The growth of Clun and Southdown sheep: body composition and the partitioning of total body fat

Fat deposition and partitioning for meat production in cattle and sheep

In markets for beef and sheep meat, an appropriate level of intramuscular fat (IMF) is highly desirable for meat-eating quality, but strategies to improve it usually lead to an undesirable excess in carcase fat, presenting a major challenge to livestock producers. To solve this problem, we need to understand the partitioning of fat among the major fat depots: IMF, subcutaneous fat (SCF) and visceral fat (VF). In most genotypes of cattle and sheep, the rate of accretion is lower for IMF than for SCF and VF, so genetic selection for a high level of IMF, or the use of an increased dietary energy supply to promote IMF deposition, will increase overall fatness and feed costs. On the other hand, feeding postnatal calves with excessive concentrates promotes IMF deposition, so a nutritional strategy is feasible. With genetic strategies, several problems arise: 1) positive genetic correlations between IMF, SCF and VF differ among genotypes in both cattle and sheep; 2) genotypes appear to have specific, characteristic rates of accretion of IMF during periods of growth and fattening; 3) most breeds of cattle and sheep naturally produce meat with relatively low levels of IMF, but IMF does vary substantially among individuals and breeds so progress is possible through accurate measurement of IMF. Therefore, an essential prerequisite for selection will be knowledge of the genetic correlations and fat accretion rates for each genotype. Currently, selection for IMF is based on existing technology that directly measures IMF in the progeny or siblings, or estimates IMF in live animals. New technology is needed to permit the simultaneous measurement of SCF and IMF in the field, thus opening up the possibility of accurate selection, particularly for fat partitioning in live animals. Specifically, there would be great value in detecting individuals with an IMF advantage at an early age so the generation interval could be shortened and genetic gain accelerated. Genetic gain would also be greatly aided if we could select for genes that control adipogenesis and lipogenesis and are also differentially expressed in the various depots.

Liquid Chromatography Quadrupole Time-of-Flight Mass Spectrometry and Rapid Evaporative Ionization Mass Spectrometry Were Used to Develop a Lamb Authentication Method: A Preliminary Study

A untargeted metabolomics approach was proposed in this study based on ultra-high performance liquid chromatography quadrupole time-of-flight (UHPLC-QTOF) and rapid evaporative ionization mass spectrometry (REIMS) to discriminate lamb and mutton meat and investigate their subtle metabolic differences, considering the higher popularity of lamb meat than mutton in the market. Multivariate statistical analysis was performed for data processing in order to distinguish between the two sample types. A total of 42 potential metabolites (20 in positive and 22 in negative ion mode) were defined for UHPLC-QTOF analysis, which provided references for discriminating the two kinds of meat. Furthermore, three potential markers were tentatively identified using LC/MS data against chemical databases. In addition, 14 potential metabolites were putatively identified in negative ion mode using the LipidMaps database. Meanwhile, the data-driven soft independent modeling of class analogy (DD-SIMCA) model was established, which could rapidly differentiate non-pretreated lamb meat and mutton with 92% specificity, rendering REIMS a promising technique for meat identification.

Relationships Between Measurements of Body Fat in Thoroughbred Horses

Equine obesity is increasing in prevalence, and weight loss diets are frequently recommended for these horses. However, there are also management situations in which horses are deemed to be too thin. To monitor the efficacy of weight change programs, estimates of body fat are often made. There are several systems available to estimate body fat, and there are benefits and challenges to using each method. The objective of this study was to compare four different methods of estimating body fat in Thoroughbred horses. In 14 mature Thoroughbred horses, relationships among body condition score (BCS), morphometric measurements, ultrasonic measures of subcutaneous fat depots, and estimation of total body fat (BF_D) via measurement of total body water through deuterium oxide dilution were evaluated. Body condition scores ranged from 4.5 to 6.5 on a 9-point scale. Body condition score, heart girth-to-body weight ratio, and BF_D were all positively correlated with each other (P < .05). Subcutaneous fat depth at the tailhead tended to be positively related to BF_D when only horses with BCS ≥ 5 were included (P = .0680). These data suggest that BCS remains a simple means of monitoring adiposity in mature horses in moderate condition. Tailhead fat depots may become useful for monitoring changes in body fat in Thoroughbreds with a BCS above 5, although more work with animals of higher adiposity is required and at different times of year.

