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The reproductive performance of beef cattle in 5 herds mated all year round in north-west Queensland was examined from 1970 to 1973. Conception rates, conception patterns and branding rates were used to assess annual reproductive performance. The level of loss between the times of confirmed pregnancy and branding was defined. The mean annual conception rate was 83.1% with individual property means ranging from 75.4 to 90.9%. Conception rates for heifers, first calf cows and mature cows were 83.9%, 80.6% and 84.7% respectively. Conception patterns were influenced by seasonal conditions, 68.1% of conceptions occurring in the wet season, between December and May. In this region, conception patterns were highly correlated with rainfall during the previous month. Losses between the times of confirmed pregnancy and branding ranged from 5.9 to 27.7%. Body condition of animals varied and was dependent upon lactation, seasonal and parity effects.

Sperm chromatin status was assessed in 565 Zebu and Zebu crossbred beef bulls in extensive tropical environments using the sperm chromatin structure assay (SCSA). The SCSA involved exposure of sperm to acid hydrolysis for 0.5 or 5.0 minutes, followed by flow cytometry to ascertain relative amounts of double-stranded (normal) and single-stranded (denatured) DNA, which was used to generate a DNA fragmentation index (%DFI). With conventional SCSA (0.5-minute SCSA), 513 bulls (91%) had15 %DFI, 24 bulls (4%) had 15 to 27 %DFI, and 28 bulls (5%) had27 %DFI. In 5.0-minute SCSA, 432 bulls (76%) had15 %DFI, 68 bulls (12%) had 15 to 27 %DFI and 65 bulls (12%) had27 %DFI. For most bulls, the SCSA was repeatable on two to four occasions; however, because most bulls had15 %DFI, repeatability of the SCSA will need to be determined in a larger number of bulls in the 15 to 27 %DFI and27 %DFI categories. The %DFI was negatively correlated with several bull semen parameters and the strongest negative correlation was with normal sperm. There was a strong positive correlation between %DFI and sperm head abnormalities. Based on these findings, most Zebu beef bulls in extensive tropical environments had relatively stable sperm chromatin. Based on the apparent negative correlations with conventional semen parameters, we inferred that the SCSA measured a unique feature of sperm quality, which has also been suggested for other species. Further studies on the relationships between sperm chromatin stability and fertility are required in beef bulls before chromatin status can be used as an additional predictor of the siring capacity of individual bulls in extensive multiple-sire herds.

The genetics of reproduction is poorly understood because the heritabilities of traits currently recorded are low. To elucidate the genetics underlying reproduction in beef cattle, we performed a genome-wide association study using the bovine SNP50 chip in 2 tropically adapted beef cattle breeds, Brahman and Tropical Composite. Here we present the results for 3 female reproduction traits: 1) age at puberty, defined as age in days at first observed corpus luteum (CL) after frequent ovarian ultrasound scans (AGECL); 2) the postpartum anestrous interval, measured as the number of days from calving to first ovulation postpartum (first rebreeding interval, PPAI); and 3) the occurrence of the first postpartum ovulation before weaning in the first rebreeding period (PW), defined from PPAI. In addition, correlated traits such as BW, height, serum IGF1 concentration, condition score, and fatness were also examined. In the Brahman and Tropical Composite cattle, 169 [false positive rate (FPR) = 0.262] and 84 (FPR = 0.581) SNP, respectively, were significant (P < 0.001) for AGECL. In Brahman, 41% of these significant markers mapped to a single chromosomal region on BTA14. In Tropical Composites, 16% of these significant markers were located on BTA5. For PPAI, 66 (FPR = 0.67) and 113 (FPR = 0.432) SNP were significant (P < 0.001) in Brahman and Tropical Composite, respectively, whereas for PW, 68 (FPR = 0.64) and 113 (FPR = 0.432) SNP were significant (P < 0.01). In Tropical Composites, the largest concentration of PPAI markers were located on BTA5 [19% (PPAI) and 23% (PW)], and BTA16 [17% (PPAI) and 18% (PW)]. In Brahman cattle, the largest concentration of markers for postpartum anestrus was located on BTA3 (14% for PPAI and PW) and BTA14 (17% PPAI). Very few of the significant markers for female reproduction traits for the Brahman and Tropical Composite breeds were located in the same chromosomal regions. However, fatness and BW traits as well as serum IGF1 concentration were found to be associated with similar genome regions within and between breeds. Clusters of SNP associated with multiple traits were located on BTA14 in Brahman and BTA5 in Tropical Composites.

The overall objective of one of the major research programs in the Co-operative Research Centre (CRC) for Beef Genetic Technologies is to ‘Improve female reproductive performance’ in tropical, northern Australian beef cattle herds. To address this overall objective, a quantitative genetics project focused on investigation of male reproductive traits was designed and linked to three female reproduction–focussed projects, (i) discovery of genes associated with post-partum re-conception and age at puberty; (ii) expression of genes associated with post-partum re-conception; and (iii) early predictors of lifetime female reproductive performance. During the initial planning of this male reproductive traits project, the CRC Scientific Review Committee recommended that the research team investigate and evaluate potentially new, early-life (i.e able to be measured before 2 years of age) predictors of both male and female reproductive performance. To address this recommendation, the following was carried out: (i) criteria for selection of traditional and candidate traits were established; (ii) methodology for tabulation of potential traits/phenotypes that define male and female reproductive function was developed; and (iii) a systematic scientific review of early-life predictors of male and female fertility was prepared. This review concluded that although factors that might be useful in predicting male reproductive performance have been studied for many years, there was relatively little useful information available to meet the objectives of this review. It was also concluded that the direction of future research should be guided not only by previous research which was scarce, but also by speculative hypotheses arising from an understanding of the physiological, endocrinological and genetic processes active in reproduction. A small number of new traits were recommended in addition to traditional sperm morphology, sexual behaviour, anatomical structure and growth traits. Potential additional traits include measurement of gonadotrophin-releasing hormone-stimulated luteinizing hormone (GnRH-stimulated LH); inhibin; several seminal plasma proteins (osteopontin, spermadhesin and seminal plasma proteins BSP30 and phospholipase A2 could be used in an index); 11β-hydroxysteriod dehydrogenase; and leptin. In addition, the potential also exists to screen animals for a number of genetic markers associated with age of puberty, follicular recruitment and ovulation rate and genes associated with bovine seminal plasma protein and testosterone production. Insulin-like growth factor-1 (IGF-1) measurements are included because of their association with growth parameters, and an additional analysis demonstrated associations with male and female reproductive traits. Some of these factors have been previously evaluated in small numbers of animals of various species under intensive management conditions. Therefore, there is a need to evaluate these factors in much larger numbers of beef cattle grazing semi-extensive tropical production systems in northern Australia to determine their value in improving beef cattle enterprise profitability through improved herd fertility.

A review of factors that may impact on the capacity of beef cattle females, grazing semi-extensive to extensive pastures in northern Australia, to conceive, maintain a pregnancy and wean a calf was conducted. Pregnancy and weaning rates have generally been used to measure the reproductive performance of herds. However, this review recognises that reproductive efficiency and the general measures associated with it more effectively describe the economic performance of beef cattle enterprises. More specifically, reproductive efficiency is influenced by (1) pregnancy rate which is influenced by (i) age at puberty; (ii) duration of post-partum anoestrus; (iii) fertilisation failure and (iv) embryo survival; while (2) weight by number of calves per breeding female retained for mating is influenced by (i) cow survival; (ii) foetal survival; and (iii) calf survival; and (3) overall lifetime calf weight weaned per mating. These measures of reproductive efficiency are discussed in depth. Further, a range of infectious and non-infectious factors, namely, environmental, physiological, breed and genetic factors and their impact on these stages of the reproductive cycle are investigated and implications for the northern Australian beef industry are discussed. Finally, conclusions and recommendations to minimise reproductive inefficiencies based on current knowledge are presented.

