Thermal Mechanisms Preventing or Favoring Multiple Ovulations in Dairy Cattle

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. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

To what extent does photoperiod affect cattle reproduction? Clinical perspectives of melatonin administration

The seasonality of reproduction in most mammals is dictated by photoperiod, temperature and nutrition. Melatonin, mainly synthesized in the pineal gland, is generally accepted as the active mediator of photoperiod responses including reproduction. While non-pregnant heifers and cows show continuous sexual activity and are therefore not seasonal breeders, it has been suggested that photo-periodicity may influence the appearance of puberty in heifers and the onset of parturition. Further, the light/dark ratio may influence endocrine patterns of gestation and a shorter light period correlates with the incidence of twin pregnancies. This review considers specific aspects of the effects of photoperiod and melatonin on reproduction in dairy cattle and discusses the clinical applications of melatonin

Control of Estrus in Gilts and Primiparous Sows

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The Effect of Ambient Temperature on Conception and Milk Performance in Breeding Holstein Cows

The aim of this study was to identify the effect of ambient temperature and season of the year on conception difficulties in Holstein cattle. The experiment was conducted on the School farm in Žabčice. Data were collected from July 2016 to January 2017. Experimental population counted 263 breeding Holstein cows, which were inseminated during the observation period. Results of this study confirmed the effect of temperature and season on conception rates in dairy cows. In winter season, successful conception was recorded in 56.36 % of cows in average ambient temperature 1.48 oC, in summer season the conception rate was only 40.43 % in average daily temperature 18.96 oC. A more detailed analysis revealed the highest conception rates in the dairy cows in January (88.24 %) and February (91.67 %). On the contrary, the worst results were recorded in September (22.73 %) and October (28.57 %). Evaluation of conception rate according to ambient temperature intervals showed best results for the temperatures below 5 oC. A part of the study was also evaluation of an association between daily milk yield and conception rate. This hypothesis cannot be conclusively confirmed, because milk yield was mostly similar in both groups (pregnant and non-pregnant) on the days of insemination. The effect of lactation order and mean daily milk yield on the conception rate in cows was not confirmed.O

Effect of melatonin administration prior to calving on milk secretion in the next lactation in dairy cows

This study evaluated the effects of melatonin administration 60 days prior to expect calving (drying-off period) on milk yield during the next lactation. Sixty dairy cows were treated with subcutaneous melatonin implants during summer (n=30) or winter (n=30) period. Another 60 animals were not treated and served as the control. There were no differences in the average milk yield between treated and untreated animals (44.5±3.7 and 44.8±5.0 kg/day for melatonin and control cows, respectively). There was an effect of season with a higher winter milk yield than in summer (43.8±5.0 and 47.1±3.0 kg/day for melatonin and control groups, respectively). The interaction between melatonin and season showed no significant effect; however, during winter, milk yield tended to be higher (P=0.06) in control cows than in melatonin treated cows (45.3±3.7 and 49.2±3.0, respectively). This study indicates that treatment with melatonin prior to calving did not modify milk yield during the following lactation. Only a tendency for a reduction in milk yield during winter was observed in melatonin treated cows

Nota introduttiva n. 11 – ottobre 2012

Storia e satira. Una relazione complessa La satira è una pratica discorsiva complessa e multiforme, una forma d’espressione “di confine”, a cavallo tra diversi media, linguaggi e obiettivi. Questo carattere si evidenzia a partire dall’incerta definizione del termine che, in prima battuta, può essere ricondotto ai mitici satiri romani (sàtyros) – la cui natura demoniaca e priapesca rimanda alla sfera della lascivia, dell’aggressività e del sovvertimento delle regole – ma anche alla lanx satura..

