Vacas leiteira de alta produção têm apresentado declínio da eficiência reprodutiva. Essa redução é devido a causas multifatoriais, entre elas a baixa concentração de estradiol (E2) no proestro e a baixa concentração de progesterona (P4) no ciclo estral subsequentente. O objetivo deste trabalho foi comparar o uso de gonadotrofina exógena na dinâmica folicular e na taxa de prenhez de vacas submetidas ao protocolo Ovsynch (Experimento 1) ou a protocolos utilizando P4 e E2 (Experimento 2). No Experimento 1, animais de primeiro serviço foram pré-sincronizados com dois protocolos (Presynch ou Double-Ovsynch). Já os animais de segundo ou mais serviços foram resincronizados com o protocolo Resynch. Os animais receberam GnRH (1º GnRH), seguido 7 dias depois pela adiministração de prostaglandina F2α (PGF2α). Nesse momento os animais foram divididos homogeneamente por paridade e número de inseminação em um de dois tratamentos: sem FSH (Ovsynch, n = 561) ou com FSH (Ovsynch + FSH, n = 571). O segundo GnRH (2º GnRH) foi administrado 56 horas após a PGF2α e a inseminação em tempo fixo foi realizada 16 horas após. Amostras de sangue foram colhidas no 1º e no 2º GnRH, na PGF2α e 6 e 13 dias após o 2º GnRH para dosagem de P4. Ainda, no 2º GnRH dosou-se também E2 No Experimento 2, os animais foram sincronizados no dia 0 com um dispositivo de P4 associado a 2 mg de benzoato de estradiol. Oito dias após o dispositivo foi removido e os animais receberam uma dose de PGF2α. Neste mesmo momento, as vacas foram divididas homogeneamente por paridade, número de serviços prévios, escore de condição corporal e presença de CL no inicio do protocolo em três tratamentos: Controle (sem tratamento adicional; n = 232); eCG (400 UI de eCG; n = 232) e FSH (20 mg de FSH; n = 230). Todos os animais receberam GnRH e foram insemados 56h após a retirada do dispositivo. Foram colhidas amostras de sangue a cada 48h do dia 11 ao dia 22. No Experimento 1, não houve efeito do FSH na concetração sérica de E2 no 2º GnRH (P = 0,88), no tamanho do maior folículo no 2 º GnRH (P = 0,63), na taxa de ovulação ao 2º GnRH (P = 0,69) ou na concentração sérica de P4 no 6º (P = 0,15) e 13º (P = 0,36) dia após o 2º GnRH. A taxa de prenhez foi semelhante (P> 0,05) entre os animais tratados com Ovsynch (36,2%) e Ovsynch + FSH (39,1%). No Experimento 2, os tratamentos não alteraram o diâmetro do folículo ovulatório (P = 0,15), o intervalo entre a remoção do dispositivo de P4 e a ovulação (P = 0,30) e a taxa de ovulação (P = 0,44). Não houve efeito de tratamento na concentração sérica de P4 (P = 0,15). A taxa de prenhez foi diferente entre os tratamentos aos 30 dias após a IATF (Controle = 28,0a vs FSH = 18,7b vs eCG = 29,7a %; P = 0,01), mas não aos 60 dias (Controle = 21,6 vs FSH = 16,1 vs eCG = 24,1%; P = 0,08) e na perda de gestacional (Controle = 18,8 vs FSH = 14,0 vs eCG = 18,4%; P = 0,39). Assim, o tratamento com FSH não estimulou o crescimento folicular final e a função luteínica de vacas leiteiras de alta produção sincronizadas com os protocolos Ovsynch e P4/E2. / Fertility in high-producing dairy cows has decreased over the years, which has been associated with reduced estradiol (E2) concentrations during proestrus and suboptimal progesterone (P4) concentrations during early stages of gestation. The objectives of the present study were to evaluate the effects of exogenous gonadotropins on follicular dynamics and risk of pregnancy per artificial insemination (P/AI) in cows subjected to the Ovsynch protocol (Experiment 1) or to a P4/E2-based timed AI protocol (experiment 2). In experiment 1, cows were enrolled in the Ovsynch protocol (GnRH, 7 d PGF2α, 56 h GnRH, 16 h IA) either after presynchronization (Presynch or Double-Ovsynch; first AI postpartum) or 32 d after previous AI. At the PGF2α injection, cows were blocked by parity and number of AI and, within each block, randomly allocated to eitherreceive 20 mg of FSH at the moment of the PGF2α(Ovsynch + FSH, n = 571) or to remain as untreated control (Ovsynch, n = 561). Blood was sampled at the 1st and 2nd GnRH and PGF2α injections, as well as on d 6 and 13 after the 2nd GnRH to access P4 and E2 (at the 2nd GnRH only) concentrations. In experiment 2, cows were received a P4 device and 2 mg of estradiol benzoate. The device was removed 8 d later concurrently with an injection of PGF2α, followed by an injection of GnRH and AI at 56 h.At the PGF2α injection, cows were blocked by parity, number of AI, body condition score, and presence of a CL at device insertion.Within each block, cows were randomly allocated to receive either 20 mg of FSH (FSH, n = 230), 400 IU of eCG (eCG, n = 232), or no additional treatment at the moment of the PGF2α (Control, n = 232). Blood was sampled at every 48 h from 1 to 12 d after AI. In experiment 1, there was no effect of FSH on serum E2 at the 2nd GnRH (P = 0.88), follicle diameter at the 2nd GnRH (P = 0.63), ovulatory response to the 2nd GnRH (P = 0.69), or serum P4 on d 6 (P = 0.15) and 13 (P = 0.36) after the 2nd GnRH. Also, P/AI was similar (P > 0.05) between Ovsynch (36.2%) and Ovsynch + FSH (39.1%). In experiment 2, treatment did not affect ovulatory diameter (P = 0.15), interval from P4 device removal and ovulation (P = 0.30), ovulatory response to the 2nd GnRH (P = 0.44), and serum P4 (P = 0.15). Interestingly, treatment with FSH reduced (P = 0.01) P/AI on d 30 (Control = 28.0a vs. FSH = 18.7b vs. eCG = 29.7a %), but not on d 60after timed AI (Control = 21.6 vs. FSH = 16.1 vs. eCG = 24.1%; P = 0.08).The risk of pregnancy loss was not affected by treatment (Control = 18.8 vs. FSH = 14.0 vs. eCG = 18.4%; P = 0.39). In conclusion, treatment with FSH failed to enhance the final growth of the ovulatory follicle and did not improve luteal function after AI in high-producing dairy cows synchronized with either the Ovsynch or P4/E2-based timed AI protocols.