This experiment assessed the effects of different quality and quantity of handling and quality of the holding yard environment on the productivity and physiological parameters indicative of stress in beef cattle. One-hundred-and-forty-four steers were given one of three human handling and yarding experiences on six occasions during a 12-month grazing period post-weaning (backgrounding): Good handling/yarding, Poor handling/yarding and Minimal handling/yarding. At the end of this phase the cattle were lot-fed for 78 days, with no handling/yarding treatments imposed, before being transported for commercial slaughter. Temperament was assessed by flight speed (FS) and a fear of humans (FOH) test, which measured the proximity to a stimulus person (ZA), the closest approach to the person (CA) and the amount the cattle moved around the test arena (TT). Mid-way through backgrounding, the Minimal treatment group was heavier than the Good, which was heavier than the Poor (mean weights 207, 201 and 194 kg, respectively; P = 0.05; LSD = 5.4), but by the end of backgrounding there was no difference between treatments and treatment did not affect liveweight during lot-feeding. At the end of backgrounding, plasma cortisol levels were significantly lower (P < 0.001) in the Good treatment group compared to the Poor and Minimal groups but at the end of lot-feeding there was no significant difference between the groups. Treatment affected plasma non-esterified fatty acid levels in backgrounding (P = 0.060) and lot-feeding (P = 0.046) with levels being higher in the Minimal than the Good and Poor groups (backgrounding: 0.52, 0.44 and 0.47 nmol/L, respectively; SE 0.02; lot-feeding: 0.46, 0.41 and 0.41 mmol/L, respectively; LSD = 0.05). Significant weak to moderate (r-value

Serving capacity studies were conducted on Santa Gertrudis, 5/8 Brahman, Brahman and Belmont Red bulls at 10 sites. Modifications, such as providing prior sexual experience, using females in oestrus and comparing restrained with unrestrained females, were made to the standard Bos taurus serving capacity test in a series of experiments with Santa Gertrudis bulls. Providing sexual experience to virgin bulls prior to testing improved the number of serves and libido scores in a serving capacity test. In serving capacity tests that used restrained females, expressions of sexual behaviour of bulls were not improved by having females in oestrus compared with non-oestrus females. There were more sexual behaviours, particularly mounts, in serving capacity tests involving restrained rather than unrestrained females. Summary statistics were collated from over 1100 serving capacity tests, in the 2 months prior to mating, across the 10 sites. In serving capacity tests using restrained females, in bulls of the same age, there were more expressions of sexual behaviours (except interest) in Belmont Red than in Brahman or 5/8 Brahman bulls with Santa Gertrudis bulls intermediate. The percentage of bulls displaying serves tended to increase with age; 82, 83 and 86% of 2-, 3- and ≥4-year-old Belmont Red bulls, respectively, completed 1 or more serves. This compared with 50, 50 and 66% of 2-, 3- and ≥4-year-old Santa Gertrudis bulls and 31% of 2-year-old Brahman bulls. Between 2 and 9% of bulls did not display any sexual behaviour in serving capacity tests with restrained females. Across genotypes, there were few and inconsistent relationships between either mounts or serves and liveweight, condition score, scrotal circumference, testicular tone and sheath measurements. The exceptions were in 2-year-old Brahmans where mounts were negatively correlated (r=−0.61; P

A systematic breeding soundness examination, including assessment of serving capacity was conducted on 5/8 Brahman, Brahman and Belmont Red bulls, most aged 2–4 years, at 12 different cattle properties across northern Australia. A subset of bulls (n=235) were subsequently mated in various groups, as multiple-sires, to cows and heifers at bull:female ratios of 2.5–6%. The number of calves sired by individual bulls (calf output) was determined by DNA typing for paternity. Overall, the incidence of physical abnormalities that were judged likely to result in reduced reproductive performance was low (5.6–12% of bulls). Measures of key physical traits scrotal circumference, sheath depth (vertical distance from ventral abdominal wall to preputial orifice), and sheath score were moderately to highly repeatable. Except in Belmont Red bulls, liveweight was positively correlated with scrotal circumference (r=0.36–0.78; P

Calf output of bulls was derived using DNA typing for paternity following multiple-sire mating at two sites in northern Australia. At Swan’s Lagoon Beef Cattle Research Station, 12, mixed-age, Brahman cross bulls were continuously mated with an average of 325 females in a 22 km2 open-savannah paddock. Water was available in two troughs. Behaviour of the bulls and location of cows were monitored. At Kamilaroi Station, 2- to 2.5-year-old Brahman bulls were introduced to the study. Twenty-four bulls (HIGH%) were mated in an 84 km2 paddock for 3.5 months to 411 heifers in 1995/1995 and for 4.5 months to 350 heifers and 320 first-lactation cows in 1995/1996. A second group of 10 bulls (LOW%) selected on reproductive soundness was mated concurrently in a neighbouring 60 km2 paddock to 411 heifers in 1995/1995 and to 350 heifers and 298 first-lactation cows in 1995/1996. In each paddock in both years, 300–350 females were expected to cycle during mating. Both paddocks were flat and semi-forested and water was available only at troughs. At both sites, detailed physical and reproductive examinations of all bulls were conducted prior to and post-mating. Calf output of individual bulls was highly variable but repeatable (r=0.6–0.7) between years. Up to 90% of the 270–380 calves resulting from each mating were sired by between 6 and 8 bulls. Reducing from 3.7 to 2.8% bulls:females at Swan’s Lagoon did not delay conceptions. At Kamilaroi, reproductively sound bulls achieved an estimated 5–6 conceptions per week over the peak mating period when sufficient cycling females were available. Differences in pregnancy rates between paddocks appeared due to differences in nutrition and it appeared that conceptions were not delayed with LOW% vs. HIGH% bulls. Variance between bulls in calf output was substantially lower when fewer bulls were used. Bull attrition occurred each year in the HIGH% paddock but not in the LOW% paddock. Calf output was unrelated to body condition of bulls. Seven of the 12 bulls in one 2-year period at Swan’s Lagoon appeared to restrict their movement range to 250–750 ha for 90–100% of the time. These ranges expanded when the bull:female ratio was reduced. Only one of the nine bulls remained within a 500 ha home range for at least 85% of the time during peak mating in 1998 at 2.8% bulls:females. In previous years with 3.7% bulls:females, up to eight of the 12 bulls had remained within a 500 ha home range for 85% of the time. Bull behaviour related to high calf output included restricted movement range, grazing with females at a majority of observations, stable social behaviour, and social dominance. These observations demonstrate that multiple-sire mating of reproductively sound Brahman and Brahman-derived bulls at 2.5% of cycling females will not jeopardise herd fertility under extensive management in northern Australia.

To compare reproduction in extensively managed, tropically adapted beef cows that were either seropositive or seronegative to Neospora caninum.Longitudinal study of cows within management groups.Compare pregnancy with weaning outcomes for 502 seropositive and 3255 seronegative cows in 25 management groups.We found N. caninum in all herds, with an average of 20% of 2640 tested animals seropositive within management group; prevalence varied between 0% and 94%. At 7 of 10 sites assessed, there was evidence of horizontal transmission of N. caninum. There was no overall difference in pregnancy rate (79% vs 75%; P0.05), reproductive wastage after confirmed pregnancy diagnosis (11% vs 10%; P0.05) or weaning rate (67% vs 68%; P0.05) between seronegative and seropositive cows, respectively. In one herd where a combination of risk factors for N. caninum was present, a significant reduction in pregnancy rate occurred after the 6 months mating (85% vs 69%; P0.05). The fetal and calf losses observed were lowest in south-east Queensland (4.3% of 117 pregnancies), highest in north-west Queensland (15.5% of 413 pregnancies) and intermediate in north-east Queensland (10.2% of 1625 pregnancies). Other infectious agents that are known to cause reproductive wastage were endemic in many herds, though none appeared to cause significant fetal or calf loss in this study.Despite a high prevalence of N. caninum, there was no apparent effect on beef cattle reproduction, but there is potential to cause reproductive wastage if known risk factors to neosporosis are in effect.

