Genetic relationships among yearling fertility, body composition and weight traits in tropically adapted composite cattle

Published Online: 6 April 2012 OnlinePublContext. Reproduction is an economically important trait in both males and females; however, the relationships between fertility and body composition traits are little researched, but essential to breeding programs, as they will help inform selection decisions and allow the greatest opportunity for genetic gain. Aims. Estimate genetic and phenotypic correlations between male and female yearling fertility traits and investigate their relationship with yearling body composition traits, which have an effect on the attainment of puberty. Methods. Genotype and phenotype data were obtained from a tropical composite commercial cattle population and imputed to 27 638 single nucleotide polymorphisms. A series of univariate and bivariate linear mixed models using a genomic relationship matrix were run to estimate genetic parameters, genetic and phenotypic correlations for a series of male and female fertility and body composition traits. These parameters were then compared to help understand the genetic relationships. Key results. Scrotal circumference was favourably genetically correlated with weight (0.34), fat traits (0.06–0.24), muscle (0.24) and heifer days to calving (−0.32). Heifer days to calving was favourably correlated with muscle (−0.18) but not fat traits (0.11 to 0.21). The genetic correlations between heifer days to calving and sperm morphology traits were generally unfavourable (−0.32 to 0.25). Sperm morphology traits were favourably genetically correlated with fat traits (−0.84 to 0.31) and muscle (−0.61 to 0.31) but not weight (−0.15 to 0.09). Conclusions and implications. Yearling sperm morphology traits were unfavourably correlated with heifer days to calving, indicating that they are not good candidates for indirect selection on improving female fertility in the herd. A different trend was found for yearling scrotal circumference and heifer days to calving, identifying it as a good candidate for indirect selection of heifer fertility as it is easy to measure and heritable. The genetic correlations estimated between composition traits with male and female fertility traits allow breeding programs to make an informed selection decision to optimise genetic gain across all traits.M.L. Facy, M.L. Hebart, H. Oakey, R.A. McEwin and W.S. Pitchfor

Growth, body composition and body wrinkle are favourably correlated with reproductive performance in 2-8-year-old Merino sheep

Context: Despite the increased economic importance of reproductive rate in AustralianMerinos, there have been low genetic improvements in reproductive performance over the past several decades. Genetically improving reproductive traits through direct selection is restricted by low heritability, low selection intensity directly on reproductive traits, high recording costs and lack of accurate maternal pedigrees in the majority of industry breeding programs. However, indirect selection via correlated traits may be useful as a supplement to direct selection or even on its own where reproduction records are not collected. Aims: The aims of the present study were to determine whether various production and quality traits have the potential to be used as indirect selection criteria for genetically improving lifetime reproductive rate, but also whether their selection could be detrimental to reproduction via unfavourable correlations. Methods: Reproductive traits studied included pregnancy rate (ewes scanned pregnant per ewe joined), fetal number (number of fetuses scanned per ewe joined), number of lambs born (per ewe joined), number of lambs weaned (per ewe joined) and ewe rearing ability (number of lambs weaned per fetuses scanned). Using data from the SA Selection Demonstration Flocks project (1997–2005), reproductive traits were modelled against various visual and production traits to estimate correlations. Key results: Favourable genetic correlations with reproductive traits were estimated with adult ewe bodyweight (0.37–0.50), hogget eye muscle depth (HEMD, 0.40–0.57), fat depth (HFAT, 0.27–0.48) and hogget body (HBWS) and neck wrinkle scores (–0.13 to –0.50). However, the estimates for genetic correlations with hogget eye muscle depth and fat depth were lower when bodyweight was fitted as a covariate, being 0.11–0.35 and 0.17–0.32 respectively. Genetic correlations with ewe rearing ability were generally unfavourable (except those with hogget body and neck wrinkle scores, which were –0.24 and –0.15 respectively), but were either negligible (adult ewe bodyweight, hogget eye muscle depth, fibre diameter and fleece weight) or low in magnitude(fat depth). Unfavourable genetic correlations were observed between fibre diameter and reproductive traits (0.13–0.33). Fleece weight had negligible genetic correlations with all reproductive traits studied (–0.08 to 0.10). Predictions of response to index selection using indirect criteria of one or more of yearling weight, HBWS, HEMD and HFAT measurements projected substantial genetic gains in the number of lambs weaned per ewe joined (NLW). Without reproduction records on the dams of candidates for selection, indirect selection using all four indirect criteria (yearling weight, HBWS, HEMD and HFAT) was predicted to achieve 112–168% of the genetic gains of direct selection for NLW.When all indirect and direct criteria for NLWare combined as part of index selection, even larger gains for NLW are predicted (from 164–215% of direct NLW genetic gains). Conclusions: Findings from the present study suggest that bodyweight, HEMD and HFAT and HBWS could be potentially beneficial as indirect selection criteria for lifetime reproductive rate. Selection for reduced fibre diameter is potentially detrimental to reproductive performance; however, selection for improved fleece weight is unlikely to have any effect on genetic gain for reproductive traits. Implications: Use of indirect selection for lifetime reproductive could allow for genetic gain when either used with or without the direct selection criteria of reproduction records.J. A. Chapman, M. L. Hebart, and F. D. Brie

Portraying Animal Cruelty: A Thematic Analysis of Australian News Media Reports on Penalties for Animal Cruelty

