Artificial Lighting During Winter Increases Milk Yield in Dairy Ewes

• Published in: Journal of dairy science Vol. 91; no. 11; pp. 4238 - 4243
• Main Authors: Morrissey, A.D., Cameron, A.W.N., Tilbrook, A.J.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.11.2008; American Dairy Science Association; Am Dairy Sci Assoc
• Subjects: animal housing; Animal productions; Animals; Biological and medical sciences; blood chemistry; body condition; Body Weight; dairy animals; dairy ewe; dairy protein; ewe milk; ewes; Female; Food industries; Fundamental and applied biological sciences. Psychology; Housing, Animal; Lactation - physiology; lactose; Lighting; Milk - chemistry; Milk - secretion; Milk and cheese industries. Ice creams; milk composition; milk fat; milk yield; parity (reproduction); Photoperiod; prolactin; Prolactin - blood; seasonal variation; Seasons; Sheep - physiology; Terrestrial animal productions; Time Factors; Vertebrates; winter; Australia; photoperiod; milk yield; dairy ewe; Dairy animal; Winter; Lighting; Dairy industry; Increase; Photoperiod; Milk production
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2007-0918

In Australia, the supply of sheep milk is reduced during the winter. Housing dairy animals under lights during winter is a simple technique to increase milk yield; however, it is difficult to predict the magnitude of this increase in dairy ewes, because there are few corroborating data. We studied 220 East Friesian crossbred ewes (50 primiparous and 170 multiparous ewes, respectively) that lambed in April to May 2007 (late autumn, southern hemisphere) and were weaned from their lambs within 24h of parturition and milked exclusively by machine. These ewes were ranked according to their milk production, and ewes producing ≥1,000mL/d of milk were allocated to 1 of 2 groups. One group of ewes was kept indoors under a long-day photoperiod (16h of light), whereas the other group was kept indoors under a naturally declining day length. Ewes were maintained under these conditions for 8 wk. Milk yield was measured twice weekly, and ewe weight and condition were measured at weekly intervals. From a subset of ewes (n=20 per group), milk samples were collected twice weekly at the morning milking to measure milk lipid, protein, and lactose, and blood samples were collected once a week to measure plasma prolactin concentrations. Mean daily milk yield was analyzed as a percentage of preexperimental milk yield because the milk yield of ewes housed under the long photoperiod was lower than that of ewes under a declining day length when the treatments began. Thus, the ewes under a long photoperiod yielded 91.7% of their starting yield by wk 8 of treatment, whereas ewes under a declining day length yielded 76.25% of their initial value (LSD=5.1), and this divergence in milk yield was apparent by wk 2 of treatment. Mean plasma prolactin levels were greater in ewes housed under the long-day photoperiod (n=20) compared with control ewes (n=20) at wk 6 (168±27 vs. 72±19ng/mL, respectively), wk 7 (125±28 vs. 37±7ng/mL, respectively), and wk 8 of the experiment (132±35 vs. 31±7ng/mL, respectively). The composition of the milk was similar between the groups at each time point, and milk from these ewes (n=20 per group) contained, on average, 6.1±0.05% lipid, 4.8±0.02% protein, and 5.4±0.01% lactose (n=309 samples). We concluded that ewes increase milk production in response to being housed under a long-day photoperiod during winter.