Abstract
The objective of this study was to assess various risk factors affecting fetal losses in high-yielding Holstein cows in a hot environment. In a retrospective observational study, 14,384 records from Holstein cows from a large highly technified dairy herd in northern Mexico were used. Logistic multivariate multiple-group response model indicated that fetal losses between 43 and 260 days of pregnancy were 23.8%. Dry periods >60 d were associated (p<0.05) with 0.8 (confidence interval CI=0.8–0.9) times lower incidence of fetal losses compared to cows with dry periods <60 d. Cows with body condition score (BCS) >3 at calving and 15 days postpartum had about half the risk of suffering fetal losses than cows with BCS <3.0. Cows with peak milk yield >38 kg were 5.5 times more likely to have a fetal loss than cows with peak milk yield <38 kg (36.9 vs. 9.6%; p<0.01). The risk of fetal loss increased with 305-d milk yield >9,000 kg (OR=2.1) compared with cows with milk yield <9,000 kg. Retained placenta was (p<0.05) associated with 1.2 (CI=1.1–1.4) times higher fetal losses than cows without this reproductive disorder. Cows suffering premature parturition had 1.2 (CI=1.0–1.4) greater (p<0.05) risk of suffering fetal losses than cows with normal parturition. Cows with twin pregnancies had significantly increased chances of losing their fetuses than cows with a single fetus (31.1 vs. 15.9 p<0.01). A bimodal distribution of fetal losses was observed with peaks around 50 and 220 days of pregnancy. It was concluded that in this particular hot environment fetal losses were associated with high milk yield, low body energy reserves at calving, reduced dry periods, occurrence of retained placenta, twin pregnancies and premature calving.
Highlights
The incidences of fetal losses in intensive dairy herds range from 7.6 to 20.5% (Starbuck et al, 2004; Pontes et al, 2015), a 2.7-fold difference between herds
The infectious causes of abortion have been a primary focus of attention and the control these infectious diseases is based on several points like vaccination, but non-infectious fetal losses still is likely in dairy herds (López‐Gatius & García‐Ispierto, 2010)
Cows with long dry periods were less prone to fetal loss rate compared with cows with dry period ≤60 days
Summary
The incidences of fetal losses in intensive dairy herds range from 7.6 to 20.5% (Starbuck et al, 2004; Pontes et al, 2015), a 2.7-fold difference between herds. Causes for these apparent differences are not clear, the wide variation in the incidence of this reproductive disorder could be explained by the inconsistent definition of gestation loss among studies, the different gestational at-risk periods considered, and the wide computation methods used among studies. The infectious causes of abortion have been a primary focus of attention and the control these infectious diseases is based on several points like vaccination, but non-infectious fetal losses still is likely in dairy herds (López‐Gatius & García‐Ispierto, 2010).
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