Protein Fractions of Pearl Millet Submitted to Different Nitrogen Doses and Cutting Ages

Brazilian livestock breeding is closely linked to exploitation of natural and cultivated pastures, so high productivity of forage grasses is one of the main factors responsible for the success of this activity. Annual grasses that mature in the hot season, such as millet (Pennisetum glaucum (L) R. Br.), are important elements in grazing systems that aim to obtain high forage yield and animal productivity in relation to area. According to Moojen et al. (1999), this species adapts well to the climate conditions in the Midwest region of Brazil and is able to produce a large quantity of good-quality forage in a short time. Due to the variability among genotypes, the choice of cultivar is an important decision and should consider genetic factors of the plant and regional edaphoclimatic factors. Millet has excellent nutritional value, good palatability and digestibility and is nontoxic to animals at all growing stages. Benedetti (1999) evaluated millet grown in a broadcast seeding system and measured average crude protein (CP) concentrations between 8.0 and 9.2% after 30 days of growth, while at the end of the pasture cycle the levels varied from 3.2 to 4.6%, which limited consumption.

According to Corsi (1995), nitrogen is the main component of the protoplasm after water. It acts in various metabolic processes, composing part of the hormones, and directly affects the photosynthesis process through its presence in the chlorophyll molecule. The application of N on forage plants can stimulate production of mass, and if there are no limitations due to production factors and lack of other nutrients, the increments can be very high (Silva et al., 2008). Kollet et al. (2006) evaluated the qualitative characteristics of pearl millet cultivars at three cutting ages: 35, 42 and 49 days, with application of 20 kg ha-1 of N, incorporated in the soil before planting, plus side dressing of 60 kg.ha-1 applied when the plants reached 10 cm in height, measuring CP values of 13.9 to 20.6%.Advances in the knowledge of ruminant nutrition, especially in the past decade, have enabled the development of new feeding systems and methods of assessing livestock feed tomaximize use of forage plants. The supply of ruminants’ nutritional needs, according to Mello and Norberg (2004), depends on the energy content of the diet that can be utilized by the ruminal microorganisms or be absorbed from the ruminal escape in other compartments of the digestive tract. The Cornell Net Carbohydrate and Protein System (CNCPS) is a system that considers the dynamics of ruminal fermentation and potential loss of nitrogen, as ammonia, in the evaluation of animal feeds (Sniffen et al., 1992), with the objective of adjusting ruminal digestion of carbohydrates and proteins to increase microbial production, reduce losses of N and estimate the ruminal escape of nutrients (Balsalobre et al., 2003). Although there have been numerous studies of the chemical composition of the forage grasses predominant in Brazil, there is little information available regarding their nutritive value, especially related to the fractionation of nutrients in function of the management conditions with use of nitrogen fertilizer.

The aim of this experiment was to characterize and identify the protein fractions contained in two pearl millet cultivars (ADR-300 and BN-1) submitted to different N doses and cutting ages, under the conditions in the municipality of Goiânia, Goiás state, Brazil.

 

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(Author: Oscar L. Faria Júnior, Aldi F. de S. França, Alzira G. da Silva-Pause, Eliane S. Miyagi, Hugo J. M. C. Peron, Emmanuel Arnhold, Alessandra G. Mascarenhas, Daniel S. Corrêa

Published by Macrothink Institute)