Missing heat symptoms, at the time when insemination ought to be able to be started after calving, is called ‘anoestrus’. Cows that are on silent heat for 60-70 days after calving, are classed as problem cows. Ovarian cysts can be classified as either follicular or luteal cysts.
While some cysts persist for long periods, most will regress and be replaced by new cysts during sub-sequent follicular waves.
Anoestrus and cysts are associated with a lower insemination and pregnancy percentage, plus a greater probability of being at risk of such due to failure to become pregnant.
Classifying the problem
One should be aware that problems with anoestrus can be confusing if you do not see signs of oes-trus. To be able to diagnose problems with anoestrus, it is therefore important to ascertain, by checking for signs of oestrus many times a day and for a sufficiently long time.
The proportion of cows with hoof/feet & leg disorders is key, as cows with such problems can have a reduced capacity for oestrus, and when considering the correlation between lameness and the presence of cysts.
Heifers of big breeds > 17 months, Jersey heifers > 15 months and cows > 70 days from calving, that have not shown cyclical activities, ought to be examined.
Anoestrus can be related to health problems in connection with, and during the course of, the first month after calving. Added to which, the degree and speed of loss of body condition in early lactation is one of the most significant risk factors that lead to delayed cyclical activity, anoestrus and cysts. In other words, all these have a negative effect on feed intake and will increase the risk of these problems arising.
The mechanisms behind the two types of cysts (follicular and luteal cysts) are basically the same and are mainly blamed on a hormonal imbalance during the course of follicular maturation. The formation of cyst like structures can, however, seemingly be caused by several different mechanisms, and a correla-tion between lame cows and the occurrence of cysts has been found.
Points for action plan
The most effective method to limit the occurrence of anoestrus and cysts, is prevention.
- Have the cows missed oestrus – or is oestrus being overlooked?
- Examination of post calvers in the first 10 days after calving
- Degree and speed of loss of body condition in early lactation
- Proportion of lame cows in the herd