Date of Award

Winter 2017

Project Type

Dissertation

Program or Major

Animal and Nutritional Sciences

Degree Name

Doctor of Philosophy

First Advisor

Dr. André Fonseca Brito

Second Advisor

Dr. Peter Erickson

Third Advisor

Dr. Joanne Curran-Celentano

Abstract

Flaxseed (Linum usitatissimum) is the richest source of the plant lignan secoisolariciresinol diglucoside (SDG), which is precursor for the synthesis of the mammalian lignans enterolactone (EL) and enterodiol (ED) by the gastrointestinal microbes in mammals. There is a great deal of interest in promoting increased intakes of lignans in humans’ diet due to their potential health benefits, especially in the prevention of cardiovascular diseases, hypercholesterolaemia, breast and prostate cancers, and osteoporosis. Consumption of milk and dairy products enriched in EL could be an excellent strategy to increase the intake of lignans by humans. The first (Chapter II) and second (Chapter III) studies presented in this dissertation aimed to evaluate strategies to improve the concentration of EL in milk of dairy cows.

In Chapter II, we evaluated the effects of replacing ground corn (GRC) with incremental amounts of liquid molasses (LM) on production, milk composition (fat, true protein, lactose, EL, urea N, fatty acids), plasma concentrations of antioxidant enzymes and urea N, and apparent total-tract digestibility of nutrients in Jersey cows fed FM. Sixteen multiparous organically-certified Jersey cows averaging (means ± standard deviation) 99 ± 41 d in milk and 462 ± 38 kg of body weight were randomly assigned to treatment sequences in a replicated 4 × 4 Latin square design with 14 d for diet adaptation and 7 d for data and sample collection. Diets were fed as total mixed rations and consisted (dry matter basis) of 52% grass-legume baleage, 8% grass hay, 8.5% soyhulls, 2.5% roasted soybean, and 15% FM. Ground corn was totally replaced by increasing amounts of LM at 0, 4, 8, or 12% of the diet dry matter. Orthogonal polynomials were used to test linear, quadratic, and cubic effects in response to LM supplementation using the MIXED procedure of SAS. Milk concentration of EL tended to respond cubically when replacing GRC by incremental amounts of LM in cows fed FM. The plasma activities of the antioxidant enzymes glutathione peroxidase and catalase did not differ, but superoxide dismutase activity tended to respond cubically with feeding increasing amounts of LM at expense of GRC. Dry matter intake and yields of milk and milk fat, true protein, and lactose decreased linearly with substituting GRC for LM. Whereas the concentrations of milk fat and milk true protein did not differ across treatments, milk lactose content decreased linearly. Feeding incremental levels of LM reduced linearly the milk concentration of urea N and the amount of N excreted in urine, and tended to decrease linearly the concentration of plasma urea N. Apparent total-tract digestibilities of dry matter, organic matter, and neutral and acid detergent fiber did not differ across treatments, while digestibility of crude protein decreased linearly. Milk fatty acids profile was substantially changed most notably by linear increases in cis-9, trans-11 18:2, cis-9, cis-12, cis-15 18:3, Σ odd-chain fatty acids, and the trans-11/trans-10 ratio, and linear decreases in cis-9 18:1 and cis-9, cis-12 18:2 when replacing GRC for incremental amounts of LM.

In Chapter III was evaluated the effects of feeding flaxseed oil or sucrose alone or in combination on production, milk composition (fat, true protein, lactose, EL, urea N) plasma concentrations of thiobarbituric acid reactive substances (TBARS) and urea N, and apparent total-tract digestibility of nutrients in Holstein cows fed FM. Sixteen multiparous (4 ruminally-cannulated) Holstein cows averaging 94 ± 37.6 d in milk and 680 ± 79.1 kg of BW at the beginning of the study were used. Cows were randomly assigned to treatment sequences in a 4 replicated 4 × 4 Latin square design. Each experimental period lasted 25 d with 18 d for diet adaptation and 7 d for data and sample collection. Treatments were fed (dry matter basis) as total-mixed rations consisting of a 60:40 forage-to-concentrate ratio and included: a negative control diet (-CTRL; 8% SBM plus 23% ground corn); 15% FM +10.7% ground corn + 5% sucrose (SUCR); 15% FM + 15.4% ground corn + 3% flaxseed oil (OIL); and 15% FM +10.2% ground corn + 5% sucrose + 3% FO (COMBO). It was observed that cows fed FM had lower dry matter intake (DMI) compared with that fed soybean meal. Within cows fed FM, the reduction in DMI was greatest in cows fed the OIL diet with no difference between SUCR and COMBO treatments. Milk yield did not differ between cows fed the -CTRL diet and those fed the SUCR and OIL diets. However, a negative associative effect was observed for milk production when FM was supplemented with sucrose and FO. The concentration and yield of milk fat decreased when FO was added to FM. No effects of treatments were observed regarding concentrations and yield of milk true protein, and concentration of milk lactose. However, lactose yield and MUN tended to decrease in the COMBO diet. Digestibility of DM and OM were lower in cows fed FM diets than in those offered the –CRTL treatment. Digestibility of ADF was greatest in –CRTL, intermediate in SUCR, and lowest in OIL and COMBO and no differences across treatments were observed for the apparent total-tract digestibilities of NDF and CP. As expected, the concentration and yield of milk EL were both greater in cows fed FM diets than those fed soybean meal. No difference in milk EL was observed when FM was supplemented with either sucrose or FO alone or their combination (COMBO diet), suggesting no synergistic effects of sucrose and FO in the conversion of SDG to EL in the rumen.

A second aim of this dissertation (Chapter IV) was to determine the pharmacokinetics of EL in newborn dairy calves fed milk replacer (MR) or EL-enriched milk. In newborn calves, suckling stimulates the reflex closure of the esophageal groove so that milk or milk replacer bypass the reticulo-rumen down to the abomasum. Thus, calves may be used as a model to make inferences about the pharmacokinetics of EL in simple-stomach mammals including humans. The objective of this study was to determine the pharmacokinetics of EL from MR or EL-enriched milk consumed by newborn Holstein calves. Twenty Holsteins calves (n = 10 males and 10 females) were used from birth to d 7 of life. The 10 calves born from multiparous cows received 4 L of colostrum using nipple bottles. Whereas, the 10 calves born from primiparous cows were fed 4 L of stored colostrum from multiparous cows when available or colostrum replacer. On d 5 of life, calves were administered 2 L of milk replacer (n = 10; Low-EL treatment: 123 nmol/L EL) or 2 L of EL-enriched milk (n = 10; High-EL treatment: 481 nmol/L EL) during the morning feeding (0700 h). Blood samples were taken from the jugular vein before (0 h) and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12, 24, and 48 h after oral administration of treatments. The area under the curve for the plasma concentration of EL was analyzed according to the trapezoidal rule between 0 and 12 h after treatment administration, and it was greater in High- (26 nmol/L × h) than Low-EL calves (4.30 nmol/L × h). Similarly, the maximum concentration of EL in plasma was greater in High- (5.06 nmol/L) vs. Low-EL calves (1.95 nmol/L). Furthermore, the time after treatment intake to reach maximum plasma concentration of EL was faster in High- (4.31 h) compared with Low-EL (4.44 h) treatment. Calves were able to absorb EL, thus indicating that EL-enriched milk can be potentially used as source of EL to pre-weaned ruminants.

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