Seasonal fertility differences in synchronised dairy cows: ultrasonic, metabolic and endocrine findings.

The aim of this study was to identify relationships among seasonal differences of fertility, metabolic parameters and appearance of irregular luteal forms in high-yielding dairy cows. Holstein-Friesian cows were put on the Provsynch regimen in winter (n = 10) and in summer (n = 10). Blood sampling (starting 35 days post partum) and rectal ultrasound examinations (starting post insemination) were carried out once a week in each examination period. Metabolic [plasma nonesterified fatty acid (NEFA) and beta-hydroxybutyrate (BHB) levels, ferric reducing ability of plasma (FRAP) and serum beta-carotene] and endocrine parameters [plasma thyroxine (T4), triiodothyronine (T3), insulin-like growth factor (IGF-I) and insulin levels] were measured. In summer, two cows were excluded from the study because of metritis and none of the remaining animals became pregnant, but 6 of the 8 cows had irregular luteal forms (ILF) on their ovaries. In winter, one cow was excluded because of metritis and 6 of the 9 cows became pregnant, while 2 of the 3 open cows had irregular luteal forms. In summer the mean plasma NEFA and BHB concentrations were significantly higher, while serum carotene and plasma IGF-I concentrations were significantly lower than in winter. The high plasma NEFA concentration found in summer seemed to be in association with the lower body condition score (BCS) caused by depressed appetite. In conclusion, statistical analysis supports the hypothesis that increased plasma NEFA and BHB and decreased plasma IGF-I concentrations may result in reduced fertility in summer. These changes may be associated with the more frequent appearance of ILFs and probably have a negative effect on ovarian function and/or oocyte quality.

Estrus response and fertility after a single cloprostenol treatment in dairy cows with various ovarian structures.

The objective of this study was to determine rates of estrus and conception in lactating multiparous Holstein cows given 500 µg of cloprostenol intramuscularly after detection of the following ≥ 60 d after parturition: a solid corpus luteum (CL), a CL with a nonechodense cavity ≤ 20 mm in diameter (CLcav), a luteal cyst (cavity > 20 mm in diameter and a luteinized wall > 3 mm in diameter), or a follicular cyst (cavity > 20 mm and a luteinized wall ≤ 3 mm in diameter). The estrus rates were 335/419 (80.0%), 183/223 (82.1%), 170/182 (93.4%), and 44/87 (50.6%), respectively (P < 0.0001), and the conception rates 30 to 36 d after insemination among the estrous cows with an apparently normal mucus discharge were 130/285 (45.6%), 44/141 (31.2%), 39/79 (49.4%), and 19/30 (63.3%), respectively (P < 0.002). Compared with a solid CL, a CLcav did not affect the estrus rate but significantly reduced the conception rate (P < 0.05), and the estrus rates were significantly higher and lower in cows with a luteal or follicular cyst, respectively (P < 0.05).

L'objectif de la présente étude était de déterminer les taux d'oestrus et de conception chez des vaches Holstein multipares en lactation à qui on administra 500 µg de cloprosténol par voie intramusculaire après détection d'un des éléments suivants ≥ 60 j après la parturition : un corps jaune solide (CL), un CL avec une cavité non-échodense ≤ 20 mm de diamètre (CLcav), un kyste lutéal (cavité > 20 mm de diamètre et une paroi lutéinisée > 3 mm de diamètre), ou un kyste folliculaire (cavité > 20 mm et une paroi lutéinisée ≤ 3 mm de diamètre). Les taux d'oestrus étaient de 335/419 (80,0 %), 183/223 (82,1 %), 170/182 (93,4 %), et 44/87 (50,6 %), respectivement (P < 0,0001), et les taux de conception 30 à 36 j après insémination parmi les vaches en oestrus avec un écoulement de mucus d'apparence normale étaient 130/285 (45,6 %), 44/141 (31,2 %), 39/79 (49,4 %), et 19/30 (63,3 %), respectivement (P < 0,002). Comparativement à un CL solide, un CLcav n'a pas affecté le taux d'oestrus mais a réduit significativement le taux de conception (P < 0,05), et les taux d'oestrus étaient significativement plus élevés et plus faibles chez les vaches avec, respectivement, un kyste lutéal ou folliculaire (P < 0,05).(Traduit par Docteur Serge Messier).