The effects of milking frequency on insulin-like growth factor I signaling within the mammary gland of dairy cows

Margerison, Jean; Murney, R.; Stelwagen, K; Wheeler, T.T.; Singh, K.

Abstract

In dairy cows, short-term changes in milking frequency (MF) in early lactation have been shown to produce both an immediate and a long-term effect on milk yield. The effect of MF on milk yield is controlled locally within mammary glands and could be a function of changes in either number or activity of secretory mammary epithelial cells (MEC). Insulin-like growth factor I (IGF-I) signaling is one candidate factor that could mediate these effects, as it can be controlled locally within mammary glands. Both MEC number and activity can be affected by IGF-I signaling by activating the phosphoinositide 3-kinase (PI3K)/Akt and extracellular-signal-regulated kinase (ERK)1/2 pathways. To investigate the relationship between MF and IGF-I signaling, udder halves of 17 dairy cows were milked either 4 times a day (4×) or once a day (1×) for 14 d in early lactation. On d 14, between 3 and 5 h following milking, mammary biopsies were obtained from 10 cows from both udder halves, and changes in the expression of genes associated with IGF-I signaling and the activation of the PI3K/Akt and ERK1/2 pathways were measured. The mRNA abundance of IGF type I receptor, IGF binding protein (IGFBP)-3, and IGFBP-5 were lower following 4× milking relative to 1× milking. However, the mRNA abundance of IGF-I was not affected by MF. Both IGFBP3 and IGFBP5 are thought to inhibit IGF-I; therefore, decreases in their mRNA abundance may serve to stimulate the IGF-I signal in the 4×-milked mammary gland. The activation of PI3K/Akt pathway was lower in response to 4× milking relative to 1×, and the activation of the ERK1/2 was unaffected by MF, suggesting that they do not mediate the effects of MF.

Citation

Margerison, J., Murney, R., Stelwagen, K., Wheeler, T., & Singh, K. (2015). The effects of milking frequency on insulin-like growth factor I signaling within the mammary gland of dairy cows. Journal of Dairy Science, 98(8), 5422-5428. https://doi.org/10.3168/jds.2015-9425

• Journal Article Type: Article
• Acceptance Date: Apr 22, 2015
• Online Publication Date: Jun 11, 2015
• Publication Date: 2015-08
• Deposit Date: Aug 3, 2017
• Journal: Journal of Dairy Science
• Print ISSN: 0022-0302
• Electronic ISSN: 1525-3198
• Publisher: American Dairy Science Association
• Peer Reviewed: Peer Reviewed
• Volume: 98
• Issue: 8
• Pages: 5422-5428
• DOI: https://doi.org/10.3168/jds.2015-9425
• Keywords: milking frequency, mammary, milk synthesis, cell signaling
• Public URL: https://nottingham-repository.worktribe.com/output/1115883
• Publisher URL: https://www.journalofdairyscience.org/article/S0022-0302(15)00411-7/fulltext
• PMID: 26074231