Influence of nonenzymatically browned soybeans on ruminal fermentation and lactational performance of dairy cows

A comparison of the effect of soybeans roasted at different temperatures versus calcium salts of fatty acids on performance and milk fatty acid composition of mid-lactation Holstein cows

To evaluate the effect of soybeans roasted at different temperatures on milk yield and milk fatty acid composition, 8 (4 multiparous and 4 primiparous) mid-lactation Holstein cows (42.9±3 kg/d of milk) were assigned to a replicated 4×4 Latin square design. The control diet (CON) contained lignosulfonate-treated soybean meal (as a source of rumen-undegradable protein) and calcium salts of fatty acids (Ca-FA, as a source of energy). Diets 2, 3, and 4 contained ground soybeans roasted at 115, 130, or 145°C, respectively (as the source of protein and energy). Dry matter intake (DMI) tended to be greater for CON compared with the roasted soybean diets (24.6 vs. 23.3 kg/d). Apparent total-tract digestibilities of dry matter, organic matter, and crude protein were not different among the treatments. Actual and 3.5% fat-corrected milk yield were greater for CON than for the roasted soybean diets. Milk fat was higher for soybeans roasted at 130°C than for those roasted at either 115 or 145°C. No differences were observed between the CON and the roasted soybean diets, or among roasting temperatures, on feed efficiency and nitrogen concentrations in rumen, milk, and plasma. Milk from cows fed roasted soybeans had more long-chain fatty acids and fewer medium-chain fatty acids than milk from cows fed Ca-FA. Compared with milk from cows fed the CON diet, total milk fat contents of conjugated linoleic acid, cis-9,trans-11 conjugated linoleic acid, cis-C18:2, cis-C18:3, and C22:0 were higher for cows fed the roasted soybean diets. Polyunsaturated fatty acids and total unsaturated fatty acids were greater in milk from cows fed roasted soybean diets than in milk from cows fed CON. Concentrations of C16:0 and saturated fatty acids in milk fat were greater for CON than for the roasted soybean diets. Cows fed roasted soybean diets had lower atherogenic and thrombogenic indices than cows fed CON. Milk fatty acid composition did not differ among different roasting temperatures. In summary, results showed that cows fed CON had higher DMI and milk yield than cows fed roasted soybean diets. Among different roasting temperatures (115, 130, and 145°C), soybeans roasted at 115°C led to higher milk production and lower DMI. Cows fed roasted soybeans, regardless of the roasting temperature, had more unsaturated fatty acids in milk. Using roasted soybeans in dairy cow rations could, therefore, improve the health indices of milk for human nutrition.

Effect of Grazing and Fat Supplementation on Production and Reproduction of Holstein Cows

The objective of this trial was to investigate the effects of feeding a soybean oil refining by-product (SORB), made up mainly of sodium salts of long-chain fatty acids, on reproductive performance and productivity of 36 early lactation Holstein cows managed in a free-stall barn or on annual rye-ryegrass pasture. In this 2 x 2 factorial arrangement of treatments, cows consumed 0 or 0.5 kg/d of SORB as part of a total mixed ration for barn cows or as part of a grain supplement fed to cows on intensively, rotationally stocked pasture. Blood was sampled 3 times weekly and plasma was measured for progesterone to assess ovarian activity. Estrus activity was recorded using the HeatWatch estrus detection system. Although average 14-wk milk production (37.2 kg/d) was not different among treatments, barn cows had more persistent lactations than did grazing cows. Cows housed in the barn lost less body weight and returned to initial body weight sooner and had lower mean concentrations of plasma nonesterified fatty acids (464 vs. 261 mEq/L) than those managed on pasture. The milk fat of cows on pasture contained greater proportions of conjugated linoleic acid and linolenic acid but a corresponding 0.22 percentage unit decrease in milk fat concentration (3.39 vs. 3.16%). Cows managed on pasture had greater peak concentrations of plasma progesterone during the first estrous cycle. Cows managed on pasture and fed SORB had the greatest accumulation of plasma progesterone over the 14 wk of the study (SORB x housing interaction). These cows experienced the most mounts during their first estrus (9.3) and pregnancy rate was also greatest for this treatment (62.5%). Feeding SORB did not affect production of milk, fat, or protein. Loss of body condition was less in cows fed SORB. Ruminal fluid concentration of propionate increased and ruminal pH decreased in cows fed SORB. A lower proportion of fatty acids less than 18 carbons in length was found in the milk fat of cows fed SORB, thus indicating lower de novo synthesis of fatty acids. Higher proportions of C18:2n-6 and conjugated C18:2 were found in the milk fat of cows fed SORB. Based on concentrations of plasma progesterone, cows fed SORB experienced their first ovulation earlier (26.7 vs. 42.4 d postpartum) than did cows not supplemented with SORB. Neither housing system nor SORB supplementation influenced detection of first estrus (50.5 d) or the mean length of each estrus period (447 min).

