Pasture-fed Lambs Research Articles

Is a short concentrate-finishing period in lambs raised on alfalfa pasture effective at reducing fat indoles contents and lightening meat colour?

Pasture-feeding in lambs has been associated with dark-coloured meat and high meat contents of volatile indoles (skatole and indole), which may be responsible for sensory defects. The risk of off-flavours is even higher when lambs graze alfalfa, because it is particularly rich in rapidly degradable proteins. Here, we investigated whether a short concentrate stall-finishing period in lambs that previously grazed alfalfa influences meat sensory quality traits. We compared three feeding treatments, using three groups of 10 male Romane lambs: grazing alfalfa (A), stall-feeding with concentrate and straw (S), and stall-finishing with concentrate and straw for 21 days after previously grazing alfalfa (AS). During stall-feeding, the concentrate was given at a level adjusted to achieve a similar growth pattern in all treatment groups, and the length of the trough was sufficient for all lambs to have access to the feeds at the same time. Lamb live weight and age at slaughter, and carcass conformation and fatness were similar for all treatment groups. Perirenal fat skatole content was lower in AS and S lambs than in A lambs (P < 0.001 and P < 0.05, respectively), and not significantly different between AS and S lambs. Perirenal fat indole and dorsal fat skatole concentrations were lower in AS lambs than in A lambs (P < 0.05 and P < 0.005, respectively), the other pairwise comparisons being not significant. There was no treatment effect on dorsal fat indole content. Longissimus et lumborum muscle colour coordinates differed between pasture-fed and stall-fed lambs, with a lower lightness (P < 0.005) and greater redness and hue angle (P < 0.001 and P < 0.01, respectively) in pasture-fed lambs, but muscle colour coordinates did not differ between A and AS lambs. A 21-d concentrate-based stall-finishing period in lambs previously raised on alfalfa pasture therefore markedly reduced fat indoles concentrations compared to lambs grazed on alfalfa until slaughter but did not change meat colour.

96 Cover Crop Grazing and Backgrounding on Carcass Quality

Abstract Integration of sheep into cropping systems via cover crop grazing leases has potential to benefit sheep producers with a source of inexpensive, high quality forage. We examined this potential by comparing lamb growth and carcass traits of four rearing systems: grain-finished control (GR), cover crop brassica-finished (CCB), cover crop mixture-finished (CCM), and background on brassica and finished on grain (BK-GR). Dorset x Polypay lambs (n = 60; 3 pens or pastures, 5 lambs each) were blocked by body weight and randomly assigned to treatment. All diets were provided to maximize voluntary dry matter intake. Lambs were harvested after 6 wks of feeding for GR and 8 wks for CCB, CCM and BK-GR (BK-GR = 4 wks brassica then 4 wks grain). Grain-fed lambs (GR and BK-GR, 442 g/d) grew faster than pasture-fed lambs (CCB and CCM, 152 g/d) prior to harvest (Table 1, P &amp;lt; 0.01) and attained greater body mass (HCW), muscling (LEA, EMD), fatness (BF, BWF) and yield grade (all P &amp;lt; 0.05). Growth of pasture-fed lambs declined 38% over time (247 wk 1–4 vs. 152 g/d wk5-8; P &amp;lt; 0.05). Pasture-fed lambs were leaner than grain-fed lambs (BF, yield grade; P &amp;lt; 0.01), yet attained a yield grade 2 average. Background lambs (BK-GR) exhibited a 107% increase in growth when fed grain (232 g/d pasture vs. 481 g/d grain, P &amp;lt; 0.01) and were fatter (BF, P &amp;lt; 0.05) yet had reduced eye muscle depth (P &amp;lt; 0.01) at harvest than GR lambs. Lambs did not differ in growth or any carcass measurement according to pasture type (CCB vs. CCM). We conclude that 8 wks of cover crop finishing produced acceptable carcass weight and finish. Backgrounding on cover crops followed by 4 wks of grain finishing results in marked compensatory gain with lambs achieving the same carcass size and similar qualities to lambs fed only grain.

