ANSC460 replacement heifers

3 assumptions for growing dairy heifers

• optimal age at first calving

• excessive rates of gain may result in reduced lifetime productivity

• minimize cost of raising replacement

advantages of enhanced growth rates

• faster return on capital investment

• savings on labour, feed costs

• reduction in number of heifers needed

• increased lifetime production

• faster genetic gain

goals with replacement heifers

• low economic and environmental cost

• not compromising future lactation

• achieve proper body size

• breeding BW vs days on feed

• prevention of metabolic disorders in transition period

target growth

• ensuring rate of gain meets nutrient requirements and rate of gain to reach desired mature size

age at first calving

• >23months no diff in 1st lactation yield

• <22months reduces milk yield

age at first calving and DOF

is variable and dependent on repro efficiency distribution of the herd.

weaning → puberty

• puberty 11-12months

• good quality grain feed + high quality forage

• feed efficiency decreases overtime

• group housing post-weaning

• >3months can consume silage but susceptible to forage quality

high-protein, high-grain

• get preg faster

• lowers milk yield

• may lead to over-conditioned heifers (increase dystocia)

close-up heifers

• separated 4-3wks pre-calving

• separate pens

• heifers are still growing

• pregnancy requirements

• adequate bunk space required

• feeding anionic salts (DCAD)

feeding heifers

• mostly forage based diets

• monitoring growth and environmental conditions (adjust diets)

• dietary energy and protein, variable requirements

• limit feeding

• avoidance of excess protein supp.

• careful inclusion of P

limit feeding/precision feeding

• limited to 70-90% of ad lib DMI

• increase feed efficiency

• decrease nutrient excretion

• maintain heifer growth

downside of precision feeding

can be an expensive diet