Plasma lipoprotein distribution in the turkey (Meleagris gallopavo).

The plasma lipoprotein profile has been determined in fasted 7-week-old male turkeys. Lipoprotein classes were subfractionated by density gradient ultracentrifugation. According to phospholipid concentration over the density gradient, an initial peak was visible in the usual LDL density range, whereas two peaks were detected in that of HDL. As density increased, the lipid composition of particles showed an increase in cholesteryl esters and decrease in triglycerides. VLDL were recovered in the first fraction (d<1.013) on the top of the gradient and IDL in fractions 2-5 (d=1.013-1.028 g/ml). The LDL and HDL populations in the density range 1.028-1.090 (fractions 6-12) differ from that found in the other bird species analyzed under the same experimental conditions. LDL predominated in fractions 6-8 with mostly beta-motility and apoB100 as the major protein component. HDL predominated in fractions 10-12 (d=1.055-1.090 g/ml) and corresponded to the first HDL peak (HDL-(A)), with mostly alpha-mobility and apoA-I as the major protein component. Both LDL- and HDL-like particle populations were present in fractions 6-12, making the separation between the two classes of lipoproteins difficult. The second peak in the HDL density range (HDL-(B), d=1.076-1.146 g/ml) contained only HDL-type particles above d=1.090 g/ml. This points out the specificity of the lipoprotein distribution in the turkey that is unique among animals. The density limit at d=1.048 g/ml is a good compromise for the separation of LDL from HDL; however, the presence of HDL-like particles in the LDL density range, and the existence of two, and even three HDL subclasses should be taken into account in the design of further metabolic studies.

Plasma glucose-insulin relationship in chicken lines selected for high or low fasting glycaemia.

1. Selected Fat or Lean chickens differ in their plasma glucose insulin relationship: in the fed or fasted state, Fat chickens have a lower glycaemia associated with normal or higher insulinaemia, depending upon the difference in glycaemia. 2. Conversely, chickens selected for low fasting glycaemia (LG) are fattier than their counterparts selected for high fasting glycaemia (HG), although the divergence in fat content is lower than in the Fat-Lean model. 3. The plasma glucose insulin relationship has been investigated in males of the HG and LG lines in the F4 and F5 generations. 4. A difference in glycaemia is suggested during embryonic development and was present at hatching and later on in the fasted or the fed state; insulinaemia did not differ. 5. During refeeding after an overnight fast, glycaemia differed between lines (except at intermediate times); cumulative food intake and insulinaemia were similar. 6. During a glucose tolerance test, glucose disposal rate and insulinaemia were rather similar. 7. Exogenous insulin exerted a very similar hypoglycaemic effect in both lines. 8. Other variables (body temperature, plasma concentrations of potassium and alpha NH2-non protein nitrogen) did not differ between HG and LG chickens. 9. In conclusion, HG and LG chickens do not exhibit any differences in glucose disposal rate, insulinaemia (in various nutritional conditions) or sensitivity to exogenous insulin, which contrasts with Fat or Lean chickens and may explain why HG and LG chickens have diverged to a lesser extent in fat content.

Does excess dietary protein improve growth performance and carcass characteristics in heat-exposed chickens?

The effects of two environmental temperatures (22 and 32 C, constant) and five dietary protein contents (10 to 33% CP) were investigated in 4- to 6-wk-old broiler chickens. High ambient temperature reduced growth rate, feed efficiency, and breast muscle proportion and increased abdominal fat proportion. Irrespective of ambient temperature, increasing dietary protein content improved growth performance and carcass characteristics. At 32 C, there was a greater heterogeneity of the data, and bird responses were lower than at 22 C. We concluded that under conditions of chronic heat exposure, diets containing the highest protein levels, 28% and 33% compared with 20% CP, slightly improved chick performance. However, the effect was low and, in our experimental conditions, modifying dietary protein supply (variations in the total quantity of protein) is not sufficient to help broilers to withstand hot conditions.

Effects of chronic heat exposure and protein intake on growth performance, nitrogen retention and muscle development in broiler chickens.