Carcass characteristics and meat quality of commercial lambs reared in different forage systems

Carcass attributes and meat quality characteristics of the Longissimus thoracis muscle were evaluated from 135 lambs from 9 commercial forage production systems (n = 15) on 3 farms. Wethers had greater eye muscle area and loin intramuscular fat percentage than cryptorchid lambs (P < 0.05). Chicory-fed lambs had a heavier carcass weight and greater loin intramuscular fat percentage compared to pasture-fed lambs (P < 0.05), but similar eye muscle area and fat depth over the loin (P > 0.05). Lambs that were processed at weaning had heavier carcasses and greater loin intramuscular fat percentage and shear force values than lambs slaughtered after further finishing on pasture or chicory (P < 0.05). The effects of the sex of the lamb, its castration status, forage diet and age at slaughter on meat quality were subtle.

Nitrogen stable isotope and carotenoid pigments signatures in the meat as tools to trace back the diet: Comparison between two sheep breeds

We compared the response of two dietary biomarkers (nitrogen stable isotope and carotenoid pigments signatures in lamb meat) in two sheep breeds when fed two dietary lucerne levels, and we deduct subsequent implications for diet authentication issues. Two breeds (Limousine and Romane) and two daily dietary lucerne levels (H: High, 500g;L: Low, 0g) were used for 60days pre-slaughter. Treatment H comprised 35 lambs of each breed, individually penned and fed. Treatment L comprised 8 lambs of each breed, fed in groups. The δ15N value of the muscle did not differ between breeds and gave a correct classification score of 92.9% comparing lambs from both feeding treatments. The absolute value of the mean integral of perirenal fat reflectance spectrum, which quantifies light absorption by carotenoid pigments present in perirenal fat, and plasma carotenoid content were similar in L Romane and L Limousine lambs, but were higher in H Romane lambs than in H Limousine lambs As the carotenoid pigments are highly involved in the discrimination process between pasture-fed lambs and concentrate-fed lambs using visible spectroscopy on the fat, further work is required to test the extent to which this between-breed variability may modulate the reliability of pasture-feeding authentication using visible spectroscopy of the fat over a range of breeds.

0900 Supplementation of glycerol or fructose via drinking water of pasture-fed lambs

0900 Supplementation of glycerol or fructose via drinking water of pasture-fed lambs

The effect of feeding system on slaughter-carcass characteristics, meat quality, and fatty acid composition of lambs

Abstract. In this study, we aimed to determine the slaughter-carcass characteristics, meat quality, and fatty acid composition in lambs raised under intensive and extensive conditions. The animal material consisted of 30 Norduz male lambs, with an average age of 171 days. The lambs were divided into two groups: concentrate-fed lambs (CO) and pasture-fed lambs (PS). The results showed that the CO lambs had heavier carcasses (p&lt; 0.001), a higher dressing percentage (p&lt; 0.001), and higher intramuscular fat (p&lt; 0.01) than the PS lambs. It was determined that the longissimus thoracis muscle of the CO lambs had a lower ultimate pH and higher L* and water-holding capacity than the PS lambs. In this study, intramuscular fat (longissimus thoracis, semimembranosus, triceps brachii), subcutaneous and tail fat samples were used to evaluate the effect of feeding system on fatty acid composition. The polyunsaturated fatty acid to saturated fatty acid ratio (PUFA ∕ SFA) of intramuscular fat was found to be significantly higher in the CO group than in the PS lambs, while similar subcutaneous and tail fat results were found in both groups. Moreover, the PS lambs had a lower n6 ∕ n3 ratio and higher percentage of omega-3 than the CO lambs in all tissues studied (p&lt; 0.05). Overall, the CO lambs have heavier and fattier carcasses with better meat quality traits than the PS lambs. However, the effects of feeding system have varying results based on the fatty acid composition of different types of fat deposits.

