Calcium-enriched goats' milk aids recovery of iron status better than calcium-enriched cows' milk, in rats with nutritional ferropenic anaemia

Ca-Fe interactions are known, but no studies are available about the effects of Ca-enriched goat or cow milk on Fe status in nutritional ferropenic anaemia (NFA). To examine this matter, control and Fe-deficient rats were fed for 14 d with goat or cow milk diets containing either normal or high Ca content (5000 or 10,000 mg/kg diet), and different indices and parameters related to iron status were measured. The apparent digestibility coefficient (ADC) and the Fe retention/intake (R/I) ratio were higher in control and anaemic rats fed goat milk diet (G diet), despite high-Ca content. Ca enrichment decreased Fe stores in liver and sternum in anaemic rats fed cow milk diet (C diet), however G diet did not modify Fe content in the organs studied in control and anaemic rats. In anaemic rats, Ca-supplementation decreased haematocrit, but platelets and serum Fe were not affected, however, in control rats platelets increased except for Ca-enriched G diet, this fact reveals that Ca-Fe interaction is minimized with G diet. Serum ferritin was always higher in rats fed G vs. C diet, both in control and anaemic rats fed either normal or Ca-enriched diets. Ca-supplementation decreased ferritin levels in control and anaemic rats fed C diet and also, though to a lesser extent, in those given the G diet. This indicates that with this G diet there is a better recovery of body Fe stores in anaemic rats, despite Ca-supplementation. In this study it is noteworthy that despite high Ca content, a goat milk diet resulted in minimal Ca-Fe interactions and did not adversely affect Fe status in rats with NFA.     

Goat milk during iron repletion improves bone turnover impaired by severe iron deficiency

The effect of goat or cow milk-based diets, with either normal Fe content or an Fe overload, on bone turnover and the mineralization process was studied in control and anemic rats during chronic Fe repletion. One hundred eighty male Wistar rats were studied during a pre-experimental period of 40 d in which they were randomly divided into 2 groups, a control group receiving the AIN-93G diet with normal Fe content (45 mg/kg of diet) and the Fe-deficient group receiving the AIN-93G diet with low Fe content (5 mg/kg of diet) for 40 d. After the pre-experimental period, the rats were fed for 10, 30, or 50 d with goat or cow milk-based diets with a normal Fe content (45 mg/kg of diet) or an Fe overload (450 mg/kg of diet). In anemic rats, goat milk with normal Fe content increased levels of the biomarker of bone formation N-terminal propeptides of type I procollagen and diminished parathyroid hormone levels after only 10 d of supplying this diet, indicating the beginning of restoration of the bone demineralization induced by the anemia, which was not observed with cow milk. After 30 d of supplying the milk-based diets with normal Fe content or an Fe overload, biomarkers of bone formation and bone resorption were not different between control and anemic rats, indicating that the bone demineralization induced by the Fe-deficiency anemia had recovered, although the process of stabilization of bone turnover began earlier in the animals fed goat milk. In addition, a higher Ca deposit was observed in femur, which positively affects bone mineralization, as well as an increase of Fe in sternum, which indicates that the hematopoietic process essentially recovered earlier on the goat milk diet compared with the cow milk diet.     

Goat milk consumption modulates liver divalent metal transporter 1 (DMT1) expression and serum hepcidin during Fe repletion in Fe-deficiency anemia

Iron deficiency is the most prevalent micronutrient deficiency worldwide. In spite of the crucial role of hepatocyte divalent metal transporter 1 (DMT1) and hepcidin in Fe metabolism, to date, no studies have directly tested the role of these proteins in liver Fe metabolism during Fe repletion after induced Fe-deficiency anemia. Therefore, the aim of the current study was to assess the effect of goat or cow milk-based diets on Fe metabolism in one of the main body storage organs, the liver, during the course of Fe repletion with goat or cow milk-based diets in anemic rats. Animals were placed on a preexperimental period of 40 d, a control group receiving a normal-Fe diet and the Fe-deficient group receiving a low-Fe diet (5 mg of Fe/kg of diet). Rats were fed for 30 d with goat or cow milk-based diets with normal Fe content (45 mg of Fe/kg of diet). The hematological parameters, serum hepcidin, hepatosomatic index, liver Fe content, and liver DMT1 expression were determined. During the recovery of the anemia with milk-based diets, the restoration of liver Fe content and hematological parameters, especially with goat milk, increased the red blood cell count, favoring the oxygen supply and weight gain. Moreover, goat milk consumption potentiates liver DMT1 expression, enhancing Fe metabolism and storage. In addition, the increase in serum hepcidin in anemic rats observed in the current study also explains and supports the higher liver Fe content after supplying goat milk, because it blocks the liberation of Fe from hepatocytes, increasing its storage in liver.     

