Nürtingen, FH, Diplomarb., 2004. / Betreuer: Gerhard Schwarting.

No description available.

Não consta resumo na publicação. / Abstract not available.

Freie Universiẗat, Diss., 2005--Berlin. / Dateiformat: zip, Dateien im PDF-Format. Erscheinungsjahr an der Haupttitelstelle: 2005.

Zugl.: Hohenheim, Univ., Diss., 2009

The effects of feeding Master Graze (MG) on dairy cows productivity and nutrient digestibility were evaluated in experiment 1. Sixteen cows were divided into 4 groups and fed treatment diets for 4 consecutive periods. Cows on the control diet were fed a diet with corn silage and alfalfa hay as forage source (1:1; DM basis). For treatment groups, the MG substituted the forage mix at 16, 33 and 50%. The feeding of MG at the three tested levels had no effects on feed intake, milk production or milk composition. The apparent digestibility of DM, OM, NDF and CP were higher in cows fed the MG. In experiment 2, the effects of maturity and preservation method on MG nutrient composition and digestibility were evaluated. The MG was harvested at 3 maturity levels and then preserved using oven-dried, ensiled, or freeze dried. In general, the MG digestibility and nutritional quality was higher in the first cut and with the freeze dried preservation method.

Não consta resumo na publicação. / Abstract not available.

No description available.

Le système INRA d’alimentation des Ruminants prédit les réponses de l’animal à des variations d’apports d’aliments ingérés. Toutefois, il évalue mal l’influence de l’alimentation sur la qualité des productions, et en particulier la qualité de la carcasse de bovins dont dépend le paiement des animaux aux producteurs. Pour un type d’animal donné, les poids et composition de la carcasse en lipides et protéines sont prédits par le modèle MECSIC (Hoch et Agabriel, 2004) à partir de l’énergie métabolisable ingérée calculée selon le système INRA de valeur énergétique des aliments et des rations. Or une étude bibliographique suggère que la composition des dépôts dépend aussi pour partie de la composition des rations qui détermine la nature des produits terminaux issus de la digestion des rations et le devenir métabolique des nutriments. Pour tester cette hypothèse, l’objectif fut d’étudier l’effet de la nature de la ration à même quantité énergie métabolisable (EM) ingérée sur la composition des dépôts et de la carcasse. Cet objectif est ciblé sur les bovins mâles en croissance. Les étapes principales de la thèse ont consisté à i) construire une base des données à partir des publications internationales traitant des effets de la variation des rations ingérées sur la composition de la carcasse chez les jeunes bovins, ii) explorer les relations entre la composition de la carcasse et la composition de la ration et sa métabolisabilité. La constitution de la base de données a montré que la composition de la carcasse n’est mesurée que dans 20% des publications, les 80% restantes l’ayant évalué par des mesures indirectes (index USA de rendement de viande, épaisseur de gras sous cutané, persillé, surface de muscle…) qui ne sont pas reliées entre elles. Une étape de recherche préliminaire a été mise en place pour quantifier par méta-analyse les relations entre mesures directes et indirectes de la composition de la carcasse dans le but d’utiliser le maximum de publications pour la suite de la thèse. Nous avons montré que seuls deux indicateurs (index USA de rendement de viande et épaisseur de gras sous-cutané) reflètent correctement la composition de la carcasse et peuvent être utilisés pour établir les lois de variation de sa qualité selon les conditions d’alimentation. Une autre méta-analyse a permis d’explorer à niveaux d’ingestion d’EM similaires, les réponses marginales des dépôts de lipides et protéines dans la carcasse, à des variations strictes de teneurs de la ration en EE, PDI, NDF ou du rapport Amidon/NDF, tout en considérant sa métabolisabilité (q=EM/EB). L’accroissement du rapport Amidon/NDF augmente la teneur en lipides des carcasses mais en deçà d’un seuil de métabolisabilité de la ration de 0,65, i.e. si les rations ont plus de 36% de fourrages. Au-delà de ce seuil, qui correspond à un rapport Amidon/ NDF minimal voisin de 2, il n’y a plus d’effet. Ainsi à même EMI, la composition du gain (et donc l’énergie nette déposée) ne varierait pas linéairement avec la métabolisabilité q de la ration. De plus la teneur en PDI augmente significativement la proportion de lipides de la carcasse (et réduit celle des protéines), surtout si le niveau global d’apports de PDI est limité et ne dépasse pas 2,5 fois les besoins d’entretien en PDI. La teneur en EE a peu d’effets. Ces caractéristiques de ration conduisent à des profils de nutriments (rapport entre nutriments glucogéniques et cétogéniques, azote-alpha-aminé) qui sont aussi discriminants pour la composition de la carcasse. Nos résultats suggèrent qu’il faut considérer les effets de la nature de la ration dans la modélisation de la composition de la carcasse des bovins selon l’EM ingérée. Cela pourra faire l’objet d’une modification significative du modèle de croissance (MECSIC) pour améliorer son pouvoir prédictif. / The INRA feeding system for Ruminants predicts the animal's responses to changes in feed intake. However, it poorly evaluates the influence of feed intake on the quality of productions, and in particular the quality of bovine carcass, on which the payment of animals to the producers depends. For a given type of animal, the carcass weight and its composition in lipids and proteins are predicted by the MECSIC model (Hoch and Agabriel, 2004) from the intake of metabolizable energy calculated from the INRA energy system. However, a literature review suggests that the composition of the depots also partly depends on the composition of the rations, which determines the nature of the digestion end products, and the metabolic fate of the nutrients. To test this hypothesis, the objective was to study the effects of the nature of the ration at similar metabolizable energy intake (MEI) on the composition of the carcass. This study is targeted to growing male cattle. The main steps of the thesis consisted of (i) building a database based on international publications on the effects of dietary intake on carcass composition in young cattle, (ii) exploring the relationships between carcass composition and the composition and metabolisability of the ration. The database showed that the composition of the carcass was measured in only 20% of the publications; the remaining 80% evaluated it by indirect measurements (USA yield grade, fat thickness, marbling, ribeye area ...). A preliminary research step was developed to quantify by meta-analysis the relationships between direct and indirect measurements of carcass composition in order to use the maximum number of publications for the rest of the thesis. We have shown that only two indicators (USA yield grade and fat thickness) correctly reflect the composition of the carcass and can be used to establish the response equations of carcass quality to dietary conditions. Another meta-analysis explored the marginal responses of lipid and protein depots in the carcass to strict variations in the dietary concentrations of EE, PDI, NDF or of the starch / NDF ratio, while considering its metabolisability (q = EM / EB). An increase in the starch / NDF ratio increases the lipid content of the carcasses but below a metabolizability threshold of 0.65, i.e. when rations contain more than 36% fodder. Beyond this threshold, which corresponds to a minimum starch / NDF ratio close to 2, there is no longer any effect. Thus, at similar MEI, the composition of the gain (and therefore the net energy deposited) does not vary linearly with the metabolisability q of the diet. Furthermore, the PDI content significantly increases the proportion of carcass lipids (and reduces that of proteins), especially if the overall level of PDI intake is limited and does not exceed 2.5 fold the maintenance requirements in PDI. The dietary EE content has little effect. These diet characteristics result in nutrient profiles (glucogenic / ketogenic ration, alpha-amino-N) which also discriminate carcass composition. Our results suggest that the effects of the nature of the ration should be considered when modeling the carcass composition of bovine animals from MEI. This should lead to significant changes in the MECSIC growth model to improve its predictive power.

