Rabbit commercial maternal lines are usually selected for litter size (LS) and paternal lines for growth rate (GR). Line OR_LS was selected by ovulation rate (OR) and LS to improve LS more efficiently. In this study, growth traits of line OR_LS were evaluated by estimating the correlated response on weaning weight (WW), slaughter weight (SW) and GR during fattening period as well as their variability (DWW, DSW and DGR, respectively). Data were analyzed using Bayesian inference methods. Heritability estimates were low for growth traits (0.09, 0.13 and 0.14 for WW, SW and GR, respectively) and negligible for growth traits variability (0.01, 0.004 and 0.01 for DWW, DSW and DGR, respectively). Moderate common litter effect ratio (c2; 0.35, 0.28 and 0.27) and low maternal effect ratio (m2; 0.11, 0.05 and 0.01) were obtained for WW, SW and GR, respectively. Both c2 and m2 were lower at slaughter than at weaning. In addition, low common litter effect and negligible maternal effect were observed for growth traits variability. Genetic correlations between LS and both growth traits and their variability were close to zero. Positive genetic correlations were observed between OR and growth traits (0.19, 0.38 and 0.36 for WW, SW and GR, respectively) as well as between OR and growth traits variability (0.35, 0.62 and 0.20 for DWW, DSW and DGR, respectively). Positive correlated responses in both periods were obtained for growth traits, WW, SW and GR (0.037, 0.156 and 0.110 kg, respectively). The correlated response found in growth traits might be due to the positive genetic correlations between OR and these traits. However, selection for OR and LS using independent culling levels did not modify the growth traits variability. Therefore, no negative consequences on growth traits can be expected in current commercial maternal lines.

Piétrain (P), Large White (LW) and Belgian Landrace stress negative (BN) boars were slaughtered at 50, 70, 90 or 110 kg live weight to investigate breed differences and the effect of slaughter weight on boar taint prevalence. Boar taint was quantified by four different methodologies: sensory evaluation of neckfat heated with a hot iron in the slaughterhouse, sensory evaluation of meat by consumer panels, sensory evaluation of fat and meat by expert panels and laboratory analysis of indole, skatole and androstenone in backfat. Skatole levels in backfat were significantly higher for LW and BN than for P boars. The androstenone levels and the hot iron method revealed a significant interaction between breed and slaughter weight. On the other hand, experts detected an effect of weight on the androstenone odour perception, which was significantly higher in fat from boars slaughtered at 90 kg compared with 50 kg, and significantly higher in meat from boars slaughtered at 110 kg compared with 50 kg. Consumers did not detect differences in the sensory characteristics among breeds or slaughter weight. These results indicate opportunities to minimise the risk of boar taint in entire male pigs by carefully selecting a combination of breed and slaughter weight. Along with the optimal slaughter weight, the effectiveness of reducing boar taint by lowering slaughter weight appeared to be breed dependent.

A total of 200 (Landrace × Large White dam × Pietrain × Large White sire) gilts of 50 ± 3 days of age (23.3 ± 1.47 kg BW) were used to investigate the effects of castration (intact gilt, IG v. castrated gilt, CG) and slaughter weight (SW; 106 v. 122 kg BW) on productive performance, carcass and meat quality. Four treatments were arranged factorially and five replicates of 10 pigs each per treatment. Half of the gilts were ovariectomized at 58 days of age (8 days after the beginning of the trial at 29.8 ± 1.64 kg BW), whereas the other half remained intact. The pigs were slaughtered at 106 or 122 kg BW. Meat samples were taken at Musculus longissimus thoracis at the level of the last rib and subcutaneous fat samples were taken at the tail insertion. For the entire experimental period, CG had higher (P < 0.05) BW gain and higher (P < 0.001) backfat and Musculus gluteus medius fat thickness than IG. However, IG had higher (P < 0.05) loin and trimmed primal cut yields than CG. Meat quality was similar for IG and CG but the proportion of linoleic acid in subcutaneous fat was higher (P < 0.001) for IG. Pigs slaughtered at 122 kg BW had higher (P < 0.001) feed intake and poorer feed efficiency than pigs slaughtered at 106 kg BW. An increase in SW improved (P < 0.001) carcass yield but decreased (P < 0.05) trimmed primal cut yield. Meat from pigs slaughtered at the heavier BW was redder (a*; P < 0.001) and had more (P < 0.01) intramuscular fat and less thawing (P < 0.05) and cooking (P < 0.10) loss than meat from pigs slaughtered at the lighter BW. In addition, pigs slaughtered at 122 kg BW had less (P < 0.01) linoleic acid content in subcutaneous fat than pigs slaughtered at 106 kg BW. Castration of gilts and slaughtering at heavier BW are useful practices for the production of heavy pigs destined to the dry-cured industry in which a certain amount of fat in the carcass is required. In contrast, when the carcasses are destined to fresh meat production, IG slaughtered at 106 kg BW is a more efficient alternative.