Effect of calcium-supplemented goat or cow milk on zinc status in rats with nutritional ferropenic anaemia

The effects of goat- or cow-milk-based diets, whether normal or supplemented with calcium (5 or 10 g kg^?1 Ca, respectively), on the nutritive utilization of Zn and its deposition in organs, were evaluated in rats with and without nutritional ferropenic anaemia (NFA). The digestive and metabolic utilization of Zn in anaemic and control groups was higher for rats on the goat milk diet than those on the cow milk diet. The most noteworthy result is that Ca supplementation in the diet improved Zn metabolism in all experimental groups, but especially in anaemic rats fed the goat milk diet. This fact is reflected in the higher levels of Zn deposition found with the goat milk diet. It appears that goat milk, especially when supplemented with Ca, had beneficial effects on nutritive utilization of Zn and Zn deposition in target organs in both control rats and, especially, rats with NFA.     

Goat milk consumption protects DNA against damage induced by chronic iron overload in anaemic rats

The effect of cow or goat milk-based diets, either normal or Fe-overloaded, on DNA stability was studied in control and anaemic rats for 30 or 50 days of chronic Fe repletion. DNA damage was assessed using the alkaline comet assay. Background DNA damage in lymphocytes of peripheral blood was much lower in control and anaemic rats, given the normal or Fe-overloaded goat milk-based diet after 30 and 50 days versus cow milk-based diet. Chronic Fe-overload had no adverse effect on DNA stability in control and anaemic fed the goat milk-based diet versus the same diet with normal-Fe content at the end of the study. The quality of goat milk fat, together with the high levels of bioavailable Mg and Zn may be responsible for its protective effect on DNA of peripheral blood lymphocytes under the different experimental conditions, even during chronic Fe-overload.     

Beneficial effect of goat milk on nutritive utilization of iron and copper in malabsorption syndrome

The search for diets that improve the digestive and metabolic use of iron and copper in malabsorption syndrome led us to study goat milk for particular nutritional characteristics and compare it with cow milk, which is usually supplied. We studied the metabolism of iron and copper in transected rats (control) and in resected rats (resection of 50% of the distal small intestine). The diets used were the standard diet recommended by the American Institute of Nutrition and diets based on goat or cow milk. Intestinal resection reduced the apparent digestibility coefficient (ADC) of iron in the three diets tested. In the transected and resected rats, the ADC of iron was highest with the goat milk diet, followed by the standard diet and lowest with the cow milk diet. The ADC of copper was not affected by intestinal resection in the animals fed the goat milk diet, and was higher than that in the two groups of animals fed the other diets. Intestinal resection reduced the ADC of copper with the standard diet and the cow milk diet. When both groups of animals were fed the goat milk diet, the deposit of iron in the organs was greater than with those fed the cow milk diet and similar to that in those animals given the standard diet. The copper content in the kidneys was lower in the resected than in the transected animals, except in the case of those fed the goat milk diet, in which it was similar to that of the control (transected) rats. This study shows the beneficial effect of goat milk, with respect to cow milk, on the metabolism of iron and copper in control rats, especially those with malabsorption syndrome.     

