Evaluation Feedstuff for Farm Livestock

ANSC 405 - Exam 2

procedures to evaluate feedstuff

• nutrient composition

• palatability

• digestibility

• productive value

• physical or handling characteristic

• provide economic comparisons

what are the types of analytical methods?

• chemical procedures

• biological procedures

• microbiological procedures

what does the chemical procedure include?

gravimetric, titration and colorimetry

gravimetric is…

weight

titration

technique where a solution of known concentration is used to determine the concentration of an unknown solution

colorimetry

measurement of the wavelength and the intensity of electromagnetic radiation in the visible region of the spectrum

biological procedures include…

lab animals

microbiological procedures

employ isolated bacteria

obtaining a good sample of feedstuff is key to…

reliable feed nutrient evaluation

list the steps to evaluate feedstuffs

1. identification

2. sampling

3. general

what are the methods used to estimate the nutritional value of a feedstuff?

1. laboratory-based analyses

2. animal-based analyses

3. additional or miscellaneous considerations

nutritional value

describes the estimated nutritional quantity and quality of a feedstuff

nutritional value is dependent on ______ and __________ _____

species; physiological state

the 3 components of estimating nutritional value:

1. estimating nutrient content

2. efficiency of nutrient use

3. identifying the presence of antinutritional factors

what’s an antinutritional factor?

components that decrease the nutritional value of the feed

lab-based analyses

measure the amount of each individual component (nutrient) in the feedstuff

what was the initial procedure used to estimate quantity of individual components of feedstuff?

Proximate Analysis System

proximate analysis is a combination of analytical procedures that provides the different fractions of feedstuff. what are these fractions?

• dry matter

• dry inorganic material

• crude protein

• ether extract (EE)

• CHO

what method breaks down the forage into fractions of readily digestible and indigestible portions, and is a better method than proximate analyses?

Van Soest (Detergent) Method

why is there no routine analysis for vitamins?

because of the diversity of compounds

what are the 3 ways energy content is expressed?

• dry matter basis

• as-fed basis

• air-dry basis

what is the dry matter basis when expressing energy content?

amount contained in only the dry matter fraction without water

what is the as-fed basis when expressing energy content?

amount contained in feed as it would be fed to animal, includes water

what is the air-dry basis when expressing energy content?

assumed to be ~90% DM; air-dry and as-fed may be the same for many common feeds

what basis is the most accurate measurement of both feed composition and nutrient requirement

dry matter basis

feeding trial

gives an indication as to whether the animal will accept the feedstuff and the performance obtained from the feedstuff compared to others.

in digestion or metabolism trials, what does chemical analysis measure?

you start with chemical analysis to determine the nutritive value of feed

digestibility is measured as…

difference between what went in and what came out

what are factors that affect digestibility within species?

• age

• particle size and/or extent of feed processing

• feed source and composition

• level of feed intake

• rate of passage through intestinal tract

• nutrient excess or deficiency

feedstuff energy

used to denote value of feed for its primary function

what is the primary function of feed that’s just ingested?

to furnish energy for body processes and to form the non-nitrogenous organic matter of tissues and secretions, functions in which all organic nutrients can take part

what are all different measures of feed energy value?

• total digestible nutrient (TDN)

• gross energy

• digestible energy

• metabolizable energy

• net energy

• roughage/concentrate ratio

total digestible nutrient (TDN)

a general measure of nutritive value of feed, digestion coefficients are used to compute its content of TDN

list the different energy units

• calorie (cal)

• kilocalorie (kcal) - 1000 small calories

• megacalorie (Mcal) - 1000 kcal or 1,000,000 cal

what are some common effects of energy deficiencies?

• decreased production level such as weight gain or milk production

• decreased performance level such as speed or endurance

• decreases reproduction efficiency such as conception and/or pregnancy rates

• increased incidence of metabolic disorders like ketosis

what is the most accurate method to compare interspecies energy expenditures and energy requirements?

comparing metabolic body weight

what are other factors that affect energy requirements between interspecies?

• activity level

• production level

• environmental conditions

• nutritional deficiencies

• general health

what are the stages of development in an animal?

• maintenance

• growth

• production

• reproduction

maintenance

support of an animal when doing no work and yielding no product

how much feed consumed by animals is used for maintenance?

1/2

growth

the general development of an animal from the time it’s born until its reached maturity

production

animals being fed for production of market animals such as those for meat, milk, wool and work

reproduction

from conception until birth; it’s important to neither overfeed or underfeed the mother during this time

gross energy (GE)

total potential energy of a feedstuff consumed

fecal energy (FE)

waste product during digestion and absorption

digestible energy (DE)

measurement takes account of digestible losses and is subject to same variables that affect digestion and same additional losses in metabolism as in TDN

GE-FE

gaseous products of digestion (GPD)

combustible gases that escape body during digestion and absorption process

urinary energy (UE)

energy excreted via urine

metabolizable energy (ME)

usable portion of ingested energy

Me = DE-UE-GPD

heat increment (HI)

increase in heat production following eating feed when animal is in thermally neutral environment

net energy (NE)

energy used for either maintenance only or for maintenance and production

NE = ME-HI

list the types of feedstuff energy in digestion and metabolism

• gross energy

• fecal energy

• digestible energy

• gaseous products of digestion

• urinary energy

• metabolizable energy

• heat increment

• net energy

ways to physically evaluate feedstuffs

• eye appraisal of feed

• palatability

• accounting for factors that might influence the value of a feedstuff

list factors that might influence the value of a feedstuff

• soil fertility

• growing conditions

• harvesting

• processing and storage

feedstuff energy in digestion and metabolism table.

what is used to determine gross energy?

bomb calorimeter

**make sure to study equations**