Influence of Season and Oestrous Cycle Phase on Serum Progesterone and Thyroxine Profiles in Savanna Brown Goats

The study was carried out to determine the effect of seasonal changes and oestrous cycle phase on serum progesterone (P4) and thyroxine (T4) profiles in Savanna Brown (SB) goats. Ten (n = 10) cycling SB goats with mean body weight and body mass index of 20.17 ± 0.2 kg and 6.2 ± 0.4, respectively were allotted to 2 groups of 5 animals each per season of study (Hot-rainy, HRS and cold-dry, CDR). Mean oestral serum P4 (ng/mL) concentrations were as follows: HRS: 0.05 ± 0.04 vs CDS: 0.05 ± 0.07; dioestral: HRS: 0.52 ± 0.02 vs CDS 0.62 ± 0.08. Combined mean of oestral and dioestral serum P4 concentrations were, HRS: 0.05± 0.02 vs CDS: 0.57 ± 0.06. Mean oestral serum T4 (ng/mL) concentrations were,HRS: 75.83 ± 4.13 vs CDS: 85.10 ± 3.90; dioestral: HRS: 78.70 ± 2.72 vs CDS: 92.35 ± 4.01 (P ˂ 0.001). Combined mean of oestral and dioestral serum T4 concentrations were, HRS: 77.42 ± 2.35 vs CDS: 89.93 ± 2.90 (P ˂ 0.001). In conclusion, mean serum T4 concentrations were significantly higher during CDS than HRS season cycles. While, peak serum T4 level coincided with peak P4 activity at midand late dioestrus/proestrus phases of both HRS and CDS cycles.