Calcium‐enriched goat milk,in comparison with similarly enriched cow milk,favours magnesium bioavailability in rats with nutritional ferropenic anaemia

BACKGROUND: The effects of dietary consumption of goat or cow milk, normal or enriched with calcium (Ca), on magnesium (Mg) bioavailability was evaluated in rats with nutritional ferropenic anaemia. Control and iron‐deficient rats were fed for 14 days with iron‐normal diets containing either normal (5000 mg kg^?1 diet) or high (10 000 mg kg^?1 diet) Ca content. RESULTS: The results shown that the goat milk diet gave the best results for digestive and metabolic utilization of Mg, both among the anaemic and the control group, with respect to the cow milk and standard diets. The most noteworthy result of Ca enrichment on the nutritive utilization of Mg is that it is less prejudicial in this respect when supplemented via goat milk than with cow milk or the standard diet. CONCLUSION: The results demonstrate the beneficial effects of the goat milk, normal or with double Ca, on the nutritional utilization of Mg; therefore the consumption of this type of milk for people with nutritional ferropenic anaemia can be recommended. Copyright © 2007 Society of Chemical Industry     

Study of nutritive utilization of protein and magnesium in rats with resection of the distal small intestine. Beneficial effect of goat milk

The search for diets to improve the nutritive utilization of protein and magnesium in malabsorption syndrome led us to study goat milk, because of its particular nutritional characteristics, and to compare it with cow milk, which is most commonly consumed. We studied the nutritive utilization of protein and magnesium in transected rats (control) and in rats with resection of 50% of the distal small intestine. The diets used were the standard diet recommended by the American Institute of Nutrition and diets based on lyophilized goat or cow milk. The consumption of goat milk produces better protein efficiency ratio and food conversion efficiency values, particularly in rats with intestinal resection, together with a higher nutritive utilization of protein. Magnesium apparent digestibility coefficient is not modified by intestinal resection in rats fed with goat milk-based diet, on the contrary to the standard and cow milk diets. Magnesium apparent digestibility coefficient is greater for the goat milk group, which is reflected in the greater quantity of this mineral stored in bone. These results demonstrate the beneficial effect of goat milk on the nutritive utilization of protein and on magnesium bioavailability, especially in animals with resection of the distal small intestine.     

Grape marc reduces methane emissions when fed to dairy cows

Grape marc (the skins, seeds, stalk, and stems remaining after grapes have been pressed to make wine) is currently a by-product used as a feed supplement by the dairy and beef industries. Grape marc contains condensed tannins and has high concentrations of crude fat; both these substances can reduce enteric methane (CH₄) production when fed to ruminants. This experiment examined the effects of dietary supplementation with either dried, pelleted grape marc or ensiled grape marc on yield and composition of milk, enteric CH₄ emissions, and ruminal microbiota in dairy cows. Thirty-two Holstein dairy cows in late lactation were offered 1 of 3 diets: a control (CON) diet; a diet containing dried, pelleted grape marc (DGM); and a diet containing ensiled grape marc (EGM). The diet offered to cows in the CON group contained 14.0 kg of alfalfa hay dry matter (DM)/d and 4.3 kg of concentrate mix DM/d. Diets offered to cows in the DGM and EGM groups contained 9.0 kg of alfalfa hay DM/d, 4.3 kg of concentrate mix DM/d, and 5.0 kg of dried or ensiled grape marc DM/d, respectively. These diets were offered individually to cows for 18 d. Individual cow feed intake and milk yield were measured daily and milk composition measured on 4 d/wk. Individual cow CH₄ emissions were measured by the SF₆ tracer technique on 2 d at the end of the experiment. Ruminal bacterial, archaeal, fungal, and protozoan communities were quantified on the last day of the experiment. Cows offered the CON, DGM, and EGM diets, ate 95, 98, and 96%, respectively, of the DM offered. The mean milk yield of cows fed the EGM diet was 12.8 kg/cow per day and was less than that of cows fed either the CON diet (14.6 kg/cow per day) or the DGM diet (15.4 kg/cow per day). Feeding DGM and EGM diets was associated with decreased milk fat yields, lower concentrations of saturated fatty acids, and enhanced concentrations of mono- and polyunsaturated fatty acids, in particular cis-9,trans-11 linoleic acid. The mean CH₄ emissions were 470, 375, and 389 g of CH₄/cow per day for cows fed the CON, DGM, and EGM diets, respectively. Methane yields were 26.1, 20.2, and 21.5 g of CH₄/kg of DMI for cows fed the CON, DGM, and EGM diets, respectively. The ruminal bacterial and archaeal communities were altered by dietary supplementation with grape marc, but ruminal fungal and protozoan communities were not. Decreases of approximately 20% in CH₄ emissions and CH₄ yield indicate that feeding DGM and EGM could play a role in CH₄ abatement.     

