Seasonal diet quality and metabolic profiles of steers grazing on Chihuahuan desert rangeland

Abstract

Four Angus steers (BW=350±3kg) with esophageal cannulae and four fitted with ruminal cannulas (BW=351±5kg) as well as fifteen steers of the same racial characteristics (BW=320±2kg), were used to evaluate seasonally across four years (2005–2009, excluding 2007) the nutritive quality of diet and the blood metabolites and insulin levels in grazing beef cattle a Chihuahuan desert rangeland. The diet consumed by grazing cattle during spring and winter was low quality because of crude protein (CP) was less than 70g/kg DM and neutral detergent fiber (NDF) higher than 720g/kg DM. Initial washing loss at time zero “A”, digestion rate “c”, effective degradability of NDF (EDNDF) and CP (EDCP), potential gas production (PGP), ruminal ammonia–nitrogen (NH3N), total volatile fatty acids (TVFA) propionate, butyrate, glucose (G), urea nitrogen (UN) and insulin were highest in summer compared to spring (P<0.05). In contrast, ruminal acetate concentrations and blood non-esterified fatty acids (NEFA) level were highest in spring as compared to summer (P<0.05). It was concluded that season of grazing had a marked influence on diet quality as well as in the blood metabolites and insulin levels in grazing beef cattle a desert rangeland.