Raised dietary n-6 polyunsaturated fatty acid intake increases 2-series prostaglandin production during labour in the ewe

Preterm labour is the major cause of perinatal morbidity and mortality in humans. The incidence is around 10% and the causes are often unknown. Consumption of dietary n-6 polyunsaturated fatty acids (PUFAs) in western societies is increasing. These are metabolized to arachidonic acid, the precursor for 2-series prostaglandins (PGs), major signalling molecules during labour. This study investigated the effect of dietary supplementation with linoleic acid (LA, 18: 2, n-6) on parturition. Ewes were fed a control or LA-supplemented diet from 100 days gestation. Labour was induced using a standardized glucocorticoid challenge (dexamethasone, Dex) to the fetus, starting on day 139. Electromyographic (EMG) activity and fetal and maternal circulating PG concentrations were monitored. One third of LA-fed ewes delivered early (pre-Dex) although basal uterine EMG activity preceding Dex was higher in control ewes (P < 0.05). A steep increase in EMG activity occurred 18-38 h after the start of Dex infusion. Twice basal EMG activity (defined as established labour) occurred on average 7 h earlier in the LA-supplemented ewes (P < 0.05). The basal concentrations of maternal and fetal PGFM and fetal PGE(2) were approximately doubled in LA-supplemented ewes before the start of Dex infusion (P < 0.01). The rise in fetal PGE(2) and maternal oestradiol concentrations post-Dex occurred earlier in the LA-supplemented ewes. All PG measurements remained significantly higher in the LA-supplemented ewes during labour onset. This study suggests that consumption of a high LA diet in late pregnancy can enhance placental PG production and may thus increase the risk of preterm labour.

The effect of dietary supplementation with linoleic acid to late gestation ewes on the fatty acid composition of maternal and fetal plasma and tissues and the synthetic capacity of the placenta for 2-series prostaglandins

Linoleic acid (18:2n-6) is metabolised to arachidonic acid (20:4n-6), the precursor for 2-series prostaglandins (PGs). Increased consumption of 18:2n-6 during pregnancy may thus modify PG synthesis during labour. We have investigated whether increased 18:2n-6 composition during gestation altered the fatty acid consumption and PG synthesis of maternal and fetal tissues in the sheep. Ewes were fed a control diet or a diet providing 40% more 18:2n-6 from 96 days gestation. Half of each group received dexamethasone on day 136 to up-regulate the PG synthetic pathways promoting parturition. Maternal and fetal tissues were collected at 138 days. The 18:2n-6 diet significantly increased the 20:4n-6 content of maternal plasma, fetal plasma and allantochorion (51-81%) phosphatidylcholine, and fetal liver (40%) and maternal caruncular endometrium (57%) phosphatidylethanolamine. Increased 18:2n-6 intake increased production of PGF(2alpha) and PGE(2) in all placental tissues (maternal caruncular and intercaruncular endometrium and fetal allantochorion) by 23-98%, whereas dexamethasone increased it by 32-142%. This suggests that consumption of an 18:2n-6-enriched diet in late pregnancy enhanced placental PG production by increasing the supply of 20:4n-6. Variations in the extent to which the diet altered the polyunsaturated fatty acid (PUFA) content of the different tissues indicated complex interactions between nutrient availability and metabolic adaptation.

Digestion, milk production, milk composition, and blood composition of dairy cows fed whole flaxseed

A total of 90 lactating Holstein cows averaging 628 kg (SE = 8) of body weight (BW) were allotted at calving to 30 groups of three cows blocked for similar calving dates to determine the effects of feeding whole untreated flaxseed on milk production and composition, fatty acid composition of blood and milk, and digestibility, and to determine whether flaxseed could substitute for other sources of fat such as Megalac and micronized soybeans. Cows were fed a total mixed diet based on grass and corn silage and fat supplements for ad libitum intake. The experiment was carried out from calving up to wk 16 of lactation. Cows within each block were assigned to one of the three isonitrogenous, isoenergetic, and isolipidic supplements based on either whole flaxseed (FLA), Megalac (MEG), or micronized soybeans (SOY). Intake of dry matter and change in BW were similar among diets. Cows fed FLA had greater milk yield than those fed MEG (35.7 vs. 33.5 kg/d) and there was no difference between cows fed FLA and those fed SOY (34.4 kg/d). Fat percentage was higher in the milk of cows fed MEG (4.14%) than in the milk of those fed FLA (3.81%) or SOY (3.70%), but milk protein percentage was higher for cows fed FLA (2.98%) than for those fed MEG (2.86%) and SOY (2.87%). Digestibilities of acid detergent fiber, neutral detergent fiber, and ether extract were lower for cows fed FLA than for those fed SOY and MEG. Retention of N was similar among diets. Feeding FLA resulted in the lowest omega-6-to-omega-3-fatty-acids ratio, which would improve the nutritive value of milk from a human health point of view. The data suggest that micronized soybeans and Megalac can be completely substituted by whole untreated flaxseed as the fat source in the diet of early lactating cows without any adverse effect on production and that flaxseed increased milk protein percentage and its omega-6-to-omega-3-fatty-acids ratio.