Unveiling the Role of IGF-I in Fertility: Effect of Long-Acting Bovine Somatotropin (bST) on Terminal Follicular Development and Fertility during an Annual Reproductive Cycle in Sheep.

The study aimed to assess the effect of long-acting bST treatment, in a dose that only increases IGF-I plasma concentrations, on ovarian and fertility markers of estrous synchronized ewes that were fed to keep their bodyweight. Three experiments were designed to evaluate this effect: in Experiment 1, 18 ewes were distributed in groups (bST 0, 30, 50 mg) to measure plasma IGF-I and insulin for 15 days; in Experiment 2, 92 ewes (5 replicates) in two groups (0 and 30 mg bST) were synchronized using a 6-day progesterone protocol during the breeding season to assess the effect of bST on follicular and luteal performances, estrous and ovulation, and fertility after mating. In Experiment 3, 50 ewes (3 replicates) were used to repeat the study before but during anestrus. Results indicate that 50 mg bST increased IGF-I and insulin plasma concentrations, but 30 mg bST only increased IGF-I concentrations; and that only during the breeding season did 30 mg bST increase the number of lambs born and the reproductive success of ovulatory-sized follicles compared to controls. This occurred without it affecting any other reproductive marker. In conclusion, 30 mg bST treatment may improve oocyte competence for fertility during the breeding season.

Effect of recombinant bovine somatotropin on the reproductive efficiency of beef cows subjected to differently timed-artificial insemination protocols.

This study aimed to verify the reproductive efficiency of beef cows treated with recombinant bovine somatotropin (rbST). Study 1, Bos indicus cows were distributed (three groups). The control group (CG) was subjected: on day zero (d0), the animals received a CIDR and oestradiol benzoate (EB); on (d8, CIDR was removed, and PGF2α and oestradiol cypionate (EC) were administered; on d10, timed Artificial Insemination (TAI) was performed; on d45, pregnancy diagnosis was made. The rbST on d0 group (bST0G) was subjected to an identical protocol as CG, except for the addition of 250 mg rbST on d0. The rbST on d8 group (bST8G) was subjected to the same protocol as bST0G, except that the rbST was administered on d8 rather. In study 2, the animals followed the same design which was used in Bos taurus cows. The follicular growth rate (FGR) was calculated between d8 and d10. In study 1, pregnancy/artificial insemination (P/AI) did not differ among the treatments. FGR in bST8G was higher than in other groups. In study 2, bST0G showed higher Pregnancy/Artificial Insemination (P/AI) (p < .05) when compared with other groups. bST0G showed a different FGR (p < .0001) than the other groups. In conclusion, rbST (Bos indicus cows) did not increase P/AI, but it did promote follicular growth when administered on d8; the rbST administered on d0 improved P/AI (p < .05) and the FGR in Bos taurus cows.

Use of new recombinant proteins for ovarian stimulation in ruminants.

Currently, gonadotropin products (follicle stimulating hormone, FSH, and luteinizing hormone, LH) used in animal reproduction are produced by extraction and purification from abattoir-derived pituitary glands. This method, relying on animal-derived materials, carries the potential risk of hormone contamination and pathogen transmission. Additionally, chorionic gonadotropins are extracted from the blood of pregnant mares (equine chorionic gonadotropin; eCG) or the urine of pregnant women (human chorionic gonadotropin; hCG). However, recent advancements have introduced recombinant gonadotropins for assisted animal reproduction therapies. The traditional use of FSH for superovulation has limitations, including labor requirements and variability in superovulation response, affecting the success of in vivo (SOV) and in vitro (OPU/IVEP) embryo production. FSH treatment for superstimulation before OPU can promote the growth of a homogenous follicular population and the recovery of competent oocytes suitable for IVEP procedures. At present, a single injection of a preparation of long-acting bovine recombinant FSH (rFSH) produced similar superovulation responses resulting in the production of good-quality in vivo and in vitro embryos. Furthermore, the treatment with eCG at FTAI protocol has demonstrated its efficacy in promoting follicular growth, ovulation, and P/AI, mainly in heifers and anestrous cows. Currently, treatment with recombinant glycoproteins with eCG-like activity (r-eCG) have shown promising results in increasing follicular growth, ovulation, and P/AI in cows submitted to P4/E2 -based protocols. Bovine somatotropin (bST) is a naturally occurring hormone found in cows. Recombinant bovine somatotropin (rbST), produced through genetic engineering techniques, has shown potential in enhancing reproductive outcomes in ruminants. Treatment with rbST has been found to improve P/IA, increase donor embryo production, and enhance P/ET in recipients. The use of recombinant hormones allows to produce non-animal-derived products, offering several advantages in assisted reproductive technologies for ruminants. This advancement opens up new possibilities for improving reproductive efficiency and success rates in the field of animal reproduction.

