Heavier Slaughter Weights Research Articles

The effect of sire genotype on the histochemical profile of theM. longissimus dorsiof pigs slaughtered at a heavy weight and its relationship with meat colour

Over the last twenty years, pig breeding has been very successful in the selection for improved lean meat production and reduced fat level. In order to meet increasing pressure to reduce fatness and increase muscularity in fatteners different types of meat boars are used by pig producers instead of traditional sires (Landrace, Large White or Duroc). There is some concern that meat and eating quality have suffered as a result of this strong use of meat boars. According to Warriss (2000), specifically the presence of Pietrain genes in many meat-line boars could potentially make their offspring more prone to the production PSE meat. Colour is the major determinant of appearance of raw meat. It can be determined by two main factors – the first is the concentration of the haem pigments, myoglobin and haemoglobin - the second is the muscle microstructure. Heavier slaughter weights have become a feature of a number of markets. Therefore, the objective of this work was to study the effect of sire genotype on the histochemical profile of theM. longissimus dorsifrom pigs slaughtered at a relatively heavy weight the 129.3 kg.

Meat quality of entire and castrated male Boer goats raised under Australian conditions and slaughtered at different weights: physical characteristics, shear force values and eating quality profiles

AbstractCastrated and entire Boer bucks (no. = 60) in groups of between three and five animals were slaughtered at 5,15, 30, 45, 60, 75, 90 and 105 kg live weight (5- and 15-kg animals were not castrated). Ultimate pH, muscle colour (subjective and objective measurement), subcutaneous fat colour, total pigment concentration, shear force values and eating quality were investigated. The ultimate pH o/longissimus muscle increased from 5-7 to 6-2 (P < 0-05) as animals were slaughtered at heavier weights. Slaughter weight had an influence on chromameter muscle colour (L*, a*, b* values) and subjective muscle colour scores recorded using a nine-point colour scale (P < 0-05) for both entire and castrated bucks. Muscle redness (a* values) and subjective muscle colour scores increased gradually in older animals while muscle lightness and yellowness (L* and b* values) decreased. Subcutaneous fat colour became more yellow at heavier slaughter weights (P < 0-05). Shear force values were affected (P < 0-05) by slaughter weight but not by castration of bucks. All eating quality scores were influenced by slaughter weight but not by castration, and flavour, as predicted by eating quality scores, was the most important attribute that contributed to overall acceptability of the goat meat.

Effects of dietary lipid type on muscle fatty acid composition, carcass leanness, and meat toughness in lambs.

Isonitrogenous amounts of two protein sources differing in rumen degradation rate and in lipid composition were fed to sheep with or without a rapidly fermentable cereal grain. The effects on intake, carcass leanness, and muscle fatty acid (FA) composition were examined. Thirty-eight crossbred wether lambs (9 mo, 35 to 48 kg) were allocated by stratified randomization to six treatment groups: 1) basal diet of alfalfa hay:oat hay (20:80) ad libitum = basal; 2) basal + lupin (358 g DM/d) = lupin; 3) basal + fish meal (168 g DM/d) = fish meal; 4) basal + barley (358 g DM/d) = barley; 5) basal + barley + lupin (179 + 179 g DM/d) = barley/lupin; or 6) basal + barley + fish meal (179 + 84 g DM/d) = barley/ fish meal. Lambs were fed individually. Dietary treatments were imposed for 8 wk, and the supplements were offered at 2-d intervals. Daily feed intake and weekly BW of lambs were recorded. At the end of the feeding period lambs were slaughtered after an overnight fast. Hot carcass weight (HCW) and fat depth (GR; total fat and muscle tissue depth at 12th rib, 110 mm from midline) were recorded. At 24 h postmortem samples of longissimus thoracis (LT) and longissimus lumborum (LL) muscles were taken from chilled (4 degrees C) carcasses for the assessment of FA composition and meat tenderness, respectively. Lambs fed lupin or fish meal with or without barley had heavier slaughter weights (P < 0.004) and HCW (P < 0.001) than lambs fed basal or barley when initial BW was included as a covariate. The lupin diet also resulted in heavier carcasses (P < 0.05) than the fish meal or barley/fish meal diets. With GR as an indicator, fish meal and barley/ fish meal diets produced leaner carcasses (P < 0.01) than lupin and barley/lupin lambs. Long-chain n-3 FA content [20:5n-3 (P < 0.001), 22:5n-3 (P < 0.003), and 22:6n-3 (P < 0.001)] in the LT muscle were substantially higher with the fish meal and barley/fish meal diets, whereas muscle total n-6 FA was increased (P < 0.003) by lupin and barley/lupin compared with all other diets. Thus, increased muscle long-chain n-3 FA content occurred without an increase in fatness measured as GR, whereas increased muscle n-6 FA content was associated with an increase in carcass fatness. Under these circumstances, a reduction in carcass fatness had no effect on meat tenderness measured as Warner-Bratzler shear force.

