Breeding management
Heifers should be ready to breed as they approach 15 months of age so that they calve at 24 months. Research has shown that the weight of a heifer at service can have an effect on subsequent fertility (Table 7).
Table 7. Effect of body weight on calving rate (Friesian heifers)
| % calvings to first serve | % not in calf | |
|---|---|---|
| Less than 260 | 21 |
33 |
| 260 – 299 | 47 |
13 |
| 300 – 339 | 59 |
8 |
| More than 340 | 57 |
7 |
Source: Agricultural Development and Advisory Service (ADAS)
The keys to a successful heifer breeding programme include:
- Proper nutrition
- Minimising stress
- Efficient heat detection
- Timely inseminations
Heifer replacements at Greenmount Campus are selected for insemination on the basis that they are approaching 15 months of age, weigh 360 - 400 KG and have a corresponding wither height of at least 125 cm for autumn born heifers. A number of spring born heifers may be inseminated between 13 - 15 months of age provided that they meet the weight and wither height criteria set out for the autumn born animals. Target body condition score for animals at this stage is 2.5 – 3.0. Housing occurs at least six weeks before service and animals at this stage are introduced to the winter diet to help them settle into their environment. Proper nutrition is important at this stage and the animals are put on a rising plane of nutrition. The diet at this stage is made up of ad lib silage plus 1.0 - 2.0 KG of an 18 percent CP heifer rearing compound. Silage for the heifers is made according to the following targets:
- Good intake characteristics (intake value* 80 +)
- Medium to high DM (greater than 25 percent)
- Medium to high energy concentration (ME 11.0 + MJ/KGDM)
* Based on the Hillsborough Feeding Information System
Target growth rates at this stage are around 0.80 - 0.85 KG/day. Visual heat detection is carried out up to four times a day at the Campus when animals are in the house and all observed heats are recorded. Inseminations are carried out within 12 hours of standing heat. Heifers are inseminated using artificial insemination up to two times. A sweeper bull is used on any heifers not holding to a second insemination. AI sires are selected on the basis that they meet the criteria set for the projects at Greenmount Campus without causing increased calving difficulties. The repeated use of easy calving sires is avoided as this may cause difficulties within the herd in the long term. Once heifers are confirmed in calf, concentrate level is reduced and phased out as animals approach turnout.
Select AI sires according to criteria that meet the needs of your farm
Heifers can also be reared successfully on straw based systems. Levels of concentrate feeding in this situation vary according to the age of the animal.
Oestrous synchronisation programs
An oestrous synchronisation program may be required for heifers on rearing units that are not close to the farm and where it is difficult to regularly observe animals. Methods of oestrous synchronisation include:
- Prostaglandin system - animals are observed for signs of oestrous during the first six days of the programme. Animals which are observed in heat at this stage are inseminated. Heifers which have not been observed cycling by day seven are injected with prostaglandin. Heat detection and inseminations are carried out between days 10 - 17. Heifers which have not been observed in heat by day 18 are injected at which point all cycling heifers should respond returning to heat over a four day period.
- CRESTAR - this program involves administering a progesterone implant beneath the skin of the ear of the heifer. An oestradiol injection is also given. The implant is removed 9 - 11 days later and animals are inseminated 48 hours after the removal of the implant.
- PRID and CIDR programs - a PRID or CIDR containing progesterone and oestradiol is inserted in the vagina of the heifer. After 12 days the device is removed. Inseminations are carried out 48 and 72 hours later after removal of the PRID or CIDR or once only at 56 hours after their removal.
Consult your local veterinarian on the program which best suits your system.
Housing
Housing for heifers reared through their second winter should have the following features:
- Good natural ventilation
- Adequate space
- Cubicles should be designed to encourage animals to lie in them - Holstein animals require cubicles as large as 2.2 x 1.2 m
- Restraining facilities for treatment and breeding
Cost effective heifer accommodation
Heifers can easily be restrained using self locking yokes
Heifers being reared through their second winter at Greenmount Campus are housed in a kennel house with solid floors. Housing heifers that are expected to come into heat on slatted houses may limit oestrous (bulling) activity compared to solid floor housing. Cubicles are fitted with comfort mattresses to improve animal comfort. Self locking yoke gates have been fitted along the feeding passages to allow operators to restrain heifers for artificial insemination and pregnancy diagnosis.
