S.K. Gulati

Incorporation of n−3 fatty acids of fish oil into tissue and serum lipids of ruminants

This study examines the biohydrogenation and utilization of the C20 and C22 polyenoic fatty acids in ruminants. Eicosapentaenoic (20∶5n−3) and docosahexaenoic (22∶6n−3) acids were not biohydrogenated to any significant extent by rumen microorganisms, whereas C18 polyenoic fatty acids were extensively hydrogenated. The feeding of protected fish oil increased the proportion of 20∶5 from 1% to 13–18% and 22∶6 from 2% to 7–9% in serum lipids and there were reductions in the proportion of stearic (18∶0) and linoleic (18∶2) acids. The proportion of 20∶5 in muscle phospholipids (PL) increased from 1.5% to 14.7% and 22∶6 from 1.0% to 4.2%; these acids were not incorporated into muscle or adipose tissue triacylglycerols (TAG). In the total PL of muscle, the incorporated 20∶5 and 22∶6 substituted primarily for oleic (18∶1) and/or linoleic (18∶2) acid, and there was no consistent change in the porportion of arachidonic (20∶4) acid.

Utilisation of fish oil in ruminants

Abstract A study was conducted to determine the transfer of eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, 22:6) from fish oil into goats’ milk. Goats were sequentially offered three diets: control (C) pellets (lucerne hay-oat grain: 60/40 w/w), C plus tuna oil protected against ruminal biohydrogenation (PTO pellets), and C plus unprotected tuna oil (UTO pellets). In supplemented diets, tuna oil constituted 3% of total dry matter (DM), and each supplement was fed for 7 days, with 12 days allowed between the two fish oil feeding periods to minimise carry-over effects. Dry matter intake, milk yield, protein and fat yield were reduced by feeding UTO, but not PTO, pellets. Goats produced ω-3 enriched milk (0.3–0.5% EPA and 1.01–1.12% DHA) when fed either supplement. The rate of transfer of dietary EPA and DHA to milk ranged from 3.5 to 7.6%. Significant transfer of EPA and DHA from tuna oil into goat milk, without deleterious effects on intake or milk yield is possible, provided that the oil supplement is substantially protected against ruminal biohydrogenation.

Protection of conjugated linoleic acids from ruminal hydrogenation and their incorporation into milk fat

In vitro incubations were used to assess the hydrogenation of conjugated linoleic acid (CLA) isomers 9-cis 11-trans and 10-trans 12-cis present in synthetically produced CLA-60. About 80‐ 90% of the unprotected CLA was hydrogenated when incubated at 388C for 24 h anaerobically with sheep rumen fluid, the main end product of hydrogenation being trans-octadecaenoic acid (C18:1). Encapsulation of the CLA in a matrix of protein provided a protection of about 70% with a 30% hydrogenation of the CLA isomers, resulting in no significant change in the trans-C18:1 but an increase in the level of stearic acid (C18:0). Feeding sheep with unprotected CLA or protected CLA increased the proportion of isomers 9-cis 11-trans and 10-trans 12-cis in abomasal digesta. The concentration of the CLA isomers leaving the abomasum and available for absorption at the small intestine was about 3.5‐4% higher for the protected CLA, confirming protection imparted by encapsulation. Feeding lactating goats with protected CLA increased the proportion of isomers 9-cis 11-trans and 10-trans 12-cis in milk fat. The total CLA levels were enhanced by about 10-fold above the control levels present in milk fat with an efficiency of transfer into milk fat of 36‐41% and 21‐30%, respectively, for the two isomers. # 2000 Published by Elsevier Science B.V.

In-vitro assessment of fat supplements for ruminants

Abstract In-vitro anaerobic incubations were used to assess the degree of metabolism or rumen inertness of different fat supplements containing either triacyglycerols and/or free fatty acids. The extent of triacylglycerol lipolysis and biohydrogenation of the unsaturated fatty acids, oleic acid (C18:1) and linoleic acid (C18:2) was monitored after 24h incubation in rumen fluid. These studies indicate that the degree of metabolism of different fat sources varies from 15 to 95%. For untreated oil, extruded oil-seed and pelleted (prilled) fat supplements the degradation values were 95, 70, and 65% respectively. The hydrogenation of calcium salts of C18 monounsaturated fatty acids when mixed with predominately C16 and C18 saturated fatty acids was 45%. The lowest degree of metabolism (

Assessing the biological effectiveness of protected lipid supplements for ruminants

Techniques are described for assessing the effectiveness with which lipids may be protected against ruminal degradation. A simple in vitro test was developed using pancreatic lipase, and this test may have application in quality control of the commercial production of protected lipid supplements, as it is applicable to supplements containing polyunsaturated or saturated lipids. All the in vitro tests overestimate the actual in vivo biological effectiveness, and this is probably due to mastication and greater microbial activity in vivo than in vitro. The poor biological response of some protected lipid supplements is most probably due to the incomplete entrapment of lipid droplets in the protein matrix.