Influence of slaughter weight and sex on yield and quality grades of Hanwoo (Korean native cattle) carcasses.

To assess the effects of slaughter weight and sex on APGS (Animal Products Grading Service) quality and APGS yield grade of Korean Hanwoo (n = 20,881) cattle, data were collected from cow, bull, and steer carcasses during a 1-yr period. Factors used to determine quality grade (marbling, meat color, fat color, texture, and overall maturity score) and yield grade (cold carcass weight, adjusted fat thickness, and longissimus muscle area) by the Korean grading system were recorded. Both yield and quality grades were improved (P < 0.01) with heavier slaughter weight, but there was no difference in yield grade for Hanwoo cattle classes heavier than 551 kg (P > 0.01). Longissimus muscle area, adjusted fat thickness, and marbling score increased (P < 0.01) with carcass weight. Bull carcasses showed higher yield but lower quality than those of cows or steers (P < 0.01). The quality grade of steer carcasses was higher (P < 0.01) than that of cow carcasses due to higher marbling scores, lower maturity scores, and heavier carcass weights. Hanwoo carcasses with larger longissimus muscle areas in relation to their carcass weight had lower APGS quality grades. The APGS quality grades were different between yield grade A and B carcasses (P < 0.01), but quality grade was not improved by increased fat thickness beyond the point of yield grade B. Adjusted fat thickness and marbling score showed significant (P < 0.01) differences among all yield grade classes, and this resulted in increased quality grade as yield grade decreased. Adjusted fat thickness showed the strongest correlation (r = -0.63) with yield grade, whereas marbling score had the strongest correlation (r = 0.81) with quality grade. Results showed a negative effect of castration on yield but a positive effect on quality. Also, data showed that Hanwoo carcasses with heavier weights had higher quality grades than those of lighter weight.

Meat production from female goat kids compared with males

Twelve female desert goat kids and an equal number of males were used to study meat production potential of desert goats at Kuku Research Station, Khartoum North, Sudan. The kids were kept in two separate groups according to sex. Kids were fed ad libitum a complete diet (a concentrate mix and green lucerne) for 147 days from 12 July to 10 Oct 1997.Male kids consumed more dry matter, had significantly greater liveweight gain and had heavier slaughter weight and superior feed conversion efficiency than females. Carcass weight was significantly greater in males than females but females dressed out heavier than males. Male carcasses had more muscles and bone while female carcasses had more fat and trimmings.Male goat kid carcasses yielded significantly (P&lt;0·001) heavier wholesale cuts as single short forequarter and neck while female kid carcasses yielded heavier wholesale cuts as leg and chump, best end of neck as well as significantly (P&lt;0·01) heavier loin and breast.

