Carcass and meat quality of Bos indicus x Bos taurus and Bos taurus cattle in northern Australia

1989 ◽  
Vol 29 (6) ◽  
pp. 757 ◽  
Author(s):  
JR Wythes ◽  
WR Shorthose ◽  
RM Dodt ◽  
RF Dickinson
Keyword(s):  
Bos Taurus ◽  
Bos Indicus ◽  
Carcass Characteristics ◽  
Liver Weight ◽  
Carcass Weight ◽  
Northern Australia ◽  
Muscle Properties ◽  
Significant Difference ◽  
Access To Water ◽  
Dressing Percentage

Liveweights, carcass characteristics, bruising and muscle properties of Bos indicus x Bos taurus (BiX) and Bos taurus (Bt) cattle (1070 steers and 394 cows) were compared from 7 experiments throughout Queensland. In general, the cattle were weighed (unfasted), transported as mixed genotype groups to an abattoir and given access to water from arrival until slaughter. Access to feed varied between experiments. Mustering to slaughter periods varied from 4 to 9 days. For steers, mean liveweight at slaughter and carcass characteristics (weight, dressing percentage, liver weight and rib fat depth) were generally similar for BiX and Bt. In 1 of the 5 experiments with steers, BiX had a greater (P<0.05) mean liveweight, carcass weight, dressing percentage and liver weight. In both of the experiments with cows, BiX had greater (P<0.05) mean carcass weight but in only 1 experiment greater (P<0.05) mean liveweight and dressing percentage. There were no consistent differences between BiX and Bt in bruise score. Meat properties were compared in 1 experiment each for steers and for cows. BiX cows had a greater (P<0.05) mean initial yield(YI) shear value and tended to have a greater peak force (PF) for M. longissimus dorsi (LD) muscle than Bt cows. BiX had a lower (P<0.05) PF - IY value. Genotype had no significant effect on shear values and sarcomere length in steers or on cooking loss in steers and cows. Over all experiments, there was a higher (P<0.05) percentage of Bt than BiX carcasses ( 8.5 v. 3.7%) with high pH (> 6.0) values 24 h post mortem (pH24) for LD muscle. Genotype had no significant effect on mean pH24 and ultimate pH in cows or steers. Significantly more (P<0.05) cow than steer carcasses had high pHz4 values (10.9 v. 5.0%). In 2 experiments, more (P<0.05) heads and tongues were condemned for BiX than Bt steers, but there was no significant difference for the percentage of burst rumens. We conclude that the belief held by producers, butchers and others that BiX cattle have more bruising and produce darker meat than Bt cattle is unfounded. The overall toughness of meat from cattle slaughtered in northern Australia is of much greater concern than minor differences between genotypes.

Chronological age and dentition effects on carcass and meat quality of cattle in northern Australia

1991 ◽  
Vol 31 (2) ◽  
pp. 145 ◽  
Author(s):  
JR Wythes ◽  
WR Shorthose
Keyword(s):  
Shear Force ◽  
Carcass Weight ◽  
Chronological Age ◽  
Longissimus Dorsi ◽  
Northern Australia ◽  
Muscle Properties ◽  
Yield Value ◽  
Access To Water ◽  
Dressing Percentage

The effects of chronological age and dentition on the liveweight, carcass weight, bruising and muscle properties of 348 cows and 370 steers were examined in 5 experiments in Queensland (1982-83). Birth dates were known only for the cows in experiments 1 and 2, and for the steers in experiment 5; with ages categorised as 4 years and less (young), 5-10 years (mature) and greater than 10 years (old). The number of permanent 'incisor' teeth were recorded for all animals. The cattle were weighed (unfasted), transported to an abattoir and given access to water and hay (except in experiment 5). Mustering to slaughter periods varied from 2 to 7 days. Half the carcasses were electrically stimulated in experiments 1 and 2. In general, old and mature cows with 8 teeth had heavier (P<0.05) mean liveweights than did young cows with 4 teeth, and both had heavier (P<0.05) liveweights and carcass weights than those with 2 teeth. Old cows with 8 teeth also had the lowest (P<0.05) mean dressing percentage, while mature cows had the greatest (P<0.05) fat depth. There was no consistent trend between groups in bruise score. Steers with 8 teeth had a greater (P<0.05) mean liveweight, carcass weight, dressing percentage and rib fat depth than other dentition groups, and a greater (P<0.05) bruise score in experiment 5 only. There was no significant effect of chronological age or dentition on the shear force values or cooking losses of M. longissimus dorsi (LD) for cows. In 1 experiment, steers with 8 teeth had a greater (P<0.05) peak force-initial yield value and lower (P<0.05) cooking loss than other dentition groups. Mature cow carcasses cooled more (P<0.05) slowly than those of other ages. Over all experiments, there were more (P<0.05) high pHz4 carcasses among the combined 6 and 8 teeth group than the combined 2 and 4 teeth group (10.2 v. 2.3%).

