Relationship between subclinical mastitis and reproduction in Lacaune sheep

Abstract

The objective of this study was to determine how the occurrence and etiology of subclinical mastitis (SM) in the postpartum period was correlated with uterine involution (UI), return to estrus, and ovarian activity. Lacaune ewes (n = 87) were categorized based on the occurrence of one or more SM events diagnosed on days 5, 20, 35, and 50 after lambing. The animals diagnosed with SM (mastitis group, n = 49) were categorized according to the disease etiology into four groups (coagulase-negative Staphylococcus [CNS], Staphylococcus aureus, coliforms, and other gram-positive pathogens). The control group (n = 38) was ewes not diagnosed with SM at any of the evaluations. The group without pathogen isolation (WPI) consisted of SM-positive sheep according to the California Mastitis Test but without pathogen isolation by microbiological culture. Ultrasonographic examination of UI, characterized by uterine horn diameter ≤ 2 cm with no content in the uterine lumen, was evaluated on days 15, 30, and 45 after lambing. Ovarian activity was evaluated from the time of estrus detection every 12 h until ovulation. The number of corpora lutea and the total luteal area were determined 10 days after ovulation. Occurrence and etiology of SM were not correlated with ultrasonographic examination of UI, and at 45 days after lambing, all sheep had involuted uteri. Estrus detection began on the 20th day postpartum, and 57.47% (50/87) of the ewes exhibited estrus until the 60th day postpartum. The diameter of the largest follicle was smaller in ewes diagnosed with SM on the 50th day after lambing than in the control group (P < 0.05). The WPI group had a smaller diameter of the largest follicle (P < 0.001) than the control group and the CNS group. The number of follicles, the number of corpora lutea, and the total luteal area were not influenced by SM occurrence or etiology. The chance of exhibiting estrus within 60 days was higher in the group affected by mastitis than in the control group. Furthermore, twin-bearing ewes and ewes with viable lambs were less likely to express estrus.