The effect of slaughter weight and breed on the composition of intramuscular fat (IMF) of seven Spanish cattle breeds was studied. Lipid classes and fatty acids were evaluated in young bulls of seven local Spanish cattle breeds, Asturiana, Avileña, Morucha, Parda Alpina, Pirenaica, Retinta and Rubia Gallega, slaughtered at a live weight of 320 kg (veal type) and 550 kg (yearling bull type). Higher slaughter weight and early maturating breeds produced higher IMF content in the longissimus muscle (P < 0.001), which was linked to a reduction in phospholipids, monoglycerides, diglycerides, cholesterol and free-fatty acids content, but an increase in triacylglycerols. Besides, heavier animals displayed a higher percentage of saturated and monounsaturated fatty acids (MUFA), but a lower polyunsaturated fatty acids (PUFA) percentage (P < 0.001). The increase in triglycerides (TG), saturated fatty acids (SFA) and MUFA illustrates the increasing importance of lipid storage as fattening proceeds and the acquisition of ruminal functionality. The feeding system based on cereals had a strong influence on the fatty acid profile, giving the studied beef a relatively high PUFA/SFA and n-6/n-3 ratios.

Hatchling length and weight are used as tools to measure hatchling quality. However, the relationship between these parameters and later performance are not well known. This review evaluates the relationship between hatchling length or weight and slaughter weight, breast meat yield and feed conversion ratio (FCR) in both male and female broilers.

Datasets from two trials were compared. In the first, hatchling length and weight of 100 male and 100 female broilers were measured and body weight and breast meat yield were determined at 38 days of age. In experiment 2, hatchling length of 187 female and 230 male broilers was measured and body weight was determined at 21 and 42 days of age. Feed intake was determined between 21 and 42 days of age.

In both experiments, male broilers showed a positive relationship between hatchling length and slaughter weight or breast meat yield, but no relationship was found with hatchling weight. The relationship between hatchling length and performance in female broilers differed between the two experiments. In female broilers, a negative relationship between hatchling weight and breast meat yield was found. No relationship between hatchling length and FCR in both male and female broilers was found. From this limited dataset, it can be concluded that hatchling length seems to be a better parameter to predict subsequent chick performance, excluding FCR, than hatchling weight, but gender needs to be taken into account.

This work presents an analysis of heterogeneity of environmental variance for slaughter weight (175 days) in pigs. This heterogeneity is associated with systematic and additive genetic effects. The model also postulates the presence of additive genetic effects affecting the mean and environmental variance. The study reveals the presence of genetic variation at the level of the mean and the variance, but an absence of correlation, or a small negative correlation, between both types of additive genetic effects. In addition, we show that both, the additive genetic effects on the mean and those on environmental variance have an important influence upon the future economic performance of selected individuals.

