饲喂频率对妊娠母猪背膘厚和繁殖性能的影响

[目的] 研究饲喂频率对妊娠母猪背膘厚和繁殖性能的影响。[方法] 挑选加系杜洛克经产母猪480头,配种时按照胎次（2~7胎）、背膘厚（11~22 mm）相近的原则随机将母猪分为T1组（每天饲喂1次）和T2组（每天饲喂2次）,两组每天等量饲喂。T1组母猪220头,饲喂时间为8：00;T2组母猪260头,饲喂时间为8：00和15：00,每次饲喂量为总量的一半,定位栏饲养。[结果] ①饲喂频率不影响妊娠56 d、开配-妊娠56 d的背膘厚（妊娠56 d背膘厚-开配背膘厚）（P>0.05）;T2组妊娠110 d（P=0.06）、妊娠56-110 d（P=0.09）背膘厚（妊娠110 d背膘厚-妊娠56 d背膘厚）有高于T1组的趋势。②饲喂频率对窝产总仔数、活仔数、死胎数、木乃伊胎数、初生窝重以及初生个体重均无显著（P>0.05）影响。③在三胎母猪中,T2组妊娠110 d（P=0.01）、妊娠56-110 d（P=0.04）背膘厚均显著高于T1组;五胎及以上母猪,T2组妊娠56-110 d（P=0.08）背膘厚有高于T1组的趋势。④饲喂频率不影响二胎母猪窝产总仔数、死胎数、木乃伊胎数、初生窝重以及初生个体重（P>0.05）,但二胎母猪中T2组活仔数有高于T1组的趋势（P=0.07）。[结论] 饲喂频率由每天两餐减少到每天一餐不会对母猪的繁殖性能产生不利影响。     

A multichannel automated chamber system for continuous measurement of forest soil CO2 efflux

We developed a fast-response multi-chamber system for measuring soil-surface CO2 efflux (Fc). The chambers (90 x 90 x 50 cm, L x W x H) had lids that opened and closed automatically, and were connected in parallel to a single CO2 analyzer equipped with a 16-channel gas sampler. Between measurements the chamber lids were raised to allow precipitation and leaf litter to reach the enclosed soil surface. When a chamber was closed, it was ventilated with well-buffered ambient air (125 l min-1) that entered by an inlet on one chamber sidewall and exited through a large vent on the opposite sidewall. The pressure difference between the inside and outside of the chamber was less than 0.22 Pa. Two additional mixing fans maintained an air speed of 0.3 +/- 0.1 m s-1 at 20 cm above the soil surface. Air was withdrawn continuously from the inlets and outlets of each chamber, and fed sequentially to an infrared CO2 analyzer. With this system, we measured Fc in a 40-year-old temperate Pinus densiflora Sieb. & Zucc. forest from February 8 to May 30, 2001. Mean Fc increased steadily from 0.9 micro mol m-2 s-1 at the beginning of February to 4.6 micro mol m-2 s-1 by the end of May. There was a statistically significant correlation between Fc and surface soil temperature (r = 0.896; P < 0.0001), and the Q10 value was 2.8. Spatial variation of Fc was higher in the non-growing season than in the growing season. Measurements were not interrupted by either rain or snow.     

Effect of a single injection of gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG) on testicular blood flow measured by color doppler ultrasonography in male Shiba goats

Although color Doppler ultrasonography has been used to evaluate testicular blood flow in many species, very little has been done in goat. Eight male Shiba goats were exposed to a single intramuscular injection of either gonadotropin-releasing hormone (GnRH group; 1 µg/kg BW) or human chorionic gonadotropin (hCG group; 25 IU/kg BW). Plasma testosterone (T), estradiol (E2) and inhibin (INH) were measured just before (0 hr) and at different intervals post injection by radioimmunoassay. Testis volume (TV) and Doppler indices, such as resistive index (RI) and pulsatility index (PI) of the supratesticular artery, were measured by B-mode and color Doppler ultrasonography, respectively. The results indicated an increase in testicular blood flow in both groups, as RI and PI decreased significantly (P<0.05), but this increase was significant higher and earlier in hCG group (1 hr) than in the GnRH group (2 hr). A high correlation was found for RI and PI with both T (RI, r= −0.862; PI, r= −0.707) and INH in the GnRH group (RI, r=0.661; PI, r=0.701). However, a significant (P<0.05) correlation was found between E2 and both RI (r= −0.610) and PI (r= −0.763) in hCG group. In addition, TV significantly increased and was highly correlated with RI in both groups (GnRH, r= −0.718; hCG, r= −0.779). In conclusion, hCG and GnRH may improve testicular blood flow and TV in Shiba goats.     

Accessory corpora lutea formation in pregnant Hokkaido sika deer (Cervus nippon yesoensis) investigated by examination of ovarian dynamics and steroid hormone concentrations

Generally, sika deer conceive a single fetus, but approximately 80% of pregnant females have two corpora lutea (CLs). The function of the accessory CL (ACL) is unknown; moreover, the process of ACL formation is unclear, and understanding this is necessary to know its role. To elucidate the process of ACL formation, the ovarian dynamics of six adult Hokkaido sika deer females were examined ultrasonographically together with peripheral estradiol-17β and progesterone concentrations. ACLs formed in three females that conceived at the first estrus of the breeding season, but not in those females that conceived at the second estrus. After copulation, postconception ovulation of the dominant follicle of the first wave is induced by an increase in estradiol-17β, which leads to formation of an ACL. A relatively low concentration of progesterone after the first estrus of the breeding season is considered to be responsible for the increase in estradiol-17β after copulation.     

Estrogen suppresses melatonin-enhanced hyperactivation of hamster spermatozoa

Hamster sperm hyperactivation is enhanced by progesterone, and this progesterone-enhanced hyperactivation is suppressed by 17β-estradiol (17βE₂) and γ-aminobutyric acid (GABA). Although it has been indicated that melatonin also enhances hyperactivation, it is unknown whether melatonin-enhanced hyperactivation is also suppressed by 17βE₂ and GABA. In the present study, melatonin-enhanced hyperactivation was significantly suppressed by 17βE₂ but not by GABA. Moreover, suppression of melatonin-enhanced hyperactivation by 17βE₂ occurred through non-genomic regulation via the estrogen receptor (ER). These results suggest that enhancement of hyperactivation is regulated by melatonin and 17βE₂ through non-genomic regulation.     

Regulation of gonadotropin subunit genes expression by 11-ketotestosterone during early spermatogenesis in male red seabream, Pagrus major

To examine the roles of gonadal steroids in the regulation of expression of gonadotropin subunit genes, male red seabream were gonadectomized and a sub-group was treated with 11-ketotestosterone (11-KT). Castration of males during the early stage of spermatogenesis elicited a significant increase in FSHβ mRNA levels, which was prevented by 11-KT replacement. By contrast, LHβ mRNA levels were not changed by castration or 11-KT replacement. In addition, administration of 11-KT to sham-operated males suppressed the steady-state FSHβ and LHβ mRNA levels. These results indicate that 11-KT may function as a negative feedback regulator of FSHβ gene expression, and may act through the testis to down-regulate LHβ mRNA levels in male red seabream during this period.