Unit 2: Evaluating Feedstuffs for Farm Livestock

1. Unit 2: Evaluating Feedstuffs for Farm Livestock

2. Unit 2: Evaluating Feedstuffs for Farm Livestock • Unit 2 Objectives: • Understanding of methods used to determine nutrient composition of feeds • Knowledge of sample collection methods • Identify and communicate how feed samples are reported • Comprehension of how feedstuff digestibility is determined • Understand various energy measurements and how they are used • Physical and economical evaluation of feeds

3. Unit 2: Evaluating Feedstuffs for Farm Livestock • Analytical Methods for Nutrient Composition • Three general types of methods can be used to determine effect of feedstuffs • Chemical procedures • Titration, colorimetry, etc. • Biological procedures • Feedstuff tested by a live animal (rat, chick) • More accurate • Much more tedious and expensive

4. Unit 2: Evaluating Feedstuffs for Farm Livestock • Microbiological procedures • Tested w/ isolated bacteria • Obtaining Samples for Analysis • Key to reliable feed nutrient evaluation is a representative sample • Identification • Thoroughly identify the feed tested • What might we include in our identification? • Sampling • Grains/Mixed Feeds • Sacked feeds – 2 samples/sack, 5-7 sacks, handful each

5. Unit 2: Evaluating Feedstuffs for Farm Livestock • Bulk Feeds – 12 to 15 samples, widely separate locations for sampling (while delivered or fed, if possible) • Mix samples in a clean pail, make sure feed doesn’t separate, send a 1 or 2lb. sample to the lab • Hay • Use a core sampler • Take a 12’ – 15” core sample that will include stem and leaves • 12 – 15 samples are needed to be accurate (1/bale) • Try to get to middle of the stack if possible • “Grab” Samples can be used, but accuracy is variable

6. Unit 2: Evaluating Feedstuffs for Farm Livestock • Haylage or Silage • Upright silos – collect during feedout, several small samples, mix together for one composite • Pit/Bunker silos – 4-5 grab samples from a fresh face, do not collect spoiled material, do not collect within 12”-18” from edge • Freeze if you are collecting over multiple days • Refrigerate if you can’t mail immediately (what happens if you don’t do this?) • Harvest Sampling • Not recommended for any feed <30% DM • Same methods as discussed prior • 12-15 samples, mix for one composite • Mark different fields as feed is stored (plastic marker, oats, etc.)

7. Unit 2: Evaluating Feedstuffs for Farm Livestock • General • Not beneficial unless you are going to use in designing a feeding program • Three benefits to using sampling for proper balance of feedstuffs – 1) minimize protein supplementation and reduce cost, 2) can properly balance if a nutrient is being underfed, 3) can confirm that a factor other than feed is limiting production • Proximate Analysis • Most generally used chemical analysis to describe nutrient composition of feeds

8. Unit 2: Evaluating Feedstuffs for Farm Livestock • Dry Matter (DM) • How do we determine DM content of a feedstuff? • Can we do this ourselves? • What is the benefit of knowing the DM content? • Ash (minerals) • Burned sample that removes all other nutrients • Only inorganic residue remains • May not be 100% accurate • Crude Protein (CP) • Digest to N through chemical process (Kjeldahl process) • How do we determine CP content from N concentration? • Does not distinguish between forms of N

9. Unit 2: Evaluating Feedstuffs for Farm Livestock • Ether Extract (Fat) • Use ether to extract fat contents for 4 hrs • Loss of wt = fat content • Includes some “fats” that are of no use to animals, so may not be 100% accurate • CHO • Crude Fiber (CF) – remove water & fat; then through chemical rxn. to remove protein, sugar, and starch; leaves cellulose, lignin, and minerals; (how are the minerals removed?) • Nitrogen-Free Extract (NFE) – sugars and starches (maybe some hemicellulose & lignin); not determined by an analysis; 100% - water, ash, protein, fiber, fat

10. Unit 2: Evaluating Feedstuffs for Farm Livestock • The Van Soest Method • Focuses on forage fiber • Divides fiber into digestible and indigestible fractions • Extraction w/ detergents • Predicts intake – NDF – index of gut fill • Predicts digestibility – ADF – indicates forage digestibility • Heat damaged forages – can help determine the amount of protein unavailable in feedstuff. What level of unavailable begins to cause problems?

11. Unit 2: Evaluating Feedstuffs for Farm Livestock • Near Infrared Reflectance Spectroscopy • Ability to sample quickly w/ little preparation (grinding); only uses one sample • Can be completed in <3 min. • Analyze multiple components in one operation • Measurements done by absorption/reflection of light • Not accurate for minerals • Expensive equipment, must be calibrated correctly • Wet-chemistry analysis is more accurate • Inexpensive

12. Unit 2: Evaluating Feedstuffs for Farm Livestock • Determination of Vitamins • No routine analysis available to determine vit content • Assays can be ordered to determine specific vitamins, if needed • Determination of Energy • Bomb Calorimeter • Sample is burned in an oxygen atmosphere • Liberated heat raises the temp of water surrounding the devise • This temp increase is the basis for determining the energy concentration • 1 cal heat required to raise 1g water 1º C

13. Unit 2: Evaluating Feedstuffs for Farm Livestock • Nutrient Expression • DM basis • Most accurate/common way to express nutrient levels • Levels the playing field to compare feeds • As-Fed basis • Amount of nutrients contained in a feed as the animal would consume it • Air-Dry basis • Assumed to be ~90% DM