Use of new recombinant proteins for ovarian stimulation in ruminants

Currently, gonadotropin products (follicle stimulating hormone, FSH, and luteinizing hormone, LH) used in animal reproduction are produced by extraction and purification from abattoir-derived pituitary glands. This method, relying on animal-derived materials, carries the potential risk of hormone contamination and pathogen transmission. Additionally, chorionic gonadotropins are extracted from the blood of pregnant mares (equine chorionic gonadotropin; eCG) or the urine of pregnant women (human chorionic gonadotropin; hCG). However, recent advancements have introduced recombinant gonadotropins for assisted animal reproduction therapies. The traditional use of FSH for superovulation has limitations, including labor requirements and variability in superovulation response, affecting the success of in vivo (SOV) and in vitro (OPU/IVEP) embryo production. FSH treatment for superstimulation before OPU can promote the growth of a homogenous follicular population and the recovery of competent oocytes suitable for IVEP procedures. At present, a single injection of a preparation of long-acting bovine recombinant FSH (rFSH) produced similar superovulation responses resulting in the production of good-quality in vivo and in vitro embryos. Furthermore, the treatment with eCG at FTAI protocol has demonstrated its efficacy in promoting follicular growth, ovulation, and P/AI, mainly in heifers and anestrous cows. Currently, treatment with recombinant glycoproteins with eCG-like activity (r-eCG) have shown promising results in increasing follicular growth, ovulation, and P/AI in cows submitted to P4/E2 -based protocols. Bovine somatotropin (bST) is a naturally occurring hormone found in cows. Recombinant bovine somatotropin (rbST), produced through genetic engineering techniques, has shown potential in enhancing reproductive outcomes in ruminants. Treatment with rbST has been found to improve P/IA, increase donor embryo production, and enhance P/ET in recipients. The use of recombinant hormones allows to produce non-animal-derived products, offering several advantages in assisted reproductive technologies for ruminants. This advancement opens up new possibilities for improving reproductive efficiency and success rates in the field of animal reproduction.(AU)

Impact of recombinant bovine somatotropin, progesterone, and estradiol benzoate on ovarian follicular dynamics in Bos taurus taurus cows using a protocol for estrus and ovulation synchronization.

This study aimed to evaluate the effect of recombinant bovine somatotropin (bST) in combination with progesterone (P4) and estradiol benzoate (EB) on ovarian follicular dynamics using a protocol for estrus and ovulation synchronization in crossbred Bos taurus taurus cows. Twenty-four non-lactating multiparous cows were randomly assigned to two groups: the recombinant bovine somatotropin group (GbST; n = 11) received an intravaginal P4 device (1.5 g), estradiol benzoate (EB = 1.0 mg IM), bST (500 mg SC), and an ovarian ultrasonography (US) on day zero (d0 = beginning of the study); d-cloprostenol (150 µg, IM), US, and P4 removal on d8; 1.0 mg of EB (IM) on d9; and US on d10 and d15. On the other hand, to the control group (GC; n = 13), the same protocol as the GbST was applied, except for the non-receipt of bST on d0. The follicles were measured and evaluated on d0, d8, and d10, as were the corpora lutea (CL) on d15 (using ultrasonography). The effect of the two treatments (GbST vs. GC) on the follicle size, CL (F-test), and ovulation rate (logistic regression) were evaluated. The GbST showed a greater follicle diameter on d10 (14.5 mm) than the GC (12.1 mm; P < 0.03), as well as a greater diameter of CL on d15 (19.7 vs. 16.9 mm, P < 0.01). In addition, in the former, the ovulation rate (90.9 vs. 69.2%, P = 0.09) was observed to be greater. It was concluded that the combination of bST, P4, and EB in synchronization for estrus and ovulation protocols significantly increased the diameter of the preovulatory follicle, produced a higher follicular growth rate, and a greater diameter of the corpus luteum. Additionally, there was a higher percentage of cows with ovulation compared to the group that did not receive bST.

