Transfer of a single embryo versus drainage of subordinate follicles to prevent twin pregnancies in dairy cows. Why not both?

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While cows are predominantly monovular, over the past 30 years the incidence of multiple ovulations and thus twinning has increased considerably alongside milk production. Multiple pregnancies are not desirable as they negatively affect the health of cows and the herd economy. Although causal mechanisms associated with multiple ovulations have been extensively revised, the process of multiple ovulations is not well understood. Recent studies on the thermal biology of the reproductive system have shown how thermal mechanisms may prevent or favor multiple ovulations. This review focuses on this relationship between thermal dynamics and multiple pregnancies. Cooling of the pre-ovulatory follicle is able to regulate ovulation. In effect, pre-ovulatory local cooling of the female reproductive system favors male and female gamete maturation and promotes fertilization. Thermal stress is proposed here as a model of stress. Periods of high ambient temperature affect the processes of pre-ovulatory follicular cooling and multiple ovulations. While the ratio between unilateral and bilateral multiple pregnancies is normally close to one, under heat stress conditions, this ratio may be 1.4 favoring unilateral multiple pregnancies. A ratio approaching unity is here proposed as an indicator of cow wellbeing.

Section: Discussionmentioning

confidence: 99%

Thermal Mechanisms Preventing or Favoring Multiple Ovulations in Dairy Cattle

Rensis

Morini

García-Ispierto

et al. 2021

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“…Interest (or absence of interest) of twin reduction has been discussed in a recent commentary [ 42 ]. To improve herd economy, induced twin reduction is the best management option and the use of a luteolytic agent to induce abortion upon a diagnosis of twins that may be a further suitable option [ 6 ], but, more effectively, would be to prevent twin pregnancies via transfer of a single embryo or drainage of subordinate follicles at insemination [ 43 , 44 ]. Lastly, although twin births are lowly heritable in dairy cattle [ 9 , 35 , 45 ], artificial insemination centers could play a key role by considering twin pregnancy as a genetic trait in sire-selection programs.…”

Section: Discussionmentioning

confidence: 99%

Twin Pregnancies in Dairy Cattle: Observations in a Large Herd of Holstein-Friesian Dairy Cows

López‐Gatius¹,

García-Ispierto

Hunter

2020

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Multiple pregnancies have devastating consequences on the herd economy of dairy cattle. This observational study examines incidence patterns based on data from the ultrasonographic examination of 1130 multiple pregnancies in cows in their third lactation or more carrying twins (98.8%), triplets (1.1%), or quadruplets (0.08%), and 3160 of their peers carrying singletons. Cows became pregnant following a spontaneous estrus with no previous hormone treatments. Irrespective of a significant decrease (p < 0.0001) in the conception rate (28–34 days post-insemination) during the warm period of the year, the multiple pregnancy rate was similar for both warm (26.5%) and cool (26.3%) periods. The incidence of unilateral multiple pregnancies (all embryos in the same uterine horn) was higher than that of bilateral pregnancies (at least one embryo in each uterine horn): 54.4% versus 45.6% (p < 0.0001). This difference rose to 17% during the warm season (p = 0.03). Pregnancy was monitored in unilateral multiple pregnancies until abortion or parturition (n = 615). In the warm period, the parturition rate was 43% compared to 61% recorded in the cool period (p < 0.0001). Thus, a warm climate is the main factor compromising the fate of multiple pregnancies. Some clinical suggestions are provided.

“…Having discussed management options after diagnosing a twin pregnancy, the best option would still be a well-designed twin pregnancy prevention program. Promising candidate strategies for this purpose are drainage without suction of co-dominant follicles at the time of insemination or transfer of a single embryo [46,47].…”

Section: Discussionmentioning

confidence: 99%

Twins in Dairy Herds. Is It Better to Maintain or Reduce a Pregnancy?

López‐Gatius¹

2020

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Multiple ovulations and so multiple pregnancies have increased recently in dairy cattle. The incidence of the double ovulation impact in high producers at insemination may be over 20%. Twin pregnancies are undesirable as they seriously compromise the welfare and productive lifespan of the cow and herd economy. Clinical problems extend from the time of pregnancy diagnosis to pregnancy loss, abortion or parturition. Early pregnancy loss or abortion of multiple pregnancies lead in most cases to culling. In cows reaching their term, mean productive lifespan is up to about 300 days shorter for cows delivering twins than for cows delivering singletons. While there is an urgent need to address multiple pregnancy prevention procedures in the foreseeable future, the incidence of twin pregnancies continues to rise in parallel with increased milk production. Herein, we review two contrasting measures proposed for the time of twin pregnancy diagnosis: (1) gonadotropin-releasing hormone treatment for pregnancy maintenance, or (2) embryo reduction. These options are discussed in terms of their implications for individual animal health and herd economy. Our main conclusions find that manual twin reduction has proven to be the best management option, whereas the use of prostaglandin F2α for inducing abortion may be a better option than doing nothing.