Breeding seasons in summer rainfall areas

Cows usually reach their optimal breeding condition about three months after the month of the highest rainfall.

The breeding season should therefore be timed to coincide with this.

For a summer breeding season, you should achieve the highest re-conception rate if the cows calve about one month before to about one month after the first good rain has fallen.

For example, if it usually falls in October, cows should calve from September to November. This means that the breeding season should be from 15 November to 15 February.

If you don’t have a breeding season and want to establish one, use the current calving pattern of the herd as a guideline. Determine in which three consecutive months most calves are born, and use this to calculate the optimal period for the breeding season.

In general, the breeding season in drier regions (where the rain usually starts later in the season) should be later than in wetter regions (where the rain usually starts earlier in the season).

The timing of the breeding season should also be governed by the availability of planted pasture, crop residue and silage, as well as synchronisation with other farm activities such as planting and harvesting.

Advantages of a summer breeding season
Except for breeding heifers at 18 months of age (in winter), a summer breeding season is usually better than a winter one for the following reasons:

• Cows are normally in good condition during midsummer, resulting in higher conception rates;
• The period of a cow’s peak nutritional requirements coincides with the peak production period of natural grazing (summer), giving you a higher weaning weight;
• The period of a cow’s lowest nutritional requirements (after weaning) coincides with the low production period of natural grazing (winter), resulting in less supplementation needed during winter.

Inevitably, a summer breeding season has disadvantages too:

• The internal and external parasite load is high during the pre-wean phase of calves, resulting in lower weaning weights;
• The growth rate during the period directly after weaning (winter) is low;
• Summer droughts might mean lower conception rates due to the poor condition of cows in the breeding season.

Two breeding seasons
Another alternative is to have two breeding seasons a year. This offers a number of advantages:

• Bulls can be used more effectively;
• Cows that fail to conceive and are not culled can be mated again within a shorter time (they will skip only six months rather than a full year);
• It facilitates the mating of heifers at 18 months of age instead of the normal 24 months.

Having two breeding seasons a year also presents disadvantages:

• You may be tempted not to cull cows that have skipped, as they can be bred again within six months. This practice may result in a lower reproduction rate;
• Contemporary groups will be smaller, as the annual calf crop will be spread over two seasons;
• This approach requires greater management and more labour, as all routine practices need to be carried out twice a year.

（April 20, 2021. From “ The Farmer’s Weekly”）

• [cf7ic]