< Animal Nutrient Requirements
" Maintenance = Basal Metabolism + Minimum Movement + Foraging On a yearly basis requires greatest amount of energy by the animal
Depends on species - Cow > sheep > deer
Age - Young > Old
For example basal metabolic rate of sheep: birth = 132 kcal /m3 15 weeks = 68 kcal /m3 6 years = 52 kcal /m3
Domestic vs Native - Most wildlife species have the ability to vary their basal metabolic rate with season.
" Growth - important energy demand in young animals and gestating females
" Lactation - greatest energy requirement of mature females above maintenance. Requires 45% greater energy supply than maintenance.
" Reproduction - energy need in last trimester of pregnancy for females and important for males during breeding season
" Environmental conditions affect the amount of energy needed by animals Cold environments require more energy for maintenance. Hot environments require more water for perspiration.
" Level of activity: 15% greater energy required for standing compared to lying down. 40-46% more energy needed for range animals than stall-fed animals.
< Match Time of Maxiumum Forage Nutrient Supply with Period of Maximum Animal Demand.
" Timing - Plan so that time of greatest animal need will coincide with time of greatest nutrient supply.
Consider type of forage (i.e., winter forage) and type of operation (ie. stocking steers during growing season vs year-round Cow/calf operation).
Timing is the basis for season suitability grazing.
Native animals already do this through natural selection. (ie. the have young in spring when forage is of greatest quality).
" Stock conservatively Allows a greater amount of forage per animal so each animal can select most nutritious foods for diet. Maximum selectivity generally results in improved diet quality.
Also reduces energy required to find adequate diet.
" Manipulate vegetation to meet animal needs. Plant introduced pastures - to provide abundant high quality forage during a particular season. For example:
Range Animal Nutrition - Page 1 • Crested wheatgrass provides good spring/fall grazing because of its growth pattern.
• New rye grasses are being developed with maintain energy and even protein values well into winter. These grasses tend to be tall to stick up above the snow and tent to act as "black bodies" for earlier snow melt and spring green-up.
Manage for palatable shrubs - to create protein and phosphorus supply during dormancy. On the benches above Logan research has been conducted to use cattle to reduce grass biomass so that shrubs will grow. Shrubs are needed for deer winter habitat.
Manage for plant diversity. Seasonal forage supply is improved as plant diversity increases because plant mature at different rates and have different levels of nutrients.
" How do grazing animals cope with period of low forage quality? Build up fat when forage quality is high (Fat for energy and vitamin A is stored in fat). Grazing animals with good fat reserves can survive 30-60 days with little or no food consumptions. (Mule deer does with high levels of fat reserves have survived periods of complete starvation up to 64 days.)
Native animals lower their metabolic rate and consequently lower energy requirements.
Nitrogen recycling in ruminants such as bison. (i.e., Some of the nitrogen that gets absorbed out of the rumen is put in saliva where it goes back into the digestive system, for possible absorption, instead of being lost in the urine).
Soil ingestion - can play a critical role in permitting ruminants to meet critical mineral needs.
Supplementation - is the major operations expense confronting the range livestock industry.
• Energy - rarely economical to supplement. When energy is supplemented, use of range vegetation generally decreases.
o High Quality Energy (grains) - generally impractical on rangelands except under drought and heavy snow. Can be used effectively for young animals in a creep feeder. Young animals under 6 months of age can be permanently stunted if they are subjected to severe under-nutrition.
o Low Quality Energy - Hay or straw is necessary to supplement when animals cannot meet daily dry matter requirements on rangeland (winter and drought). Remember hay or straw is basically an energy source - cellulose.
• Protein (or Nitrogen) - Use of range may actually increase with nitrogen supplementation.
o Non-protein Nitrogen (Urea and Biuret) - Lower cost than true protein, made into protein by rumen microbes, can be used to meet about 1/3 total protein requirements.
o High-protein feeds - alfalfa, cottonseed meal, soybean meal.
o Protein supplementation important when crude protein values of rang forage falls below 6%. Because below 6%, rumen microbial growth is inhibited and structural CHO's cannot be adequately digested.
Range Animal Nutrition - Page 2