G. Papadomichelakis

Reduced Sertoli cell number and altered pituitary responsiveness in male lambs undernourished in utero

The nutritional status of females during pregnancy can have profound effects on the fetus reproductive system development that could affect the reproductive potential as later as in adulthood (fetal programming). The aim of the present study was to examine the effects of maternal nutrient restriction imposed during different periods of gestation on pituitary responsiveness at different ages postnatal and on Sertoli cell number in male offspring. Pregnant ewes were fed to 100% of Metabolizable Energy and Crude Protein requirements throughout pregnancy (Control) or to 50% from 0 to 30 (R1) or from 31 to 100 days of gestation (R2). Male lambs were selected and fed to appetite throughout the study. At 2, 5.5 and 10 months of age a GnRH challenge was conducted. At slaughter (10 months) testes were removed and examined histologically. Maternal undernutrition did not affect the time of the onset of puberty, defined as the first increase in plasma testosterone concentrations > or =1 ng/ml. The LH and FSH response to GnRH challenge did not differ between groups at 2 and 5.5 months but at 10 months of age a higher (P<0.05) FSH response was found in R2 group. Testes weight did not differ between groups at slaughter. Mean Sertoli cell number was significantly lower in animals of R2 group compared with Control (P<0.01). A smaller seminiferous tubules diameter was detected in R2 group (P<0.05), while the diameter of the lumen was similar in all groups. Collectively, these results provide clear evidence for a direct effect of nutrient restriction during pregnancy on Sertoli cell number in adulthood. The lower number of Sertoli cells is the most candidate factor for the higher pituitary activity through a reduction in the suppressive effect of inhibin.

Sheep and goats differences in CLA and fatty acids milk fat content in relation with mRNA stearoyl-CoA desaturase and lipogenic genes expression in their mammary gland

An experiment was conducted with 12 lactating dairy ewes and 12 goats with the objective to determine whether, under the same dietary treatments, the differences in their fatty acid (FA) profile with emphasis on cis-9 trans-11 CLA milk fat content, are reflected in the transcript levels of genes involved in FA and cis-9, trans-11 CLA biosynthesis. The animals were fed with two diets (A, B) in different days of milk (DIM) due to the different milk yield, body weight etc, in order to have the same food intake and to avoid dietary effects. Diet A was fed to the animals on a group basis as it is traditionally used in practice, while diet B was chosen to avoid individual feed intake variation which is usually observed in group feeding. The results showed that there are significantly lower mRNA levels of acetyl-CoA carboxylase (ACC) in sheep mammary gland compared with those of goats, independently from the diet fed. The same trend was observed with the mRNA level of FA synthase (FAS), but the results were significant only for diet A. The mRNA level of lipoprotein lipase (LPL) in the mammary gland did not differ between sheep and goats fed with diet A. In addition, the concentration of cis-9 trans-11 CLA content was significantly higher in sheep milk fat compared with those of goats. This is in accordance with the significant higher levels on mRNA of stearoyl-CoA desaturase (SCD) which were observed in their mammary adipocytes of sheep compared with those of goats, independently of the fed diet (A or B). In conclusion, these findings demonstrate that the differences between sheep and goats, concerning cis-9, trans-11 CLA and FA milk fat content, under the same dietary treatments could be explained in part by the differences in mRNA of SCD and lipogenic genes in their mammary gland.

Supranutritional selenium level affects fatty acid composition and oxidative stability of chicken breast muscle tissue.

A total of 128 broilers were used to investigate the effect of selenium (Se) on fatty acid (FA) composition and oxidative stability of lipids in the breast muscle tissue. There were 4 replicates of 4 dietary treatments: T1 (basal diet with no added Se), T2 (T1 with 0.15 mg Se added per kg diet), T3 (T1 with 0.3 mg Se added per kg diet) and T4 (T1 with 3.0 mg Se added per kg diet). A yeast source was used for added Se. Breast muscle tissue was collected from two chickens per replicate pen for the determination of Se concentration by ICP-MS, FA profile by GC and lipid oxidation using thiobarbituric acid reactive substances method. Addition of supranutritional Se levels to chicken diets leads to the production of Se-enriched meat. Consumption of 100 g of breast meat from chickens fed diets supplemented with 0.15, 0.3 and 3 mg Se per kg of diet can provide 26, 41 and 220 μg of Se, respectively. Long-chain polyunsaturated fatty acids namely C20:3n-6, C20:4n-6, C20:5n-3, C22:5n-3 and C22:6n-3 increased linearly (p = 0.047, p < 0.001, p = 0.023, p = 0.003 and p = 0.002, respectively) as the Se inclusion levels in the diets increased. At slaughter, a linear decrease in lipid oxidation (p = 0.019) was observed with Se addition, possibly attributed to the antioxidant properties of Se. Addition of supranutritional Se to chicken diets, at levels well below those causing toxicity, leads to production of Se-enriched meat, protection of health-promoting long-chain FA like C20:5n-3 and C22:6n-3 and protection of meat quality from oxidation at day 1 after slaughter.

