Document Type : Research Paper
Authors
1 Animal Science Research Department, Gilan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran.
2 Department of Animal Science, College of Agriculture and Natural Resources, Razi University, Kermanshah, Iran.
3 Animal Science Department, Golpayegan branch, Islamic Azad University, Golpayegan, Iran
Abstract
Objective: Castration is one of the management activities practiced worldwide in order to reduce aggressive behaviour, sexual activity and to facilitate management ease. Numerous studies have been conducted comparing production efficiencies and carcass traits of intact and castrated beef cattle and sheep. It has been agreed generally that castration causes less growth efficiency and produces carcasses with higher fat contents which results in increased proportion of saturated fatty acids. However, effects of castration on mentioned parameters in goats has been less investigated, despite the fact that goats genetically deposit less fat in their muscles with a more favorable fatty acid composition compared with other ruminants. Therefore, this research was conducted to evaluate the effects of castration on growth performance and carcass and meat quality attributes in Markhoz kids.
Method: Sixteen male Morkhoz kids (13.2±1.6 kg live body weight, 3 months old) were used to evaluate the effects of castration on growth performance, carcass and meat quality attributes and fatty acid composition of longissimus thoracis and semimembranosus muscles based on a completely randomized design with 2 treatments and 8 replicates. Kids were castrated using ring castration in the respective treatment one week before the beginning of the experimental period. During 119 days of feeding experimental diet (formulated to meet NRC recommendations for small ruminants), growth performance of kids were recorded individually. Then, all kids were slaughtered and enough samples of each muscle were collected from the left side of each carcass, vacuum-packed and frozen at −20°C until subsequent determination of meat quality attributes including shear force, cooking loss, colour, proximate composition and fatty acids profile. The value of pH24, percentages of drip loss and water holding capacity were determined immediately on the day after slaughtering.
Results: Morkhoz kids castration decreased average daily feed intake and daily weight gain and increased feed conversion ratio significantly (P<0.05). However, cold carcass percentage, back fat thickness and rib eye area were not affected by castration. Fat percentage of longissimus thoracis and semimembranosus muscles increased significantly in response to castration (P<0.05), but crude protein content of muscles was similar in intact and castrated kids. Meat quality attributes of mentioned muscles, including pH24, drip loss, water holding capacity and shear force were not affected by castration; however, cooking loss percentage in longissimus thoracis muscle decreased significantly by castration (P<0.05). L* and b* indexes of meat colour showed similar values in both muscles of intact and castrated groups, but the value of a* index was significantly lower in muscles of castrated kids (P<0.05). Castration had no significant effect on fatty acid composition of intramuscular fat in the longissimus thoracis muscle and only minor effects on the fatty acid composition of semimembranosus muscle were observed, including significant reduction in C14:1 cis and C18:3 cis3 fatty acids percentages (P<0.05).
Conclusion: Results showed that Morkhoz kids castration, in addition to diminution of growth performance and feed efficiency, increase fat content of muscles which is not a desirable change with respect to consumers’ health.
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