Nutrition of Heifers

A successful dairy feeding system is defined as one that delivers the needed nutrients to each cow at the correct time (stage of lactation) to maintain maximum milk production. No one system is correct for all dairy producers. The feeding system selected must consider the delivery of forages, grain, protein and minerals, either individually or in various combinations.

Heifer Nutrition

Rearing the calf from 12 weeks to 1 year 

Free-choice forage and limited grain can be fed during this period of the herd replacement's life. The amount of grain and protein content of the grain mix needed will be determined by the quality of forage(s) being fed. Pasture can be used successfully in the feeding program, but it should not be expected to supply all of the nutrients for calves in this age group. A grain mix and some stored forage are desirable for calves less than 6 months old on pasture. If heifers cannot be grouped, a creep feeder is an option. The inclusion of low-energy bulky feeds in the creep mix may be necessary to avoid excess energy intake with free choice feeding. Trace mineralized salt and a calcium-phosphorus supplement can be offered free-choice if not adequately supplied in the grain mix. All calves must have access to clean, fresh water. 

During this stage of the feeding program, avoid overfeeding grain and allowing calves to become fat. Over-conditioned heifers produce less milk in later life than those reared on a more moderate level of nutrition. The key period in mammary gland development is between 3 and 9 months of age. During this period, mammary tissue grows 3.5 times faster than body tissue. Heifers fed high-concentrate rations from calf hood to breeding age develop less milk secretory tissue in the mammary gland than heifers raised at normal, recommended growth rates. Fattening of heifers before puberty appears to have an inhibitory effect on mammary secretory tissue development and/or changes the endocrine stimulation of mammary gland growth. Accelerated growth rates for heifers 15 months of age and older do not affect mammary secretory tissue. Higher protein levels in the diet (14 to 16%) may help prevent over-conditioning when heifers are fed high-energy diets. 

If the protein content of forage is good, a little protein supplement will be required in the grain mix. Grain mixes prepared for the milking herd are acceptable as long as they are properly fortified with minerals and vitamins. 

Feeding program for heifers 1 to 2 years of age (to 2 months before calf down): Good quality forage should be available and only fed according to a need for heifers over 1 year of age. Trace mineral salt and a calcium-phosphorus supplement are recommended on a free-choice basis. Heifers deficient in energy, phosphorus, or vitamin A will not get/ come on heat (oestrus). 

The first oestrus in heifers is dependent on a combination of size and weight but primarily weight. A general guideline is heifers will show their first oestrus at 40% of their mature weight, which should be before 12 months of age. Heifers fed high planes of nutrition will show oestrus at an earlier age than heifers grown at recommended rates, but underfeeding of heifers will delay oestrus. Underfed or very slow-growing heifers may ovulate, but oestrus signs often are suppressed. Heifers in good condition and gaining weight at breeding time generally show more definite signs of oestrus and have improved conception rates over heifers in poor condition and/or losing weight. Over-conditioned or fat heifers have been reported to require more services per conception than heifers of normal size and weight. 

Two months before calving to calving

Heifers should move from a steady growth rate after breeding to a rapidly growing phase (2 to 3 kg /day gain) during the last two to three months of pregnancy. How heifers are fed during this period can affect milk production during the first lactation. Heifers grow rapidly at the calving time but need additional growth during the first lactation and are found to be more persistent milkers than full-sized heifers at calving. Also, heifers slightly undersized at calving (80% of normal) will reach full milk production potential and normal size if fed sufficient nutrients for both growth and milk production during lactation. 

The exact amount of grain to feed before calving depends on the forage quality, size, and condition of the heifer. A thumb rule would be to feed grain at 1% of body weight starting about 6 weeks before calving. Be sure rations are balanced in protein, minerals, and vitamins. Excess salt intake can contribute to udder oedema and should be avoided during the last 2 weeks before calving. 

Well-grown heifers will have a minimum of problems at calving, but the ease of calving can be affected by the plane of nutrition in two ways: 1) an effect on calf size, and 2) an effect on the fatness of the dam. At equal body weights, fat, over-conditioned heifers are almost always younger and consequently will have less skeletal growth than leaner, normally grown heifers. Thus, fat heifers have higher dystocia rates because of small pelvic openings and usually a larger-than-normal-sized calf at birth. Underfed or poorly grown heifers will also require more calving assistance and have a higher death rate than normal-sized heifers.