The effect of increasing slaughter weight on the production performance and meat quality of finishing pigs

AbstractA study was made in two parts to establish the production performance potential of pigs taken to heavy slaughter weights (a) in individual housing and (b) in group housing. In experiment 1 96 crossbred pigs, comprised of equal numbers of boars, castrated males and gilts, were housed individually from 50 kg live weight and offered foodad libitumuntil one of four target slaughter weights was reached (70, 80, 90 or 100 kg carcass weight). Detailed dissection and meat quality assessments were performed on sample joints taken from these pigs. There were significant interactions in that boars maintained a high level offood conversion efficiency while this deteriorated at heavier weights for castrated males and gilts. Protein deposition rates (PDR) were estimated to be close to, or in excess of, 200 glday for boars. Daily live-weight gains were similar at all four slaughter weights despite increases (P&lt; 0·001) in daily food intake at the heavier weights. Sample joint contents of lean (P&lt; 0·05) and bone (P = 0·001) decreased while subcutaneous fat content increased (P&lt; 0·001) with increasing slaughter weight. Cooking loss was reduced (P&lt; 0·001) at the heavier weights while other meat quality parameters were not significantly affected by slaughter weight or gender. In experiment 2 288 group-housed boars and gilts were slaughtered at the same four target carcass weights as in experiment 1. Daily food intake, daily live-weight gain and variability in performance were lower for group-housed animals. It is concluded that maximum lean growth lies beyondad libitumfood intake for group-housed pigs of the genotype used in the present study. There are opportunities to take pigs to high slaughter weights with no reduction in daily live-weight gain and concomitant improvements in some aspects of meat quality.

Effect of halothane genotype on porcine meat quality and myoglobin autoxidation

The objective of this study was to determine effects of light (40–80 kg) or heavy (100–130 kg) slaughter weight and halothane status (positive, nn; negative, NN; and heterozygous, Nn), on meat quality. Longissimus muscle (LM) pH at 45 min (pH 45) post-exsanguination was 6.25, 6.03, and 5.84 (different at p < 0.01) for NN, Nn, and nn genotype, respectively. At heavier weights (100–130 kg), genotype correlated ( r = −0.71) with LM pH 45, 10th costae LM (TENLM) color score ( r = −0.55), TENLM Hunter L ∗-value ( r = 0.47), water holding capacity ( r = 0.42) and TENLM subjective firmness-wetness score ( r = 0.51). Rate constants for metmyoglobin accumulation and oxymyoglobin autoxidation, indicators for fresh meat color stability, increased ( p < 0.05) with decreasing pH. Color stability for NN muscle was more stable than nn muscle ( p < 0.05). Electrofocusing of myoblobin revealed two bands (MW 17.10 3) at pI 6.1 and 6.5 across genotypes. Because differences were not observed across genotypes, an observed increase ( p < 0.05) in 24 hr myoglobin autoxidation rate constant (associated with increased expression of the HAL gene) are presumed dependent upon post-mortem muscle changes. These data show that changes in halothane status affect fresh pork quality and that lowered meat quality results in further color destruction due to altered chemical reactions involving myoglobin oxidation.

Estimating the Values of Cattle Characteristics Using an Ordered Probit Model

AbstractIn this study we evaluate the preferences of cattle producers in Manitoba, Canada, for different cattle characteristics using the conjoint analysis methodology. Preferences are estimated for three different segments of the cattle production system: purebred breeders, commercial cow‐calf producers, and cattle feeders. Data were collected for steers and bulls via a mail survey in 1993. Here we provide relative valuation for the different characteristics by segment of the cattle sector. Evidence is provided that different segments of the cattle sector do not value characteristics the same. For example, purebred breeders have higher preferences for reproduction traits, while feedlot operators give higher values to commercial attributes such as heavy slaughter weight and carcass yield. The different valuations of characteristics across segments of the cattle sector suggest that signals regarding preferences may be noisy. As a result, it might be difficult to design some breed improvement programs to be broadly acceptable, if they have differential benefits to the different segments of producers, when using standard profit‐oriented selection indices.

