Most importantly, if we wish to start breeding after the commonly used 60-day voluntary waiting period, we must effectively manage feeding during the dry period and for fresh cows.
Energy balance during the dry cow period has the greatest effect on reproduction. Most often, the dry matter intake will begin to drop approximately one week or more before calving. Therefore, we must focus our feeding practices to try to minimize that drop in intake, therefore reducing the magnitude of the negative energy balance before calving.
First, we need to examine the body condition of our dry cows. We must aim for a body score of no more than 3.5 (on a scale of zero to five). We need to continue to monitor that body score after calving to make sure cows lose less than one point of body score during the first 30 days of lactation.
Research from university tells us that the first ovulation usually occurs 10 to 14 days after calving. This is quite often when energy balance is at its lowest point. This is not all bad because the first ovulation starts the timing of subsequent ovulations.
Commonly, three ovulations will occur during the voluntary waiting period. Remember that the follicle takes about 10 weeks to fully develop, meaning the one that is released around the 60-day mark was developed during the dry period. That is why the pre-calving diet is so important for successful breeding.
Recent research has focused on the feeding of fat during the dry period, emphasizing not just any fat but the particular fatty acids that help reproduction (C-18.2). Feeding these types of fatty acids to close-up dry cows and fresh cows helps to produce prostaglandin and causes the uterus to involute.
There are several sources in typical farm feeds that contain C-18.2 fats, such as soybeans, cottonseed and my personal favourite – flaxseed. There are also several commercially prepared bypass fats available containing these fatty acids.
During lactation, producers must monitor blood urea nitrogen or milk urea nitrogen (tests are available from DHI for a fee). Keeping MUN levels in the 10 to 14 range is a good target. Levels above 18 are thought to be toxic to both sperm and embryos.
Supplying proper vitamin and mineral levels during the dry period and breeding period is essential. Research indicates that higher levels of antioxidants such as vitamin E, D and selenium increase breeding success.
Much research has also been done on the success of including proteinate chelated organic trace minerals, zinc, manganese, copper, cobalt and chelated selenium yeast for reproduction. Producers should have their present levels assessed to avoid deficiencies.
During the transition period, hypocalcaemia (mild milk fever) increases the risk for displaced abomasums, retained placenta and subsequent metritis due to lack of smooth muscle contraction. Even a mild case of metritis has been shown to increase services for conception in cows.
Focusing on not only energy balance in the transition period as well as the DCAD (dietary cation-anion difference) balance will minimize the risk for hypocalcaemia.
Commercial products are also available to help control DCAD balance and increase the cow’s natural ability to replace calcium from her own stores.
Although a number of other factors can influence reproductive success (such as heat stress, pen movement, heat detection, etc.), the critical role nutrition plays cannot be ignored. Covering the nutritional aspects we have discussed here can greatly improve the chances of successful reproduction on your farm. PD
Tom Palen
Nutritionist
Triple “P” Consulting
