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Context Stress responses in chickens are commonly assessed from measurements of corticosterone in blood, but there is an increasing research effort to develop non-blood means of assessing the activity of the hypothalamo–pituitary (HPA) axis. It is common to measure corticosterone in the eggs and faeces. Aims We extended previous work by undertaking a study of caged laying hens comparing basal concentrations of corticosterone in plasma, faeces, egg albumen and egg yolk on a between-cage basis. We tested the hypothesis that there are positive relationships between corticosterone in plasma and corticosterone in each of the other matrices. Methods Blood samples were collected from each bird at a single point in time. In Experiment 1, these comparisons (between plasma concentrations of corticosterone on Day 1 and egg albumen, egg yolk and faecal concentrations of corticosterone on Days 1, 3 and 4 of the study) were made for hens of two ages under basal conditions, whereas, in Experiment 2, the comparisons (between plasma concentrations of corticosterone on Day 3 and egg albumen, egg yolk and faecal concentrations of corticosterone on Days 1 and 2 of the study) were made for hens housed at different space allowances with and without access to a nest box. The birds without a nest box had not had experience with a nest box prior to sampling. Key results There was a statistically significant (P = 0.012), but limited, positive relationship between plasma and egg albumen concentrations of corticosterone under basal conditions in Experiment 2. There were no other statistically significant (P > 0.05) relationships in either experiment. These results suggest that measures of corticosterone in the albumen, yolk and faeces of laying hens are unlikely to be robust predictors of basal concentrations of corticosterone in the blood. Conclusions Although there was some indication that concentrations of corticosterone in albumen may be related to concentrations in blood under basal conditions, based on all the results, this suggestion is made cautiously. Implications More comprehensive research is required to establish if measures of corticosterone in egg components and faeces are related to chronic basal activity of the hypothalamo–pituitary axis in laying hens. There is also a need to understand the impact of corticosterone on production, reproduction and welfare in hens from measures in both blood and non-blood matrices.

Current research on factors affecting the welfare of dairy calves is predominantly based on indoor, year-round calving systems. Calf rearing in these systems differs from that in more seasonal, pasture-based dairy production, meaning that risks to the welfare of dairy calves may not always be comparable between the two systems. The aim of this review was to consolidate the scientific literature relating to calf welfare in pasture-based dairy systems from birth until weaning, allowing for (1) the identification of current and emerging risks to calf welfare and (2) the formation of recommendations to mitigate these risks. Many of the risks to calf welfare discussed in this review are not exclusive to pasture-based dairies. This includes a global trend for increasing perinatal mortalities, a significant number of calves failing to achieve effective passive transfer of immunity, the low uptake of best practice pain relief when calves are disbudded, and the feeding of restricted milk volumes. In addition to these persisting welfare risks, two factors discussed in this review pose an immediate threat to the social license of dairy farming; the separation of cow and calf soon after birth and the management of surplus calves (i.e. calves not needed by the dairy industry). Several recommendations are made to improve the uptake of best-practice calf rearing and progress the development of alternative pasture-based rearing systems that accommodate changing community expectations. These include communication strategies that strengthen farmer beliefs regarding the welfare and productivity benefits achieved by best practice calf rearing and challenge beliefs regarding the associated costs. Farmers should also be encouraged to benchmark their rearing practices through improved record keeping of key rearing inputs and outcomes. Biological research is needed to advise the development of new calf rearing recommendations and the evolution of existing recommendations. Research priorities identified by this review include the effects of dystocia on the neonate and strategies to mitigate these effects, relationships between features of pen design and calf health and welfare, feasibility of dam rearing in large pasture-based dairy systems, and strategies that increase the value of the surplus calf.

