Fatty acid metabolism in lambs fed citrus pulp.

In the present study, we have hypothesized that replacing barley with high proportions of dried citrus pulp in a concentrate-based diet for lambs could increase the intake of unsaturated fatty acids and could reduce the rate of the ruminal biohydrogenation of PUFA, with a consequent improvement of the intramuscular fatty acid composition. To test this hypothesis, 26 Comisana lambs were divided into 3 groups and for 56 d were fed a barley-based concentrate diet (CON; 8 lambs) or 2 diets in which barley was replaced with 24% (CIT24; 9 lambs) or 35% (CIT35; 9 lambs) dried citrus pulp. An overall improvement of the fatty acid composition of LM from lambs fed citrus pulp-containing diets was found. The PUFA/SFA ratio was lower (P < 0.05) in the LM from lambs in the CON group compared with both the CIT24 and CIT35 groups. The thrombogenic index was lower (P < 0.05) in meat from lambs fed the CIT35 diet compared with those fed the CON diet. The CIT35 diet increased the proportion of C20:5 n-3 in the LM (P < 0.05), whereas the CIT24 diet enhanced that of C22:6 -3 (P < 0.05) compared with the CON diet. Some of these results might be explained considering that feeding the CIT24 and CIT35 diets increased the intake of total fatty acids (P < 0.05) and of C18:3 n-3 (P < 0.01) compared with feeding the CON treatment. On the other hand, phenolic compounds present in citrus pulp could have inhibited the ruminal biohydrogenation of PUFA. This is supported by the fact that regardless of the level of inclusion in the diet, citrus pulp increased the proportion of rumenic acid (P < 0.001) in LM compared with the CON diet. The plasma from lambs fed both CIT24 and CIT35 diets had a greater percentage of vaccenic acid (VA; < 0.001) compared with that from lambs fed the CON diet, and the CIT35 diet increased the proportion of rumenic acid in plasma compared with the CON treatment (P < 0.05). In the ruminal fluid, stearic acid (SA) tended to decrease, and the sum of CLA tended to increase (P = 0.09) with increasing level of citrus pulp in the diets. Furthermore, the SA/(SA + VA) ratio tended to be lower (P = 0.10) in the ruminal fluid from lambs fed the CIT35 diet compared with that of the CON group. In conclusion, our results support the hypothesis that replacing barley with citrus pulp in the diet of growing lambs improves intramuscular fatty acid composition and underline the need for specific studies to clarify the mechanisms by which feeding citrus pulp affects the fatty acid metabolism in ruminants.

Effect of including carob pulp in the diet of fattening pigs on the fatty acid composition and oxidative stability of pork.

The effect of feeding pigs with carob pulp on meat quality was investigated. Nine pigs were finished on a conventional concentrate-based diet (control), while two groups received a diet comprising of the same ingredients with the inclusion of 8% or 15% carob pulp (Carob 8% and Carob 15%, respectively). Feeding carob-containing diets reduced the concentration of saturated fatty acids in the muscle, increased the concentration of monounsaturated fatty acids in meat (P < 0.01) and of n-3 polyunsaturated fatty acids (PUFAs) and reduced the n-6/n-3 PUFA ratio (P < 0.001). The meat underwent slow oxidative deterioration over 9 days of storage. However, the Carob 15% treatment increased meat susceptibility to lipid oxidation across storage (P = 0.03), while the dietary treatment did not affect meat colour stability. In conclusion, feeding pigs with carob pulp could represent a strategy,in the Mediterranean areas, to naturally improve meat nutritional value and to promote the exploitation of this local feed resource.

Antioxidant effects of ryegrass phenolics in lamb liver and plasma.