Effect of feeding different fat supplements on the fatty acid composition of goat milk

The effect of feeding dietary fat supplements on the fatty acid composition of goat milk was examined. Inclusion of canola and soybean (8020; ww) oilseed supplement protected from ruminal hydrogenation, significantly increased the proportion of C18:1 (oleic acid), C18:2 (linoleic acid) and decreased the proportion of C16:0 (palmitic acid) and C14:0 (myristic acid), while there was a small increase in C18:0 (stearic acid). Feeding protected cotton seed significantly increased C18:2 and C18:0, but there was a reduction in C18:1 while the C16:0 was unchanged. When combinations of protected cotton seed and protected-canola soybean (8020; ww) were fed, a level of 20–25% incorporation of protected cotton seed was sufficient to inhibit the desaturase enzyme, with an increase in the proportion of C18:0. In contrast, feeding calcium salts of fatty acids, a predominantly saturated fatty acid supplement, increased C16:0 and reduced C10:0 (decanoic acid) and C14:0. Feeding fat supplements of different fatty acid compositions and varying levels of inertness in the rumen will enable significant manipulation of the fatty acid composition of milk fat.

Increased efficiency of wool growth and live weight gain in Merino sheep fed transgenic lupin seed containing sunflower albumin

The aim of this experiment was to assess, using sheep, the nutritive value of lupin seed transgenically modified to contain sunflower seed albumin. Eighty Merino wether sheep of mean live weight 32.3 kg were divided into two groups and fed 796 g dry matter (DM) day−1 of a cereal hay-based diet containing 350 g kg−1 of either the transgenic or parent (unmodified) lupin seed for 6 weeks. Measurements were made of wool growth and live weight gain. After 6 weeks, half the sheep in each group were selected for a urine and faeces balance study in which organic matter (OM), nitrogen (N) and urinary purine metabolites were measured. Blood samples were taken from all sheep at the beginning and end of treatment and analysed for amino acids and plasma metabolites. A comprehensive chemical analysis of the grains showed that there was little difference between them in terms of most nutritional components, but the transgenic lupin seed contained a 2.3-fold higher methionine concentration and 1.3-fold higher cysteine than did the parent. There were no significant differences between grains in OM digestibility, rumen microbial protein synthesis or in sacco degradability of dry matter. Sheep fed the transgenic lupin grain had an 8% higher rate of wool growth (P   0.1). Plasma urea N was lower in the sheep fed the transgenic grain than those fed the parent grain (6.5 vs 6.8 mmol l−1, P < 0.05). The results show that genetic modification of a feed grain can improve its nutritive value for ruminants. The size and nature of the responses were consistent with the transgenic lupins providing more methionine to the tissues, a first-limiting amino acid for sheep. © 2000 Society of Chemical Industry

Milk fat enriched in n-3 fatty acids

Abstract Feeding dairy cows with rumen protected n -3 fatty acids (FAs) derived from oilseeds or marine oils significantly increased the proportion of these acids in milk fat. Feeding protected canola/soybean oilseed (70/30, w/w) and soybean oilseed/linseed oil (70/30, w/w) supplements increased the proportions of C 18:3 from 0.8 to 2.49 and 0.64 to 8.45%, respectively. Feeding protected soybean oilseed/tuna oil (70/30, w/w) increased the proportions of eicosapentaenoic (C 20:5 ) and docosahexaenoic (C 22:6 ) from 0 to 0.86 and 0 to 1.41%, respectively, in milk fat. There were also increases in the proportions of linoleic (C 18:2 ) and a simultaneous reduction in the saturated FAs myristic (C 14:0 ) and palmitic, (C 16:0 ) concentration, with no significant change in the proportion of stearic acid (C 18:0 ). These changes in the fatty acid composition had pronounced effects on the thermal characteristics of milk fat with a much higher proportion of liquid fats at lower temperatures, which will improve spreadability of butter. The proportions of n -3 FAs increased in milk fat at higher supplementation rates, however, the efficiency of transfer declined. This relationship between supplementation and transfer rate will determine the optimal feeding regimes necessary to produce the desired proportions of n -3 FAs in milk and dairy products.

Effect of feeding protected cholesterol on ruminant milk fat secretion

Feeding 1–2 g/day of cholesterol protected against ruminal hydrogenation caused a 20–30% drop in the secretion of milk fat by goats and cows. The effect was observed with goats fed conventional rations or with goats and cows fed rations supplemented with protected lipids, but was not observed with cows fed conventional rations, or when unprotected cholesterol and protected β-sitosterol was fed to these animals. The results suggest that this depression in milk fat is due to a decreased uptake of plasma triacylglycerol fatty acids by the mammary gland, induced by dietary cholesterol.