Visible spectroscopy on carcass fat combined with chemometrics to distinguish pasture-fed, concentrate-fed and concentrate-finished pasture-fed lambs

We used visible spectroscopy of fat to discriminate lambs that were pasture-fed (n=76), concentrate-fed (n=79) or concentrate-finished after pasture-feeding (n=69). The reflectance spectrum of perirenal and subcutaneous caudal fat was measured at slaughter and 24h post mortem. In Method 1 (W450–510), the optical data were used at wavelengths in the range of 450–510nm to calculate an index quantifying light absorption by carotenoids. In Method 2 (W400–700), the full set of data at wavelengths in the range of 400–700nm was used to differentiate carcasses using PLS-DA as a classification method. W400–700 proved more reliable than W450–510 (P<0.0001). The proportion of correctly classified lambs using W400–700 was 95.6% and 95.9% for measurements made on perirenal fat at slaughter and 24h post mortem. The intensity of light absorption by carotenoids decreased exponentially with live weight gain during the finishing period.

Effects of supplementation with fish oil and barium selenate on performance, carcass characteristics and muscle fatty acid composition of late season lamb finished on grass-based or concentrate-based diets

The objectives of this study were to investigate the effects of fish oil supplementation on performance and muscle fatty acid composition of hill lambs finished on grass-based or concentrate-based diets, and to examine the interaction with selenium (Se) status. In September 2006, 180 entire male lambs of mixed breeds were sourced from six hill farms after weaning and finished on five dietary treatments: grazed grass (GG), grass +0.4 kg/day cereal-based concentrate (GC), grass +0.4 kg/day cereal-based concentrate enriched with fish oil (GF), ad libitum cereal-based concentrate (HC) and ad libitum fish oil-enriched concentrate (HF). Within each treatment, half of the lambs were also supplemented with barium selenate by subcutaneous injection. At the start of the trial, the proportion of lambs with a marginal (<0.76 μmol/l) or deficient (<0.38 μmol/l) plasma Se status was 0.84 and 0.39, respectively. Compared with control lambs, GG lambs treated with Se had higher (P < 0.01) plasma Se levels, whereas erythrocyte glutathione peroxidase activity was higher (P < 0.01) for Se-supplemented lambs fed diets GG and GF. However, Se supplementation had no effects on any aspect of animal performance. Fish oil increased (P < 0.05) levels of 22:5n-3 and 22:6n-3 in the Longissimus dorsi of HF lambs but otherwise had no effect on the health attributes of lamb meat. There were no significant effects of fish oil on dry matter intake, animal performance or lamb carcass characteristics. Daily carcass weight gain (CWG; P < 0.001), carcass weight (P < 0.01) and conformation score (P < 0.01) increased with increasing concentrate inputs. Lambs fed concentrate-based diets achieved a higher mean CWG (P < 0.001), dressing proportion (P < 0.001) and carcass weight (P < 0.011), and were slaughtered up to 8.3 days earlier (P < 0.05) and at 1.2 kg lower (P < 0.05) live weight than pasture-fed lambs. However, carcasses from grass-fed lambs contained lower levels of perinephric and retroperitoneal fat (P < 0.05), and had less fat over the Iliocostalis thoracis (P < 0.001) and Obliquus internus abdominis (P < 0.05). Meat from grass-fed lambs also had lower levels of 18:2n-6 and total n-6 fatty acids compared with those finished indoors. The results of this study demonstrate that fish oil supplementation has some benefits for the health attributes of meat from lambs fed concentrate-based diets but not grass-based diets. Supplementing Se-deficient lambs with barium selenate will improve Se status of lambs fed zero-concentrate diets, but has no additional benefit when lambs are already consuming their daily Se requirement from concentrates or when fish oil-enriched diets are fed.

Comparison of meat and carcass quality in organically reared and conventionally reared pasture-fed lambs

