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ABSTRACT This study aimed to evaluate the in vitro gas production from three pearl millet cultivars submitted to four nitrogen levels. The treatments consisted of three pearl millet cultivars (ADR 500, ADR 7020, and LABH 70732) and four nitrogen levels (0, 50, 100, and 200 kg/ha), using urea as the nitrogen source. A 3 x 4 factorial experimental design, employing a randomized block setup, was used to assess both gas production and digestibility. No interaction was observed between nitrogen doses and fermentative parameters on in vitro gas production from the dry matter of pearl millet cultivars. Nitrogen had no impact on the dry matter content or chemical composition of the cultivars. Consistency prevailed in the chemical composition across the various cultivars, a trend that extended to the gas production rates for both soluble and insoluble contents. Notably, nitrogen fertilizer exerted an influence on the fermentation pattern of organic matter, gas production, and lag time for the cultivars. Nitrogen fertilization is advised solely for enhancing fermentative attributes in the case of the cultivar ADR 7020.

It is important to evaluate nutritional value of new grass species, which can be better characterized through rumen fermentation and degradation techniques. The aim was to evaluate the effects of Nitrogen (N) fertilization on the kinetics of fermentation and ruminal degradation of the Mulato II grass. Two distinct sources of N (common and protected urea) were used during two periods of the year (summer - I and autumn - II). A completely randomized experimental design was used, in a 2x4 factorial arrangement with three replicates. Fraction A changed based on N dosage. The passage rate (K) and effective degradability (ED) were influenced by sources and doses of N, while Fraction B and Lag Time were not influenced during period I. Fractions A and B and EDs were all influenced by N sources and doses during period II. Lag time and potential degradability were influenced by N sources only. Among the kinetics parameters of dry matter ruminal fermentation obtained during period I, only K1 was influenced by the interaction between N doses x sources, while the remaining parameters were only influenced by the N doses applied. As for period II, with the exception of K2, all remaining parameters were influenced by the interaction of N doses and sources. Protected urea improved fermentation parameters during period I. The dose equivalent to applying 150kg/ha positively influenced ruminal fermentation parameters of the Mulato II grass mainly in the summer. The use of protected urea as a Nitrogen source improved fermentation parameters in the summer. Keywords: Brachiaria; digestibility; digestion kinetics; rumen fermentation; gas production

This study aimed to evaluate the effects of including virginiamycin (VM) in two levels, the proteinenergy supplement for growing beef cattle diet with the tropical grass base in the dry season. Three treatments were evaluated: control treatment, only Mineral Supplement ME - Production - F.10 proteinenergy (SPE); 100 virginiamycin treatment (VM 100) + SPE 108 mg (Phigrow®) VM / animal / day and treatment virginiamycin 200 (200 MV) + SPE 216 mg (Phigrow®) VM / animal / day. The variables analyzed were the supplement intake (SI), average daily gain (ADG), biometric measurements and body condition score (BCS) in experiment 1 and the average daily supplement intake (ADSI), ruminal pH, ammonia nitrogen, in situ ruminal degradability of dry matter (DM), acid detergent fiber (ADF) and neutral detergent fiber (NDF) in experiment 2. There was no statistical difference for ADG, SI and biometric measurements (P>0.05), ADG for VM 200 of 0,431; VM 100 of 0.391 and control 0.398 kg/animal/day. There was no significant difference (P>0.05) for ruminal pH, the ammonia concentration and the variables at the in situ degradability of DM, NDF and ADF. The virginiamycin conveyed in SPE for beef cattle grazing can promote changes in consumption did not cause significant effects on the values of ruminal pH and ammonia nitrogen and do not show significant effects on the degradability of DM, NDF and ADF.

The production capacity of green and dry mass of the entire plant, efficiency of N conversion, apparent N recovery and the chemical composition of cultivar Mulato II was evaluated under a system of cuts and nitrogen doses. The assay, conducted in the municipality of Goiânia, GO, Brazil, had a totally randomized 2 x 4 factorial design (2 height cuts, 0.40 and 0.50 m and 4 nitrogen doses), with three replications and subdivided subplots. Treatments comprised four N doses (0, 50, 100 and 150 kgha-1 N, with urea as nitrogen source). There was no significant interaction (p>0.05) between N doses and cut heights for the variables productivity of green (PGM) and dry (PDM) mass, nitrogen use efficiency (NUE) and apparent N recovery (ANR), which were neither affected (p0.05) DM rates of the plant, whilst mean dry matter rate was 17.49%. CP rates were affected (p0.05) occurred in ADF rates among the variables analyzed. ADF contents were influenced by N supply (p