Comparative Growth Performance and Carcass Traits of Calves of Different Cattle Breeds Fed Pasture and Concentration

The aim of the current study was to explore growth performance and carcass traits using ultrasound measurements of calves of different cattle breeds under pasture and concentration feeding system. A total of 25 male cattle calves between the ages of 6 to 7 months with an average body weight of 162.37 ± 7.7 kg were fed two separate fattening trials for seven months (pasture and nishing period). Animals were divided into ve groups (ve of each breed): Kurdi, Rustaki, Jenoubi, Herford and Friesian crossbred. The average daily weight gain was similar (P > 0.05) for calves of different cattle breeds during growth (pasture) period, while these values were signicantly higher in Kurdi, Rustaki and Friesian crossbred calves during nishing period. The body size measurements were similar among calves of different cattle breeds. The highest increase in Longissimus muscle area and subcutaneous fat thickness was observed in Kurdi, Rustaki and Friesian crossbred calves. In conclusion, In conclusion, Kurdi, Rustaki and Friesian crossbred calves possess the promising potential for beef production under the barn rearing or nishing period.


Introduction
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 signi cant 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 nishing 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 ve different cattle breeds at two different rearing periods.

Materials And Methods
All animals received humane care according to the standard local guidelines. The local animal care and use committee of the College of Agriculture Engineering Sciences, Salahaddin University-Erbil, Kurdistan Region, Iraq approved the protocols for the current trial.

Animals and rearing conditions
The investigation was conducted on 25 calves of different cattle breeds bred purchased from different farms in Erbil city, Kurdistan Region-Iraq after weaning at approximately 6 to 7 months of age. The animals were assigned into ve groups: Group A, ve calves from the Kurdi breed; Group B, ve calves from Rustaki breed; Group C, ve calves from Jenoubi breed; Group D, ve calves from Herford crossbred and Group E, ve calves from Friesian crossbred. Before the trial all calves were weighed, properly tagged, and treated for internal and external parasites. Two separate fattening trials were conducted in seven months (three and four months, respectively). All calves were assigned to two rearing periods; pasture rearing (growth period) and barn rearing ( nishing period). In the pasture period, calves were reared on cereal crop residue and were offered concentrates daily for maintenance to consider the animal welfare regulations. All the experimental calves were gone out and fed ad libitum twice daily at 06:00 to 09:30 and 16:00-19:30 h by cereal crop residue. All the experimental calves rotationally grazed a separate area (12 ha) of cereal crop residue which included the straw of barley and wheat as well as some seeds of wheat and barley left after harvesting. Concentrates were offered in one feed each night in linear stainless troughs (0.5 m feed space per animal). In the nishing period, calves were housed together in a proper free-stall house (8 m x 23 m x 2.8 m) with a big stable (17 m x 27 m x 1.7 m). Throughout the second period of fattening, the calves were fed a mixed diet available ad libitum composed of 15% soya bean, 50% barley, 33% wheat bran, 1% salt and 1% limestone. The animals were subjected to seven days of adaptation to the experimental diet. Animals had ad libitum access to water during the whole experiment.

Weight and body size measurements
Data for each animal included initial weight (kg), average daily gain (kg), slaughter weight (kg), and body measurements (cm) which were recorded systematically. Individual calves weights were measured using a heavy duty scale with accuracy ±0.5 kg (initial weight) at the beginning and continued in each 15 days throughout the study. A daily gain during growth period was calculated between the initial weight at the beginning of study and weight at nal periods of feeding on cereal crop residue while average daily gain of nishing period was calculated between initial weight of fattening and nal weight of slaughter. An estimated total gain during the fattening period was calculated between the initial weight and at slaughter weight. Body measurements such as body length, height at withers, heart girth, chest depth and paunch girth were recorded at the beginning of the experimental and at 10 months of age and prior to slaughter using measuring stick and tape (Hauptner, Germany) when animals were standing as described in Ozkaya and Bozkurt (2008).