The ‘Organic’ product label guarantees a production process that avoids the use of synthetic fertilisers, pesticides and hormones and minimises recourse to pharmaceuticals or veterinary drugs; however, the product's quality remains an issue that needs to be addressed in response to consumer demand. Consequently, this study was conducted to compare the sensory and nutritional qualities of meat and carcasses from pasture-fed lambs reared organically (O) or conventionally (C). Mean lamb growth profile was kept similar between the two treatments to avoid confounding effects with lamb age or weight at slaughter. The experiment was conducted over 3 years (2005 to 2007) with 12 O and 12 C lambs each year. The O and C treatments differed in the level of on-pasture mineral N fertilisation inducing a higher proportion of white clover in the organic pasture than the conventional pasture. Lambs were slaughtered when they attained a fat class of 2 to 3, and carcass and meat quality were evaluated. Lambs were slaughtered at an average weight and age of 35.3 kg and 156 days in the O treatment, respectively, and 35.2 kg and 155 days in the C treatment, respectively. Sensory evaluation indicated that loin chops from the O treatment had a higher level of abnormal fat odour compared with the C treatment. Carcasses from the O treatment had a softer subcutaneous fat one among 3 years (2007) compared to the C treatment. These results are probably due to a higher proportion of white clover in the diet. Organically reared lambs did offer the slight advantage of muscle fatty acid containing a higher level of stearic acid, which may have positive effects in the prevention of cardiovascular disease in humans. This may be the result of a higher rumen bio-hydrogenation of C18:3n-3 due to differences in the botanical composition between the O and the C pasture. Production system had no effect on the colour characteristics of the meat and subcutaneous fat, except lightness of subcutaneous dorsal fat, which was slightly higher in the O lambs. There were no differences between O and C lambs in terms of colour stability and lipid oxidation of the meat during the 6-day refrigerated storage under gas-permeable film.

Universal DNA-Based Methods for Assessing the Diet of Grazing Livestock and Wildlife from Feces

Because of the demand for controlling livestock diets, two methods that characterize the DNA of plants present in feces were developed. After DNA extraction from fecal samples, a short fragment of the chloroplastic trnL intron was amplified by PCR using a universal primer pair for plants. The first method generates a signature that is the electrophoretic migration pattern of the PCR product. The second method consists of sequencing several hundred DNA fragments from the PCR product through pyrosequencing. These methods were validated with a blind analysis of feces from concentrate- and pasture-fed lambs. The signature method allowed differentiation of the two diets and confirmed the presence of concentrate in one of them. The pyrosequencing method allowed the identification of up to 25 taxa in a diet. These methods are complementary to the chemical methods already used. They could be applied to the control of diets and the study of food preferences.

Discrimination of pasture-fed lambs from lambs fed dehydrated alfalfa indoors using different compounds measured in the fat, meat and plasma

The last decade has seen important developments in the use of carotenoid pigments to authenticate pasture-feeding in ruminants. However, dehydrated alfalfa is sometimes incorporated in grain-based concentrates fed to stall-raised lambs, which may affect the reliability of the pasture-feeding authentication methods based on carotenoids in plasma and fat, due to significant residual carotenoid levels post-dehydration. The aim of this study was to examine whether other compounds can give additional information to authenticate diet and discriminate pasture-fed lambs from lambs fed high levels of alfalfa indoors. Two feeding treatments were compared: pasture-feeding (P) v. stall-feeding with dehydrated alfalfa (A). Each treatment group consisted of seven male Romanov × Berrichon lambs. Pasture-fed (P) lambs grazed a permanent graminaceae-rich pasture maintained at a leafy, green stage, offered ad libitum; they received no supplementation at pasture. A-group lambs were individually penned and fed dehydrated alfalfa and straw; their feed level was adjusted to achieve a similar growth pattern as for P-group lambs. Plasma carotenoid concentration was measured at slaughter by spectrophotometry. The reflectance spectrum of perirenal and subcutaneous caudal fat was measured at 24-h post mortem and used to calculate an index (absolute value of the mean integral (AVMI)) quantifying light absorption by carotenoid pigments present in the fat. The nitrogen (N) stable isotopes ratio (δ15N) in both feed and longissimus dorsi muscle was measured by isotopes ratio mass spectrometry (IRMS). Volatile compounds were analyzed in perirenal fat for five randomly chosen lambs per treatment, using dynamic headspace–gas chromatography–mass spectrometry. Plasma carotenoid concentration and AVMI of the fat did not differ significantly between P- and A-group lambs, but there were significant between-treatment differences in meat δ15N values and in the terpene profiles of perirenal fat. A discriminant analysis performed using three compounds in different animal tissues (δ-cadinene in perirenal fat, δ15N value of the meat and plasma carotenoid concentration) clearly separated pasture-fed lambs from lambs fed high levels of alfalfa indoors.

