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The objectives of these studies were to assess U.S. dairy nutritionists' approaches toward balancing CP in lactating cow diets, and to leverage existing knowledge of postabsorptive AA metabolism through the application of a mathematical ration-balancing model to predict N efficiency through a more accurate postabsorptive amino acid (AA) delivery. In experiment 1, dairy nutritionists (n = 77) that fed a total of 521,000 lactating dairy cows responded to a questionnaire related to demographic information, feelings toward environmental nitrogen (N) excretion, and dietary CP balancing practices. Eighty-nine percent of nutritionists balanced diets based on one or more individual AA requirements of dairy cows. The primary concern with formulation of lower CP diets was the cost per unit of metabolizable protein (MP). In the second study, three treatments were fed to lactating Holstein cows (n = 48) to test proof of concept of NASEM 2021 and a nonlinear optimizer: a control balanced to fulfill all nutrient needs of lactating dairy cows producing 45 kg milk/d using the NRC (2001) dairy model (NRC01), and two diets balanced with a nonlinear optimizer that fulfilled requirements according to the updated NASEM (2021) dairy model and attempted to either: 1) maximize N efficiency through tailored post-ruminal AA supply (NEFF), or 2) maximize income over feed cost (IOFC). A simulation function was written in RStudio (version 2022.02.3) to predict daily animal performance with NASEM 2021. Dry matter intake, milk, and milk components from both the observed data and the simulation data matrices were analyzed as repeated measures (days) in a mixed model to test for both observed and predicted (simulated) differences in treatment means. Income over feed cost was $4.83, $4.77, and $5.12/cow/d for NRC01, IOFC, and NEFF, respectively (P = 0.96). Nitrogen efficiency (%) was greatest for NEFF (33.7), followed by NRC01 (28.9) and IOFC (23.4; P < 0.05 between all treatments). Based upon simulation data, NASEM 2021 predicted relative performance differences between animals that consumed treatments with differing absorbed EAA supplies, although residual analyses revealed that further progress could be made in milk protein (g/d), milk fat (g/d), milk yield (kg/d), and DMI (kg/d) predictions. Doctor of Philosophy Nitrogen (N) is considered one of the major environmental pollutants of the dairy industry. A concerted focus on reducing dietary crude protein (CP) loss by targeting the specific amino acid (AA) needs of cattle will also reduce the amount of N they excrete. Because most dairy farmers hire nutritionists to formulate rations for their cows, the objective of our first study, performed in 2019, was to assess U.S. dairy nutritionists' approaches toward balancing AA in lactating cow diets. The objective of our second study was to apply a mathematical ration-balancing model that specifically optimized AA efficiency for lactating dairy cows by leveraging existing knowledge of dairy cow AA metabolism. In study 1, 89% of nutritionists balanced diets based on one or more individual AA requirements of dairy cows. Most respondents (72%) reported that they are currently formulating diets with lower dietary protein than they were 3 to 5 yr ago. In the first study, the primary concern with formulating lower protein diets was the high cost of protein sources that are highly metabolizable for cows. In study 2, income over feed cost (income made from estimated milk sales minus cost of feed) was similar for cows fed a diet with the lowest protein (relative to two other diets), but cows on the low protein diet also ate the least (kg of dry matter/d) and produced the least amount of milk protein (kg/d) and milk fat (kg/d). Still, relative to the other two diets in the study, N consumed by cows on the lowest CP diet was more efficiently converted to milk protein, which resulted in lesser N excretion in milk. Harnessing the knowledge gained from these studies could allow significant reduction of environmental N excretion at little to no cost to consumers or farmers.

Spineless cactus is a useful feed for various animal species in arid and semiarid regions due to its adaptability to dry and harsh soil, high efficiency of water use and carbohydrates storage. This meta-analysis was carried out to assess the effect of spineless cactus on animal performance, and develop and evaluate equations to predict dry matter intake (DMI) and average daily gain (ADG) in meat lambs. Equations for predicting DMI and ADG as a function of animal and diet characteristics were developed using data from eight experiments. The dataset was comprised of 40 treatment means from 289 meat lambs, in which cactus was included from 0 to 75% of the diet dry matter (DM). Accuracy and precision were evaluated by cross-validation using the mean square error of prediction (MSEP), which was decomposed into mean bias, systematic bias and random error; concordance correlation coefficient, which was decomposed into accuracy (Cb) and precision (ρ); and coefficient of determination (R2). In addition, the data set was used to evaluate the predicting accuracy and precision of the main lamb feeding systems (Agricultural and Food Research Council, Small Ruminant Nutritional System, National Research Council and Institut National de la Recherche Agronomique) and also two Brazilian studies. The DMI, CP intake (CPI), metabolizable energy (ME) intake and ADG increased when cactus was included up to 499 g/kg DM (P500 g/kg DM) had a decreased DMI, CPI and NDF intake, but increased feed efficiency (P

Made available in DSpace on 2013-09-27T14:53:35Z (GMT). No. of bitstreams: 1 WOS000292445000018.pdf: 159060 bytes, checksum: ba52293118f64e763ee5cca8e34ada05 (MD5) Previous issue date: 2011-06-01 Made available in DSpace on 2013-09-30T18:03:34Z (GMT). No. of bitstreams: 1 WOS000292445000018.pdf: 159060 bytes, checksum: ba52293118f64e763ee5cca8e34ada05 (MD5) Previous issue date: 2011-06-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:19:11Z No. of bitstreams: 1 WOS000292445000018.pdf: 159060 bytes, checksum: ba52293118f64e763ee5cca8e34ada05 (MD5) Made available in DSpace on 2014-05-20T13:19:11Z (GMT). No. of bitstreams: 1 WOS000292445000018.pdf: 159060 bytes, checksum: ba52293118f64e763ee5cca8e34ada05 (MD5) Previous issue date: 2011-06-01 A main purpose of a mathematical nutrition model (a.k.a., feeding systems) is to provide a mathematical approach for determining the amount and composition of the diet necessary for a certain level of animal productive performance. Therefore, feeding systems should be able to predict voluntary feed intake and to partition nutrients into different productive functions and performances. In the last decades, several feeding systems for goats have been developed. The objective of this paper is to compare and evaluate the main goat feeding systems (AFRC, CSIRO, NRC, and SRNS), using data of individual growing goat kids from seven studies conducted in Brazil. The feeding systems were evaluated by regressing the residuals (observed minus predicted) on the predicted values centered on their means. The comparisons showed that these systems differ in their approach for estimating dry matter intake (DMI) and energy requirements for growing goats. The AFRC system was the most accurate for predicting DMI (mean bias = 91 g/d, P < 0.001; linear bias 0.874). The average ADG accounted for a large part of the bias in the prediction of DMI by CSIRO, NRC, and, mainly, AFRC systems. The CSIRO model gave the most accurate predictions of ADG when observed DMI was used as input in the models (mean bias 12 g/d, P < 0.001; linear bias -0.229). while the AFRC was the most accurate when predicted DMI was used (mean bias 8g/d. P > 0.1; linear bias -0.347). (C) 2011 Elsevier B.V. All rights reserved. Univ Estadual Paulista, UNESP, Dept Zootecnia, BR-14884900 São Paulo, Brazil Ohio State Univ, Dept Anim Sci, Columbus, OH 43210 USA Univ Sassari, Dipartimento Sci Zootecn, I-07100 Sassari, Italy Univ Estadual Paulista, UNESP, Dept Zootecnia, BR-14884900 São Paulo, Brazil