14. Unit 2: Evaluating Feedstuffs for Farm Livestock • Let’s practice some conversions • Thumb rules • Nutrient concentration should increase when converting to DM basis • Wt. will decrease on DM basis • Feeding Trials • Can give information as to acceptance and performance of a feed • Doesn’t tell why a feed performed the way it did

15. Unit 2: Evaluating Feedstuffs for Farm Livestock • Digestion or Metabolism Trial • Weakness of chemical analysis is that is doesn’t take into account digestibility very accurately • Steps of a digestion trial • Proximate feed analysis to know what you start w/ • Feed a measured amount of feed, or feed at constant rate • Collect fecal matter • Proximate analysis on feces • Difference is the apparent digestibility of the feed

16. Unit 2: Evaluating Feedstuffs for Farm Livestock • Can use markers or indicators to identify feeds • Testing can be done in metabolism stalls where the animal is somewhat confined • Attached to collection instruments for feces and/or urine • Usually done in 2 phases • Preliminary phase • Frees digestive tract of any other types of feeds • Animal gets accustomed to the process and feed • 3-5d in pigs, 8-10d in ruminants

17. Unit 2: Evaluating Feedstuffs for Farm Livestock • Collection phase • When feed and fecal collections are measured • What are some of the chances for error in this system? • Measures of Feedstuff Energy • Total Digestible Nutrients (TDN) • General, calculated amount • Does not account for important losses of digestion • Can be expressed as lbs., %, or kg

18. Unit 2: Evaluating Feedstuffs for Farm Livestock • Can be extremely variable/inaccurate (usually overestimate) • 1lb. TDN from 1.2 lbs. corn = 1.2 Mcal NE • 1lb. TDN from 2.1 lbs. hay = 1.0 Mcal NE • 1lb. TDN from 2.4 lbs. poor hay = .8 Mcal NE • Nutrient Partitioning in Digestion & Metabolism • Energy Units • Calorie = amount of heat needed to raise 1g water 1ºC • Kilocalorie = 1000 calories • Megacalorie = 1000 kcal, or 1,000,000 calories (a.k.a. therm)

19. Unit 2: Evaluating Feedstuffs for Farm Livestock • Gross Energy (GE) • Total potential energy of a feedstuff consumed • Determined in a bomb calorimeter • Fecal Energy (FE) • Undigested residue that passes through the GI • Can be collected and tested same method as above • Digestible Energy (DE) • DE = GE – FE • Takes account of some losses during digestion • Gasseous Products of Digestion (GPD) • Combustible gasses that escape the body during digestion & absorption • Mostly methane; some H, CO, acetone, etc.

20. Unit 2: Evaluating Feedstuffs for Farm Livestock • Most common in ruminants • Hard to measure accurately • Urinary Energy (UE) • Includes materials that result directly from the digestion/absorption/enzymatic processes • Many endogenous sources as well • Metabolizable Energy (ME) • ME = DE – UE – GPD • More accurate measure of nutritive value than DE and TDN • Easy to determine in nonruminants because of the lack of GPD

21. Unit 2: Evaluating Feedstuffs for Farm Livestock • Heat Increment (HI) • Increase in heat production following feed consumption • Caused by the heats of fermentation, and heats of nutrient metabolism • Energy is wasted unless the environmental temperature is below the animal’s critical temperature zone • If it is used for temperature regulation, becomes part of NEm • Net Energy (NE) • NE = ME – HI • Amount of energy used for maintenance only, or for maintenance and production purposes • Function should be stated clearly when reporting/evaluating NE

22. Unit 2: Evaluating Feedstuffs for Farm Livestock • NEm (NE for Maintenance) • Part of total NE needed to keep animal in energy equilibrium • No gain/loss of energy in body tissue • Basal Metabolism – energy needed to maintain basic vital cellular activity • Energy of Voluntary Activity – energy needed for basic movement to obtain food, water, lying down, etc. • Heat to keep body warm – additional heat needed when environmental temp < animal’s critical temperature

23. Unit 2: Evaluating Feedstuffs for Farm Livestock • Heat to keep body cool – extra energy expended when environmental temp > animal’s thermo neutral zone • NEp (NE Production) • Additional energy required above NEm • What would be considered production? • NEl, NEg • Energy in Beef Cattle • This system can be used to accurately predict energy needs for wt. gain under normal conditions • Make adjustments for abnormal conditions • See tables 2-3, 2-4, and 2-5 for reference • We will discuss further later in the semester

24. Unit 2: Evaluating Feedstuffs for Farm Livestock • Energy in Dairy Cattle • NE values are much more accurate than any other system • Evaluate NEm, NEg, and NEl • NEl – includes energy requirements for pregnancy, reproduction, and milk production • NEl – most often used component in ration formulation and evaluation • Energy in Swine • Generally use ME or DE as their evaluating tools • Will eat to energy requirements if feed ad libitum • Will cover further later

25. Unit 2: Evaluating Feedstuffs for Farm Livestock • Physical Evaluation of Feedstuffs • Eye Appraisal • Used mostly w/ forages • Type • Color • % of leaves • Weed contamination • Spoilage • Palatability

26. Unit 2: Evaluating Feedstuffs for Farm Livestock • Factors Affecting Value • Soil fertility • Growing conditions • Harvesting • Stage of maturity • Losses • Processing & Storage • Evaluating Feeds Cost/Unit of Nutrient • Cost of feed/unit wt. divided by unit wt. * % nutrient concentration • Examples

27. Unit 2: Evaluating Feedstuffs for Farm Livestock • Unit 2 Assignment: • Review Problem Solving Questions • 1-5 • Take your time!!!!