The present study was conducted to examine effects of long-term graded L-arginine supply on growth development, egg laying and egg quality in four genetically diverse purebred layer lines. The study comprised a rearing trial from hatch to week 16 and a following laying performance trial from week 17 to 41. After hatch 150 oneday-old female chicks of each genotype were distributed to three diets. The experimental diets were equivalent to 70, 100 and 200% L-arginine of age-specific recommended level (National Research Council, 1994) and were offered ad libitum to chicks (hatch to week 7), pullets (week 8 to 16) and hens (week 17 to 41). However, hens' diets were quite low in crude protein. After a pre-laying period from week 17 to 21 thirty-six pullets of each group were used further in the laying performance trial. Independent of chicken's genetic background, insufficient L-arginine supply caused lower body weight, daily weight gain and daily feed intake during the rearing (p＜0.001) and induced lower laying intensity and daily egg mass production in the laying period (p＜0.05). Parameters fitted to Gompertz function suggested higher adult body weight in L-arginine supplemented birds compared to insufficient supplied ones (p＜ 0.01). Groups fed with insufficient L-arginine reached age of maximum daily weight gain later and showed lowest maximum daily weight gain (p＜0.001). As a consequence of limitations in dietary L-arginine and crude protein, high performing genotypes decreased strongly in body weight, daily feed intake and performance compared to the low performing genotypes. In conclusion, L-arginine modified the amount of weight gain and feed intake, especially in growing chicks and pullets independent of genetic background. The high performing hens were more nutritionally stressed than the low performing ones, because concentrations of dietary crude protein were relatively low.

L-arginine (Arg) is an essential amino acid in birds that plays a decisive role in avian protein synthesis and immune response. Effects of graded dietary Arg supply on metabolic and clinical response to Escherichia coli lipopolysaccharide (LPS) were studied over 48 hours after a single intramuscular LPS injection in 18-week-old genetically diverse purebred pullets. LPS induced a genotype-specific fever response within 4 hours post injectionem. Whereas brown genotypes showed an initial hypothermia followed by longer-lasting moderate hyperthermia, white genotypes exhibited a biphasic hyperthermia without initial hypothermia. Furthermore, within 2 hours after LPS injection, sickness behavior characterized by lethargy, anorexia, intensified respiration, and ruffled feathers appeared, persisted for 3 to 5 hours and recovered 12 hours post injectionem. The varying grades of Arg did not alter the examined traits named above, whereas insufficient Arg reduced body growth and increased relative weights of liver and pancreas significantly. At 48 hours post injectionem, increased relative weights of liver and spleen were also found in LPS treated pullets, whereas LPS decreased those of pancreas, bursa, thymus, and cecal tonsils. Moreover, LPS lowered the sum of plasma amino acids and decreased plasma concentrations of Arg, citrulline, glutamate, methionine, ornithine, phenylalanine, proline, tryptophan, and tyrosine, and increased those of aspartate, glutamine, lysine, 1- and 3-methyl-histidine. Elevating concentrations of dietary Arg led to increasing plasma concentrations of Arg, citrulline, ornithine, and 3-methyl-histidine subsequently. As quantitative expression of LPS-induced anorexia, proteolysis, and the following changes in plasma amino acids, pullets showed a significant decrease of feed and nitrogen intake and catabolic metabolism characterized by negative nitrogen balance and body weight loss in the first 24 hours post injectionem. Pullets recovered from the challenge within the second 24 hours post injectionem and changed to anabolism with re-increased feed and nitrogen intake, positive nitrogen retention, and weight gain. To conclude, present results confirmed that LPS induced numerous metabolic and physiological changes in pullet's genotypes, whereas dietary Arg affected the examined traits only slightly.

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Due to its decisive function in the avian metabolic, endocrine and immune system L-arginine (Arg) is dietary indispensable for chickens. In 12-week-old cockerels of two high- and two low-performing purebred layer lines, the effects of increasing dietary Arg on the haematological and febrile response were studied over 48 h after single lipopolysaccharide (LPS) injection. The offered diets contained Arg equivalent to 70%, 100% and 200% of recommended supply. Pathophysiological alterations in weight gain, feed intake, body temperature and differential blood count were examined in comparison with their physiological initial values. Within the first 24 h after LPS injection, cockerels reduced feed intake and lost body weight subsequently. Thereby, low-performing genotypes lost body weight to a lesser extent than high-performing ones. The loss of body weight was further intensified by deficient dietary Arg. Within the following 24 h, cockerels recovered by improving feed intake and weight gain. Furthermore, LPS induced genotype-specific fever response: both brown genotypes showed initial hypothermia followed by longer lasting moderate hyperthermia, whereas the white genotypes exhibited biphasic hyperthermia. Fever response was accompanied by significant changes in differential blood counts. Characterized by lymphopenia and heterophilia, a severe leucopenia was observed from 4 to 8 h after LPS injection and replaced by a marked leucocytosis with longer lasting monocytosis up to 48 h after LPS injection. Under given pathophysiological conditions, deficiently Arg-supplied cockerels showed higher total leucocyte counts than adequately and excessively Arg-supplied cockerels. However, deficient and surplus dietary Arg tended to cause higher ratios between heterophils and lymphocytes. To conclude, present results confirmed that LPS induced numerous immunological changes in 12-week-old cockerels and emphasized that chicken's genotype is a source of variation to be considered for immunological studies. Deficient dietary Arg intensified acute changes in differential blood counts and weight gain during LPS-induced inflammation.

Little information has been available about the influence of genetic background and dietary L-arginine (Arg) supply on organ growth of chickens. Therefore, the present study examined the effects of a graded ad libitum Arg supply providing 70, 100 and 200% of recommended Arg concentration on organ growth of female chickens from hatch to 18 weeks of age. The chickens derived from four layer lines of different phylogeny (white vs. brown) and laying performance (high vs. low). Based on residual feed and absolute body and organ weights recorded in six-weekintervals, feed consumption, changes of relative organ weights and allometric organ growth were compared between experimental groups.Surplus Arg caused higher feed intake than insufficient Arg (p＜0.01) that induced growth depression in turn (p ＜0.05). During the entire trial chicken's heart, gizzard and liver decreased relatively to their body growth (p＜0.001) and showed strong positive correlations among each other. On the contrary, proportions of pancreas and lymphoid organs increased until week 12 (p＜0.001) and correlated positively among each other. Due to their opposite growth behaviour (p＜0.001), internal organs were assigned to two separate groups. Furthermore, insufficient Arg induced larger proportions of bursa, gizzard and liver compared with a higher Arg supply (p＜0.05). In contrast to less Arg containing diets, surplus Arg decreased relative spleen weights (p＜0.01). The overall allometric evaluation of data indicated a precocious development of heart, liver, gizzard, pancreas and bursa independent of chicken's genetic and nutritional background. However, insufficient Arg retarded the maturation of spleen and thymus compared with an adequate Arg supply.In conclusion, the present results emphasised the essential function of Arg in layer performance, and indicated different sensitivities of internal organs rather to chicken's dietary Arg supply than to their genetic background.