The respective effects of ambient temperature, dietary crude protein and feed intake were investigated in finishing chickens and the consequence of protein supplementation under high temperature conditions was analysed in particular. Heat-related reduction in growth was associated with decreased nitrogen retention (-30 or -35% according to the diet), which could not be explained by the observed lower feed intake alone. Tissue samples performed in 5- to 6-week-old chicks showed varying effects of heat according to the muscles studied: at 32 degrees C, the proportion of Pectoralis major muscle (in percentage of body weight) appeared slightly reduced (reduction lower than 10%), whereas the proportion of two leg muscles were increased (+10 to +15% for the Sartorius muscle; +5% for the gastrocnemius muscle). At 32 degrees C, providing a high protein diet significantly (P < 0.05) increased weight gain and feed efficiency, and slightly improved whole body protein deposition.

Genetic parameters of body weight of broiler chickens measured at 22 degrees C or 32 degrees C.

1. Male broilers (n = 1521) from 247 families were reared from 4 to 6 weeks of age at 22 degrees or 32 degrees C. 2. Genetic correlations between measurements recorded at 22 degrees C and 32 degrees C were 0.73 +/- 0.12 for weight gain between 4 and 6 weeks and 0.74 +/- 0.08 for food conversion ratio (FCR). Genes controlling weight gain at both temperatures differed to some extent. 3. Heritability of weight gain from 4 to 6 weeks was much lower at 32 degrees C than at 22 degrees C (0.13 +/- 0.03 vs 0.24 +/- 0.04): selection for increased body weight will thus be much less efficient at 32 degrees C than at 22 degrees C. 4. Conversely, heritabilities of the FCR were very similar at the 2 temperatures (0.28 +/- 0.04 at 22 degrees C and 0.27 +/- 0.04 at 32 degrees C). Selecting for FCR would thus be efficient at 32 degrees C too. 5. These results justify, at least under our experimental conditions, selecting broiler lines for improved growth performance at 22 degrees C. However, it could be more efficient if broilers are to be reared in hot climates to select for improved FCR rather than for increased body weight.

Effect of high ambient temperature on feed digestibility in broilers.

The effect of chronic heat exposure on feed digestibility of broilers was investigated. Eighty 4-wk-old male chickens were brooded in individual battery cages in two controlled-environment rooms at a constant ambient temperature (22 or 32 C) until 6 wk of age. They were equally distributed into three treatments: 22 C, ad libitum feed consumption (22AL); 32 C, ad libitum feed consumption (32AL), and 22 C, pair-feeding on the daily feed intake of heat-exposed chickens (22PF). Broilers were fed either a standard corn-soybean meal diet (control diet) or a practical seasonal diet containing several ingredients including wheat, spring pea, and animal fat (summer diet). Digestibility of energy, dry matter, protein, fat, starch, and nitrogen, and total mineral balances were measured between 38 and 42 d of age. Apparent metabolizable energy content of summer diet was significantly decreased in 32AL compared to 22AL, whereas AME of the control diet did not change. Nitrogen retention was significantly reduced in 32AL birds compared to 22AL and 22PF birds, irrespective of the diet. Taking into account these differences in nitrogen balance, AMEn was reduced under hot exposure: -72 and -155 kcal for control and summer diets respectively, in 32AL compared to 22PF chickens. This reduction could be explained by a significant decrease of nutrient digestibility:protein: -4.2 percentage units irrespective of the diet, fat: -1.7 and -5.2 percentage units for control and summer diets respectively, and starch: -4.2 percentage units for summer diet. It thus appears worthwhile to take into account such reduction in digestibility to formulate practical diets for brooding under hot conditions. High quality oil and protein sources should also be used instead of low quality feedstuffs, like animal sources, in such conditions.

Chronic heat exposure enhances fat deposition and modifies muscle and fat partition in broiler carcasses.

