Heat shock on bovine embryos from day 2.5-3 selects the most competent for progression to the blastocyst stage.

Heat shock can impair embryo formation, while growth factors, such as colony-stimulating factor 2 (CSF2), modulate embryonic development. This study evaluated the effect of heat shock between days 2.5 and 3, as well as the impact of CSF2 at day 5 on bovine embryos cultured in a serum-free in vitro medium. The focus was on blastocyst development, the number of blastomeres, DNA fragmentation (TUNEL-positive cells), and mitochondrial activity. Heat shock reduced the proportion of cleaved embryos that developed into blastocysts (P = 0.0603). The resultant blastocysts exhibited a reduced number and proportion of TUNEL-positive cells in the trophectoderm (P = 0.0270 and P = 0.0240, respectively) and in the entire embryo (P = 0.0029 and P = 0.0031, respectively). Additionally, mitochondrial activity was lower in blastocysts derived from heat-shocked embryos (P = 0.0150) and further reduced in embryos exposed to both heat shock and CSF2 (P = 0.0415). In conclusion, the exposure of cleaved embryos to heat shock reduced their development to the blastocyst stage. However, the resulting blastocysts showed decreased DNA fragmentation and mitochondrial activity.

Sperm head morphometry and chromatin alterations in bulls with different conception rates.

The objective of this investigation was to analyze timed-AI conception rates (CRs) of different sires in light of their conventional semen quality parameters, sperm head morphometry, and chromatin alterations. Semen was collected in the field from six Angus bulls and used for the timed-AI of 890 suckled multiparous Nellore cows at a single farm. Semen batches were evaluated on the following in vitro parameters: sperm motility, concentration, and morphology, sperm head morphometry, and chromatin alteration types. The overall CR was 49% and Bulls 1 (43%) and 2 (40%) presented reduced (P < 0.05) pregnancies per AI compared to Bull 6 (61%), even though no differences were observed between their conventional semen quality parameters. Bull 1, however, presented higher (P = 0.0001) shape factor, smaller (P = 0.0025) antero-posterior symmetry, and elevated (P = 0.0141) Fourier 1 parameter, whereas Bull 2 exhibited a higher (P = 0.0023) percentage of chromatin alteration along the central axis of the sperm head. In conclusion, bulls with varying CRs may present sperm head morphometric differences and/or chromatin alterations while not presenting differences in conventional in vitro semen quality parameters. Although further studies are needed to elucidate the concrete implications of chromatin alterations on field fertility, sperm morphometric differences and chromatin alterations may be at least partially causative of the lower pregnancies per timed-AI of certain sires.

Squamous metaplasia of the rete ovarii in a Zebu cow.

BACKGROUND: Stratified keratinizing squamous epithelium in the ovary has been associated with the diagnosis of ovarian teratoma in cows. Recently, the diagnosis of "epidermoid cyst" has been proposed. A case of squamous metaplasia of the rete ovarii in a Zebu cow is described in this report. CASE PRESENTATION: A crossbreed Zebu cow had both ovaries enlarged with multiple cysts. Most cysts were lined by well differentiated keratinizing stratified squamous epithelium and filled with keratinized lamellar material. Some cysts were lined by an epithelial layer that ranged from single cuboidal, double cuboidal epithelium, stratified non keratinized epithelium, and areas of keratinizing stratified squamous epithelium. Single or double layered cuboidal epithelia of the cysts expressed low molecular weight cytokeratin 7, whose expression was absent in the keratinizing stratified squamous epithelia of same cysts. Conversely, high molecular weight cytokeratins 1, 5, 10, and 14 were strongly expressed by the keratinizing stratified epithelium. CONCLUSION: Squamous metaplasia of the rete ovarii was diagnosed. Squamous metaplasia of the rete ovarii, may account for some of the previously described squamous lesions in the ovary, which may have been misinterpreted as teratoma or epidermoid cysts.

Erratum to: Daily vaginal temperature in Girolando cows from three different genetic composition under natural heat stress.

