Abstract
To understand how the capacity for fat metabolism (uptake, synthesis, modification) changes in rumen epithelia immediately before and after onset of lactation in dairy cows, rumen fluid Short Chain Fatty Acid (SCFA) concentrations and mRNA expression profiles of rumen epithelia was determined in twelve Holstein dairy cows at three weeks prior to calving (wk -3, n = 12), one week post calving (week +1, n = 12) and six weeks (week +6, n = 12) after calving. The diet was modified from a dry cow formulation to a lactating cow formulation immediately following parturition and raised the non-fiber carbohydrate level from 34 to 43%. All data was analyzed using the mixed procedure of SAS, with cows blocked by anticipated calving date and week of sampling as the repeated measure. Propionate, butyrate, isovalerate and valerate levels rose significantly following the diet change (p≤0.001), although acetate and isobutyrate levels were unchanged (p>0.05). Mean rumen pH also changed during the transition period (6.38 Vs 5.81 and 5.85±0.08; -3 Vs +1 and +6; p
Highlights
Management of transition cows can be found in several sources
Microarray analysis of total RNA from rumen epithelial biopsies revealed 1476 differentially expressed genes at a false discovery rate of 10%. These results were filtered for genes that were directly related to both the immune system and fat metabolism/homeostasis
As a result of low feed intake, circulating insulin concentrations are low and result in drastic reductions in lipogenesis through alterations in the control pathways that regulate them (Ji et al, 2012; Leroy et al, 2008), enabling more nutrients available for milk production. These changes can be effectively tracked by studying genomic changes in key metabolic pathways and so, relative changes in gene expression can be used as a tool to track energy status in the periparturient dairy cow
Summary
Management of transition cows can be found in several sources Louis Dionissopoulos et al / American Journal of Animal and Veterinary Sciences 9 (1): 36-45, 2014 the production of milk at the expense of normal body maintenance (Ingvartsen, 2006) These changes are hallmarked by clear reductions in body condition score and dry matter intake in the modern dairy cow, so it is clear that a massive mobilization of nutrients must be taking place which is orchestrated by an as yet unknown series of mechanisms (Adrien et al, 2012). As a result of low feed intake, circulating insulin concentrations are low and result in drastic reductions in lipogenesis through alterations in the control pathways that regulate them (Ji et al, 2012; Leroy et al, 2008), enabling more nutrients available for milk production These changes can be effectively tracked by studying genomic changes in key metabolic pathways and so, relative changes in gene expression can be used as a tool to track energy status in the periparturient dairy cow. The objective of the current study was to determine the magnitude and identification of genomic changes in the rumen related to nutrient (fat) homeostasis and energy availability
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