The effect of chronic heat exposure on carcass quality of broilers: proportion of lean and fat tissues, fat content, and fatty acid composition, was investigated. One hundred and eight 4-wk-old male chickens were brooded in individual battery cages in two controlled-environment rooms at constant ambient temperature (22 or 32 C) until 7 wk of age. They were equally distributed into three treatments: 22 C, ad libitum feeding (22AL); 32 C, ad libitum feeding (32AL); and 22 C, pair-feeding on the daily feed intake of heat-exposed chickens (22PF). At 7 wk of age, heat-exposed chickens (32AL) had a lower body weight gain than the other birds: -47% compared to 22AL and -31% compared to 22PF. At 32 C, broilers exhibited a lower breast to body weight proportion: 11.9 vs 13.4% for 22AL. Abdominal, subcutaneous, and intermuscular fat deposits were enhanced in hot conditions, respectively, 15, 21, and 22% compared to 22AL and 58, 64, and 33% compared to 22PF. However, lipid contents of abdominal, subcutaneous, intermuscular, and intramuscular tissues were not affected by heat exposure but were significantly reduced in the 22PF birds. In heat-exposed birds, although saturated fatty acid proportions, particularly palmitic acid (C16:0), were increased, unsaturated fatty acids as a percentage of total fatty acids were decreased, especially oleic (C18:1) and linoleic (C18:2) acids in fat tissues. Consequently, under ad libitum feeding conditions, heat exposure significantly decreased the unsaturated to saturated fatty acid ratio in the abdominal and subcutaneous fat tissues, but not in intermuscular and intramuscular fats.

Metabolic and endocrine changes induced by chronic heat exposure in broiler chickens: growth performance, body composition and energy retention.

The present study was performed in order to investigate the effect of chronic heat exposure (32 degrees, constant) on growth, body composition and energy retention of broiler chickens in relation to age. At 2 and 4 weeks of age, fifty-four male Shaver broiler chickens were allocated to three treatments according to the following design: 22 degrees, ad lib. feeding (22AL); 32 degrees, ad lib. feeding (32AL); and 22 degrees, pair-feeding with the 32 degrees group (22PF). Ambient temperature was kept constant at either 22 or 32 degrees for 2 weeks. Heat exposure decreased feed intake by 14% between 2 and 4 weeks and by 24% between 4 and 6 weeks of age. Even with the same feed intake, chicks gained less weight at 32 degrees than at 22 degrees, 5.5% less in young chickens and 22% less in older ones. Hot environmental conditions thus resulted in decreased feed efficiency; the feed:gain ratio was 2.85 at 32 degrees compared with 2.06 at 22 degrees in 22AL birds for the period 4-6 weeks. Body composition appeared significantly affected by high ambient temperature. Feathering was reduced at 32 degrees in absolute weight but not as a proportion of body weight. Heat-exposed birds showed a decrease in body protein content, protein gain and protein retention. Group 32AL birds were fatter than the pair-fed (22PF) or ad lib.-fed (22AL) groups at 22 degrees. The percentage of energy retained as fat was 79 in heat-exposed chickens compared with 64 in the control groups. The energy retained as protein:energy retained as fat for groups maintained at 22 degrees (0.56) was twice that for those maintained at 32 degrees (0.28). These modifications should be investigated further in relation to metabolic and endocrinological changes.

Metabolic and endocrine changes induced by chronic heat exposure in broiler chickens: biological and endocrinological variables.

The present study was designed to investigate the effect of chronic heat exposure (32 degrees constant) on plasma metabolites and hormone concentrations in broiler chickens. At 2 and 4 weeks of age, fifty-four male Shaver broiler chickens were allocated to one of three treatments: 22 degrees, ad lib. feeding (22AL), 32 degrees, ad lib. feeding (32AL) and 22 degrees, pair-feeding with the 32AL group (22PF). Ambient temperature was kept constant at either 22 or 32 degrees for 2 weeks. Plasma glucose, triacylglycerols, phospholipids, non-esterified fatty acids (NEFA), individual amino acids, uric acid, insulin, triiodothyronine (T3), thyroxine, corticosterone were determined. Sensitivity to exogenous insulin was also measured at 7 weeks of age. At 4 and 6 weeks of age, i.e. after 2 weeks at high ambient temperature, fasted 32AL chickens displayed similar concentrations of glucose and triacylglycerols to those of 22AL birds. When fed, 32AL chickens exhibited higher plasma levels of glucose and decreased concentrations of NEFA and amino acids. Feed restriction resulted in intermediate values. Concentrations of all plasma free amino acids were decreased under heat exposure except for aspartic acid, glutamic acid and phenylalanine. At 6 weeks of age, plasma T3 was reduced irrespective of the nutritional state, while plasma corticosterone concentrations were increased in 32AL birds compared with 22AL birds. Heat exposure did not change plasma insulin concentration in either fasted or fed chickens. The 32AL chickens displayed significantly reduced sensitivity to exogenous insulin when fasted, but an enhanced response to insulin when fed, compared with both 22 degrees groups. Such endocrinological changes could stimulate lipid accumulation through increased de novo lipogenesis, reduced lipolysis and enhanced amino acid catabolism under chronic heat exposure.

