- Oral presentation
- Open Access
Extent of Prepartum Serum Retinol Concentration Decline Affects Postpartum Morbidity in Holstein Cows
- Thomas H. Herdt1
© The Author(s); licensee BioMed Central Ltd. 2003
Published: 31 March 2003
Serum retinol concentrations are known to decline prepartum in cows. The cause of this decline is unknown, although it does not appear to be associated with vitamin A intake. The importance of the peripartum decline in serum vitamin A to disease resistance is also unknown. The objective of this project was to determine in cows receiving a diet of adequate vitamin A concentration, the association of prepartum serum retinol concentration to the incidence of postpartum disease. In addition, the relationship of serum retinol concentration to the serum concentration of metabolites indicative of metabolic status was also determined.
One hundred-nine Holstein cows in a commercial dairy were studied. Blood samples were collected weekly starting three weeks prior to expected calving with the last sample collected in the week after calving. All samples were collected between June and August of 1999. All animals were receiving the same, totally mixed ration with dietary vitamin A concentration of 60,000 IU/kg dry matter. The first sample, the prepartum sample nearest to calving, and the postpartum sample were analyzed for serum concentrations of retinol, non-esterified fatty acids, beta-hydroxybutyrate, albumin, and cholesterol.
The mean collection times relative to calving for each analyzed sample were -15, -5.4, and 3.1 d. Mean serum retinol concentrations declined significantly (p < .05) from each sample to the next, with mean (and range) values of 225 (113–397), 181 (67–333), and 118 (296–39) nG/mL, respectively. Serum concentrations of NEFA increased (p < .05) from each sampling time to the next. Serum retinol and NEFA concentrations were correlated negatively (p < .01) at each sampling time with respective r values of -.32, -.53, and -.42. Weaker, but significant (p < .05) correlations were observed between serum retinol and serum beta-hydroxybutyric acid at the immediate pre-, and postpartum samplings. Other serum metabolite concentrations were not significantly correlated with serum retinol.
Overall morbidity among the study animals was 48% with the majority due to metritis (33%) and mastitis (16%). The association of metabolite concentrations with disease was assessed by logistic regression. Initial independent variables in the model included twining, parity, sex of calf, calving difficulty, and the individual metabolite concentrations. Low serum retinol concentration at the sampling immediately prior to calving was a significant risk factor for overall postpartum morbidity (p < .05). No other independent variable entered the model.
I conclude that peripartum serum retinol concentrations are highly variable among animals, even on the same diet. Serum retinol concentration appears to be affected by general metabolic status, especially by energy status. The negative association between prepartum retinol concentration and post-partum disease might be due to insufficient delivery of vitamin A to tissues; however, low serum retinol may be general sign of metabolic stress and thus associated only indirectly with disease risk.
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