Impact of recombinant bovine somatotropin, progesterone, and estradiol benzoate on ovarian follicular dynamics in Bos taurus taurus cows using a protocol for estrus and ovulation synchronization.

This study aimed to evaluate the effect of recombinant bovine somatotropin (bST) in combination with progesterone (P4) and estradiol benzoate (EB) on ovarian follicular dynamics using a protocol for estrus and ovulation synchronization in crossbred Bos taurus taurus cows. Twenty-four non-lactating multiparous cows were randomly assigned to two groups: the recombinant bovine somatotropin group (GbST; n = 11) received an intravaginal P4 device (1.5 g), estradiol benzoate (EB = 1.0 mg IM), bST (500 mg SC), and an ovarian ultrasonography (US) on day zero (d0 = beginning of the study); d-cloprostenol (150 µg, IM), US, and P4 removal on d8; 1.0 mg of EB (IM) on d9; and US on d10 and d15. On the other hand, to the control group (GC; n = 13), the same protocol as the GbST was applied, except for the non-receipt of bST on d0. The follicles were measured and evaluated on d0, d8, and d10, as were the corpora lutea (CL) on d15 (using ultrasonography). The effect of the two treatments (GbST vs. GC) on the follicle size, CL (F-test), and ovulation rate (logistic regression) were evaluated. The GbST showed a greater follicle diameter on d10 (14.5 mm) than the GC (12.1 mm; P < 0.03), as well as a greater diameter of CL on d15 (19.7 vs. 16.9 mm, P < 0.01). In addition, in the former, the ovulation rate (90.9 vs. 69.2%, P = 0.09) was observed to be greater. It was concluded that the combination of bST, P4, and EB in synchronization for estrus and ovulation protocols significantly increased the diameter of the preovulatory follicle, produced a higher follicular growth rate, and a greater diameter of the corpus luteum. Additionally, there was a higher percentage of cows with ovulation compared to the group that did not receive bST.

Influência do Hormônio do Crescimento na concentração de testosterona plasmática e nas características seminais de touros jovens e adultos da raça Nelore / Influence of Growth Hormone on plasma testosterone concentration and seminal characteristics of young and adult Nellore bulls

Estudou-se o efeito do Hormônio do Crescimento bovino (bGH) sobre os parâmetros seminais e a concentração sérica de testosterona de touros da raça Nelore. Dezesseis touros foram distribuídos em um delineamento fatorial 2 x 2 (duas idades e dois níveis de r-bST), com quatro animais em cada tratamento. As aplicações de r-bST foram realizadas a cada 14 dias, totalizando nove aplicações por animal, em um período experimental de 120 dias. As coletas de sêmen foram realizadas a cada 15 dias e, para determinar as concentrações de testosterona, foram realizadas coletas de sangue a cada quatro horas, num total de 24 horas, e a cada 30 dias a partir da primeira aplicação de r-bST. O sêmen dos touros adultos tratados com r-bST apresentaram maior motilidade e vigor (P<0,05) em relação aos animais controles (79,70±11,56% vs 64,06±23,65%) e (3,80±0,88 vs 2,92±1,25), respectivamente; entretanto, as demais características seminais não foram influenciadas (P>0,05) pelo tratamento com r-bST. Os aspectos físicos do sêmen dos touros jovens não foram afetados (P>0,05) pelo tratamento com r-bST. Entretanto o tratamento com r-bST diminuiu os defeitos morfológicos menores (delgado, gigante normal, pequeno normal, globoso, cabeça isolada normal, abaxial, cauda dobrada e enrolada levemente e gota distal) em relação aos jovens não tratados (P<0,05). As concentrações séricas de testosterona foram influenciadas (P<0,05) pelo tratamento, aos 120 dias após a primeira aplicação do r-bST, e apresentaram tendência de três picos no período de 24 horas.

