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

Four Angus steers (BW=350±3 kg) with esophageal cannulae and four fitted with ruminal cannulas (BW=351±5 kg) as well as fifteen steers of the same racial characteristics (BW=320±2 kg), 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 70 g/kg DM and neutral detergent fiber (NDF) higher than 720 g/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.