Zinc (Zn) is an essential mineral fundamental in many biological processes related with growth, energy balance and immunity. The aim of the present study was to analyse the effect of Zn supplementation on growth parameters in small ruminants by using a meta-analytic approach. We concluded that dietary Zn supplementation improves growth performance of small ruminants. The level of response is influenced mainly by species, production level, Zn source and dosage rate.

Single nucleotide polymorphisms (SNPs) are responsible for variations among individuals; therefore, reliable SNPs, if identified, could serve as predictive markers giving sound information about many productive/reproductive traits. Prolificacy is a complex trait in goats, and identification of high confidence SNPs linked with this trait is possible by ddRAD at low cost. Bone morphogenetic protein (BMP) genes plays a major role in reproduction, and in this study, SNPs were discovered from BMP genes, and a selected SNP was validated and could be used for further association studies.

The effects of feeding tropical legumes on the animal responses are strongly dependent on the quality of both the legume and the grass they supplement. We found that tropical legumes are more fermentable than are tropical grasses, but their fibre fraction is less degradable than that of grasses. Synergism occurred between the fibre of grasses and legumes, particularly when a good-quality legume supplemented a grass. These results can help understand and optimise strategies to successfully feed tropical legumes to ruminants.

Betaine supplementation has been reported to increase insulin-like growth factor-1 (IGF-1) secretion and may, therefore, improve growth performance of weaned piglets. The lack of knowledge on the feeding duration and effect on targeted bodyweight class (light- or normal-weight) has limited its application in weaner pigs. The present experiment found that supplementing 0.1% betaine in 0–7 days, 7–35 days or 0–35 days post-weaning did not improve blood IGF-1 concentration, growth performance or survival rate in light- or normal-weight weaners in a commercial environment. Betaine supplementation is not recommended in the weaner phase when other dietary methyl donors are sufficient.

Research involving the use of alternative mineral sources for use in animal diets is complex, but necessary to understanding animal physiological response. Our findings show that calcitic seaweed (CS) can replace calcitic limestone in piglet diets as well as being an organic calcium source. Studies involving the use of CS for piglets are limited and require further break throughs.

Australian pig producers require flexible strategies to temporarily slow growth rate and avoid the price penalty associated with over-weight and fat carcasses. Our study showed that shortening the immunocastration-to-slaughter interval from 3 to 2 weeks following the second vaccination can reduce growth rate, carcass weight and backfat thickness in group-housed male pigs slaughtered at 22 weeks of age. However, the shortened immunocastration-to-slaughter interval doubled the percentage of pigs showing sexual behaviour and increased carcass skin blemishes.

The major culling reasons and their phenotypic trend over the past two decades as well as the trend in age at culling were investigated for Australian dairy cattle data. The study revealed that the estimated age at culling for Holstein and Jersey cows has changed little over the past two decades. The major culling reasons found were infertility, mastitis, low production and ‘other reasons not reported’. Although the latter category is relatively large, we did conclude that culling due to low production has decreased over time whereas the frequency of culling for infertility and mastitis has increased. This indicates a change of the survival phenotype over time as well as over lactations, and this likely also results in a change of the underlying genetic model determining survival phenotypes.

The effects of condensed tannins in ruminant faeces on soil microbial dynamics have not been described. Our study showed that presence of condensed tannins in bovine faeces could reduce decomposition rates of soil organic matter, alter nitrogen mineralisation and change the composition of the soil microbial community. Therefore, bovine faeces from diets rich in CT may have positive environmental impacts in cattle production ecosystems.

Wool fibre diameter is one of the most important economic traits of sheep wool. In the present study, we discovered 467 differentially expressed genes between fine- and coarse-wool sheep, a large proportion of which are related to lipid metabolism and the immune system. Further study of these genes will help to elucidate mechanisms underlying wool follicle metabolism and wool fibre diameter.