Sixteen lambs were divided into two groups and fed two different diets. Eight lambs were stall-fed with a concentrate-based diet (C), and the remaining eight lambs were allowed to graze on Lolium perenne (G). The antioxidant status was measured in the liver and plasma samples before and after solid-phase extraction (SPE) to probe the antioxidant effects that grass phenolic compounds may have conferred onto the animal tissues. The liver and plasma samples from grass-fed lambs displayed a greater antioxidant capacity than the tissues from C lamb group, but only if samples had not been passed through SPE cartridges. Finally, the feed and animal tissues, which had been purified by SPE, were analysed by liquid chromatography combined with mass spectrometry (LC���MS) to identify phenolic compounds present in L. perenne and to evaluate the results from the antioxidant assays. It would appear that the improvement of the antioxidant capacity of lamb liver and plasma from lambs fed ryegrass was not related to the direct transfer of phenolic compounds from grass to the animal tissues.

The effect of the change from a herbage- to a concentrate-based diet on the oxidative stability of raw and cooked lamb meat.

Over 89 days, 10 lambs (S) were fed concentrates and hay in stall, while 9 lambs (P) grazed at pasture. Two groups of 9 animals grazed at pasture until switching to a concentrate-based diet for 14 or 37 days before slaughter (P-S14 and P-S37). The fat content of longissimus dorsi muscle (LM) increased with increasing duration of concentrate feeding (P=0.05). As a consequence, the concentration of polyunsaturated fatty acids (PUFA) and of the highly peroxidisable (HP) PUFA in the polar lipids was similar between treatments. Lipid oxidation in fresh LM over 8 days of storage was affected by the diet (P<0.0005) with the P-S37 and P treatments producing, respectively, the highest and the lowest TBARS values. The P treatment reduced TBARS in cooked minced LM over 2 days of storage and no difference was found between the P-S14, P-S37 and S treatments. Colour stability of fresh LM was not noticeably affected by the dietary treatment.

Stable isotope ratios of blood components and muscle to trace dietary changes in lambs.

Multielemental stable isotope ratio (SIR) analysis was used in lamb plasma, erythrocytes and muscle to detect the switch from a pasture- to a concentrate-based diet, with the aim of verifying the possibility to trace the change of feeding in animal tissues. During 89 days of experimental feeding, lambs were subjected to four dietary treatments: pasture (P), pasture followed by concentrate in the stall for either 14 days (P-S14) or 37 days (P-S37) or concentrate in the stall (S). Pasture and concentrate diets comprised C3 plants only and had different values of 13C/12C, 18O/16O, 2H/1H and 34S/32S ratios. Muscle 13C/12C and 34S/32S and plasma 13C/12C and 18O/16O ratios in P, P-S14 and P-S37 lambs were significantly different. A multivariate analytical approach revealed that 13C/12C and 18O/16O ratios in plasma were the most powerful variables for the discrimination among the dietary treatments.

The restriction of grazing duration does not compromise lamb meat colour and oxidative stability.

Over 72 days, 33 lambs were fed: concentrates in stall (S), grass at pasture for 8 hours (8 h), or grass at pasture for 4 hours in the afternoon (4h-PM). The 4h-PM treatment did not affect the carcass yield compared to the 8h treatment. Meat colour development after blooming was unaffected by the treatments. The 4 h-PM treatment increased the proportion of polyunsaturated fatty acids (PUFA; P<0.0005) and of the highly peroxidizable fatty acids (HP-PUFA; P<0.001) in meat compared to the 8h treatment. The S treatment increased lipid oxidation (higher TBARS values) and impaired colour stability (higher H* values) of meat over storage compared to the 8h and 4 h-PM treatments (P<0.0005 and P=0.003, respectively). No difference in meat oxidative stability was found between the 8h and the 4h-PM treatments. In conclusion, growing lambs can tolerate a restriction of grazing duration without detrimental effects on performances and meat oxidative stability.

Influence of stall finishing duration of Italian Merino lambs raised on pasture on intramuscular fatty acid composition.