The effect of formulated goats' milk on calcium bioavailability in male growing rats

BACKGROUND: There are two main proteins in milk; whey and casein. Casein contains casein phosphopeptides (CPP), which are released on digestion of the milk. These may increase calcium solubility by binding calcium in the small intestine. Thus increasing casein in the diet may help to stimulate bioavailability of calcium and increase bone density. The present study tested this hypothesis in growing male rats fed diets containing three different concentrations of casein from goat milk. RESULTS: Rats fed the diet containing no casein had significantly lower calcium absorption when compared to rats fed the diets that contained 80% and 57% of goat milk protein as casein; however, no significant difference was observed between rats fed diets with 80% and 57% casein. The varying amounts of casein had no effect on mineral uptake or retention in the femur. Biomechanical testing and mineral analysis of the femurs showed no differences between diet groups. The mechanism to explain this lack of retention remains unclear. CONCLUSION: The diets containing 80% and 57% of goat milk protein as casein delivered increased calcium absorption compared to the diet containing no casein, suggesting a minimum level of casein is needed to optimize calcium absorption from goat milk. Copyright © 2009 Society of Chemical Industry     

Mineral retention in three-week-old piglets fed goat and cow milk infant formulas

Goat milk and cow milk are commonly used in infant formula preparations and, as such, understanding the nutritional characteristics of infant formulas made from these milks is important. In this study, a goat milk infant formula was compared with an adapted (whey-enhanced) cow milk infant formula with respect to mineral absorption and deposition using the 3-wk-old piglet as a model for the 3-mo-old infant. Equal numbers of piglets (n = 8) were fed either the goat milk formula or the cow milk formula. The mineral composition of the prepared goat milk formula was higher than that of the prepared cow milk formula for most minerals, including calcium (75.1 vs. 56.7 mg/100 mL) but excluding iron, which was higher in the prepared cow milk formula (0.92 vs. 0.74 mg/100 mL). The amounts of calcium, phosphorus, and manganese absorbed by the piglets were significantly higher for the goat milk formula, whereas the amounts of zinc, iron, and magnesium absorbed were significantly higher for the cow milk formula. Apparent mineral absorption, relative to intake, was statistically higher in the cow milk formula for calcium and phosphorus, although the actual differences were very small (less than 1.3%). For copper, zinc, iron, and magnesium there was no significant difference between treatments in apparent mineral absorption, whereas for manganese, absorption was higher for the goat milk infant formula. The absolute mineral deposition was higher in piglets fed the goat milk formula for calcium, phosphorus, and manganese, whereas iron deposition was higher in the piglets fed cow milk formula. For all other minerals tested, there were no significant differences between treatments. The goat milk infant formula provided a pattern of mineral retention in the 3-wk-old piglet very similar to that of the adapted cow milk infant formula. The minor differences observed between the 2 appeared to be due to the different mineral contents of the 2 formulas.     

Digestive utilization of goat and cow milk fat in malabsorption syndrome.

We studied the effects of goat and cow milk fat on the digestive utilization of this nutrient and on some of the biochemical parameters that are related to the metabolisim of lipids, using rats with a resection of 50% of the distal small intestine and control animals (transected). The fat content in all the diets was 10% but the lipid quality was varied: the standard diet was based on olive oil, while the other two diets included fat obtained from lyophilized goat milk and cow milk, respectively. The digestive utilization of the fat was lower in the resected animals than in the transected ones for all three diets studied. In both resected and transected animals. the apparent digestibility coefficient (ADC) of the fat was greater with the standard diet (olive oil) than with diets whose fat content was provided by goat or cow milk. The digestive utilization of the fat was greater in the transected and resected rats receiving a diet of goat's milk (rich in medium-chain triglycerides) than those given a cow-milk-based diet and more closely approached the values obtained for olive oil. The consumption of goat milk reduced levels of cholesterol while levels of triglycerides, HDL, GOT and GPT remained with in the normal ranges, for both transected and resected animals. The advantageous effect of goat milk on the metabolisim of lipids with respect to cow milk suggests that the former should be included in the diet in eases of malabsorption snydrome.     

