Predictive equations for milk yield and dry matter intake and development of a maximum-profit ration formulation model

Eleven cooperating University Agricultural Experiment Stations provided information on 19 separate experiments in which total feed intake and milk production was recorded. A total of 492 cows on these experiments provided 4135 Holstein and 704 Jersey 28-day records which contained information on feed intake, milk yield, butterfat content, ration composition, body weight, season and stage of lactation. The backward elimination procedure was used to identify important dependent and independent variables, and least square procedures were used to develop predictive modes for milk (R² = .807) and maximum dry matter intake (R² = .741). Season, days in lactation, fat percent, dry matter intake, body weight, and crude protein and concentrate percent of dry matter were identified as important independent variables for the milk model. In the dry matter intake model independent variables consisted of season, days in lactation, fat yield, milk yield, body weight, and crude fiber content of the ration. Linear, squared and logarithmic expressions of the variables were used resulting in curvilinear response models. In order to incorporate the above two equations into a maximum profit ration formulation model several additional areas were investigated, including the relationship between crude fiber and concentrate content in the ration, and the variation of crude fiber and net energy within a ration. A procedure was developed to adjust net energy values for rate of intake, thus compensating for declining digestibility as intake rate increased. Least-square equations were developed to provide quantitative estimates of the substitution of one feed ingredient in a ration for another while still maintaining constant production. A linear programming algorithm was used as the base upon which a maximum-profit ration formulation program was built. The curvilinear production response to varying amounts of dry matter, crude protein and concentrate was divided into smaller segments which were closely approximated by a straight line and incorporated into the linear programming matrix. A final solution was obtained by a repetitive stepwise procedure which solved through each production segment until an optimum ration was obtained which combined highest possible returns from milk produced with minimum feed cost. Additional stipulations were incorporated into the final matrix to insure that such a ration also met minimum accepted nutrient requirements.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Animal Science

Department dc:contributor.department

Animal Science

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1976

Author dc:creator

• Brown, Carl Alton

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10919/118382

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/118382