O presente experimento foi realizado com o objetivo de avaliar o impacto da inseminação artificial em tempo fixo (IATF) na eficiência reprodutiva de vacas de leite de alta produção inseminadas no período pós-parto. Vacas Holandesas com média de 50 dias pós-parto foram distribuídas homogeneamente em um de dois grupos experimentais, levando em consideração a presença ou ausência de corpo lúteo (CL), o escore de condição corporal e a produção de leite. No grupo Controle (G-Controle; n = 490), as vacas foram submetidas à observação do comportamento de aceitação de monta (duas vezes ao dia por uma hora) e inseminadas 12 horas após a primeira detecção. No grupo IATF (G-IATF; n = 495), as vacas receberam um implante auricular de norgestomet, mantido por oito dias, e 2 mg de benzoato de estradiol IM no dia 0 (D0; dia aleatório do ciclo estral). No momento da retirada do implante (D8) foram administrados 150 µg de prostaglandina F2α, 400 UI de gonadotrofina coriônica eqüina e 1 mg de cipionato de estradiol. A IATF foi realizada de 54 a 56 h após a retirada do implante auricular, concomitante à administração de 100 µg de gonadorelina. Após a IATF, as vacas foram submetidas à observação de cio com subseqüente inseminação, seguindo os mesmos critérios descritos para o G-Controle. Amostras de sangue foram colhidas de um subgrupo de animais (G-Controle, n = 50; G-IATF, n = 58) 5 e 11 dias após a primeira inseminação artificial (IA) para dosagem de progesterona (P4) circulante. Todos os animais foram mantidos no experimento até a terceira IA ou 150 dias após o parto e os tratamentos foram realizados no inverno e no verão. O diagnóstico de gestação foi realizado aos 30 dias pós-IA por ultrassonografia e aos 60 dias pós-IA por palpação transretal. Os dados binomiais foram analisados por regressão logística utilizando o PROC GLIMMIX e as variáveis contínuas por ANOVA utilizando PROC GLM do SAS. Não se verificou interação entre estação do ano e tratamento na análise das taxas de concepção, perda gestacional, intervalo entre IAs, intervalo parto-concepção (IPC) e taxa de prenhez aos 150 dias pós-parto. Os resultados são indicativos de que não existem diferenças nas taxas de concepção entre os diferentes grupos após as IAs (primeira, segunda e terceira). A perda gestacional relativa à primeira IA foi maior nas vacas do G-IATF. Os intervalos parto-primeira IA, parto-segunda IA e parto-concepção foram inferiores para as vacas do G-IATF. Entretanto, o intervalo entre a primeira e a segunda IA foi maior para o G-IATF. Não houve diferença na taxa de prenhez aos 150 dias entre os grupos. Ainda, a taxa de serviço (TS) nos primeiros 21 dias após o período voluntário de espera (PVE) foi maior para o grupo IATF. Entretanto, a TS entre 21 e 42 dias após o PVE foi maior para o G-Controle. As concentrações circulantes de P4 não diferiram entre os grupos e as estações do ano. Concluiu-se que o emprego da IATF 60 dias pós-parto foi eficiente para diminuir o IPC. Contudo, a porcentagem de vacas prenhes aos 150 pós-parto foi semelhante entre os dois tratamentos (Controle e IATF) / The aim of the present study was evaluate the impact of fixed-time artificial insemination (FTAI) on reproductive efficiency of high-producing dairy cows inseminated during the postpartum period. Holstein cows with average 50 days in milk were allocated to one of two groups considering the presence or absence of corpus luteum (CL), body condition score and milk production. On Control group (Control-G; n = 490), the cows were submitted to estrus detection twice per day for one h and were inseminated 12 hours after the first detection. On FTAI group (FTAI-G; n = 495), the cows received a norgestomet ear implant (kept for eight days) plus administration of 2 mg of estradiol benzoate i.m. on Day 0 (random day of the estrous cycle). The implant was removed on Day 8 followed by FTAI 54 to 56 h later and the administration of 100 µg of gonadorelin. On Day 8, cows received 400 IU eCG, 150 &micro:g of prostaglandin F2α and 1 mg of estradiol cypionate. After FTAI, cows were submitted to estrus detection and artificial insemination (AI) 12 h after. Blood samples were collected from a subset of animals (Control-G, n = 50; FTAI-G, n = 58) on Day 5 and 11 after the first AI to investigate serum progesterone concentration (P4). All animals were maintained on the experiment until 150 days post-partum and the treatments were conducted during the winter and summer. Pregnancy diagnosis was performed by ultrasonography 30 days after AI (Day 30) and by rectal palpation 60 days after AI (Day 60). Binomial data were analyzed by logistic regression using the PROC GLIMMIX and continuous variables by ANOVA using PROC GLM of SAS. No interaction was found between season and treatment when conception rate, pregnancy loss, interval between inseminations, interval from calving to conception and pregnancy rate 150 post-partum were analysed. The results indicate no differences on conception rate among both experimental groups after AI (first, second and third). However, the interval from calving to first and second AI and interval from calving to conception were lower on FTAI-G. No difference on pregnancy rate 150 days post-partum was found among groups. Pregnancy loss after first AI was greater on FTAI-G. The interval from calving to first AI, from calving to second AI and the interval from calving to conception were shorter on FTAI-G. However, the interval between first and second AI was longer on FTAI-G. There was no difference on pregnancy rate 150 days post-partum among treatments. Also, the service rate (SR) 21 days after the voluntary waiting period (VWP) was greater on FTAI-G compared to Control-G. Conversely, the SR was lower between 21 and 42 days after the VWP on FTAI-G. No difference was found in serum concentration of P4 among treatment groups and season. Thus, the use of FTAI 60 days post-partum was efficient to anticipate the conception of high-producing dairy cattle by reducing the interval from calving to conception, but did not increase the pregnancy rate 150 days post-partum

