Effect of Cut and Irrigation Water Quality on Chemical Composition and in situ Rumen Degradability of Alfalfa

Document Type: Research Articles

Authors

Department of Animal Science, Faculty of Agricultural Science, Sari Agricultural Science and Natural Resources University, Sari, Iran

Abstract

The objective of this study was to investigate the effects of cut and irrigation water quality on chemical composition and in situ dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) degradability of alfalfa. Three fistulated Zel sheep (approximately 2 years old) were used in a complete randomized design to evaluate the in situ rumen degradability. Ruminal incubation times consisted of 0, 3, 6, 9, 12, 24, 48, and 72 h. The results showed that increasing the cut of maturity and irrigation with saline water significantly cause to increase the components of cell wall (P=0.0011) and decrease the protein concentrations in alfalfa (P=0.0001). Except the quickly rumen degradability of DM that in first cut of alfalfa was higher, other parameters of ruminal degradability of DM were not different. Ruminal NDF degradability in second cut of alfalfa, that irrigated with saline water, was higher (P=0.0143). Degradation rate of NDF in first cut of alfalfa, and effective rumen degradation of NDF at different passage rate in alfalfa that irrigated with saline water were higher. Slowly ruminal CP degradability (P=0.001) and effective degradation at different passage rate of alfalfa, that irrigated with saline water, were higher. The cut did not effect on CP degradability of alfalfa. Our experiment indicates that increasing water salinity have not a negative effect on alfalfa forage quality.

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INTRODUCTION

The gradual increase in the amount of land and water resources affected by salt in arid and semi-arid regions requires strategies to optimize the use of these marginal-quality resources (Diaz et al. 2018). An interest in salt tolerance has developed worldwide because crop irrigation promotes soil salinization (McKimmie and Dobrenz, 2007). The nutritional values, yield, and quality of forages are affected by growth stage, forage species, cultivar, fertilization, soil type, climate (e.g., rainfall, temperature), planting (e.g., row spacing, planting rate), and growing conditions (Cox et al. 1994). Vegetative forage production is basically a linear function of plant transpiration. Open stomata with lots of water vapor leaving the plant (transpiration) allows for maximum carbon dioxide uptake to build plant carbohydrates and biomass. Excessive salinity in the crop rootzone creates osmotic stress that reduces root uptake of water and crop transpiration. The added stress then reduces forage yield (Sanden and Sheesley, 2007). The gradual reduction in the quantity and quality of conventional water resources for agricultural use in arid and semi-arid regions, representing 40% of the world's 270 million irrigated hectares, has necessitated the supplementation of new water resources obtained from the desalination of saline groundwater and seawater. Moreover, even if desalinized water of this type is considered high quality water by farmers, initial experiences with desalinated water have not proven totally positive. Biosaline agriculture (i.e. economically sustainable crop production using irrigation water and soils with a wide range of salinity levels) has gained popularity in recent years in arid and semiarid regions. Recent field and greenhouse experiments have demonstrated the potential of growing certain ‘pre-selected’ varieties of alfalfa in highly saline condition (Diaz et al. 2018). Alfalfa (Medicago sativa) is the most important and a good quality forage for dairy cattle. Alfalfa possesses