Effect of Feeding Regime on Fatty Acid Composition of Longissimus dorsi Muscle and Subcutaneous Adipose Tissue of Akkaraman Lambs

Summary In this study, effect of feeding regime on fatty acid composition including conjugated linoleic acid (CLA) of Longissimus dorsi muscle and subcutaneous adipose tissue from lambs were investigated. From same flock, forty-five male Akkaraman suckling lambs, the most common lamb breeds in Turkey, were fed mainly maternal milk from birth to weaning and then were divided into three groups (only maternal milk-fed group, pasture-fed group and concentrate-fed group) at three months of age with an average live weight of 25 kg. Longissimus dorsi muscle from pasture fed-lambs contained significantly more total CLA, n-3 and n-3/n-6 ratio than other groups. In addition, pasture-fed lambs contained significantly more total saturated fatty acid (SFA), CLA, n-3 and n-3/n-6 ratio compared concentrate fed-lambs in subcutaneous adipose tissue. In conclusion, intramuscular muscle and subcutaneous adipose tissue fatty acid composition of lamb can be improved by pasture in the feeding regime.

A dose-response study relating the concentration of carotenoid pigments in blood and reflectance spectrum characteristics of fat to carotenoid intake level in sheep1

This study was conducted to describe the dose-response curve relating the concentration of carotenoid pigments in plasma and reflectance spectrum characteristics of fat to the carotenoid intake level in sheep, and to investigate the extent to which incorporation of dehydrated alfalfa in the diet affects the reliability of the discrimination between concentrate-fed and pasture-fed lambs based on these measurements. In Exp. 1, 6 treatments were compared in individually penned lambs: feeding 0, 250, 500, 750, 1,000, or 1,250 g/d of dehydrated alfalfa for 60 d before slaughter. Each treatment (T0 to T1,250) consisted of 8 male Romanov x Berrichon lambs with an initial average BW of 24.8 kg (SD 2.6). All lambs received straw for ad libitum intake and T0 to T1,000 lambs received a concentrate free of green vegetative matter in amounts to produce similar ADG in all treatments. In Exp. 2, 33 male Romanov x Berrichon lambs grazed a natural pasture maintained in a leafy green vegetative stage for at least 59 d before slaughter. Initial BW when turning out to pasture was 14.2 kg (SD 2.3). Plasma carotenoid concentration was measured at slaughter by spectrophotometry. Reflectance spectrum, lightness, redness, and yellowness were measured after 24 h of shrinkage in subcutaneous caudal and perirenal fat. The spectra were translated to 0 reflectance at 510 nm, and the integral of the translated spectrum was calculated between 450 and 510 nm (i.e., the range of light absorption by carotenoids). Reflectance measurement was replicated 5 times, from which we calculated the absolute value of the mean integral (AVMI). In Exp. 1, plasma carotenoid concentration at slaughter (PCCS) increased linearly with mean daily carotenoid intake (P < 0.01). Both subcutaneous caudal and perirenal fat AVMI increased linearly (P < 0.01) with mean daily carotenoid intake and PCCS, the slopes of the regressions being greater for perirenal than for subcutaneous caudal fat. The mean PCCS was greater for lambs of Exp. 2 than for lambs on any treatment of Exp. 1 (P < 0.01). We established the dose-response curves relating PCCS and AVMI of subcutaneous and perirenal fat to carotenoid intake level. The combined use of PCCS and of perirenal fat AVMI enabled discrimination of pasture-fed lambs of Exp. 2 from the lambs of Exp. 1 that received up to 500 g/d of dehydrated alfalfa.

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 20 kg. 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.

