Tatsuyuki Yoshida

Association of BoLA-DRB3 alleles with mastitis resistance and susceptibility in Japanese Holstein cows.

In this study, 714 cows from 26 dairy herds were reclassified as healthy or mastitic cows on the basis of long-term somatic cell count (SCC) in milk. Cows with more than three consecutive lactation records of SCC from the first or second to fifth lactation, were selected, and their BoLA-DRB3 (DRB3) alleles were identified using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Cows with an SCC of < 200 000 cells/mL in all monthly records were classified as healthy (n=91). Cows with an SCC of > 300 000 cells/mL in two consecutive tests or four non-consecutive tests or cows with an SCC of > 500 000 cells/mL in any one test during lactation, regardless of parity, were classified as mastitic (n=201). Mastitic cows (n=153) from another 40 herds were considered to be infected if bacteriological testing revealed mastitis pathogens in milk. Their DRB3 alleles were identified using PCR-sequence-based typing (PCR-SBT). The differences in DRB3 allelic frequencies between healthy cows and cows with various degrees of mastitis were re-investigated. Moreover, the associations of various amino acid motifs in DRB3 alleles with resistance or susceptibility to mastitis pathogens were re-examined. DRB3.2*8(DRB3*1201) and DRB3.2*16(DRB3*1501) alleles were found to be associated with susceptibility, while DRB3.2*22(DRB3*1101), DRB3.2*23(DRB3*2703), and DRB3.2*24(DRB3*0101) alleles were found to be associated with resistance.

Relation of reproductive performances and rectal palpation for luteum function of heifers 7 days after estrus

Diagnosis of corpus luteum (CL) function by rectal palpation (RP) has been widely used for recipient selection of embryo transfer (ET), a technology essential for genetic improvements in cattle. To examine the accuracy of RP diagnosis method, the relationship between RP-based CL function and reproductive performance was compared in this study. In Experiment 1, CL of Holstein heifers on day 7 after estrus was classified into functional or hypoplastic by RP, and the results were compared with ultrasonographic (US) images and plasma progesterone (P4) levels. As a result, heifers with functional CL judged by RP had a mean maximum CL diameter of 20.1 ± 3.1 mm on US and a mean P4 concentration of 8.1 ± 2.3 ng/mL. These values were significantly greater than those of heifers with hypoplastic CL (12.4 ± 5.4 mm, 4.0 ± 2.8 ng/mL) (P < 0.001). In Experiment 2, the length of the estrus cycle was examined between functional CL and hypoplastic CL. The rate of heifers with a normal estrus cycle length with 18-25 days was significantly lower with hypoplastic CL than with functional CL (16/24 vs. 43/46, P < 0.01). In Experiment 3, 543 inseminated heifers were similarly classified by CL function by RP 7 days after estrus. The heifers with functional CL showed higher pregnancy rate compared with the heifers with hypoplastic CL (75.2 vs. 47.9%, P < 0.0001). Finally, the CL function of 66 heifers was examined by RP on day 7 post-estrus, and ET was performed in 49 (74.2%) heifers with functional CL. As a result, 27 (55.1%) of them became pregnant. Taken together, these results reconfirm that RP on day 7 after estrus is useful for selection of heifers with functional CL.

Effect of estrus synchronization treatment after luteolysis on Holstein heifers as embryo transfer recipients.

This study was designed to evaluate the effect of estrus synchronization treatments on recipient heifers for embryo transfer (ET). Holstein heifers were separated into the following three groups: (i) an administration of 50 µg GnRH (gonadotropin-releasing hormone) analog was given to heifers at a random stage of the estrus cycle, followed 7 days later by two administrations of 7.5 mg prostaglandin F2 alfa analog (PG) as control; (ii) another administration of 100 µg GnRH was given to the control group at 48 h after the administration of PG as the second GnRH group; and (iii) an administration of 0.75 mg estradiol benzoate (E2) was given to the control group at 24 h after the administration of PG as the E2 group. Each method caused estrus synchronization. Fresh embryos were nonsurgically transferred into the suitable recipients that had a functional corpora lutea (CL) 7 days after estrus. The E2 group showed a significantly higher (P < 0.01) rate of estrus synchronization (98.9%) at 1-3 days after PG administration and the final pregnancy rate of the E2 group (50.6%) was also significantly higher than the other groups (37.1%, P < 0.05 and 30.9%, P < 0.01, respectively). These findings demonstrate that E2 administration 24 h after PG protocol is effective for estrus synchronization of Holstein heifers, thus improving the productivity of ET.

Behavioral Responses of Chicks to a Saccharin-Quinine Mixture

To date, few reports have been published on the sensitivity of birds to sweet tastes. Therefore, in this study, the behavioral responses of White Leghorn chicks to the sweet taste of saccharin and the bitter taste of quinine were assessed. Three chicks were provided with a solution of 3.0 mM quinine and a mixture of 3.0 mM quinine mixed with 0.1, 0.5, 1.0, or 10.0 mM saccharin in a two-bottle choice test for 48 h. It was found that the chicks consumed more of the 0.5 mM saccharin/3.0 mM quinine mixture but significantly less of the 10.0 mM saccharin/3.0 mM quinine mixtures than the quinine solution alone (P<0.05). The aversive behavior of 3.0 mM quinine solution was eased when mixed with 0.5 mM saccharin, indicating that chicks are detecting the sweetness associated with the 0.5 mM saccharin. The aversion to the 1.0 and 10.0 mM saccharin solutions might be stronger than to the 3.0 mM quinine solution alone. These findings suggest that chicks are able to detect this artificial sweetener.