Growth and carcass characteristics of heavy slaughter weight lambs: effects of sire breed and sex of lamb and relationships to serum metabolites and IGF-1

AbstractTexel (T) and Suffolk (S) sired ram, wether and ewe lambs (no = 180) were kept at grass with their dams until weaned at 20 weeks and then taken to slaughter weights of 40, 44 and 48 kg, also at grass. Sex type, but not sire breed, affected lamb growth rate (rams 293, wethers 253, ewes 224 g/day; P &lt; 0·001). Both T and S ewe lambs were fatter at slaughter in all fat depots compared with their ram and wether siblings such that rams could be slaughtered at a calculated 7·7 kg greater live weight than ewes at equal carcass fat cover. T carcasses were greater than S carcasses in eye-muscle area (793 v. 732 mm2; P &lt; 0·001) and killing-out proportion (481 v. 476 g/kg; P &lt; 0·05) but not in any fat measurement. Slaughter weight influenced killing-out proportion (P &lt; 0·001) and all fat measurements (P &lt; 0·01) but did not significantly affect eye-muscle area.Mean serum insulin-like growth factor-1 (IGF-1) concentrations (μig/l), determined during weeks 8,11, 14, 17 and 20 in a balanced subset of 84 lambs, were higher in T than in S lambs (P &lt; 0·05), in singles than in twins (P &lt; 0·01; rams and wethers only) and in rams than in either wethers or ewes (P &lt; 0·001). Mean serum IGF-1 concentration decreased between week 8 and week 20 with a greater rate of decline in singles than in twins (P &lt; 0·001). IGF-1 was more strongly correlated with live weight at 8 weeks (r = 0·629; P&lt; 0·001) than at 20 weeks (r = 0·293; P &lt; 0·05). Mean IGF-1 (weeks 8 to 20) was correlated with rate of live-weight change (r = 0·576; P &lt; 0·001). Significant differences for T and S lambs were found in the relationships between mean serum IGF-1 (weeks 8 to 20) and daily live-weight gain (weeks 8 to 20) and between mean IGF-1 and eye-muscle area at slaughter. Metabolite concentrations differed little between sire breeds and not at all between sex types.

Survival, body weights, feed efficiency, and carcass traits of 3/4 white composite and 1/4 Duroc, 1/4 Meishan, 1/4 Fengjing, or 1/4 Minzhu pigs.

Pigs were the progeny of White Composite (WC) boars mated to F1 Duroc x WC, Meishan x WC, Fengjing x WC, and Minzhu x WC gilts. Meishan and Fengjing crosses had more (P < .05) nipples than Duroc and Minzhu crosses. Meishan and Minzhu crosses had a higher survival rate at birth (P < .05) than Duroc and Fengjing crosses, but breed types did not differ significantly (P approximately .29) for survival to 14 or 28 d of age. Duroc crosses were heavier (P < .05) than Fengjing and Minzhu crosses at 0, 28, 56, 70, 98, 126, and 154 d of age; they were heavier (P < .05) than Meishan crosses at 0, 28, 98, 126, and 154 d of age. Chinese crosses had similar weights at most ages, although Meishan crosses were heavier (P < .05) than Fengjing and Minzhu crosses at 126 and 154 d of age. Breed types did not differ significantly (P approximately .27) for feed efficiency during the nursery period. Over the entire finishing period, Duroc-cross gilts (.3310) were less efficient (P < .05) than Meishan (.3436), Fengjing (.3454), or Minzhu crosses (.3466); among barrows Meishan crosses (.3176) were least efficient (P < .05), Fengjing crosses (.3263) were most efficient (P < .05), and Duroc (.3211) and Minzhu (.3209) were intermediate but not significantly different from the Meishan or Fengjing crosses. At a constant age, Duroc crosses had longer carcasses, greater longissimus muscle area, and heavier slaughter weight, carcass weight, and weight of untrimmed cuts and trimmed cuts than the Chinese crosses (P < .05). There were few significant differences among breed types for carcass traits at a constant carcass weight. Results show that, relative to one-half Duroc females, incorporation of one-half Chinese females into a crossbreeding program will result in progeny with a significant decrease in rate of growth (approximately 9% for weight at 154 d of age) and a small, nonsignificant decrease in yield of trimmed lean cuts (approximately 5%) at a constant carcass weight.