Forty male Italian Merino lambs were used to study the effects of four feeding systems on muscle fatty acids composition: S group-ten lambs were kept indoors, and fed with concentrate for all experimental period (89 days); P group-ten lambs were allowed to graze a pasture for all experimental period; PS37 group-ten lambs were allowed to graze a pasture for 52 days and shifted indoor, fed with concentrate, 37 days before slaughtered; PS14 group, where 10 lambs were fed on pasture for 75 days and shifted indoor, fed with concentrate, 14 days before slaughtered. Grazing lowered the levels of C12:0, C14:0, C16:0 and n-6 PUFA and increased n-3 PUFA and CLA isomer compared to concentrate feeding. After a short period of indoor finishing with concentrate, the fatty acid characteristics of the meat retain a part of the benefits occurring from grazing, while a longer period seems to erase almost all the benefits from grazing.

Intramuscular fatty acid composition of lambs fed diets containing alternative protein sources.

Thirty male Merinizzata italiana lambs were divided into three groups after weaning according to live weight. The diet of the three groups differed in the main protein source used in the concentrate, soybean meal for treatment SBM, faba bean for treatment FB and peas for treatment PEA. Lambs were fed ad libitum and slaughtered at about 160 days of age. Meat from the PEA group had higher proportions of the essential fatty acids C18:2 ω-6 and C18:3 ω-3 than from FB and SBM lambs and consequently its derivatives, C20:4 ω-6 and C20:5 ω-3 respectively, were higher in meat from PEA animals, compared to SBM and FB ones. The total n-3 fatty acids were highest in meat from PEA lambs and consequently PEA lambs showed a more favourable n-6/n-3 ratio. In conclusion the use of legume seeds such as peas in lamb diets positively affected intramuscular fatty acid composition.

Metabolic fate of fatty acids involved in ruminal biohydrogenation in sheep fed concentrate or herbage with or without tannins.

A 2 x 2 factorial experiment was carried out to evaluate the effect of herbage or concentrate feeding and dietary tannin supplementation on fatty acid metabolism and composition in sheep ruminal fluid, plasma, and intramuscular fat. Twenty-eight male lambs were divided into 2 equal groups at 45 d of age and kept in individual pens. One group was given exclusively fresh herbage (vetch), and the other group was fed a concentrate-based diet. Within each treatment, one-half of the lambs received supplementation of quebracho powder, providing 4.0% of dietary DM as tannins. Before slaughter, blood samples were collected. The animals were slaughtered at 105 d of age, and ruminal contents and LM were collected. Blood plasma, ruminal fluid, and LM fatty acid composition was determined by gas chromatography. Tannin supplementation reduced (P < 0.05) the concentration of stearic acid (-49%) and increased the concentration of vaccenic acid (+97%) in ruminal fluid from concentrate-fed lambs. Within concentrate- and herbage-based diets, tannin supplementation reduced the accumulation of SFA in blood (P < 0.05) compared with lambs fed the tannin-free diets. When tannins were included in the concentrate, the LM contained 2-fold greater concentrations of rumenic acid compared with the LM of the lambs fed the tannin-free concentrate (0.96 vs. 0.46% of total extracted fatty acids, respectively; P < 0.05). The concentration of PUFA was greater (P < 0.05) and SFA (P < 0.01) less in the LM from lambs fed the tannin-containing diets as compared with the animals receiving the tannin-free diets. These results confirm, in vivo, that tannins reduce ruminal biohydrogenation, as previously reported in vitro. This implies that tannin supplementation could be a useful strategy to increase the rumenic acid and PUFA content and to reduce the SFA in ruminant meats. However, the correct dietary concentration of tannins should be carefully chosen to avoid negative effects on DMI and animal performance.

Meat quality and intramuscular fatty acid composition of Sanfratellano and Haflinger foals.

