Abstract
The Cornell Net Carbohydrate and Protein System (CNCPS) model has been increasingly used in tropical regions for dairy and beef production. However, the lack of appropriate characterization of the feeds has restricted its application. The objective of this study was to develop and evaluate a feed library containing feeds commonly used in tropical regions with characteristics needed as inputs for the CNCPS. Feed composition data collected from laboratory databases and from experiments published in scientific journals were used to develop this tropical feed library. The total digestible nutrients (TDN) predicted at 1x intake of maintenance requirement with the CNCPS model agreed with those predicted by the Weiss et al. (1992) equation (r² of 92.7%, MSE of 13, and bias of 0.8%) over all feeds. However, the regression r² of the tabular TDN values and the TDN predicted by the CNCPS model or with the Weiss equation were much lower (58.1 and 67.5%, respectively). A thorough comparison between observed and predicted TDN was not possible because of insufficient data to characterize the feeds as required by our models. When we used the mean chemical composition values from the literature data, the TDN predicted by our models did not agree with the measured values. We conclude using the TDN values calculated using the Weiss equation and the CNCPS model that are based on the actual chemical composition of the feeds result in energy values that more accurately represent the feeds being used in specific production situations than do the tabular values. Few papers published in Latin America journals that were used in this study reported information need by models such as the CNCPS.
Highlights
The demand for meat and milk will increase 2.9 and 3.2% annually in the developing world between 1993 and 2020 (Bradford, 1999; Delgado et al, 1999)
The objective of this study was to develop a tropical feed library containing chemical composition values needed for the Cornell Net Carbohydrate and Protein System (CNCPS) model (Fox et al, 2000) to predict feed biological values
The data collection and organization of this database consisted of three phases: (1) the information reported for each feed was sorted by common name, botanical name, variety, preservation method, fertilization, and region; (2) the coefficient of variation (CV) for each feed component was computed and samples that inflated the CV more than 30% were considered to be outliers and excluded from the database; and (3) feeds lacking crucial information for the CNCPS model (DM, CP, Neutral Detergent Fiber (NDF), and Lignin) were excluded from the database
Summary
The demand for meat and milk will increase 2.9 and 3.2% annually in the developing world between 1993 and 2020 (Bradford, 1999; Delgado et al, 1999). Improved nutrition is the most important and most feasible way to increase animal productivity to meet this anticipated demand. When measured data on the protein and carbohydrate contents of feeds were used, the predictions of the performance of growing steers 2) and dual-purpose cows (Juarez Lagunes et al, 1999; Lanna et al, 1996) by the Cornell Net Carbohydrate and Protein System (CNCPS) were more accurate than when tabular values were used. The CNCPS model requires an accurate description of the carbohydrate and protein fractions and the rates of digestion of these fractions to obtain the best predictions. Several feed composition tables have been developed for tropical regions. The total digestible nutrients (TDN), which was derived either from digestion trials or from empirical equations published by Harris et al (1972), was used to estimate the feed concentration of metabolizable energy (ME) and net energy (NE)
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