Modern reindeer dairy farming - the influence of different milking regimes on udder health, milk yield and composition

The purpose of the study was: (1) to test if the reindeer mammary gland (udder) could tolerate regular long-term machine milking, (2) to record milk yield of reindeer exposed to regular long-term machine milking and (3) to document changes in milk composition through a 3 months experimental period (July, August and September 1999). Adult female reindeer were allotted to four groups of four. Treatments were: Group 1, milked once per week, 6 h after separation of calves (control); Group 2, two milkings per day, no calves at foot; Group 3, as for Group 2 with a pre-milking oxytocin injection (i.m. 10 IE); Group 4, milked once per day, 6 h after separation of calves. Vacuum pressure was set to 25 kPa, pulse rate to 100 pulses/min with a suckling: massage ratio of 60:40. Somatic cell count (SCC), a measure of udder health, stabilized below 150,000 cells/ml in all groups, indicating that udder health was not affected by long-term regular machine milking. Average milk yield for Group I was 50 g/6 h, whereas a yield of 380 g per day was achieved for Group 3 (no nursing and injected with oxytocin). Milk yield of Group 3 was four-fold higher than Group 2 (90 - per day), which was milked twice daily but had no nursing and no injections of oxytocin. Separation of calves for 6 h before daily milking (Group 4) yielded 35 g. Based on the effectiveness of oxytocin, we conclude that milk letdown mechanisms are critical for effective emptying of the udder. A treatment reversal trial was conducted for a week late in the experimental period: for Group 3 mean daily milk yield when injected with saline although lower than the yield with oxytocin was greater than Group 2 which showed a 10-20% increase due to oxytocin; the 6 h mean milk yield of Group 4 when injected with oxytocin, was six-fold higher (215 g versus 35 g). We conclude that: (a) oxytocin is effective in all treatments, (b) oxytocin condition induced emptying of the mammary gland, (c) nursing contributes to maintenance of milk production, and (d) in absent of suckling or oxytocin milking twice daily with 6 and 18 h intervals is inadequate for maintaining milk secretion and may induce involution of the mammary elands. Milk dry matter content averaged about 25% (12% fat, 9% protein and 3% lactose) and increased slightly with stage of lactation, as a result of increased fat and protein concentration. (C) 2002 Published by Elsevier Science B.V.