The aim of this trial was to study the effect of Growth Hormone (GH) on the seminal parameters and testosterone profile from Nellore bulls. Sixteen bulls were allocated in a 2 x 2 factorial arrangement (two ages and two r-bST levels), with four animals per treatment. The r-bST was injected every 14 days, with a total of nine injections per animal, during the 120 days of the experimental period. The semen collections were done every 15 days and blood samples were collected in four hour intervals for 24 hours, and in 30 day intervals from the first r-bST injection for testosterone profile. The semen of adult bulls treated with r-bST showed greater MOT and VIG (P<0.05) in relation to the control (79.70±11.56% vs 64.06±23.65%) and (3.80±0.88 vs 2.92±1.25) respectively; however, the other evaluated seminal parameters were not affected (P>0.05) by the r-bST treatment. The physical measurements of the semen of young animals was also unaffected (P>0.05) by r-bST injection. However, the treatment with r-bST decreased the number of minor morphologic defects (narrow head, giant head, small normal head, round head, free normal head, abaxial implantation, simple bent tail and distal droplet) compared to untreated young bulls (P<0.05). The serum testosterone concentration was influenced (P<0.05) by treatment, at 120 days after the first injection of r-bST and they showed a tendency of three picks in a 24 hour period of sampling.

Influência do Hormônio do Crescimento na concentração de testosterona plasmática e nas características seminais de touros jovens e adultos da raça Nelore / Influence of Growth Hormone on plasma testosterone concentration and seminal characteristics of young and adult Nellore bulls

Estudou-se o efeito do Hormônio do Crescimento bovino (bGH) sobre os parâmetros seminais e a concentração sérica de testosterona de touros da raça Nelore. Dezesseis touros foram distribuídos em um delineamento fatorial 2 x 2 (duas idades e dois níveis de r-bST), com quatro animais em cada tratamento. As aplicações de r-bST foram realizadas a cada 14 dias, totalizando nove aplicações por animal, em um período experimental de 120 dias. As coletas de sêmen foram realizadas a cada 15 dias e, para determinar as concentrações de testosterona, foram realizadas coletas de sangue a cada quatro horas, num total de 24 horas, e a cada 30 dias a partir da primeira aplicação de r-bST. O sêmen dos touros adultos tratados com r-bST apresentaram maior motilidade e vigor (P<0,05) em relação aos animais controles (79,70±11,56% vs 64,06±23,65%) e (3,80±0,88 vs 2,92±1,25), respectivamente, entretanto, as demais características seminais não foram influenciadas (P>0,05) pelo tratamento com r-bST. Os aspectos físicos do sêmen dos touros jovens não foram afetados (P>0,05) pelo tratamento com r-bST. Entretanto o tratamento com r-bST diminuiu os defeitos morfológicos menores (delgado, gigante normal, pequeno normal, globoso, cabeça isolada normal, abaxial, cauda dobrada e enrolada levemente e gota distal) em relação aos jovens não tratados (P<0,05). As concentrações séricas de testosterona foram influenciadas (P<0,05) pelo tratamento, aos 120 dias após a primeira aplicação do r-bST, e apresentaram tendência de três picos no período de 24 horas.(AU)

The aim of this trial was to study the effect of Growth Hormone (GH) on the seminal parameters and testosterone profile from Nellore bulls. Sixteen bulls were allocated in a 2 x 2 factorial arrangement (two ages and two r-bST levels), with four animals per treatment. The r-bST was injected every 14 days, with a total of nine injections per animal, during the 120 days of the experimental period. The semen collections were done every 15 days and blood samples were collected in four hour intervals for 24 hours, and in 30 day intervals from the first r-bST injection for testosterone profile. The semen of adult bulls treated with r-bST showed greater MOT and VIG (P<0.05) in relation to the control (79.70±11.56% vs 64.06±23.65%) and (3.80±0.88 vs 2.92±1.25) respectively, however, the other evaluated seminal parameters were not affected (P>0.05) by the r-bST treatment. The physical measurements of the semen of young animals was also unaffected (P>0.05) by r-bST injection. However, the treatment with r-bST decreased the number of minor morphologic defects (narrow head, giant head, small normal head, round head, free normal head, abaxial implantation, simple bent tail and distal droplet) compared to untreated young bulls (P<0.05). The serum testosterone concentration was influenced (P<0.05) by treatment, at 120 days after the first injection of r-bST and they showed a tendency of three picks in a 24 hour period of sampling.(AU)