Bioavailability of iron in goat milk compared with cow milk fed to anemic rats

Bioavailabilities of iron from dehydrated whole and skim goat milk were investigated using iron-deficient rats. Hemoglobin regeneration efficiencies were determined as the percent conversion of dietary iron into hemoglobin. The respective hemoglobin regeneration efficiencies for groups fed whole goat milk, whole cow milk, skim goat milk, and skim cow milk were 50.6, 13.1, 26.0, and 13.0%, indicating that iron bioavailability of goat milk was greater than cow milk. However, rats fed each milk had negative net increases in hemoglobin concentrations, implying that the iron contents of each milk were not adequate. For animals consuming whole goat milk supplemented with ferrous sulfate, the slope relating hemoglobin iron gained versus iron intake was .95. Respective bioavailabilities relative to ferrous sulfate were 54, 14, 28, and 14% for the four sources of milk. Iron bioavailability of goat milk is superior to cow milk when fed to anemic rats.     

Performance and amino acid utilization of early lactation dairy cows fed regular or reduced-fat dried distillers grains with solubles

The objective of this study was to evaluate lactation response and AA utilization of early lactation cows fed 2 types of dried distillers grains with solubles (DG): regular (DDGS) or reduced-fat (RFDGS). Thirty-six Holstein cows 19.7 ± 2.6 d in milk at the start of the experiment were used in a randomized complete block design for 14 wk including a 2-wk covariate period. Treatments consisted of the following diets: 1) control (CON) diet containing 0% DG; 2) diet containing 22% DDGS; and 3) diet containing 20% RFDGS. Distillers grains replaced soybean meal, expeller soybean meal, and soyhulls from the CON diet. Diets were formulated to be similar in crude protein, ether extract, neutral detergent fiber, and net energy for lactation concentrations. Dry matter intake (24.7 kg/d) and milk yield (39.3 kg/d) were similar for all diets. Milk fat and lactose percentages were unaffected by diets; however, protein percentage was greater for cows fed the DG diets compared with the CON diet. Consequently, milk protein yield was also greater for the DG diets compared with CON. Milk urea nitrogen decreased for cows fed DG diets and averaged 11.8, 10.9, and 10.1 mg/dL, respectively, for CON, DDGS, and RFDGS. Feed efficiency tended to be greater and N efficiency was greater for cows fed DG compared with CON. Body weight (711 kg), body weight change (+0.49 kg/d), and body condition score (3.36) were similar for all diets, but cows fed CON tended to gain more body condition (+0.14) than cows fed DG diets. Amino acid utilization was evaluated at the peak of milk production corresponding to wk 9 of lactation. Arterial Lys concentration was lower with DG diets (70.4, 58.6, and 55.8 μM/L). Cows fed DG had greater arterial Met concentration (21.3 μM) compared with CON (14.9 μM). Arterio-venous difference of Lys was similar across diets, whereas that of Met was greater for the DG diets compared with the CON diet (10.3 vs. 13.0 μM/L). Extraction efficiency of Lys by the mammary gland was greater for DG diets than for CON (76.1 vs. 65.4%). Mammary uptake of Lys (2.56 g/kg of milk) was similar for all diets, and the uptake of Met tended to increase in cows fed DG diets. Plasma glucose, triglyceride, and total cholesterol were unaffected by treatment; however, cows fed DG diets had lower β-hydroxybutyrate and tended to have lower nonesterified fatty acid concentrations than cows fed the CON diet. Despite the apparent deficiency of Lys, milk protein percentage was increased in cows fed DG diets.     