O presente experimento foi realizado com o objetivo de avaliar o impacto da inseminação artificial em tempo fixo (IATF) na eficiência reprodutiva de vacas de leite de alta produção inseminadas no período pós-parto. Vacas Holandesas com média de 50 dias pós-parto foram distribuídas homogeneamente em um de dois grupos experimentais, levando em consideração a presença ou ausência de corpo lúteo (CL), o escore de condição corporal e a produção de leite. No grupo Controle (G-Controle; n = 490), as vacas foram submetidas à observação do comportamento de aceitação de monta (duas vezes ao dia por uma hora) e inseminadas 12 horas após a primeira detecção. No grupo IATF (G-IATF; n = 495), as vacas receberam um implante auricular de norgestomet, mantido por oito dias, e 2 mg de benzoato de estradiol IM no dia 0 (D0; dia aleatório do ciclo estral). No momento da retirada do implante (D8) foram administrados 150 µg de prostaglandina F2α, 400 UI de gonadotrofina coriônica eqüina e 1 mg de cipionato de estradiol. A IATF foi realizada de 54 a 56 h após a retirada do implante auricular, concomitante à administração de 100 µg de gonadorelina. Após a IATF, as vacas foram submetidas à observação de cio com subseqüente inseminação, seguindo os mesmos critérios descritos para o G-Controle. Amostras de sangue foram colhidas de um subgrupo de animais (G-Controle, n = 50; G-IATF, n = 58) 5 e 11 dias após a primeira inseminação artificial (IA) para dosagem de progesterona (P4) circulante. Todos os animais foram mantidos no experimento até a terceira IA ou 150 dias após o parto e os tratamentos foram realizados no inverno e no verão. O diagnóstico de gestação foi realizado aos 30 dias pós-IA por ultrassonografia e aos 60 dias pós-IA por palpação transretal. Os dados binomiais foram analisados por regressão logística utilizando o PROC GLIMMIX e as variáveis contínuas por ANOVA utilizando PROC GLM do SAS. Não se verificou interação entre estação do ano e tratamento na análise das taxas de concepção, perda gestacional, intervalo entre IAs, intervalo parto-concepção (IPC) e taxa de prenhez aos 150 dias pós-parto. Os resultados são indicativos de que não existem diferenças nas taxas de concepção entre os diferentes grupos após as IAs (primeira, segunda e terceira). A perda gestacional relativa à primeira IA foi maior nas vacas do G-IATF. Os intervalos parto-primeira IA, parto-segunda IA e parto-concepção foram inferiores para as vacas do G-IATF. Entretanto, o intervalo entre a primeira e a segunda IA foi maior para o G-IATF. Não houve diferença na taxa de prenhez aos 150 dias entre os grupos. Ainda, a taxa de serviço (TS) nos primeiros 21 dias após o período voluntário de espera (PVE) foi maior para o grupo IATF. Entretanto, a TS entre 21 e 42 dias após o PVE foi maior para o G-Controle. As concentrações circulantes de P4 não diferiram entre os grupos e as estações do ano. Concluiu-se que o emprego da IATF 60 dias pós-parto foi eficiente para diminuir o IPC. Contudo, a porcentagem de vacas prenhes aos 150 pós-parto foi semelhante entre os dois tratamentos (Controle e IATF) / The aim of the present study was evaluate the impact of fixed-time artificial insemination (FTAI) on reproductive efficiency of high-producing dairy cows inseminated during the postpartum period. Holstein cows with average 50 days in milk were allocated to one of two groups considering the presence or absence of corpus luteum (CL), body condition score and milk production. On Control group (Control-G; n = 490), the cows were submitted to estrus detection twice per day for one h and were inseminated 12 hours after the first detection. On FTAI group (FTAI-G; n = 495), the cows received a norgestomet ear implant (kept for eight days) plus administration of 2 mg of estradiol benzoate i.m. on Day 0 (random day of the estrous cycle). The implant was removed on Day 8 followed by FTAI 54 to 56 h later and the administration of 100 µg of gonadorelin. On Day 8, cows received 400 IU eCG, 150 &micro:g of prostaglandin F2α and 1 mg of estradiol cypionate. After FTAI, cows were submitted to estrus detection and artificial insemination (AI) 12 h after. Blood samples were collected from a subset of animals (Control-G, n = 50; FTAI-G, n = 58) on Day 5 and 11 after the first AI to investigate serum progesterone concentration (P4). All animals were maintained on the experiment until 150 days post-partum and the treatments were conducted during the winter and summer. Pregnancy diagnosis was performed by ultrasonography 30 days after AI (Day 30) and by rectal palpation 60 days after AI (Day 60). Binomial data were analyzed by logistic regression using the PROC GLIMMIX and continuous variables by ANOVA using PROC GLM of SAS. No interaction was found between season and treatment when conception rate, pregnancy loss, interval between inseminations, interval from calving to conception and pregnancy rate 150 post-partum were analysed. The results indicate no differences on conception rate among both experimental groups after AI (first, second and third). However, the interval from calving to first and second AI and interval from calving to conception were lower on FTAI-G. No difference on pregnancy rate 150 days post-partum was found among groups. Pregnancy loss after first AI was greater on FTAI-G. The interval from calving to first AI, from calving to second AI and the interval from calving to conception were shorter on FTAI-G. However, the interval between first and second AI was longer on FTAI-G. There was no difference on pregnancy rate 150 days post-partum among treatments. Also, the service rate (SR) 21 days after the voluntary waiting period (VWP) was greater on FTAI-G compared to Control-G. Conversely, the SR was lower between 21 and 42 days after the VWP on FTAI-G. No difference was found in serum concentration of P4 among treatment groups and season. Thus, the use of FTAI 60 days post-partum was efficient to anticipate the conception of high-producing dairy cattle by reducing the interval from calving to conception, but did not increase the pregnancy rate 150 days post-partum

