The flow and composition of lymph from the mammary gland in merino sheep.

Abstract

An investigation has been made of the flow and composition of lymph collected from the mammary lymph duct of lactating and dry merino ewes. Lymph flowed at the rate of 20–40 ml./hr. in ewes in early lactation and 2–6 ml./hr. in dry ewes. The rate of lymph flow was highest in those ewes producing the most milk. Maximum rates of flow of 50–180 ml./hr. were recorded for short periods of time in lactating ewes when they were suckled or when they were milked. In lactating ewes, the mammary lymph ducts contributed up to 20–30 per cent of the total thoracic duct lymph flow and up to 10–20 per cent of the total thoracic duct lymphocyte output per day.In general, the composition of udder lymph resembled lymph collected from areas such as the head and neck and limbs. In lactating ewes there was a large plasma‐lymph concentration gradient for both unesterified fatty acids and triglycerides and this suggested that these substances were being utilized by the mammary gland.Estimates have been made on the size of the interstitial fluid pool drained by the mammary lymph duct in lactating and dry ewes. Values of 100–220 ml. for ewes in early lactation and 20–60 ml. in dry ewes are reported. These findings are discussed in relation to the exchange of substances between the plasma and the mammary gland during the synthesis and secretion of milk.