Effect of method of sale and various water regimens at saleyards on the liveweight, carcass traits and muscle properties of cattle

1983 ◽  
Vol 23 (122) ◽  
pp. 235 ◽  
Author(s):  
JR Wythes ◽  
MJ Brown ◽  
WR Shorthose ◽  
MR Clarke
Keyword(s):  
Water Content ◽  
Carcass Traits ◽  
The Other ◽  
Carcass Weight ◽  
Muscle Properties ◽  
Muscle Water Content ◽  
Access To Water ◽  
Muscle Water ◽  
Dressing Percentage ◽  
Water Contents

In two experiments, we examined the effects on liveweight, carcass traits and muscle properties of (a) sending cattle to the abattoir either direct from a farm or via a saleyard, and (b) different curfew and sale procedures at a saleyard. During the 12 h curfew and 10 h sale periods, cattle were held with or without water, but always denied feed. In experiment 1, after a journey of 1320 km, 252 bullocks (mean liveweight 558 kg) were subjected to one of seven treatments. The groups transported direct to the abattoir were (1) denied water between arrival and slaughter (26 h), (2) offered water for 26 h, or (3) offered water and feed for 50 h and then water alone for 24 h. Those sent to the saleyard were given access to water (4) at all times, (5) only during the curfew and sale periods, (6) only before the curfew began, or (7) were denied water until after the sale, when all groups were offered water for 36 h until slaughter. Among the bullocks sent direct to the abattoir, the group with water for 26 h until slaughter had heavier (P< 0.0 1 ) carcasses than those denied water (331 kg vs 312 kg) and also a greater (P < 0.0 1) muscle water content, while the carcasses of the group slaughtered 2 d later were intermediate for both. Whether dressing percentages were calculated on liveweights at the start or end of the simulated sale for the four saleyard groups, the differences in mean dressing percentages between groups offered water (0.7 and 0.3 percentage units) were less than the differences between the means of the groups denied water (3.7 and 3.5 units). The increases in dressing percentage during the sale for groups with water (0.7 and 0.3 units) were less than those for the groups denied water (1.5 and 1.7 units). Differences in mean liveweights and mean muscle water contents between groups followed the same trends. Mean carcass weights did not differ significantly between saleyard groups (318-323 kg). In experiment 2, after a journey of 90 km, 152 cows (mean liveweight 323 kg) were subjected to one of four treatments. The group going direct to the abattoir was offered water for 4.5 h, fasted for 16 h and then slaughtered. For the other three groups, the saleyard treatments 4,6, or 7 of experiment 1were imposed, followed by 21 h on water and a 16 h pre-slaughter fast. Trends in dressing percentage and liveweight were similar to those recorded in experiment 1. Mean carcass weight varied (P<0. 05) between groups and tended to increase with muscle water content. Method of sale was important because it affected the time from mustering to slaughter, and thus, carcass weight. At saleyards, the practice of giving cattle continuous access to water reduced significantly the variation in liveweight, dressing percentage and muscle water content between groups with similar initial liveweights. This practice at abattoirs avoided dehydration of carcass tissues at slaughter

A COMPARISON OF FEEDLOT PERFORMANCE AND CARCASS CHARACTERISTICS OF CHARBRAY × HEREFORD WITH HEREFORD STEERS

1959 ◽  
Vol 39 (1) ◽  
pp. 14-20 ◽  
Author(s):  
M. A. MacDonald ◽  
S. B. Slen ◽  
H. J. Hargrave
Keyword(s):  
Muscle Fibre ◽  
Carcass Characteristics ◽  
Carcass Weight ◽  
Longissimus Dorsi ◽  
Average Thickness ◽  
Feedlot Performance ◽  
Commercial Feed ◽  
Significant Difference ◽  
Dressing Percentage