Effect of utilization of single or double prostaglandin administration within an ovsynch fixed-time artificial insemination protocol during summer season in dairy cows

This study investigated the fertility of dairy cows during summer season after treatment with a single or double PGF2α in a progesterone (P4)-based Ovsynch protocol for fixed-time artificial insemination (FTAI). The data were compared to a treatment effectuated during winter season. Two groups of 60 dairy cows each were randomly assigned on day 60 post-partum to single PGF2α or double PGF2α group. At removal of the P4 treatment the single PGF2α group received a single dose and the double PGF2α group received two doses of PGF2α at 24 hours apart. In each group, 30 cows were treated during the summer (June, July and August) and 30 cows during the winter (December, January and February) season. During summer season a double PGF2α dose did not influence pregnancy rate at FTAI but improved cumulative pregnancy rate 60 days after FTAI (43% vs 69% for single PGF2α and double PGF2α administration, respectively; P<0.05). During winter season the single or double PGF2α administration did not modify PR or cumulative PR. In conclusion, during summer the utilization of a double instead of single PGF2α treatment into a P4-based Ovsynch-FTAI protocol did not increase pregnancy rate at FTAI but improved cumulative pregnancy rate

Thermal Mechanisms Preventing or Favoring Multiple Ovulations in Dairy Cattle

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.This research was funded by “Fondo Locale per la Ricerca-FIL 2020/2021” University of Parma, Italy (coordinator F.D.R.)

Postotak koncepcije nakon primjene Ovsynch protkola s točno određenim vremenom umjetnog osjemenjivanja s aplikacijom egzogenog progesterona u cikličnih mliječnih krava tijekom toplog i hladnog razdoblja godine

Progesterone plasma levels during the warm period of the year (summer) are more variable and this can induce a reduction in the fertility of dairy cows. Therefore, the aim of this study is to investigate the effect of the combined use of progesterone supplements with an Ovsynch and FTAI protocol on conception rates during the summer in cows. The data were compared with treatments carried out during the cold season (winter). In total, 120 cows underwent oestrus synchronization by using an Ovsynch and FTAI protocol. After this, one group of 60 cows received progesterone supplements and another group of 60 cows did not. In each group, 30 cows were treated during the summer and 30 cows were treated during the winter. All cows were pre-synchronized with PGF2α 25 days and 11 days before starting the Ovsynch protocol. The conception rate at days 30 and 40 post-insemination was not changed by the Ovsynch protocol being supplemented with progesterone. No interaction between progesterone supplementation and the season (winter or summer ) was observed (P=0.17). The results of the study indicate that in cyclic cows with a functional corpus luteum the supplementation of the Ovsynch- FTAI protocol with progesterone did not improve the conception rate during the warm or cold seasons.Koncentracije progesterona u plazmi u mliječnih krava tijekom toplog razdoblja godine (ljeto) više variraju što može prouzročiti njihovu smanjenu plodnost. Stoga je cilj ovoga rada bio istražiti učinak aplikacije egzogenog progesterona u ovsynch protokolu u kombinaciji s točno određenim vremenom umjetnog osjemenjivanja (TOVO) na postotak koncepcije u mliječnih krava tijekom ljetnog razdoblja. Podatci su bili uspoređeni s istom kombinacijom protokola tijekom hladnog razdoblja godine (zima). Ukupno je u 120 krava sinkroniziran estrus klasičnim ovsynch i TOVO protokolom. Nakon toga, u 60 krava je apliciran egzogeni progesteron, dok u ostalih 60 krava nije apliciran spomenuti pripravak. U svakoj je skupini 30 krava tretirano tijekom ljeta i 30 krava tijekom zimskog razdoblja. Sve su krave bile podvrgnute postupku presinkronizacije s PGF2α 25 dana i 11 dana prije početka ovsynch protokola. Aplikacija egzogenog progesterona u kombinaciji s ovsynch protokolom 30. i 40. dana nakon umjetnog osjemenjivanja nije utjecala na postotak koncepcije. Nije ustavljena značajna povezanost između dodatka egzogenog progesterona i godišnjeg doba (zima ili ljeto)(P=0.17). Rezultati ovog istraživanja pokazali su da aplikacijom egzogenog progesterona u kombinaciji s ovsynch-TOVUO protokolom nije poboljšao postotak koncepcije u krava s cikličnom aktivnosti jajnika (funkcionalno žuto tijelo) tijekom toplog ili hladnog dijela godine