The food intake, performance and carcass characteristics of two pig genotypes grown to 120 kg live weight

AbstractUsing a completely randomized design, 72 individually penned pigs, comprising two genotypes (Masterbreeders Mastergilt × Large White and Sovereign × Large white progeny) with equal numbers of boars and gilts, were given foodad libitumfrom 25 to 60 kg live weight. From 60 to 120 kg one-third of the pigs continued to be given foodad libitumwhilst the remainder were given one of two levels of restriction (0.85 and 0.925 of maintenance energy × 3.5). Diets were calculated to provide 13.8 and 13.0 MJ digestible energy (DE) per kg air-dry weight for growing and finishing phases respectively. Ultrasonic measurements of backfat at the P2 site were made at 10 kg intervals from 60 to 120 kg live weight and carcass measurements taken at slaughter. Complete dissection of ham joints was carried out. Predictedad libitumintakes were based on established equations but daily intakes were much lower than these values and no treatment provided food restriction compared with them. Daily DE intakes (mean of both genotypes) obtained at 25, 60, 90 and 120 kg live weight were 204, 30.7, 36.2, and 414 MJ (i.e. 3.5, 3.1, 2.9 and 2.7 × maintenance). During the growing (25 to 60 kg live weight) and finishing (60 to 120 kg live weight) periods boars grew faster (P&amp;lt; 0.01 andP&amp;lt; 0.001) than gilts (881v.827 and 944v.806 g/day) with corresponding improvements in food conversion ratio (P&amp;lt; 0.001). Boars had lower killing-out proportions (0.787v.0.801;P&amp;lt; 0.001). Mean P2 values for boars and gilts were 13.2 and 13.9 mm respectively (excluding skin). Greater quantities of muscle were found in the hams of boars than gilts (662.7v.642.3 kg;P&amp;lt; 0.05) but no difference between the sexes for ‘eye muscle’ area was observed (43.3v.45.0 cm2). Results show the apparent potential of modern hybrids to achieve good growth rates despite moderate food intakes and their ability, even when given continuous access to food, to produce very lean carcasses at relatively heavy slaughter weights.

Relationship of Body Measurements with Meat and Skin Yield Characteristics in Free Range Reared Bengal Goats

Abstract Three hundred free range reared Bengal goats (122 males and 178 females) were slaughtered after recording age, body weight, ear length, heart girth, shank length, loin spread and after slaughter, skin length, skin breadth, blood loss and dressed carcass yield were recorded to establish relationship among these parameters. The males had greater individual variations in linear body measurements than that in females. Despite older age, heavier slaughter weights and greater skin area, females had lower dressing yield and slightly lighter skin (P>0.05) than in males. The correlations indicated body length, heart girth, ear length, shank length and loin spread as reliable independent predictors of body weight and, therefore, of dressing yield.

Effect of Crossbreeding and Mating System on Slaughter Performance and Meat Quality in Three Breed Diallel Crosses of Rabbits

Abstract Sixty five rabbits, representing three breeds (New Zealand White, Californian and Baladi) and their crosses, were used to determine the influence of purebred vs. crossbred as well as mating system on slaughter performance, carcass traits and meat quality. The New Zealand White male and female lines were the heaviest in slaughter weight and carcass traits. The crossbred rabbits had heavier slaughter weight (1.99 kg), middle part weight (244.54 g) and head weight (108.87 g) as compared to purebred rabbits (1.91 kg, 221.50g, 100.63 g respectively) and the differences were highly significant. Crude protein and ether extract were of the same order in all classes. Moisture and ash were significantly affected by male rabbit line, while female line had only a significant effect on ash percentage. The purebred vs. crossbred rabbits had only significant effect on ash percentage. Highly significant phenotypic correlations were found between different carcass traits. There were no phenotypic correlations bet...

