Considering the maximum protein deposition in carcasses of different sex and genetics is approximately 70 kg in weight, it can be deduced that, in market conditions in which such animals are slaughtered weighing more than 100 kg, there would be a need to maximize protein deposition in the initial growth phase if we consider that these animals exhibit compensatory deposition of protein in the carcass.
Based on these considerations, we established a research program that was conducted with pigs, male castrated, immunostained and female, under different environmental conditions, to evaluate nutritional strategy, with different digestible lysine intake, in order to explore this protein deposition characteristic, evaluating the total creation period, and not each separate stage, as is usually done. A total of eight (8) experiments were conducted in which animals started with a mean age of 63 days, (+ - 24 kg), and remained in the experiment for 100 days, which were divided into three (3) periods corresponding to 40 - 30 and 30 days.
In all experiments, five treatments and eight replications were used, with two animals per bay, as experimental unit. The treatments corresponded to nutritional plans, which ranged from 0.90% -1.00% -1.10% - 1.20% and 1.30% digestible lysine (ld) for the first 40 days , and in the next two 30-day periods, lysine levels decreased by 0.10% in each treatment, so the first treatment corresponded to 0.90% -0.80% - 0.70% of ld and the fifth corresponded to 1.30% -1.20% -1.10% of ld.
The animals were weighed at the beginning of the experiment, that is, at 63 days of age and at the end of each established period, that is, at 103 (40 days), 133 (70 days) and 163 (100 days). In all experiments, without exception, although when the first 40 days were evaluated, the levels of ld that provided the best performance results corresponded to 1.30%, 1.20% and 1.10% of ld respectively, for females and castrated males, when the total period of 100 days was considered, there was no difference in performance when the animals that received the treatments that provided the best results in the initial period of 40 days (1.30 %, 1.20% or 1.10% ld) with those who received the treatment corresponding to the lowest ld level (0.90% ld).
In addition to performance, the amount of meat in the carcass, which was evaluated in all animals in the refrigerator, also did not vary among treatments. In the last two experiments, which we conducted with castrated males, in the winter and summer periods, treatments ranged from 0.80% to 1.20% of ld in the first 40 days, and similarly to previous experiments in both periods After 30 days, lysine levels decreased by 0.10%.
The results were similar to the previous ones, that is, in the first 40 days, the best data were obtained at the level of 1.10% ld, and in the total period there was no difference in the performance and quantity of meat in the carcass of the animals, when compared the treatment corresponding to 1.10% -1.00% - 0.90% with that of 0.80% -0.70% -0.60% 1d, although in the first period the level of 1.10% has resulted in better performance.
Additionally, in the latter two experiments, the quality of the meat of the animals was evaluated, where it was found that the animals submitted to the treatment corresponding to the lowest sequence of ld (0.80% -0.70% -0.60%) presented higher quantity of fat in the meat that corresponded in average 30%. These experiments confirmed the possibility of producing pigs that are slaughtered weighing more than 100 kg with lower aminoacid intake, which evidently improves the production yield with a positive impact on the environment, reducing the pollutant load of the wastes.
With these experiments, it was evidenced that in conditions where pigs are slaughtered weighing over 100 kg, which is a market reality, establishing the nutritional demand per breeding stage, as is usually done, can overestimate the requirement of amino acids for maximizing the production efficiency. This makes it advantageous to determine the requirements based on the evaluation in the total period of production and to be able to exploit the compensatory deposition of protein of these animals once the phases are interdependent.