Treatment with eCG and hCG to induce onset of estrous cycles in ewes during the non-breeding season: Effects on follicular development and fertility.

Although combining of eCG and hCG administrations is known to enhance LH-like actions, there have been few studies where there was comparison of the effects of treatment of anestrous ewes with eCG and hCG and eCG alone. In Experiment 1, 18 ewes in seasonal anestrus were administered an intravaginal device (IVD) containing medroxyprogesterone acetate for 12 days, and at the time of IVD removal (D0), were allocated into the following groups (n = 6/group): no further treatment (control); 400 IU eCG (eCG); or 400 IU eCG and 200 IU hCG (eCG + hCG). There was greater ovarian follicular growth in the groups treated with gonadotropins, compared to the control, and there were greater progesterone concentrations in the eCG + hCG group on D9 (P < 0.05). In Experiment 2, 66 ewe lambs were assigned to the same treatment groups described for Experiment 1, and subsequently there was natural mating with rams. There was a greater rate of behavioral estrous manifestation in the eCG (88.5 %; 23/26) and eCG+hCG (85.2 %; 23/27), than control (30.8 %; 4/13; P < 0.05) group. Pregnancy rate was also greater in the eCG (34.6 %; 9/26) and eCG+hCG (18.6 %; 5/27) than control (0 %; 0/13; P < 0.05) group, whereas conception rate, considering only ewe lambs that were mated, was only greater in the eCG group. Although there were greater progesterone concentrations 9 days after treatment in the eCG+hCG group, there was no difference in follicular growth in anestrous ewes, nor was there an effect on estrous behavior manifestation and pregnancy rates in ewe lambs, compared to treatment with only eCG.

Expression of paraoxonase types 1, 2 and 3 in reproductive tissues and activity of paraoxonase type 1 in the serum and seminal plasma of bulls.

The paraoxonases types 1, 2 and 3 (PON1, PON2 and PON3, respectively) are enzymes that degrade lipid peroxides, preventing oxidative damages relevant for male reproductive function. This study determined the expression of those three paraoxonases in reproductive tissues of bulls and evaluated correlations among the activity of PON1 in the serum and seminal plasma with breeding soundness parameters in bulls. The expression of PON1, PON2 and PON3 was characterised by RT-PCR in samples of testicular parenchyma, vesicular glands and epididymis collected from three slaughtered bulls. All three paraoxonases were expressed in the testicular parenchyma, PON2 and PON3 were both expressed in the epididymis head and PON3 was also expressed in the epididymis tail. The PON1 activity was determined in samples of serum and seminal plasma from 110 bulls submitted to breeding soundness evaluation. There was a strong correlation (r = .90) between the activity of the PON1 in both serum and seminal plasma (p < .0001). The PON1 activity in the seminal plasma was positively correlated with ejaculate's colour, sperm mass activity (p = .04), motility, vigour and viability (all p < .01). Thus, PON1 may be a potential marker for sperm motility and viability in bulls.

Expression of growth and differentiation Factor 9 and cognate receptors during final follicular growth in cattle

Mutations in growth and differentiation factor9 (GDF9) gene are associated to sterility or,paradoxically, increased ovulation rate in ewes. Despiteits importance, the exact function of GDF9 in ovarianphysiology is still poorly understood. This study aimedto investigate GDF9 function during dominant folliclegrowth and its regulation in follicular fluid. Theregulation of GDF9 receptors in GnRH/LH-stimulatedgranulosa cells was also investigated. In a firstexperiment, a new follicular wave was induced and theintrafollicular GDF9 treatment into the largest growingfollicle (8.5-9.5 mm) at both 100 (n = 3) and 1000ng/ml(n = 4) had no effect on follicular growth, estrusmanifestation and ovulation compared to control (PBSinjected)follicles (n = 3). In a second experiment,follicles were obtained just after follicular deviation(day 4 after follicular emergence) and the abundance ofGDF9 in follicular fluid did not differ between healthydominant (n = 4) and atretic subordinate follicles (n =4), as assessed by western blot analysis. Finally, mRNAexpression of BMPR2 and TGFBR1 receptors wasevaluated in granulosa cells obtained from preovulatoryfollicles (>12 mm diameter) obtained 0, 3, 6, 12 or 24 hafter i.m. GnRH administration (n = 4-5follicles/moment). Both receptors were significantly upregulated 12 h after GnRH treatment. Present results donot confirm the hypothesis that GDF9 inhibits dominantfollicle growth and suggests a minor role in determiningfollicle fate. In the other hand, GDF9 receptorsregulation in GnRH/LH-stimulated granulosa cellsprovides the first in vivo evidence of its involvement inthe complex cascade of events that culminates inovulation and luteinization in cattle.(AU)

Expression of growth and differentiation Factor 9 and cognate receptors during final follicular growth in cattle

