The objective of this retrospective study was to investigate the prevalence of pregnancy loss (PL; between 28–110 pregnancy days) and its relationship with factors: farm, year (2015–2018), season, artificial insemination (AI)-rank, parity, AI-type (fixed-time vs. oestrus-AI), previous PL, days in milk (DIM), fixed-time-AI protocol, AI-technician, bull, and semen-type (sexed vs. conventional). Data of 19,437 Holstein cattle AIs from eight Spanish farms were studied. Overall conception rate was 34.3% (6696/19,437) and PL 12.3% (822/6696). The PL was more likely to occur in primiparous (10.8%, odds ratio (OR) = 1.35; p = 0.04) and multiparous (15.3%; OR = 2.02, p < 0.01) than in heifers (PL = 6.9%, reference). Pregnancies achieved with AI after observed oestrus and natural breedings were associated with less PL than pregnancies after fixed-time-AI (12.7 vs. 11.9%; OR = 0.12, p = 0.01). First AIs related to higher PL than ≥2nd AIs (PL = 13.8% vs. 11.2; OR = 0.73, p < 0.01). The factors season, fixed-time-AI protocol, DIM, bull, AI-technician, or type of semen were not significantly associated with PL. Therefore, farmers and consultants should adapt their preventive strategies relating to PL, particularly, to the parity of the cattle.

Bovine viral diarrhoea (BVD), one of the most important infectious diseases affecting bovine production systems, is thought to show a subclinical course in most cases, especially in regions that have suffered high BVD prevalence for a long time. However, few studies have assessed this rigorously under non-epidemic conditions. Here we assessed how often active BVD infection in a herd, defined as at least one antigen-positive animal, is associated with clinical signs. Surveying and sampling methods were used to detect BVD infection based on clinical picture. Analysis of 1203 samples of individual animals from 167 herds clinically suspected of BVD infection showed that 33.7% of dairy farms, 30.6% of beef cow-calf farms and 40% of feedlots contained at least one animal positive for BVD viral antigen. Prevalence of BVD infection was 7.7% at the animal level, much higher than the prevalence of 1–3% reported in the literature. This suggests that clinical picture can be useful for detecting active BVD infection, and that infections show a variable clinical course. On dairy farms, the presence of at least one antigen-positive animal was associated with a tendency towards lower fertility and higher rates of stillbirths and calf health problems (P < 0.1). On feedlots, such presence was associated with a tendency to a higher of calf health problems. In beef cow-calf systems, however, the presence of an antigen-positive animal was not associated with any particular sign. These results suggest a higher association of active BVD infections spreading in a herd and clinical pictures at the herd level, particularly in dairy herds.