No abstract

Two experiments were conducted to examine circulating concentrations of progesterone (P4) in cows with ovarian follicular cysts (OFCs) and to relate differing levels of P4 to subsequent follicular events. In experiment 1, peripheral concentrations of P4 were determined in cows diagnosed with OFCs. Nonpregnant, lactating Holstein and Jersey cows (n = 32) were diagnosed as having OFCs by rectal palpation. Ovarian follicular cysts were then examined by transrectal ultrasonography to confirm the presence of OFCs (follicle diameter, >/=17 mm; absence of luteal tissue). At confirmation, a blood sample was collected for quantification of P4. The concentration of P4 at confirmation was classified as low (<0.1 ng/ml), intermediate (0.1-1.0 ng/ml), or high (1.0-2.0 ng/ml). More OFCs were associated with intermediate (66%) than with either low (28%) or high (6%) concentrations of P4. In experiment 2, the fate of follicles (diameter, >/=10 mm) that formed in the presence of an OFC was determined and related to circulating concentrations of P4 during follicular development. Follicles (n = 59) that formed in the presence of an OFC ovulated (n = 19), formed a cyst (n = 30), or underwent normal growth and regression (NGR; n = 10). Endogenous P4 in the 7-day period during follicular development was classified as low (if P4 dropped to <0.1 ng/ml for 1 day or longer), intermediate (if P4 averaged between 0.1 and 1.0 ng/ml and never dropped to <0.1 ng/ml), or high (if P4 averaged >1.0 ng/ml and never dropped to <0.1 ng/ml). In the presence of intermediate P4, 75% of observed follicles formed cysts, compared with 10% that ovulated and 15% that experienced NGR. In the presence of low P4, 53%, 41%, and 6% of follicles ovulated, formed a follicular cyst, or experienced NGR, respectively. Thus, an association between intermediate P4 and the formation of OFCs was established.

The purpose of this study was to determine the effects of stage and the number of lactation on plasma ascorbate concentration and to establish the association between plasma ascorbate concentrations and plasma glucose, insulin, nonesterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), aspartate aminotransferase (AST), milk somatic cell count (SCC), milk yield, and body condition score (BCS) in dairy cows. Holstein cows (n = 193) from three different herds were used in this study. Animals were randomly selected, and assigned to five groups according to stage of lactation (group 1, dry cows; group 2, 1 to 28 d; group 3, 29 to 56 d; group 4, 57 to 140 d; group 5, 141 to 280 d), and the number of lactation (primiparous or multiparous). Plasma ascorbate concentration, plasma glucose concentration, serum insulin concentration, plasma NEFA concentration, plasma BHBA concentration, serum AST concentration, milk SCC, milk yield, and BCS were measured. The results of this study demonstrate that plasma ascorbate concentrations do not change in response to stage of lactation, or number of lactations. Among the several variables studied, none was found that, singly or in combinations, could explain variations in ascorbic acid concentrations.

RESUMO O objetivo do presente estudo foi o de analisar os efeitos da suplementação de propilenoglicol (PPG) para vacas no período peri-parto sobre a produção de leite, mudanças no escore de condição corporal (ECC), número de dias para o primeiro cio pós-parto, concentrações plasmáticas de bhidroxibutirato (BHBA), ácidos graxos não-esterificados (AGNE) e glicose. Vinte e três vacas da raça dias -10, -5, 0, 3, 7, 14, 21, 28, 35, 42

A mieloperoxidase (MPO) é uma enzima que desempenha papel fundamental nos mecanismos bactericidas dos mamíferos, sendo encontrada principalmente em leucócitos polimorfonucleares neutrófilos. A MPO está diretamente relacionada com os mecanismos bactericidas dependentes de 0 2 , sendo catalisadora do processo de formação de radicais altamente reativos como o ácido hipocloroso (HCLO-), a partir de Hp 2 e íons halogênios, constituindo, portanto, importante mecanismo de defesa contra microrganismos patogênicos. O ácido ascórbico apresenta efeitos estimulatórios sobre a atividade fagocitária de leucócitos, sobre a função do sistema reticuloendotelial e sobre a síntese de anticorpos, além de estimular a atividade de MPO in vitro em humanos, aumentando a produção de HCIO-. No homem, foi descrito um quadro de deficiência de MPO que leva à diminuição da capacidade bactericida dos neutrófilos contra Staphylococcus aureus e Candida albicans, e também a uma maior susceptibilidade desses indivíduos às infecções em geral. Neste trabalho foram coletadas amostras de sangue de 1 00 vacas da raça Holandesa, distribuídas em diferentes estágios de lactação e provenientes de três rebanhos comerciais. Utilizou-se o método de Kaplow, originalmente utilizado em humanos, para a avaliação da atividade MPO de neutrófilos e a técnica de HPLC ("High Performance Liquid Chromatograph") para a determinação dos níveis plasmáticos de ácido ascórbico. Os resultados da correlação entre a atividade MPO e os níveis de ácido ascórbico foram analisados através do programa "Computacional Statistical Analysis System" (SAS lnstitute Inc., 1985), mostrando associação negativa entre a atividade enzimática da MPO e o nível plasmático de ácido ascórbico in vivo. Além disto, houve efeito significativo do número de lactações sobre esta associação.

Foi objetivo deste estudo analisar os efeitos da suplementação de propilenoglicol para vacas em lactação sob a ocorrência de cetose e as suas conseqüências na: a) produção de leite; e b) variação do escore de condição de corporal e primeiro estro pósparto. Vinte e três vacas da raça Holandesa foram alocadas em dois tratamentos: 1) 300mL de propilenoglicol (grupo tratamento, 11 vacas), 2) 300 ml de água (grupo controle, 12 vacas), administrados através de beberagem no período peri-parto. Foram colhidas amostras de plasma para análise de β-hidroxibutirato e realizada a avaliação do escore de condição (ECC) corporal. A incidência de cetose subclínica foi de 9,1% e 33,5%; o primeiro estro pós-parto foi em média 40,18 e 45,17 dias no grupo tratamento e controle, respectivamente. Não houve efeito do tratamento ou tempo sobre produção de leite, embora a interação tempo tratamento foi significativa. O ECC do grupo tratamento foi maior que o do grupo controle, mas não sofreu variação nos primeiros 60 dias de lactação.

No abstract

Forty-eight primiparous and pregnant Holstein cows at 202 (+/-59) days in milk and average daily milk production (DMP) of 22 (+/-5.3) kg at the beginning of the trial were used to study the possibility of identifying animals that are more responsive to recombinant bovine somatotropin (rbST). Animals were housed in free-stall barns, milked three times a day and fed a total mixed ration. Animals were injected with one dose (500 mg each) of rbST every 21 days during a 105-day total period (five doses in all). Daily milk production was recorded to measure average apparent response (AAR) and peak of apparent response (PAR). Average apparent response was defined as the average increase in milk production, expressed as kilogram per cow per day, for days 0-18 after dosing, as compared to the average production calculated for days -1, -2, -3, 19, 20 and 21 after dosing. Peak of apparent response was calculated as the increase in milk production for each day from 0 to 18 days after dosing as compared to the average production for days -1, -2 and -3. There was a positive linear correlation (r = 0.608; p = 0.0001) between AAR for the first 21 days and AAR for the total 105-day period (AATR). A correlation coefficient was calculated between each individual PAR value and AATR. The highest correlation coefficient (r = 0.511; p = 0.0002) was observed for days 8, 9 and 10, and therefore these days were considered the best estimates for calculating AAR when DMP records are not available. Also, high somatic cells count had a negative impact on milk yield response to treatment (p = 0.0162).