Several studies suggest that the administration of GnRH near the time of insemination improves pregnancy rates in cattle. It has also been reported that there is greater improvement in repeat-breeder animals than at first service. The mechanism for this observation has not been established. Twenty-eight lactating Holstein cows that returned to estrus after one or more inseminations from the usu caine Dairy were used in the study. Anilrals were rarxiomly divide:i into tW'O treatment groups, intrarmJscular administration of 100 ug GnRH or saline oontrol at the tirre of insemination. Blood samples were collected at o, 1, 1.5, 2, 2.5, 3 and 4 hours post-insemination for LH determination and on days 0 through 7, 10, 16 and 22 for progesterone determination. Pregnancy status was detennined by rectal palpation 40 to 47 days post insemination. serum IR concentrations reached peak concentrations (9.33 ± 5.5 ng/ml) by one hour following GnRH administration. This was significantly different from saline controls (p Serum progesterone levels increased as expected. from day o to day 16 in all animals. Animals treated with GnRH that became pregnant tended to have the highest progesterone levels beginning from day 4. Animals treated with GnRH that were non-pregnant at 40 to 47 days tended to have the lowest progesterone levels from days 4 through 10 but were high on day 16. Pregnant animals had higher progesterone levels than non-pregnant animals from days 4 to 16. These differences approached significance (0.25 > p < 0.10). These results support the contention that GnRH administration affects progesterone levels rut do not conclusively establish increased early progesterone levels as the mechanism for improved pregnancy rates. Other hormonal andl functional factors may be involved.

This study was conducted to evaluate the effect of microbial feed additives Megasphaera elsdenii NCIMB 41125 and Saccharomyces cerevisiae 1026, individually and combined on rumen pH,ammonia-N and volatile fatty acids (VFAs) fermentation. An in vitro batch fermentation was conducted using rumen fluid from two early lactating Holstein cow donor fed the TMR for lactating cows which was evaluated under two diets, differing in concentrate to forage ratio. The diets were high concentrate, a 60:40 concentrate to forage ratio diet (HC) and low concentrate, a 40:60 (LC) concentrate to forage ratio diet. The treatments were; Control (diet with no additives), Me (diet with M. elsdenii NCIMB 41125 10mm (108 CFU/ml)), LY (diet with live yeast, S. cerevisiae 1026), and Me+LY (diet with mixture of M. elsdenii and S. cerevisiae). The average rumen pH was 5.8 and ammonia nitrogen was not affected by Me and LY supplemented separately or in combination (Me+LY) in both low and high concentrate diets. Total VFAs were increased with the addition of LY alone and in combination Me+LY+Me) in high concentrate diet only but the addition of Me had no effect in both diets. Acetate, lactate and A: Pr were decreased (P<0.05) by all the treatments (Me and LY alone and in combination) on both diets, except in high concentrate diet where the addition of Me tended to decrease (P<0.07) acetate and had no effect on lactate. Propionate was increased by all the treatments in low concentrate diet and tended toincrease (P<0.08) by addition of Me and Me+LY in high concentrate diet. In a low concentrate diet, butyrate was increased by LY but tended to be decreased by Me, however, all the treatments lacked effects on high concentrate diet. Live yeast appears to act differently compared to Me by showing two times more effects on high than low concentrate diets.This in vitro study showed that both Me and LY had a tendency to modify rumen fermentation and that might indicate their potential to mitigate the metabolic challenges and improve energy status of Holstein dairy cows during the transition and early lactation period. However, there is a need for further research that will include in vivo study. / Agriculture, Animal Health and Human Ecology / M.Sc. (Agriculture)

Made available in DSpace on 2015-03-26T13:46:56Z (GMT). No. of bitstreams: 1 texto completo.pdf: 308082 bytes, checksum: e30aa6dee1e9497438ca76f699ba5715 (MD5) Previous issue date: 2011-03-11 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective was to estimate the urinary excretion of purine from the TDN consumption and determine the endogenous contribution in dairy cows. The experiment was conducted at the Unidade de Ensino, Pesquisa e Extensão em Gado de Leite (UEPE-GL) during the month of March 2010. Twelve Holstein cows purebred and crossbred, allocated in a completely randomized design with three treatments based on production of milk, which were assessed as high, medium and low bands by taking the following production: 33,50; 18,42 and 11.07 kg of milk / day, respectively.The diet consisted of corn silage ad libitum and concentrate fed at a rate of one kilogram for every three pounds of milk produced. The experimental period lasted 15 days, se ven to eight days for adaptation and implementation of collection of urine, faeces, blood and milk, as well as to evaluate the consumption and digestibility. Milkings were carried out in two hours, from 6:00 h and 16:00 h. The results were evaluated by analysis of variance, using the 5% level of probability of type I error, through the SAS, by using the t test to compare means. Relations between the daily excretion of purine derivatives and the consumption of total digestible nutrients (TDNI), digestible organic matter intake (DOMI) and dry matter intake (DMI) were assessed using linear regression. No significant differences (P>0.05) for lactose and milk fat, however, the percentage of protein was higher for cows with low production (P<0.05). Intakes of all nutrients, except for neutral detergent fiber corrected for ash and protein (NDF) and neutral detergent fiber indigestible (NDFi) were higher for animals for higher production. The digestibility of dry matter (DM), organic matter (OM), crude protein, and non-fiber carbohydrates and contents of total digestible nutrients (TDN) did not differ between treatments (P> 0.05), whereas the digestibility of ether extract and NDF were influenced by the level of milk production, and lower for cows of high production. The levels of urea nitrogen in plasma and milk and excretion of nitrogenous (N) in urine were highly correlated and higher (P<0.05) for more productive animals, indicating that the concentration varied with the level of milk production. Urinary excretions of purine derivatives (PD) and urea, as well as the relations of allantoin: creatinine, uric acid, creatinine, purine derivatives, creatine and urea, creatinine, when compared between different times of collection and spot urine collection total urine for 24 hours, no significant difference (P>0.05). The synthesis of ruminal microbial crude protein and excretion of PD were associated with intake of TDN and digestible organic matter (DOM), being raised from 23.48 mmol of SD for each kg of TDN consumed, 25.50 mmol SD for each kg of digestible organic matter, revealing that both relations can be used to make these estimates. The gathering spot can be used to estimate the daily excretion of purine derivatives and urea in the urine of cows, regardless of the level of production. Both the use of TDN intake and consumption of MOD can be used in order to estimate the urinary purine derivatives. Whereas the excretion of PD in mmol/kgPC0,75 and dry matter intake expressed as g/kg PC0,75, obtained the value of the fraction of endogenous DP mmol/kgPC0.2370,75. / Objetivou-se estimar a excreção urinária de derivados de purinas a partir do consumo NDT e determinar a contribuição endógena em vacas de leite. O experimento foi realizado na unidade de ensino, pesquisa e extensão em gado de leite (UEPE-GL) durante o mês de março de 2010. Utilizaram-se doze vacas da raça Holandesa, puras e mestiças, alocadas em delineamento inteiramente casualizado, com três tratamentos em função da produção de leite, que foram determinadas como Alta, Média e Baixa seguindo as seguintes faixas de produção: 33,50, 18,42 e 11,07 kg de leite/dia, respectivamente. A dieta foi constituída de silagem de milho à vontade e concentrado fornecido na proporção de um kg para cada três kg de leite produzido. O período experimental teve duração de 15 dias, sendo sete para adaptação e oito dias para realização das coletas de urina, fezes, sangue e leite, bem como para avaliação do consumo e digestibilidade aparente. As ordenhas foram realizadas em dois horários, às 6:00 h e 16:00 h. Os resultados foram avaliados por meio de análises de variância, utilizando-se nível de 5% de probabilidade para o erro tipo I, por intermédio do programa SAS, sendo utilizado o teste de T para comparação de médias. As relações entre as excreções diárias dos derivados de purinas e os consumos de nutrientes digestiveis totais (CNDT), de matéria orgânica digestível (CMOD) e de matéria seca (CMS) foram avaliadas através do modelo de regressão linear simples. Não houve diferença (P>0,05) para os teores de lactose e gordura do leite, porém, o percentual de proteína foi superior para vacas de baixa produção (P<0,05). Os consumos de todos os nutrientes, exceto o de fibra insolúvel em detergente neutro corrigida para cinzas e proteína (FDNcp) e fibra insolúvel em detergente neutro indigestível (FDNi), foram maiores para os animais de maior produção. As digestibilidades da matéria seca (MS), matéria orgânica (MO), proteína bruta, e carboidratos não fibrosos e os teores de nutrientes digestíveis totais (NDT) não diferiram entre os tratamentos (P>0,05), enquanto que as digestibilidades do extrato etéreo e da FDNcp, foram influenciadas pelo nível de produção de leite, sendo menores para vacas de Alta produção. Os teores de nitrogênio uréico no plasma e no leite e a excreção de compostos nitrogenados (N) na urina foram altamente correlacionados e superiores (P<0,05) para animais mais produtivos, indicando que a concentração variou com o nível de produção de leite. As excreções urinárias dos derivados de purinas (DP) e uréia, bem como as relações de alantoina:creatinina, ácido úrico:creatinina, derivados de purina:creatina e uréia:creatinina, quando comparadas entre os diferentes tempos de coleta spot de urina e coleta total de urina durante 24 horas, não apresentaram diferença significativa (P>0,05). A síntese ruminal de proteína bruta microbiana e a excreção de DP foram relacionadas com o consumo de NDT e de matéria orgânica digestível (MOD), sendo obtidos 23,48 mmol de DP para cada kg de NDT consumido e 25,50 mmol de DP para cada kg de MO digestível, sendo possível observar que ambas as relações podem ser utilizadas para realizar estas estimativas. A coleta spot pode ser utilizada para estimar a excreção diária de derivados de purinas e de uréia na urina em vacas, independentemente do nível de produção. Tanto a utilização do consumo de NDT quanto de MOD podem ser utilizados com o intuito de estimar os derivados de purinas urinários. Considerando a excreção de DP em mmol/kgPC0,75 e o consumo de matéria seca expresso em g/kg PC0,75, obteve-se o valor da fração endógena de DP de 0,237 mmol/kgPC0,75.

The purpose of this thesis was to analyse mortality in calf rearing.I found out that the most important causes of the calf mortality are: course of calving, order of calving, seasonal character and climatic conditions.The casualties in calf rearing were about 24 %. Economic loss which was evoked by calf death affected trading income in whole cattle breeding. The main aim of the both farms is to achieve high level in calf rearing which essentially decides about profitability and efficiency of cattle breeding.

