Effects of nutrient restriction on mammary cell turnover and mammary gland remodeling in lactating dairy cows

Abstract

The aim of this study was to investigate the effects of a severe nutrient restriction on mammary tissue morphology and remodeling, mammary epithelial cell (MEC) turnover and activity, and hormonal status in lactating dairy cows. We used 16 Holstein × Normande crossbred dairy cows, divided into 2 groups submitted to different feeding levels (basal and restricted) from 2 wk before calving to wk 11 postpartum. Restricted-diet cows had lower 11-wk average daily milk yield from calving to slaughter than did basal-diet cows (20.5 vs. 33.5 kg/d). Feed restriction decreased milk fat, protein, and lactose yields. Restriction also led to lower plasma insulin-like growth factor 1 and higher growth hormone concentrations. Restricted-diet cows had lighter mammary glands than did basal-diet cows. The total amount of DNA in the mammary gland and the size of the mammary acini were smaller in the restricted-diet group. Feed restriction had no significant effect on MEC proliferation at the time of slaughter but led to a higher level of apoptosis in the mammary gland. Gelatin zymography highlighted remodeling of the mammary extracellular matrix in restricted-diet cows. Udders from restricted-diet cows showed lower transcript expression of α-lactalbumin and kappa-casein. In conclusion, nutrient restriction resulted in lower milk yield in lactating dairy cows, partly due to modulation of MEC activity and a lower number of mammary cells. An association was found between feed restriction-induced changes in the growth hormone-insulin-like growth factor-1 axis and mammary epithelial cell dynamics.

Caracterização eletroforética de proteínas e estabilidade do leite em vacas submetidas à restrição alimentar

“…A restrição de 30% do aporte energético em vacas confinadas, no entanto, não reduziu sua produção leiteira, o que pode estar relacionado a seu avançado estádio lactacional, já que essas vacas se encontravam com mais de 230 dias de lactação. Isso pode ter causado diminuição na capacidade de resposta das vacas à alimentação, pela redução no número de células epiteliais mamárias e pelo aumento da taxa de apoptose (Capuco et al, 2001), observada em vacas sob restrição alimentar (Dessauge et al, 2011).…”

“…Guinard-Flamend et al (2007) observaram que restrição alimentar de 30% reduziu o percentual de caseína, mas não alterou o percentual de soro-proteínas lácteas. Dessauge et al (2011) observaram menor expressão da transcrição de α-lactoalbumina e κ-caseína, em vacas submetidas à restrição alimentar.…”

Biosynthesis of milk fat, protein, and lactose: roles of transcriptional and posttranscriptional regulation

“…The expression of LALBA increases upon treatment with a cocktail of lactogenic hormones (i.e., insulin ϩ hydrocortisone ϩ prolactin ϩ 17␤-estradiol or growth hormone), as observed in mouse and bovine mammary cells in vitro (105,199). The expression of LALBA is also induced by increased milking frequency in bovine and caprine (21,154) and by the AA Lys and Met in primary bovine mammary cells (155), but it is decreased by mastitis in dairy cow and yak (126,150) and by feed restriction in the cow (62). It is well established that the promoter region of LALBA contains a STAT5 binding site, and the presence of STAT5 is essential for the expression of LALBA in mouse (178,245).…”

Low‐quality rice straw forage increases the permeability of mammary epithelial tight junctions in lactating dairy cows

“…Approximately 800 mg of samples were collected with sterile surgical scissors and then quickly washed 20 times in ice‐cold phosphate‐buffered saline (PBS). For each cow, mammary samples were collected from the rear udder at the middle section in small aliquots . A portion of each tissue sample was immediately frozen in liquid nitrogen and stored at −80 °C until it was used for RNA extraction.…”