Effect of Ambient Temperature on Daily Milk Yield and Blood Flow to the Mammary Gland in Lactating Goats Treated With Growth Hormone
Keywords:
Physiology, Animal, Caprine, Mammary GlandAbstract
The study was done with the objective of studying the effect or high temperature on the mammary gland production in terms or its blood supply and synthetic capacity. Growth hormone was injected to see whether high temperature has an interaction with the galactopoietic effects of the hormone in the mammary gland. Eight, one year old goats in their 6th week of lactation (1st lactation) were put into two climatic chambers, four in a chamber at 12°C and four in a chamber at 30°C. After four weeks of exposure to their respective temperatures two goats in each chamber were injected with bovine somatotropin (BST) daily for fifteen days. Daily milk yield was recorded. Blood flow rate was calculated from velocities measured using the Doppler Ultrasound Technique. Milk yield in goats at 30°C was 78% of milk yield of goats at 12°C at all times. With BST treatment milk yield increased by 9% and 13% at 12°C and 30°C respectively. Blood flow rate (L/day) to the mammary gland was in accordance to the milk yield with a blood flow rate: milk yield (CBF MY) ratio of 572 ± 166: 1 and 760 ± 180 : 1 at 12°C and 30°C respectively. With BST treatment the BF:MY ratio was 1059 ± 263 : 1 and 89 ± 38: 1 at 12°C and 30°C respectively. It is herewith concluded that blood flow to the mammary gland is a factor contributing to increased milk yield as it supplies the necessary nutrients for milk synthesis in the udder. The depressive effects of high ambient temperature can be counteracted by BST treatment as this increases milk yield not only through increased blood flow but also increased efficient nutrient extraction and utilization by the mammary gland cells for milk synthesis
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