Abstract
The aim of this study was to evaluate the effects of repeated oronasal administration of lipopolysaccharide (LPS) on milk composition and the overall productive performance of dairy cows. One hundred pregnant Holstein dairy cows were randomly assigned to two treatment groups (n = 50). 30 cows out of 100 were selected for intensive sampling (n = 15) starting at 28 d before parturition. Cows were administered orally and nasally with 2 and 1 mL of saline solution, respectively (control), or saline solution containing 3 doses of LPS from Escherichia coli 0111:B4 as follows: 1) 0.01 μg/kg body weight (BW) on d ﹣28, 2) 0.05 μg/kg BW on d ﹣25 and ﹣21, and 3) 0.1 μg/kg BW on d ﹣18 and ﹣14. Daily feed intake and milk production were recorded for each cow during the first 28 d postpartum. Milk samples were obtained once per week and analyzed for various milk components. Overall, results indicated that treatment did not affect feed intake, milk yield, milk efficiency, fat content, fat yield, protein content, protein yield, lactose content, lactose yield, milk urea nitrogen (MUN), total solid contents, fat-corrected milk (FCM), and energy-corrected milk (ECM; P > 0.05). However, milk somatic cell count (SCC) tended to be lower in the treated cows (P eek interaction for milk energy (P = 0.03), and tendencies for FCM, ECM, lactose content, and milk efficiency (P
Highlights
The normal function of the bovine mammary gland is disrupted during microbial infections and by the harmful toxins that they release early post-partum [1]
Analysis of the overall data did not reveal any effect of week for milk lactose content (P > 0.05; Figure 5(b)), it reached the point of significance for milk lactose yield (P < 0.01; Figure 5(a))
The tendency for lower somatic cell count (SCC) in the treated cows in the present study suggests that oronasal administration of LPS has induced the humoral immunity which lowered proinflammatory mediators and prevented subsequent translocation of large amounts of LPS
Summary
The normal function of the bovine mammary gland is disrupted during microbial infections and by the harmful toxins that they release early post-partum [1]. Among the various harmful bacterial toxins lipopolysaccharide (LPS), a cell wall component of all Gram-negative bacteria (GNB), commonly known as endotoxin, has received much attention [1,2]. Rumen carries high loads of free LPS especially when cows are switched from the dry off period diets low in grain to high-grain diets early postpartum. The latter diets are known to cause sudden depression of ruminal pH with the onset of subacute ruminal acidosis and disrupting the balance of multi-species microbiota with a major shift towards GNB [5,6]. It is evident that rumen LPS translocates into the bloodstream and further into the mammary gland where it suppresses the functions of the mammary epithelial cells (MEC) [6,7]
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