Bulls of Charbray breeding and Hereford bulls were turned out with a commercial herd of Hereford cows in southwestern Saskatchewan in 1956. It was assumed the cows were bred at random. At weaning in 1957, 25 Charbray × Hereford (crossbred) steers and 25 Hereford steers were selected at random, weighed and removed to a commercial feed lot where they were fed in two groups to a desirable slaughter finish.Crossbred steers were heavier at weaning, gained more per day on feed and returned a higher hot carcass weight with a greater eye of lean area than Hereford steers. There was no significant difference between groups in dressing percentage, average thickness of rib fat, TDN consumption per pound of liveweight gain, or average muscle fibre diameters of samples taken from m. longissimus dorsi. The Hereford group produced a higher proportion of choice carcasses than the Charbray × Hereford group.

scholarly journals The Effect of Dried Blood Rumen Content Mixture (D BRCM) on Carcass Characteristics of SASSO C44 Broiler Chicks

2016 ◽  
Vol 12 (12) ◽  
pp. 166
Author(s):  
Melkamu Bezabih Yitbarek ◽  
Berhan Tamir ◽  
Ashenafi Mengistu
Keyword(s):  
Soybean Meal ◽  
Carcass Characteristics ◽  
Abdominal Fat ◽  
Carcass Weight ◽  
Broiler Chicks ◽  
Fat Percentage ◽  
Carcass Yield ◽  
Treatment Groups ◽  
Significant Difference ◽  
Dressing Percentage

The experiment was conducted to evaluate the effect of dried bloodrumen content mixture (DBRCM) on carcass characteristics of broiler chicks to replace soybean meal (SBM). A total of 225 unsexed day old broiler chicks (SASSO C44) were randomly distributed to five dietary treatment groups in a completely randomized design. Each treatment was replicated thrice with 15 birds per replicate. The experimental diets were formulated to contain 100%SBM+0%DBRCM (T1), 80%SBM+20% DBRCM (T2),60%SBM+ 40% DBRCM (T3), 40%SBM+60% DBRCM(T4) and 20%SBM+80% DBRCM (T5) in 56 days of age. At the end of the experiment, two male and two female birds per replicate were used to determine carcass characteristics. The result revealed that the edible carcass yield ranged from 977.9-1159.3g. The dressing percentage based on the edible carcass weight was 63.9 % (T1), 66.6 % (T2), 65.4 (T3), 64.2% (T4) and 63.1% (T5). There was no a significant difference (P>0.05) in both edible carcass yield and its dressing percentage. The commercial carcass weight was 937.4g (T1), 984.7g (T2), 962.0g (T3), 925.0g (T4) and 833.1g (T5) and the dressing percentage was 54.9%, 56.6%, 55.3%, 53.7% and 53.7% for T1, T2, T3, T4 and T5, respectively. Significant difference (P>0.05) was not observed in commercial carcass yield and its dressing percentage among the treatment groups. There was no a statistical marked difference (P>0.05) in total nonedible offal and edible offal. Females had more (P<0.05) breast meat than that of males. The abdominal fat and abdominal fat percentage were not significantly influenced (P>0.05) by a diet containing DBRCM. However, abdominal fat and its fat percentage were higher (P<0.05) in females than males. Based on this result, it could be concluded that DBRCM can replace soybean meal up to 80% substitution level without any adverse effect on carcass characteristics.

scholarly journals QUANTITATIVE AND QUALITATIVE BUFFALO (Bubalus bubalis L.) CARCASS CHARACTERISTICS FED WITH A DIFFERENT RELATIONSHIP OF ROUGHAGE AND CONCENTRATE ON A FEEDLOT SYSTEM IN BRAZIL

2006 ◽  
Vol 4 (3) ◽  
pp. 33 ◽  
Author(s):  
Marcos Elias Traad da Silva ◽  
José Sidney Flemming ◽  
José Lino Martinez ◽  
Nina Waszczynskyj ◽  
Carlos Ricardo Soccol
Keyword(s):  
Block Design ◽  
Energy Levels ◽  
Carcass Characteristics ◽  
Bubalus Bubalis ◽  
Carcass Weight ◽  
Leg Length ◽  
Muscle Area ◽  
Significant Difference ◽  
Quantitative Characteristics ◽  
Dressing Percentage