Context Manipulation of milk composition in lactating ewes represents an important mechanism by which sheep breeders can improve profits through increased milk prices for cheese making and higher lamb growth rates. To this end, melatonin implantation may affect milk composition by alleviating reproductive seasonality and augmenting insulin like growth factor-1 (IGF-1). Aims This research aimed to evaluate the effects of melatonin administration on hormone levels and milk composition, and to determine its potential to manipulate milk composition of lactating Barki ewes. Methods Fifty lactating Barki ewes were divided into two groups of 25. One group received 18 mg melatonin in a single implant at 40 days after delivery, and the other group served as an untreated control. Over the following 8 weeks, milk components (fat, protein, lactose and total solids percentages), milk energy value, and blood serum hormones including IGF-1 were measured. Key results Melatonin implantation increased (P

Context In extensive grazing sheep systems, pregnant ewes undergo periods of undernutrition because gestation coincides with winter when natural pasture is of lowest quantity and poorest quality. The lamb’s weight and thermoregulatory capacity, and the ewe–lamb bond at birth, may be compromised. Maternal melatonin treatment during gestation may reverse these effects. Aim The aim was to determine the effects of melatonin treatment of single-lambing, undernourished ewes during the last third of gestation on lamb birthweights and body temperatures, and on ewe–lamb interactive behaviour after birth. Methods At Day 100 of gestation, 39 single-bearing ewes received a subcutaneous melatonin implant, and 54 ewes served as controls with no implant. Throughout gestation, the ewes remained under extensive conditions grazing on natural pasture. Measurements were made of lamb birthweight, body temperatures (surface temperature by infrared thermography and rectal temperature), and ewe–lamb behaviours during a handling test at 6–17 h after lambing. Key results There was no effect of melatonin treatment on lamb birthweight or rectal temperature, or on ewe–lamb interaction behaviours. Hip minimum surface temperature was greater in lambs from melatonin-treated ewes than lambs from control ewes (21.2°C ± 0.9°C vs 18.8°C ± 0.8°C; P = 0.05), and there was a similar trend for hip mean surface temperature (24.6°C ± 0.9°C vs 22.3°C ± 0.7°C; P = 0.06). Rump surface temperatures were greater in male than female lambs: maximum (27.9°C ± 1.2°C vs 22.9°C ± 1.2°C; P = 0.01), minimum (22.2°C ± 1.5°C vs 16.7°C ± 1.5°C; P = 0.02) and mean (25.4°C ± 1.3°C vs 20.5°C ± 1.3°C; P = 0.02). Conclusion Melatonin treatment during the last third of ewe pregnancy slightly enhanced the surface temperature of lambs at birth but did not influence ewe–lamb interaction behaviour after birth (i.e. after establishment of the ewe–lamb bond). Implications Further study in more depth is warranted into the possible effects of maternal supplementation with commercial melatonin implants on lamb development, thermoregulatory capacity, behaviour and survival rates in extensive grazing systems, including the effect on ewe–lamb behaviours immediately after birth for both singletons and twins.

Context The use of buserelin, a gonadotropin-releasing hormone (GnRH) agonist, can improve semen quality. Nevertheless, the appropriate dosage, and frequency and time of application, remain to be established owing to the subsequent negative feedback on endogenous production of testosterone described so far. Aims This study aimed to propose a new buserelin application protocol for sperm improvement in Santa Inês rams. Methods Fifteen Santa Inês rams were divided into two experimental groups: the first group (n = 8) received 2.5 μg buserelin acetate; and the second group (n = 7) received saline solution. Treatments were applied for 21 days at intervals of 6 h, totalling four hormonal or saline applications per day. In all animals, macroscopic and microscopic seminal characteristics and freezability, plasma testosterone, pixels of testicular parenchyma, and biometric analysis of testicular and accessory sex glands by ultrasound were evaluated throughout the period of hormonal application and for a further 7 days. Key results Rams receiving buserelin showed a peak of testosterone after the first week (Day 7) of application, with a drop in values at Day 14, followed by negative feedback at Day 21 and return to basal concentrations at Day 28. They also showed improvement of kinetics parameters such as straight line velocity (μm/s: +buserelin 51.5 ± 1.5 > control 46.6 ± 1.6) and linearity coefficient (%: +buserelin 53.5 ± 1.8 > control 47.5 ± 1.9). Ultrasound parameters, pixels of testicular parenchyma, and freezability were not affected by treatment. Conclusions The administration of buserelin was able to improve some sperm kinetics parameters of Santa Inês rams. Implications Low doses of this GnRH analogue can be used; however, further adjustments to the hormonal protocol are needed to obtain an effective improvement in sperm quality.