Impact of bovine somatotropin (bST)on the milk production and genetic evaluation of Holstein cattle / Impacto da utilização da somatotropina bovina (bST) sobre a produção de leite e a avaliação genética de bovinos da raça Holandesa

The objective of this work was to study the influence of the use of bovine somatotropin (bST) on milk yield (MP305) and genetic evaluation of MP305 of Holstein Cattle. Data from 474 bulls and observations concerning 3.341 lactations of 1.271 cows during the period from 1999 to 2003 were used. Variance analysis was performed by the GLM SAS procedure (2003) and parameters in one animal model. The heritability estimates for model 1(bST as a fixed effect) and model 2 (absence of this effect) were respectively 0.26 and 0.23 for the two analyses and correlations between estimated breeding values for bulls sets a (all evaluated), b (best 20%), c (best 10%) and d (best 5%) were, respectively, 0.9484, 0.9829, 0.9752 and 0.8974. Variance analysis of variance showed that the average PL305 increased significantly (P 0.0001) with the increase number of bST applications. The Spearman correlations coefficients between breeding values of bulls were high, with or without the use of bST in the model, indicating that the use of this technology does not affect the classification of genetically evaluated bulls.

O objetivo do presente trabalho foi estudar a influência do uso da somatotropina bovina (bST) sobre a produção de leite (PL305) e a avaliação genética da PL305 de bovinos da raça Holandesa. Foram utilizados dados referentes a 474 touros e observações referentes a 3341 lactações de 1271 vacas, durante o período de 1999 a 2003. A análise de variância foi realizada pelo procedimento GLM do SAS (2003) e os parâmetros genéticos sob modelo animal unicaracterístico. As estimativas de herdabilidades para o modelo 1 (bST como efeito fixo) e modelo 2 (ausência desse efeito) foram respectivamente de 0,26 e 0,23 e a correlações entre os valores genéticos preditos para os conjuntos de touros a (todos avaliados), b (os melhores 20%), c (os melhores 10%) e d (os melhores 5%) foram, respectivamente, 0,9484, 0,9829, 0,9752 e 0,8974. A análise de variância demonstrou que as médias de PL305 aumentaram significativamente (P 0,0001), com o aumento do número de aplicações do bST. As altas correlações de Spearman entre os valores genéticos dos touros, considerando-se ou não o uso do bST no modelo, indicam que o uso desta tecnologia não interfere na classificação dos touros avaliados geneticamente.

Impacto da utilização da somatotropina bovina (bST) sobre a produção de leite e a avaliação genética de bovinos da raça holandesa / Impact of bovine somatotropin (bST) on the milk production and genetic evaluation of Holstein cattle

O objetivo do presente trabalho foi estudar a influência do uso da somatotropina bovina (bST) sobre a produção de leite (PL305) e a avaliação genética da PL305 de bovinos da raça Holandesa. Foram utilizados dados referentes a 474 touros e observações referentes a 3341 lactações de 1271 vacas, durante o período de 1999 a 2003. A análise de variância foi realizada pelo procedimento GLM do SAS (2003) e os parâmetros genéticos sob modelo animal unicaracterístico. As estimativas de herdabilidades para o modelo 1 (bST como efeito fixo) e modelo 2 (ausência desse efeito) foram respectivamente de 0,26 e 0,23 e a correlações entre os valores genéticos preditos para os conjuntos de touros a (todos avaliados), b (os melhores 20% ), c (os melhores 10%) e d (os melhores 5%) foram, respectivamente, 0,9484, 0,9829, 0,9752 e 0,8974. A análise de variância demonstrou que as médias de PL305 aumentaram significativamente (P<0,0001), com aumento do número de aplicações do bST. As altas correlações de Spearman entre os valores genéticos dos touros, considerando-se ou não o uso do bST no modelo, indicam que o uso desta tecnologia não interfere na classificação dos touros avaliados geneticamente.