Carcass evaluation using ultrasound as a modern tool
Calves were ultrasonically scanned between the12th and 13th ribs two to three times for external fat thickness and longissimus muscle area using the Pie Medical Scanner 200 (PieMedical Equipment BV, Maastricht, The Netherlands) equipped with an animal science probe (ASP-18) and with a frequency of 3·5 MHz, 17.2 cm linear array transducer. The transducer was located laterally between the 12th and 13th ribs on the right side of the animal after the scanning site was determined by palpation. To establish good acoustical contact and avoid the presence of air bubbles between the probe and skin surface, the palpated area was cleaned, oiled using vegetable oil and curried until free from dirt and then re-oiled for optimum image quality.

Statistical analysis
The experiment followed a completely randomized design. Data obtained for all parameters were subjected to the generalized linear model (GLM) procedure using Statistical Analysis System package (SAS) version 9.1 software (SAS Institute Inc., Cary, NC, USA). Duncan multiple range test was used to test the signi cance of variance between the means of the studied parameters at signi cant level of p<0.05.The data in the tables are presented as mean ± standard errors of the mean (SEM).

Results And Discussion
Growth characteristics Growth as an important economic feature should be included in either breeding or nished cattle program (Hozáková et al., 2020). In this study, weights were recorded at the beginning and at the end of each fattening period. Despite the fact that calves came from deferent elds, there were no signi cant differences between breed groups in initial weight at the start of the fattening periods which is presented in Table 1. Furthermore, there was no difference between breed groups in the live body weight and average daily gains of the pasture group over the growing period. The lack of statistical differences might be due to a less stable growth rate of pasture calves which could be explained by that animal on pasture are exposed to changing climatic conditions in uencing feed intake and feed conversion e ciency (Velik et al., 2013). Inversely, the average daily gains over the nishing period and slaughter weight were signi cantly higher in Rustaki, Friesian crossbred and Kurdi calves compared to Jenoubi and Herford crossbred calves. The better performance of Rustaki, Friesian crossbred and Kurdi calves could be due to their comparatively better acclimatization to the area. Over the whole experiment, average daily gain differ (p<0.05) among different breeds of calves. The higher average daily gain was observed in Rustaki, Friesian crossbred and Kurdi calves. These results coincide with those of average daily gain through feedlot fattening period. Body measurements are important characteristics in beef cattle (Bene et al., 2007). They are often using to estimate animals' maturity and additional characteristics including live body weight. Furthermore, body dimensions can also serve as signi cant selective factors with a relatively high level of heritability (Hozáková et al., 2020). Details on body size measurements, body length, height at withers, heart girth, chest depth and paunch girth, at the beginning of the experiment, at the end of the growing period and at slaughter are given in Table 2

Muscle area and subcutaneous fat thickness
Ultrasound technology is a modern tool that can be utilized to accurately estimate carcass measurements in live animals such as subcutaneous fat thickness and Longissimus muscle area (Gupta et al., 2013). Consequently, the evaluation of subcutaneous fat thickness and muscle depth by ultrasonography could be shown differences in the deposition of subcutaneous fat and muscle throughout the production cycle.
Therefore, this kind of data is mostly handy for breeding animals that will not drive for slaughtering (Blanco et al., 2014). Muscle area and subcutaneous fat thickness were different at the end of the calves housing period, when Kurdi, Rustaki and Friesian crossbreds had signi cantly greater muscle area and subcutaneous fat thickness than Jenoubi and Herford crossbred calves (Table 3) but did not differ at the growing of the calves' rearing period. The differences between calves groups in muscle depth and subcutaneous fat thickness at the end of the nishing period were related to differences in the live body weight, as both variables were highly correlated (r=0.0.68 and 0.67 for muscle area and subcutaneous fat thickness, respectively; p<0.01).

Declarations
Funding: The authors received no nancial support for the research, authorship and publication of this article.
Con icts of interest: There is no con ict of interest declared by the authors.
Ethics approval: All methods and procedures employed in this study complied with the recommendations by the Animal Welfare and Ethics Board of Salahaddin University-Erbil (Kurdistan Region, Iraq).
Consent to participate: Not applicable.