The genetics of reproduction is poorly understood because the heritabilities of traits currently recorded are low. To elucidate the genetics underlying reproduction in beef cattle, we performed a genome-wide association study using the bovine SNP50 chip in 2 tropically adapted beef cattle breeds, Brahman and Tropical Composite. Here we present the results for 3 female reproduction traits: 1) age at puberty, defined as age in days at first observed corpus luteum (CL) after frequent ovarian ultrasound scans (AGECL); 2) the postpartum anestrous interval, measured as the number of days from calving to first ovulation postpartum (first rebreeding interval, PPAI); and 3) the occurrence of the first postpartum ovulation before weaning in the first rebreeding period (PW), defined from PPAI. In addition, correlated traits such as BW, height, serum IGF1 concentration, condition score, and fatness were also examined. In the Brahman and Tropical Composite cattle, 169 [false positive rate (FPR) = 0.262] and 84 (FPR = 0.581) SNP, respectively, were significant (P0.001) for AGECL. In Brahman, 41% of these significant markers mapped to a single chromosomal region on BTA14. In Tropical Composites, 16% of these significant markers were located on BTA5. For PPAI, 66 (FPR = 0.67) and 113 (FPR = 0.432) SNP were significant (P0.001) in Brahman and Tropical Composite, respectively, whereas for PW, 68 (FPR = 0.64) and 113 (FPR = 0.432) SNP were significant (P0.01). In Tropical Composites, the largest concentration of PPAI markers were located on BTA5 [19% (PPAI) and 23% (PW)], and BTA16 [17% (PPAI) and 18% (PW)]. In Brahman cattle, the largest concentration of markers for postpartum anestrus was located on BTA3 (14% for PPAI and PW) and BTA14 (17% PPAI). Very few of the significant markers for female reproduction traits for the Brahman and Tropical Composite breeds were located in the same chromosomal regions. However, fatness and BW traits as well as serum IGF1 concentration were found to be associated with similar genome regions within and between breeds. Clusters of SNP associated with multiple traits were located on BTA14 in Brahman and BTA5 in Tropical Composites.

The overall objective of one of the major research programs in the Co-operative Research Centre (CRC) for Beef Genetic Technologies is to 'Improve female reproductive performance' in tropical, northern Australian beef cattle herds. To address this overall objective, a quantitative genetics project focused on investigation of male reproductive traits was designed and linked to three female reproduction-focussed projects, (i) discovery of genes associated with post-partum re-conception and age at puberty; (ii) expression of genes associated with post-partum re-conception; and (iii) early predictors of lifetime female reproductive performance. During the initial planning of this male reproductive traits project, the CRC Scientific Review Committee recommended that the research team investigate and evaluate potentially new, early-life (i.e able to be measured before 2 years of age) predictors of both male and female reproductive performance. To address this recommendation, the following was carried out: (i) criteria for selection of traditional and candidate traits were established; (ii) methodology for tabulation of potential traits/phenotypes that define male and female reproductive function was developed; and (iii) a systematic scientific review of early-life predictors of male and female fertility was prepared. This review concluded that although factors that might be useful in predicting male reproductive performance have been studied for many years, there was relatively little useful information available to meet the objectives of this review. It was also concluded that the direction of future research should be guided not only by previous research which was scarce, but also by speculative hypotheses arising from an understanding of the physiological, endocrinological and genetic processes active in reproduction. A small number of new traits were recommended in addition to traditional sperm morphology, sexual behaviour, anatomical structure and growth traits. Potential additional traits include measurement of gonadotrophin-releasing hormone-stimulated luteinizing hormone (GnRH-stimulated LH); inhibin; several seminal plasma proteins (osteopontin, spermadhesin and seminal plasma proteins BSP30 and phospholipase A(2) could be used in an index); 11β-hydroxysteriod dehydrogenase; and leptin. In addition, the potential also exists to screen animals for a number of genetic markers associated with age of puberty, follicular recruitment and ovulation rate and genes associated with bovine seminal plasma protein and testosterone production. Insulin-like growth factor-1 (IGF-1) measurements are included because of their association with growth parameters, and an additional analysis demonstrated associations with male and female reproductive traits. Some of these factors have been previously evaluated in small numbers of animals of various species under intensive management conditions. Therefore, there is a need to evaluate these factors in much larger numbers of beef cattle grazing semi-extensive tropical production systems in northern Australia to determine their value in improving beef cattle enterprise profitability through improved herd fertility.

A systematic breeding soundness examination, including assessment of serving capacity was conducted on 5/8 Brahman, Brahman and Belmont Red bulls, most aged 2-4 years, at 12 different cattle properties across northern Australia. A subset of bulls (n=235) were subsequently mated in various groups, as multiple-sires, to cows and heifers at bull:female ratios of 2.5-6%. The number of calves sired by individual bulls (calf output) was determined by DNA typing for paternity. Overall, the incidence of physical abnormalities that were judged likely to result in reduced reproductive performance was low (5.6-12% of bulls). Measures of key physical traits scrotal circumference, sheath depth (vertical distance from ventral abdominal wall to preputial orifice), and sheath score were moderately to highly repeatable. Except in Belmont Red bulls, liveweight was positively correlated with scrotal circumference (r=0.36-0.78; P0.01), and both traits increased with age. In 2-year-old Brahman bulls only, percent normal spermatozoa was correlated with scrotal circumference (r=0.34; P0.05). However, 12 and 15% of Santa Gertrudis and Brahman bulls, respectively, with greater than or equal to the recommended threshold values for scrotal circumferences, had less than 50% morphologically normal spermatozoa. Size and conformation of the umbilicus was associated with conformation of the sheath, and influenced mating ability in 2-year-old Brahman and 3-year-old Santa Gertrudis bulls. In 2-year-old Brahman bulls umbilical cord thickness was positively related (r=0.36; P0.05) to sheath depth, and negatively related (r=-0.65; P0.05) to number of mounts and serves in a serving capacity test. In 3-year-old Santa Gertrudis bulls navel (external umbilical scar) score was negatively related to the number of serves (r=-0.53; P0.01) in a serving capacity test. None of the physical traits measured were consistently included in the final regression model for calf output for each breed.

Serving capacity studies were conducted on Santa Gertrudis, 5/8 Brahman, Brahman and Belmont Red bulls at 10 sites. Modifications, such as providing prior sexual experience, using females in oestrus and comparing restrained with unrestrained females, were made to the standard Bos taurus serving capacity test in a series of experiments with Santa Gertrudis bulls. Providing sexual experience to virgin bulls prior to testing improved the number of serves and libido scores in a serving capacity test. In serving capacity tests that used restrained females, expressions of sexual behaviour of bulls were not improved by having females in oestrus compared with non-oestrus females. There were more sexual behaviours, particularly mounts, in serving capacity tests involving restrained rather than unrestrained females. Summary statistics were collated from over 1100 serving capacity tests, in the 2 months prior to mating, across the 10 sites. In serving capacity tests using restrained females, in bulls of the same age, there were more expressions of sexual behaviours (except interest) in Belmont Red than in Brahman or 5/8 Brahman bulls with Santa Gertrudis bulls intermediate. The percentage of bulls displaying serves tended to increase with age; 82, 83 and 86% of 2-, 3- andor =4-year-old Belmont Red bulls, respectively, completed 1 or more serves. This compared with 50, 50 and 66% of 2-, 3- andor =4-year-old Santa Gertrudis bulls and 31% of 2-year-old Brahman bulls. Between 2 and 9% of bulls did not display any sexual behaviour in serving capacity tests with restrained females. Across genotypes, there were few and inconsistent relationships between either mounts or serves and liveweight, condition score, scrotal circumference, testicular tone and sheath measurements. The exceptions were in 2-year-old Brahmans where mounts were negatively correlated (r=-0.61; P0.05) with umbilicus thickness and in 3-year-old Santa Gertrudis bulls, where serves (r=-0.53; P0.01) and mounts+serves (r=-0.49; P0.01) were negatively correlated with navel score. Measures of sexual behaviour were unable to consistently predict calf output of bulls in multiple-sire mating groups in extensive pastoral conditions. The main value of the serving capacity test in these genotypes is to identify whether a bull is capable of natural service.