[This corrects the article DOI: 10.1093/tas/txab138.].

Daily vaginal temperature in Girolando cows from three different genetic composition under natural heat stress.

The present trial evaluated the effect of crossbred composition and Temperature and Humidity Index (THI) on vaginal temperature (VT) of Girolando dairy cows maintained under tropical pasture during warm seasons. The VT was monitored along 41 to 96 h in 615 Girolando cows with different Holstein (H) × Gir genetic composition (1/2 H = 284, 3/4 H = 248, and 7/8 H = 83) from six Brazilian farms in the summer of 2016 and 2017. VT of each cow at each hour of the day and the respective THI were averaged per hour across all monitoring days to generate an averaged value for VT and THI during 24 h. A linear mixed model with repeated measures using restricted maximum likelihood (REML) method for (co)variance components estimation procedure was employed. The final model adjusted the VT for the effects of cow, time, THI, farm, year, pregnancy status, body condition score (BCS), milk yield, genetic composition, and genetic composition*time interaction. Fixed effects were evaluated by ANOVA and tested with Tukey test in R software version 3.6.1 (R Core Team, 2019). Overall mean of VT, air temperature (AT), and THI were 39.06 ± 0.52 °C, 25.63 ± 0.40 °C, and 75.06 ± 3.96, respectively. VT had moderate positive correlation with THI (r² = 0.45, P < 0.001) and AT (r² = 0.46, P < 0.001). The VT had estimated linear increase of 0.05 °C for each THI unit increase (P < 0.001). Least square mean of VT varied among the farms (P < 0.001), pregnancy status (P < 0.001), and BCS (P < 0.05) but not for Milk yield (P > 0.05). The daily average VT was affected by genetic composition (P < 0.001) with highest temperature for 3/4 H (39.08 ± 0.06 °C a) and 7/8 H (39.09 ± 0.06 °C a) and lowest temperature for 1/2 H (38.95 ± 0.06 °C b). The difference of VT among the three crossbred groups varied in function of the time of the day, from 12:00 to 20:00 h (P < 0.001), with 3/4 Holstein and 7/8 Holstein cows reaching similar VT, above to the upper limit 39.1 °C and higher than 1/2 Holstein cows during all this period. In conclusion, Girolando cows are sensitive to heat stress in tropical condition during warm seasons. Moreover, Girolando cows with genetic composition higher than 3/4 Holstein display reduced thermoregulatory efficiency. Therefore, Girolando cows in tropical dairy farms require strategies to mitigate heat stress according to their genetic composition.

Production of IL-1ß, IL-6 and CXCL8 by endometrium of crossbred heifers stimulated with various pathogen-associated molecular patterns.

Uterine bacterial infections are common during the post-partum period of dairy herds and, apparently, incidences in crossbred cattle are less than in Holsteins. The aims of this study were (I) to evaluate production of interleukin 1-ß (IL-1ß), interleukin-6 (IL-6) and chemokine CXCL8 using endometrial explants from Bos indicus crossbred heifers at diestrous, stimulated by various pathogen-associated molecular patterns (PAMP), and (II) assess production of these cytokines by lipopolysaccharide-stimulated endometrial explants from heifers when samples were collected at different stages of estrous cycle. In the first experiment, endometrial explants from heifers at diestrous were stimulated by ten-fold serial dilutions of lipopolysaccharide (LPS), triacylated lipopeptide (PAM3) or peptidoglycan (PGN). In the second experiment, endometrial explants collected at different stages of the estrous cycle were treated with LPS. Concentrations of IL-1ß, IL-6 and CXCL8 were quantified in supernatant. There was a marked (P < 0.05) production of IL-1ß, IL-6, and CXCL8 in response to LPS treatment. There was also production of IL-1ß (P < 0.05) in response to PGN treatment. Explant samples collected at different stages of the estrous cycle responded to LPS treatment with production of IL-1ß and IL-6, but with no differences (P > 0.05) between stages of estrous cycle. In conclusion, endometrial samples of crossbred Zebu-based heifers collected during diestrous produced IL-1ß, IL-6 and CXCL8 in response to LPS and IL-1ß in response to PGN. The cytokine production in response to LPS, however, was not affected by the stage of the estrous cycle in Bos indicus crossbred heifers.

