Avaliação nutricional da grama-estrela cv. Africana para vacas leiteiras em condições de pastejo

Abstract

RESUMO -Objetivou-se avaliar nutricionalmente a grama-estrela ( Cynodon nlemfuensis) cv. Africana utilizada sob pastejo rotacionado por vacas leiteiras. Dez vacas mestiças foram manejadas em 2 ha de grama-estrela e divididas em 11 piquetes/ha. O período de pastejo foi de três dias e os 30 subseqüentes foram destinados à recuperação da pastagem. Durante o período experimental, os animais foram ordenhados duas vezes ao dia e receberam suplementação com 2 kg de concentrado. Amostras representativas do pasto ingeridas (extrusa) foram colhidas para determinação de sua composição nutricional. O consumo de matéria seca (MS) pelos animais foi estimado utilizando-se cromo e a MS indigestível como indicadores externo e interno. O desempenho individual das vacas foi avaliado pela produção de leite diária e pela pesagem dos animais. A dinâmica da matéria alimentar foi estimada com base nas técnicas in vitro gravimétricas, de produção cumulativa de gases da fermentação microbiana e da estimativa da cinética de passagem das fases sólida e líquida. A quantidade de energia líquida total (ELt), em MJ/dia, atendeu à demanda energética exigida pelos animais. Os valores de proteína metabolizável (PM) preditos corresponderam ao suprimento de 91% da PM exigida por esses animais. As predições das exigências em macrominerais atenderam apenas 75% do Ca exigido, mas atenderam às exigências dos demais macrominerais. A grama-estrela atende à demanda energética nutricional de mantença e produção de 11,7 kg de leite por dia. Nas circunstâncias estudadas, é necessário suplementar nutrientes que complementem a PM e Ca não atendidos completamente. O teor e as características cinéticas da fibra não causam repleção ruminal e restrição sobre o consumo de vacas leiteiras em pastejo.Palavras-chave: análise bromatológica, desempenho animal, forragem tropical Nutritional analysis of stargrass cv. Africana for dairy cattle under rotational grazingABSTRACT -An nutritional analysis of stargrass cv. Africana fed dairy cattle under rotational grazing was evaluated in this research. Ten Holstein-Zebu crossbred cows were managed in 2 ha covered with the grass and divided in 11 paddocks /ha with three grazing days 30 days of resting period. During the experimental period the animals were milked twice a day for 16 days and were feed two kg of concentrate. Representative samples of the pasture consumed (extrusa) were taken and determined the nutritional composition. The dray matter intake of the animals was estimated by means of chromium and indigestible DM as external and internal markers. The individual performance of the cows was evaluated by daily milk production and by weighting the animals. The food matter dynamics was estimated with gravimetric in vitro techniques, cumulative gas production from microbial fermentation and estimates of the passage kinetics of solid end liquid phases. The amount of total net energy (NEt) in MJ/d meet the energetic requirement by the animals. The predicted values for metabolizable protein (MP) corresponded to the supply of ...

Performance and metabolite profile of dairy cows fed tropical grasses and concentrates containing crude protein with low or high degradability

“…The use of the CNCPS model to evaluate diets is useful to estimate the nutritive value of different forage resources and other tropical foragebased diets (Cabral et al, 2000;Vieira et al, 2000a,b,c). The dietary synchronization is important for microbial growth and, depending on the availability of non-fibrous carbohydrates, the microbial biomass uses degradable nitrogen more efficiently Malafaia et al, 1998;1999;Vieira et al, 2000c;Favoreto et al, 2008;Fernandes et al, 2014). Because of the nutritional imbalances of sugarcane, e.g., high soluble sugars and low protein content, it should be used with caution to prevent excess nutrient losses (Fernandes et al, 2001).…”

Nutritive value of Tanzania grass for dairy cows under rotational grazing

“…Favoreto et al (2008) observed levels of 20.37 g/100 g in star grass (Cynodon nlemfuensis). Vieira et al (2000) highlighted the importance of determining this fraction, as it is considered to be unavailable in the rumen and the intestines.…”

“…Fractions A' (simple sugars) and B 1 ' (non-fibrous complex carbohydrates) were estimated by in vitro gravimetric and gas production techniques. A gravimetric profile of degradation of neutral detergent fiber corrected for ash and protein (NDFap) was obtained after incubation of samples (Favoreto et al, 2008).…”

“…Protein fractions were determined as follows: fraction A (non-protein nitrogen) as the difference between total N and N insoluble in trichloroacetic acid; fraction C as the acid detergent insoluble protein (ADICP) that is indigestible in the gastrointestinal tract of the animal; fraction B 2 (protein with a slow degradation rate) as the difference between neutral detergent insoluble protein (NDICP) and ADICP according to Sniffen et al (1992); and fraction B 1 (protein with a faster degradation rate than fraction B 2 ) by the difference, according to the equation 100 − (A + B 2 + C) (Favoreto et al, 2008).…”

“…Recently, mathematical models for diet formulation using non-linear optimization techniques have been suggested by several authors (Souza, 2006;Tedeschi et al, 2008;Jardim et al, 2013). These models allow for simultaneous diet formulation and evaluation to meet animal protein, energy, and fiber requirements, subject to the constraint of maximum fiber intake capacity (Favoreto et al, 2008;Jardim et al, 2013). However, these models need to be repeatedly evaluated and updated to enhance predictive and optimization powers.…”