Calf output of bulls was derived using DNA typing for paternity following multiple-sire mating at two sites in northern Australia. At Swan's Lagoon Beef Cattle Research Station, 12, mixed-age, Brahman cross bulls were continuously mated with an average of 325 females in a 22km2 open-savannah paddock. Water was available in two troughs. Behaviour of the bulls and location of cows were monitored. At Kamilaroi Station, 2- to 2.5-year-old Brahman bulls were introduced to the study. Twenty-four bulls (HIGH%) were mated in an 84km2 paddock for 3.5 months to 411 heifers in 1995/1995 and for 4.5 months to 350 heifers and 320 first-lactation cows in 1995/1996. A second group of 10 bulls (LOW%) selected on reproductive soundness was mated concurrently in a neighbouring 60km2 paddock to 411 heifers in 1995/1995 and to 350 heifers and 298 first-lactation cows in 1995/1996. In each paddock in both years, 300-350 females were expected to cycle during mating. Both paddocks were flat and semi-forested and water was available only at troughs. At both sites, detailed physical and reproductive examinations of all bulls were conducted prior to and post-mating.Calf output of individual bulls was highly variable but repeatable (r=0.6-0.7) between years. Up to 90% of the 270-380 calves resulting from each mating were sired by between 6 and 8 bulls. Reducing from 3.7 to 2.8% bulls:females at Swan's Lagoon did not delay conceptions. At Kamilaroi, reproductively sound bulls achieved an estimated 5-6 conceptions per week over the peak mating period when sufficient cycling females were available. Differences in pregnancy rates between paddocks appeared due to differences in nutrition and it appeared that conceptions were not delayed with LOW% vs. HIGH% bulls. Variance between bulls in calf output was substantially lower when fewer bulls were used. Bull attrition occurred each year in the HIGH% paddock but not in the LOW% paddock. Calf output was unrelated to body condition of bulls. Seven of the 12 bulls in one 2-year period at Swan's Lagoon appeared to restrict their movement range to 250-750ha for 90-100% of the time. These ranges expanded when the bull:female ratio was reduced. Only one of the nine bulls remained within a 500ha home range for at least 85% of the time during peak mating in 1998 at 2.8% bulls:females. In previous years with 3.7% bulls:females, up to eight of the 12 bulls had remained within a 500ha home range for 85% of the time. Bull behaviour related to high calf output included restricted movement range, grazing with females at a majority of observations, stable social behaviour, and social dominance. These observations demonstrate that multiple-sire mating of reproductively sound Brahman and Brahman-derived bulls at 2.5% of cycling females will not jeopardise herd fertility under extensive management in northern Australia.

Reproduction records from 2137 cows first mated at 2 years of age and recorded through to 8.5 years of age were used to study the genetics of early and lifetime reproductive performance from two genotypes (1020 Brahman and 1117 Tropical Composite) in tropical Australian production systems. Regular ultrasound scanning of the reproductive tract, coupled with full recording of mating, calving and weaning histories, allowed a comprehensive evaluation of a range of reproductive traits. Results showed components traits of early reproductive performance had moderate to high heritabilities, especially in Brahmans. The heritability of lactation anoestrous interval in 3-year-old cows was 0.51 ± 0.18 and 0.26 ± 0.11 for Brahman and Tropical Composite, respectively. Heritabilities of binary reproductive output traits (conception rate, pregnancy rate, calving rate and weaning rate) from first and second matings were generally moderate to high on the underlying scale. Estimates ranged from 0.15 to 0.69 in Brahman and 0.15 to 0.34 in Tropical Composite, but were considerably lower when expressed on the observed scale, particularly for those traits with high mean levels. Heritabilities of lifetime reproduction traits were low, with estimates of 0.11 ± 0.06 and 0.07 ± 0.06 for lifetime annual weaning rate in Brahman and Tropical Composite, respectively. Significant differences in mean reproductive performance were observed between the two genotypes, especially for traits associated with anoestrus in first-lactation cows. Genetic correlations between early-in-life reproductive measures and lifetime reproduction traits were moderate to high. Genetic correlations between lactation anoestrous interval and lifetime annual weaning rate were –0.62 ± 0.24 in Brahman and –0.87 ± 0.32 in Tropical Composite. The results emphasise the substantial opportunity that exists to genetically improve weaning rates in tropical beef cattle breeds by focusing recording and selection on early-in-life female reproduction traits, particularly in Brahman for traits associated with lactation anoestrus.

Genetic correlations of young bull and heifer puberty traits with measures of early and lifetime female reproductive performance were estimated in two tropical beef cattle genotypes. Heifer age at puberty was highly (r(g) = -0.71 +/- 0.11) and moderately (r(g) = -0.40 +/- 0.20) genetically correlated with pregnancy rate at first annual mating (mating 1) and lifetime annual calving rate, respectively in Brahman (BRAH). In Tropical Composite (TCOMP), heifer age at puberty was highly correlated with reproductive outcomes from the first re-breed (mating 2), mainly due to its association with lactation anoestrous interval (r(g) = 0.72 +/- 0.17). Scrotal circumference were correlated with heifer age at puberty (r(g) = -0.41 +/- 0.11 at 12 months in BRAH; -0.30 +/- 0.13 at 6 months in TCOMP) but correlations were lower with later female reproduction traits. Bull insulin-like growth factor-I was correlated with heifer age at puberty (r(g) = -0.56 +/- 0.11 in BRAH; -0.43 +/- 0.11 in TCOMP) and blood luteinising hormone concentration was moderately correlated with lactation anoestrous interval (r(g) = 0.59 +/- 0.23) in TCOMP. Semen quality traits, including mass activity, motility and percent normal sperm were genetically correlated with lactation anoestrus and female lifetime female reproductive traits in both genotypes, but the magnitudes of the relationships differed with bull age at measurement. Preputial eversion and sheath scores were genetically associated with lifetime calving and weaning rates in both genotypes. Several of the early-in-life male and female measures examined were moderately to highly genetically correlated with early and lifetime female reproduction traits and may be useful as indirect selection criteria for improving female reproduction in tropical breeds in northern Australia.

Early-in-life female and male measures with potential to be practical genetic indicators were chosen from earlier analyses and examined together with genomic measures for multi-trait use to improve female reproduction of Brahman cattle. Combinations of measures were evaluated on the genetic gains expected from selection of sires and dams for each of age at puberty (AGECL, i.e. first observation of a corpus luteum), lactation anoestrous interval in 3-year-old cows (LAI), and lifetime annual weaning rate (LAWR, i.e. the weaning rate of cows based on the number of annual matings they experienced over six possible matings). Selection was on an index of comparable records for each combination. Selection intensities were less than theoretically possible but assumed a concerted selection effort was able to be made across the Brahman breed. The results suggested that substantial genetic gains could be possible but need to be confirmed in other data. The estimated increase in LAWR in 10 years, for combinations without or with genomic measures, ranged from 8 to 12 calves weaned per 100 cows from selection of sires, and from 12 to 15 calves weaned per 100 cows from selection of sires and dams. Corresponding reductions in LAI were 60–103 days or 94–136 days, and those for AGECL were 95–125 or 141–176 days, respectively. Coat score (a measure of the sleekness or wooliness of the coat) and hip height in females, and preputial eversion and liveweight in males, were measures that may warrant wider recording for Brahman female reproduction genetic evaluation. Pregnancy-test outcomes from Matings 1 and 2 also should be recorded. Percentage normal sperm may be important to record for reducing LAI and scrotal size and serum insulin-like growth factor-I concentration in heifers at 18 months for reducing AGECL. Use of a genomic estimated breeding value (EBV) in combination with other measures added to genetic gains, especially at genomic EBV accuracies of 40%. Accuracies of genomic EBVs needed to approach 60% for the genomic EBV to be the most important contributor to gains in the combinations of measures studied.

A total of 4063 young bulls of two tropical genotypes (1639 Brahman and 2424 Tropical Composite) raised in northern Australia were evaluated for a comprehensive range of production and reproduction traits up to 24 months of age. Prior to weaning, peripheral blood concentrations of luteinising hormone (LH) and inhibin were measured at 4 months of age. At weaning (6 months) blood insulin-like growth factor-1 (IGF-I) and flight time were recorded. Body composition traits of fat depth and eye-muscle area were determined by ultrasonography at 15 months of age when additional measurements of liveweight, hip height and body condition score were recorded. Bull breeding soundness was evaluated at ~12, 18 and 24 months of age when measurements of scrotal circumference, sheath score, semen mass activity, progressive motility of individual sperm and percent morphologically normal sperm were recorded. Magnitude of heritability and genetic correlations changed across time for some traits. Heritability of LH, inhibin, IGF-I and of 18-month scrotal circumference, mass activity, progressive motility and percent normal sperm was 0.31, 0.74, 0.44, 0.75, 0.24, 0.15 and 0.25, respectively, for Brahmans and 0.48, 0.72, 0.36, 0.43, 0.13, 0.15 and 0.20, respectively, for Tropical Composites. Inhibin and IGF-I had moderate genetic association with percent normal sperm at 24 months in Brahmans but low to negligible associations in Tropical Composites. Body condition score in Brahmans and sperm motility (mass and individual) traits in both genotypes had moderate to strong genetic correlation with percent normal sperm and may prove useful candidates for indirect selection. There is scope to increase scrotal circumference by selection and this will be associated with favourable correlated responses of improved semen quality in both genotypes. The lack of genetic antagonism among bull traits indicates that selection for improved semen quality will not adversely affect other production traits.

