An Evaluation of the Supplementation of Rumen-Protected Lysine and Methionine on the Lactation Performance of Fall Parturition Grazing Holstein Cows in Southern Chile.

The aim of this study was to evaluate the effect of the supplementation of rumen-protected (RP) methionine and lysine on milk yield, solids, and body weight over time on fall-calving grazing multiparous Holstein cows from Chile. Four treatment groups were studied and compared for the outcomes over time. The treatments were as follows: (i) CON: control (n = 26); (ii) RP lysine group (LYS; 20 g per cow per day; n = 26); (iii) RP methionine group (MET; 20 g per cow per day; n = 26); and (iv) LYS × MET (RP lysine and RP methionine 20 g of each amino acid per cow per day; n = 26). Data were analyzed with general linear mixed model ANOVAs for repeated measures to primarily test the main effects of each amino acid and their interactions. The supplementation of the amino acids was conducted from 2 to 70 days postpartum. Overall, milk production tended to be higher in the MET and in the LYS × MET group when compared to the control group. Furthermore, CON produced significantly less milk protein (kg) and milk fat (kg) than the LYS, MET, and LYS × MET groups. Milk urea tended to be lower during the entire study in the CON group than the rest of the groups. There was a trend for a reduction in the losses of postpartum body weight in the LYS × MET than the CON. In conclusion, RP methionine and lysine improved milk fat and protein yield in grazing multiparous cows with fall parturitions; consequently, both RP amino acids can be used as a strategy for improving grazing cows' production performance.

A daily intake of approximately 6 microg vitamin B-12 appears to saturate all the vitamin B-12-related variables in Danish postmenopausal women.

BACKGROUND: Recommended daily intakes of vitamin B-12 vary between 2 and 6 microg. OBJECTIVE: The objective was to examine the associations between vitamin B-12 intake and markers of vitamin B-12 deficiency. DESIGN: We studied 98 Danish postmenopausal women aged 41-75 y. Serum cobalamin, transcobalamin (TC) saturated with vitamin B-12 (holo-TC), TC saturation (holo-TC/total TC), methylmalonic acid (MMA), and total homocysteine (tHcy) were measured to assess vitamin B-12 status. Dietary intakes of vitamin B-12 were determined from 7-d weighed food records. Gastric pH measurement and the alkali-challenge test were performed with the use of Heidelberg radiotelemetric capsules. RESULTS: The total intake of vitamin B-12 ranged from 1.2 to 23.9 microg/d. All vitamin B-12-related variables, except gastric pH, correlated significantly with total vitamin B-12 intake. Those taking supplements (54%) had higher circulating concentrations of cobalamin and TC saturation and lower concentrations of MMA and tHcy than did those not taking supplements. All subjects were divided into quintiles according to their total vitamin B-12 intake. For all the variables analyzed, the curves appeared to level off at a daily vitamin B-12 intake of approximately 6 microg; the median (and 25th-75th percentiles) for cobalamin was 380 (270-480) pmol/L, for holo-TC was 119 (92-162) pmol/L, for MMA was 0.12 (0.14-0.17) micromol/L, and for tHcy was 9.75 (8.3-11.40) micromol/L (n = 58). CONCLUSION: A daily vitamin B-12 intake of 6 microg appeared to be sufficient to correct all the vitamin B-12-related variables measured in the postmenopausal Danish women in this study.

[Lactation--a risk factor for elevated plasma homocysteine?]. / Amning--en risikofaktor for forhøjet plasma-homocystein?

INTRODUCTION: Women have an increased need of folate in the breastfeeding period and, as a consequence, may be in risk of having a negative folate balance. Elevated total homocysteine in plasma (P-tHcy) is a sensitive marker for deficiency of folate, B6, and B12 vitamins and a risk factor for developing cardiovascular disease. We examined whether there is a difference in P-tHcy among breastfeeding mothers depending on folic acid supplement and compared these results to women from the background population. MATERIAL AND METHODS: A total of 20 breastfeeding mothers had their plasma homocysteine content and their erythrocyte folate content measured through a standard blood sampling procedure in their homes. Half of the mothers took a folic acid supplement. The background population was age-matched, non-pregnant, and non-lactating women from a previous Danish study. RESULTS: The group of breastfeeding mothers who did not take folic acid supplements had a higher prevalence of elevated P-tHcy (70%) both than the group of breastfeeding mothers who took folic acid supplements (30%) and than the background population (33%). The difference between P-tHcy in the group of breastfeeding mothers who did not take folic acid supplements and the group of breastfeeding mothers who took folic acid supplements was non-significant (p = 0.12). However, we found a statistically significant difference between the group of breastfeeding mothers who did not take folic acid supplements and the background population (p = 0.02). DISCUSSION: Our study suggests that there is a significant fraction of Danish breastfeeding mothers in negative folate balance resulting in elevated P-tHcy compared to the background population.

Effects of vitamin supplementation and hyperhomocysteinemia on atherosclerosis in apoE-deficient mice.

It has been demonstrated that hyperhomocysteinemia (HHcy) accelerates atherosclerosis in apolipoprotein E-deficient (apoE(-/-)) mice. In this study, vitamin-defined chow diets were used to induce HHcy in apoE(-/-) mice in an attempt to identify possible pathogenic pathways. Six-week-old female apoE(-/-) mice were divided into seven groups: vitamin-defined purified chow diet alone (control), or same diet supplemented with either D,L-homocysteine (upward arrow Hcy) or L-homocystine (upward arrow Hcy-Hcy), or diet high in L-methionine (upward arrow Met), or diet high in B-vitamins (upward arrow vitamin), or diets deficient in folate (downward arrow folate) or vitamin B(6) ( downward arrow B(6)). Eighteen weeks later, plasma total homocysteine (tHcy), lipids and atherosclerotic plaque burden (aortic root, aortic arch, and brachiocephalic trunk) were measured. tHcy levels were similar in the upward arrow vitamin, downward arrow folate, downward arrow B(6) and control groups (9.2-10.1 micromol/l, NS), but elevated mildly in the upward arrow Hcy-Hcy group (16.1 micromol/l) and moderately in the upward arrow Met and upward arrow Hcy groups (53.6 and 51.5 micromol/l, respectively). Mice in the latter two groups had significantly more atherosclerosis in the aortic root. Although B vitamin-supplementation failed to lower tHcy levels, mice had less atherosclerosis in the aortic arch. In summary, dietary methionine and homocysteine, but not homocystine, enhanced the development of atherosclerosis. Supplementation with B vitamins appeared to confer homocysteine-independent protection against atherosclerosis. These results suggest that (1) there may be a threshold level below which homocysteine is not atherogenic; (2) the atherogenic effect of HHcy may be mediated via an intracellular pathway; and/or (3) the anti-atherogenic effect of B vitamins in normohomocysteinemic mice is independent of tHcy levels.