The goal of the trial was to evaluate meat quality, with an emphasis on intramuscular fatty acid composition, of Sanfratellano foals, compared to that from Haflinger foals,both slaughtered at 18 months of age. Thirty foals, half of Sanfratellano breed and half of Haflinger breed, naturally weaned at 7-8 months, were divided into two homogeneous groups at 15 months of age and fed a finishing diet based on polyphite hay and concentrate. The finishing period lasted three months. Sanfratellano foals showed higher slaughter weight (P<0.05) as well carcass weight (P<0.05) compared to Haflinger foals. Meat physical and proximate analyses did not discriminate the two groups. Normal pH values (5.6-5.7) measured at 4-6 day post mortem were recorded in meat from both groups. Shear force values accounted (range 55-58N) for a favourable tenderness in both groups. The intramuscular fat level was low in both groups (<2.5%) supporting the healthy image of this meat. The proportion of linolenic acid was higher (P<0.01) in Haflinger meat than in Sanfratellano one, thus causing a higher (P<0.05) total n-3 fatty acid content. Overall meat from both groups showed a favourable repartition among saturated (36-37% total FAME's), monounsaturated (33% total FAME's) and polyunsaturated fatty acids (30-31% total FAME's).

Meat odour and flavour and indoles concentration in ruminal fluid and adipose tissue of lambs fed green herbage or concentrates with or without tannins.

A 2 × 2 factorial experiment was carried out to evaluate the effect of herbage or concentrate feeding system and tannin addition to diet on skatole and indole in ruminal fluid and adipose tissue and meat sensory properties. Twenty-eight male lambs aged 45 days were randomly assigned to one of two feeding systems (vetch green herbage or concentrates, n = 14) and within feeding system to one supplement (quebracho tannins added to the diet or none). Animals were kept in singular pens and slaughtered at the age of 105 days. Indole (P < 0.05) and skatole (P < 0.01) concentrations in ruminal fluid were higher in lambs fed herbage compared to those given concentrates. Skatole in ruminal fluid tended to be present at lower concentrations in animals that received the tannin supplementation (P = 0.07). Indole was also higher in the caudal fat of animals fed green vetch compared to those fed concentrate (P = 0.04). Skatole concentration was lower in the fat of lambs fed concentrates compared to those given herbage (P = 0.05) and was lower in the fat of animals supplemented with tannins compared to the animals not supplemented (P = 0.01). Sheep meat odour was lower in meat from animals supplemented with tannins compared to those not supplemented (P < 0.01). It is concluded that tannins are more effective in reducing skatole formation in ruminants when they are associated with concentrate diets than green herbages.

Influence of ewe feeding systems on fatty acid composition of suckling lambs.

The main objective of this study was to evaluate the effects of ewe dietary treatments on the intramuscular fatty acid composition of suckling lambs. Twenty-four pregnant Italian Merino ewes were divided into two equal groups. One group (pasture-fed group) was allowed to graze a natural pasture and the other group (stall-fed group) was penned indoors and fed with hay and concentrate. After lambing, all ewes stayed with their respective lambs for the whole experimental period. Lambs were slaughtered at 100 days of age with an average live weight of 20kg. Fatty acid profiles of milk and lamb meat (longissimus lumborum muscle) were analysed. Intramuscular fat from pasture-fed lambs showed higher (P<0.001) proportions of polyunsaturated fatty acids. The percentage of lauric (C12:0; P<0.05), palmitic (C16.0; P<0.001) and oleic (C18.1; P<0.001) fatty acids were higher in the intramuscular fat from stall-fed lambs, whereas pasture-fed lambs showed greater proportions of linolenic (C18:3; P<0.001), eicosapentaenoic (C20:5; P<0.001) and docosapentaenoic (C22:5; P<0.05) fatty acids. Moreover, the intramuscular fat from pasture-fed lambs displayed a higher (P<0.001) PUFA/SFA ratio, and a lower (p<0.001) n-6/n-3 ratio. The conjugated linoleic acid (CLA) tended to be higher (P=0.07) in the intramuscular fat from pasture-fed lambs. This study confirmed that pasture enhanced the unsaturated fatty acid profile of intramuscular fat in lambs including n-3 fatty acids.