Assessment of body fat in the pony: part I. Relationships between the anatomical distribution of adipose tissue, body composition and body condition

REASONS FOR PERFORMING STUDY

Evaluation of equine body fat content is important for nutritional and clinical purposes. However, our understanding of total body fat and its regional distribution in the body is sparse. Currently, body fat evaluation relies on the subjective assessment of body condition score (BCS), which has never been validated against 'gold standard' chemical analysis or dissection measurements in ponies.

OBJECTIVES

To define the relationships between subjective (BCS), objective (morphometric) indices of body fat and 'gold standard' measurements of actual body composition.

HYPOTHESES

BCS and morphometry offer valid, noninvasive methods for determination of body fat in equids.

METHODS

Seven mature (mean ± s.e. 13 ± 3 years, 212 ± 14 kg, BCS 1.25-7/9), Welsh Mountain pony mares, destined for euthanasia (for nonresearch purposes), were used. For all ponies, body mass (BM), BCS and various morphometric measurements were recorded. Following euthanasia, all ponies were systematically dissected. Discrete white adipose tissue (WAT) depots were independently described. Gross, body chemical composition was determined by proximate analyses.

RESULTS

Total somatic soft tissues increased linearly (r(2) = 1.00), whereas body WAT content (1-26% live BM) increased exponentially (r(2) = 0.96), with BCS. WAT was equally distributed between internal and external sites in all animals irrespective of BCS. Nuchal fat was a poor predictor of total WAT (r(2) = 0.66). Periorbital WAT did not alter with BCS (r(2) = 0.01). Heart girth:withers height and ultrasonic retroperitoneal fat depth were closely associated with total, chemically-extracted lipid which comprised 1-29% live BM (r(2) = 0.91 and 0.88, respectively).

CONCLUSIONS AND POTENTIAL RELEVANCE

The exponential relationship between BCS and total body WAT/lipid suggests that BCS is unlikely to be a sensitive index of body fat for animals in moderate-obese states. Morphometric measurements (body girths and retroperitonel fat depth) may be useful to augment subjective BCS systems.

Muscle growth and distribution of muscle weight in Clun and Southdown sheep

A total of 56 sheep, 28 Clun and 28 Southdown were slaughtered, five of each breed, at birth, 50, 100, 150 and 200 days and three of each breed at 415 days of age. The left half of each carcass was separated anatomically into individual muscles, bones and fat depots. For the purposes of analysis, individual muscles were assigned to one of eight muscle groups, depending upon their anatomical location.

The relative growth of some individual muscles was found to change over this age range, as indicated by a significant squared term in the quadratic allometric equation: this was true for proportionately 0·33 of the muscles in Clun and for proportionately 0·44 of those in Southdown, accounting for proportionately 0·33 and 0·47 of total muscle weight in Clun and Southdown respectively.

Principal components analysis (PCA) was used to derive the multivariate analogue of the quadratic part of quadratic allometry: the sign of the loading on the second principal component had the same sign as the change observed in bq, the quadratic relative growth coefficient. Thus, PCA offers the potential to identify simultaneously, and independently of shape or conformation, all those muscles whose relative growth coefficients change over the period examined. It could be applied successfully to breed comparisons of conformation.

The cumulative effects of changing relative growth rates of muscles were small. Muscle weight distribution appears to be almost fixed within the first few weeks after birth. Despite their differences in conformation and mature size, Clun and Southdown lambs had similar distributions of muscle weight at the same age; the high valued muscles constituted 513·8 g/kg total muscle in Clun and 514·7 g/kg total muscle in Southdown lambs at 200 days of age.

Relationship of body condition score and live weight with body composition in mature Churra ewes

Thirty-five mature Churra ewes, ranging in live weight from 30·3 to 52·6 kg and in body condition score from 1·25 to 4·00 were used to study the relationship between body condition score (BCS), live weight (LW) and body composition and fat distribution in ewes of this breed, which is one of the major sheep breeds of northern Spain. The procedure at slaughter and at subsequent dissection was designed to partition each body into two components, carcass and ‘non-carcass’. Right side carcasses and ‘non-carcass’ components were used to analyse the chemical composition. From the left side of the lumbar region a joint was cut and dissected into muscle, bone, subcutaneous and intermuscular fat. According to the results obtained, omental fat represented the highest proportion of total internal fat regardless of the level of fatness. Distribution of internal fat was similar to that observed in other milk production breeds. Regressions on LW explained more of the variation than those on BCS for individual internal fat depots and chemically determined ‘non-carcass’ fat. The prediction of total body fat afforded by LW was better than that provided by BCS. The subcutaneous and intermuscular fat depots in the lumbar joint were well correlated with BCS, carcass fat and total fat in the body, validating the use of this region for assessing BCS in Churra ewes. Nevertheless, the correlation coefficient with the omental depot was not statistically significant. The results of this study suggest that BCS was not as accurate for estimating body composition and fat depots in mature Churra ewes as has been shown previously in other breeds. The single most effective prediction index was LW. However, the utilization of both BCS and LW together provided more accurate estimations.