Energy metabolism of pregnant zebu and crossbred zebu dairy cattle.

The purpose of this study was to determine the energy partition of pregnant F1 Holstein x Gyr with average initial body weight (BW) of 515.6 kg and Gyr cows with average initial BW of 435.1 kg at 180, 210 and 240 days of gestation, obtained using respirometry. Twelve animals in two groups (six per genetic group) received a restricted diet equivalent to 1.3 times the net energy for maintenance (NEm). The proportion of gross energy intake (GEI) lost as feces did not differ between the evaluated breeds and corresponded to 28.65% on average. The daily methane production (L/d) was greater for (P<0.05) F1 HxG compared to Gyr animals. However, when expressed as L/kg dry matter (DM) or as percentage of GEI there were no differences between the groups (P>0.05). The daily loss of energy as urine (mean of 1.42 Mcal/d) did not differ (P>0.05) between groups and ranged from 3.87 to 5.35% of the GEI. The metabolizable energy intake (MEI) of F1 HxG animals was greater (P < 0.05) at all gestational stages compared to Gyr cows when expressed in Mcal/d. However, when expressed in kcal/kg of metabolic BW (BW0,75), the F1 HxG cows had MEI 11% greater (P<0.05) at 240 days of gestation and averaged 194.39 kcal/kg of BW0,75. Gyr cows showed no change in MEI over time (P>0.05), with a mean of 146.66 kcal/kg BW0. 75. The ME used by the conceptus was calculated by deducting the metabolizable energy for maintenance (MEm) from the MEI, which was obtained in a previous study using the same cows prior to becoming pregnant. The values of NEm obtained in the previous study with similar non-pregnant cows were 92.02 kcal/kg BW0.75 for F1 HxG, and 76.83 kcal/kg BW0.75 for Gyr (P = 0.06). The average ME for pregnancy (MEp) was 5.33 Mcal/d for F1 HxG and 4.46 Mcal/d for Gyr. The metabolizability ratio, averaging 0.60, was similar among the evaluated groups (P>0.05). The ME / Digestible Energy (DE) ratio differed between groups and periods evaluated (P<0.05) with a mean of 0.84. The heat increment (HI) accounted for 22.74% and 24.38% of the GEI for F1 HxG and Gyr cows, respectively. The proportion of GEI used in the basal metabolism by pregnant cows in this study represented 29.69%. However, there were no differences between the breeds and the evaluation periods and corresponded to 29.69%. The mean NE for pregnancy (NEp) was 2.76 Mcal/d and did not differ between groups and gestational stages (P>0.05).

In vitro toxicity of Niedenzuella (Tetrapterys) multiglandulosa on bovine embryos / Toxicidade in vitro da Niedenzuella (Tetrapterys) multiglandulosa em embriões bovinos

Niedenzuella (Tetrapterys) multiglandulosa, a vine plant found in Brazil, has been correlated to outbreaks of poisoning in cattle and buffaloes, generating economic losses related to the death due to heart failure, miscarriage, abortion, stillbirth, and neonatal mortality. The aim of this study was to examine the embryotoxic potential of the aqueous plant extract on in vitro bovine embryos. In vitro study was performed in five replicates of bovine embryo culture assigned in two groups: control, in vitro embryo culture medium without the aqueous plant extract; treated group, with addition of 2.7mg/mL of aqueous plant extract (10%) to the embryo culture on the sixth day of culture. Cleavage rate was evaluated at day 2 of the cell culture. Viability, hatchability and underdevelopment of blastocysts on the seventh, eighth, and ninth days (D7, D8, and D9, respectively) of culture were assessed under stereoscopic microscope. On day 7, blastocysts were submitted to TUNEL assay to determine apoptotic index. In vitro exposure of bovine embryos to of N. multiglandulosa resulted in reduced embryo development and survival, evaluated by dark cytoplasm indicating poor morphology and poor quality with marked reduction of hatchability. We observed a significant reduction of blastocyst production/number of cleaved embryos (60.6% vs 41.5%); reduction of blastocysts production/total number of matured bovine oocytes (35.1% vs 21.3%); and embryonic hatching rates (38.0% vs 10.0%). However, no effects were observed on the apoptotic rate. In conclusion, aqueous extract of N. multiglandulosa leaves reduces bovine embryo viability in vitro, suggesting possible detrimental effects on embryo development.(AU)

