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The use of dietary crystalline aminoacids (AA) allows to meet specific AA requirements and adjust dietary AA profiles while reducing the crude protein (CP) content in the diet. Moreover, reducing the excess of dietary CP by including crystalline AA decreases catabolism of AA that are in excess of dietary requirements in lactating sows and reduces the excretion of N compounds to the environment. Therefore, the aim of the present study was to determine the optimal standardized ileal digestible (SID) CP level to maximize litter gain in high-yielding lactating sows when feeding reduced CP, crystalline amino acid-supplemented diets. For that purpose, a total of 520 Landrace × Yorkshire sows (with a ranging parity from 1 to 5) were allocated to 1 of 6 diets two days after farrowing, when litters were standardized to 14 piglets. All diets were formulated to meet or slightly exceed Lys, Met, Met+Cys, Thr and Trp Danish recommendations by using crystalline amino acids. Experimental diets contained 116, 126, 132, 138, 144, and 153 g SID CP per kg (as-fed). Sow body weight, back fat thickness and litter weight were recorded at litter standardization (d2) and at weaning. On a subsample of 72 sows (parity 2 to 4), milk samples were collected at day 3, 10 and 17 post-partum, and blood was sampled at day 10 and 17 post-partum.
As a result, litter size and average daily gain at weaning were not affected by the dietary CP content. Similarly, dietary CP did not influence milk contents of fat and lactose. Likewise, sow body weight and back fat thickness were similar across dietary treatments. Milk protein and milk Lys, among other essential amino acids in milk protein, were reduced at a SID CP concentration of 116 g/kg. Plasma concentrations of non-esterified fatty acids and creatinine were not affected by dietary treatment, but concentrations of plasma urea nitrogen were elevated as dietary CP content increased.
In conclusion, sows were able to maintain a high litter growth when fed reduced CP, crystalline amino acid-supplemented diets, with no repercussions on other parameters. However, it should not be recommended to feed the lactating sows less than 126 g SID CP/kg (as-fed), or else milk protein and AA concentration could be affected.
Hojgaard, C. K., Bruun, T. S., Strathe, A. V., Zerrahn, J. E., & Hansen, C. F. (2019). High-yielding lactating sows maintained a high litter growth when fed reduced CP, crystalline amino acid-supplemented diets. Livestock Science, 226, 40-47. https://doi.org/10.1016/j.livsci.2019.06.002
