The voluntary waiting period (VWP) is a designated interval between calving and the first postpartum insemination, typically lasting between 50 to 80 days depending on the farm’s management strategy. The primary purpose of the VWP is to allow the cow adequate time to recover from the stress of calving, restore her energy balance and return to normal reproductive function.
Extenging the VWP can increase the likelihood of successful conception on the first insemination, reducing the number of inseminations required and the amount of semen used, leading to cost savings. However, VWP remains debated, making it essential to assess its efficacy in delivering benefits and identifying any unforeseen challenges.
Fertility metrics
Key fertility metrics such as estrus intensity, first-service conception rate, number of inseminations per conception and insemination period length serve as vital indicators in assessing a cow’s reproductive performance.
Estrus intensity refers to the strength and visibility of the signs of estrus (heat) exhibited by cows. This is an important factor in fertility management, as stronger and more obvious signs of estrus make it easier for farmers to accurately detect when a cow is in heat, thereby timing insemination more effectively to enhance the chances of successful conception. Signs of estrus can include behaviors such as mounting other cows, increased activity, vocalization and mucus discharge.
Previous university studies, however, have yielded mixed results regarding the effects of extended VWP on fertility outcomes. The data has often been confounded by variations in study methodologies and cow demographics. Moreover, the impact of extended VWP on health indicators and culling rates remains inconclusive, further complicating the assessment of its overall efficacy.
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