Production and quality of alfalfa harvested on different stages of maturity in summer and fall
Alfalfa is a very important forage for the dairy industry. The objective of this study was to determine the effect of maturity on quality of hay of two varieties of alfalfa (“Cuff-101” and “Excellent Multileaf”) in two seasons (summer and fall). The production (t/ha) and quality of forage was characterized through the determination of leaf:stem ratio of biomass and its content of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin over a range of days to harvest (0, 5, 10, 15, and 20 d following Stage 2) within the two seasons. Data were analyzed as a split-plot experiment, the plots arranged factorially in a randomized complete block design, being the alfalfa varieties and season the main effects, and maturity the subplot term. Results indicated season influenced both production and forage quality, so in fall the production of DM was lower (P<0.05). On d 20 in summer a yield of 5.8 t MS/ha was determined and in fall only 4.9 t MS/ha, without differences among varieties (P>0.05). Dry matter crude protein (CP) content of leaves in fall was 35.0% on d 0, and in summer 29.3% (P<0.01). In summer, CP content of leaves was 32.7% and 29.3% in the whole plant, without differences among them (P>0.05), whereas the content of CP on stem was lower than both (22.6%, P<0.01). On d 20 in summer the leaves had 25.4% CP, stems 20.2% and whole plant 23.7% in Excellent Multileaf, compared to 23.5%, 19.1% and 21.6% CP in Cuff-101, respectively, without those differences among varieties being significant (P>0.05). On d 20 it was determined 23.7% CP in fall, whereas in summer 21.6% (P<0.01). NDF and ADF diminished (P<0.01) in fall. In terms of CP, ADF and NDF in leaves, stem and whole plant, it was concluded that a higher quality alfalfa was growth in fall, without differences among varieties.
Keywords: Alfalfa, CP, Fiber