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Systems Approach to Evaluate Growth and Meat Production of Sheep under Two Production Systems
Abstract:
The growth and carcass performance of sheep reared under integration in the mature oil palm plantation and feedlot system were studied using a systems approach. Simulation models of the growth and carcass of the Dorset x Siamese Long Tail (DSLT) and Dorset x Malin (Dmalin) sheep were described.
To construct simulation models to evaluate a production system, a series of studies were carried out. Firstly, the dry matter intake, energy intake and energy requirements of sheep were determined. Secondly, the live weight changes, carcass, muscle, fat and bone weight changes were measured. Thirdly, the models were constructed to describe the growth and carcass performance of sheep under the two production systems. Validations of the simulation models were done by comparing the simulated data with the actual data of live weight, carcass, and its tissue weight.
The study on sheep reared under integration with mature oil palm plantations (9- 21 years old) was conducted at the Sungai Seraya Plantation, Far East Holdings Bhd, Pahang, Malaysia. Under the oil palm plantation production system, the sheep was grouped into pre-weaning and post-weaning sheep. The pre-weaning lambs were kept in the sheds and fed with natural herbage ad libitum through a cut and carry system while concentrate supplementation was given at the rate of approximately 80 grams/ head/day from 4 weeks of age to 2 months and then increased to 100 grams/head/day at 4 months old. The weaned lambs and ewes were allowed to graze together under the oil palm canopy without any concentrate supplementation. The grazing period of sheep under the mature oil palm canopy was about 5 hours a day. During the study, the botanical composition of herbage under the oil palm canopy, dry matter yield, dry matter herbage intake, growth and carcass performance of sheep were measured.
The study on sheep reared in the feedlot system was conducted at the Department of Animal Science, Universiti Putra Malaysia. The sheep used in this study were selected from the same flock used in the first study. During the study, the sheep were fed Guinea grass (Panicum maximum cv. Common Guinea) ad libitum and 2 percent live weight of concentrate supplementation. Parameters determined in this study were feed intake, live weight change, and carcass composition.
The study indicated that within 120 days of the experimental period, the DSLT and DMalin sheep reared in the feedlot system grew at the rate of 103.2 grams per day, while the grazing sheep in the mature oil palm canopy grew only 43.3 gramsper day (p < .01). Although the sheep in the feedlot system had a similar DM intake per metabolic weight with those in the integration system, the fattening sheep had a higher MEI (metabolisable energy intake) per metabolic weight than the grazing sheep (0.71 vs. 0.42 JMJ ME/kg LW0.75/day; p < .01).
In terms of carcass performance, the sheep in the feedlot system had better carcass weight gains than the sheep in the mature oil palm plantation (1.4 kg vs. 6.8kg) (p < .01). The average carcass gain of the sheep in the feedlot and integration systems were 56.7 and 11.7 grams per day (p < .01), respectively. The sheep in the feedlot system had a significantly higher dressing percentage (% DP) than those in the mature oil palm plantation (50.1% vs. 45.4%) (p < .01) and displayed significantly higher muscle and fat but possessed a lower bone percentage than those under the integration system (p < .01).
The study revealed the sheep reared integrated with mature oil palm plantation without any concentrate supplementation received poor nutrition, particularly metabolisable energy intake, than the sheep reared under the feedlot system. This was due to the lower availability of green vegetation under mature oil palm plantation compared with the feedlot system. Although the sheep integrated under the mature oil palm canopy received enough metabolisable energy for their maintenance (MERm), they did not receive enough energy for the production. This was the reason why the growth and carcass performance of the sheep under oil palm plantation system were poorer compared to those in the feedlot system.
Simulation models were constructed based on the net energy retained in the body, tissue weight changes and tissue gains, determined from the experiments. After validation, the study indicated that the simulated data of the body weight, carcass, and its tissue weight were similar to the actual data. Thus, the simulation models that estimated the growth and carcass performance of the DSLT and Dmalin sheep reared under the oil palm plantation and feedlot systems could be used to evaluate the reallife sheep rearing under similar conditions.