with a forage chopper. On the same day, 21 round bale silos of each material of approximately 300 kg and 0.64 m3 each, were made with a baler-wrapper, using five layers of inner conventional net wrap and 13 layers of conventional plastic film for each silo.
Sample collection was at day 0 (day of ensiling), 4, 7, 10, 15, 30, 60, and 200. For day 0, three samples were collected from three different parts of the whole batch of the chopped material to be ensiled. For the rest of the sampling days, a sample of 1 kg of three different bales was collected daily with a manual core-sampler from the middle, and 20 cm up and down from the base of the bale. The three sub-samples were then composited into one.
Evolution of microbial populations during the ensiling process
Lactic bacteria populations increased in the early days (0–7) in all three silages, reaching the maximum on day 7. They then decreased and stabilized on day 30 in broccoli silage (6.88 log cfu/g FM) and on day 60 in artichoke and artichoke stubble (7.13 and 7.08 log cfu/g FM, respectively). Enterobacteria population decreased markedly in all three silages from day 0 and disappeared completely on day 15 in broccoli, and day 60 in the other two silages.
The evolution of the mesophilic aerobic population varied according to the coproduct. In broccoli, it decreased gradually from day 0 (8.84 log cfu/g FM) and stabilized on day 60 (4.56 log cfu/g FM), while in artichokes the reduction started on day 15 (7.77 log cfu/g FM) until day 200, reaching a value of 1.57 log cfu/g FM.
In artichoke stubble, a significant increase in the mesophilic aerobic population was observed on day 7 (8.75 log cfu/g FM), followed by a reduction and then stabilization on day 30 (4.52 log cfu/g FM). Yeasts were reduced in all three silages throughout the experiment, reaching 3.17, 1.65 and 3.42 log cfu/g FM on day 200, respectively for broccoli, artichokes and artichoke stubble.
Moulds remained stable in broccoli and artichokes throughout the experiment, with an average value of 1.07 and 2.11 log cfu/g FM, respectively. However, in the artichoke stubble a reduction was observed from day 0 (5.15) until their disappearance on day 30.
Judging by the physicochemical parameters and fermentative and nutritional components the ensiled coproducts stabilized by day 30, with their quality remaining high until day 200. The high microbial quality and nutritional composition at the end of the trial (day 200) suggests they were suitable feed for cattle.
The variables with the greatest differences among sampling times were microbial populations and fermentation variables. There were no dry matter losses, while some significant differences were observed in the nutritional composition, particularly crude protein and fiber, but they did not affect the nutritive value of the silages. Phytosanitary residues tested on day 200 were below the maximum limits set by European standards.
These results show that ensiling these coproducts in commercial round bale silos seems to be a suitable technique that allows for their prolonged preservation.
Reference
Paula Monllor, Gema Romero, Raquel Muelas, Carlos A Sandoval-Castro, Esther Sendra, JosĂ© RamĂłn DĂaz. Ensiling Process in Commercial Bales of Horticultural By-products from Artichoke and Broccoli. Animals (Basel). 2020 May 11;10(5):831.
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