Effect of dietary soybean oil addition on the odd-numbered and branched-chain fatty acids in rabbit meat.

The effect of dietary soybean oil (SO) inclusion (20g/kg) on the odd-numbered (ONFA) and branched-chain (BCFA) fatty acids (FA) of two muscles, differing in fatness (Longissimus lumborum and Biceps femoris), was studied in 24 New ZealandxCalifornian rabbits. The increased muscle fatness in Biceps femoris (P<0.001) was related to higher saturated (P<0.01) and monounsaturated (P<0.01) fatty acids. Intramuscular ONFA and BCFA contents were not affected, but their proportions were reduced (P<0.01 and P<0.001) by SO addition, suggesting a dilution effect of the dietary polyunsaturates accumulated in both muscles, except for 17:0i which decreased only in Longissimus lumborum due to significant (P<0.05) soybean oilxmuscle interaction. The higher (P<0.05) BCFA contents and the FA profile in Biceps femoris were not affected by fatness, indicating an association with other muscle properties. The present study supplies new information on ONFA and BCFA in rabbit meat.

Effects of Gestational Maternal Undernutrition on Growth, Carcass Composition and Meat Quality of Rabbit Offspring

An experiment was conducted in order to evaluate the effects of gestational undernutrition of rabbit does on growth, carcass composition and meat quality of the offsprings. Thirty primiparous non lactating rabbit does were artificially inseminated and randomly divided in three treatment groups: Control (C; fed to 100% of maintenance requirements throughout gestation, n = 10), early undernourished (EU; fed to 50% of maintenance requirements during days 7–19 of gestation, n = 10) and late undernourished (LU; fed to 50% of maintenance requirements during days 20-27 of gestation, n = 10). During the 4th week of the gestation period, LU does significantly lost weight compared to C and EU groups (P<0.05). At kindling, C does produced litters with higher proportions of stillborn kits (P<0.05) while the total litter size (alive and stillborn kits) was not different among groups (10.7, 12.8 and 12.7 kits in C, EU and LU groups, respectively). Kit birth weight tended to be lower in the LU group. During fattening, body weight and feed intake were not different among offsprings of the three experimental groups. Moreover, the maternal undernutrition did not have any impact on carcass composition of the offsprings in terms of carcass parts and internal organs weights as well as meat quality of L. lumborum muscle (pH24, colour, water holding capacity and shear values) at slaughter (70 days of age). Therefore, it can be concluded that the gestational undernutrition of the mother does not have detrimental effects on the productive and quality traits of the offsprings.

Effects of increasing dietary organic selenium levels on meat fatty acid composition and oxidative stability in growing rabbits

The effects of dietary organic selenium (Se) addition at 0.1, 0.5 and 2.5mg/kg vs. an unsupplemented basal diet (BD) on performance, fatty acid (FA) composition and oxidative stability were studied in muscle tissue of growing rabbits. Muscle Se content increased (P<0.001) in a dose dependent manner with dietary Se inclusion. Saturated FA (SFA) were affected linearly (P<0.05) and quadratically (P<0.05) by dietary Se addition. Polyunsaturated FA (PUFA) increased linearly (P<0.01) resulting in a linear increase in the PUFA:SFA ratio (P<0.01) with dietary Se increment. Feeding 0.5mgSe/kg diet reduced malondialdehyde (MDA) and oxygen radical absorbance capacity (ORAC) values in the muscle, whilst 2.5mgSe/kg diet increased MDA concentrations and tended to increase ORAC values, likely indicating oxidative stress. In conclusion, dietary Se supplementation at 0.5mg/kg improves meat FA composition and oxidative stability, whereas at 2.5mg/kg may induce pro-oxidant effects.

Effects of soyabean meal- or whey-based diets on lipid metabolism in weaned piglets.

The present study aimed to test the hypothesis that dietary protein source influences lipid metabolism-related parameters weaned piglets. The effects of soyabean meal (SB) and whey proteins (WP) on gene expression of several genes involved in the lipogenic process in liver, visceral (VAT) and subcutaneous (SAT) adipose tissues, plasma insulin concentration and fatty acid (FA) profile were investigated in 18 weaned piglets. Weaned piglets were fed one of two diets containing either SB or WP as the main protein source. Following a 10-h fasting period, plasma insulin concentration and FA profile were assessed at 56 and 72 days of age, whereas gene expression in liver, VAT and SAT was assessed at 72 days of age. Plasma insulin concentration was not affected by diet, although it was 40% lower in SB fed pigs. The SB pigs had lower 14:0 (p < 0.01) and higher 18:3n-3 (p < 0.001) levels in plasma in comparison with WP pigs. However, these changes were attributed to background differences in the dietary FA profile and not to a direct protein source effect. Gene expression of sterol regulatory element-binding protein 1 (SREBP-1) in liver and VAT were lower (p < 0.01 and p < 0.05, respectively) in SB compared to WP fed piglets, but no differences occurred in SAT. No changes were observed in sterol regulatory element-binding protein 2, liver X receptor, peroxisome proliferator-activated receptors α and γ and plasminogen activator inhibitor 1 mRNA levels, either in liver or in adipose tissues. In conclusion, dietary protein source, accompanied likely by side alterations in the dietary composition, affects lipid metabolism in pigs through the downregulation of SREBP-1, which is a crucial determinant of lipogenic process.