Hip height, body condition, subcutaneous fat, eye muscle area, percentage Bos taurus, fetal age and diet digestibility data were collected at 17 372 assessments on 2181 Brahman and tropical composite (average 28% Brahman) female cattle aged between 0.5 and 7.5 years of age at five sites across Queensland. The study validated the subtraction of previously published estimates of gravid uterine weight to correct liveweight to the non-pregnant status. Hip height and liveweight were linearly related (Brahman: P < 0.001, R2 = 58%; tropical composite P < 0.001, R2 = 67%). Liveweight varied by 12–14% per body condition score (5-point scale) as cows differed from moderate condition (P < 0.01). Parallel effects were also found due to subcutaneous rump fat depth and eye muscle area, which were highly correlated with each other and body condition score (r = 0.7–0.8). Liveweight differed from average by 1.65–1.66% per mm of rump fat depth and 0.71–0.76% per cm2 of eye muscle area (P < 0.01). Estimated dry matter digestibility of pasture consumed had no consistent effect in predicting liveweight and was therefore excluded from final models. A method developed to estimate full liveweight of post-weaning age female beef cattle from the other measures taken predicted liveweight to within 10 and 23% of that recorded for 65 and 95% of cases, respectively. For a 95% chance of predicted group average liveweight (body condition score used) being within 5, 4, 3, 2 and 1% of actual group average liveweight required 23, 36, 62, 137 and 521 females, respectively, if precision and accuracy of measurements matches that used in the research. Non-pregnant Bos taurus female cattle were calculated to be 10–40% heavier than Brahmans at the same hip height and body condition, indicating a substantial conformational difference. The liveweight prediction method was applied to a validation population of 83 unrelated groups of cattle weighed in extensive commercial situations on 119 days over 18 months (20 917 assessments). Liveweight prediction in the validation population exceeded average recorded liveweight for weigh groups by an average of 19 kg (~6%) demonstrating the difficulty of achieving accurate and precise animal measurements under extensive commercial grazing conditions.

Research into the genetics of whole herd profitability has been a focus of the Beef Cooperative Research Centre for Beef Genetic Technologies over the past decade and it has been identified that measures of male reproduction may offer a potential indirect means of selecting for improved female reproduction. This paper describes the experimental design and provides a descriptive analysis of an array of male traits in Brahman and Tropical Composite genotypes managed under the medium to high stress, semi-extensive to extensive production systems of northern Australia. A total of 1639 Brahman and 2424 Tropical Composite bulls with known pedigrees, bred and raised in northern Australia, were evaluated for a comprehensive range of productive and reproductive traits. These included blood hormonal traits (luteinising hormone, inhibin and insulin-like growth factor-I); growth and carcass traits (liveweight, body condition score, ultrasound scanned 12–13th rib fat, rump P8 fat, eye muscle area and hip height); adaptation traits (flight time and rectal temperature); and a bull breeding soundness evaluation (leg and hoof conformation, sheath score, length of everted prepuce, penile anatomy, scrotal circumference, semen mass activity, sperm motility and sperm morphology). Large phenotypic variation was evident for most traits, with complete overlap between genotypes, indicating that there is likely to be a significant opportunity to improve bull fertility traits through management and bull selection.

Sperm chromatin fragmentation is associated with subfertility, but its relationship with age progression in young bulls is poorly understood. The objective was to assess sperm chromatin fragmentation during the early post-pubertal development of 20 tropical composite bulls, using a sperm chromatin structure assay (SCSA) and sperm-bos-halomax (SBH). Bulls were subjected to bull breeding soundness evaluation (BBSE) at mean ages of 13, 18, and 24 mo. Traits measured included liveweight (WT), body condition score (BCS) and scrotal circumference (SC). Semen samples were collected by electroejaculation and assessed for mass activity (MA), motility (Mot), concentration (conc), sperm morphology and chromatin fragmentation. Concentration (r = 0.34, P = 0.0076), Mot (r = 0.36, P = 0.0041) and percentage of morphologic normal sperm (percent normal sperm (PNS); r = 0.31, P = 0.0132) were positively correlated with age. The percentage of sperm with proximal droplets (PD) was negatively correlated with age (r = -0.28, P = 0.0348), whereas neither SCSA nor SBH results were significantly correlated with age. The percentage of sperm with chromatin fragmentation using SCSA was correlated with PNS (r = -0.53, P < 0.0001), the percentage of sperm with head abnormalities (r = 0.68, P < 0.0001) and the percentage of intact sperm (Int) with SBH (r = -0.26, P = 0.0456). In summary, for assessment of sperm chromatin fragmentation, samples could be equally collected at 13, 18 or 24 mo of age, as results did not vary with age. (c) 2012 Elsevier Inc. All rights reserved.

The genetics of heifer performance in tropical 'wet' and 'dry' seasons, and relationships with steer performance, were studied in Brahman (BRAH) and Tropical Composite (TCOMP) (50% Bos indicus, African Sanga or other tropically adapted Bos taurus; 50% non-tropically adapted Bos taurus) cattle of northern Australia. Data were from 2159 heifers (1027 BRAH, 1132 TCOMP), representing 54 BRAH and 51 TCOMP sires. Heifers were assessed after post-weaning 'wet' (ENDWET) and 'dry' (ENDDRY) seasons. Steers were assessed post-weaning, at feedlot entry, over a 70-day feed test, and after ~120-day finishing. Measures studied in both heifers and steers were liveweight (LWT), scanned rump fat, rib fat and M. longissimus area (SEMA), body condition score (CS), hip height (HH), serum insulin-like growth factor-I concentration (IGF-I), and average daily gains (ADG). Additional steer measures were scanned intra-muscular fat %, flight time, and daily (DFI) and residual feed intake (RFI). Uni- and bivariate analyses were conducted for combined genotypes and for individual genotypes. Genotype means were predicted for a subset of data involving 34 BRAH and 26 TCOMP sires. A meta-analysis of genetic correlation estimates examined how these were related to the difference between measurement environments for specific traits. There were genotype differences at the level of means, variances and genetic correlations. BRAH heifers were significantly (P < 0.05) faster-growing in the 'wet' season, slower-growing in the 'dry' season, lighter at ENDDRY, and taller and fatter with greater CS and IGF-I at both ENDWET and ENDDRY. Heritabilities were generally in the 20 to 60% range for both genotypes. Phenotypic and genetic variances, and genetic correlations, were commonly lower for BRAH. Differences were often explained by the long period of tropical adaptation of B. indicus. Genetic correlations were high between corresponding measures at ENDWET and ENDDRY, positive between fat and muscle measures in TCOMP but negative in BRAH (mean of 13 estimates 0.50 and ᾰ0.19, respectively), and approximately zero between steer feedlot ADG and heifer ADG in BRAH. Numerous genetic correlations between heifers and steers differed substantially from unity, especially in BRAH, suggesting there may be scope to select differently in the sexes where that would aid the differing roles of heifers and steers in production. Genetic correlations declined as measurement environments became more different, the rates of decline (environment sensitivity) sometimes differing with genotype. Similar measures (LWT, HH and ADG; IGF-I at ENDWET in TCOMP) were genetically correlated with steer DFI in heifers as in steers. Heifer SEMA was genetically correlated with steer feedlot RFI in BRAH (0.75 ± 0.27 at ENDWET, 0.66 ± 0.24 at ENDDRY). Selection to reduce steer RFI would reduce SEMA in BRAH heifers but otherwise have only small effects on heifers before their first joining.

