Document Type : Research Paper

Authors

• Seyyed Saeid Mousavi ¹
• Hamid Amanlou ²

¹ Department, Zanjan Agricultural and Natural Resources Research and Education Center, AREEO, Zanan, Iran

² Department, Faculty of Agriculture, Zanjan University, Zanjan, Iran

Abstract

Keywords

• starting age
• feedlot
• slaughter
• Afshari male lamb

Main Subjects

• Animal Nutrition and poultry

Extended Abstract

Introduction

In the livestock industry, particularly in sheep farming, determining the appropriate age for fattening lambs is one of the key factors in optimizing meat production and enhancing economic efficiency. The Afshari male lamb, as one of the important sheep breeds in Iran, holds a special position in fattening due to its high growth potential, adaptability to environmental conditions, and desirable carcass quality. The appropriate age for fattening should be determined based on carcass characteristics, final weight, and meat quality to achieve maximum economic productivity and final product quality. This is because slaughter weight also influences carcass characteristics. Lambs slaughtered at higher weights typically exhibit better carcass quality. However, determining the optimal age for the start and end of the fattening period, in order to achieve maximum growth and carcass quality, requires a thorough examination of the physiological and growth characteristics of these lambs during the post-weaning period.

Material and method

24 male Afshari lambs were divided into four age groups (60, 90, 120, and 150 days) with average initial weights of 22.83 kg, 27.73 kg, 36.30 kg, and 42.55 kg, respectively, in a completely randomized design. The objective of this experiment, based on a previous study, was to achieve a slaughter weight of 50 kg in the shortest possible time.

Result

The results showed that the average slaughter age of the experimental groups differed significantly, with lambs fattened at 60 and 90 days of age having a lower slaughter age compared to the other groups (P < 0.05). The effect of fattening start age on weight gain was significant, with the 90-day group showing the highest daily weight gain (333 grams) (P < 0.05). There was a significant difference in dry matter intake among the experimental groups, with the lowest intake observed in the 60-day group (1.31 kg), which increased with age (P < 0.0001). As the fattening start age increased, the feed conversion ratio significantly increased, with the highest value in the 150-day group (7.72) and the lowest in the 90-day group (4.48) (P = 0.0003). Neck weight differed significantly among the groups, with values of 0.848 kg, 0.693 kg, 0.975 kg, and 0.770 kg for the first, second, third, and fourth groups, respectively (P < 0.0001). The weights of the shoulder, breast, thigh, and loin were similar among the groups and did not differ significantly. However, the weight of the tail fat was significantly higher in the 60- and 90-day groups compared to the 120- and 150-day groups (3.063 kg and 3.200 kg vs. 2.085 kg and 2.427 kg, respectively) (P = 0.0029). Hot carcass weight and cold half-carcass weight did not differ statistically, but the highest cold carcass weight was observed in the first group (60-day start, 26.683 kg), and the lowest was in the third group (120-day start, 23.933 kg). The weight of meat and bone in the cold half-carcass did not differ significantly among the experimental groups. Subcutaneous fat weight was significantly lowest at 120 days and highest at 90 days (P = 0.0152), while intermuscular fat weight in the cold half-carcass was similar among the groups (P > 0.05). However, total fat weight, including visceral fat, in the cold half-carcass differed significantly (P = 0.0500), being higher in the 60- and 90-day groups (5.218 kg and 5.300 kg, respectively) compared to the 120-day group (4.347 kg), with the 150-day group (4.626 kg) showing no difference from the other groups. The lowest slaughter age was observed in lambs fattened starting at 90 days, which was significant (P < 0.05). Overall, it can be concluded that the optimal fattening start age for male Afshari lambs, considering carcass composition and cost-effectiveness, is 90 days, with a starting weight of approximately 27 kg.

Conclusion

In the fattening-only period, the starting age of fattening at 90 and 120 days was superior to 60 and 150 days. Only lambs fattened from day 90, which had a complete weaning period and were fattened immediately, reached slaughter weight earlier than all treatments. For the starting age of fattening at 150 days, daily weight gain was lower throughout life. The use of pasture significantly reduced the dependence on finishing feed. Fattening lambs at an early age and its impact on the environment requires further research.

Author Contributions

Seyyed Saeid Mousavi: Conceptualization, Validation, Methodology, Software, Formal analysis,  Investigation, Writing - Original Draft, Project administration

Hamid Amanlou: Supervision, Formal analysis, Investigation, Writing - Review & Editing

All authors have read and agreed to the published version of the manuscript.

Data Availability Statement

The data supporting reported results are collected and used from published articles, to them we have referred in the manuscript.

Acknowledgements

The authors would like to thank all participants of the present study, especially the National Institute of Animal Sciences Research, the Agricultural and Natural Resources Research and Education Center of Zanjan Province, the Faculty of Agriculture of the University of Zanjan, and the sheep farm.

Ethical considerations

The study was approved by the Ethics Committee of Zanjan Agricultural and Natural Resources Research and Education Center. The authors avoided data fabrication, falsification, plagiarism,and misconduct.

Conflict of interest

The author declares no conflict of interest.