LACTATION BIOLOGY SYMPOSIUM: Effects of photoperiod on mammary gland development and lactation1

Abstract

Photoperiod, or the daily sequence of light and dark, has dramatic effects on many physiological systems across animal species. Light patterns alter melatonin secretion profiles and, subsequently, the release profiles and circulating concentrations of several hormones that influence a variety of physiological responses. Although the impact of photoperiod on reproductive processes is perhaps the most common example, it is often the seasonal aspects of ovulation and anestrus that are considered. However, in cattle, the final phase of reproduction, that is, lactation, is significantly influenced by photoperiod. In contrast to short days (SDPP; 8 h light:16 h dark), exposure to long days (LDPP) of 16 to 18 h of light and 6 to 8 h of darkness increases milk yield 2 to 3 kg/d, regardless of the stage of lactation. There is evidence that this LDPP effect is due to increased circulating IGF-I, independent of any effect on GH concentrations. Cows that are housed under SDPP during the dry period have increased mammary growth and produce 3 to 4 kg/d more milk in the subsequent lactation compared with cows on LDPP when dry. While cows are on SDPP, circulating prolactin (PRL) diminishes but expression of PRL receptor increases in mammary, liver, and immune cells. Moreover, PRL signaling pathways within those tissues are affected by photoperiod. Further, replacement of PRL to cows on SDPP partially reverses the effects of SDPP on production in the next lactation. Thus, effects on dry cows are mediated through a PRL-dependent pathway. Before maturity, LDPP improve mammary parenchymal accumulation and lean body growth, which lead to greater yields in the first lactation. The accumulated evidence supports the concept that photoperiod manipulation can be harnessed to improve the efficiency of production across the life cycle of the dairy cow.

Melatonin Treatment at Dry‐off Improves Reproductive Performance Postpartum in High‐producing Dairy Cows under Heat Stress Conditions

“…; Dahl et al. ). In response to this, plasma prolactin concentrations decline but prolactin receptor expression increases in many tissues, including the liver, mammary gland and lymphocytes (Auchtung et al.…”

“…Photoperiod changes in cattle include low concentrations of melatonin observed under light conditions and their marked increase under conditions of darkness (Dahl et al. ). The effects of these changes on the reproductive performance of cattle seem limited (Hansen et al.…”

Epigenetics and developmental programming of welfare and production traits in farm animals

“…photoperiod), plane of nutrition and growth rate during the prepubertal period can each impinge on the development of the mammary gland in a manner that will determine milk yields during subsequent lactations (Robinson et al 1999;Dahl et al 2012). The curvilinear nature of the relationship between weight gain during the rearing period and mammary gland development is such that reductions of around 10% in milk yields have been reported, particularly in firstlactation dairy heifers that were either under-or overfed during the peripubertal period.…”

Effect of Melatonin on Casein Expression in Buffalo Mammary Epithelial Cells

“…Recent studies have shown its protective effect on viability of LPSstimulated bovine mammary epithelial cells and mastitis, and improved quality of milk by reducing somatic cells count (Shao et al, 2015;Yang et al, 2017;Yu et al, 2017). Studies have shown that administration of exogenous melatonin during long days or artificial RESEARCH ARTICLE stimulation of short days affect milk protein and casein contents in sheep and cows (Dahl et al, 2012;Molik et al, 2012). However, no reports are available regarding protein contents in buffalo.…”