Eighteen non castrated Murrah male buffaloes, averaging 403 kg in weight, have been used in a feed lot randomized complete-block design, to test three different diets (T) with different combination of roughage (R) and concentrate (C). Tukey test has been used (5% of significance) to evaluate the obtained averages. The trial was carried on at AGRONOMIC INSTITUTE OF PARANÁ (Pinhais town, Paraná, Brazil), during 91 days. The animals have been fed twice daily, and the diets contained (%): T1 =75 R : 25 C; T2 =65 R : 35 C and T3 =55 R : 45 C, and it was calculated to have the same level of protein and energy in its composition, aiming to evaluate the diets effects on the animals’ performance on body weight and carcass characteristics. The R utilised was corn silage plus 0.5% of urea. The C was composed by soybean, wheat meal, corn, cottonseed, plus mineral, presenting: T1 =32.78 and 71.08; T2 =24.17 and 66.50; T3 =20.23 and 63.84, in percentage of crude protein and total digestive nutrients, respectively. The following quantitative characteristics have been evaluated: Hot Carcass Weight (HCW); Cold Carcass Weight (CCW); Hot Carcass Dressing Percentage (HCP); Cold Carcass Dressing Percentage (CCP); Loss After Cooling (LC); Carcass Length (CL); Leg Length (LL); Thigh Thickness (TT); Longissimus dorsi muscle area between 12th and 13th ribs (LA); Loin Area per 100kg of Cold Carcass (LA/100kg CC); Loin Fat Thickness Under the Skin, measured between the 12th and 13th ribs (LF); Bones Percentage (BP), Muscle (MP) and Fat (FP) of the Carcass - data, relative to 9th, 10th and 11th ribs. The evaluated qualitative characteristics were: Carcass Conformation (CONF); Meat Marbling (MM); Meat Texture (MT); Meat Color (MC). The diets have not affected (P > 0.05) the main carcass characteristics: HCW(kg)=265.83; 267.67 and 268.67; CCW(kg)=257.97; 260.92 and 259.27; HCP(%)=50.28; 51.20 and 51.05; CCP(%)=48.80; 48.81 and 49.45; LC(%)=2.96; 2.91 and 3.13; CL(cm)=133.75; 133.50 and 135.83; LL(cm)=70.66; 71.33 and 72.40; TT(cm)=26.16; 26.25 and 26.25; LA(cm2 )=65.48; 67.83 and 62.76; LA/100kg CC(cm2 )=25.37; 26.16 and 24.20; LF(mm)=7.58; 8.42 and 6.88, respectively for T1 , T2 , and T3 . Higher values (P < 0.05) of BP (%) have been observed in T3 (17.32) when compared with T1 (16.06). However, T2 (16.38) had a non-significant difference (P > 0.05). The MP (%) and FP (%) were similar (P > 0.05) for the three diets, and the values were: T1 =56.47 and 27.85; T2 =61.07 and 22.73; T3 =59.00 and 23.50, respectively. The diets have not affected (P > 0.05) the qualitative carcass characteristics, and the marbling observed has been classified as soft. It has been concluded that the use of different relations of roughage and concentrate for non-castrated male buffaloes, submitted to a confined system, on diets of the same protein and energy levels, at the trial conditions, have not influenced the productive performance of the animals, neither the carcass qualitative and quantitative characteristics.

Cattle handling at abattoirs. 3. The effects of feeding, and of different feeds, during the resting period before slaughter on liveweight carcasses and muscle properties

1989 ◽  
Vol 40 (5) ◽  
pp. 1099 ◽  
Author(s):  
JR Wythes ◽  
PJ Round ◽  
GN Johnston ◽  
PC Smith
Keyword(s):  
Rice Straw ◽  
Ph Value ◽  
Liver Weight ◽  
Carcass Weight ◽  
Muscle Properties ◽  
Access To Water ◽  
Ad Libitum ◽  
Native Pastures ◽  
Brahman Steers ◽  
Resting Period

The effects of feeding lucerne hay or rice straw during the resting period before slaughter on live, carcass and liver weights, bruising, the percentages of condemned head and tongues and of rumens with ingesta spillage, and muscle properties of cattle were examined. The 217 British breed and 70 Brahman steers (mean liveweights of 582 and 603 kg) had been grazing native pastures in northern Queensland. They were transported 440 km by road to an abattoir.The seven groups (each 41 steers) had access to water from unloading at the abattoir (late day 2) until slaughter. Three groups (N2, N4 and N6) were not fed, while two groups were fed ad libitum rice straw (RS4 and RS6) and another two groups were fed ad libitum lucerne hay (LH4 and LH6) from day 3 until 24 h before slaughter. The period from mustering to slaughter was 2 days for group N2,4 days for groups N4, RS4 and LH4, and 6 days for N6, RS6 and LH6.Unfed steers lost 4.7% of their pre-transport liveweight after 3 days and 9.1% after 5 days, while the fed steers lost 34% and 6.7%, respectively.Group N2 had a heavier (P<O.05) mean carcass weight than groups N4, RS4, RS6 and LH6 (351 kg compared with 343-344 kg). Both N2 and LH4 (348 kg) were heavier (P< 0.05) than group N6 (340 kg). Trends in mean dressing percentage were the same as for carcass weight. Group N2 had a heavier (P< 0.05) mean liver weight than all other groups, with no effect of feeding treatment. Group N2 and the fed groups (except RS6) had a greater (P< 0.05) mean water content for the M. longus colli than groups N4 and N6.Treatment had no significant effect on mean bruise score, fat thickness, mean pH value of M. longissirnus dorsi 24 h post mortem, the percentage of carcasses with high (>6.00) pH values, and the percentages of heads and tongue condemned due to ingesta contamination and rumens contaminated with ingesta spillage.

