Golden hamster females have the shortest known gestation period among placental mammals, and at the same time raise very large litters of up to 16 offspring, which are born in a naked and blind state and are only able to pick up food from days 12 to 14 onwards. We quantified energy metabolism and milk production in female golden hamsters raising offspring under cold (8°C), normal (22°C) and hot (30°C) ambient temperature conditions. We monitored energy intake, subcutaneous body temperature, daily energy expenditure, litter size and pup masses over the course of lactation. Our results show that, in line with the concept of heat dissipation limitation, female golden hamsters had the largest energy intake under the coldest conditions and a significantly lower intake at 30°C (partial for influence of ambient temperature: F 2,403=5.6; P=0.004). Metabolisable energy intake as well as milk energy output showed the same pattern and were significantly different between the temperatures (partial for milk energy production: F 1,40=86.4; P<0.0001), with consistently higher subcutaneous temperatures in the reproductive females (F 1,813=36.77; P<0.0001) compared with baseline females. These data suggest that raising offspring in golden hamsters comes at the cost of producing large amounts of body heat up to a level constraining energy intake, similar to that observed in some laboratory mice. Notably, we observed that females seemed to adjust litter size according to their milk production, with the smallest litters (3.4±0.7 pups) being raised by hot-exposed mothers. Future research is needed to unravel the mechanism by which females assess their own milk production capabilities and how this may be linked to litter size at different ambient temperatures. Golden hamsters reach 8-10 times resting metabolic rate when raising offspring under cold conditions, which is compatible with the findings from laboratory mice and other rodents.

Life-cycle assessment (LCA) is the preferred methodology to assess carbon footprint per unit of milk. The objective of this case study was to apply an LCA method to compare carbon footprints of high-performance confinement and grass-based dairy farms. Physical performance data from research herds were used to quantify carbon footprints of a high-performance Irish grass-based dairy system and a top-performing United Kingdom (UK) confinement dairy system. For the US confinement dairy system, data from the top 5% of herds of a national database were used. Life-cycle assessment was applied using the same dairy farm greenhouse gas (GHG) model for all dairy systems. The model estimated all on- and off-farm GHG sources associated with dairy production until milk is sold from the farm in kilograms of carbon dioxide equivalents (CO2-eq) and allocated emissions between milk and meat. The carbon footprint of milk was calculated by expressing GHG emissions attributed to milk per tonne of energy-corrected milk (ECM). The comparison showed that when GHG emissions were only attributed to milk, the carbon footprint of milk from the Irish grass-based system (837 kg of CO2-eq/t of ECM) was 5% lower than the UK confinement system (884 kg of CO2-eq/t of ECM) and 7% lower than the US confinement system (898 kg of CO2-eq/t of ECM). However, without grassland carbon sequestration, the grass-based and confinement dairy systems had similar carbon footprints per tonne of ECM. Emission algorithms and allocation of GHG emissions between milk and meat also affected the relative difference and order of dairy system carbon footprints. For instance, depending on the method chosen to allocate emissions between milk and meat, the relative difference between the carbon footprints of grass-based and confinement dairy systems varied by 3 to 22%. This indicates that further harmonization of several aspects of the LCA methodology is required to compare carbon footprints of contrasting dairy systems. In comparison to recent reports that assess the carbon footprint of milk from average Irish, UK, and US dairy systems, this case study indicates that top-performing herds of the respective nations have carbon footprints 27 to 32% lower than average dairy systems. Although differences between studies are partly explained by methodological inconsistency, the comparison suggests that potential exists to reduce the carbon footprint of milk in each of the nations by implementing practices that improve productivity.

Ankyloglossia (tongue tie) is a well-recognized cause of breastfeeding difficulties and, if untreated, can cause maternal nipple pain and trauma, ineffective feeding, and poor infant weight gain. In some cases, this condition will result in a downregulation of the maternal milk supply. Milk-production measurements (24-hour) for a breastfeeding infant with ankyloglossia revealed the ineffective feeding of the infant (78 mL/24 hours), and a low milk supply (350 mL/24 hours) was diagnosed. Appropriate management increased milk supply (1254 mL/24 hours) but not infant milk intake (190 mL/24 hours). Test weighing convincingly revealed the efficacy of frenotomy, increasing breastfeeding milk transfer from 190 to 810 mL/24 hours. Postfrenotomy, breastfeeding almost completely replaced bottle-feeding of expressed breast milk. This case study confirms that ankyloglossia may reduce maternal milk supply and that frenotomy can improve milk removal by the infant. Milk-production measurements (24-hour) provided the evidence to confirm these findings.