The effect of fish oil supplementation of pregnant and lactating ewes on milk production and lamb performance

Abstract

Supplementation of pregnant ewes with long-chain n-3 polyunsaturated fatty acids (PUFA) demonstrably improves indicators of neonatal lamb vigour, potentially improving the number of lambs reared per ewe. The present study investigated the effect of supplementing ewes with fish oil and vitamin E (a-tocopherol acetate) throughout both pregnancy and lactation on the performance of lactating ewes and sucking lambs. Forty-eight ewes were supplemented with one of four concentrates containing either Megalac or fish oil plus a basal (50 mg/kg) or supranutritional (500 mg/kg) concentration of vitamin E from 6 weeks pre-partum until 4 weeks post partum in a two-by-two factorial randomised-block design. All concentrates were formulated to contain approximately 60 g/kg supplemental fatty acids. Ewes were housed, penned on sawdust and offered straw ad libitum. Blood samples were taken from ewes and lambs at intervals throughout the experiment and milk samples were obtained at 21 days into lactation. There was no notable effect of dietary vitamin E concentration upon ewe or lamb performance. Ewe dry-matter (DM) intake and yield were unaffected by dietary treatment, although ewes fed fish oil lost less weight during lactation (21.88 kg compared with 23.97 kg for Megalac-supplemented ewes; P , 0.01). Milk fat concentrations (67.3 g/kg compared with 91.8 g/kg; P , 0.01) and yields (6.65 g/h v. 9.26 g/h; P , 0.01) were reduced in ewes fed fish oil and these decreases were associated with lower litter-growth rates (0.49 g/day compared with 0.54 g/day; P , 0.05). Milk protein yield was increased by fish oil supplementation (3.82 g/h) compared with Megalac supplementation (3.28 g/h; P , 0.05); moreover, there was an interaction between fat source and vitamin E concentration in that both protein concentration and yield were significantly lower in milk from ewes fed treatment with Megalac 1 basal vitamin E (MB) compared with the other three treatments. Fish oil supplementation increased the concentrations of C 18:1 trans-, cis-9, trans-11 conjugated linoleic acid (CLA), C 20:5 (n-3) and C 22:6 (n-3) within ewe plasma, milk and lamb plasma. The mechanisms by which fish oil supplementation affects milk composition warrants further investigation.

Plasma Fatty Acid Profile of Gestating Ewes Supplemented with Fishmeal

“…The significant increase in plasma 20:5n3 and 22:6n3 in ewes offered diets containing fishmeal were a direct result of the increased dietary supply of preformed VL_n3-PUFA and in agreement with Capper et al (2007). However, our study was carried out with a limited number of experimental units.…”

“…A specific functional role of DHA had been shown in the fetus and early infant neural development, which might influence neonatal viability (Cattaneo et al, 2006;Capper et al, 2007). Docosahexaenoic acid is highly concentrated in brain tissues and selectively accumulated during later stages of fetal development and infant brain growth (Brenna and Lapillonne, 2009;Hsieh and Brenna, 2009).…”

Feeding vegetable oils to lactating ewes modifies the fatty acid profile of suckling lambs

“…Researchers (Appeddu et al, 2004;Capper et al, 2007) have reported either small or no changes in suckling lamb performance when lactating ewe diets were supplemented with calcium soaps or fish oil. Furthermore, researchers indicated that changes in suckling lamb performance are mainly related to differences in milk yield, as well as milk fat and protein levels.…”

“…However, inclusion of certain oils, especially fish oils, has been shown to reduce both milk yield and milk fat concentrations in the dam (Capper et al, 2007), which could potentially reduce suckling lamb growth rates.…”

Effects of dam breed and dietary source of n-3 polyunsaturated fatty acids on the growth and carcass characteristics of lambs sourced from hill sheep flocks

“…A significant amount of research has focused on the benefits of lipid supplementation on the PUFA content of lamb meat but its effects on animal performance and carcass composition, which are of greatest economic importance, have received little attention. Supplementing ewes with fish oil during pregnancy and lactation has been shown to improve neonatal lamb vigour (Capper et al, 2006) but depresses milk yield and fat concentration (Annett et al, 2008 and, which can reduce growth rate of their lambs (Capper et al, 2007;Annett et al, 2008). There is also evidence that PUFA supplementation can reduce dry matter intake (DMI) in sheep (Annett et al, 2008), which could further impinge on lamb growth and make these feeding strategies uneconomical.…”