Plasma urea nitrogen as an indicator of amino acid imbalance in rabbit diets

López-Luján

Ródenas

et al. 2021

Self Cite

As a consequence of the genetic selection process in growing rabbits, there are currently fast-growing animals exhibiting an average daily gain that may exceed 45 g/d. The protein requirements of these animals, namely amino acid requirements, may differ from animals with low growth rates. The objective of this work was to evaluate growth performance, the coefficient of total tract apparent digestibility (CTTAD), the apparent ileal digestibility (AID) of amino acids and nutrient retention of fast-growing rabbits when they had access to a diet with high levels of amino acids and/or a diet formulated with current nutritional recommendations in a choice-feeding trial. To this end, two diets were formulated: the M diet following current nutritional recommendations for growing rabbits (including 8.1, 5.8 and 6.9 g/kg dry matter (DM) of total lysine, sulphur amino acids and threonine, respectively) and the H diet with higher levels of total lysine, sulphur amino acids and threonine (9.4, 6.6 and 7.8 g/kg DM, respectively). A total of 220 weaned rabbits, from a paternal line selected for the growth rate, had free access to the M diet, the H diet or both (MH) diets from 28 to 63 days of age. The CTTAD of DM, crude protein and gross energy from 49 to 53 days of age as well as the AID of amino acids of the diets at 63 days of age were determined. Protein, amino acids and energy retained in the empty body from 28 to 63 days of age were also registered. No significant differences in growth performance, CTTAD, AID and nutrient retention between dietary treatments were observed. However, animals fed the H diet showed a higher AID of cysteine (p < 0.05) and higher threonine retention (p < 0.05) compared to the M diet. As regards the choice-feeding trial, MH animals showed a higher feed intake of the M diet compared to the H diet (+8.61%; p < 0.001), and furthermore, more than 50% of the animals preferred the M diet throughout the experimental period (p < 0.05). Our results suggest that animals with high growth rates do not show significantly higher productive traits when fed the H diet compared to the M diet. As regards choice feeding, MH animals were capable of choosing their preferred diet, showing high intra-individual repeatability in preference for the M diet. It would be interesting to continue studying this behaviour of choice based on amino acid levels.

Section: Discussionsupporting

confidence: 92%

Do Growing Rabbits with a High Growth Rate Require Diets with High Levels of Essential Amino Acids? A Choice-Feeding Trial

López-Luján

Ródenas

et al. 2021

Self Cite

“…In the current study, PUN varied depending on the sampling conditions, being widely higher when blood samples were taken at 21:00h—i.e., 3 h after refeeding following a 10-h fasting period—than at 8:00h under ad libitum feeding. These results closely agree with those obtained by [ 14 ] for the same times and feeding managements, as a result of low feed intake during morning (when rabbits are practicing caecotrophy) and the overeating at evening after a fasting period—since the higher the protein intake, the higher the PUN [ 22 ], because of the catabolism of a greater amount of leftover amino acids. Additionally, the essential amino acid content in microbial proteins recycled through soft feces could improve the quality of dietary protein and reduce protein catabolism, although the amino acid supply from soft feces does not seem to be enough to alter the amino acid pattern of conventional diets [ 23 ].…”

Section: Discussionsupporting

confidence: 90%

“…At 08:00h on day 47, each collective cage was randomly switched to one of the 27 experimental diets, which was provided ad libitum. Following the methodology described by [ 14 ], at 08:00h on day 48 (after 24 h receiving the experimental diet), blood samples were taken from the central ear artery (1 mL in EDTA vials). Subsequently, the animals were subjected to 10 h of fasting and a second blood sample was extracted at 21:00h (3 h after refeeding).…”

Section: Methodsmentioning

confidence: 99%

“…A large number of studies showed that low levels of plasmatic urea nitrogen (PUN), which correspond to the amount of nitrogen in form of urea circulating in the bloodstream, could be related with performance in pigs [ 11 , 12 ] or in broilers. Furthermore, [ 13 , 14 ] have demonstrated that PUN could be an indicator to detect amino acid deficiencies in diets for growing rabbits and have proposed an appropriate methodology to determine it. Furthermore, an oversupply is costly and leads to an excessive nitrogen excretion with a potentially negative environmental impact [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Plasmatic Urea Nitrogen in Growing Rabbits with Different Combinations of Dietary Levels of Lysine, Sulphur Amino Acids and Threonine

