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Abstract
The most effective and economical use of the principles of oestrus synchronisation requires the pre-treatment identification of normally cycling animals. This identification can be conveniently achieved either by using bulls fitted with chin-ball harnesses or by ‘tail-painting’ in the pre-treatment period. Both procedures mean that groups of cycling animals can subsequently be either: (i) treated with a single prostaglandin injection and then inseminated twice 72 and 96 h later (single-double system); or inseminated once at an observed post-treatment oestrus (single-single system); or (ii) synchronised using a progesterone-releasing intravaginal device (PRID), supplemented with oestrogen, over a 10-day period and then inseminated once at 56 h after PRID removal.
The prostaglandin systems are simple to apply and can be effectively monitored by the herd owner's veterinarian. Their economic value will vary with the particular purpose for which they are being used and the type of animal being treated. A number of these situations are described, but aspects such as time-saving and convenience may be as important as cost in influencing the frequency of their use.
Management problems associated with suckling beef cows and the variable incidence of post-partum anoestrum currently limit the use of oestrus synchronisation in this class of cattle. The use of the PRID in conjunction with temporary calf removal may be elements of the most successful system.
