Lahrmann K H
Berl Munch Tierarztl Wochenschr. 1989 Jul 1;102(7):227-33.
In 7 herds half of the sows of each service area have been illuminated, additionally to the natural daylight, with artificial light during 2 years (year 1: 100 1 x; year 2: 300 1 x). From 2965 services parameters of fertility of the natural and artificial light groups have been recorded and compared within and between herds as well as seasons. Seasonal variations of fertility, as reported by other authors, have been confirmed under natural and artificial light. Generally the results under additional artificial light were better in all seasons. The duration of daylight seems to be one of the main reasons for seasonal variations of fertility. During the period of April, May and June (increasing daylength from 13 h to 17 h, but moderate temperatures from 13 degrees C to 22 degrees C) fertility was most depressed, followed by the period of July, August and September (decreasing daylength from 17 h to 12 h, temperatures from 24 degrees C to 22 degrees C). The best fertility has been recorded during winter (October to March, less than 12 h daylength). In addition to increased light intensity a period of 12 h artificial lighting appears to be favourable in winter with less than 12 h natural daylength, but it is not effective during summer with daylengths longer than 12 h. In respect to these results reducing natural daylength to 12 h during summer maintaining sufficient light intensity might be useful.
在7个猪群中，每个配种区域的一半母猪在两年时间里（第1年：100勒克斯；第2年：300勒克斯）除自然光照外还接受了人工光照。记录了自然光照组和人工光照组2965次配种的繁殖参数，并在猪群内部和之间以及不同季节进行了比较。正如其他作者所报道的，在自然光照和人工光照条件下都证实了繁殖力的季节性变化。一般来说，在所有季节中，额外人工光照下的结果都更好。日照时长似乎是繁殖力季节性变化的主要原因之一。在4月、5月和6月期间（日照时长从13小时增加到17小时，但温度适中，从13摄氏度到22摄氏度），繁殖力最低，其次是7月、8月和9月期间（日照时长从17小时减少到12小时，温度从24摄氏度到22摄氏度）。冬季（10月至3月，日照时长少于12小时）的繁殖力最佳。除了增加光照强度外，在自然日照时长少于12小时的冬季，12小时的人工光照时段似乎是有利的，但在日照时长超过12小时的夏季则无效。基于这些结果，在夏季将自然日照时长减少到12小时并保持足够的光照强度可能是有用的。