Correlated responses in slaughter and carcass traits of crossbred progeny to selection for carcass lean content in sheep

AbstractCorrelated responses in slaughter and carcass traits to divergent selection for high or low carcass lean content in Texel-Oxford sheep were measured in the crossbred progeny of 23 rams. Rams were selected using the selection index: -0·995 FATD + 0·206 WT20, where FATD and WT20 are the ultrasonic backfat depth and live weight at 20 weeks of age, with both traits standardized to have zero mean and unit phenotypic variance. A total of 329 crossbred lambs were slaughtered at 16 weeks of age and 250 lambs were slaughtered at fixed weight, 38 to 40 kg for castrated males and 36 to 38 kg for ewe lambs. Progeny from high-line rams grew faster, as indicated by the heavier slaughter weight of lambs slaughtered at fixed age (04 (s.e.d. 0·5) kg) and the lower age at slaughter for lambs slaughtered at fixed weight (-5 (s.e.d. 3) days). Subcutaneous and internal fat scores and the Meat and Livestock Commission carcass appraisal and conformation scores were all lower in the high line than in the low line and the magnitude of the selection line differences for lambs slaughtered at fixed weight was essentially double that of lambs slaughtered at fixed age (0·8 v. 0·5 score units).Shoulder joints of 254 lambs, slaughtered at fixed age, were dissected and half carcasses were dissected on 66 of the lambs. Carcass and shoulder joint information was combined with double-sampling methodology, using multiple regression equations to predict carcass composition. For each tissue type, viz. lean, subcutaneous fat, internal fat and bone, the correlations between carcass content and shoulder joint content were at least 0·90 and the proportions of variation in carcass tissue content accounted for by the prediction equations were also at least 0·90. Progeny of high-line rams had higher carcass lean weight, (402 (s.e.d. 140) g) than progeny from the low line, with no difference in carcass fat weight, such that carcass lean content was higher, (10 (s.e.d. 5) g/kg), and carcass fat content was lower, (-10 (s.e.d. 7) g/kg). Based on the slaughter and carcass traits of these crossbred progeny, divergent selection for high and low carcass lean content has established lines of animals with different rates of lean growth but similar rates offat deposition.

The voluntary feed intake of modern pig genotypes

The continued genetic improvement for lean tissue growth rate and efficiency of pig production has allowed the liberal feeding of modern pigs without adverse effects on carcass quality or food conversion efficiency, even at heavy slaughter weights (Cole and Chadd, 1989; Webb, 1989). This genetic improvement has, however, been associated with a reduction in appetite so that the food intake of modern genotypes of pigs cannot be precisely assessed from the prediction equations established for the older and fatter genotype of pigs. The present experiment was designed to measure voluntary feed intake in order to facilitate the establishment of nutrient requirements and feeding strategies for modern pig genotypes.

Dietary factors affecting voluntary food intake in growing and finishing pigs

Ad libitum feeding provides the opportunity for animal scientists to explore the genetic and environmental factors which determine voluntary feed intake, a greater knowledge of which could help increase potential appetite thereby raising the level at which the latter may limit productivity. A Braude Travel Scholarship was used to finance a visit to a number of research establishments based in the Netherlands, Denmark and France to observe the extent to which diet and related factors are examined through experimentation, the results of which may contribute to our understanding of the mechanisms of feed intake control. Major differences in the production systems encountered in these countries when compared with the UK include the greater emphasis given to current environmental issues, expression of dietary energy as NE, production of castrated males, heavier slaughter weights and associated export demands. Such factors substantially influence the direction taken by nutrition research programmes. Although the primary purpose of the study tour was the appraisal of dietary factors in relation to food consumption, such effects could not be considered in isolation from associated genetic, physiological and environmental aspects, hence their inclusion in this report.

