Subtropical goats ovulate in response to the male effect after a prolonged treatment of artificial long days to stimulate their milk yield

Abstract

The objectives of this study were to determine (i) if in subtropical goats that gave birth during mid-December, the exposition to an artificial long-day photoperiod consisting in only 14 hr of light per day can increase the milk yield and (ii) to test whether these females can respond to the male effect at the end of the prolonged photoperiodic treatment. In experiment 1, 17 lactating goats were maintained under natural short days (control group), while another 22 goats were maintained under artificial long days (treated group) consisting in 14 hr light and 10 hr darkness starting at day 10 of lactation. The continuous exposition to an artificial long-day photoperiod produced an increase in the milk yield level during the first 110 days of lactation (time × treatment interaction; p = .01), while none of the milk components were modified due to the photoperiodic treatment (p > .05). In experiment 2, all control and treated anovulatory goats were submitted to the male effect using photostimulated males. All females showed oestrous behaviour within the first 10 days that were in contact with males (100% in both groups; p > .05). Thus, the latency to onset of oestrus did not differ between females from control (58.2 ± 3.0 hr) and treated (62 ± 4.6 hr) groups. Male exposition provoked ovulation independently if females were previously under long days or natural photoperiod (96 vs 100%, respectively; p = .79). It was concluded that exposure to 14 hr of light per day in subtropical goats that gave birth in late autumn stimulates milk yield without preventing the ovulation in response to the male effect at the end of the prolonged photoperiodic treatment.

An Extended Photoperiod Increases Milk Yield and Decreases Ovulatory Activity in Dairy Goats

“…These findings of the current study are consistent with those of others who found milk yield was increased by LDDP in goats [ 3 , 6 , 11 ]. In the present study there was an effect on milk yield over the latter stages of the study whereas there was no effect in the first 6 weeks of exposure to LDPP.…”

“…The decline in ovulatory activity during LDPP is supported by Garcia-Hernandez, et al [ 3 ] who looked at reproductive performance at parturition and found that a higher proportion of LDPP goats were pseudo-pregnant compared to goats under natural light conditions which led them to speculate that LDPP was detrimental to reproductive performance. On the other hand, LDPP exposure in goats in the sub-tropics did not decrease ovulation rate in another study [ 11 ]. Rivera et al [ 15 ] found that reproductive activity late in the breeding season had a higher proportion of detached cycles where a silent ovulation occurred, or oestrous behaviour only was observed.…”

“…The study by Garcia-Hernandez, et al [ 3 ] conducted in the Northern Hemisphere found that average milk yield increased by 15% in goats exposed to LDPP during the final 6 months of lactation but the response was greatest over the last 3 months of lactation. On the other hand, the increase in milk yield in response to LDPP declined over the final 3 weeks in subtropical goats kidding in late Autumn and exposed to LDPP (14 h) for the first 110 days of lactation [ 11 ].…”

“…In the present study the buck effect was shown to override the effect of LDPP on ovulation, but only during the month of August when ovulatory activity was already low. In contrast, buck exposure had no effect on oestrus or ovulation in goats housed in the sub-tropics although in that study there were high rates of oestrus (100%) and ovulation (95%) in the does exposed to LDPP [ 11 ]. The present experiment was conducted in a commercial setting with does that were exposed to bucks being reintroduced into the group.…”

Reproduction in Small Ruminants (Goats)

“…In most areas of the world, goats are mated once yearly in the fall, during their natural mating season, for spring kidding [3][4][5]. Animals bred at this time are more likely to get pregnant and have multiple kids.…”