Lecture 19: Dairy Nutrition 3

nutritional priorities

• protein utilization efficiency

• mineral balance and interactions

• adequate water intake

• proper dry cow management

amino acid balance

• lysine and methionine = limiting AA in most feeds

• microbial protein = ideal AA profile

• RUP (bypass protein) helps meet AA needs → SBM or fish meal

protein sources and considerations

• soybean meal, distillers grains, fish meal

• palatability may limit inclusion

• high fat sources may impair fiber digestion

protein requirements

• typical diet: 16-18% CP

• higher in early lactation

• essential to match energy and protein supplies

why is it essential to match energy and protein supplies?

• microbes require energy and nitrogen simultaneously

• imbalance → ammonia accumulation → urea

• ammonia from rumen → blood → blood ammonia increases

mismatch of energy and protein supplies =

wasted protein

consequences of excess protein

• increased urinary nitrogen excretion

• infertility and lameness risk → excess ammonia/urea can delay maturation of oocytes or developing embryos

• environmental nitrogen loss

BUN and MUN

• indicators of nitrogen balance

• BUN: 10-20 mg/dL

• MUN: <10-12 mg/dL

• high values: excess RDP or poor CHO balance

excess ammonia can overwhelm the liver’s ability to

convert to urea

what ingredient supplements lysine and methionine but is not very palatable?

fish meal

major minerals

• Ca, P, Mg → often supplemented

• K, Cl, S

potassium interactions

• high K → decreased Ca mobilization → milk fever/hypocalcemia

• high K → decreased Mg absorption → grass tetany

calcium nutrition

• often supplemented above requirement (0.62-0.67%)

• true availability about 45%

• high fat diets → increased Ca and Mg needs

• Ca:P ratios not as important as meeting requirements for Ca and P

why do high fats increase Ca and Mg needs?

insoluble soaps form between cations (mostly Ca and Mg) and fatty acids in SI, making them unavailable for absorption

importance of phosphorus

• often deficient in soils and plants

• required for milk production

phosphorus excretion

• excess P excreted in feces

• environmental concern

true or false: increased phosphorus above NRC requirement does not increase milk yield.

true

phosphorus guidelines

• requirement: 0.3-0.4%

• 0.45% unnecessary

which mineral is affected by high potassium and linked to grass tetany?

magnesium

water importance

• most important nutrient

• essential for milk production

water intake

• 2-4 lb water/lbs DMI

• +3-5 lb water/lbs milk

factors affecting water intake

• milk yield

• DMI

• temperature and humidity

• water quality and availability

water management

• adequate access and space → one trough per 15-20 cows

• clean, palatable water

• most intake after feeding/milking

water quality

• assess: odor, taste, contaminants

• risks: nitrates, sulfates, algae

• poor water quality reduces intake

goals for dry cow feeding

• maintain BCS (3-4) → needs to have adequate fat reserves for 6-8 weeks after calving

• maintain DMI

• avoid excess energy → little to no grain until she enters transition phase

transition period

• last 3 weeks pre-calving and 3 weeks post-calving

• decreased intake, increased demand

• high-risk period for metabolic disease

adapting to grain feeding strategy for transition cows

• introduce grain pre-calving

• prepares rumen for lactation diet

• increased energy density helps to compensate for drop in DMI

high fiber feeding strategy for transition cows

• maintain high NDF diet

• add grain after calving

• fiber buffers rumen pH to help avoid rumen acidosis when grain is added

adapting to grain strategy

• goal: rumen adaptation

• advantage: smooth transition

high fiber strategy

• goal: rumen stability

• advantage: lower acidosis risk