Mutations in growth and differentiation factor9 (GDF9) gene are associated to sterility or,paradoxically, increased ovulation rate in ewes. Despiteits importance, the exact function of GDF9 in ovarianphysiology is still poorly understood. This study aimedto investigate GDF9 function during dominant folliclegrowth and its regulation in follicular fluid. Theregulation of GDF9 receptors in GnRH/LH-stimulatedgranulosa cells was also investigated. In a firstexperiment, a new follicular wave was induced and theintrafollicular GDF9 treatment into the largest growingfollicle (8.5-9.5 mm) at both 100 (n = 3) and 1000ng/ml(n = 4) had no effect on follicular growth, estrusmanifestation and ovulation compared to control (PBSinjected)follicles (n = 3). In a second experiment,follicles were obtained just after follicular deviation(day 4 after follicular emergence) and the abundance ofGDF9 in follicular fluid did not differ between healthydominant (n = 4) and atretic subordinate follicles (n =4), as assessed by western blot analysis. Finally, mRNAexpression of BMPR2 and TGFBR1 receptors wasevaluated in granulosa cells obtained from preovulatoryfollicles (>12 mm diameter) obtained 0, 3, 6, 12 or 24 hafter i.m. GnRH administration (n = 4-5follicles/moment). Both receptors were significantly upregulated 12 h after GnRH treatment. Present results donot confirm the hypothesis that GDF9 inhibits dominantfollicle growth and suggests a minor role in determiningfollicle fate. In the other hand, GDF9 receptorsregulation in GnRH/LH-stimulated granulosa cellsprovides the first in vivo evidence of its involvement inthe complex cascade of events that culminates inovulation and luteinization in cattle.

Indução artificial de lactação em bovinos: histórico e evolução / Artificial induction of lactation in cattle: history and evolution

O descarte precoce de vacas leiteiras por problemas reprodutivos, por falhas no manejo e por outrosfatores que levem as vacas a encerrarem uma lactação sem estarem prenhes aumenta os custos e diminui arentabilidade da produção de leite. Como alternativa, pode-se utilizar a indução artificial de lactação, prática demanejo que mimetiza o perfil endócrino da vaca no periparto com o objetivo de induzir a síntese láctea pelaglândula mamária. Os protocolos de indução em bovinos são estudados desde a década de 40, e os primeirosestudos envolviam aplicações hormonais por até nove meses. Nos anos 70, houve uma evolução significativa,quando foi estabelecido que sete dias de aplicação de hormônios esteroides eram suficientes para induzir asvacas a lactarem. Protocolos utilizando progesterona e estradiol como base foram testados ao longo dos anos e,atualmente, os protocolos comerciais têm a duração de aproximadamente 21 dias e utilizam aplicações degrandes volumes de hormônios em manejos diários. Embora os protocolos possibilitem boa taxa de resposta e deprodução de leite, até o presente momento não foram avaliados os impactos nos animais. O objetivo destarevisão é demonstrar a evolução dos protocolos, suas aplicações, desvantagens, possíveis soluções eperspectivas.(AU)

The early culling of dairy cows due to reproductive failure, management problems and other factorsthat lead the dairy cows to be dried-off without being pregnant, increase costs and decrease profitability of milkproduction. A possible alternative is the use of artificial lactation induction, a tool that mimics peripartumendocrine profiles with the aim of inducing milk synthesis from the mammary gland. Protocols of induction oflactation in cattle have been studied since the 1940s, and the first studies consisted of hormonal applications fornine months. In the 1970s, there was a significant evolution, when it was established that seven days of steroidhormones application were sufficient to induce lactation. Since then, several protocols using progesterone andestradiol have been tested. Currently, commercial protocols lasts for 21 days and use large volumes ofhormones, requiring daily handling of animals. Although current protocols are efficient, enabling good responserate and milk production, so far the degree of discomfort to which animals are exposed is unknown. The purposeof this review is to provide background information on the evolution of protocols, their applications, drawbacks,possible solutions and prospects.(AU)

Indução artificial de lactação em bovinos: histórico e evolução / Artificial induction of lactation in cattle: history and evolution

O descarte precoce de vacas leiteiras por problemas reprodutivos, por falhas no manejo e por outrosfatores que levem as vacas a encerrarem uma lactação sem estarem prenhes aumenta os custos e diminui arentabilidade da produção de leite. Como alternativa, pode-se utilizar a indução artificial de lactação, prática demanejo que mimetiza o perfil endócrino da vaca no periparto com o objetivo de induzir a síntese láctea pelaglândula mamária. Os protocolos de indução em bovinos são estudados desde a década de 40, e os primeirosestudos envolviam aplicações hormonais por até nove meses. Nos anos 70, houve uma evolução significativa,quando foi estabelecido que sete dias de aplicação de hormônios esteroides eram suficientes para induzir asvacas a lactarem. Protocolos utilizando progesterona e estradiol como base foram testados ao longo dos anos e,atualmente, os protocolos comerciais têm a duração de aproximadamente 21 dias e utilizam aplicações degrandes volumes de hormônios em manejos diários. Embora os protocolos possibilitem boa taxa de resposta e deprodução de leite, até o presente momento não foram avaliados os impactos nos animais. O objetivo destarevisão é demonstrar a evolução dos protocolos, suas aplicações, desvantagens, possíveis soluções eperspectivas.

The early culling of dairy cows due to reproductive failure, management problems and other factorsthat lead the dairy cows to be dried-off without being pregnant, increase costs and decrease profitability of milkproduction. A possible alternative is the use of artificial lactation induction, a tool that mimics peripartumendocrine profiles with the aim of inducing milk synthesis from the mammary gland. Protocols of induction oflactation in cattle have been studied since the 1940s, and the first studies consisted of hormonal applications fornine months. In the 1970s, there was a significant evolution, when it was established that seven days of steroidhormones application were sufficient to induce lactation. Since then, several protocols using progesterone andestradiol have been tested. Currently, commercial protocols lasts for 21 days and use large volumes ofhormones, requiring daily handling of animals. Although current protocols are efficient, enabling good responserate and milk production, so far the degree of discomfort to which animals are exposed is unknown. The purposeof this review is to provide background information on the evolution of protocols, their applications, drawbacks,possible solutions and prospects.