There is a paucity of data on the beef production potential of Norwegian Red (NOR) compared with ‘modern’ Holstein-Friesian (HF) cattle. The present study used a total of 64 bulls in a 2 × 2 factorial design study encompassing two breeds (HF and NOR) and two slaughter ages (485; E, and 610; L, days). The mean initial age and live weight of the HF bulls were 179 (s.d. 47.1) days and 203 (s.d. 64.0) kg, while the corresponding data for the NOR bulls were 176 (s.d. 39.7) days and 185 (s.d. 63.6) kg, respectively. Bulls were offered a 50 : 50 mixture (dry matter (DM) basis) of grass silage and concentrates. No breed × slaughter group interactions were recorded for any parameters evaluated (P > 0.05). HF bulls had higher (P < 0.001) DM intake and poorer (P < 0.01) efficiency of conversion of food to carcass gain than NOR bulls. HF bulls tended (P = 0.07) to have a higher rate of live-weight gain and were heavier (P < 0.001) at slaughter than NOR bulls, though both carcass weight and rate of carcass gain did not differ between the breeds (P > 0.05). NOR bulls had higher (P < 0.001) dressing proportion and carcass conformation score than HF bulls, while breed of bull had no influence (P > 0.05) on carcass fat classification, depth of subcutaneous fat, marbling score or on the weight of fat in the internal depots. Daily food intakes did not differ (P > 0.05) across the two slaughter age groups, though efficiency of conversion of food to carcass gain was poorer (P < 0.05) in the L compared with E bulls. Rate of live-weight gain was lower (P < 0.01) for L bulls, although rate of carcass gain did not differ (P > 0.05) between the E and L bulls. Increasing age at slaughter increased (P < 0.01 or greater) dressing proportion, carcass fat class, depth of subcutaneous fat, marbling score and internal fat depots, but had no effect (P > 0.05) on the carcass conformation score. Instrumental measures of meat quality indicated that meat from NOR bulls was tougher (P < 0.01) than meat from HF bulls, while delaying slaughter increased (P < 0.001) a* and C*ab, and decreased (P < 0.01) h0, indicating improved redness. It is concluded that NOR bulls have higher food efficiency and produce more highly conformed carcasses than HF bulls, but HF bulls produce more tender meat.

A total of 180 Holstein-Friesian male calves, mean age and live weight (LW) at start of the study 112 (s.d. 26·0) days and 134 (s.d. 37·6) kg, respectively, were used to evaluate the effect of slaughter weight on food efficiency and animal performance. Animals were offered concentrates ad libitum and a restricted quantity of straw and slaughtered at one of six LWs as bulls: 300, 350, 400, 450, 500 or 550 kg. A further group of cattle were slaughtered as steers at 450 kg LW. Mean age at slaughter was 247 and 434 days for bulls slaughtered at 300 and 550 kg LW respectively. Neither rate of LW or carcass gain was influenced by weight at slaughter ( P>0·05), with mean values of 1·31 and 0·70 kg/day, respectively. Food conversion ratio, killing-out proportion, carcass conformation, fat classification and weight of internal fat depots increased ( P<0·001) as slaughter weight of the bulls increased. In the comparison of steers and bulls slaughtered at 450 kg, steers had lower ( P<0·001) rates of LW and carcass gains and had a higher ( P<0·001) food conversion ratio than comparable bulls. Steers had lower ( P<0·001) estimated carcass lean, and higher ( P<0·01) estimated carcass fat concentrations than bulls slaughtered at the same LW.

Castrated 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.

Three weaning treatments (weaning at 45 days of age, at 65 days of age, unweaned) and two slaughter weights (24 and 28 kg) were compared in lambs raised at pasture, and their effect on carcass and meat traits were studied. Unweaned lambs displayed a greater growth rate, lower concentrate consumption, greater dorsal fat thickness, more kidney knob and channel fat and greater total fat levels, measured through dissection of the hind limb. Total collagen concentration was lower in unweaned lambs and the intramuscular fat of these same animals exhibited a greater proportion of saturated fatty acids and a lower n-6/n-3 fatty acid ratio. Slaughter weight influenced scored carcass fatness, which was greater in heavier lambs, meat colour, which displayed greater lightness in lower-weight lambs, and water-holding capacity, which was lower in lambs with the lower slaughter weight. The heavier lambs displayed lower soluble collagen values, and the intramuscular fat of the longissimus dorsi muscle of these same lambs contained higher levels of monounsaturated and lower levels of polyunsaturated fatty acids.

Forty-five Talaverana breed sucking lambs of both sexes were slaughtered at 10 and 12 kg live weight in order to study the effect of gender and slaughter weight on carcass, meat and fat traits. Carcass dressing proportions and fatness (by various measures) were higher in females and heavier lambs, which also showed better conformation. Lightness (L*) of the carcass fat was higher in males and heavier lambs. Females and heavier lambs also displayed a greater proportion of fat on dissection, primarily due to a higher percentage of subcutaneous fat tissue. Water-holding capacity was greater in males and in lower-weight lambs. Males presented higher total collagen and lower soluble collagen values than females. In general, a high percentage of short-chain (C12:0 and C14:0) fatty acids, as well as of palmitic acid (C16:0), was observed in the intramuscular fat of the longissimus dorsi muscle, corresponding with an exclusively milk diet.

