A. Priolo

Effect of grass or concentrate feeding systems and rate of growth on triglyceride and phospholipid and their fatty acids in the M. longissimus thoracis of lambs

Thirty-two male Ile-de-France lambs were used in a factorial 2×2 design to analyse the effects of feeding systems (grass outdoor, G, or concentrate and hay indoor: stall, S) and of growth rate (low, L, or high, H) on total lipids, triglyceride (TG) and phospholipid (PL) contents and their fatty acid composition in the longissimus thoracis muscle (L.T.). Contents were lower for TG (10.4 vs. 15.8 mg/100 g fresh tissue, P<0.05) and higher for PL (6.4 vs. 5.8 mg/100 g fresh tissue, P <0.05) in grass-fed lambs compared to stall-fed ones. TG of grass fed lambs displayed lower proportions of palmitic acid (C16:0), monounsaturated fatty acids (MUFAs), linoleic acid (C18:2n-6) and other (n-6) polyunsaturated fatty acids (PUFA) and higher proportions of stearic acid (C18:0), linolenic acid (C18:3n-3), cis 9, 11 trans C18:2 and trans monounsaturated fatty acids. In PL of the same lambs only lower MUFA, C18:2n-6 and (n-6) PUFA and higher C18:3n-3, (n-3) PUFA and cis 9, 11 trans C18:2 were observed. Growth rate had no effect on lipid, TG or PL contents of longissimus thoracis. However C18:0 proportions were higher in TG and lower in PL for low growth rate lambs. Low growth rate lambs had also lower cis 9, 11 trans C18:2 in TG. Thus, irrespective of growth rate, the muscle lipids characteristic of grass fed lambs fulfilled the recommended features of human food components much better than that of stall fed lambs, namely for CLA and C18:3n-3. The lower ratios of (n-6) to (n-3) PUFA displayed in grass fed lambs both in TG and in PL were also useful to discriminate all the grass fed lambs from all the stall fed animals.

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.

Ruminal biohydrogenation as affected by tannins in vitro.

The aim of the present work was to study the effects of tannins from carob (CT; Ceratonia siliqua), acacia leaves (AT; Acacia cyanophylla) and quebracho (QT; Schinopsis lorentzii) on ruminal biohydrogenation in vitro. The tannins extracted from CT, AT and QT were incubated for 12 h in glass syringes in cow buffered ruminal fluid (BRF) with hay or hay plus concentrate as a substrate. Within each feed, three concentrations of tannins were used (0.0, 0.6 and 1.0 mg/ml BRF). The branched-chain volatile fatty acids, the branched-chain fatty acids and the microbial protein concentration were reduced (P < 0.05) by tannins. In the tannin-containing fermenters, vaccenic acid was accumulated (+23 %, P < 0.01) while stearic acid was reduced ( - 16 %, P < 0.0005). The concentration of total conjugated linoleic acid (CLA) isomers in the BRF was not affected by tannins. The assay on linoleic acid isomerase (LA-I) showed that the enzyme activity (nmol CLA produced/min per mg protein) was unaffected by the inclusion of tannins in the fermenters. However, the CLA produced by LA-I (nmol/ml per min) was lower in the presence of tannins. These results suggest that tannins reduce ruminal biohydrogenation through the inhibition of the activity of ruminal micro-organisms.

Ruminant fat volatiles as affected by diet. A review

Volatile compounds in meat have been widely studied for their favourable or undesirable effects on meat flavour, or for their potential use in tracing the animal feeding system. To date, the chemical mechanisms causing the appearance of volatile compounds in meat have been largely understood. Several variables are involved in the accumulation of volatiles in animal tissues and among them animal diet plays a key role. The purpose of the present review is to highlight the effects of different dietary regimes (concentrate, green grass and fat-enriched diets) on the appearance of fat volatile compounds in ruminant meat. Grain-based diets induce greater accumulations in meat of branched-chain fatty acids, some aldehydes, and lactones while meat fat from grazing animals contains high levels of phenols, terpenes, indoles and sulphur compounds. Fat-enriched diets exert their effect mainly on those volatiles which originate from polyunsaturated fatty acids. Cooking procedures have been considered for their contribution to fat volatiles in meat by reactions induced by high temperatures.