Methodological developments in the use of visible reflectance spectroscopy for discriminating pasture-fed from concentrate-fed lamb carcasses

The ability to authenticate the feed given to animals from the animal products has become a major challenge for scientists, monitoring bodies and commercial entities alike. This study compared two methods based on the use of the visible reflectance spectrum of the fat to discriminate pasture-fed (P) from stall concentrate-fed (S) lamb carcasses. A total of 307 (143 P and 164 S) Limousine lambs were used over 2 years. Pasture-fed lambs grazed a permanent pasture that was maintained at a leafy, green vegetative stage, and offered ad libitum; they received no supplementation at pasture. Body weight of P lambs when turning out to pasture and at slaughter averaged 9.2 (standard deviation (s.d.) 2.21) kg and 33.2 (s.d. 2.89) kg, respectively. S lambs were fed indoors on an ad libitum diet of commercial concentrate and hay until slaughter at a mean body weight of 33.7 (s.d. 3.62) kg. The reflectance spectrum of perirenal and subcutaneous caudal fat was measured at slaughter and at 24 h post mortem. Plasma carotenoid concentration was measured at slaughter. In method 1, the fat reflectance spectrum data were used at wavelengths between 450 and 510 nm to calculate an index quantifying light absorption by carotenoid pigments. In method 2, a multivariate analysis was performed over the full set of fat reflectance data at wavelengths between 400 and 700 nm. Method 2 yielded a higher proportion of correctly classified lambs compared with method 1 (P < 0.05 to 0.001), except for measurements made at 24 h post mortem on perirenal fat for S lambs. The proportion of lambs correctly classified using method 2 was 87.4% and 92.9% for measurements made on perirenal and caudal fat at slaughter, and 93.9% and 91.0% for measurements made on perirenal and caudal fat 24 h post mortem. Plasma carotenoid concentrations were higher in P lambs than in S lambs (P < 0.001), which led to correct classification of 90.7% of the lambs.

Use of Lotus corniculatus containing condensed tannins to increase lamb and wool production under commercial dryland farming conditions without the use of anthelmintics

Two grazing experiments were conducted for 12 and 13 weeks, respectively, over the spring periods of 2000 and 2001 at Massey University's Riverside farm in the Wairarapa (New Zealand) to compare effects of grazing Lotus corniculatus (birdsfoot trefoil; cv. Grasslands Goldie) or perennial ryegrass ( Lolium perenne)/white clover ( Trifolium repens) dominant pasture during lactation on ewe and lamb live weight (LW), wool production, faecal nematode egg counts (FEC) and dag score. Ewes and their lambs (mainly twins) were rotationally grazed on lotus or pasture ( n = 50) without any anthelminitc treatment at a herbage allowance of 6.5 and 8.0 kg green DM/ewe/days for Experiments 1 and 2, respectively. Total condensed tannins (CT) concentration in the diet selected was 24 to 27 g CT/kg DM for lotus and 1.4 to 1.5 g CT/kg DM for pasture. In vitro organic matter digestibility and metabolisable energy (ME) concentration were higher for lotus than for pasture in both experiments, whilst the concentrations of neutral detergent fibre (NDF) was lower in lotus than in pasture. The LW gain, weaning LW and wool production were consistently higher ( P < 0.001) for lambs grazing lotus, in both Experiment 1 (258 versus 189 g/days; 36.1 versus 30.1 and 1.17 versus 0.98 kg) and in Experiment 2 (247 versus 162 g/days; 31.8 versus 24.1 and 1.17 versus 0.81 kg), respectively. Ewe and lamb dag score were strongly and positively correlated with dag weight ( P < 0.001), and generally increased with time in sheep grazing pasture; while grazing on lotus consistently reduced dag score. FEC in ewes grazing pasture showed a post-parturient rise (PPR) following lambing, whilst ewes grazing lotus had a reduced PPR in FEC. Up to day 70, FEC in lambs grazing lotus was lower than that for lambs grazing pasture, but between day 70 and the end of both experiments (approximately day 90), FEC in lambs grazing lotus increased to similar values as for pasture-fed lambs. FEC was not correlated with dag score or dag weight in ewes or lambs grazing pasture, but these indices were weakly and positively correlated in ewes and lambs grazing lotus, suggesting that lowering FEC on lotus also reduced dag formation. Under dryland farming conditions, the use of Lotus corniculatus (cv. Grasslands Goldie) during the spring/early summer lactation period can be used to increase lamb growth and wool production, whilst eliminating the need for pre-lambing anthelmintic drenching and, probably, reducing the amount of insecticide needed to control flystrike. These effects are probably due to the CT in lotus reducing rumen protein degradability and controlling internal parasites, and to the higher digestibility and voluntary feed intake (VFI) of lotus compared to perennial ryegrass ( Lolium perenne)/white clover ( Trifolium repens) pasture. The absence of endophyte in lotus may also have contributed to these effects.