Niedenzuella (Tetrapterys) multiglandulosa, uma videira encontrada no Brasil, tem sido correlacionada a surtos de intoxicações em bovinos e búfalos, gerando perdas econômicas relacionadas à morte por insuficiência cardíaca, aborto, natimorto e mortalidade neonatal. O objetivo deste estudo foi examinar o potencial embriotóxico do extrato vegetal aquoso em embriões bovinos in vitro. O estudo in vitro foi realizado em cinco repetições de cultura de embriões bovinos distribuídos em dois grupos: controle, meio de cultura de embriões in vitro sem o extrato aquoso da planta; grupo tratado, com adição de 2,7mg / mL de extrato vegetal aquoso (10%) à cultura do embrião no sexto dia de cultivo. A taxa de clivagem foi avaliada no dia 2 da cultura de células. Viabilidade, eclodibilidade e subdesenvolvimento de blastocistos no sétimo, oitavo e nono dia (D7, D8 e D9, respectivamente) de cultura foram avaliados em microscópio estereoscópico. No dia 7, os blastocistos foram submetidos ao ensaio TUNEL para determinar o índice apoptótico. Observamos redução significativa da produção de blastocisto / número de embriões clivados (60,6% vs 41,5%); redução da produção de blastocistos / número total de oócitos bovinos maturados (35,1% vs 21,3%); e taxas de eclosão embrionária (38,0% vs 10,0%). No entanto, nenhum efeito foi observado na taxa de apoptose. Em conclusão, o extrato aquoso das folhas de N. multiglandulosa reduz a viabilidade do embrião bovino in vitro, sugerindo possíveis efeitos prejudiciais no desenvolvimento embrionário.(AU)

Osteolytic osteomyelitis associated with visceral leishmaniasis in a dog.

A dog was examined with a history of weight loss and lameness of the left hind limb. A painful response to examination of the left hip joint, and lymphadenopathy were noted. Amastigote forms of Leishmania sp. were observed by cytology in samples from the popliteus lymph node, and anti-Leishmania sp. antibodies at a titer of 1:640 were detected in serum by indirect immunofluorescence. Radiological changes included osteolysis and a periosteal proliferative reaction in the left femoral greater trochanter. These changes were histologically characterized as an osteolytic granulomatous osteomyelitis associated with amastigotes within macrophages. Non-decalcified fragments of the periosteum were processed for immunohistochemistry, observed with prominent immunolabelling of amastigotes of Leishmania sp. within macrophages. The diagnosis was further confirmed by positive PCR for Leishmania sp., belonging to the Leishmania donovani complex.

Explants of intact endometrium to model bovine innate immunity and inflammation ex vivo.

