Browsing by Author "Hansen, P. J."

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    Cows exposed to heat stress during fetal life exhibit improved thermal tolerance
    (Oxford University, 2017-06-12) Ahmed, B. M. S.; Younas, U.; Asar, T. O.; Hansen, P. J.; Dahl ., G. E.; Dikmen, S.; Uludağ Üniversitesi/Veteriner Fakültesi/Hayvan Bilimleri Anabilim Dalı.; 0000-0002-5611-4993; A-5731-2018; 8280302600
    Maternal heat stress during late gestation affects calf function during postnatal life. The objective of the present study was to evaluate whether calves that experience heat stress in utero have altered thermoregulatory responses to acute heat stress later in life. Specifically, the hypothesis was that heat stress in utero would improve the response to acute heat stress at maturity. Females were born to dams exposed to heat stress or cooled during late gestation preceding their birth. All animals were raised postnatally under identical management. Twelve lactating Holstein cows that were exposed to in utero heat stress (HT) and 12 that were exposed to in utero control (CON) were used. A heat stress challenge was conducted in 3 blocks using 4 HT and 4 CON cows matched according to milk yield, stage of lactation, and parity. Each challenge consisted of transfer from a barn with shade and evaporative cooling to one with shade but no additional cooling for 48 h. The challenge was replicated twice for each block. Sweating rate, respiration rate, rectal temperature (RT), and skin temperature were measured on each cow at 0900, 1100, 1300, 1500, and 1700 h for 2 consecutive days. Mean ambient temperature across 6 challenge days was 26.15 +/- 4.75 degrees C. Tendencies for differences at 1700 h were observed between treatments for RT (HT: 39.5 +/- 0.1; CON: 39.6 +/- 0.1 degrees C; P = 0.065), however, there was no difference in respiration rate (HT: 77.6 +/- 1.6; CON: 79.5 +/- 1.6 bpm; P = 0.85). Sweating rate for shaved skin (HT: 29.4 +/- 2.0; CON: 36.0 +/- 2.0 g/m(2)h; P = 0.057) and for non-shaved skin (HT: 22.5 +/- 1.5; CON: 29.2 +/- 1.2 g/m(2)h; P = 0.01) differed between groups. However, there was no effect on skin temperature at the shaved location (HT: 36.2 +/- 0.2; CON: 36.0 +/- 0.2 degrees C; P = 0.81), but there was a tendency for differences for the non-shaved area (HT: 35.4 +/- 0.2; CON: 34.9 +/- 0.2 degrees C; P = 0.097). Cows that underwent in utero heat stress had greater skin temperature at 1700 h vs. in utero control cows, which may be because HT cows increased skin perfusion, and consequently greater cooling via conduction. In utero HT cows would then have higher heat loss and reduced core body temperature, which results in lower rectal temperature and lower sweating rate when exposed to heat stress. These results support the hypothesis that heat stress in utero in late gestation increases heat tolerance at maturity by increasing capacity to dissipate heat to maintain core body temperature.
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    Interactions of human chorionic gonadotropin with genotype and parity on fertility responses of lactating dairy cows
    (Elsevier, 2019-01) Zolini, A. M.; Ortiz, W. G.; Estrada-Cortes, E.; Ortega, M. S.; Sosa, F.; Hansen, P. J.; Giordano, Julio O.; Dikmen, Serdal; Bursa Uludağ Üniversitesi/Veteriner Fakültesi/Zootekni Ve Hayvan Besleme Ve Veterinerlik Zootekni Bölümü.; 0000-0002-5611-4993; A-5731-2018; 8280302600
    Fertility-promoting effects of treatment of lactating dairy cattle with human chorionic gonadotropin (hCG) after artificial insemination (AI) have been variable. Here, we tested whether fertility response to hCG in lactating Holstein cows interacts with genotype and parity. Primiparous (n = 538) and multiparous (n = 613) cows were treated with hCG (3,300 IU) or vehicle 5 d after AI. Pregnancy was diagnosed on d 32 and 60 after AI. A subset of cows (n = 593-701) was genotyped for 4 single nucleotide polymorphisms (SNP) previously associated with fertility. Treatment with hCG increased progesterone concentration on d 12 after AI regardless of genotype or parity. Pregnancy per AI was improved by hCG in primiparous cows but riot in multiparous cows. Moreover, hCG treatment interacted with a SNP in coenzyme Q9 (COQ9) to affect fertility. Fertility of cows treated with vehicle was greatest for the AA allele, whereas fertility was lowest for the same genotype among cows treated with hCG. Pregnancy per AI was also affected by genotype for heat shock protein AI-like (HSPA1L) and progesterone receptor (PGR), but no interactions were observed with treatment. Genotype for a SNP in prostate androgen-regulated mucin-like protein 1 (PARM1) was not associated with fertility. Overall, results show that variation in response to hCG treatment on fertility depends on parity and interacts with a SNP in COQ9.