Galactopoietic effects of somatotropin are the result of IGF-I and require high-quality nutrient intake. This study investigated short-term partitioning effects during recombinant bovine somatotropin (bST) administration in high yielding early lactation dairy cows. Administration of recombinant bST has been shown generally to alter results of metabolic tests in the face of unchanged basal glucose and insulin concentrations. Ten multiparous Holstein cows were subjected to rbST (Lactotropin®) and/or feed intake restriction to 80% of predicted ME requirement (80% ME). Responses to insulin challenge (0.1 IU porcine insulin/kg BW. 210 min) and hyperglycaemic clamp (+50 mg/dL whole blood, 120 min) were tested during weeks 8 (control), 9 (rbST ), 11 (80% ME) and 12 (rbST + 80% ME) postpartum. Plasma and whole blood samples were assayed for glucose concentrations. The rbST treatment decreased fasting whole-blood glucose concentration by 9.4% (P<0.0001), which was likely a remnant of control hyperglycaemia. Maximum glucose response was 4.0 mg/dL (21.7%) lower (P<0.0038) and took 6.5 minutes longer to attain (P<0.0037). Steady-state glucose infusion rate (SSGIR) decreased by 8.1 % (P<0.0001). The 80% ME treatment decreased glucose availability by 5 to 6% (P<0.0100), while no glucose responses were affected. Restricted energy intake during treatment with rbST resulted in plasma glucose increase by 5.5% (P<0.0001). Peripheral uptake and utilization of glucose increased by 5.1 % (P<0.0005). Compared to energy restriction, 80%ME + rbST did not alter effects of nutrient restriction on responses to exogenous insulin challenge. Effects were small and inconsistent. SSGIR decreased by 5.0% in the 80% ME + rbST compared to the 80% ME period (P<0.0004) and the change in the hyperglycaemic clamp in the absence of an effect in the insulin challenge may be due to differences in endogenous insulin secretion. The conclusion was that rbST treatment resulted in altered glucose metabolic responses, even with restricted energy intake. / Dissertation (MSc(Agric))--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Profitable milk production and genetic improvement in dairy herds are largely dependant on fertile cows capable of calving down on an annual basis. Several studies indicate declines in the reproductive performance of Holstein cows over the last 30 years. Calving interval (CI) and services per conception (SPC) are being used by dairy farmers as indicators of the reproductive performance of dairy cows. However, using these traits as cow fertility indicators is problematic as CI is dependent on subsequent calving dates while SPC is strongly linked to inseminator proficiency. The aim of the study is therefore, firstly, to describe alternative fertility traits derived from insemination and calving dates and pregnancy check results. The effects of some non-genetic factors on these traits are discussed. Means±sd for interval traits from calving to first insemination (CFS) and the interval from calving to conception (DO) were respectively 77±30 and 134±74 days while the number of services per conception (SPC) averaged 2.55±1.79. The percentage of first servics occurring within 80 days post-partum (FS80d) and the proportion of cows being confirmed pregnant within 100 (PD100d) and 200 days post-partum (PD200d) were 0.64±0.48, 0.36±0.48 and 0.71±0.45, respectively. Although fertility traits were affected significantly by lactation number, calving year and month, herds (managers) had the largest effect. Fertility is a complex trait, however, the challenge is finding traits that best describe this trait. Genetic parameters for these traits could give an indication of the response to selection in dairy herds. In the second part of this study, genetic parameters and correlations between fertility traits, sourced from standard reproduction management data bases, are analysed for Holstein cows using bivariate linearlinear and linear-threshold animal models. Insemination events (n = 69 181) from 26 645 lactations of 9 046 Holstein cows from 14 herds, calving down during the period from 1991 to 2007, were available. The outcome of each AI event was known. Insemination records were linked to the calving date of each cow, lactation number as well as dam and sire identification. Fertility traits indicating the ability of cows to show heat early in the breeding period, and to become pregnant, were derived. Data were analysed using bivariate linear-linear and linear-threshold animal models with fixed effects being herd (14 levels), year (17 levels), season (4 levels) and lactation number (6 levels). The model included the random effects of animal and animal permanent environment (PE). Heritability estimates ranged from 0.04±0.01 to 0.10±0.02 for FS80d, from 0.07±0.01 to 0.08±0.02 for PD100d and from 0.06±0.04 to 0.08±0.02 for PD200d depending on the two-trait combination. Although heritability estimates of most fertility traits were below 0.10, they were in close agreement with results published by other researchers using linear models. Genetic correlations between different fertility parameters analyzed in this study indicated that it is unlikely that a single characteristic would serve well for selection purposes; instead, combining different traits could be used in selection programmes to improve fertility. Further research in constructing an optimal fertility index is warranted. In the third part of this study, genetic parameters for South African Holstein cows for fertility and production traits were estimated from 2415 lactation records. Two-trait analysis of fertility and milk yield was investigated as a method to estimate fertility breeding values when culling, or selection based on milk yield in early