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

Control of Estrus in Gilts and Primiparous Sows

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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

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

Double cloprostenol administration during mid luteal phase of oestrous cycle does not modify the interoestrous interval in gilts

The present study was undertaken to test the effect of two vulva injections of D-cloprostenol on day 7, 9 and 10 of oestrous cycle on the duration of the interestrous interval in gilts. Following a pre-treatment oestrous cycle, 87 gilts were assigned to receive vulva injections of 75 μg D-cloprostenol at 08:00 and 14:00 h on day 7 (D7; n=30), day 9 (D9; n=29) or day 10 (D10; n=28) of their second observed oestrous cycle. Across the treatments, the duration of the oestrous cycle with D-cloprostenol treatment (19.1±0.1 d) was not different from that of the previous oestrous cycle (20.1±0.4 days). Plasma progesterone concentrations were evaluated 6 h before and 24 and 72 h after D-cloprostenol treatment in the D9 group. Compared to pretreatment levels (9.6±0.4 ng/mL), plasma progesterone concentrations were reduced (P<0.05) at 24 h (6.3±1.0 ng/mL) and 72 h after treatment but complete luteolysis did not occur. These data indicate that in gilts double vulva administration of D-cloprostenol is not able to induce a complete luteolisys and hence the duration of the oestrous cycle is not modified

Učinak primjene melatonina prije teljenja na izlučivanje mlijeka tijekom laktacije u mliječnih krava

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.U ovom istraživanju procjenjivan je učinak primjene melatonina 60 dana prije očekivanog teljenja (razdoblje isušivanja) na proizvodnju mlijeka tijekom kasnije laktacije. Šezdeset mliječnih krava tretirano je potkožnim implantatima melatonina tijekom ljetnog (n=30), odnosno zimskog (n=30) razdoblja. Drugih 60 životinja nije tretirano i one su poslužile kao kontrola. Nije bilo razlika u prosječnoj proizvodnji mlijeka između tretiranih i netretiranih životinja (44,5±3,7 kg/ dan u krava tretiranih melatoninom, odnosno 44,8±5,0 kg/dan u kontrolnih krava). Postojao je učinak sezone, pri čemu je proizvodnja mlijeka bila veća zimi u odnosu na ljeto (43,8±5,0 kg/ dan u krava tretiranih melatoninom, odnosno 47,1±3,0 kg/dan u kontrolnoj skupini). Interakcija između melatonina i sezone nije pokazala značajniji učinak, ali tijekom zimske sezone proizvodnja mlijeka u kontrolnih krava bila je veća (P=0,06) u odnosu na krave tretirane melatoninom (45,3±3,7 u kontrolnoj skupini, odnosno 49,2±3,0 u krava tretiranih melatoninom). Ova studija ukazuje da tretman melatoninom prije teljenja ne mijenja proizvodnju mlijeka tijekom kasnije laktacije. Primijećena je samo tendencija smanjenja proizvodnje mlijeka u zimskoj sezoni u krava tretiranih melatoninom

COMPARISON OF THE EFFECTS OF KISSPEPTIN-10 OR GNRH ON LUTEINIZING HORMONE SECRETION DURING THE LUTEAL PHASE OF THE OESTROUS CYCLE IN SWAMP BUFFALO COWS

This study compared the effect of kisspeptin-10 or GnRH administration on LH release in swamp buffalo during the luteal phase of the estrous cycle. Six animals were treated with a single intravenous injection of 1,000 pmol/kg b.w. of kisspeptin-10 or a single intramuscular injection of 10 mu g/cow of GnRH agonist buserelin. For plasma LH analysis blood samples were collected every 15 minutes, 1 h before and 6 h after kisspeptin-10 and GnRH administration. An increase in LH plasma concentrations was observed after GnRH administration but not after kisspeptin-10 administration. The results of this study indicate that during the luteal phase of the estrous cycle, administration of GnRH, but not kisspeptin-10, stimulate LH secretion

The GnRH analogue dephereline given in a fixed-time AI protocol improves ovulation and embryo survival in dairy cows

This study compares the fertility effects of inducing ovulation using the GnRH analogue, dephereline, versus natural GnRH at the end of a 5-day progesterone(P4)-based protocol for fixed-time artificial insemination (FTAI) in in heat-stressed and non-heat stressed lactating dairy cows. Cows were given GnRH (GnRH group, n = 369) or dephereline (DEPH group, n = 379) and were inseminated 14-20 h later. Dephereline treatment increased corpus luteum (CL) size on Day 7 post-AI compared with GnRH (P < .0001) while a one-mm increase in CL size was found to give rise to a 1.1-fold increase in the pregnancy rate at FTAI (P = .001). Based on odds ratios, the interaction between treatment and heat stress had a significant effect on the ovulation failure rate (P < .01). This meant that relative to non-heat-stressed GnRH-treated cows, ovulation failure was 2.9 times more likely in heat-stressed GnRH-treated cows (P = .001), 0.3 times less likely in non-heat-stressed DEPH-treated cows (P = .04) and was similar in heat-stressed DEPH-treated cows. Further, non-heat-stressed DEPH-treated cows were more likely to conceive by a factor of 1.6 than the remaining cows (P = .03). Finally, GnRH-treated multiparous cows were 9.9 times more likely to suffer pregnancy loss than the remaining cows (P = .03). Our results indicate that, compared to treatment with GnRH, dephereline reduced the risk of ovulation failure and consequently increased the pregnancy rate under heat stress conditions. In multiparous cows, dephereline treatment also reduced the negative age effect on pregnancy maintenance

Postpartum prostaglandin F2alpha administration affects colostrum yield, IgG and piglet performance

Objective: Current study was conducted to determine the effect of postpartum prostaglandin F2α (PGF2α) administration on colostrum and milk yield, colostrum immunoglobulin G (IgG) and piglet growth performance. Methods: In total, 36 sows were included in the experiment. The sows were classified into two groups: i) control (n = 11) and ii) PGF2α (n = 25). Sows in the PGF2α group received 10 mg of PGF2α within an hour after farrowing. The body weight of piglets was measured at 0 and 24 h after birth to estimate colostrum consumption. Colostrum was collected at 1 and 24 h after farrowing to determine IgG concentrations. For milk yield study, the remaining sows in the PGF2α group (n = 23) were divided into two subgroups: i) single PGF2α (n = 12) and ii) multiple PGF2α (n = 11). In the multiple PGF2α, the sows received repeated doses of PGF2α at seven and 14 days postpartum. The piglets’ body weight was measured at 0, 1, 5, and 20 days of age. The milk yield of the sows was calculated. Results: Colostrum yield of sows averaged 5.62±2.25 kg. Sows treated with PGF2α postpartum had a higher colostrum yield than control (7.01 and 5.12 kg, p&lt;0.05). The concentration of IgG in colostrum at 24 h in the PGF2α group was higher than the control (31.6 and 17.4 g/L, p&lt;0.05). For primiparous sows, milk yield was highest in the sows treated with multiple doses of PGF2α during lactation and lowest in control sows (10.25 and 7.61 kg, p&lt;0.05). Colostrum intake was higher in the treatment than the control groups (+56.7 g, p&lt;0.05). Primiparous sows treated with multiple doses of PGF2α had a higher litter weight than controls (p&lt;0.01). Conclusion: Postpartum treatment with PGF2α improved colostrum yield and IgG in multiparous sows and increased colostrum intake of piglets. Multiple administration of PGF2α improved the milk yield and increased litter weight of piglets in primiparous sow