Breed and sex differences among equally mature sheep and goats 4. Carcass muscle, fat and bone

Males and females from Soay, Welsh Mountain, Southdown, Finnish Landrace, Jacob, Wiltshire Horn and Oxford Down sheep breeds and a breed of feral goats were slaughtered when proportionately 0·40, 0·52, 0·64 or 0·76 of mature live weight. On average, carcasses contained 583 g muscle, 243 g fat and 174 g bone per kg. Individual cuts (four commercially higher-valued and six lower-valued cuts of the shoulder, rib, loin and gigot joints) ranged from 375 to 670g muscle, 129 to 625 g fat and 0 to 294 g bone per kg.

Allometric coefficients are given for 32 traits. The distribution of bone in the carcass joints changed little as animals matured but carcass muscle and fat distributions changed significantly.

Breeds differed significantly in proportion of carcass muscle, fat and bone and also in their distribution. Welsh Mountain, Southdown, Wiltshire and Oxford Down all deposited carcass fat about three times more rapidly than did the Soay, goat, Finnish Landrace and Jacob. The Oxford Down had the lowest proportion of muscle (514 g/kg) and most fat (317 g/kg). The Southdown had least bone (148 g/kg) and the feral goat most muscle (662 g/kg). Southdown and Soay had the most muscle in commercially higher-valued cuts and Jacob and feral goat the least. Males had significantly more of their muscle in the neck and shoulder and significantly less in the gigot and flank.

As breed size increased, proportion of carcass muscle and bone decreased and proportion of carcass fat increased. These breed regressions were attributed to the small but exceptionally lean feral Soay and goat breeds, rather than to a failure of genetic size-scaling. There were no significant trends with breed size among the domesticated breeds.

Bovine growth hormone in lambs: effects on carcass composition and tissue distribution in crossbred females

Thirty-two Dorset Down × Finn Dorset female lambs were reared from 8 to 20 weeks on an ad libitum concentrate diet. They comprised four groups of eight lambs, one on each of the following treatments: (1) control, no injections; (2) daily subcutaneous injection of 0-1 mg bovine pituitary growth hormone (bGH) per kg live weight; (3) daily subcutaneous injection of 1 mg bromocriptine mesilate (Br); (4) daily injections of both bGH and Br at the same rates as treatments (2) and (3).

There were no important differences in carcass composition or tissue distribution between the +bGH and +bGH+Br lambs or between the control and +Br lambs. The +bGH lambs (+bGH and +bGH+Br lambs pooled) contained significantly greater proportions of lean and bone compared with the −bGH lambs (control and +Br lambs pooled). Although carcass composition was altered by bGH treatment, the distribution of individual tissues (lean, bone and fat) was not influenced significantly.

Carcass quality was improved markedly by bGH treatment: subcutaneous fat depth was reduced and the area of the m. longissimus lumborum increased. +bGH carcasses would be ranked one fat class less on the Meat and Livestock Commission fatness scale than −bGH carcasses at the same carcass weight.

Food intake, growth and body composition in Australian Merino sheep selected for high and low weaning weight 4. Partitioning of dissected and chemical fat in the body

Changes in the partitioning of both dissected and chemical fat were examined from birth to maturity, in rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock. The partitioning of fat between six dissected and 11 chemical fat partitions in the body was examined in 34 mature animals, and the maturing patterns for these fat partitions calculated relative to the weight of total body fat, using the mean values for the mature animals and individual data from 106 immature animals.

Strain had no effect on the partitioning of dissected fat in the mature animals, but did affect the partitioning of chemical fat in the bone and pelt partitions. Mature ewes had greater proportions of dissected subcutaneous and kidney fat, and lower proportions of dissected intermuscular and scrotal/udder fat, than the mature rams.

There were significant strain and sex effects on maturing patterns for dissected subcutaneous and intermuscular fat. Strain and sex effects were also significant for the maturing patterns of some chemical fat partitions.