Effect of dietary inclusion of goat milk on the bioavailability of zinc and selenium in rats

The effects of dietary inclusion of freeze-dried goat and cow milk on the utilization of zinc and selenium, and on the metabolic fate of zinc, were studied in transected (control) and resected rats (resection of 50% of the distal small intestine). Intestinal resection reduced the apparent digestibility coefficient and zinc retention in the cow milk diet, whereas these biological indices were similar in transected (control) and resected rats with standard (without milk) and goat milk diets. The apparent digestibility coefficient and retention of selenium were not affected by intestinal resection in the animals fed with the three diets studied. In transected (control) and resected rats, the apparent digestibility coefficient and retention of zinc and selenium were higher for the goat milk diet than for the other two diets. Zinc deposits in the organs, expressed as microg/g dry weight were in order of decreasing concentrations: femur, testes, sternum, liver, kidney, heart, spleen, longissimus dorsi muscle and brain. Deposits were greatest with the goat milk diet, followed by the standard diet and were lowest for the rats given the cow milk diet, both for transected (control) and resected animals. We conclude that consumption of the goat milk diet produces a greater bioavailability of zinc and selenium and a greater deposit of zinc in key organs, for both the transected (control) and the resected rats, with respect to the standard diet and the cow milk diet.     

Digestion, Ruminal Fermentation, Ciliate Protozoal Populations, and Milk Production from Dairy Cows Fed Cinnamaldehyde, Quebracho Condensed Tannin, or Yucca schidigera Saponin Extracts

Four ruminally cannulated lactating cows were used in a 4 × 4 Latin square design (28-d periods) to determine the effects of cinnamaldehyde (CIN; 1 g/cow per day), condensed tannins from quebracho trees (QCT, containing 70% tannins, 150 g/cow per day), and saponins from Yucca schidigera extract (YSE, containing 10% saponins; 60 g/cow per day) on digestion, ruminal fermentation characteristics, protozoal populations, and milk production. Intake of dry matter was not affected by the addition of CIN or QCT, but cows fed YSE had lesser intake than cows fed the control diet (21.8 vs. 23.2 kg/d). Apparent total-tract digestibilities of dry matter, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber were unaffected by dietary treatments. Supplementation with CIN, QTE, or YSE did not affect in situ ruminal degradation of soybean meal, grass silage, or corn grain. Ruminal pH (6.67), total volatile fatty acid concentration (135 mM), and molar proportions (mol/100 mol of total volatile fatty acid) of acetate (65.0), propionate (19.6), and butyrate (11.2) were similar among treatments. Ruminal NH₃-N concentration was not changed by the addition of CIN and YSE, but tended to decrease in cows fed QCT compared with cows fed the control diet (132 vs. 160 mg/L). Total numbers of ruminal protozoa were not changed by adding CIN, QCT, or YSE in the diet (5.85 log₁₀/mL). However, the number of Isotricha was greater in ruminal fluid of cows fed CIN than in ruminal fluid of cows fed the control diet (4.46 vs. 4.23 log₁₀/mL). Milk production (33.1 kg/d), milk fat (4.3%), and milk protein (3.5%) remained unchanged between dietary treatments. Results of this study show that under our experimental conditions, supplementing dairy cow diets with CIN, QCT, or YSE had limited effects on digestion, ruminal fermentation characteristics, and protozoal populations. The lack of effects observed in this study suggests that these antimicrobials require administration at greater doses to favorably alter rumen microbial fermentation.     

Diet supplementation with fish oil and sunflower oil to increase conjugated linoleic acid levels in milk fat of partially grazing dairy cows

