14. Mammary blood flow and nutrient uptake

Abstract

Sow milk is the major source of nutrients for suckling piglets and taking into account the large litter sizes of our current sow genotypes, it is imperative to maximize nutrient use by the mammary gland. The amount of nutrients available to mammary tissue is dependent upon the concentrations of nutrients in blood and the rate of its flow to the lactating glands. Nutrient availability to the udder may be estimated by measuring mammary arteriovenous differences, and mammary blood flow can be measured either directly or via indirect calculations. For all these measures, mammary venous and arterial blood samplings are required and catheters must be inserted in mammary veins. Blood flow to the udder is influenced by numerous factors, such as litter size, time since feeding, postural behaviour, vasoactive substances, and ambient temperature; yet, the single most important effector of mammary blood flow is milk removal. Glucose represents 40 to 60% of the total carbon mass taken up by sow mammary tissue and its uptake by the mammary gland appears to be mediated by glucose transporter proteins. Other energetic precursors which are used by the mammary gland are triglycerides, phospholipids, acetate, propionate and lactate. The uptake of amino acids by sow mammary glands has been extensively studied and is affected by diet, stage of lactation, and milk demand. Recent data also showed that amino acid uptake is controlled by transporter proteins that channel amino acids intracellularly, and that these proteins are in turn affected by diet and physiological status. Data on mammary uptake of hormones are contradictory; yet, the endocrine involvement in the regulation of milk synthetic processes is evidenced by the presence of specific hormonal receptors in mammary tissue.

Effects of timing and size of meals prior to farrowing on sow and litter performance

“… Le Cozler et al (1999) observed sow arterial glucose concentration remained constant as time since birth of first piglet increased, and rapidly increased after the birth of the last pig until time of placenta expulsion. This may be due an increased demand of glucose as a precursor for lactose in milk synthesis once parturition is complete ( Farmer et al, 2015 ), or circulating hormones during parturition altering glucose regulation. Feyera et al (2018) demonstrated glucose and triglyceride extraction by the uterus increased 1.4- and 6-fold, respectively, during parturition compared with after parturition.…”

Lack of evidence of mastitis as a causal factor for postpartum dysgalactia syndrome in sows123

“…In addition, we saw no correlation between the LPS concentration in v. epigastrica and redness, warmth, hardness, and edema in the first 6 anterior glands. Moreover, no differences in LPS concentrations were detected between sows with and without PDS, indicating that increased inflammation was not induced by translocation of LPS from the udder to the bloodstream ( Farmer et al, 2015 ). These results are in line with previous studies indicating that predisposing factors other than bacterial infections must be present for PDS to develop ( Magnusson et al, 2001 ; Osterlundh et al, 2002 ; Gerjets et al, 2011 ; Kaiser et al 2018b ).…”

Regulation of fluid flow through the mammary gland of dairy cows and its effect on milk production: a systematic review

“…Milk precursors are digested in the gut, transported through the blood circulatory system, and finally absorbed by the MG. Nutrients accessible to the MG from the blood can interfere with the rate of MBF, which causes nutritional perturbation of MBF . A previous study suggested that insufficient availability of glucose decreased mammary plasma flow and decreased glucose uptake of the MG by 30% .…”