Master of Agribusiness / Department of Agricultural Economics / Jeffery R. Williams / Economically optimized ration formulations were used to test whether California dairy producers who implemented price risk management strategies on both the input and output sides achieved significantly higher net returns as measured by milk income minus feed costs compared to producers who bought feed and sold milk on the spot market. Two ration formulation models were developed, a least cost and a profit-maximization. The least cost method formulates a ration that meets the nutritional requirements of a lactating cow at the lowest possible cost for a given level of milk production. The profit maximization model incorporates into its algorithm a production function between net energy intake and milk production that increases at a decreasing rate. For today's high producing cows, after being supplied with enough energy to meet maintenance requirements, all additional energy is partitioned for milk production. Up to a certain point, depending on the price of milk and the price of feed, the cost of providing additional feed units is more than offset by the revenues derived by the extra milk produced from the larger quantities of feed consumed. The profit-maximization model used formulates a ration using both feed and milk prices where the cost of the last unit of feed provided is equal to the revenues of the last unit of milk produced. To compare returns, a ration program was designed that could either use spot or forward values for feed costs and milk price to economically optimize the ration on a weekly basis in the cow’s milk production cycle. To better gauge the impact of price volatility on both the input and output sides and to account for the extended nature of the forward contracts, the 305-day lactation cycle of a high producing cow over six successive cycles was used. The federal order Class III milk price was used for milk values and it was assumed that unless the producer engaged in some sort of forward contract, the milk price received was the monthly Class III value. To account for forward sales, the Class III futures contract traded at the Chicago Mercantile Exchange was used. For the feed prices, the ration model had a library of 16 different ingredients, 11 of which had forward and spot values. Similar to the output side, it was assumed that unless the producer engaged in some sort of forward contract the feed price used was the spot value averaged for each month. Most California dairy operators use some version of the least-cost method when formulating their rations. A large number also forward contract a significant portion of their feed as the concept of forward contracting feed is much more common in the western U.S. as compared to other regions in the country. Conversely, there has been little interest in locking in future milk prices as the tools for forward contracting are relatively new and many producers are not familiar with the mechanics. This helps explain the limited use of the profit-maximization model since milk prices are an integral part of this process. Results of this study show that producers who formulate using the profit-maximization model attain higher milk production and derive higher milk revenues, albeit with higher feed costs. Nonetheless, across every situation, that is whether one forward contracts feed, milk, or some combination thereof the profit-maximization model returned anywhere from $0.14 to $0.19 of milk revenues in excess of feed costs per hundredweight of milk as opposed to the least-cost method. For a producer milking 1,000 cows this represents another $50,000 to $70,000 of income per year. The results also show that whether least-cost or the profit-maximization method is employed, feed costs were lower when producers forward contract at least a portion of their needs. Milk prices, on the other hand, were lower relying on the spot market as opposed to either of the two forward milk contracting models that were developed. Finally, the variability of returns as measured by the coefficient of variability show less volatility in revenues when producers forward contract milk and less variability with input costs when producers forward contract feed.