Aguirre V, Orihuela A, Vázquez R
Facultad de Ciencias Agropecuarias de la Universidad Autónoma del Estado de Morelos, Av. Universidad 1001 Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
Trop Anim Health Prod. 2007 May;39(4):271-7. doi: 10.1007/s11250-007-9010-8.
The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behaviour and testosterone (T4) concentration in pelibuey rams subjected to different semen collection frequencies. eighteen intact males were assigned randomly to one of two semen collection frequencies: in the high rate (HR) treatment, two ejaculations per week were obtained from each ram; one ejaculation every two weeks was collected under the low rate (LR) treatment. All animals were housed individually in contiguous 5 m x 5 m wire mesh pens and evaluated over a 12-month period. At the beginning of the experiment rams were 20 months old and 40-50 kg in weight. All rams ejaculated and produced semen throughout the year. Semen volume, sperm per ejaculation, testicular circumference and testicular volume were significantly (p < 0.05) greater during short days in all rams, regardless of the semen collection frequency, with the exception of sperm concentration, for which no variation was found in hr individuals, and reaction time and T4 levels, for which no variation was found in IR males. Rams subjected to HR collection were more affected by the short-day photoperiod than rams collected twice per week, exhibiting greater reduction (p < 0.05) in time to achieve their first ejaculation and in sperm per ejaculation, as well as greater increases (p < 0.05) in T4 concentration than IR rams (14.65 +/- 1.22 vs 23.53 +/- 5.34 s, (3.37 +/- 0.17) x 10(9) vs (3.52 +/- 0.20) x10(9) sperm and 8.68 +/- 0.44 vs 6.85 +/- 0.74 ng/ml, respectively). It was concluded that: (a) the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year, and (b) seasonal variation within variables was affected differently between semen collection frequencies.
本研究的目的是考察日长对不同采精频率的佩利布埃公羊精液特性、睾丸大小、性行为及睾酮（T4）浓度的影响。18只成年雄性公羊被随机分配到两种采精频率之一：在高频率（HR）处理组，每只公羊每周采精两次；低频率（LR）处理组每两周采精一次。所有动物单独饲养在相邻的5米×5米的铁丝网围栏中，为期12个月。实验开始时，公羊年龄为20个月，体重40 - 50千克。所有公羊全年都能射精并产生精液。无论采精频率如何，所有公羊在短日照期间的精液量、每次射精的精子数、睾丸周长和睾丸体积均显著（p < 0.05）增加，但HR组个体的精子浓度以及IR组雄性的反应时间和T4水平未发现变化。与每周采精两次的公羊相比，HR组公羊受短日照光周期的影响更大，首次射精时间和每次射精的精子数减少幅度更大（p < 0.05），T4浓度的增加幅度也更大（p < 0.05），分别为（14.65 ± 1.22对23.53 ± 5.34秒）、（3.37 ± 0.17）×10⁹对（3.52 ± 0.20）×10⁹个精子以及8.68 ± 0.44对6.85 ± 0.74纳克/毫升）。研究得出结论：（a）季节性影响的程度不足以阻止公羊全年用于繁殖，（b）不同采精频率下变量的季节性变化受到的影响不同。