The objective of this work was to study the influence of the use of bovine somatotropin (bST) on milk yield (MP305) and genetic evaluation of MP305 of Holstein Cattle. Data from 474 bulls and observations concerning 3.341 lactations of 1.271 cows during the period from 1999 to 2003 were used. Variance analysis was performed by the GLM SAS procedure (2003) and parameters in one animal model. The heritability estimates for model 1(bST as a fixed effect) and model 2 (absence of this effect) were respectively 0.26 and 0.23 for the two analyses and correlations between estimated breeding values for bulls sets a (all evaluated), b (best 20%), c (best 10%) and d (best 5%) were, respectively, 0.9484, 0.9829, 0.9752 and 0.8974. Variance analysis of variance showed that the average PL305 increased significantly (P<0.0001) with the increase number of bST applications. The Spearman correlations coefficients between breeding values of bulls were high, with or without the use of bST in the model, indicating that the use of this technology does not affect the classification of genetically evaluated bulls.

Efeito da somatotropina recombinante bovina (rbST) sobre os níveis de marcadores metabólicos de touros semiconfinados das raças Aberdeen Angus e Brangus / Effect of recombinant bovine somatotropin (rbST) on the concentrations of metabolic markers in semi-confined sires Aberdeen Angus and Brangus

O objetivo deste estudo foi avaliar o efeito da somatotropina recombinante bovina (rbST) sobre os marcadores do metabolismoenergético, proteico, mineral e hepático de touros mantidos em semiconfinamento. Foram utilizados 20 touros de raçasAberdeen Angus e Brangus, sendo divididos aleatoriamente em dois grupos (Placebo e rbST), para que no Placebo fosseadministrado via subcutânea duas doses de NaCl, 0,9% e no rbST fosse administrado o rbST (Lactotropin®). Foram realizadascinco coletas de sangue, com intervalo de 14 dias, para avaliação da concentração de triacilgliceróis e colesterol comomarcadores energéticos, ureia, como indicador proteico, fosfatase alcalina e fósforo como marcadores minerais e asenzimas aspartato aminotransferase (AST) e a gama glutamiltransferase (GGT) como indicadoras da função hepática. Aaplicação de rbST não influenciou os marcadores energéticos, minerais, e proteico, exceto a enzima hepática GGT (P 0,05).Estes resultados indicam que a utilização do rbST em touros não alterou o metabolismo, pois os parâmetros avaliadosmantiveram-se dentro dos padrões considerados fisiológicos para a espécie.

The aim of this study was to evaluate the effect of recombinant bovine somatotropin (rbST) on metabolic markers for energy, protein, mineral and hepatic metabolism of sires kept grazing and receiving concentrate. Twenty sires Aberdeen Angus and Brangus used for this experiment were divided in two groups (Placebo and rbST). The group Placebo received subcutaneous administration of NaCl, 0.9% and rbST receive rbST twice. Five blood collections with 14 days of interval were made for evaluation of triglyceride and cholesterol as energetic metabolism markers, urea, as proteic marker, alkaline phosphatase and phosphorus as minerals markers and aspartate aminotransferase (AST) and gamma glutamyltransferase (GGT) as indicators of the hepatic function. The rbST did not influence the energetic, mineral and proteic markers, except the hepatic enzyme GGT (P<0,05). These results indicated that the use of rbST in sires did not affect metabolism, therefore evaluated parameters remaining in the physiological range for the specie.

Efeito da somatotropina recombinante bovina (rbST) sobre os níveis de marcadores metabólicos de touros semiconfinados das raças Aberdeen Angus e Brangus / Effect of recombinant bovine somatotropin (rbST) on the concentrations of metabolic markers in semi-confined sires Aberdeen Angus and Brangus

O objetivo deste estudo foi avaliar o efeito da somatotropina recombinante bovina (rbST) sobre os marcadores do metabolismoenergético, proteico, mineral e hepático de touros mantidos em semiconfinamento. Foram utilizados 20 touros de raçasAberdeen Angus e Brangus, sendo divididos aleatoriamente em dois grupos (Placebo e rbST), para que no Placebo fosseadministrado via subcutânea duas doses de NaCl, 0,9% e no rbST fosse administrado o rbST (Lactotropin®). Foram realizadascinco coletas de sangue, com intervalo de 14 dias, para avaliação da concentração de triacilgliceróis e colesterol comomarcadores energéticos, ureia, como indicador proteico, fosfatase alcalina e fósforo como marcadores minerais e asenzimas aspartato aminotransferase (AST) e a gama glutamiltransferase (GGT) como indicadoras da função hepática. Aaplicação de rbST não influenciou os marcadores energéticos, minerais, e proteico, exceto a enzima hepática GGT (P 0,05).Estes resultados indicam que a utilização do rbST em touros não alterou o metabolismo, pois os parâmetros avaliadosmantiveram-se dentro dos padrões considerados fisiológicos para a espécie.

