Association of plasma metabolites and hormones with the growth and composition of lambs as affected by nutrition and sire genetics

Abstract

An experiment was conducted to test 3 hypotheses regarding the variation in plasma parameters and their association with lamb growth and composition. The experiment tested whether sire genetics and available nutrition affected specific plasma traits, whether these traits were associated with growth and compositional characteristics, and whether data on plasma traits could improve the prediction of growth and carcass composition. Lambs (n = 103) produced by sires differing in estimated breeding values for growth, muscling, and fat were reared on LOW or HIGH planes of lifetime nutrition. Blood samples were collected immediately prior to weaning and before slaughter at 8 months of age. Concentrations of plasma creatinine (CRE), urea (PUN), insulin like growth factor I (IGF-I) were measured in all samples. Leptin was measured in samples from male lambs only (n = 56). HIGH nutrition increased preweaning and preslaughter IGF-I and leptin concentrations; nutritional effects on PUN and CRE were inconsistent. Lambs of the high muscle sire-type exhibited increased plasma IGF-I, reduced PUN, and an increased PUN : CRE ratio preweaning. Increased genetic potential of the sire for growth reduced PUN and increased PUN : CRE ratio. Plasma IGF-I correlated strongly with lamb growth rate (r2 = 0.49). Interaction of nutrition and sire-type for preslaughter leptin mimicked the interaction occurring for carcass fat, providing an example of selection on genotype inducing a physiological (hormonal) change and resulting in a modified phenotype. Stepwise regressions developed to predict carcass protein and fat mass from information available at weaning or at slaughter indicated that inclusion of plasma parameters in these models caused only small increases in the proportion of variance accounted for. The most significant benefit was an increase in the proportion of variance in carcass weight accounted for (from 65 to 73%) by including IGF-I and CRE as predictors compared with prediction from weaning weight alone. If slaughter data were available, then >90% of the variance in carcass fat and protein masses was explained by carcass weight alone and this was not increased by inclusion of any preslaughter plasma parameter in the model. It was concluded that while nutrition and the genetic capacity of the sire (especially for muscling) affect plasma constituents as well as lamb growth and carcass composition, the inclusion of the measured plasma traits in models to predict final carcass composition from weaning data or slaughter data is unlikely to improve the prediction sufficient to justify the additional measurement cost.

Sainfoin in the Dams’ Diet as a Source of Proanthocyanidins: Effect on the Growth, Carcass and Meat Quality of Their Suckling Lambs

“…The Sainfoin + PEG suckling lambs ingested a greater quantity of urea from their dam’s milk, but it was not reflected in their plasma concentration, which suggests that the protein metabolism could be different between groups. The plasma creatinine concentration in suckling lambs was similar between treatments, indicating a similar metabolism of muscle mass [ 29 ], so that the PAC of dams’ diet had no effect on the use of amino acids of their lambs by reducing the ruminal degradation of dietary protein [ 16 ].…”

Omega–3 Long-Chain Fatty Acids in the Heart, Kidney, Liver and Plasma Metabolite Profiles of Australian Prime Lambs Supplemented with Pelleted Canola and Flaxseed Oils

“…Knowledge of haematological metabolite concentrations is valuable in understanding the individual health status and productivity of lambs [ 23 ]. Hence, quantifying the changes in plasma metabolite concentrations in lambs due to feed supplements and genetics is essential [ 24 ], especially the plasma metabolite profiles of prime lambs supplemented with graded levels of canola and flaxseed oil. The primary objective of this study was to investigate the effects of graded levels of canola and flaxseed oil supplementation to purebred Merino and first-cross prime lambs on heart, liver and kidney fatty acid profiles, including absolute contents, and the plasma metabolites.…”

Field Pea Can Be Included in Fattening Concentrate without Deleterious Effects on the Digestibility and Performance of Lambs

“…Creatinine is the final product of the dephosphorylation of phosphocreatine to creatine in muscle and is related to the proportion of muscle mass in lambs [33]. In the current experiment, the inclusion of pea did not affect plasma creatinine in the digestibility trial, but it affected plasma concentration at slaughter; the lambs fed the concentrate with 30% pea presented a greater creatinine concentration than that of their counterparts fed concentrates with 0% and 10% pea.…”