PROBLEM: Bacterial infections commonly cause bovine endometritis and infertility via innate immune pathways. However, mechanistic studies using isolated cells or chopped tissue may be compromised by the disruption of endometrial architecture and release of damage-associated molecular patterns. So, this study aimed to establish an ex vivo model of intact bovine endometrium to study innate immunity and inflammation. METHOD OF STUDY: Intact bovine endometrium explants were collected using a sterile 8-mm punch biopsy and cultured ex vivo with bacteria or pathogen-associated molecules. Interleukin accumulation was measured, and tissue viability was assessed by microscopy, TdT-mediated biotin-dUTP nick-end labelling and lactate dehydrogenase assay. RESULTS: Intact endometrium explants accumulated IL-6, IL-1ß and IL-8 in response to Gram-negative or Gram-positive bacteria, and their purified pathogen-associated molecules; inflammatory responses were dependent on the stage of oestrous cycle. Explants of intact endometrium maintained viability and tissue architecture, and had lower basal accumulation of interleukins compared with explants using chopped endometrium. CONCLUSION: This study established a tractable ex vivo model of intact endometrium to explore the mechanisms of immunity and inflammation in the bovine endometrium.

Transcription of pattern recognition receptors and abortive agents induced chemokines in the bovine pregnant uterus.

Pattern recognition receptors (PRRs) are important components of the innate immune system whose ligands are specific pathogen associated molecular patterns (PAMPs). Considering the scarcity of studies on transcription of PRRs in the pregnant uterus of cows, and its response to PAMPs and microorganisms that cause abortion in cattle, this study aimed to characterize the transcription of TLR1-10, NOD1, NOD2 and MD2 in bovine uterus throughout gestation and to investigate the sensitivity of different uterine tissues at third trimester of pregnancy to purified TLR ligands or heat-killed Brucella abortus, Salmonella enterica serotype Dublin (S. Dublin), Listeria monocytogenes, and Aspergillus fumigatus, by assessing chemokine transcription. RNA extracted from endometrium, placentome and intercotiledonary region of cows at the first (n=6), second (n=6), and third (n=6) trimesters of pregnancy were subjected to real time RT-PCR. After stimulation of endometrium and intercotiledonary regions with purified TLR ligands or heat-killed microorganisms, gene transcription was assessed by real time RT-PCR. In the placentome, there was no significant variation in TLRs transcription throughout the three trimesters of pregnancy. In the endometrium, there was significant variation in TLR4 and TLR5 transcription during the three stages of gestation; i.e. TLR4 transcription was higher during the third trimester, whereas TLR5 transcription was higher during the last two trimesters. In the intercotiledonary region, there was significant variation in transcription of TLR1/6, TLR7, and TLR8, which were more strongly expressed during the first trimester of pregnancy. At the third trimester of gestation, significant transcription of CXCL6 and CXCL8 was detected mostly in endometrial tissues in response to purified TLR4 and TLR2 ligands. Transcription of these chemokines was induced in the endometrium and intercotiledonary region at the third trimester of pregnancy when stimulated with heat-killed B. abortus or S. Dublin. Therefore, this study demonstrates that some PRRs are expressed in the uterus during pregnancy, which coincides with its ability to respond to stimulation with TLRs ligands as well as heat-killed organisms known to cause abortion in cattle.

Maturação in vitro de oócitos bubalinos e seu efeito sobre o desenvolvimento embrionário / In vitro maturation of buffaloes oocytes and its effect on embryonic development

As biotécnicas da reprodução representam uma alternativa promissora para incremento genético emcurto espaço de tempo nos animais domésticos e, em bubalinos, ganham maior notoriedade devido a ocorrênciade entraves reprodutivos, como manifestação discreta do estro e longo anestro pós-parto. Assim, a produção deembriões in vitro (PIVE) em bubalinos vem gradativamente ganhando mercado, apesar dos resultadosinconsistentes e inferiores quando comparado aos bovinos. Diante disso, o entendimento das etapas da PIVE,que inclui a maturação in vitro dos oócitos (MIV), a fertilização in vitro (FIV) e o cultivo in vitro (CIV) se faznecessário para melhor compreensão das mudanças e necessidades durante o crescimento e desenvolvimento dooócito e do embrião. Especificamente durante a MIV ocorrem inúmeras mudanças nos oócitos que irão interferirna sua capacidade de se tornar um embrião e a seleção dos oócitos mais viáveis e competentes pode incrementarsignificativamente as taxas de PIVE em bubalinos. Assim, métodos de avaliação precisos e confiáveis e oconhecimento profundo da cinética de desenvolvimento dos oócitos e embriões bubalinos são necessários para oestabelecimento de protocolos e meios específicos para estes, uma vez que, que na maioria das vezes osutilizados são extrapolados da espécie bovina.

