Photoperiod management in dairy herd

Abstract

Photoperiod management deals with manipulation of light and dark exposure to the animals during 24
hours duration. Shifting of cow from short day (8 hrs. of light) photoperiod (SDPP) to long day (16 - 18
hrs. of light) photoperiod (LDPP) improved performance of dairy animals. Light stimulates photoreceptor
cells of retina which subsequently relay inhibitory signal to pineal gland for melatonin secretion via retino
hypothalamic tract through a series of endogenous process. Melatonin secretes at night and duration of
secretion vary inversely with day length. Melatonin secretion from pineal gland further influences secretion
of number of other hormones like prolactin (PRL), gonadotropins and IGF-I. Alterations in these circulating
hormones influence growth, reproduction, lactation and immunity of dairy animals. Photo periodic response
was more with fluorescent, metal halide, high pressure sodium lighting. The recommended level of light
for the cow was 15 foot candle (162 lux) at 1m (3’) height from the stall floor. The 30 (close house) and
45 foot candle (open house) produce the good effect. The separation distance between two lights should
be 1.5 times more than mounting height (14 – 35 ft) depending on type of sheds. The optimum CRI of
light for calf house was 80. The recommended illumination level for milking parlour was 50 foot candles.
Duration of exposure to photoperiod directly affects growth of calves and heifers, as well as the mammary
tissue growth in heifers. Exposure to LDPP during the growth phase results larger and leaner animals at
maturity with greater mammary parenchymal growth and these effects are associated with greater yield in
first calver. Extending photoperiod (4 hrs.) using 160 lux light during winter season resulted in better growth
rate and early onset of puberty in buffalo heifers. Proliferation of mammary cells was better in SDPP dry
cows as compared to LDPP. Cows reared on LDPP during early lactation produced more milk (8 to 10%)
than on natural photoperiod. The effect of LDPP developed gradually and significantly after 3 - 4 weeks of
exposure. However, there is no carryover effect of photoperiod on milk production. LDPP produced more
milk yield may be due to elevated level of prolactin, growth hormone and IGF-I. Dry cow on SDPP for entire
dry period produces more milk (up to 3 kg) along with protein and fat in next lactation. SDPP also increased
feed intake (more than 1 kg) and improved the immunity in advanced pregnant dry cows. Duration of day
length during autumn and winter is generally shorter, but cattle and buffaloes when exposed to LDPP
show significant improvement of reproduction. Improved reproduction in cows reared under LDPP may be
associated with increased circulating Ca, P, vitamin D and A, total protein, hemoglobin, erythrocytes and
γ-globulins. Heifers reared under SDPP had increased lymphocyte proliferation and enhanced neutrophil
function than those reared under LDPP. SDPP exposure to dry cows improves immune status, uterine and
udder health immediately during post partum period. Somatic cell counts also reduced in cows exposed
to SDPP during dry period in contrast to cows under LDPP.
Thus, proper manipulation of photoperiod improved lactating animal performance especially in terms of
milk, reproduction and health of animals.