W4 lab: sampling feedstuffs

Question 1

proximate analysis

Answer 1

procedures used for analysis of nutrients & feedstuffs to compare results of analyzed nutrients in feeds/rations delivered to animals vs what was purchased & originally formulated

Question 2

how are bag feeds sampled

Answer 2

using probes or triers designed to collect a # of small sub-samples simultaneously throughout the whole bag

Question 3

how are hay bales sampled

Answer 3

directly from intact bales at original storage location prior to feeding (otherwise broken up & particles separate out by size)

• probe takes unbiased cross-sectional core sample as it is pushed/drilled into bale
• representative sample requires 15-20 core samples from random bales
• rectangular bales: sample from butt end
• round bales: sample from curved side

Question 4

types of probes

Answer 4

1. penn state hay probe → attached to hand/power drill & drilled into center of bale, then dowel plunger used to push sample into plastic bag
2. best harvest hay/forage probe → uses power-drill & a bagging attachment to deposit sample pushed out but cleaning rod
3. golf club hay probe → hand powered, manually push shank into bale while holding plastic bag under t-handle

Question 5

sampling TMR

Answer 5

• have to be sampled immediately after putting the feed out for the animals before they have access to it
• larger sample of TMR (from >1 location) is collected from feeding bunk line followed by immediate sub-sampling to for storage & analysis

Question 6

sampling from silage piles

Answer 6

sampled from large piles of loose silage material made by scraping exposed face

Question 7

sampling other feed ingredients stored in piles on mixing pad or in commodity bays

Answer 7

easily sampled (should ensure freshest load)

Question 8

sampling liquid ingredients stored in large tanks

Answer 8

sample either from access valves or during mixing as fluid is pumped into mixer wagons

Question 9

frequency of sampling depends on:

Answer 9

1. variability: more variable chem compounds = more frequent sampling & analysis
   
   • grains do not vary → do not require analysis of every batch
   • forages vary based on season & maturity at harvest ∴ sample every time new lot is received
   • byproducts vary based on country of origin or manufacturing plant → origin determines frequency of sampling
   • silage piles should be sampled at regular intervals throughout pile’s lifetime (possibility of mold or yeast)
2. inclusion level: ingredients at higher quantities can have large impact on chem profile if not updated regularly

Question 10

digestibility

Answer 10

proportion of a feed that is not excreted in feces & is assumed to be absorbed

• assessed through digestion studies → quantifying nutrient intake, collecting & quantifying fecal nutrient output, & calculating diff between intake & output as % of total input
• measures apparent digestibility → does not account for part of feces not derived from undigested feed residues (e.g. digestive enzymes, bacteria, & intestinal tissues)

Question 11

apparently digestibility study methods

Answer 11

1. total collection method: requires total daily fecal collection using metabolic crates or collection harnesses & complete records of feed intake
   • % apparent digestibility = ((amt of nutrient consumed) — (amt of nutrient in feces)/amt of nutrient consumed) x 100
2. indicator method: animals feed diet of unabsorbed indigestible reference substance (nontoxic e.g. chromic oxide, acid insoluble ash, lignin) then feed & feces are collected & analyzed for nutrient of interest → apparent digestibility can be obtained w/ less labor-intensity (can use grab samples)

Question 12

fecal sample collection

Answer 12

1. total fecal collection requires metabolic crates or collection harnesses (small ruminants)
2. representative fecal sample when TFC not possible
   
   1. ground collection must see which animal defecates & collect immediately, samples should have no grass or insects (ideally feces collected directly into container while animal is defecating)
   2. rectal grab sample when feces cannot be collected from ground w/out contamination, feces is collected directly from rectum using gloved hand to scrape feces into container

Question 13

hay bale types we will be sampling

Answer 13

1. orchard grass
2. alfalfa (high quality)
3. alfalfa (low quality)
4. wheat hay

Question 14

bagged feed types we will be sampling

Answer 14

1. crimped oats
2. rolled barley
3. wheat bran
4. layer feed