Reproductive seasonality in female goats adapted to a subtropical environment persists independently of food availability.
The aim of this study was to determine whether the seasonal change in food availability provides a predictive cue that synchronizes the breeding season in goats adapted to the subtropical conditions of Northern Mexico. Groups of multiparous intact (n=7) and ovariectomized does bearing a subcutaneous implant constantly releasing estradiol-l7 beta (OVX+E; n=12) were allocated in two pens and received a constant amount of feed. Another group of OVX+E does (n=10) was incorporated into a flock raised under natural grazing conditions with seasonal fluctuations in food availability. Blood samples were taken twice weekly. Ovulation of intact goats was inferred from plasma progesterone levels. In OVX+E does plasma levels of LH were measured. Intact does displayed seasonal variations in ovulation and the breeding season lasted from September to February. OVX+E goats displayed large seasonal variations in LH secretion regardless of whether they were fed constantly indoors or kept under natural grazing conditions (P<0.0001). The mean date of increase in LH secretion varied between years (P<0.0001) but did not differ between groups (naturally grazed: August 13+/-10 days; constantly fed: August 26+/-10 days). In contrast, the seasonal decline in LH secretion differed between groups: it was consistently delayed in constantly fed animals compared to those feeding naturally (naturally grazed: January 28+/-4 days; constantly fed: February 24+/-6 days, group effect, P<0.01). These results show that local female goats from subtropical Mexico display large reproductive seasonality independently of food availability.
Duarte
G
G
Centro de Investigación en Reproducción Caprina, Universidad Autónoma Agraria Antonio Narro, Periférico Raúl López Sánchez y Carretera a Santa Fe, C.P. 27054, Torreón, Coahuila, Mexico.
Flores
J A
JA
Malpaux
B
B
Delgadillo
J A
JA
D000818:Animals; D001835:Body Weight / Q000502:physiology; D004435:Eating / Q000502:physiology*; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology; D030762:Estrous Cycle / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006041:Goats / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood / Q000502:physiology; D010052:Ovariectomy / Q000662:veterinary; D017440:Photoperiod; D010865:Pilot Projects; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D014329:Tropical Climate
D004958:Estradiol; D007986:Luteinizing Hormone