Selection for high or low weaning weight had little effect on the partitioning of either dissected or chemical fat when compared at the same stage of maturity of total fat. There were large differences in the partitioning of both chemical and dissected fat between the rams and the ewes when compared at either the same weight of total fat, or the same stage of maturity of total fat in the body.

Growth and body composition of Omani local sheep 1. Live-weight growth and carcass and non-carcass characteristics

Forty-five local Omani ram, wether and ewe lambs were reared from birth until slaughter at 18, 28 or 38 kg live weight (five of each ‘sex’ at each weight group) on an ad libitum concentrate diet and Rhodesgrass hay.

Ram lambs grew faster from birth and reached predetermined slaughter weights earlier than wether and ewe lambs. At 28 kg live weight, ram lambs had: heavier heads, feet, reticulo-rumens and livers; higher muscle and bone and lower fat proportions in the carcass; lower muscle: bone and higher muscle: fat ratios; higher proportions of carcass but lower non-carcass fat than had wether and ewe lambs. The head, feet, alimentary tract, liver and heart of Omani sheep grew at a lower rate; the skin grew at a similar rate and the carcass grew at a rate faster than empty body weight (EBW). Relative to EBW, muscle grew at a similar rate, fat faster and bone slower. Both carcass and non-carcass fats grew at a rate higher than that of the growth of EBW, with non-carcass fat growing at a higher rate than that of carcass fat. The growth rate of omental fat was the fastest followed by kidney, mesenteric, subcutaneous, tail, scrotal, intermuscular and pelvic fats respectively.

This study demonstrated that Omani sheep have good potential for growth if they are managed and fed satisfactorily. Omani sheep are early maturing for which reason it is recommended that they be slaughtered at lighter weights to avoid higher fat content in the carcass. Castration in Omani sheep is not recommended for production of meat lambs under intensive systems as it resulted in reduced growth rates and deposition of excess fat at lower slaughter weights.

The effect of pattern of food supply on performance, compensatory growth and carcass composition of Beulah and Welsh Mountain lambs

Seventy-eight Beulah (BH) and 78 Welsh Mountain (WM) wether lambs (mature live weights (MLW) 60 and 70 kg respectively), were used to investigate genotypic differences in performance and compensatory growth during the post-weaning period. After an initial slaughter of 12 of each breed, a complete straw-based pelleted diet (122 g crude protein and 10·4 Mj metabolizable energy per kg dry matter (DM)) was offered ad libitum to a further 29 of each which were slaughtered at a range of live weights between proportionately 0·35 andl -00 of ML W. As well as these groups undergoing normal growth (NG), the remaining lambs were given the same diet at a level sufficient to maintain constant live weight (LW) for 3 months. Eight of each breed were then slaughtered and the remaining 29 of each offered the diet ad libitum for a period of post-restricted growth (PRG); these 29 were also slaughtered between 0·35 and 1·00 of MLW. During the periods of ad libitum food supply, voluntary food intake was greater in BH than WM lambs (BH: 38·3, WM: 35·3 g DM per kg LW, P < 0·01) and during PRG as compared with NG although this result was due to a response only in WM lambs (NG - BH: 38·0, PRG-BH: 38·5, NG - WM: 33·3, PRG - WM: 37·2 g DM per kg LW, breed × pattern of food supply interaction, P < 0·05). Daily live-weight gain (LWG) was greater during PRG than NG in both breeds (NG: 3·15, PRG: 4·80 g/kg LWper day, P < 0·05). This effect was greatest in the first 8 weeks of growth but persisted into the period 16 weeks to maturity. WM lambs had overall slightly leaner carcasses and a lower proportion of protein in the fleece-free empty body than BH when compared at the same proportion of MLW; particularly during PRG. The protein in the carcass-weight gain (CWG) was greater in WM lambs during PRG than during NG (NG: 98, PRG: 123 g/kg, P < 0·05), but did not differ significantly in BH (NG: 106, PRG: 118 g/kg). The proportion of fat in CWG was concomitantly smaller during PRG. There are thus breed differences in the performance and carcass composition of lambs during compensatory growth. Genotypes to be finished by continuous feeding or a regimen incorporating food restriction should be carefully chosen for date offinishing in relation to desired carcass composition.

Breed and sex differences among equally mature sheep and goats 6. Breed correlations for body composition and food conversion efficiency

Breed means are given for 40 traits relating to food conversion efficiency and body composition at the same stage of maturity in seven breeds of sheep and a feral goat breed. In terms of breed means, food intake and food conversion efficiency were genetically correlated, as were most traits associated with fatness or leanness.

