The influence of dietary concentration of amino acids on protein and energy utilization in growing rats and piglets 3. diets of high biological value but with different protein concentrations

Eggum, B.O.; Chwalibog, A.; Danielsen, V.

Journal of Animal Physiology and Animal Nutrition 57(1): 52-64

1987


ISSN/ISBN: 0931-2439
DOI: 10.1111/j.1439-0396.1987.tb00006.x
Accession: 006696402

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Abstract
Four diets with decreasing protein concentration from 26.8, 26.6, 23.1 to 19.5% in DM were prepared. Diet 2 (26.6%) was diluted with maize starch at two levels to obtain a protein concentration of 23.1 and 19.5% in Diet 3 and 4 respectively. Based on earlier experiments in the same series efforts were made to meet the dietary requirements of lysine, methionine + cystine and threonine with natural food sources. Protein quality was tested in balance experiments with growing rats and piglets and in a separate growth trial with piglets. The balance experiments with pigs included both nitrogen and energy balances while only nitrogen balances and digestible energy were measured in the rat experiments. Tested at a constant protein level with rats the biological value varied from 78.7% in a traditional diet for piglets (Diet 1) to 90% in the other diets composed in a more untraditional way. Digestibility of both protein as well as energy was the same for all diets and at the same level for both rats and pigs. In the balance experiments with pigs it could be seen that daily nitrogen deposition was highest in pigs given Diet 2 with 26.6% protein and slightly lower when given Diet 3 with 23.1% dietary protein. Pigs on Diet 2 also had the highest daily gain but the frequency of diarrhea was significantly lower in pigs on Diet 3 and 4, i.e. with a lower dietary protein content. The results from energy metabolism showed that retained protein energy was lowest in pigs given Diet 4 with relatively smaller differences between the other groups. Pigs on Diet 3 had the lowest heat production and thus the highest energy retention with relatively more energy retained in the fatty tissue than pigs on Diet 1 and 2. Based on all the applied criteria in the present study it is concluded that the protein content and quality of Diet 2 are very close to meet the requirement of essential amino acids for fast growing piglets in the weight range 8 to 20 kg. However, due to significant digestive disturbances in pigs on Diet 2 a protein concentration intermediate to the levels in Diet 2 and 3 is recommended, i.e. 25% of DM. Values for lysine, methionine + cystine and threonine requirements are given in a separate table. By comparing data from rats and pigs obtained in all three experiments in the same series it could be seen that protein- and energy digestibility was not significantly different between these two animal species. Furthermore, a relationship between daily N-retention in piglets and utilizable protein in rats could be described by the following regression: RN in pigs, g/day = 0813 .times. UP (%), rats.

The influence of dietary concentration of amino acids on protein and energy utilization in growing rats and piglets 3. diets of high biological value but with different protein concentrations