Dietary tannins improve lamb meat colour stability

Fourteen male Comisana lambs were divided into two groups at 45days of age: lambs fed a concentrate diet (C), or lambs fed the same concentrate with the addition of quebracho (Schinopsis lorentzii) tannins (T). Sheep were slaughtered at 105days of age. Lipid oxidation, colour coordinates, haem pigment concentration, and metmyoglobin percentages were measured on minced semimembranosus muscle (SM) over 14days of refrigerated storage in a high oxygen modified atmosphere. Tannin supplementation increased (P<0.01) a(∗) values and reduced (P<0.01) b(∗) values of the SM when compared to C. Lower hue angles (P<0.001) and metmyoglobin formation (P=0.07) were observed in lamb from T-fed compared to C-fed sheep during the 14-days storage period. Furthermore, feeding T resulted in greater (P<0.001) haem pigment concentrations in the SM during refrigerated storage; however, diet had no (P=0.28) effect on lipid oxidation. Therefore, including quebracho tannins in sheep diets can improve meat colour stability of fresh lamb during extended refrigerated storage.

Bacterial and protozoal communities and fatty acid profile in the rumen of sheep fed a diet containing added tannins.

ABSTRACT This study evaluated the effects of tannins on ruminal biohydrogenation (BH) due to shifts in the ruminal microbial environment in sheep. Thirteen lambs (45 days of age) were assigned to two dietary treatments: seven lambs were fed a barley-based concentrate (control group) while the other six lambs received the same concentrate with supplemental quebracho tannins (9.57% of dry matter). At 122 days of age, the lambs were slaughtered, and the ruminal contents were subjected to fatty acid analysis and sampled to quantify populations of Butyrivibrio fibrisolvens, which converts C18:2c9-c12 (linoleic acid [LA]) to C18:2c9-t11 (rumenic acid [RA]) and then RA to C18:1t11 (vaccenic acid [VA]); we also sampled for Butyrivibrio proteoclasticus, which converts VA to C18:0 (stearic acid [SA]). Tannins increased (P < 0.005) VA in the rumen compared to the tannin-free diet. The concentration of SA was not affected by tannins. The SA/VA ratio was lower (P < 0.005) for the tannin-fed lambs than for the controls, suggesting that the last step of the BH process was inhibited by tannins. The B. proteoclasticus population was lower (−30.6%; P < 0.1), and B. fibrisolvens and protozoan populations were higher (+107% and +56.1%, respectively; P < 0.05) in the rumen of lambs fed the tannin-supplemented diet than in controls. These results suggest that quebracho tannins altered BH by changing ruminal microbial populations.

Lipid and colour stability of meat from lambs fed fresh herbage or concentrate

Fourteen male Comisana lambs were divided into two groups at 45days of age and were individually penned for 105days. Over this period, seven lambs were fed a concentrate-based diet (C), whereas the remaining animals received vetch (Vicia sativa; H) harvested daily and given fresh to the animals. Lipid oxidation was measured in both minced cooked meat (semimembranosus muscle, SM) over 4days of aerobic refrigerated storage and on minced raw meat stored over 14days in a high oxygen atmosphere. Colour descriptors, haem pigment concentration, and metmyoglobin percentages were also determined during storage duration on the minced raw meat. Lipid oxidation increased over time in cooked and raw meat (P<0.0005), but lower TBARS values were found in both cooked and minced meat from lambs fed vetch compared to those given concentrates (P=0.001; P=0.006, respectively). Higher a* values, lower b* values and lower hue angle values were observed in meat from H-fed animals as compared to meat from C-fed lambs (P=0.006; P=0.02; P=0.005, respectively). Metmyoglobin formation increased over time (P<0.0005), but the H diet resulted in lower metmyoglobin percentages than the C diet (P=0.006). Haem pigment concentration decreased over the 14days of storage (P<0.0005). We conclude that, under conditions that promote oxidative stress in meat, a herbage-based diet can improve the oxidative stability of meat compared to a concentrate-based diet.