This study investigated the effects of the percentage of Texel or Rouge de l’Ouest (Rouge) genes in lambs (0, 50, 75 or 100%; the remainder being Greyface (Border Leicester × Scottish Blackface)) on lamb carcass characteristics and meat quality. Ewe lambs were slaughtered at 34, 40, 46 and 52 kg and ram lambs were slaughtered at 40, 46, 52 and 58 kg live weight. Dressing proportion increased (P < 0·001) by 0·53 and 0·27 g carcass weight per kg live weight for each 1% increase in Texel or Rouge genes respectively. Carcass conformation classification increased (P < 0·001) by 0·016 and 0·007 units (on a five-point scale) for each 1% increase in Texel or Rouge genes respectively. Carcass fat depth measures were reduced by Texel and Rouge genes such that at a constant fat depth end point, carcass weight could be increased by 0·029 and 0·023 kg for each 1% increase in Texel or Rouge genes. Carcass lean content increased (P < 0·001) by 0·99 and 0·27 g/kg for each 1% increase in Texel or Rouge genes. Subcutaneous fat content was reduced (P < 0·001) by 0·36 and 0·29 g/kg for each 1% increase in Texel or Rouge genes. Intermuscular fat content was reduced (P < 0·01) by 0·38 g/kg per 1% increase in Texel genes, whereas Rouge genes had no effect. Similarly, bone content was reduced (P < 0·01) by Texel genes only (0·31 g/kg per 1% increase in Texel genes). Warner-Bratzler shear force values showed a quadratic effect with increasing Texel and Rouge genes, with an initial decrease from 0 to 50% followed by an increase to 100%. Cooking loss increased (P = 0·05) as the percentage of Rouge genes in lambs increased. Increasing the percentage of Texel or Rouge genes significantly increased L* values (P < 0·01 and P < 0·05 respectively), b* values (P = 0·05 and P< 0·05 respectively) and H° values (P < 0·001).

Carcass and meat quality traits were studied in 94 barrows of known HAL-1843 genotype (homozygote - - and heterozygote - +) from three crosses slaughtered at 90 kg and 120 kg live weight. Crosses A and B were produced from sires of which 0·5 of the genes were from a heavy-muscled × Large White line and 0·5 from pure Pietrain (A) or Duroc (B). Sows for both A and B were from a hyperprolific Large White × Landrace line and this latter line produced the pigs for cross C (control). The carcasses from cross A which were sired from boars having 0·75 of their genotype from heavy-muscled genetic lines had higher killing-out proportion, better conformation scores, greater loin depth and loin area, less carcass length and bone content, and greater lean proportion compared with cross C. The carcasses from cross B, with roughly 0·25 of Duroc genes had a significantly higher backfat thickness than either cross A or C. However their composition was not significantly different from C, since the higher backfat was counter-balanced by their better conformation. Carcass and lean weight distribution was more favourable in crosses A and B, which had significantly higher economic yields than cross C. The halothane genotype did not have a significant effect on fatness and carcass composition, although the heterozygote showed a significantly greater muscle depth. In addition, no significant effect of the halothane gene on carcass and lean weight distribution was observed. In relation to the light group of carcasses (72·8 (s.e. 4·4) kg), the heavy group (100·1 (s.e. 2·7) kg) had greater killing-out proportion, better conformation, longer carcasses, higher fatness and greater loin depth and area. These genetic lines showed a 9·6 g/kg increase in fat and a 6·1 g/kg decrease in lean for every 10 kg of increasing slaughter weight. With the slaughter weight increase the longissimus dorsi muscle became less pale due to a higher muscle pigment concentration, and the backfat had a higher proportion of oleic and lower proportion of linoleic and palmitic fatty acids. The halothane genotype had a significant effect on meat quality. The heterozygote produced much paler, softer and more exudative meat. However, the effect of cross and carcass weight was not significant for meat quality measurements determining pale, soft and exudative meat.