The reproduction biotechnologies represent a promising alternative for genetic increase in short time indomestic animals. On buffaloes the gain are greater due to the occurrence of reproductive barriers such asdiscrete manifestation of estrus and long anoestrus postpartum. Thus, in vitro embryo production (IVEP) inbuffaloes is gradually gaining market share despite inconsistent and inferior results when compared to cattle.Thus, the understanding of the stages of IVEP, which includes the in vitro maturation of oocytes (IVM), in vitrofertilization (IVF) and in vitro culture (IVC) is needed to better understand the changes and needs during growthand development of the oocyte and embryo. Specifically during IVM occur numerous changes in oocytes that willinterfere with your ability to turn an embryo and the selection of the most viable and reliable oocytes cansignificantly increase PIVE rates in buffalo. Thus, accurate assessment and safe methods and a deep knowledgeof the buffalo oocytes and embryos development kinetics are needed to establish protocols and specific means tothem, since most that are used are extrapolated bovine species.

Maturação in vitro de oócitos bubalinos e seu efeito sobre o desenvolvimento embrionário / In vitro maturation of buffaloes oocytes and its effect on embryonic development

As biotécnicas da reprodução representam uma alternativa promissora para incremento genético emcurto espaço de tempo nos animais domésticos e, em bubalinos, ganham maior notoriedade devido a ocorrênciade entraves reprodutivos, como manifestação discreta do estro e longo anestro pós-parto. Assim, a produção deembriões in vitro (PIVE) em bubalinos vem gradativamente ganhando mercado, apesar dos resultadosinconsistentes e inferiores quando comparado aos bovinos. Diante disso, o entendimento das etapas da PIVE,que inclui a maturação in vitro dos oócitos (MIV), a fertilização in vitro (FIV) e o cultivo in vitro (CIV) se faznecessário para melhor compreensão das mudanças e necessidades durante o crescimento e desenvolvimento dooócito e do embrião. Especificamente durante a MIV ocorrem inúmeras mudanças nos oócitos que irão interferirna sua capacidade de se tornar um embrião e a seleção dos oócitos mais viáveis e competentes pode incrementarsignificativamente as taxas de PIVE em bubalinos. Assim, métodos de avaliação precisos e confiáveis e oconhecimento profundo da cinética de desenvolvimento dos oócitos e embriões bubalinos são necessários para oestabelecimento de protocolos e meios específicos para estes, uma vez que, que na maioria das vezes osutilizados são extrapolados da espécie bovina.(AU)

The reproduction biotechnologies represent a promising alternative for genetic increase in short time indomestic animals. On buffaloes the gain are greater due to the occurrence of reproductive barriers such asdiscrete manifestation of estrus and long anoestrus postpartum. Thus, in vitro embryo production (IVEP) inbuffaloes is gradually gaining market share despite inconsistent and inferior results when compared to cattle.Thus, the understanding of the stages of IVEP, which includes the in vitro maturation of oocytes (IVM), in vitrofertilization (IVF) and in vitro culture (IVC) is needed to better understand the changes and needs during growthand development of the oocyte and embryo. Specifically during IVM occur numerous changes in oocytes that willinterfere with your ability to turn an embryo and the selection of the most viable and reliable oocytes cansignificantly increase PIVE rates in buffalo. Thus, accurate assessment and safe methods and a deep knowledgeof the buffalo oocytes and embryos development kinetics are needed to establish protocols and specific means tothem, since most that are used are extrapolated bovine species.(AU)

Postpartum toll-like receptors and ß-defensin 5 mRNA levels in the endometrium of Holstein cows.

