Small Ruminant Research 121 (2014) 188–192 Contents lists available at ScienceDirect Small Ruminant Research jou rn al h om epa ge : w ww.elsevier.com/locate/smallrumres Influence of live weight, sex and type of birth on growth and slaughter characteristics in early weaned lambs Miroslav Simeonov a,∗ , Nikolai Todorov b , Krym Nedelkov b , Atanas Kirilov a , David L. Harmon c a Research Institute of Forage Crops, Pleven 5800, Bulgaria b Trakia University, Stara Zagora 6000, Bulgaria c Department of Animal & Food Science, University of Kentucky, Lexington 40546-0215, USA a r t i c l e i n f o Article history: Received 8 June 2014 Received in revised form 4 September 2014 Accepted 8 September 2014 Available online 18 September 2014 Keywords: Lamb Live weight at birth Growth Sex Type of birth Live weight at weaning Age at weaning Carcass yield Carcass quality a b s t r a c t The aim of the present study was to analyze live weight and growth data from birth to a live weight of 24–26 kg in early weaned lambs. The growth in the different age periods was determined on the basis of live weight changes for 152 lambs from the Blackhead Pleven breed. The results showed that the single lambs with a higher live weight at birth grew faster, but for twins there were no differences (P > 0.05). The difference in live weight was largely related to sex and type of birth. During the first 14 days of the suckling period the growth of lambs depended mainly on the amount of suckled milk. The male lambs grew faster than females after weaning. The lambs born as twins or singles placed under the same conditions of feeding and management did not differ in daily growth after weaning. Differences in live weight of lambs at birth and at weaning time were apparent until lambs reached 25 kg live weight. Correspondingly, this led to an increase of 5–10 days to reach 25 kg live weight of the lambs weaned at less than 9–11 kg and under 19–21 days, compared with the older lambs or born or lambs weaned at heavier live weights. The live weight from 7 to 11 kg and age from 17 to 28 days of weaning did not affect daily gain after weaning. However, all lambs have relatively low daily gain during the first week after weaning (about 50–60% of expected) and during the second week (about 60–70% of expected gain). © 2014 Elsevier B.V. All rights reserved. 1. Introduction It is generally accepted that at birth male lambs have higher live weights than females, but there is equiv- ocal opinions about the influence of the sex on the growth rate. According to Daskiran et al. (2010), the weight was higher throughout the whole experimental period (from birth up to 198 days of age) for male lambs versus female born as singles. Idris et al. (2010) pointed ∗ Corresponding author at: 89 General Vladimir Vazov Str., Pleven 5800, Bulgaria. Tel.: +359 878 632 156; fax: +359 64 805 881. E-mail address: msimeonov78@abv.bg (M. Simeonov). out that the female lambs were born with lower live weight than males, but this had no effect on their growth rates. Similar results were observed by others (Ali et al., 1999; Boujenane and Kansari, 2002). Other researchers (Mavrogenis, 1996; Kumar et al., 2008) have reported that male lambs from different breeds and at any age had higher live weight and better growth performance than females. The reasons for the higher growth rate of male lambs were the sex hormones (Fahmy et al., 1969) and faster skeletal development than in females (Abbas et al., 2010). However, in the experiment of Manso et al. (1996) female lambs were born with lower live weight but after weaning at 37 days of age, they grew faster than males. http://dx.doi.org/10.1016/j.smallrumres.2014.09.005 0921-4488/© 2014 Elsevier B.V. All rights reserved.