A total of 897 pigs were used in a study to investigate the relative effects of terminal sire genotype (lines Av.Bv. C), sex (castrate v. gilt), slaughter weight (80 v. 100 v. 220 kg), feeding regimen (ad libitum v. restricted, 0·82 ad libitum intake) and slaughter-house (HI v. H2 v. H3) on growth performance, carcass and meat quality characteristics and the eating quality offresh pig meat. Sire line A was a pure Duroc population, and B and C were European-type experimental lines where C contained Pietrain and B did not. In total, 26 sires from line A, 42 sires from line B, and 21 sires from line C were mated to females from the same crossbred dam line and progeny were reared under standard conditions to slaughter. Following slaughter and carcass evaluation, samples of longissimus dorsi were investigated for a range of meat quality and organoleptic characteristics. Line A produced fatter carcasses (C fat depths = 15·6 v. 24·0 v. 14·0 mm for lines A, B, and C, respectively, average s.e. 0·39) with higher killing-out proportions (g/kg) (790 v. 779 v. 786 respectively, average s.e. 1·4) and higher visible marbling, less tissue separation, firmer backfat, and juicier (3·81 v. 3·67 v. 3·72 respectively, average s.e. 0·044: on a scale 1 (extremely dry) to 8 (extremely juicy)) and more acceptable meat (4·54 v. 4·37 v. 4·42 respectively average s.e. 0·037: on a scale 1 (dislike extremely) to 8 (like extremely)) with a lower shear force (5·35 v. 5·78 v. 5·67 kg respectively, average s.e. 0·078) than lines B and C which were similar in most respects. Increases in slaughter weight were associated with a reduction in growth rate (785 v. 769 v. 725 glday for 80, 100 and 120 kg slaughter weight respectively, average s.e. 8·5), increases in backfat (Cfat = 13·3 v. 24·2 v. 26·3 mm respectively, average s.e. 0·34) and longissimus muscle area (34·6 v. 40·7 v. 44·6 cm2 respectively, average s.e. 0·59) and a deterioration in tenderness (4·72 v. 4·40 v. 3·95 respectively, average s.e. 0·062: on a scale 1 (extremely tough) to 8 (extremely tender) and overall acceptability (4·65 v. 4·44 v. 4·25 respectively, average s.e. 0·045) and an increase in shear force (5·37 v. 5·58 v. 5·87 kg respectively, average s.e. 0·085). Slaughter-house had a significant impact on pork odour scores but not on other organoleptic properties. Pigs reared under ad libitum feeding grew faster (840 v. 678 g/day respectively, average s.e. 3·7), were fatter (Cfat = 15·8 v. 23·2 mm respectively, s.e. 0·28), had lower carcass yields (780 v. 790 g/kg respectively, average s.e. 1) and produced more tender, juicier meat than those reared under restricted feeding. Differences between castrated males and gilts in growth and carcass trait were in line with other studies and there were no significant differences between the sexes for eating quality. There were relatively few significant interactions (P < 0·05) for eating quality traits and most of these involved slaughter-house and were for pork odour intensity, which are of limited practical significance. This suggests that the effects of sire genotype, slaughter weight and feeding regimen on eating quality identified in this study are likely to be additive.

Bulls (½ Blonde d'Aquitaine ⅜ Charolais) were used in a 2 × 3 factorial design experiment with two planes of nutrition in the finishing period and three slaughter weights. High and low planes of nutrition were based on diets with similar forage to concentrate ratio (0·40 of dry matter (DM)) offered ad libitum or at 0·78 of ad libitum DM intake at equal live weight respectively. The target slaughter live weights were 550, 625 and 700 kg. Twelve bulls were taken to each slaughter point and an additional five animals were killed as a pre-experimental slaughter group. Mean initial live weight was 412 (s.e. 5·3) kg at a mean age of 342 (s.e. 2·5) days. No significant interactions were found between the main factors. For the high and low planes, live-weight and estimated carcass gains were 1251 and 989 (s.e. 47·7), and 816 and 668 (s.e. 35·3) g/day respectively, the reduction in gains being similar to the proportional degree of nutritional restriction. Plane of nutrition had no effect on live-weight or carcass gain per unit of energy intake. The low plane of nutrition produced significant decreases in body cavity fat depots, subcutaneous fat in the sample joint and increased the proportions of both saleable beef and high-priced joints in the carcass.

With increase in slaughter weight, energy intake per unit of live weight0·75 and rates of both live-weight and carcass gain tended to decline. The dressing proportions were 583,579 and 609 (s.e. 9·1) g/kg for the slaughter live weights of 550, 625 and 700 kg. Carcass conformation improved while fat depots in the body cavity and estimated concentration of separable fat in the carcass increased with increase in slaughter weight, and both estimated lean and bone concentrations decreased. Forequarter as a proportion of total side tended to increase with increase in slaughter weight. Slaughter weight had no effect on concentration of saleable meat or ultimate pH of carcass muscle. It is concluded that bulls of this genotype can be taken to high slaughter weights on diets having a relatively high proportion of forage as grass silage, with high rates of growth and acceptable carcass leanness.