Effects of flaxseed, raw soybeans and calcium salts of fatty acids on apparent total tract digestibility, energy balance and milk fatty acid profile of transition cows

Oilseeds offer some protection to the access of ruminal microorganisms and may be an alternative to calcium salts of fatty acids (FA), which are not fully inert in the ruminal environment. This study aimed to evaluate the effects of different sources of FA supplementation on apparent total tract nutrient digestibility, milk yield and composition, and energy balance (EB) of cows during the transition period and early lactation. We compared diets rich in C18:2 and C18:3 FA. Multiparous Holstein cows were randomly assigned to receive one of the four diets: control (n=11); whole flaxseed (WF, n=10), 60 and 80 g/kg (diet dry matter (DM) basis) of WF during the prepartum and postpartum periods, respectively; whole raw soybeans (WS, n=10), 120 and 160 g/kg (diet DM basis) of WS during the prepartum and postpartum periods, respectively; and calcium salts of unsaturated fatty acids (CSFA, n=11), 24 and 32 g/kg (diet DM basis) of CSFA during the prepartum and postpartum periods, respectively. Dry cows fed WF had higher DM and net energy of lactation (NEL) intake than those fed WS or CSFA. The FA supplementation did not alter DM and NDF apparent total tract digestibility, dry cows fed WF exhibited greater NDF total tract digestion than cows fed WS or CSFA. Feeding WS instead of CSFA did not alter NEL intake and total tract digestion of nutrients, but increased milk fat yield and concentration. Calculated efficiency of milk yield was not altered by diets. FA supplementation increased EB during the postpartum period. Experimental diets increased long-chain FA (saturated and unsaturated FA) in milk. In addition, cows fed WS and CSFA had higher C18:1 trans-11 FA and C18:2 cis, and lower C18:3 FA in milk than those fed WF. Furthermore, cows fed CSFA had higher C18:1 trans-11 and cis-9, trans-11 FA than cows fed WS. Although supplemental C18:2 and C18:3 FA did not influence the milk yield of cows, they positively affected EB and increased unsaturated long-chain FA in milk fat.

Biohydrogenation of dietaryn-3 PUFA and stability of ingested vitamin E in the rumen, and their effects on microbial activity in sheep

The present study investigated the susceptibility of dietaryn-3 PUFA to ruminal biohydrogenation, the stability of ingested vitamin E in the rumen and the subsequent uptake of PUFA and vitamin E into plasma. Six cannulated sheep were assigned to six diets over five 33d periods, in an incomplete 6×5 Latin square. The diets, based on dried grass, were formulated to supply 50g fatty acids/kg DM using three lipid sources: Megalac®(calcium soap of palm fatty acid distillate; Volac Ltd, Royston, Herts., UK), linseed (formaldehyde-treated; Trouw Nutrition, Northwich, Ches., UK) and linseed–fish oil (formaldehyde-treated linseed+fish oil). The diets were supplemented with 100 or 500mg α-tocopheryl acetate/kg DM. Fat source or level of vitamin E in the diet did not alter microbial activity in the rumen. Biohydrogenation of linoleic acid (18:3n-6; 85–90%), linolenic acid (18:3n-3; 88–93%), docosahexaenoic acid (22:6n-3; 91%) and EPA (20:5n-3; 92%) was extensive. Feeding formaldehyde-treated linseed elevated concentrations of 18:3n-3 in plasma, whilst 22:6n-3 and 20:5n-3 were only increased by feeding the linseed–fish oil blend. Duodenal recovery of ingested vitamin E was high (range 0·79–0·92mg/mg fed). High dietary vitamin E was associated with increased plasma α-tocopherol (2·57v.1·46μg/ml for 500 and 100mg α-tocopheryl acetate/kg DM respectively), although all concentrations were low. Plasma vitamin E levels, however, tended to decrease as the type and quantity of PUFA in the diet increased. The present study illustrates that nutritionally beneficial PUFA in both fish and linseed oils are highly susceptible to biohydrogenation in the rumen. Although α-tocopheryl acetate resisted degradation in the rumen, plasma vitamin E status remained deficient to borderline, suggesting either that uptake may have been impaired or metabolism post-absorption increased.

Digestion and metabolism of dietary fat in farm animals

Fat digestion and metabolism differ widely between animal species. In ruminants, dietary fats are hydrogenated in the rumen before intestinal absorption so that absorbed fatty acids (FA) are more saturated than dietary FA. In non-ruminants, intestinal FA digestibility depends on the level of saturation of dietary FA. Fat supplementation of the diet of cows decreases milk protein and has a variable effect on milk fat, depending on the source of dietary lipids. When encapsulated lipids are used, the linoleic acid content of milk is increased, but the organoleptic quality of milk may be altered. Supplementary lipids are incorporated into non-ruminant body fat, whereas de novo lipogenesis is reduced. There is a close relationship between the nature of dietary FA and nonruminant body FA.

Effects of chemical treatment of whole canola seed on digestion of long-chain fatty acids by steers fed high or low forage diets

The objective was to evaluate the effectiveness of alkaline H2O2 treatment of whole canola seed as a means of weakening the seed coat while simultaneously protecting long-chain unsaturated fatty acids from ruminal biohydrogenation without hindering their digestion in the lower gut. Six ruminally and duodenally cannulated beef steers were offered six isonitrogenous diets for ad libitum intake twice daily in a 6 x 6 Latin square design. Treatments were arranged as a 2 x 3 factorial with two forage percentages (70 vs. 30% of dietary DM as corn silage) and three forms of canola seed supplementation, including no canola seed or canola seed added at 10% of dietary DM as treated whole seed or as crushed seed. Canola seed contributed 5% added fat to the total diet. Treated whole canola seed was superior to crushed seed in increasing the amounts of C18:1, C18:2, and C18:3 flowing to the duodenum and the amounts digested postruminally. However, digestibilities of these long-chain fatty acids (as percentages of the amounts entering the small intestine) did not differ between diets containing canola seed as treated whole seed or crushed seed. Results suggest that chemically treated whole canola seed can be used as a means of postruminal delivery of digestible long-chain unsaturated fatty acids, especially C18:1, which contributes 62% of the total fatty acids in canola seed. Results also suggest that treated whole canola seed may be more beneficial when fed with low than with high forage diets.

Volatile fatty acid metabolism by rumen mucosa from cattle fed hay or grain

Effects of an all-grain versus an all-hay diet on metabolic activity of rumen mucosa of cattle were investigated. After diets had been fed for 3 to 4 mo, rumen papillae were collected at slaughter from the dorsal rumen sac and incubated with one of various volatile fatty acids. Rates of substrate utilization were in the order: n-butyrate greater than n-valerate approximately propionate greater than iso-butyrate approximately iso-valerate. Over-all, papillae from hay-fed steers utilized greater amounts of volatile fatty acids. Dietary treatment did not significantly affect extent of conversion of volatile fatty acids to lactate and to ketone bodies. Lactate was the major metabolite from propionate and n-valerate. Ketone body formation accounted for more than 90% of n-butyrate uptake by papillae. Ketone formation from n-valerate was restricted to beta-hydroxybutyrate while that from iso-valerate was essentially acetoacetate plus acetone. Metabolic systems in rumen mucosa of physiologically mature ruminants seem to adapt little to varying individual volatile fatty acids available for absorption in vivo.