The effect of the diversified signal of melatonin on milk yields in seasonally breeding sheep

Previous studies demonstrated that milk yields in sheep displaying strong seasonal sexual activity depend on the day length. The objective of the studies was to determine whether the introduction of melatonin in high pregnancy affects milk secretion in seasonally sheep. The studies were carried out on 60 Polish Longwool sheep. Sheep were allocated to three groups: Group I (n=20 – the control group, lambed in February), Group II (n=20 – a group of sheep lambed in June and kept under natural day-length conditions), Group III (n=20 – a group of sheep with melatonin implants injected six weeks before lambing, sheep lambed in June). Lambs were reared with mothers up to 56th day of their life. When lambs were weaned, ewes were milked mechanically twice a day up to the dry period. Once a month collective milk samples were drawn from six sheep from each group in order to determine the concentration of melatonin. Milk yields were subjected to individual checks every 10 days. The studies demonstrated that sheep lambed in February (Group I) displayed the highest milk yields in the milking period (37.8±8.1 l). The milk performance of the two other groups was lower and amounted to 30.2±9.4 litres in case of sheep lambed in June and to 29.2±7.6 litres in sheep with melatonin implants. The introduction of melatonin signal to produce a short-day condition in state of high pregnancy in ewes caused a drop of milk yields both in the period of lambs raising and during milking. Archiv Tierzucht 56 (2013) 93, 924-932 Received: 2 April 2013 doi: 10.7482/0003-9438-56-093 Accepted: 18 October 2013 Online: 5 November 2013 Corresponding author: Edyta Molik; email: [email protected] Biotechnology and Genomics Laboratory, Department of Swine and Small Ruminants Breeding, Agricultural University in Krakow, 30-059 Krakow, Poland © 2013 by the authors; licensee Leibniz Institute for Farm Animal Biology (FBN), Dummerstorf, Germany. This is an Open Access article distributed under the terms and conditions of the Creative Commons Attribution 3.0 License (http://creativecommons.org/licenses/by/3.0/). Open Access 925 Archiv Tierzucht 56 (2013) 93, 924-932