lactation, determines presence or absence of fertility observations in later lactations. Fertility traits were days from calving to first service (CFS), days from calving to conception (DO), percentage cows inseminated within 80d post-partum (FS80d), number of service per conception (SPC), and the binary traits percentage of cows pregnant within 100d and 200d postpartum (PD100d, Pd200d). Milk production traits were 300 day milk, fat and protein yield. For fertility traits, range of estimates of heritability (h2) was 0.006 to 0.08 for linear traits and 0.05 to 0.12 for binary traits. The range for permanent environmental variance (c2) was 0.016 to 0.032. In this study genetic correlations of fertility with milk production traits were unfavourable ranging between −0.93 to 0.76. / AFRIKAANSE OPSOMMING: Winsgewende melkproduksie en genetiese verbetering in melkkuddes hang grootliks af van vrugbare koeie wat op ‘n jaarlikse basis kalf. Verskeie studies toon dat die reproduksievermoë van Holsteinkoeie oor die afgelope 30 jaar afgeneem het. Melkboere gebruik tussenkalfperiode (TKP) en aantal inseminasies per konsepsie (KIPK) as aanduidings van die reproduksievermoë van melkkoeie. Dit is egter moeilik om hierdie eienskappe as vrugbaarheidseienskappe vir melkkoeie te gebruik omdat TKP afhanklik is van opeenvolgende kalfdatums terwyl KIPK baie sterk gekoppel is aan die inseminasievermoë van die insemineerders. In die eerste gedeelte van die studie word alternatiewe vrugbaarheidseienskappe, wat afgelei is van inseminasie- en kalfdatums en die uitslag van dragtigheidsondersoeke, beskryf. Die invloed van ‘n aantal nie-genetiese faktore op dié eienskappe word ook bespreek. Gemiddeldes±standaard afwykings vir die periode vanaf kalwing tot eerste inseminasie (CFS), die periode van kalwing tot konsepsie (DO) was 77±30 en 134±74 dae onderskeidelik, terwyl die aantal inseminasies per konsepsie (SPC) 2.55±1.79 was. Die persentasie eerste inseminasies wat binne 80 dae na kalwing (FS80d), en die persentasie koeie wat dragtig bevestig is binne 100 (PD100d) en 200 dae na kalwing (PD200d) was 0.64±0.48, 0.36±0.48 en 0.71±0.45, onderskeidelik. Hoewel vrugbaarheidseienskappe betekenisvol beïnvloed is deur laktasienommer, jaar en seisoen van kalwing, het kuddes (bestuurders) die grootste effek op eienskappe gehad. Vrugbaarheid is ‘n ingewikkelde eienskap en die uitdaging is om eienskappe te vind wat dit die beste beskryf. Genetiese parameters vir eienskappe wat oorweeg word sal ‘n aanduiding gee van die seleksieresponse in melkkuddes. In die tweede gedeelte van die studie is genetiese parameters van vrugbaarheidseienskappe en korrelasies tussen dié eienskappe beraam. Eienskappe is bekom vanaf reproduksiebestuursprogramme wat in melkkuddes gebruik word. Al die inseminasierekords (n = 69 181) van 26 645 laktasies van 9 046 Holsteinkoeie van 14 melkkuddes wat tussen 1991 en 2007 gekalf het, was beskikbaar. Die uitslag van elke inseminasie was bekend. Inseminasierekords is met die kalfdatum, laktasienommer, identifkasienommers van die moeder en vader van elke koei, gekoppel. Vrugbaarheidseienskappe wat die vermoë van koeie aandui om vroeg na kalwing op hitte te kom en beset te raak, is verkry. Die data is ontleed deur gebruik te maak van twee-eienskap liniêreliniêr- en liniêr-drempel-diere modelle met vaste effekte kudde (14 vlakke), jaar (17 vlakke), siesoen (4 vlakke) en laktasienommer (6 vlakke). Die modelle het die ewekansige effekte van dier- en dierpermananente omgewingseffkte (PE) ingesluit. Genetiese, diere PE en residuele korrelasies is vervolgens beraam. Oorerflikhede varieer vanaf 0.04±0.01 tot 0.10±0.02 vir FS80d, vanaf 0.07±0.01 tot 0.08±0.02 vir PD100d en vanaf 0.06±0.04 tot 0.08±0.02 vir PD200d, afhangende van die tweeeienskap kombinasie. Ten spyte daarvan dat die oorerflikhede van die meeste vrugbaarseienskappe laer as 0.10 is, is die resultate in ooreenstemming met ander navorsers wat liniëre modelle gebruik het. Genetiese korrelasies tussen verskillende vrugbaarheidseienskappe toon dat daar nie enkel beste eienskap is wat vir seleksiedoeleindes gebruik kan word nie. Dit sou waarskynlik beter wees om verskillende eienskappe te kombineer om die vrugbaarheid in melkkoeie te verbeter. Verdere navorsing is nodig om ‘n optimale vrugbaarheidseienskap te ontwikkel. Dit is belangrik dat die verband tussen reproduksie en melkproduksie vir melkkoeie bepaal word. In die derde gedeelte van die studie is genetiese parameters vir vrugbaarheid- en melkproduksieeienskappe vir Suid Afrikaanse Holsteinkoeie beraam. ‘n Totaal van 2415 laktasierekords was beskikbaar. Vrugbaarheid en melkproduksie is volgens ‘n twee-eienskap analise ontleed as ‘n metode om teelwaardes vir vrugbaarheid te bepaal in gevalle waar die uitskot of seleksie gebaseer op melkproduksie in vroeglaktasie die teenwoordigheid of afwesigheid van vrugbaarheidseienskappe in latere laktasies bepaal. Vrugbaarheidseienskappe was die periode (aantal dae) tussen kalfdatum en eerste inseminasie (CFS), die aantal dae van kalf tot konsepsie (DO), die persentasie koeie wat by 80 dae na kalf vir die eerste keer geïnsemineer was (FS80d), die aantal inseminasies per konsepsie (SPC), en binêre eienskappe van die persentasie koeie wat by 100 dae en 200 dae na kalf beset was (PD100d en PD200d). Melkproduksie-eienskappe was 300-dae melk., vet- en proteïnproduksie. Vir vrugbaarheidseienskappe het die oorerflikheidswaardes (h2) vanaf 0.006 tot 0.08 vir liniêre eienskappe gevarieer en tussen 0.05 tot 0.12 vir binêre eienskappe. Die permanente omgewingsvariansie (c2) het tussen 0.016 tot 0.032 gevarieer. In hierdie studie was die genetiese korrelasies tussen vrugbaarheidseienskappe en melkproduksie-eienskappe ongunstig en het dit tussen −0.93 tot 0.76 gevarieer.