The effect of lactating dairy ewes' diet supplementation with ALIMET (liquid methionine) on milk yield and milk composition

Abstract The objective of this work was to study the effect of the supplementation of dairy ewes’ diet with liquid methionine (ALIMET) on milk yield and milk composition, from late pregnancy to mid lactation period. Sixty 3-4 year old Boutsiko breed lactating dairy ewes with an average initial body weight 48±1.7 kg and good body condition (3.6), were divided into three groups (treatments), balanced according to milk yield. Ewes were fed 0.8 kg alfalfa hay and 0.8 kg of concentrate daily. Ewes in Group A were fed a usual concentrate for lactating ewes (control), in Group B the control concentrate +1 g ALIMET /kg concentrate, and in Group C the control concentrate +3 g ALIMET /kg concentrate. Ewes were milked twice daily, and milk weights (yield) were recorded every 4 weeks, while milk samples were taken, on a percent basis (10%), for compositional analysis. The results showed that the inclusion of ALIMET significantly increased (p<0.05) milk yield (by 6.8% in Group B and 12% in Group C), compared to control, FCM (6% fat) yield (by 5.5% in Group B and 13.6% in Group C), and milk fat, protein and non fat solids. The growth rate of lambs was 7% and 8% higher, for the suckling period of 42 days, for the Groups B and C, respectively, compared to control, but those differences were not significant. The average daily body weight change of ewes during the experimental lactation period was +0.6, +1.0 and 0.2 kg for Groups A, B and C, respectively. Thus, supplementing the ewes’ diet with ALIMET, at a level of 3 g /kg concentrate, had a positive effect on milk yield and milk composition.

The effects of rearing diet, sex and age on the fatty acid profile of Chios lambs

A total of 40 lambs of Chios breed were used to determine the effect of rearing system, sex and age on the fatty acid (FA) profile of M. semimembranosus proprius (SP), M. longissimus dorsii (LD) and M. triceps brachii (TB). The lambs were assigned into two groups balanced for bodyweight and sex. The first group (n = 20) underwent natural rearing (natural) and received only maternal milk until weaning. The second group (n = 20) weaned at birth and subjected to artificial suckling (artificial) with a commercial milk replacer. At 35 days of age, 10 animals from each group were weighed and slaughtered. The remaining lambs of both groups, after weaning were fed daily 100 g barley hay per animal and a commercial concentrate diet ad libitum up to 90 days of age, where they were also weighed and slaughtered. The results showed that the FA profile of lamb muscles was related with that of suckled milk (natural or artificial). Sex did not affect the FA profile, whereas the increase in the slaughtered age lead to changes in the FA profile of lamb muscles (SP, LD, TB). In conclusion, both rearing system and age change the FA profile of lamb muscles, but not in the same manner in all of them (SP, LD, TB).

Effect of dietary protein source on piglet meat quality characteristics

An experiment was conducted to examine the effects of different dietary protein sources (soybean meal vs whey protein) on piglet meat quality characteristics. Eighteen castrated male Large White × Duroc × Landrace piglets were randomly assigned to 2 groups. Piglets were kept in individual metabolic cages and fed ad libitum over a period of 38 days the following 2 diets: diet SB, which was formulated to meet the nutrient requirements of piglets using soybean meal as the main crude protein source and diet WP, where SB was totally replaced by a mixture of whey proteins on equal digestible energy and crude protein basis. At the end of the experiment, piglets were weighed and slaughtered. After overnight chilling, samples of Longissimus dorsi muscle were taken and were used for meat quality measurements. No significant differences were observed in the values of pH, color, water holding capacity, shear force and intramuscular fat content of L. dorsi muscle between the dietary treatments. Measurement of lipid oxidation values showed that dietary supplementation with different protein sources did not influence meat antioxidant properties during refrigerated storage. The SB piglets had lower C14:0 (P<0.01) and higher C18:3n-3 (P<0.001) levels in intramuscular fat in comparison with WP piglets. However, these changes were attributed to background differences in the dietary FA profile and not to a direct protein source effect. The results of this preliminary study indicate that the examined dietary protein sources do not have a significant effect on meat quality characteristics of piglets.