A total of 2115 heifers from two tropical genotypes (1007 Brahman and 1108 Tropical Composite) raised in four locations in northern Australia were ovarian-scanned every 4–6 weeks to determine the age at the first-observed corpus luteum (CL) and this was used to define the age at puberty for each heifer. Other traits recorded at each time of ovarian scanning were liveweight, fat depths and body condition score. Reproductive tract size was measured close to the start of the first joining period. Results showed significant effects of location and birth month on the age at first CL and associated puberty traits. Genotypes did not differ significantly for the age or weight at first CL; however, Brahman were fatter at first CL and had a small reproductive tract size compared with that of Tropical Composite. Genetic analyses estimated the age at first CL to be moderately to highly heritable for Brahman (0.57) and Tropical Composite (0.52). The associated traits were also moderately heritable, except for reproductive tract size in Brahmans (0.03) and for Tropical Composite, the presence of an observed CL on the scanning day closest to the start of joining (0.07). Genetic correlations among puberty traits were mostly moderate to high and generally larger in magnitude for Brahman than for Tropical Composite. Genetic correlations between the age at CL and heifer- and steer-production traits showed important genotype differences. For Tropical Composite, the age at CL was negatively correlated with the heifer growth rate in their first postweaning wet season (–0.40) and carcass marbling score (–0.49), but was positively correlated with carcass P8 fat depth (0.43). For Brahman, the age at CL was moderately negatively genetically correlated with heifer measures of bodyweight, fatness, body condition score and IGF-I, in both their first postweaning wet and second dry seasons, but was positively correlated with the dry-season growth rate. For Brahman, genetic correlations between the age at CL and steer traits showed possible antagonisms with feedlot residual feed intake (–0.60) and meat colour (0.73). Selection can be used to change the heifer age at puberty in both genotypes, with few major antagonisms with steer- and heifer-production traits.

The genetics of heifer performance in tropical ‘wet’ and ‘dry’ seasons, and relationships with steer performance, were studied in Brahman (BRAH) and Tropical Composite (TCOMP) (50% Bos indicus, African Sanga or other tropically adapted Bos taurus; 50% non-tropically adapted Bos taurus) cattle of northern Australia. Data were from 2159 heifers (1027 BRAH, 1132 TCOMP), representing 54 BRAH and 51 TCOMP sires. Heifers were assessed after post-weaning ‘wet’ (ENDWET) and ‘dry’ (ENDDRY) seasons. Steers were assessed post-weaning, at feedlot entry, over a 70-day feed test, and after ∼120-day finishing. Measures studied in both heifers and steers were liveweight (LWT), scanned rump fat, rib fat and M. longissimus area (SEMA), body condition score (CS), hip height (HH), serum insulin-like growth factor-I concentration (IGF-I), and average daily gains (ADG). Additional steer measures were scanned intra-muscular fat %, flight time, and daily (DFI) and residual feed intake (RFI). Uni- and bivariate analyses were conducted for combined genotypes and for individual genotypes. Genotype means were predicted for a subset of data involving 34 BRAH and 26 TCOMP sires. A meta-analysis of genetic correlation estimates examined how these were related to the difference between measurement environments for specific traits. There were genotype differences at the level of means, variances and genetic correlations. BRAH heifers were significantly (P < 0.05) faster-growing in the ‘wet’ season, slower-growing in the ‘dry’ season, lighter at ENDDRY, and taller and fatter with greater CS and IGF-I at both ENDWET and ENDDRY. Heritabilities were generally in the 20 to 60% range for both genotypes. Phenotypic and genetic variances, and genetic correlations, were commonly lower for BRAH. Differences were often explained by the long period of tropical adaptation of B. indicus. Genetic correlations were high between corresponding measures at ENDWET and ENDDRY, positive between fat and muscle measures in TCOMP but negative in BRAH (mean of 13 estimates 0.50 and –0.19, respectively), and approximately zero between steer feedlot ADG and heifer ADG in BRAH. Numerous genetic correlations between heifers and steers differed substantially from unity, especially in BRAH, suggesting there may be scope to select differently in the sexes where that would aid the differing roles of heifers and steers in production. Genetic correlations declined as measurement environments became more different, the rates of decline (environment sensitivity) sometimes differing with genotype. Similar measures (LWT, HH and ADG; IGF-I at ENDWET in TCOMP) were genetically correlated with steer DFI in heifers as in steers. Heifer SEMA was genetically correlated with steer feedlot RFI in BRAH (0.75 ± 0.27 at ENDWET, 0.66 ± 0.24 at ENDDRY). Selection to reduce steer RFI would reduce SEMA in BRAH heifers but otherwise have only small effects on heifers before their first joining.

This experiment tested the hypothesis that relocating cattle is detrimental to their growth. The study examined the effect of having relocated cattle mixed with, or segregated from, the local acclimatised cattle at the destination property. Bos indicus cross steers (120) were allocated to three groups and were relocated, in two separate cohorts, 980 km from northern Queensland to improved pastures in central Queensland. At the start of Phase 1, the control group (C) was moved 3 months before the other two groups. The remaining two groups grazed native pastures; one group was supplemented (SR) to increase growth rate similar to that expected from improved pasture in central Queensland and the other was not supplemented (R). At the end of Phase 1, C was significantly (P < 0.05) heavier than SR, which was significantly (P < 0.05) heavier than R. At the start of Phase 2, the SR and R groups were relocated and after transportation the R and SR groups lost 12 kg or 4.4% of liveweight and 18 kg or 5.7% of liveweight, respectively; this weight loss was recovered after 5 days. All steers were reallocated to segregated (SEG) or mixed (MIX) treatment groups forming six treatments (SEG.C, SEG.R and SEG.SR and MIX.C, MIX.R and MIX.SR). There were no significant differences in liveweights within the SEG treatments by 57 days or within the MIX treatments by 106 days after relocation. There were few if any significant differences in the plasma constituents and differential leucocyte counts of the steers and most results were within physiologically normal ranges. We conclude on the basis of these results and of other experiments that the anecdotal poor performance of cattle after relocation appears to be unfounded.

During mammalian spermiogenesis nucleosomal histone proteins bound to DNA are replaced by protamines. The integrity and stability of the protamine-DNA association in sperm can be measured using the sperm chromatin structure assay (SCSA). The recent emergence of compelling information from assisted reproduction in humans of a relationship between sperm chromatin stability and the establishment and maintenance of pregnancy has led to considerable interest in production and recreational animals.1 The aim in the present study was to determine the incidence of sperm chromatin instability amongst bulls in a subtropical region of northern Australia, as a first step in evaluating whether sperm chromatin instability is a contributing factor to reproductive wastage in cattle. Semen was obtained from 565 Bos indicus and Bos indicus x taurus bulls from northern and central Queensland aged between 20months and 10years. Samples were subjected to standard semen evaluation2 and aliquots stored in liquid nitrogen until chromatin integrity was determined using the SCSA.3 Samples exposed to the SCSA for 0.5min revealed 4.9% of bulls had a DFI >27% and this increased to 11.5% of bulls with DFI >27% when samples were exposed to the SCSA for 5 min. DFI was significantly correlated with sperm density, mass activity, motility and morphology. Location appeared to have a greater influence on DFI than genotype. Preliminary data from a small sample of bulls would suggest that a relatively high DFI can be repeatable for individual bulls. These findings indicate that sperm chromatin instability occurs in bulls in northern Australia although the prevalence might be considered to be relatively low. The relationship of sperm chromatin instability to the contribution of bulls to embryonic mortality requires further study and likewise the impact on reproductive wastage remains to be determined. (1)Boe-Hansen GB et al. (2005). Theriogenology 63, 1789.(2)Fitzpatrick LA et al. (2002). Anim. Reprod. Sci. 71, 39.(3)Evenson D and Jost L (2000). Methods Cell Sci. 22, 169.

Fifty Bos indicus steers, 2–3 years old, were exposed to aspects of a feedlot environment on their home property for 9 days (pre-exposed). A further 50 steers were placed in a holding paddock for the 9 days (naïve). Twenty steers in each group became 'focal animals' for periodic blood sampling and behaviour observations. The cattle were transported for 15 h (950 km) to an experimental feedlot where they were lot-fed for 100 days, with productivity (liveweight, body condition and feed intakes) and flight speeds recorded at intervals. A subjective fear of humans test was conducted on the pre-exposed group during the 9 days in the yards on the home property and carcass traits were measured on all cattle.Both groups lost substantial weight on the property and during transportation. On the property, the pre-exposed steers lost about 12% of their original liveweight and the naïve about 9%. Transit losses were a further 5 and 4% of pre-transport liveweights, respectively. The steers did not reach their initial liveweights until day 41 of feedlotting. The pre-exposure treatment did not affect final liveweight, but feed intakes were lower for the pre-exposed animals than the naïve ones during the first 16 days of feedlotting, and the pre-exposed steers had superior average daily gains and feed conversion efficiencies. These effects were probably due to a combination of compensation and improved feed digestibility, as a result of the pre-exposed animals being under-fed on the property, but receiving concentrated grain supplement. There was no effect of focal status on productivity.Flight speed and the subjective fear of humans test were significantly correlated. Neither treatment nor focal status affected flight speeds, but flight speeds decreased in the latter part of feedlotting, were highly correlated between days and negatively correlated with average daily gain and intakes.

