Document Type : Research Paper
Authors
1 Department of Animal and Poultry Sciences, Aburaihan College of Agricultural Technology, University of Tehran, Tehran, Iran
2 Department of Animal and Poultry Sciences, College of Agricultural Technology (Aburaihan), University of Tehran, Tehran, Iran
Abstract
Objective: Livestock producers in Iran face increasing challenges with forage supply due to progressively detrimental climatic changes. Due to nutrient losses during drying, and spoilage and mold during storage of fresh forage, ensiling is used to preserve and utilize forage when fresh produce is unavailable. Intercropping barley crop (Hordeum vulgare) with forage pea (Pisum arvense L.) can provide a substantial portion of the protein requirements for growing livestock and dairy cows, given its acceptable protein yield per hectare. Considering the advantages of legume-cereal forage intercropping and the widespread adoption of winter cropping for forage production nationwide, particularly in the Varamin region of Iran, optimizing the legume-cereal ratio in forage crop mixtures is essential to maximize agronomic performance, water-use efficiency, nutritional value, and suitability of the mix for animal feeding. Therefore, this study aimed to investigate the effects of different ratios of whole-crop barley to forage pea on silage fermentation quality and digestibility, and to determine the optimal mixing ratio.
Method: Whole crop barley and forage pea were harvested at specific growth stages (early dough stage for barley and mid-flowering to late flowering/early pod formation for forage pea). The experiment consisted of four treatments: 1) 100% barley silage, 2) 80% barley + 20% forage pea silage, 3) 70% barley + 30% forage pea silage, and 4) 60% barley + 40% forage pea silage, with three replicates in a completely randomized design. Ensiling was carried out in 10-liter plastic mini-silos. After 60 days of ensiling, the silos were opened and sampled for analysis of crude ash, ether extract (EE), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent insoluble nitrogen (ADIN), lignin (ADL), water-soluble carbohydrates (WSC), ammonia N and volatile fatty acids. An in vitro gas production test was used to compare treatments for gas production kinetics, and estimated digestibility, metabolisable energy, and short-chain fatty acid concentrations.
Result: With the increase in the proportion of forage pea, the dry matter content decreased while pH increased. The inclusion of forage pea in the mixture tended to increase crude protein and crude ash contents (P < 0.10). However, the values of EE, ADF, NDF, ADL, and ADIN were not affected by the forage pea (P > 0.05). Furthermore, increasing the proportion of forage pea significantly elevated the concentration of ammonia-N in the silage (P<0.05). No significant differences were observed among silages in terms of acetic, propionic, and butyric acid concentrations, with the levels of these volatile fatty acids falling within the range typically found in well-fermented silages. The treated silage containing 20% forage pea exhibited higher gas production volume, organic matter digestibility, metabolizable energy, and short-chain fatty acids than forage barley silage as the sole crop (P < 0.05).
Conclusions: Overall, the results demonstrated that mixing forage pea with whole crop barley during ensiling improved its nutritional value by enhancing CP content and reducing fiber levels, while taking advantage of barley forage, such as higher dry matter and WSC. This approach could serve as a winter-cropping strategy in semi-arid climates, improving feed quality, reducing costs, and promoting environmental sustainability. The present study suggested a 20% forage pea inclusion level for mixing with barley forage in laboratory conditions. However, this proportion should be further studied in animal trials.
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