Analysis of the volatile fraction of lamb fat tissue: influence of the type of feeding

The volatile compounds of subcutaneous fat tissue of lambs were analysed by dynamic headspace sampling-high resolution gas chromatography-mass spectrometry (DHS-HRGC-MS). The animals were produced in six European countries according to local traditional rearing conditions and they were classified into two groups according to the predominant type of feed consumed (pasture or concentrate). The analysis showed that the pasture-fed lambs clearly differed from the concentrate-fed lambs. Fat samples from the pasture-fed lambs desorbed greater quantities of compounds of green leaf tissue origin such as long-chain alkanes, C7 aldehydes and 2,3-octanedione. The fat samples from the concentrate-fed lambs desorbed greater quantities of short-branched and non-branched acids and methyl ketones. The present results suggest that 2,3-octanedione or long-chain alkanes, and 4-heptanone or 2-octanone in the lamb subcutaneous fat tissue are specific of feedings consisting predominantly of pasture and concentrate, respectively. These compounds could be used as markers of the feeding background of the animal.

Alpha-tocopherol concentrations and case life of lamb muscle as influenced by concentrate or pasture finishing

Two experiments were conducted to evaluate alpha-tocopherol accumulation in muscle of lambs finished on pasture or concentrates. The objective for Exp. 1 was to compare accumulation of alpha-tocopherol in the longissimus muscle of pasture-fed lambs to that of lambs fed three concentrations (15, 150, and 300 IU/kg of DM) of supplemental vitamin E (all rac alpha-tocopheryl acetate) in all-concentrate diets. The objective in Exp. 2 was to investigate the effect of duration of supplemental vitamin E feeding on alpha-tocopherol content and color change during display case storage of lamb muscle. Treatments evaluated in Exp. 2 were: 15 IU of supplemental vitamin E/kg DM fed to finish; 15 IU/kg followed by 300 IU/kg of DM during the last 21 d; and 15 IU/kg DM until 7 d prior to finish, then 300 IU/kg DM. In Exp. 1, alpha-tocopherol concentration of rotational grazed alfalfa and perennial ryegrass averaged 137 and 169 mg/kg of DM. Vitamin E treatments for lambs fed concentrate diets did not affect ADG (P > 0.15), but ADG was greater (P < 0.01) for concentrate-fed lambs than for grazing lambs. For the concentrate-fed lambs, alpha-tocopherol in longissimus muscle increased quadratically (P < 0.05) as dietary concentrations of vitamin E increased. Predicted maximum alpha-tocopherol concentration in muscle occurred at about 400 IU/kg of diet DM. Longissimus muscle from lambs grazing alfalfa or ryegrass had similar (P > 0.50) alpha-tocopherol concentrations, and those concentrations were similar to values obtained when the concentrate diet supplemented with 150 IU of vitamin E/kg was fed. In Exp. 2, no differences (P > 0.10) in ADG were observed. Concentrations of longissimus alpha-tocopherol were highest when 300 IU supplemental vitamin E was fed for 21 d prior to slaughter. During a 6-d display period, semimembranosus steaks from lambs fed 300 IU of supplemental vitamin E/kg for either 7 or 21 d had higher a* and b* color readings than steaks from lambs fed 15 IU/kg of supplemental vitamin E. Increased consumption of vitamin E either via pasture or supplementation results in higher alpha-tocopherol concentrations in meat.

