By Annie Williams

Mineral status and metabolic indicators effect body condition, methane emissions and lamb body weight, similar to findings previously reported in dairy cows. However, the importance of the parameters is breed specific, with a commercial breed Merinolandsheep (ML) responding more sensitively compared to Rhonsheep (RH). Thus, breed differences have a genetic effect on metabolic robustness, but the inclusion of some blood parameters, indicating mineral and metabolic status might be used favourably in sheep breeding to improve lamb body weights, body condition score and reduce methane emissions.

Mineral status can have a big impact on profitability of sheep enterprises. Profitability is dependent on maternal health, feed efficiency and performance of lambs. It is already known that optimising macro and micro mineral supply so that the physiological status of the ewe is within the reported normal range is important for fetal development during gestation and on milk production during lactation, thus having a big impact on the performance of lambs. This study aimed to develop from this and address maternal energy metabolism profiles, methane emissions, lamb body weight in two sheep breeds considering the sheep’s mineral status. Methane emissions were selected because they reflect an unused proportion of gross energy intake. In sheep enterprises feed costs, including forage, are crucial to profitability. Therefore, feed efficiency, as well as health and productivity, is of increasing importance and focus for sheep breeders. This study hypothesised that optimising maternal blood concentration of minerals and metabolic indicators pre and postpartum would deliver desired ewe BCS, reduced methane emissions and increased lamb body weight.

Traits, including methane emissions, body weight, backfat thickness and body condition score were recorded at the beginning of gestation, at lambing, three weeks postpartum and at weaning for ewes from two breeds; Merionlandsheep (ML) and Rhonsheep (RH). Traits were also recorded at weaning for lambs. Blood parameters, including calcium, sodium, potassium, phosphate, nonesterified fatty acids, betahydroxybutyrate, glutatmate dehydrogenase, selenium, copper, iron, zinc, magnesium, were also measured.

The study found that at weaning a maternal serum magnesium over 1.0 mmol/L was associated with a 13% increase in lamb body weight compared to lambs from ewes with less than 0.8 mmol/L in the ML breed. High Cu levels were favourably associated with ewe body condition score and backfat thickness in both breeds. Selenium levels over 2.4 µmol/L was associated with increased body condition score in the RH breed. Interestingly an association between zinc levels and methane were also found in the MH breed, whereby high zinc levels during lactation were associated with reduced methane emissions. A low betahydroxybutyrate, an indicator of ketosis, was associated with decreasing methane emissions in both breeds demonstrating the need to avoid sheep going into negative energy balance.

The results show the importance of minerals supply and metabolic status of ewes with regard to body condition score, methane emissions and lamb body weight, but different minerals have a different effect in the two breeds used in this study. There are also indications that energy efficiency in the production system can also be affected, which has an impact on profitability of the enterprise. Overall, ML sheep responded more sensitively to mineral and metabolic parameters indicating that breed differences have an effect on metabolic robustness. The inclusion of some parameters measured might be used in sheep breeding to improve lamb body weights, body condition score and reduce methane emissions.

Summarised from:

J. Reintke, K. Brügemann, T. Yin, H. Wagner, A. Wehrend, A. Müller, S. König,

Associations between minerals and metabolic indicators in maternal blood pre- and postpartum with ewe body condition, methane emissions, and lamb body weight development,

Animal,

Volume 15, Issue 3,

2021,

100034,

ISSN 1751-7311,

https://doi.org/10.1016/j.animal.2020.100034.

(https://www.sciencedirect.com/science/article/pii/S1751731120300343)