One hundred and twenty Bos indicus cross steers were allocated to 3 treatments (good, mixed and poor) on the basis of flight speed, as a measure of cattle temperament. The cattle were lot-fed for 100 days and data collected at intervals on their temperament (flight speeds) and productivity (liveweight changes, body condition, pen feed intakes) during this time. After slaughter, data were collected on carcass traits and meat quality. Eating-quality attributes were measured in meat samples from 22 carcasses from each treatment. Flight speeds were highly correlated across animals and within treatments, showed little change in variability over time and were highly repeatable. Flight speed indicated a slight deterioration in temperament with time in the feedlot until day 70, suggesting an increasing fearfulness in the steers. Differences in flight speeds between treatments were maintained throughout the feedlotting period; poor-temperament animals retained poor temperaments and good retained good. Flight speed was correlated with measures of production, and flight speed measured at feedlot induction was a predictor of performance. Correlations and treatment effects showed that cattle with poor temperaments had poorer average daily gains, feed conversion efficiencies, body conditions and dressing percentages compared with those with good temperaments. Reduced performance in the poor-temperament animals may have resulted from their fearfulness and state of high arousal. Treatment (temperament grouping) did not influence carcass traits, but there was evidence of lower initial pH levels and indicators of 'heat-shortening' in the meat of steers with poor temperament compared with those with good temperament. These findings suggest that the poor temperament steers were more susceptible to pre-slaughter stressors than the good temperament animals. However, the meat quality differences were not detected in eating-quality measurements.

Rumen microbial populations were measured in Brahman-cross steers that were relocated from spear grass (Heteropogon contortus) dominant pastures in northern Queensland to buffel grass (Cenchrus ciliasis) dominant pastures in central Queensland, to assess whether aspects of rumen function may contribute to the sometimes reported depressed growth rates following relocation. Nine genera of ciliate protozoa (Isotricha, Dasytricha, Entodinia, Epidinium, Diplodinium, Ostracodinium, Metadinium, Elytroplastron, and Eudiplodinium) were recorded in the rumen fluid of the steers. In most steers all genera were present at any time and the generic mix persisted throughout the 10 months over which the study was conducted. Protozoal population composition fluctuated only slightly over the sampling period. Entodinia were predominant, occupying 50-70% of the population. Population density varied according to season, with the highest density (4-8×105 /mL rumen fluid) occurring in the wet season. Bacterial and protozoal populations were remarkably stable and little affected by relocation. Again, the major impact on population density was the season, with all carbohydrate (soluble sugar, starch, xylan, and cellulose) utilising bacterial subpopulations reaching the greatest density with the onset of the wet season.

The genetics of growth to 24 months, scrotal circumference (SC) at 24 months and temperaments at 6, 12 and 18 months in 7 year groups of F2 et seq., 1/2 Brahman, 1/2 Sahiwal, 3/4 Brahman and 3/4 Sahiwal bulls were investigated in the dry tropics of northern Queensland. Cattle tick (Boophilus microplus) and buffalo fly (Haematobia irritans exigua) resistance were also assessed at 24 months. Scrotal circumference at 24 months was highest in 1/2 Sahiwal crosses (28 cm v. 26-27 cm; P0.9); however, the rG of weaning weight with postweaning seasonal growth rates to 24 months were consistently negative (-0.09 to -0.71; P>0.05). The rG of SC with post-weaning growth rates were negative (-0.4 to -0.8). The rG of SC with weights up to 18 months were not significantly different to zero, but tended to be negative with weight at 24 months.

Strategies for culling on reproductive outcome were evaluated for 2 herds at Swan's Lagoon in the northern speargrass region and 1 herd at Kidman Springs in the semi-arid tropics by editing the records from actual culling to simulate more stringent culling policies. The greatest impact was for young cows, with 13.6 and 27.5% of 2-year-old cows in the 2 herds at Swan's Lagoon failing to rear a calf, and 39.8% at Kidman Springs failing to rear a calf. The corresponding failure rates as 3-year-old cows were 48.1, 54.9, and 80.2%, respectively. Culling for 2 consecutive reproductive failures at Kidman Springs resulted in cumulative wastage of cows >60% by 4 years of age. Other strategies based on 1 or 2 failures had cumulative wastage >SO% by 5 years of age and were too severe to be sustained in the harsh environment at Kidman Springs, with low productivity. At Swan's Lagoon, heifer replacement rates were 17.5-22.2% for strategies based on 2 failures and averaged 37.3% for a single reproductive failure but were 28.7% when failure as a 3-year-old was not penalised. At Kidman Springs, heifer replacement rates were 29.3% for 2 consecutive reproductive failures and reduced to 21.3% when 2-year-olds were retained but were very high (33.7-56.7%) for stricter culling strategies. With current branding rates, only culling on 2 reproductive failures in the speargrass region and extremely limited culling on 3 failures in the semi-arid tropics can be recommended as practical options. The lifetime number of calves reared from cows up to 10 years of age at Swan's Lagoon averaged 3.1 when culling was based on 2 failures and 2.2 for culling on a single failure; this increased to 2.8 calves reared when the strategy was relaxed for 3-year-olds. At Kidman Springs the number of calves reared was 2.3 with culling on 2 consecutive reproductive failures but was closer to the actual level at 2.9 when 2-year-old cows were not culled for reproductive failure.

Mortality and wastage rates and lifetime productivity for seasonally mated, Bos indicus cows were studied over 8000 cow year records from 1972 to 1992 at Swan's Lagoon in the subcoastal speargrass region of North Queensland. The proportional hazards model was used to estimate age-specific mortality and wastage rates, adjusted for cohort and genotype effects. The 1970-72 cohorts had an average mortality of 1.7% (range 0-4.2%), with this low overall rate tending to increase with age. The average mortality rate for the 1973-87 cohorts was 1.2% (range 0.5-2.6%), with no pattern with age. For 1970-72 cohorts, the average wastage rate was 8.9% and ranged from 2.1 to 18.3% with no clear age pattern. However, there was a clear age pattern for the 1973-87 cohorts, with an average wastage rate of 9.2% comprising very high rates (27.5%) for 2-year-olds and low rates (2.8-8.9%) for 3-7-year-olds, increasing to 11.9% for 8-year-olds and 14.2% for 9-year-olds. The heifer replacement rates to maintain a stable herd size were 17.5 and 19.2% for the 2 herds. Lifetime productivity was very low, with 1970-72 cohorts rearing 3.3 calves over 4.7 years at a rate of 57.5% calves per year, and 1973-87 cohorts rearing 3.1 calves over 4.9 years at a rate of 45.0% calves per year. Total weaner weights reared up to 10 years of age were 578 kg for 1970-72 cohorts and 315 kg for 1973-87 cohorts. However, variability between individual cows was high, indicating scope for selection based on productivity, provided that better performing cows can be identified from predictors early in life.