Meat quality of cryptorchid lambs grazing either dryland or irrigated perennial pasture with some silage supplementation

The meat quality of lambs grazed on perennial pasture (ryegrass Lolium perenne, cocksfoot, Dactylis glomerata and white clover Trifolium repens) was examined in three treatments; group 1 (S) lambs were grazed on dryland pasture for 30 days and then offered a supplement of pasture silage ad libitum until slaughter, 30 days later ( n = 21). Lambs in group 2 (P) were grazed on dryland pasture throughout ( n = 28) and those in group 3 (IP) on irrigated pasture ( n = 28). Lambs in group IP had a significantly ( p < 0.001) heavier pre-slaughter liveweight and hot carcass weight than lambs in the other two groups. There was no significant difference ( p < 0.05) infatscore between groups or in GR when adjusted to a common carcass weight. For cold carcass weight (reduced sample) IP lambs were still significantly heavier than those from group P, but no different to those from group S ( n = 15, 15 and 10, respectively). There was no significant difference between groups for measures of fatness or for m. longissimus thoracis et lumborum (LL) area when adjusted to a common carcass weight of 23.6 kg. There was a significant difference between ( p < 0.001) treatments for pH, group P carcasses having higher pH values for the LL muscle, with no treatment effect on m. semimembranosus (SM) pH. Differences between groups for meat colour values ( L ∗, a ∗, b ∗ ) showed no consistent trend and there was no significant difference ( p > 0.05) between groups in tenderness of the LL and SM muscles as indicated by shear force values. Aroma of the loin meat from pasture-fed lambs (P) was considered significantly ( p < 0.05) stronger than from lambs in groups S and IP ( n = 6, all groups) and the flavour of samples from lambs in group P was significantly ( p < 0.05) stronger than from lambs in group IP. Overall there was no significant ( p < 0.05) difference in acceptability between groups. The results indicate that consumers would be unlikely to detect the differences identified by the panel and that pasture silage will not have an adverse effect on lamb eating quality.

The effects of age, weaning, drench volume and yarding on ruminoreticulum bypass in sheep, with reference to the anthelmintic efficacy of benzimidazole drenches

Aims. To determine the incidence of ruminoreticulum bypass in lambs before and after weaning, following drenching with anthelmintic-equivalent volumes of fluid; to investigate the influence of withholding feed for 24 hours before drenching on the incidence of ruminoreticulum bypass; and to investigate the hypothesis that ruminoreticulum bypass occurs more frequently following drenching with large than with low volumes. The relationship between these factors and the efficacy of benzimidazole anthelmintic drenches has been widely promoted in New Zealand and Australia. Methods. Video-taped fluoroscopy, using barium sulphate suspension with a specific gravity of 1.38 as a contrast medium, was used to study closure of the reticular groove and ruminoreticulum bypass in sheep. Results. When lambs were drenched with 3 ml of barium sulphate suspension/10 kg liveweight soon after removal from pasture, ruminoreticulum bypass only occurred before weaning and during the first 8 weeks after weaning. However, when a low volume drench (1 ml/10 kg) was used in lambs soon after removal from pasture during the same period, ruminoreticulum bypass was not observed. When recently weaned lambs were yarded for 24 hours before drenching with barium sulphate suspension, substantial (≥ 20%) ruminoreticulum bypass occurred in 25-58% of the animals. When 8-9 month-old hoggets were yarded for 24 hours before drenching, substantial ruminoreticulum bypass occurred in 35% of the animals. Ruminoreticulum bypass was not observed in the same group of hoggets when drenched soon after removal from pasture, in a reversed crossover experiment. This effect of withholding feed for 24 hours on ruminoreticulum bypass was significant (p < 0.0001). In hoggets which had been yarded for 24 hours before drenching with barium sulphate suspension, the incidence of ruminoreticulum bypass was significantly lower (p = 0.0026) following the use of a low volume ( 1 ml/10 kg) when compared to high volume (3 ml/ 10 kg) of drench. Thus, the effect of withholding feed for 24 hours on ruminoreticulum bypass was largely overcome when the low volume drench was used. Conclusions. These results support the use of low volume formulations of benzimidazole drenches for New Zealand pasture-fed lambs less than 6 months old. The results indicate that, in order to obtain the optimum efficacy of benzimidazole anthelmintics in New Zealand pasture-fed sheep, which have been yarded for 24 hours, low volume drench formulations should be used.