Artificial long-day photoperiod in the subtropics increases milk production in goats giving birth in late autumn12

Abstract

Two experiments were conducted to determine whether exposure to a photoperiod of artificial long days in autumn increased milk yield in subtropical goats milked once (Exp. I) or twice daily (Exp. II). In Exp. I, starting at d 10 of lactation, 1 group of does was kept under naturally decreasing photoperiod (DD1X; n = 8), whereas the other group was submitted to an artificial photoperiod of long days (LD1X; n = 8; 16 h light:8 h darkness). The kids were weaned 28 d after parturition, and dams were manually milked once daily. Milk yield and milk components (fat, protein, and lactose) were assessed up to 140 d of lactation. From d 0 to 28 of lactation (suckling phase), mean daily milk yield did not differ between DD1X and LD1X goats (2.3 ± 0.2 kg vs. 2.4 ± 0.2 kg; P = 0.717). However, between d 29 and 84 (early milking phase), mean daily milk yield was greater in LD1X does than in DD1X does (2.6 ± 0.1 kg vs. 2.1 ± 0.1 kg; P = 0.001). Finally, between d 85 and 140 (late milking phase), mean daily milk yield was greater in LD1X goats than in DD1X goats (P ≤ 0.05) only during the first 2 wk. In Exp. II, one group of goats was exposed to a photoperiod of naturally decreasing days (DD2X; n = 8) and another group was submitted to an artificial photoperiod of long days (LD2X; n = 7). In both groups, kids were weaned on d 28 of lactation and the dams were manually milked twice daily. During the nursing phase, mean daily milk yield did not differ between the DD2X and LD2X groups (2.5 ± 0.3 kg vs. 2.6 ± 0.2 kg; P = 0.767). In the early milking phase, mean daily milk yield was greater in LD2X than in DD2X goats (3.3 ± 0.2 kg vs. 2.8 ± 0.2 kg; P = 0.022), whereas during the late milking phase, milk yield did not differ between the 2 groups (P = 0.946). In both experiments, milk composition was not significantly influenced by exposure to long-day photoperiod. We conclude that, in subtropical female goats that start lactation in late autumn, exposure to an artificial long-day photoperiod stimulates milk yield, even if goats are milked once daily. In addition, combining exposure to long days with twice-daily milking will increase further milk yield in such goats without affecting milk components.

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

“…In the present study, the continuous exposure to an artificial longday photoperiod of 14 hr of light per day increased milk production during the first 100 days of lactation in goats that had given birth during late autumn. The findings of the current study agree with those described by Garcia-Hernandez et al (2007) and Flores et al (2011Flores et al ( , 2015 and Hernández et al (2016). Indeed, goats exposed to 20 or 16 hr of light per day showed an increase in milk production level compared with control animals.…”

“…In fact, in subtropical goats, it is well documented that exposure to artificial long days consisting in 20 (Garcia‐Hernandez et al., ) or 16 hr of light/day during natural decreasing photoperiod increased milk yield level. This effect was observed regardless if animals were milked once or twice per day (Flores et al., ; Hernández et al., ) or if they were under extensive grazing conditions with a food supplement (Flores et al., ). The results of the current study clearly show that the administration of 14 hr of light per day in goats starting their lactation during late autumn is a skeleton photocycle that results in a strong galactopoietic effect.…”

“…In goats, Garcia‐Hernandez, Newton, Horner, and Nuti () reported that exposure to a photoperiod consisting in 20 hr light and 4 hr of darkness was effective to increase the milk yield. In subtropical goats that gave birth during autumn, several studies demonstrated that exposition to artificial long days consisting of 16 hr light and 8 hr darkness increased by 21% the milk yield compared with animals under natural decreasing days (Flores et al., , , ; Hernández et al., ). However, in these animals, it remains unknown if reducing the exposure from 16 to 14 hr of light/day can be effective to stimulate milk production, like reported previously that this light regime inhibits ovulation (Duarte et al., ).…”

Effects of exposure to artificial long days on milk yield, maternal insulin‐like growth factor 1 levels and kid growth rate in subtropical goats

“…A previous report described the natural photoperiod variations throughout the year in the region where the present study was performed (Flores et al 2011). The average maximum and minimum temperatures recorded during the study were 24.6°C and 6.0°C, respectively.…”

“…Other physiological processes affected by changes in the natural photoperiod include changes in body growth, pelage, body composition and milk production (Gebbie et al 1999;Dahl et al 2000;Flores et al 2011). The effect of an altered photoperiod on milk production can be observed in dairy cattle submitted to an artificial long day photoperiod, despite the fact that this species does not have a seasonal reproductive pattern.…”