Toll-like receptors (TLRs) and ß-defensins are important components of the innate immune system. This study aimed to evaluate endometrial mRNA levels of TLRs (1/6, 2, 4, and 5) and ß-defensin 5 in Holstein cows by quantitative real time RT-PCR. Uterine biopsies were performed from 6 to 12 h after parturition, and cows were divided into two groups: (i) cows with placental retention and clinical signs of uterine infection until 45 days postpartum (n=10) or (ii) cows with normal puerperium (n=10). All cows had detectable levels of TLRs and ß-defensin 5 mRNAs, but these levels did not differ between groups (P>0.05). Levels of TLR4 mRNA had a positive and significant correlation with the time required for uterine involution in both groups.

Reprodução de vacas mestiças: potencialidade e desafios / Reproduction of crossbreeding dairy cows: potentiality and challenges

O desafio dos produtores de leite do Brasil consiste em buscar o equilíbrio entre produção de leite e sustentabilidade dos sistemas de produção. Aproximadamente 70% do rebanho leiteiro do Brasil é composto por vacas mestiças Holandês x Zebu, mantidas em sistema de manejo semi-intensivo. Pesquisas básicas e aplicadas que visam compreender as particularidades da produção e reprodução de fêmeas mestiças leiteiras são extremamente importantes para auxiliar na melhoria do desempenho desses animais, considerando a realidade da atividade leiteira no País. Essa revisão tem como objetivo apresentar dados sobre o potencial de produção e reprodução de vacas mestiças Holandês x Zebu, além dos principais desafios enfrentados pelos produtores para melhorar a eficiência dos seus rebanhos.

The challenge of milk producers in Brazil is to find the balance between production and sustainability of milk production systems. Approximately 70% of Brazilian dairy herds consists in crossbreeding Holstein x Zebu cows, which are kept in semi-intensive management system. Basic and applied researches aimed at understanding the particularities about the productive and reproductive physiology of dairy crossbred females are extremely important to help increase the performance of these animals, considering the reality of dairy farming in our country. This review aims to present data about potential of production and reproduction of crossbred Holstein x Zebu dairy cows, and the challenges to improve their performance.

Reprodução de vacas mestiças: potencialidade e desafios / Reproduction of crossbreeding dairy cows: potentiality and challenges

O desafio dos produtores de leite do Brasil consiste em buscar o equilíbrio entre produção de leite e sustentabilidade dos sistemas de produção. Aproximadamente 70% do rebanho leiteiro do Brasil é composto por vacas mestiças Holandês x Zebu, mantidas em sistema de manejo semi-intensivo. Pesquisas básicas e aplicadas que visam compreender as particularidades da produção e reprodução de fêmeas mestiças leiteiras são extremamente importantes para auxiliar na melhoria do desempenho desses animais, considerando a realidade da atividade leiteira no País. Essa revisão tem como objetivo apresentar dados sobre o potencial de produção e reprodução de vacas mestiças Holandês x Zebu, além dos principais desafios enfrentados pelos produtores para melhorar a eficiência dos seus rebanhos.(AU)

The challenge of milk producers in Brazil is to find the balance between production and sustainability of milk production systems. Approximately 70% of Brazilian dairy herds consists in crossbreeding Holstein x Zebu cows, which are kept in semi-intensive management system. Basic and applied researches aimed at understanding the particularities about the productive and reproductive physiology of dairy crossbred females are extremely important to help increase the performance of these animals, considering the reality of dairy farming in our country. This review aims to present data about potential of production and reproduction of crossbred Holstein x Zebu dairy cows, and the challenges to improve their performance.(AU)

Desempenho de novilhas Holandês na produção de embriões F1 Holandês-Zebu, em condições tropicais / Performance of Holstein heifers for F1 Holstein-Zebu embryo production, in tropical conditions

