In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Different factors contribute to this situation; the most important are a consequence of increased temperature and humidity that result in a decreased expression of overt estrus and a reduction in appetite and dry matter intake. Heat stress reduces the degree of dominance of the selected follicle and this can be seen as reduced steroidogenic capacity of its theca and granulosa cells and a fall in blood estradiol concentrations. Plasma progesterone levels can be increased or decreased depending on whether the heat stress is acute or chronic, and on the metabolic state of the animal. These endocrine changes reduce follicular activity and alter the ovulatory mechanism, leading to a decrease in oocyte and embryo quality. The uterine environment is also modified, reducing the likelihood of embryo implantation. Appetite and dry matter intake are both reduced by heat stress thus prolonging the postpartum period of negative energy balance and increasing the calving-conception interval, particularly in high producing dairy cows. The utilization of cooling systems may have a beneficial effect on fertility but dairy cows cooled in this way are still unable to match the fertility achieved in winter. Recent studies suggest that the use of gonadotropins to induce follicular development and ovulation can decrease the severity of seasonal postpartum infertility in dairy cows. © 2003 Elsevier Science Inc. All rights reserved.

Heat stress and seasonal effects on reproduction in the dairy cow-a review. Theriogenology, 60: 1139-1151 / DE RENSIS, Fabio; Scaramuzzi, Jr. - In: THERIOGENOLOGY. - ISSN 0093-691X. - 60:(2003), pp. 1139-1151. [10.1016/S0093-691X(03)00126-2]

Heat stress and seasonal effects on reproduction in the dairy cow-a review. Theriogenology, 60: 1139-1151.

DE RENSIS, Fabio
;
2003-01-01

Abstract

In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Different factors contribute to this situation; the most important are a consequence of increased temperature and humidity that result in a decreased expression of overt estrus and a reduction in appetite and dry matter intake. Heat stress reduces the degree of dominance of the selected follicle and this can be seen as reduced steroidogenic capacity of its theca and granulosa cells and a fall in blood estradiol concentrations. Plasma progesterone levels can be increased or decreased depending on whether the heat stress is acute or chronic, and on the metabolic state of the animal. These endocrine changes reduce follicular activity and alter the ovulatory mechanism, leading to a decrease in oocyte and embryo quality. The uterine environment is also modified, reducing the likelihood of embryo implantation. Appetite and dry matter intake are both reduced by heat stress thus prolonging the postpartum period of negative energy balance and increasing the calving-conception interval, particularly in high producing dairy cows. The utilization of cooling systems may have a beneficial effect on fertility but dairy cows cooled in this way are still unable to match the fertility achieved in winter. Recent studies suggest that the use of gonadotropins to induce follicular development and ovulation can decrease the severity of seasonal postpartum infertility in dairy cows. © 2003 Elsevier Science Inc. All rights reserved.
2003
Heat stress and seasonal effects on reproduction in the dairy cow-a review. Theriogenology, 60: 1139-1151 / DE RENSIS, Fabio; Scaramuzzi, Jr. - In: THERIOGENOLOGY. - ISSN 0093-691X. - 60:(2003), pp. 1139-1151. [10.1016/S0093-691X(03)00126-2]
File in questo prodotto:
File Dimensione Formato  
De Rensis Heat stress.pdf

non disponibili

Tipologia: Documento in Post-print
Licenza: Creative commons
Dimensione 289.22 kB
Formato Adobe PDF
289.22 kB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/1629624
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 547
  • ???jsp.display-item.citation.isi??? 447
social impact