Effects of rigor attainment temperature on meat blooming and colour on display

This paper describes the colour properties of seven hot-boned, unstimulated beef striploins during rigor attainment at 9, 14 and 24°C, during blooming at 4°C, and after storage at -1°C for 0, 2 and 8 weeks. Immediately after rigor attainment (0 weeks of storage) full blooming, as judged by L* and chroma, took at least 12 h. After 2 and 8 weeks storage, blooming was complete within about 4 h. The exponential equations describing blooming were different for 0 weeks compared with 2 and 8 weeks. This difference can be explained in terms of oxygen consumption by meat freshly in rigor. At 0 weeks, meat that entered rigor at 24°C had the best bloomed colour, whereas at 2 and 8 weeks the 9°C treatment had the best and the 24°C the worst. The data set, which spanned a range of ultimate pH values and three rigor attainment temperatures, was used to estimate the value of early colour measurements (first 24 h post-rigor) in predicting colour during display several weeks later. As judged by correlation coefficients, early measurements of hue were the only ones useful. L* and chroma were poor predictors. This result, together with the knowledge that blooming is slow in the first 24 h post-rigor, casts doubt on the value of subjective or objective colour assessments made in chillers. Temperature of rigor attainment between 9 and 24°C did not affect the time of browning onset, nor the rate of browning. It was confirmed that meat with lower pH had higher chroma before and after blooming.

Lamb meat quality as affected by a natural or artificial milk feeding regime

Fourteen Barbaresca lambs were divided into two groups of seven at 24h from birth and reared exclusively on natural milk (NR) or on artificial milk (AR). Lambs were slaughtered at 40 days of age. The NR group tended (P<0.10) to grow faster, thus resulting in a higher (P<0.10) carcass weight as compared to the AR group. AR meat was darker (P<0.05), leaner (P<0.001) and with a higher moisture (P<0.10) and ash (P<0.05) content than its counterpart. The proportion of polyunsaturated fatty acids was higher (P<0.01), while that of saturated lower (P<0.01) in meat from the AR group, resulting in a higher (P<0.01) polyunsaturated/saturated ratio. Linoleic acid content (P<0.001) and its n-6 series derivatives, except 9-12 trans C18:2 n-6 (P<0.001), increased more in the AR group meat than in the NR group. On the other hand, α-linolenic (P<0.001) and other n-3 series fatty acids were higher in meat from the NR group than in the AR group, leading to a lower (P<0.001) n-6/n-3 ratio. Furthermore, 9 cis 11 trans CLA was higher (P<0.001) in NR meat compared to AR meat. Finally, a milk-feeding regime exclusively based on artificial milk adversely affected the dietetic value of lamb meat compared to a natural rearing system, reducing the level of desirable fatty acids such as n-3 series and CLA.

Δ9 desaturase protein expression and fatty acid composition of longissimus dorsi muscle in lambs fed green herbage or concentrate with or without added tannins

The aims of this study were to investigate the effect of feeding system and of supplementation of tannins (8.93% DM) on the relationship between intramuscular fat content, fatty acid composition and Δ(9)desaturase (Δ(9)d) protein expression in longissimus dorsi muscle of lamb. Twenty-eight Comisana lambs (age 45days) were fed either vetch (Vicia sativa) or concentrate. The herbage diet was (i) lower in saturated fatty acids (especially in C16:0), C18:1 n-9 and in C18:2 n-6; (ii) higher in C16:1 and C18:3 n-3 when compared to concentrate. Within each feeding system the lambs were divided into two sub-groups, one of which received the diet without tannins supplementation, and the other was fed the diets supplemented with the tannins from Quebracho (Schinopsis lorentzii). The animals were slaughtered at age 105days. The concentrate feeding system increased (p<0.01) the total intramuscular fat content and the amount of SFA, MUFA and n-6 PUFA and decreased the level of n-3 PUFA (p=0.05) when compared to the vetch-fed animals but did not affect Δ(9) desaturase protein expression. There was no correlation between Δ(9)d protein expression and total intramuscular fatty acids, CLA and MUFA level. It was suggested that in ruminants, in contrast to monogastric animals, Δ(9)d expression does not play the key role in intramuscular fatty acids formation. Tannins supplementation resulted in higher (p<0.05) muscle levels of transC18:1 and C18:2 n-6. It has also increased Δ(9)d expression in the case of herbage-based diet but not in the case of concentrate-based diet. The mechanism of tannins action on the enzyme expression needs to be elucidated.