Breeds of cattle are distributed in the world and are much vital farm animals in Kurdistan Region-Iraq as well as other parts of the world. In this species, a significant attention has been received in growth performance and carcass characteristics studies since last two decades because of their high economic and social values (Sutarno and Setyawan, 2015). On the other hand, there is still incomplete information regarding understanding of the quality of beef meat, body size measurements and weight gain in different species as well as in different rearing periods.
Carcass characteristics, weight gains are of much important economics to cattle producers. There are widely differences between types of cattle breeds in slaughter age and weights based on how sharply they mature that is characterized by fat lying down at a finishing fattening period (Phillips, 2018). Generally, da Costa et al., (2019) stated beef, which produces longer carcasses lead to a poorer conformation as well as a higher fat level in their carcass. On the other hand, it is not case for some small breeds. Differentiations in the carcass yields which are connected to the composition of genetic and the differences of body size that is inherent variations and these are attributed to sex, nutrition and slaughter endpoints (Bureš and Bartoň, 2012).
Body measurements might serve as vital chosen considerations; the production of calves could be better estimated compared to other production properties (Bene et al., 2007). The high heritability can be relatively observed in body size measurements (Kamprasert et al., 2019). Nian et al. (2017) reported that weight gain is positively related to beef body weight, which has a high growth rate, produce more size of muscle with a more glycolytic activity that is probably to favour meat ageing as well as thus, tenderness that is the main reason in the consumer’s meat preferences. In order to be successful in maximizing the amount of beef production, breed selection is necessary to be considered in cattle.
The major local cattle breeds in Iraq are the Rustaqi, Sharabi, Kurdi and Jenubi and there are some commercial cross breeds have been introduced over the years, including Holstein-Friesian and Hereford and Jersey (Alshawi et al., 2019). Sharabi breed is one of the varieties of domestic cattle in south and north of Iraq. In general, this species lives in Tigris valley and in North of Mosul. The average live body weight and wither height of Sharabi males is about 400 kg and 119 cm, respectively. Sharabi breed is black colour. Its male has small horns. Rustaqi breed lives around Hillah and Bagdad. The average live body weight of males is about 450 kg and its average daily gain is about 688 g. Rustaqi breed is brown colour and light tan. Male Rustaqi has small horns. Karadi or Kurdi breed lives around Kurdistan region. The average live body weight of males is about 300 kg and its average daily gain is about 379 g. Kurdi breed is black colour and light markings and its main use is meat. Jenubi breed lives south eastern and central Iraq. The average live body weight of males and wither height is about 325 kg and 125 cm, respectively and its average daily gain is about 557 g (Magid et al., 2003).
In a marketing system, the viability of the beef cattle industry depends on the ability to produce a high quality, consistent end product. This can be achieved through a clear understanding of lean and fat growth in various breeds of feedlot cattle. Thus far, there is a dearth of information on this topic, not only in number but also in scope, because they have involved a single Iraqi breed. Consequently, the aim of this study was to compare growth performance and carcass traits of calves of five different cattle breeds at two different rearing periods.