Seasonal Variations in Hours of Daylight Associated with Fertility Level of Cattle under Natural Breeding Conditions

A Study of the Reproductive Performance of a Purebred Hereford Herd1

“…There was a large monthly variation in spermatozoan concentration, initial motility, and motility after thirty minutes at 45°c. Mercier and Salisbury (1947) noted a similar condition in Eastern Canada, where the fertility of Ayrshire, Holstein, Shorthorn, and Milking Shorthorn bulls was highest in summer and lowest in winter . Schultze et al (1948) at Nebraska noted among 25,146 services a decreased conception rate in the summer (52.5…”

“…(1948) at Nebraska reported a conception rate of 59 per cent in the spring and only 52 per cent in the summer . Mercier and Salisbury (1947) reported a significant correlation of 0 . 59 between fertility and the average monthly temperature of the month in which the cows were bred .…”

REVIEW: Factors Affecting Decisions on When to Calve Beef Females

“…Similar stress-related physiological responses and lower fertility have been observed in females during cold stress in northern states and Canada, but this has also been attributed to, and is potentially confounded by, day length (34,35). There is evidence that decreasing day length, compared with increasing day length, results in reduced conception rates (38) and increased frequency of an ovulatory estrus (30,43,58).…”

Untersuchungen an Kühen des Vereins Ostfriesischer Stammviehzüchter zur Steigerung des prozentischen Milchfettgehaltes über 4 Prozent hinaus als Problem der energetischen Lebensleistung

“…Die Nutzungsdauer und die mittlere Zwischen-nachst rasch an, a b e l l e 6 V e r t e i l u n g d e r K u h e n a c h Z w i s c h e n k a l b e z e i t u n d r n i t t l e r c r L e b e n s l e i s t u n g i n F C 50 50 50 50 50 5 0 1 50 50 50 50 50 50 50 50 5 0 Eine Drosselung der Jahresleistungen bei hoch veranlagten Tieren, ohne Schadigung der Gesundheit, kann durch eine Regulierung des Eiweii3-Starkeeinheiten-Verhaltnisses erfolgen, des weiteren wurde es empfehlenrwert sein, die Kalbungen grundsatzlich in das Fruhjahr zu verlegen. Aus Arbeiten von CANNAN (5), HAMMOND (18), MERCIER c. s. (37,38), ERB c. s.…”