Many producers in Wisconsin are in the midst of or finishing up their calving season and preparing for breeding. During this time they may not prioritize management factors prior to breeding that will optimize fertility and lead to a successful calf crop the following year.
If you are experiencing open cows or an extended calving season with an increased percentage of the herd calving late you may want to focus on management factors during the prebreeding period. In general, a strong vaccination program and good nutrition will set you up for reproductive success.
Your vaccination program should be specific to your herd and developed with a veterinarian. Prebreeding vaccinations should occur > 4 weeks before the start of your breeding season depending on if they are killed or modified live and consider addressing Leptospirosis, Vibriosis, Infectious Bovine Rhinotracheitis (IBR) and Bovine Viral Diarrhea (BVD).
Body Condition Scoring (BCS) can be used to evaluate your nutrition program by accessing the amount of condition or stored energy a cow is carrying.
The management of yearling heifers, first calf heifers and cows will often vary and is dependent on their stage of production.
Heifers are the replacement females that have the most impact on the future of your cow herd and as such you will want to manage these important future producers accordingly. Heifers should be selected based on the specific management goals for your operation but in general selection for adequate development including proper weight and moderate frame will improve the fertility and ultimately the longevity of this female in your operation.
Heifers calving as 2-year-olds will need to reach puberty between 12 and 14 months of age and be 65% of their mature weight at breeding between 14 and 16 months of age. In order to reach puberty, weight and age are important but other management factors to consider include Reproductive Tract Score (RTS) and pelvic measurement. RTS accesses the physical development of the reproductive system including the uterine horns and ovaries. The numerical score, 1 (immature) to 5 (cycling), is assigned by a veterinarian and determined through rectal palpation. The area of the pelvis has an effect on dystocia and measurement at yearling age has been reliable at indicating potential calving difficulty. Pelvic area is determined by measuring the height and width of the pelvis rectally with a pelvimeter. Producers can use RTS and pelvic measurements as tools in their selection process with heifers scoring a RTS of < 3 or in the bottom 10-15% pelvic measurement as potential culls.
If less mature heifers have a valuable phenotype that you would like to breed consider using a synchronization protocol with progesterone such as MGA or a CIDR to help initiate cyclicity. These protocols are also advantageous in anestrous first calf heifers and cows. In general, if cattle are cycling then other protocols can be utilized to synchronize estrus.
First calf heifers have the most difficulty returning to estrus by 26 months for rebreeding because they are facing the greatest nutritional demand. At calving, these 2-year-olds should be 85% of their mature weight and be at a BCS of 6. First calf heifers require additional condition because they will prioritize body maintenance then growth followed by lactation over reproduction.
Cows also need adequate condition but are at their mature body size and can calve in at a BCS of 5. In addition to having an effect on resuming cyclicity, BCS can also have an effect on colostrum and milk production with cows calving at a BCS < 5 having reduced colostrum production. This will ultimately affect your calf crop. With feed supplies limited, it is advantageous to separate cattle based on stage of production and body condition for feeding.
Source: Katie Pfeiffer, Sauk County Ag Agent, recently appeared in the Wisconsin Agriculturist