Media portrayals of animal cruelty can shape public understanding and perception of animal welfare law. Given that animal welfare law in Australia is guided partially by ‘community expectations’, the media might indirectly be influencing recent reform efforts to amend maximum penalties in Australia, through guiding and shaping public opinion. This paper reports on Australian news articles which refer to penalties for animal cruelty published between 1 June 2019 and 1 December 2019. Using the electronic database Newsbank, a total of 71 news articles were included for thematic analysis. Three contrasting themes were identified: (1) laws are not good enough; (2) laws are improving; and (3) reforms are unnecessary. We propose a penalty reform cycle to represent the relationship between themes one and two, and ‘community expectations’. The cycle is as follows: media reports on recent amendments imply that ‘laws are improving’ (theme two). Due to a range of inherent factors in the criminal justice system, harsher sentences are not handed down by the courts, resulting in media report of ‘lenient sentencing’ (theme one). Hence, the public become displeased with the penal system, forming the ‘community expectations’, which then fuel future reform efforts. Thus, the cycle continues.Rochelle Morton, Michelle L. Hebart, Rachel A. Ankeny, and Alexandra L. Whittake

Evaluating Amino Acid Profiles and Blood Gas Concentrations Between Single and Twin Merino Newborn Lambs

As sheep production standards progress, and animals are bred for high production in terms of the number and weight of lambs weaned per ewe, research has identified a difference in the physiology of single lambs compared to multiple born lambs. The current study aimed to report the baseline amino acid (AA) profiles and blood gas concentrations in newborn, Merino single and twin lambs. From 120 days of gestation, 50 single-bearing and 50 twin-bearing, naturally mated Merino ewes were monitored for signs of approaching parturition. At birth, blood samples of the progeny were collected, and birth weight, rectal temperature, and meconium score were recorded. Blood plasma samples were analysed for AA profiles and blood gas concentrations were determined using an i-Stat Alinity. Single-born lambs had a higher birth weight (5.05 kg) compared to twins (4.24 kg; p < 0.05). Birth rank also affected rectal temperature and AAs aspartic acid, isoleucine, leucine, and phenylalanine, all being lower in twins compared to singles (p < 0.05). These baseline data provide insight into the physiological differences between single and twin lambs at birth from dams where there has been no treatment or intervention imposed.Leesa-Joy Dunstan, Michelle L. Hebart, Forbes D. Brien, Sue A. McCoard, Mariana Caetan

Australia’s sustainable grazing on saline lands initiative: a national research progra

No abstract availabl

Evaluation of miRNA as biomarkers of emotional valence in pigs

The ability to assess the welfare of animals is dependent on our ability to accurately determine their emotional (affective) state, with particular emphasis being placed on the identification of positive emotions. The challenge remains that current physiological and behavioral indices are either unable to distinguish between positive and negative emotional states, or they are simply not suitable for a production environment. Therefore, the development of novel measures of animal emotion is a necessity. Here we investigated the efficacy of microRNA (miRNA) in the brain and blood as biomarkers of emotional state in the pig. Female Large White × Landrace pigs (n = 24) were selected at weaning and trained to perform a judgment bias test (JBT), before being exposed for 5 weeks to either enriched (n = 12) or barren housing (n = 12) conditions. Pigs were tested on the JBT once prior to treatment, and immediately following treatment. MiRNA and neurotransmitters were analyzed in blood and brain tissue after euthanasia. Treatment had no effect on the outcomes of the JBT. There was also no effect of treatment on miRNA expression in blood or the brain (FDR p > 0.05). However, pigs exposed to enriched housing had elevated dopamine within the striatum compared to pigs in barren housing (p = 0.02). The results imply that either (a) miRNAs are not likely to be valid biomarkers of a positive affective state, at least under the type of conditions employed in this study, or (b) that the study design used to modify affective state was not able to create differential affective states, and therefore establish the validity of miRNA as biomarkers.Laura Marsh, Mark R. Hutchinson, Clive McLaughlan, Stefan T. Musolino, Michelle L. Hebart, Robyn Terr

Divergent breeding values for fatness or residual feed intake in Angus cattle. 1. Pregnancy rates of heifers differed between fat lines and were affected by weight and fat

The pregnancy rate of heifers affects the efficiency and profitability of beef herds. Heifers extreme in rib fatness (Fat) or post-weaning residual feed intake (RFI) estimated breeding values (EBVs) were evaluated for their pregnancy rates at two locations in the southern agricultural regions of Australia (Struan and Vasse) as part of the Beef Cooperative Research Centre Maternal Productivity Project. Heifers divergent in Fat (High-Fat and Low-Fat) had differences in fat depth pre-joining at the 12/13th rib (4.4 mm vs 3.5 mm) and P8 rump site (6.1 mm vs 4.8 mm). This was associated with significant differences in pregnancy rates over a 9-week joining period (91.5% vs 83.0%) and an even larger difference when calculated over a 6-week joining period (77.3% vs 65.0%). Heifers divergent in RFI (Vasse only) also differed in rib fat (7.6 mm vs 6.4 mm) and P8 fat (11.0 vs 9.2 mm), but not significantly in pregnancy rates between the two RFI (High-RFI and Low-RFI) genotypes following a 9-week (92.4% vs 88.5%) or 6-week (81.2% vs 73.7%) joining period. The phenotypic analysis of the Fat and RFI heifers together indicated that weight and fat depth were the largest contributing factors to variation in pregnancy rates, and age and pre-joining weight gain were not significant. These phenotypic characteristics indicated that producers can manage heifers to particular weight and fat combinations to improve heifer conception rates. Associations of BREEDPLAN EBVs with heifer fertility showed that a shorter days-to-calving EBV had the biggest impact (P < 0.001) on heifer pregnancy rates and rib fat and scrotal size EBVs were close to significant (P < 0.10)