Role of Changes in Physical and Chemical Properties of Milk in Determination of Lambing in Ewes

Abstract

Mammary gland around parturition time shows different changes as a function of dramatic physiological adaptations of the animal for the transition period; from late pregnancy to lactation [1][2][3]. Mammary secretion undergoes a sequence of changes in ewes close to lambing [4]. Indeed, the milk secreted during this period is identified as transit milk, which is characterized by the formation of the colostrum that is subsequently changed to mature milk [5,6]. Ruminant colostrum is a thick creamy yellowish colour with a mixture of lacteal secretion containing immunoglobulins and other serum proteins, vitamins, lactoferrin, fat, and minerals [7,8].Determining the time of parturition is important for handling pregnant animals failed to show signs of parturition or suffered from dystocia [9,10]. Although the normal pregnancy period in ewes is about 140-155 days, with some individual variation according to the breed [11], different methods can be used for determination of the onset of parturition, including breeding records, ultrasonography, hormonal profile, specific proteins, changes in animal behaviour, as well as changes in the mammary gland (wet/dry udder) [12]. Lambing in some ewes, however, could be potentially missed by the owners as flocks of sheep are generally grazed in open areas where animals usually are not frequently closely M AMMARY gland and its secretion around parturition show different changes. The objective of the study conducted here was to examine the changes in the physical and chemical properties of the milk before, during, and after lambing. A total of 40 local Iraqi breed ewes, 2 to 4 years-old, confirmed pregnant by B-mode ultrasonography was used in this study.Milk was collected from each study ewe at 3 consecutive times, (i) on day 135 of pregnancy, (ii) at the time of lambing, and (iii) on day 5 postpartum. Milk examinations included colour, consistency, density, specific gravity, chloride contents, pH, light transmittance percentage, and light extinction coefficient. Results indicated changes of colour and consistency during different study periods. Milk density and specific gravity decreased as ewes approached lambing time and started lactation. Milk pH was low at the time of lambing. Mean of light transmittance percentage became zero at the time of lambing and later. The light extinction coefficient increased at the time of lambing and later. In conclusion, although signs of parturition could be simply observed, changes in milk properties can prompt owners to closely observe ewes whether they have already lambed or not.