Resumo
We evaluated the association of monthly milk urea N (MUN) concentrations before conception and days open in high-producing dairy cows from commercial herds in Southern Brazil. Other herd traits were also investigated regarding their relationship with days open. A database containing 16,569 monthly test-day records (obtained from 3,926 lactations of 2,145 cows) for productive, reproductive, and milk quality data was assembled from three different herds. Maximum MUN before conception was divided into quartiles as follows: ≤15.5 mg/dL (1), from 15.6 mg/dL to 18.0 mg/dL (2), from 18.1 to 20.5 mg/dL (3), and >20.5 mg/dL (4). When cows calved in spring and winter, days open averaged (mean±SE) 171.2±2.71 and 155.4±2.31, corresponding to an increase in 12 and 2%, respectively, related to cows that calved in summer (152.7±2.44). When cows calved in fall, a 12% reduction in days open (135.5±1.79) compared with cows that calved in summer was observed. The estimated regression coefficients showed that multiparous cows are expected to have an increase of 12 and 6% in days open when compared with primiparous and secondiparous cows, respectively. Days open were positively associated with the highest MUN value obtained until conception. Cows in the highest quartile of maximum MUN (>20.5 mg/dL) had more days open (184.6±2.93) than cows in quartiles 1, 2, and 3 (123.7±2.12, 150.2±2.16, and 160.5±2.29, respectively), which represents reductions of 40, 21, and 14%, respectively. These results suggest that a maximum MUN concentration before conception higher than 15.5 mg/dL may negatively impact the fertility of high-producing dairy cows.
Assuntos
Animais , Feminino , Bovinos , Luz Solar , Leite/química , Fertilização/fisiologia , Amônia/análiseResumo
The present investigation aimed to evaluate the population structure and inbreeding of Holstein herds in southern Brazil. To carry out the analysis, the Associação Paranaense de Criadores de Bovinos da Raça Holandesa (APCBRH) in Brazil provided the data, which consisted of a pedigree file of 206,796 animals born between 1970 and 2014. Results regarding the following parameters were determined: pedigree integrity, effective number of founders, effective number of ancestors, generation interval, inbreeding coefficient, realized effective population size, and average relatedness coefficient. POPREP and ENDOG v.4.5 software packages were employed to estimate these parameters. Based on the data set, the mean generation interval was found to be 6.3 years, and the average inbreeding coefficient, related to inbred animals, was 4.99%. Furthermore, the realized effective population size varied throughout the time period, ranging from 22 to 114, whereas the rate of inbreeding in this same period showed a decreasing trend towards the later years in the period until 2014. Upon evaluation, average relatedness coefficient was estimated to be 0.71%. Moreover, the effective number of founders and ancestors were estimated as 418 and 400 animals, respectively. According to the level of inbreeding observed, it could be noticed that genetic diversity remains elevated, which will be important to the genetic progress in the Holstein breeding program in Southern Brazil.(AU)
Assuntos
Animais , Bovinos/fisiologia , Endogamia/métodos , BrasilResumo
Objetivou-se com este trabalho avaliar o efeito da ordem de lactação e estação do ano ao parto sobre a produção e qualidade do leite de vacas da raça Holandesa. A ordem de parto teve efeito significativo sobre a produção de leite e escore de células somáticas (ECS), sem efeito sobre os teores de gordura e proteína. Vacas de 3ª e 4ª lactação foram mais produtivas devido ao completo desenvolvimento da glândula mamária e crescimento corporal. O ECS aumentou com a elevação do número de lactações devido ao contato com agentes patogênicos à medida que os animais têm uma idade mais avançada. Lactações iniciadas na primavera apresentaram a menor produção de leite (Kg/vaca/dia) por causa do estresse calórico que os animais sofreram no pico de lactação, de modo a comprometer a produção de leite dessa lactação. ECS e teores de gordura e proteína não variaram em função da época de parição. Ordem de lactação e estação do ano ao parto causam variação na produção de leite, e é importante o uso de estratégias para minimizar o estresse calórico, principalmente no pico de lactação. Maiores cuidados devem ser tomados com vacas a partir da 4ª lactação, pois apresentam maior ECS e o estresse calórico pode favorecer a ocorrência de mastite. (AU)
It was aimed to evaluate the effect of the lactation order and calving season on milk production and quality of Holsteins cows. The lactation order had a significant effect on milk production and score of somatic cells (SSC), without affecting fat and protein content. Cows of 3rd and 4th lactation were more productive due to the complete development of the mammary gland and corporal growth. SSC rose with the increase of the lactation number due to the contact with pathological agents as the animals had a more advanced age. Lactations that begin in the spring presented the smallest milk production (Kg/cow/day) because of the heat stress that these animals suffered in the lactation pick, with damage of milk production of this lactation. SSC, the fat and protein content did not vary in function of the calving season. Lactation order and calving season caused variation in the milk production, being important the use of strategies to minimize the heat stress mainly in the lactation pick. Larger careful should be taken with cows starting from 4th lactation, because these present a higher SSC, and the heat stress can favor the mastitis occurrence.(AU)
Assuntos
Animais , Fenômenos Fisiológicos da Nutrição Animal/fisiologiaResumo
Objetivou-se com este trabalho avaliar o efeito da ordem de lactação e estação do ano ao parto sobre a produção e qualidade do leite de vacas da raça Holandesa. A ordem de parto teve efeito significativo sobre a produção de leite e escore de células somáticas (ECS), sem efeito sobre os teores de gordura e proteína. Vacas de 3ª e 4ª lactação foram mais produtivas devido ao completo desenvolvimento da glândula mamária e crescimento corporal. O ECS aumentou com a elevação do número de lactações devido ao contato com agentes patogênicos à medida que os animais têm uma idade mais avançada. Lactações iniciadas na primavera apresentaram a menor produção de leite (Kg/vaca/dia) por causa do estresse calórico que os animais sofreram no pico de lactação, de modo a comprometer a produção de leite dessa lactação. ECS e teores de gordura e proteína não variaram em função da época de parição. Ordem de lactação e estação do ano ao parto causam variação na produção de leite, e é importante o uso de estratégias para minimizar o estresse calórico, principalmente no pico de lactação. Maiores cuidados devem ser tomados com vacas a partir da 4ª lactação, pois apresentam maior ECS e o estresse calórico pode favorecer a ocorrência de mastite.
It was aimed to evaluate the effect of the lactation order and calving season on milk production and quality of Holsteins cows. The lactation order had a significant effect on milk production and score of somatic cells (SSC), without affecting fat and protein content. Cows of 3rd and 4th lactation were more productive due to the complete development of the mammary gland and corporal growth. SSC rose with the increase of the lactation number due to the contact with pathological agents as the animals had a more advanced age. Lactations that begin in the spring presented the smallest milk production (Kg/cow/day) because of the heat stress that these animals suffered in the lactation pick, with damage of milk production of this lactation. SSC, the fat and protein content did not vary in function of the calving season. Lactation order and calving season caused variation in the milk production, being important the use of strategies to minimize the heat stress mainly in the lactation pick. Larger careful should be taken with cows starting from 4th lactation, because these present a higher SSC, and the heat stress can favor the mastitis occurrence.