The effects of genotype, age, pregnancy, lactation and rumen characteristics on voluntary intake of roughage diets by cattle

1986 ◽  
Vol 37 (5) ◽  
pp. 549 ◽  
Author(s):  
RA Hunter ◽  
BD Siebert
Keyword(s):  
Bos Taurus ◽  
Bos Indicus ◽  
Late Pregnancy ◽  
Poor Quality ◽  
Heteropogon Contortus ◽  
Lactating Cows ◽  
Significant Difference ◽  
Pregnancy And Lactation ◽  
Rate Of Decline ◽  
Brahman Steers

The effects of genotype, age and liveweight, pregnancy and lactation on the voluntary feed intake by cattle of roughage diets of different qualities were studied in a number of experiments. The diets ranged from poor quality (low-nitrogen, high-fibre) spear grass (Heteropogon contortus) hay on which intakes were low ( 1 1 g DM/kg liveweight (LW)) to good quality lucerne (Medicago sativa) hay (26 g DM/kg LW). On the poorest-quality diet, differences in intake between Bos taurus and Bos indicus were not significant. However, on the higher quality diets Herefords (Bos taurus) ate significantly (P < 0.05) more than Brahmans (Bos indicus). In addition, as the quality of the diet improved from speargrass through to lucerne, the breed difference in favour of the Herefords became progressively greater and the variability between animals progressively smaller as a proportion of intake. Another study showed that with increasing age and liveweight of steers, intake per unit body weight declined, the rate of decline being significantly (P < 0.05) greater on good-quality lucerne compared to a poor-quality speargrass diet. There was no significant difference between Aberdeen Angus (Bos taurus) and Brahman steers in the rate of decline of intake of each diet with increasing age and liveweight of the steers. Another experiment which measured intake of pregnant and lactating heifers showed that the amount of feed eaten by pregnant heifers increased with increasing liveweight in late pregnancy, with intake per unit liveweight remaining constant. Lactating cows ate 35% more on a liveweight basis than their nonpregnant, non-lactating counterparts. These results are discussed in relation to mechanisms which control intake of roughage diets in ruminants, especially those associated with energy metabolism.

Effects of sodium chloride and betaine on hydration status of lambs at slaughter

2008 ◽  
Vol 48 (9) ◽  
pp. 1194 ◽  
Author(s):  
K. L. Pearce ◽  
D. G. Masters ◽  
R. H. Jacob ◽  
D. L. Hopkins ◽  
D. W. Pethick
Keyword(s):  
Sodium Chloride ◽  
Carcass Characteristics ◽  
Carcass Weight ◽  
Urine Specific Gravity ◽  
Hydration Status ◽  
Chloride Salt ◽  
Feeding Period ◽  
High Salt Diet ◽  
Access To Water ◽  
The Difference

Under commercial conditions in Australia, lambs are often dehydrated at slaughter despite access to water at the abattoir. Dehydration results in reduced fluid content of meat, which causes liveweight and carcass weight loss. Two experiments evaluated hydration status and carcass characteristics in lambs fed increased levels of sodium chloride (salt) and/or betaine before slaughter. Both experiments were 2 × 2 factorial designs with two levels of salt added [0 and 50 g/kg dry matter (DM)] and two levels of betaine added (0 and 6.7 g/kg DM) to the diets. The treatment diets were introduced to sheep over a 7–8-day period and then fed at 1.5 kg/day for the following 7 days. In experiment 1, 96 Poll Dorset–Merino cross wether lambs (45.9 ± 0.17 kg) were fed in individual pens and in experiment 2, 204 Merino wether lambs (43.1 ± 0.35 kg) were fed in group pens. In the first experiment, water and feed were withheld from the end of the treatment feeding period until slaughter 48 h later. In the second experiment, feed and water were withheld for the first 24 h after treatment but water was available for the next 24 h immediately before slaughter. In both experiments, consumption of the high salt diet decreased urine specific gravity and osmolarity at the end of the feeding period and after 24 h without access to water. This indicates an improved hydration status at this time. However, the difference in hydration status related to feeding salt declined during the 48-h lairage period and there were no significant differences in hot carcass weight or muscle DM among groups at slaughter. It could be concluded from this result that the addition of salt has little commercial value; however, this may not be the case. The lambs in experiment 2 did not behave according to industry expectations. They all drank water in the last 24 h in lairage and none of the groups showed severe dehydration. Further research is justified to determine if the lambs fed the diets with no added salt drunk in lairage as a learned response from the lambs fed salt and, if so, whether this can be developed into a commercial strategy. Feeding betaine did not result in any changes in hydration status or carcass characteristics.

