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If more than 20 of cows are conceiving in the third cycle, further investigation is needed to rectify the issue.
BCS of breeders at the beginning of mating is a key factor in the resultant calving pattern, with cows in BCS
3.0 or higher more likely to conceive during their irst cycle than cows in BCS 2.5 or less.
For both bulls and cows, checklists have been developed to ensure that all of the premating and mating
requirements of these animal can be met leading up to and during joining. These are provided in TECHNICAL
NOTE 10 - Preparations for Breeding.
5.4.4. Mating After Calving
The period between a cow calving and her return to oestrus cycling ranges from 30-72 days. For a cow to
calve on the same date each year, she must conceive again within 80 to 85 days of calving. Therefore there
is only a narrow window of opportunity between return to oestrus and the desired conception date to achieve
a 365-day calving interval. Management of the breeding cow’s body condition score throughout the calving and
re-mating period is essential to achieve high conception rates in lactating cows. Ideally, cows should have a BCS
of at least 2.5 and preferably 3.0 at the time of re-mating. This also means that their BCS should be at least 3.0
when they calved. Cows with a BCS falling to 2.0 or below following calving have a signiicantly reduced
chance of conceiving again within the desired mating period.
5.4.5. Using Artificial Insemination in the Reproductive Cycle
Artiicial insemination AI provides a breeding enterprise with access to industry-leading genetics that would
not otherwise be available to most herds. AI is also an efective means of widening the genetic base within
herds that rely heavily on bulls bred in the local area from a limited gene pool. However, a high level of
management is required if the enterprise is going to capitalise on the higher costs of calf production from
artiicial breeding. AI is most commonly used with heifers, as they:
• Are usually in ideal body condition at joining because they are not lactating
• Are the most genetically advanced generation in the herd
• Managers can select from a wide range of sires with desirable traits such as ease of calving.
5.4.6. Pregnancy Detection
Two common methods of pregnancy detection are manual palpation Fig. 5.13, and ultrasound. Manual
palpation involves an operator manually feeling the uterus, via the rectum, for evidence of a pregnancy,
while ultrasound machines use either an external or internal probe to provide an image of the uterus for the
operator to examine for signs of pregnancy. Pregnancy status can also be determined through measuring the
progesterone levels in blood or milk. Heifers can be pregnancy tested by manual palpation
from six weeks 42 days after the last day of mating, while older cows should wait eight weeks 56 days. All
females can be diagnosed using ultrasound from one month 30 days after the last day of mating.
Check for multiple births when pregnancy testing so these females can be managed accordingly. Multiple
births are very risky for cattle and close supervision is required to minimise calving diiculties.
More practical details on pregnancy detection are provided in TECHNICAL NOTE 11 - Pregnancy Testing.
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5.5. Calving Management
