11:067:330 Lecture Notes - Lecture 2: Kjeldahl Method, Silage, Dry Basis

• School: Rutgers University
• Department: Animal Science
• Course: 11:067:330
• Professor: P Stark

Document Summary

When determining feed: need most cost friendly, most palatable, and most nutritious for the animal. Methods for determining nutritive value: laboratory assessments, animal assessments, or a mix of both. Nutritive value assessed in a lab through chemical evaluations. Proximate analysis measures crude fiber, crude protein, ash (minerals), and ether extract (lipids) (cid:1543) proximate analysis most common. Fifth component -- nitrogen-free extract -- is mathematically determined. Pp: you have a 4g sample of hay that weighs 3. 6g after drying. Pp: you run a kjeldahl on 1. 8g and are left with . 06g of nitrogen. 06g n x (1g protein / . 16g nitrogen) (cid:1543) . 375g protein. After a kjeldahl on a sample always multiply by 1/. 16! (or 6. 25) What % cp in sample? (cid:1543) . 375g / 1. 8g = 20. 8% on a dry basis. Pp: you run an ether extraction on the other 1. 8g of sample and are left with . 054g ether extract. 054g / 1. 8g x 100 (cid:1543) 3% lipid (dm)