Growth and carcass characteristics of ram, cryptorchid and wether Border Leicester x Merino lambs: effects of increasing carcass weight.

1986 ◽  
Vol 26 (2) ◽  
pp. 153 ◽  
Author(s):  
GJ Lee
Keyword(s):  
Growth Rate ◽  
Carcass Characteristics ◽  
The Other ◽  
Carcass Weight ◽  
Consumer Acceptability ◽  
Cross Border ◽  
Ad Libitum ◽  
Dressing Percentage ◽  
Fat Score ◽  
Score Distributions

The growth and carcass characteristics of first-cross Border Leicester x Merino ram, cryptorchid and wether lambs were compared over a range of slaughter weights (35-55 kg). Lambs were offered feed ad libitum after weaning. The growth rate of wether lambs (221 g/day) was less (P< 0.01) than that of rams and cryptorchids (308 and 280 g/day respectively, P = 0.076). The dressed carcasses of the wether lambs were approximately 2 percentage units heavier than those of the ram and cryptorchids, but this difference was partly due to the weight of the testes. Across all sex groups, dressing percentage increased by 0.46 percentage units per kg increase in carcass weight. The carcasses of rams and cryptorchid lambs tended to be leaner than those of wethers. Fat score distributions, based on export standards, were such that wethers scored higher (fatter) than rams and cryptorchids (P< 0.05). There was a significant sexx carcass weight interaction with GR tissue depths. Above 17 kg carcass weight, tissue depth of wether lambs was greater than those of the other sex types. Of 12 families assessing consumer acceptability (taste, smell, size, fatness and tenderness) of leg roasts, the majority showed no preference for any of the sexes.

Genetic parameters for tropical beef cattle in northern Australia: a review

1993 ◽  
Vol 44 (2) ◽  
pp. 179 ◽  
Author(s):  
GP Davis
Keyword(s):  
Genetic Parameters ◽  
Production Systems ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Genetic Correlations ◽  
Environmental Stresses ◽  
Northern Australia ◽  
Weighted Mean ◽  
Weaning Weight ◽  
Reproduction Traits

This paper reviews published estimates of genetic parameters for traits of growth, reproduction and resistance to environmental stresses for Bos indicus and Zebu derived breeds in northern Australia. Most published estimates of heritabilities for growth and reproduction traits were higher for tropically adapted breeds in northern Australia than for Bos taurus breeds in temperate Australia. Weighted mean estimates of heritabilities for the direct component of weaning weight were 39% for the Brahman breed and 30% for Zebu-derived breeds in northern Australia compared with 13% for Bos taurus breeds in temperate areas of Australia. Mean estimates for the maternal component of weaning weight were 5, 24 and 13% respectively. Mean heritabilities for yearling and 550 day weights for Zebu derived breeds in northern Australia (24 and 25%) were similar to those for Bos taurus breeds in temperate areas, though estimates for Brahmans were higher (39 and 39%). Published estimates of heritabilities of later weights (700 and 900 days), which are most relevant to northern Australian production systems, were rare but averaged between 32 and 45% for Zebu-derived breeds and Brahmans. Weighted mean heritability for female calving success was 14% and for realised bull fertility was 5%. Published estimates of heritabilities of scrota1 circumference averaged 31%, and testosterone response to GNRH stimulation was 52%. Heritabilities of resistance to various environmental stresses were all moderate with weighted means between 20 and 34%. Genetic correlations between growth, reproduction and resistance to environmental stresses are also reviewed. There appears to be predictable variation in estimates of parameters between breeds in different environments which is related to level of resistance to environmental stresses, and this is likely to affect the prediction of breeding values for cattle in northern Australia.

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