Influence of heavy slaughter weights on growth and carcass characteristics of pigs

Slaughter weights for pigs in the United Kingdom have traditionally been much lower than those in most other European countries and in North America. For example, in 1988 average carcass weights in the UK were around 64 kg compared to 72 kg in Denmark, 80 kg in Holland and over 105 kg in Italy. Currently, there is considerable interest within the BritisTi pig industry in heavier slaughter weights for pigs to exploit potential advantages in reducing fixed costs of production per unit of output. A research programme is currently being undertaken at this centre to investigate the potential for increasing slaughter weight and results from the first two studies undertaken are reported here.

The effects of different factors on the levels of androstenone and skatole in pig fat

The number of entire male pigs slaughtered in Great Britain has increased steadily over the past 10 years and they now constitute some 45 per cent of the national population. Although there has been concern about possible boar taint, the industry has apparently experienced few problems. However, boar taint continues to be a major concern in other countries, possibly reflecting heavier slaughter weights and breed differences. Limited evidence indicates that earlier maturing breeds, such as the Pietrain and Duroc, tend to have more taint than other breeds of the same weight or age. This has implications for the wider use of specialist meat type sires which now supply atleast 10 per cent of the genes in the commercial British slaughter population.

Response of modern hybrid pigs to dietary energy concentration

In a recent experiment using the same improved genotype, pigs over the liveweight range 25 to 120 kg were found to have modest voluntary energy intakes (Chadd and Cole, 1988) particularly when compared with former intake prediction equations. It follows that the response of such pigs in terms of voluntary feed intake behaviour when provided with diets differing in energy concentration may have also changed. Diets that are formulated to be low in energy density and therefore bulky in nature are likely to represent more of a limitation to voluntary feed intake than previously. Former experiments designed to examine the pig's ability to adjust feed intake in order to maintain a constant energy intake have produced results varying from complete to incomplete compensation.A study was undertaken to examine the response of a modern genotype in terms of voluntary feed intake, digestible energy (DE) intake, growth performance and associated carcass characteristics, when offered a range of dietary energy concentrations ad libitum and taken to a heavy slaughter weight.

Effects of oestradiol-17β or zeranol with or without trenbolone acetate on live-weight gain, carcass composition and zeranol residues in steers on an 18-month beef system

ABSTRACTA comparison of anabolic treatment regimes was made in 761 autumn-born Friesian steers on 14 farms. Prior to turn-out for grazing at 6 months of age and approximately 180 kg live weight, steers were weighed and divided into three equal-weight groups. Group 1 received silastic implants containing 45 mg oestradiol-17β. Group 2 received 36 mg zeranol and group 3 were untreated controls. All steers were weighed at intervals of approximately 3 months (i.e. mid summer, yarding at autumn, mid winter and pre-slaughter) and group 2 steers received a further 36 mg zeranol at the second, third and fourth weighing. At the third weighing half the cattle in each of the treatment groups 1 and 2 received 300 mg trenbolone acetate. Also at the third weighing, group 3 (controls) were subdivided into three equal-weight groups, the first of which received 45 mg oestradiol-17β and 300 mg trenbolone acetate and the second 36 mg zeranol and 300 mg trenbolone acetate. The third subgroup remained as untreated controls.From 10 farms a 25% sample close to group mean weight at mid winter were slaughtered on the same day and subjectively assessed for subcutaneous fat score and conformation on 15-point scales. The left thin flank was separated into tissues. Samples of lean fat, liver and kidney were analysed for zeranol residues. All implant treatments resulted in higher live-weight gain, heavier slaughter weights and earlier slaughter. Trenbolone increased daily gain only during the first 3 months after treatment. Implanted carcasses were heavier both in the fore- and hindquarter but trenbolone also produced heavier forequarters. Carcasses from treated steers had more subcutaneous fat, less perinephric and retroperitoneal fat and less intermuscular fat in the thin-flank joint. Zeranol residues in implanted steers were not significantly higher than controls except in the kidney, but even these were significantly below accepted tolerance levels.