Effect of nutrient restriction on mammary cell turnover in lactating dairy cows
2010
Dessauge, Frederic | Lollivier, Vanessa | Cutullic, Erwan | Disenhaus, Catherine | Barbey, Sarah | Lemosquet, Sophie | Boutinaud, Marion
The aim of the study was to investigate the effects of nutrient restriction on mammary cellturnover in lactating dairy cows. We used 15 Holstein x Normande crossbred dairy cows,divided into 2 groups submitted to 2 feeding levels. From calving to wk 11 postpartum, thecows were fed a total mixed ration composed either of 55% maize silage, 15% alfalfa hayand 30% concentrate (High-group, N=7) or of 60% grass silage and 40% hay (Low-group,N=8). Cows were milked twice daily. Milk yield (MY) and composition were measured. After11 wk of lactation, cows were slaughtered and mammary glands were removed and weighed.The mammary DNA concentration was measured in order to measure the total amount ofDNA in the mammary gland and to estimate the total number of mammary cells. Expressionof proteins involved in proliferation and cell death were evaluated on mammary tissue byreal-time qPCR, Western Blotting and immunohistochemical staining. Low-group cows had lower 11-week average daily MY from calving to slaughter than High-group cows (20.5 kg/dvs. 34.5, P<0.001). At the mammary tissue level, the total number of mammary cells and thesize of the mammary acini were lower (-20% P<0.002, and – 55 % P<0.05, respectively) inthe Low- group compared to the High-group. Mammary cell proliferation or apoptosis didn’tseem to be modified at the time of slaughtering but a remodelling of the extracellular matrixwas observed.
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