A presente tese foi dividida em 5 Experimentos. Os objetivos do Experimento 1 foram avaliar a utilização da gonadotrofina coriônica equina (eCG) e/ou do cipionato de estradiol (ECP) na dinâmica folicular e taxa de concepção de vacas holandesas submetidas a inseminação em tempo fixo (IATF). No D0, todos os animais (n = 782) receberam 2 mg de benzoato de estradiol (BE) e um dispositivo intravaginal de progesterona (CIDR). Oito dias depois, o CIDR foi retirado e todos os animais receberam PGF2?. Simultaneamente, os animais foram divididos em 4 grupos: G1) eCG + ECP no Dia 8; G2) eCG no Dia 8 + GnRH após 48h; G3) ECP no Dia 8; G4) GnRH após 48h. Amostras de sangue e exames utlra-sonográficos foram realizados frequentemente em um subgrupo de animais (n = 96). As análises estatísticas de todos os experimentos foram efetuadas com o proc GLIMMIX e proc MIXED do SAS. O uso de eCG e o escore de condição corporal (ECC) dos animais afetaram as concentrações circulantes de progesterona no diestro. Os animais do G2 apresentaram maior taxa de concepção que os do G4 (33,8% vs. 28,9%). Além disso, para animais de menor ECC, ficou evidente o benefício da aplicação de eCG (G2 = 44,4% vs. G4 = 6,1%). No Experimento 2 (n = 26), o objetivo foi comparar o efeito da administração da eCG no dia da remoção do CIDR em animais de menor (2,0-2,5) ou maior (3,0-3,5) ECC. Foram avaliadas algumas características do corpo lúteo (CL) como o volume e histologia, assim como as concentrações plasmáticas de progesterona no diestro. Independentemente da condição corporal dos animais, a eCG aumentou o volume do CL e a concentração plasmática de progesterona no diestro. O ECC afetou negativamente o volume e concentração de progesterona sérica no diestro. Não foi encontrado diferença na proporção de células grandes/pequenas, assim como no fluxo sanguíneo no CL entre os grupos experimentais. No Experimento 3, foi comparado a taxa de concepção em vacas de leite de alta produção (n = 388) após o uso do protocolo G2 do Experimento 1 (Capítulo I), com ou sem adição de ECP no momento da retirada do CIDR (novo ou usado). Não foi verificado efeito da adição do tratamento com ECP e nem do tipo do dispostivo na taxa de concepção. No Experimento 4 (n = 199), apesar no aumento verificado no diâmetro folicular no grupo tratado com GnRH 56h (17,8 mm) comparado com GnRH 48h (16,5 mm); e do atraso no momento da ovulação após a retirada do CIDR (GnRH 56h = 75,3h; GnRH 48h = 79,8h) não foi constatado qualquer diferença na concepção ao se atrasar a aplicação do GnRH de 48h para 56h em vacas inseminadas 16h depois do GnRH. No Experimento 5 (n = 185), a taxa de concepção não diferiu em animais que receberam o GnRH 48h ou 56h (momento da IATF) após a retirada do CIDR, indicando a possibilidade do emprego de um protocolo com apenas 3 manejos em vacas de leite de alta produção. / The current thesys has been divided in 5 Experiments. Objectives of Experiment 1 were to evaluate the effects of equine chorionic gonadotropin (eCG) and/or estradiol cypionate (ECP) on follicular dymanics and conception rate in Holstein cows receiving fixed timed artificial insemination (TAI). On D0, all cows (n = 782) received 2 mg of estradiol benzoate (EB) and one intravaginal progesterone device (CIDR). Eight days later, CIDR was removed and all animals were treated with PGF2?. Simultaneously, animals were divided in 4 groups: G1) eCG + ECP on Day 8; G2) eCG on Day 8 + GnRH 48h later; G3) ECP on Day 8; G4) GnRH 48h later. Blood samples and ultrasound exams were frequently performed in a subset of the animals (n = 96). All the statistical analyses for all experiments were performed with proc GLIMMIX and proc MIXED of SAS. Equine chorionic gonadotropin (eCG) treatment and body condition score (BCS) affected circulating progesterone in the diestrus. Cows in G2 had greater conception rates than cows in G4 (33,8% vs. 28,9%). In addition, in cows with lower BCS, eCG seems to be even more affective (G2 = 44,4% vs. G4 = 6,1%). In Experiment 2 (n = 26), the objective was to compare the effect of eCG the day of CIDR removal in animals with lower (2,0-2,5) or higher (3,0-3,5) BCS. Some variables such as corpus luteum (CL) volume, histology and circulating progesterone concentration in the diestrus were evaluated. Regardless of the body condition of the animals, eCG increased CL volume and circulating progesterone concentration in the diestrus. BCS negatively affected CL volume and circulating progesterone. There were no differences in large/small CL cell ratio, as well as CL blood flow between experimental groups. In Experiment 3, it was compared conception rate in dairy cows (n = 388) after using the same protocol G2 from Experiment 1 (Chapter I), with or without an ECP treatment at the time of CIDR (new or used) removal. Both ECP treatment and type of CIDR did not significantly affected conception rates. In Experiment 4 (n = 199), despite the fact that follicular diameter was increased in group GnRH 56h (17,8 mm) compared with GnRH 48h (16,5 mm); and of the delayed time of ovulation after CIDR removal (GnRH 56h = 75,3h; GnRH 48h = 79,8h), there were no differences in conception rates after delaying the GnRH treatment from 48h to 56h in cows inseminated 16h after GnRH. In Experiment 5 (n = 185), conception rate did not differ in animals that received GnRH 48h or 56h (at the time of TAI) after CIDR removal, indicating the possibility of using a protocol with only 3 handlings in high producing dairy cows.