Raising dairy heifers begins with choice of a bull likely to produce animals with high genetic potential for milk. A well managed dairy farm should have as many calves born every year as there are cows in the herd. Most farmers sell males calves at an early age while the females are reared as dairy replacement heifers for the herd or as heifers for sale. Raising a high number of replacement heifers allows a dairy farmer to:
- Obtain the best replacement heifers through strict selection criteria from wide
- Expand the dairy herd at low cost (without buying heifers or cows)
- Sell excess heifers to earn
Heifers represent the future of the herd. At the same time, they are non-productive animals incurring expenditure in terms of feed, labour and veterinary services without immediate returns. Raising heifers is a financial investment that begins to bring dividends after the first calving; therefore the goal should be to make ensure proper growth rate at minimum costs to be inseminated on time in order to realize full lactation potential later in life.
Heifer raising is the second largest expenditure in a farm after the milking herd, with feed costs takes the largest share. The aim should be to rear heifers to reach the desired body weight early so that they initiate puberty, establish pregnancy, and calve easily. When feeding heifers, the farmer should aim to:
- Reduce interval between weaning and first lactation. This will increase number of calvings per lifetime (more of lactations) and lead to faster genetic improvement.
- Minimize mortality.
- Achieve a growth rate of 0.5-0.7 kg/d.
- Achieve first calving at 22 to 24 months of age
- Feeding management must ensure that heifers reach target live weights for breeding at 14-16 months of breeding at 14-16 months of age.
Combining both adequate development and early age at calving has several advantages:
- It decreases the risk of calving
- It improves lifetime milk production (days in lactation and milk production per day in lactation).
- It reduces rearing costs (feed, labour, );
- It decreases total number of heifers needed to maintain herd size
In most farms, heifers are normally the most neglected group in terms of feeding resulting in delayed calving. When heifers are fed as a group, the main problem becomes that the heifers are normally of different ages and thus aggressiveness varies. When concentrate is fed to the group, the young and weak consume less compared to others. In pasture management systems, close supervision is required due to variation in pasture quality through the seasons which may affect heifer growth rates.
Heifers can be reared on good quality pasture only as their nutrient requirements are low (growth and maintenance). Supplementation with concentrate should be at 1% of body weight. Generally the amount of concentrate given to heifers should be 1 to 4 kg depending on age (size) of the heifer and forage quality. Mineral salt supplement is recommended on a free-choice basis.
While designing a feeding program for heifers, the following should be considered:
- Puberty (thus calving) is related to size (feeding) rather than age. The consequences of poor feeding are manifested in delayed calving resulting in delayed milk
- Feeding heifers too much energy leads to deposition of fat in mammary gland tissue displacing secretory tissue resulting in reduced milk yield. The key period in mammary gland development is between 3 and 9 months of age. During this period, mammary tissue is growing 3.5 times faster than body tissue. Heifers fed high-concentrate rations develop less milk secretory tissue in the mammary gland than heifers raised on recommended
- Underfeeding heifers results in small bodied heifers which experience dystocia (difficult calving).
- Heifers calving at 24 months have a higher lactational milk yield compared to calving at an older age.
Size of animal is related to milk For twins of same genetic makeup, the heavier one produces extra milk in a lactation.
Growth rate (weight) versus age
Both under- and over-feeding heifers are undesirable during heifer rearing. Overfeeding may result in obesity, low conception rate, difficult calving and low milk production while underfeeding will result in low conception rate, poor fetal growth, difficult calving and low first lactation milk yield. It is therefore important to monitor performance of heifers, particularly the body weight change and height at withers.
Growth should be such that increase in weight is accompanied by a proportionate change in height. Growth charts allow a farmer to compare the height and weight of heifers to a standard curve that represents the average for the particular breed. This tool enables the farmer to monitor heifer performance to determine whether feeding and other management practices are adequate.
Body weight and height at withers are three important measurements used to evaluate heifer growth. The weight is estimated with a weigh band and height by graduated piece of timber as shown in the picture below.
Once the measurements are taken, they are then fitted into a growth chart which is breed specific (eg below). If the body weight falls below the band (expected), then the heifer not getting enough nutrients (energy) and vise-versa. Short heifers are an indication of low protein in the diet.
Regardless of age, puberty is reached when a heifer weighs approximately 40% of her mature body weight. Breeding however, is recommended when a heifer has reached 60% of her expected mature body weight. This is normally achieved when the heifer is 14 to 16 months old. Smaller breeds may be bred one or two months earlier than large breeds because they mature faster. Heifers in good condition and gaining weight at breeding time generally show more definite signs of estrus 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. The table below gives a guide on when to breed heifers:
Recommended age and size for breeding and calving for different dairy breeds
|Breed||Age in Months||Size in kg||Height in cm||Age in Months||Size in kg|
NB: There is a tremendous increase in weight during the 9 month. This is due to heifer growth and foetal weight
Once heifers are pregnant, feeding should be adequate to ensure proper development to avoid calving problems and poor first-lactation yield. Pregnant heifers may be maintained on good quality forage alone but concentrates should be given if the forage is of low quality.
During the last two months of pregnancy, the feeding regime can affect milk production during the first lactation. The exact amount of concentrates to feed before calving will depend on forage quality, size, and condition of the heifer. A rule of thumb the heifer should be fed concentrate at 1 percent of body weight starting about 6 weeks before calving with a ration balanced in protein, minerals, and vitamins.
Feeding concentrates allows the rumen bacteria to get used to digesting high levels of concentrate, which is very important during early lactation. If practical, concentrates should be fed in a milking parlour as this accustoms the heifer to the milking parlour.
Well managed heifers will have a minimum of problems at calving, but ease of calving can be affected by plane of nutrition in two ways:
- an effect on calf size, and
- an effect on fatness of the
Fat heifers have higher rates of difficult calving because of small pelvic openings and usually a larger-than-normal sized calf at birth. Underfed or poorly grown heifers also will require more assistance at calving and have a higher death rate at calving than normal sized heifers.
When considering housing for heifers, the following factors need to be considered:
- Convenience of feeding: Feeding from outside the house is desirable as it minimizes stress and risk of
- Cleanliness of the sleeping area: It should be easy to remove bedding or clean the sleeping
- Convenience of moving and restraining animals: Heifers go through management practices such as vaccination, dehorning, deworming, weighing, artificial insemination and they require restraint. The housing facility should meet the animal’s requirements but also make it easy to handle
From weaning to five months, the young heifers may be housed in small groups of four to five. However, the house should be sheltered, clean, have dry bedding, good ventilation and easy access to water and feed. For zero-grazing systems, the heifers may be housed in the same unit with the mature cows, but in a separate cubical fitted with feed and water trough. If they are to be housed in a separate unit, a free stall may be used but it should include outside lots for exercise and feeding.
From the sixth month, heifers may can be kept in paddocks in the pastures but watched regularly. Shelter and fenced area must be constructed to ease animal handling and restraint but the degree of protection needed will depend on weather conditions. Facilities for feeding supplemental feeds and minerals must also be provided.
Raising healthy heifers is important in all dairy production systems as health affects growth rate, fertility and hence age at first calving and milk production. Losses are also incurred in form of veterinary costs and death limiting the opportunity for selection of high quality animals and or sales. Most of the common diseases affecting calves are also important in heifer rearing and have been dealt with in the previous chapter.