Impact of Environmental Heat Stress on Ovarian Function of Zebu Cows
Impact of Environmental Heat Stress on Ovarian Function of Zebu Cows
N. Wachida1*, P. M. Dawuda2,1, I. U. Ate3,1, P. I. Rekwot4, 2
ABSTRACT
Study evaluated the impact of environmental heat stress on follicle diameter, and ovarian hormones concentrations. Twelve (n=12) non-pregnant, Zebu cows with 2-3 successive calving record were utilized. Temperature humidity index (THI) determined and rectal temperatures of cows were monitored. Cows were synchronized for oestrus using PGF2α. Follicular studies were carried out. Serum oestradiol and luteinizing hormones were monitored by Enzyme-Linked Immunosorbent Assay (ELISA). Blood samples for serum were collected for oestradiol and luteinizing hormones. Follicular diameters at 42 hr were longer (P<0.05) in hot dry season (8.088±0.52 mm) than in raining seasons (8.618±0.9 mm) and cold dry season (6.338± 0.68 mm). At 72 hr follicular diameters were longer (P<0.05) in hot dry season (17.006±1.41 mm) than cold dry (12.898±1.22 mm) and raining seasons (12.075±0.82 mm). Time to peak of oestradiol surges were shorter (P<0.05) in cold dry season (31.50±5.41 hr) than hot dry season (35.42±4.25 hr) and raining seasons (52.25±7.08 hr). Oestradiol concentrations were higher (P<0.05) in cold dry season (39.13±5.27 pg/dL) than hot dry (19.50±2.52 pg/dL) and raining seasons (17.63±1.89 pg/dL). Time to peak of LH surges were earlier (P<0.05) in cold dry season (38.38±2.29 hr) than hot dry season (44.40±4.76 hr) and raining season (53.86±5.37 hr). LH concentrations were higher (P<0.05) in raining season (11.8±4.59 ng/mL) than cold dry (4.14±0.3 ng/mL) and hot dry seasons (4.18±0.86 ng/mL). Duration of LH surges were longer (P<0.05) in cold dry season (18.63±2.67 ng/mL) than raining season (8.71±2.94 ng/mL). In conclusion, heat stress affected ovarian function by increasing follicles diameters, reducing oestradiol concentrations, and affected onset and duration of LH surges.
Keywords | Follicle, Hormone, Season, Zebu cows, Reproduction.
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