Are genetically lean broilers more resistant to hot climate?

1. Genetically lean (LL) or fat (FL) male chickens were exposed to either high (32 degrees C) or control (22 degrees C) ambient temperature up to 9 weeks of age. They were fed on one of two isoenergetic diets differing in protein content: 190 or 230 g/kg. 2. At 22 degrees C, weight gain of LL broilers was the same as in FL chickens, but at the high temperature LL birds grew to a greater weight than FL ones. 3. Food conversion efficiency was not affected by ambient temperature in LL chickens but was depressed in FL ones at 32 degrees C. 4. Increasing dietary protein content did not alleviate heat-induced growth depression irrespective of the genotype. 5. Gross protein efficiency was higher in LL chickens and was less depressed at 32 degrees C than in FL birds. 6. Fat deposition decreased with increasing protein concentration at normal temperature in both genotypes; at high temperature, high protein content enhanced fatness, particularly in LL chickens. 7. Thus, genetically lean broilers demonstrated a greater resistance to hot conditions: this was indicated by enhanced weight gain and improved food and protein conversion efficiencies.

Research note: effect of high ambient temperature on dietary metabolizable energy values in genetically lean and fat chickens.

Effect of high ambient temperature (32 versus 22 C) on dietary ME value was investigated in 32 genetically lean and fat 8-wk-old male chickens. Lean broilers exhibited higher AME and TME values than fat chickens. Hot climatic conditions significantly increased AME and TME values, particularly in leaner birds. Protein retention efficiency was enhanced by selection for leanness and increased with ambient temperature. Correction for nitrogen balance (AME(n) and TMEn) reduced the effect of temperature but lean genotypes still revealed higher TMEn values than fatter ones.

Cerebellum and memory: an experimental study in the rat using a passive avoidance conditioning test.

Adult DA/HAN strain rats were submitted to a one-trial passive avoidance conditioning procedure consisting in associating darkness with a nociceptive stimulus. Seven or fourteen days after the one-trial initial experience, they were tested again in order to know whether they had forgotten it or not. The animals were divided into two experimental groups, the rats being either conditioned (COC group) or not (NOC group) before cerebellectomy, and two control groups, the animals being either intact (C group) or sham-operated (SO group). Each group was divided into two subgroups, one being given the retrieval test 7 days and the other 14 days after the initial conditioning. The results show that retention in C, SO and NOC rats was similar whether the animals were tested 7 days or 14 days after the initial one-trial conditioning. Seven days after their initial experience and the cerebellectomy, the retention in COC rats was null while when they were tested 14 days after cerebellar removal these animals had much better scores, significantly higher than 7 days after the lesion. It is concluded that the cerebellum is involved in the consolidation processes of the memory trace but is not the site of memory storage.

[Food value of spiruline algae for the laying hen]. / Valeur alimentaire des algues spirulines pour la poule pondeuse

The three diets (composition in table I) were isonitrogenous (16,4 p. 100 crude protein), similar in their content of lysine and sulfur amino acids, but with different levels of spiruline algae : 0 (control); 7.5 or 15 p. 100. Each diet was used for the feeding of 48 hybrid pullets of medium size during a 24-week test period (32 to 56 weeks). Egg production (table II) was slightly better (47.1 g/hen/day) with 7.5 p. 100 of spirulines, compared to the control (45.3 g/hen/day), the difference being significant (P less than 0.01). With 15 p. 100 of spirulines egg production was similar to that observed in the control, but the average egg weight was reduced (58.5 vs 60.5 g) as a result of a lower albumen content. The colour of the egg yolk (table IV) was very light in the controls, but was a deep orange (above the maximum in the Roch scale) with 7.5 or 15 p. 100 of spirulines in the laying hen diet. The diet consumption, feed conversion and live weight variations (table III) show that the energy level is no higher in laying hens (about 2 500 kcal M.E./kg spirulines) than in the broiler.