A produção in vivo de embriões bovinos é uma alternativa para a formação e manutenção de rebanhos mestiços F1 destinados à produção de leite. Objetivou-se estudar o potencial de utilização de novilhas da raça Holandês, mantidas em pasto e suplementadas, como doadoras de embrião, nas épocas de verão e inverno. Procederam-se superovulação e coleta de embriões em sete novilhas em cada época. Foram obtidos os dados climáticos, a temperatura retal e a frequência respiratória das doadoras. No verão, observou-se maior índice de temperatura e umidade (ITU) às 6h, 12h e 18h, bem como maior (P0,05) na média de estruturas recuperadas (20,14±17,47 vs. 8,57±9,40), embriões viáveis (14,57±11,91 vs. 7,14±7,24) e congeláveis (13,28±11,39 vs. 6,57±6,24) obtidos no inverno e no verão, respectivamente. Sob as condições estudadas, novilhas da raça Holandês podem ser utilizadas para a produção de embriões F1, tanto no verão, quanto no inverno.

In vivo embryo production (embryo transfer) is an alternative for F1 dairy herds formation and maintenance. The aim of this study was to evaluate the potential of utilization of grazing and supplemented Holstein heifers as embryo donors in summer or winter. Superovulation was performed in seven heifers on each season. Climatic parameters, as well as rectal temperature and respiratory rate of donors were measured. Temperature and humidity index (THI) was higher (p0.05). Holstein heifers can be used as embryo donors in both summer and winter, under the given conditions.

Desempenho de novilhas Holandês na produção de embriões F1 Holandês-Zebu, em condições tropicais / Performance of Holstein heifers for F1 Holstein-Zebu embryo production, in tropical conditions

A produção in vivo de embriões bovinos é uma alternativa para a formação e manutenção de rebanhos mestiços F1 destinados à produção de leite. Objetivou-se estudar o potencial de utilização de novilhas da raça Holandês, mantidas em pasto e suplementadas, como doadoras de embrião, nas épocas de verão e inverno. Procederam-se superovulação e coleta de embriões em sete novilhas em cada época. Foram obtidos os dados climáticos, a temperatura retal e a frequência respiratória das doadoras. No verão, observou-se maior índice de temperatura e umidade (ITU) às 6h, 12h e 18h, bem como maior (P<0,05) temperatura retal das doadoras às 18h. A porcentagem de animais que respondeu à superovulação foi de 71,4% (5/7) no inverno e 85,7% (6/7) no verão. O número total de estruturas recuperadas por doadora variou de um a 49 no inverno, e de zero a 23 no verão. Não houve diferença (P>0,05) na média de estruturas recuperadas (20,14±17,47 vs. 8,57±9,40), embriões viáveis (14,57±11,91 vs. 7,14±7,24) e congeláveis (13,28±11,39 vs. 6,57±6,24) obtidos no inverno e no verão, respectivamente. Sob as condições estudadas, novilhas da raça Holandês podem ser utilizadas para a produção de embriões F1, tanto no verão, quanto no inverno.(AU)

In vivo embryo production (embryo transfer) is an alternative for F1 dairy herds formation and maintenance. The aim of this study was to evaluate the potential of utilization of grazing and supplemented Holstein heifers as embryo donors in summer or winter. Superovulation was performed in seven heifers on each season. Climatic parameters, as well as rectal temperature and respiratory rate of donors were measured. Temperature and humidity index (THI) was higher (p<0.05) in summer at 6:00, 12:00 and 18:00, as rectal temperature at 18:00. Response to superovulation was observed in 71.4% (5/7) and 85.7% (6/7) of donors in winter and summer, respectively. Total ova/embryo recovered varied from 1 to 49 in winter and 0 to 23 in summer. Average ova/embryo, viable and freezable embryo was respectively, 20.14±17.47; 14.57±11.91 and 13.28±11.39 in winter and 8.57±9.40; 7.14±7.24 and 6.57±6.24 in summer (P>0.05). Holstein heifers can be used as embryo donors in both summer and winter, under the given conditions.(AU)