Old C.A.,California Chapter ARPAS |
Oltjen J.W.,California Chapter ARPAS |
Miller J.R.,California Chapter ARPAS |
Ohanesian N.,California Chapter ARPAS |
And 3 more authors.
Professional Animal Scientist | Year: 2016
Nine samples of pure stand alfalfa hay, representative of the compositional variability found in Mediterranean and Intermountain West climates, were collected throughout California and western Nevada during the 2008 growing season. Samples were evaluated in vivo (at either maintenance or ad libitum intakes by lambs), in vitro, in silico, and by near infrared spectrophotometry to determine characteristics of DM and fiber degradation as well as energy metabolizability. Also determined, from these and other routine analyses, were common indices of alfalfa quality including relative feed quality, relative feed value, in vivo TDN and ME. Significant differences (P < 0.05) in observed ME (Mcal/kg) were noted for alfalfa hays depending on source; quality indices were compared with observed ME. None of the indices evaluated were valid predictors of observed ME (P < 0.050), with the exception of near infrared predicted ME at either level of intake. Users of quality indices may expect less than optimal prediction of animal performance from use of indices or calculations based on indices failing to accurately predict ME. Results from this study indicate that ME estimated from near infrared spectrophotometry of pure stand alfalfa hay may improve characterization of alfalfa hay quality in that, depending on the feeding standard, ME input explains the vast majority of variation in animal output. However, given the limited numbers of alfalfa hay samples evaluated in this study, more studies are required. © 2016 American Registry of Professional Animal Scientists
Owens F.N.,DuPont Pioneer |
Qi S.,DuPont Pioneer |
Sapienza D.A.,Sapienza Analytica
Professional Animal Scientist | Year: 2014
The metabolizable protein (MP) system initially outlined by Burroughs et al. (1975) and expanded in later NRC publications separates the need for N for ruminal microbes within the rumen from the postruminal need for amino acids for growth and maintenance of the host ruminant. Compared with the CP system, the MP system represents a clearer understanding of the complexity of the protein metabolism of ruminants. Using compiled data sets from recent publications, the effect of dietary CP concentration on performance of feedlot and dairy cattle was reevaluated. Maximum performance (rate of gain; milk production) required higher CP concentrations than routinely are being fed, with the added performance being due at least partially to greater DMI of diets containing more CP. Precision of the NRC (2000) MP model 1 was evaluated by comparing its predicted values with measurements of duodenal flow determined with growingfinishing cattle fed 118 different concentrate- rich diets. Though duodenal supply of microbial protein increased with intake of TDN, diet TDN concentration was not correlated (R2 = 0.00) with the extent of OM fermented in the rumen. Although undegraded intake protein and MP increased with DMI, precision of predicting degraded intake protein, undegraded intake protein, and MP per kilogram of diet was poor, reflecting imprecision of estimates or equations and failure of prediction equations to match in vivo measurements. The paucity of data supporting values suggested for individual feeds and inclusion of numerous theoretical but unverified equations within current MP models severely limits their precision and usefulness for field application. © 2014 American Registry of Professional Animal Scientists.