Highly inter-correlated measures of breed fatness were proportion of fat in the carcass, proportion of total carcass fat found in the rib plus loin, the fat : muscle ratio and the lipid concentration in the dry matter of all tissues except bone. Dressing proportion was highly correlated with all these measures of fatness.

Breeds with a high proportion of subcutaneous fat did not necessarily have a low proportion of intra-abdominal fat. A low proportion of carcass fat in the rib plus loin was associated with a high proportion in the shoulder (inter-breed correlation —0·7): both were measures of leanness. Muscle : bone ratio was not correlated with fatness or leanness. Slower maturing, larger breeds had slightly more bone, less fat and more lean in their higher-priced cuts. Breeds with heavier fleeces were fatter (0·7). The food conversion efficiency of a breed was largely independent of its body composition.

Fat partitioning and tissue distribution in crossbred ewes following different growth paths

Forty Hampshire Down × Mule (Blue-faced Leicester cf × Swaledale 2) ewe lambs, obtained within a week of birth, were reared on milk replacer and from 6 weeks of age on a complete pelleted diet. Food intake of individual lambs was controlled to produce periods of high (H: ca. 210 g/day) and low (L: ca. 110 g/day) rates of live-weight gain from 4 to 20 and 20 to 36 weeks of age. Groups of eight lambs were slaughtered and dissected at 20 weeks having followed either growth paths H or L, and at 36 weeks having followed growth paths LL, HL or LH.

Growth path had little effect on the lean or bone content of the carcass, but had a significant effect on carcass fat content and distribution. At the same carcass weight, the ratio of intermuscular to subcutaneous fat was higher in leaner carcasses. When compared at the same weight (ca. 35 kg) but different ages (H, 20 weeks; LL 36 weeks), the slower growing LL lambs contained 1·22 kg more fat than the H lambs, primarily in the intermuscular and subcutaneous depots but also in the internal omental depot. At the same age and weight (ca. 36 weeks and 48 kg), lambs which had followed the growth path LH contained 2·5 kg more fat than lambs which had followed the HL path. These differences in fatness are thought to have come about through changes in the effective protein:energy ratio of the diet, induced by the manipulation of food intake.

Carcasses of HL lambs would be of more value to the meat trade compared with LH, since they would require less fat trimming before retail sale.

The allometric hypothesis when the size variable is uncertain: issues in the study of carcass composition by serial slaughter

The allometric hypothesis which relates the shape (y) of biological organs to the size of the plant or animal (x), as a function of the relative growth rates, is ubiquitous in biology. This concept has been especially useful in studies of carcass composition of farm animals, and is the basis for the definition of maintenance requirements in animal nutrition.

When the size variable is random the differential equation describing the relative growth rates of organs becomes a stochastic differential equation, with a solution different from that of the deterministic equation normally used to describe allometry. This is important in studies of carcass composition where animals are slaughtered in different sizes and ages, introducing variance between animals into the size variable.

This paper derives an equation that relates values of the shape variable to the expected values of the size variable at any point. This is the most easily interpreted relationship in many applications of the allometric hypothesis such as the study of the development of carcass composition in domestic animals by serial slaughter. The change in the estimates of the coefficients of the allometric equation found through the usual deterministc equation is demonstrated under additive and multiplicative errors. The inclusion of a factor based on the reciprocal of the size variable to the usual log - log regression equation is shown to produce unbiased estimates of the parameters when the errors can be assumed to be multiplicative.

The consequences of stochastic size variables in the study of carcass composition are discussed.

Carcass composition and meat quality of brush-tail possums (Trichosurus vulpecula)

One-hundred-and-thirty-nine possums, balanced as far as possible for sex (68 male, 71 female) and age (1 year, 42; 2-4 years, 61; 5+ years, 36), were slaughtered and the dissected carcass composition, muscle, and cooked meat composition measured. Possums were slaughtered at time in captivity TIC 0 (n = 58), TIC 14 days (n = 20) and TIC 28 days (n = 61). Compared with the 5+ years (mature) age group the 1 year olds (juveniles) were 67% and the 2-4 year olds (immature) 96% of the live weight of the mature possums. Carcass composition was characterised by high lean (78-80%) and low fat (around 1-2%). The cooked meat from possums is very high in protein (∼ 25%) and low in fat, suggesting it should be a valuable source of animal protein with a low total fat, high unsaturated fat content. In all cases cooked meat was rated as tender, based on shear force values, despite having a pH of around 6·3.