López-Luján

Ródenas

et al. 2020

Self Cite

A total of 27 experimental diets were formulated starting from the same basal mixture, with a moderate content of crude protein and digestible energy (155 g and 9.86 MJ/kg of digestible matter (DM), respectively, both estimated). The contents of lysine, sulphur amino acids and threonine were variable. The first one, close to the current recommendations (Medium, M; 8.1, 5.8 and 6.9 g/kg DM for lysine, sulphur amino acids and threonine, respectively), and two other levels were on average 15% higher (High, H; 9.4, 6.6 and 7.8 g/kg DM for lysine, sulphur amino acids and threonine, respectively) or lower (Low, L; 6.7, 4.9 and 5.7 g/kg DM for lysine, sulphur amino acids and threonine, respectively). Diets were named with three letters, indicating lysine, sulphur amino acids and threonine levels, respectively. In total, 918 weaned rabbits (28 days old) were used (34 per diet). At weaning, animals were fed ad libitum with a commercial diet until day 46, day 47 each collective cage was randomly switched to one experimental diet. At day 48, blood samples were collected at 08:00h then the animals were subjected to 10 h of fasting and a second blood sample was extracted at 21.00h. At 08:00h, Pasmatic urea nitrogen (PUN) was higher with the L level of lysine (p < 0.001), unaffected by the level of sulphur amino acids and increased with the level of threonine (p < 0.001). At 21:00h, minimum PUN was observed with the MHL diet (14.72 ± 0.661 mg/dL). Taken into account the usual recommendations (established for a diet containing 11.3 MJ DE/kg DM, and then being 0.72, 0.51 and 0.61 g/MJ DE for lysine, sulphur amino acids and threonine, respectively), these results suggest that a diet containing more lysine and sulphur amino acids per energy unit (around 0.82 and 0.67 g/MJ DE) could better fit the growing rabbit requirements, although studies on the effects of such a diet on performance and protein retention are necessary.

“…Usually, amino acid requirements have been determined by using dose–response methods which show the response of the performance to ascending contents of the amino acid studies [ 23 ]. However, there exist other techniques, such as controlling the amount of amino acid (in blood, plasma or serum), or even plasmatic urea nitrogen, which corresponds to the amount of nitrogen in form or urea circulating in the bloodstream [ 24 ]; it could be related with performance in pigs [ 25 , 26 ]. Nitrogen from unused amino acids presents an energy cost for the animal—three ATP molecules for every nitrogen molecule excreted [ 27 ]—related to the urea cycle.…”

Section: Nutrition In Pigsmentioning

confidence: 99%

How Does Protein Nutrition Affect the Epigenetic Changes in Pig? A Review

Llobat

2021

Self Cite

Epigenetic changes regulate gene expression and depend of external factors, such as environment and nutrition. In pigs, several studies on protein nutrition have been performed to improve productive and reproductive traits. Indeed, these studies aimed not only to determine broad protein requirements but also pigs’ essential amino acids requirements. Moreover, recent studies tried to determine these nutritional requirements for each individual, which is known as protein precision nutrition. However, nutritional changes could affect different epigenetic mechanisms, modifying metabolic pathways both in a given individual and its offspring. Modifications in protein nutrition, such as change in the amino acid profile, increase or decrease in protein levels, or the addition of metabolites that condition protein requirements, could affect the regulation of some genes, such as myostatin, insulin growth factor, or genes controlling cholesterol and glucose metabolism pathways. This review summarizes the impact of most common protein nutritional strategies on epigenetic changes and describes their effects on regulation of gene expression in pigs. In a context where animal nutrition is shifting towards precision protein nutrition (PPN), further studies evaluating the effects of PPN on animal epigenetic are necessary.