Variation in the interservice intervals of dairy cows in the United Kingdom

Abstract

An understanding of the normal estrous-cycle length of the cow is important when managing and monitoring dairy-herd fertility. Although the normal interovulatory interval is widely considered to be 21 d, some studies have found alternative intervals to be more prevalent; previously, most of the variation in interval length was expected to be between cows. The aim of this study was to assess the time between inseminations (interservice interval, ISI) in a large number of dairy cows and to explore possible associations between cow factors and estrous-cycle length. The study used ISI data from 42,252 cows in 159 herds across England and Wales. Univariate analysis of the subset of 114,572 intervals between 15 and 30 d (a range covering the increased frequency of ISI occurring at the expected time of the first return to estrus) following an insemination revealed a modal ISI of 22d. Primiparous heifers had a modal ISI of 21 d. Significant differences existed between the distribution of ISI for different yield groups, parity numbers, and the number of inseminations. Multilevel regression modeling was used to evaluate the associations between cow factors and ISI, while accounting for clustering at the herd and cow level. This revealed significant associations between predicted ISI and insemination number, days in milk, lactation 305-d milk yield, and month and year of insemination. Variance partition coefficients indicated that only 1% of variation in ISI was at the herd level, 12% at the animal level, and 87% at the insemination level, indicating that cycle length varies substantially more between cycles within a cow than between cows or herds. These findings suggest the normal range of ISI for modern UK dairy cows is longer than expected and cycle length has a large amount of unexplained variation within individual animals over time.

Embryo Mortality Around the Period of Maintenance of the Corpus Luteum Causes Alterations to the Ovarian Function of Lactating Dairy Cows

“…Unquestionably, the greatest detriment to cow reproductive performance is embryo loss. Nevertheless, cows that lose their pregnancy may also exhibit alterations in ovarian function leading to delayed estrus expression and re-insemination [4][5][6]. Pregnancy loss may also be responsible, at least in part, for the poor response to synchronization of estrus and ovulation treatments used for previously inseminated non-pregnant cows [7][8][9][10].…”

Perspectives on pasture versus indoor feeding of dairy cows

“…As milk yield has increased in high‐producing dairy cows over the past decades, infertility has become a major concern and is now considered to be one of the most significant problems on dairy farms . The replacement rate in the United Kingdom increased from 25% to 33% between 1990 and 2010 .…”

“…43 As milk yield has increased in high-producing dairy cows over the past decades, infertility has become a major concern and is now considered to be one of the most significant problems on dairy farms. 44,45 The replacement rate in the United Kingdom increased from 25% to 33% between 1990 and 2010. 46 In 2013, the cull rate for cows reached 38% in the US, which translates to an average productive life span of only 2.63 years or 31.6 months.…”

A description of interestrus and interservice intervals and associated fertility in 16 United Kingdom dairy herds

“…However, with recent work demonstrating marked differences between the reproductive traits of the modern dairy cow and her genetically distant predecessors, it is plausible that these parameters may no longer accurately describe the dairy cow's estrous cycle (Royal et al, 2000;Lopez-Gatius, 2003;Pryce et al, 2004). Indeed, recent work has shown that interservice interval has a mode of 22 d, with an upper range of 28 d (Remnant et al, 2015). However, this data set focused exclusively on interservice interval and did not examine intervals following estrus events with no insemination.…”