The birth weights and weaning weights of Bos indicus cross calves from 4 inter se mated herd groups in a dry tropical environment were studied. The calving season commenced in late October, about 2 weeks before the start of the pasture-growing season. Second and subsequent generations of 1/2 Brahman and 1/2 Sahiwal crosses and first backcross, and later generations of 3/4 Brahman and 3/4 Sahiwal crosses, were represented. The Bos taurus component of the crosses was primarily Beef Shorthorn. In general, Brahman crosses were heavier at birth and grew faster to weaning than Sahiwal crosses (P

Postweaning growth to slaughter at 42 months of age in males and to initial mating at 27 months of age in females was studied in 4 inter se mated Bos indicus crosses in a dry tropical environment. Six-monthly growth periods from weaning (at about 6 months of age) generally coincided with wet and dry seasons. The cattle represented were second and subsequent generations of 112 Brahman and 112 Sahiwal crosses and first backcross and later generations of 314 Brahman and 314 Sahiwal crosses, The Bos taurus component of the crosses was primarily Beef Shorthorn. Annual growth averaged 300 g/day, with annual gain ranging from 60 to 180 kg. Average growth rates were about 50 g/day in the dry season (-352 to +374 g/day) and 500 g/day in the wet season (221-830 g/day). Postweaning growth of Brahman crosses was about 4% higher than Sahiwal crosses, with most of this advantage expressed in wet seasons. Sahiwal crosses were earlier maturing than Brahman crosses. Wet season growth was higher in 314 crosses than in 1/2 crosses, which probably reflected significant environmental stress in this period. Higher growth of 3/4 crosses tended to be maintained during dry seasons. Calves born late in a wet season grew more rapidly in dry seasons than early-born calves, so that liveweight differences which were apparent at weaning were reduced by one-third at 24 months of age. The difference between liveweights of weaners with young dams and those with mature dams was also reduced from 12-18 kg to 5-6 kg by 24 months. Dressing percentages of 3/4 cross steers at slaughter were 0.6 units higher than in half crosses, with no difference between Brahman and Sahiwal crosses. Sarcomere lengths, Warner-Bratzler shear force values, and Instron compression values together showed that M. longissimus dorsi muscle samples from 1/2 Brahman steers were the most tender of the breed crosses studied. Samples from Sahiwal cross and 3/4 Brahman steers appeared most affected by connective tissue toughness. Those from 3/4 Sahiwals appeared most affected by meat processing factors, causing them to be the least tender.

Factors influencing the conception rates of 1332 Bos indicus cross maiden heifers in the dry tropics of North Queensland were studied between 1973 and 1986. The heifers, which were 112 and 314 Bos indicus (Brahman or Sahiwal) crosses with Bos taurus, were mated at 24-27 months of age over a 3-month period commencing in mid to late January. The effects of liveweights and growth rates on conception rate were initially assessed in separate models which always included cohort (year of branding group) as an additional factor. Cohort and liveweight at weaning, 18 months of age or the start of mating significantly (P

Three drafts of Brahman cross calves (phenotypically half to three-quarters Bos indicus) were either early weaned (EW) in April (mean age 5 months) or late weaned (LW) in July (mean age of 8 months). Their postweaning performance on native pastures in the dry tropics of North Queensland was monitored through to 2.5 years of age for females and 3.5 years for males. At late weaning, LW calves of both sexes were significantly (P

The female reproductive rates and liveweight performance of F2 et seq. generations of 1/2 Brahman (1/2 B), 1/2 Sahiwal (1/2 Sah), 3/4 Brahman (3/4 B) and 3/4 Sahiwal (3/4 Sah) were evaluated in the dry tropics of northern Queensland from 1978 to 1986. The balance of the breed composition was predominantly Shorthorn. A preliminary comparative analysis of F2 and F3 data showed no differences between the filial generations and data were subsequently pooled. Crossbreed differences between groups had a small effect on pregnancy rate and were not a major determinant of fertility compared with age and year effects. Any crossbreed differences were counteracted by inconsistent cross x year effects. For mature cows, 3/4 Sah had significantly (P

A sample of 19 male and 19 female 5th graders from a private school were tested on the 1949 WISC and the 1974 revised edition (WISC-R). Tests were administered in a partially counterbalanced order. Correlation coefficients for Verbal, Performance and Full Scale IQs were all very high as expected. On average, students scored 9.6 points higher on the WISC Verbal Scale and 8.4 points higher on the Performance Scale. Results for this small sample suggest the need for more frequent restandardization.

Bos indicus-crossbred calves exposed to natural Babesia bovis infection in wet and dry tropical environments in northern Queensland were tested for antibodies using the indirect haemagglutination (IHA) test. There was evidence of maternal antibodies suggesting endemicity of B. bovis in the 2 environments. Within one year 35.3 to 94.6% of the calves had acquired B. bovis infection. The highest titres and most rapid conversion rates were observed just after the wet season when the tick population was at its peak. Clinical disease was not observed. A third group of Bos indicus-cross cattle of varying ages in a dry tropical environment of north Queensland was examined for antibodies against B. bovis and Anaplasma marginale using the IHA and complement fixation (CF) tests, respectively. B. bovis and A. marginale antibodies were detected on the farm but clinical disease did not occur.

The Adjective Check List (ACL) and a self-rating schedule (SRS) made up of Murray's needs taken from the ACL manual were administered to 27 graduate students in psychology on two separate occasions. Test-retest reliabilities were low for both tests, SRS reliabilities being appreciably lower than those for the ACL. Correlations between these two measures of self-description were also low and varied considerably from one testing to the next. Correcting the average cross-correlations for unreliability in the two scales still indicated that slightly less than half of their reliable variance was held in common. Reasons for the poor reliabilities and the poor cross-correlations were discussed and avenues for further research suggested.

SUMMARY The roles of helminths and coccidia in post-weaning diarrhoea in beef calves in the dry tropics were investigated. Diarrhoea occurred approximately one month after weaning in both anthelmintic treated and untreated calves. The highest numbers of coccidial oocysts were seen 29 days after weaning and 3 necropsies confirmed Eimeria zuernii coccidiosis. In the absence of wet overcrowded conditions, disease may have been precipitated by environmental interactions leading to suppression of host immunity. Other Eimeria identified were E. bukidnonensis, E. wyomingensis, E. bovis, E. auburnensis, E. cylindrica, E. ellipsoidalis and E. subspherica. The last 5 species are believed not to have been previously documented in Australia. The presence of E. canadensis was strongly suspected.

SUMMARY Five experiments with Leptospira interrogans serovar hardjo vaccine were carried out over a 6-year period in pregnant Brahman-cross and Sahiwal-cross cows in the dry tropics of northern Queensland. The numbers ranged from 127 breeders aged 2 to 5 years in 1972 to 344 breeders aged 2 to 9 years in 1977. Half of the cows were vaccinated twice in midpregnancy except for 1977, when they were vaccinated once. In 1975–1977 inclusive, half of the heifers were given an additional dose of vaccine at commencement of mating. Vaccination caused a significant (P

Post-weaning Eimeria zuernii coccidiosis in beef calves was treated prophylactically with monensin from intra-ruminal continuous release devices. The evaluation of four treatments during three consecutive years also allowed observations on the epidemiology of this disease to be made. Monensin was an effective prophylactic and the intra-ruminal devices were a convenient method of continuous administration over a one to two month period. The three years of the trial included two characteristically very dry and one unusually wet weaning period. Coccidiosis was more severe in the dry years suggesting that oocyst challenge was less important than the immunodepressive effect of weaning and dietary stress in precipitating disease. Severe disease also occurred in calves subsequent to elimination of oocyst shedding by monensin during the initial treatment trial. The occurrence of disease in conditions inimical to oocyst survival and development and after treatment suggested a role for arrested endogenous stages.

The prevalence, stages and causes of foetal and calf wastage were determined in Brahman (1/2 B, 3/4 B) and Sahiwal (1/2 San, 3/4 Sah) and high grade Sahiwal (HGSah) genotypes over a 12-year period. The mean total loss from pregnancy being first diagnosed to weaning was 13.5% (range 9.4 to 19.0%) and was not influenced by cow age. Across all age groups total losses were significantly lower in 1/2 B (11.8%) and 3/4 B (11.7%) than in 1/2 Sah (16.3%) and 3/4 Sah (19.4%) which were in turn significantly lower than in HG Sah (26.5%). Mean prenatal, perinatal and postnatal losses were 3.5%, 4.4% and 5.6%, respectively. For prenatal losses, 42.4% occurred in early-, 34.8% in mid- and 23.0% in late gestation, the prevalence being influenced only by year effects. Perinatal losses were lowest in 3/4 B (2.9%) and highest in 3/4 Sah (8.3%) with other genotypes intermediate. Postnatal losses were lowest in 1/2 B (4.1 %) and 3/4 B (5.0%), intermediate for 1/2 Sah (7.2%) and 3/4 Sah (6.2%) and highest in HG Sah (15.5%). In Brahmans, important causes of perinatal and postnatal losses were from unknown causes, and in Sahiwals from bottle teats, unknown causes and factors influenced by the cow. Bottle teats were mostly in cows older than 2 years with the majority being in Sahiwals. A high proportion (44%) of the postnatal losses occurred by 14 days after birth.