To start a new lactation period, cows must calve down (give birth). From this, a heifer (female) or bull (male) calf is born. Heifer calves are reared to replace cows leaving the herd. Heifer rearing starts at birth and ends at her first calving.
The newly born calf has to be treated like a baby, especially during the first two months of its life. Within six hours after birth, help the calf to suckle from the mother or milk the cow by hand and feed colostrum to the calf using an artificial teat. Colostrum is the first milk produced after calving. It contains antibodies against diseases that the mother was exposed to during her pregnancy. This provides a passive immunity to calves during the first weeks of their lives.
Colostrum also has a higher solid content than standard milk, e.g. 24% versus 13%, because of higher fat and protein levels. Milk solids become less after 24 hours. While the direct absorption of antibodies stops after 6 - 8 hours, colostrum provides protection within the stomach and should be fed for as long as it is produced by the cow.
After 24 hours, put the newly-born calf into a calf pen (1.0 wide x 1.8 m long) with dry bedding such as straw or sawdust. Pens must have 1.2 m high walls on three sides and a roof of 1.5 m high. Replace wet bedding once a day with dry straw. Keep calves in the pens until 3 months of age, after which heifers can be kept in groups. Milk feeding, using whole milk or milk replacer, continues after colostrum feeding. Feed 2 to 3 litres of milk to each calf in the morning and afternoon.
Warm milk can be fed to calves directly after milking the cows. While an artificial teat can be used, calves can also be trained to drink from a bucket. Sterilize and dry drinking utensils after each feeding to prevent pathogens from spreading among the calves. Keep on milk feeding until weaning at about 2 to 3 months of age. Stimulate starter meal intake by not increasing the daily amount of milk during weaning.
To begin weaning, feed a calf starter meal (with 18% crude protein) from about seven days of age. Start by giving about 150 g of starter meal (large coffee mug) into a dry feed bin once a day. Teach calves to eat from the bin by rubbing some of the dry feed on their noses. By licking its nose, the calf recognises the feed. Give fresh feed every day. Increase the amount daily when all is eaten. Remove old feed as it becomes mouldy very quickly because of saliva. Wean calves from the milk when their starter meal intake reaches 1 kg/day.
Start feeding about 0.5 kg/day of ground hay from two months of age to encourage forage intake. Change to a growth meal (16% crude protein) from three months of age. A calf growth meal (15% to 16%) has less crude protein than that of a starter meal (e.g. 18%). Increase the amount of growth meal once a week. Daily feed intake increases as heifers get older, starting at 3 kg at 3 months to 18 kg per day at 24 months of age.
Heifers can be put on pasture and fed about 1 kg of concentrate per day at 12 months of age. After 12 months of age pasture feeding only should be sufficient. A sufficient amount of pasture (such as kikuyu or ryegrass) should be available; otherwise, it should be supplemented with hay or silage. When no pasture is available, a total mixed diet must be fed.
The amount and concentration of diets should be fed according to specific age groups as this changes as heifers get older. Weigh heifers regularly to determine whether the feeding programme is correct. Inseminate heifers once they weigh 300 - 330 kg or when they've reached 12 - 14 months of age. This should ensure first calving at about 24 - 25 months of age.