Effect of temperature - humidity index on the onset of post- partum ovarian activity and reproductive behavior in Bos indicus cows

• Published in: Animal reproduction Vol. 17; no. 1; p. e20190074
• Main Authors: Díaz, Ramiro Fernando, Galina, Carlos Salvador, Aranda, Emilio Manuel, Aceves, Lorenzo Armando, Sánchez, Jaime Gallegos, Pablos, Jose Luis
• Format: Journal Article
• Language: English
• Published: Brazil Colégio Brasileiro de Reprodução Animal - CBRA 01-01-2020; Colégio Brasileiro de Reprodução Animal
• Subjects: BIOTECHNOLOGY & APPLIED MICROBIOLOGY; Original; fat thickness; beef cows; reproductive cyclicity; natural mating; temperature-humidity index
• ISSN: 1984-3143; 1806-9614; 1984-3143
• DOI: 10.21451/1984-3143-AR2019-0074

The effect of climatic factors on ovarian activity and reproductive behavior (RB) was evaluated in 46
cows kept under grazing conditions. Temperature-humidity index (THI) was used as an indicator of stress and divided in alert, damage and emergency levels. Fat thickness (FAT) was taken during the last trimester of gestation (LTG) to approximately 90d postpartum (PP). At 30d PP animals received a progesterone (P
)-releasing device (CIDR) which was withdrawn 9d later. Ovarian activity was assessed by blood progesterone on days 21, 24, 27, 30, 49, 51, and 54 PP. Animals were divided into three groups, higher, and moderate RB and non-behavior. Sixty percent presented a THI >74 increasing dramatically from June to September up to >78. During LTG, animals lost 27% of their body reserves contrasting to PP where an increase of 2.6% (P=0.002) was observed. The percentages of cyclic and non-cyclic animals were 57 and 43%, respectively (P> 0.05). Seventy-two percent displayed RB and 28% were non-behavior (P<0.05). A negative correlation (r = -0.307; P = 0.038) between THI and RB, and a positive correlation (r = 0.427; P = 0.003) between the onset of ovarian activity and RB were observed. Differences in THI during the LTG (P<0.01) were observed between cyclic and non-cyclic animals. Non-behavior cows in the LTG had a higher THI (P <0.05). High levels of THI have a negative effect on the resumption of ovarian activity and RB in
especially if high THI occurs during the last trimester of gestation.