The aim of this study was to evaluate the effect of recombinant bovine somatotropin (rbST) on metabolic markers for energy, protein, mineral and hepatic metabolism of sires kept grazing and receiving concentrate. Twenty sires Aberdeen Angus and Brangus used for this experiment were divided in two groups (Placebo and rbST). The group Placebo received subcutaneous administration of NaCl, 0.9% and rbST receive rbST twice. Five blood collections with 14 days of interval were made for evaluation of triglyceride and cholesterol as energetic metabolism markers, urea, as proteic marker, alkaline phosphatase and phosphorus as minerals markers and aspartate aminotransferase (AST) and gamma glutamyltransferase (GGT) as indicators of the hepatic function. The rbST did not influence the energetic, mineral and proteic markers, except the hepatic enzyme GGT (P<0,05). These results indicated that the use of rbST in sires did not affect metabolism, therefore evaluated parameters remaining in the physiological range for the specie.(AU)

Estimates of correlations among yield traits and somatic cell score with different models to adjust for bovine somatotropin effects on Holstein dairy cows

Records of Holstein cows from the Dairy Records Processing Center at Raleigh, NC were edited to obtain three data sets: 65,720 first, 50,694 second, and 65,445 later lactations. Correlations among yield traits and somatic cell score were estimated with three different models: 1) bovine somatotropin (bST) administration ignored, 2) bST administration as a fixed effect and 3) administration of bST as part of the contemporary group (herd-year-month-bST). Heritability estimates ranged from 0.13 to 0.17 for milk, 0.12 to 0.20 for fat, 0.14 to 0.16 for protein yields, and 0.08 to 0.09 for somatic cell score. Estimates were less for later than first lactations. Estimates of genetic correlations among yields ranged from 0.35 to 0.85 with no important differences between estimates with the 3 models. Estimates for lactation 2 agreed with estimates for lactation 1. Estimates of genetic correlations for later lactations were generally greater than for lactations 1 and 2 except between milk and protein yields. Estimates of genetic correlations between yields and somatic cell score were mostly negative or small (-0.45 to 0.11). Estimates of environmental correlations among yield traits were similar with all models (0.77 to 0.97). Estimates of environmental correlations between yields and somatic cell score were negative (-0.22 to -0.14). Estimates of phenotypic correlations among yield traits ranged from 0.70 to 0.95. Estimates of phenotypic correlations between yields and somatic cell score were small and negative. For all three data sets and all traits, no important differences in estimates of genetic parameters were found for the two models that adjusted for bST and the model that did not

Impact of bovine somatotropin on ranking for genetic value of dairy sires for milk yield traits and somatic cell score

Records of Holstein cows were used to examine how different models account for the effect of bovine somatotropin (bST) treatment on genetic evaluation of dairy sires for yield traits and somatic cell score. Data set 1 included 65,720 first-lactation records. Set 2 included 50,644 second-lactation records. Set 3 included 45,505 records for lactations three, four and five. Estimated breeding values (EBV) of sires were with three different animal models. With Model 1, bST administration was ignored. With Model 2, bST administration was used as a fixed effect. With Model 3, administration of bST was used to define the contemporary group (herd-year-month of calving-bST). Correlations for EBV of 1,366 sires with treated daughters between pairs of the three models were calculated for milk, fat and protein yields and somatic cell score for the three data sets. Correlations for EBV of sires between pairs of models for all traits ranged from 0.971 to 0.999. Fractions of sires with bST-treated progeny selected in common (top 10 to 15%) were 0.94 and usually greater for all pairs of models for all traits and parities. For this study, the method of statistical adjustment for bST treatment resulted in a negligible effect on genetic evaluations of sires when some daughters were treated with bST and suggests that selection of sires to produce the next generation of sires and cows might not be significantly affected by how the effect of bST is modeled for prediction of breeding values for milk, fat and protein yields and somatic cell score