The objective of this study was to determine the long-term effect on milk conjugated linoleic acid (cis-9, trans-11 CLA) of adding fish oil (FO) and sunflower oil (SFO) to the diets of partially grazing dairy cows. Fourteen Holstein cows were divided into 2 groups (7 cows/treatment) and fed either a control or oil-supplemented diet for 8 wk while partially grazing pasture. Cows in group 1 were fed a grain mix diet (8.0 kg/d, DM basis) containing 400 g of saturated animal fat (control). Cows in the second group were fed the same grain mix diet except the saturated animal fat was replaced with 100 g of FO and 300 g of SFO. Cows were milked twice a day and milk samples were collected weekly throughout the trial. Both groups grazed together on alfalfa-based pasture ad libitum and were fed their treatment diets after the morning and afternoon milking. Milk production (30.0 and 31.2 kg/d), milk fat percentages (3.64 and 3.50), milk fat yield (1.08 and 1.09 kg/d), milk protein percentages (2.97 and 2.88), and milk protein yield (0.99 and 0.91 kg/d) for diets 1 and 2, respectively, were not affected by the treatment diets. The concentrations of cis-9, trans-11 CLA (1.64 vs. 0.84 g/100 g of fatty acids) and vaccenic acid (5.11 vs. 2.20 g/100 g of fatty acids) in milk fat were higher for cows fed the oil-supplemented diet over the 8 wk of oil supplementation. The concentration of cis-9, trans-11 CLA in milk fat reached a maximum (1.0 and 1.64 g/100 g of fatty acids for diets 1 and 2, respectively) in wk 1 for both diets and remained relatively constant thereafter. The concentration of vaccenic acid in milk fat followed the same temporal pattern as cis-9, trans-11 CLA. In conclusion, supplementing the diet of partially grazing cows with FO and SFO increased the milk cis-9, trans-11 CLA content, and that increase remained relatively constant after 1 wk of oil supplementation.     

Milk fatty acid composition of grazing dairy cows when supplemented with linseed oil

The effects of varying amounts of linseed oil (LSO) in grazing dairy cows’ diet on milk conjugated linoleic acid (cis-9, trans-11 CLA) were investigated in this study. Twelve Holstein cows in midlactation (150 ± 19 DIM) were placed on alfalfa-based pasture and assigned to 4 treatments using a 4 × 4 Latin square design with 3-wk periods. Treatments were: 1) control grain supplement; 2) control grain supplement containing 170 g of LSO (LSO1); 3) control grain supplement containing 340 g of LSO (LSO2); and 4) control grain supplement containing 510 g of LSO (LSO3). Grain supplements were offered at 7 kg/d. Additional 100 g/d of algae, divided evenly between the 2 feeding times, were added to every treatment diet. Milk samples were collected during the last 3 d of each period and analyzed for chemical and fatty acid composition. Treatments had no effect on milk production (18.9, 18.5, 19.6, and 19.1 kg/d for treatments 1 to 4, respectively). Linseed oil supplementation caused a quadratic increase in milk fat (3.23, 3.44, 3.35, and 3.27% for treatments 1 to 4, respectively) and protein (3.03, 3.19, 3.12, and 3.08%) contents. Concentrations (g/100 g of fatty acids) of milk cis-9, trans-11 CLA (1.12, 1.18, 1.39, and 1.65 for treatments 1 to 4, respectively) and VA (3.39, 3.62, 4.25, and 4.89) linearly increased with LSO supplementations. Results from this trial suggest that the increase in milk cis-9, trans-11 CLA was proportional to the amounts of LSO fed. In conclusion, adding LSO to grazing dairy cow diets can improve the nutritional value of milk without compromising milk composition or cow performance.     

Effect of supplementing myristic acid in dairy cow rations on ruminal methanogenesis and fatty acid profile in milk

The objective of this study was to evaluate the effects of supplementing myristic acid in dairy cow rations on ruminal methanogenesis and the fatty acid profile in milk. Twelve multiparous Holstein dairy cows (710 ± 17.3 kg of live weight; 290 ± 41.9 d in milk) housed in a tie-stall facility were used in the study. The cows were paired by parity and days in milk and allocated to 1 of 2 treatments: 1) the regular milking cow total mixed ration (control diet), and 2) the regular milking cow total mixed ration supplemented with 5% myristic acid on a dry matter basis (MA diet). The cows were fed and milked twice daily (feeding, 0830 and 1300 h; milking, 0500 and 1500 h). The experiment was conducted as a completely randomized design and consisted of a 7-d pretrial period when cows were fed the control diet to obtain baseline measurements, a 10-d dietary adaptation period, and a 1-d, 8-h measurement period. The MA diet reduced methane (CH₄) production by 36% (608.2 vs. 390.6 ± 56.46 L/d, control vs. MA diet, respectively) and milk fat percentage by 2.4% (4.2 vs. 4.1 ± 0.006%, control vs. MA diet, respectively). The MA diet increased 14:0 in milk by 139% and cis-9 14:1 by 195%. There was a correlation (r = −0.58) between the 14:0 content in milk and CH₄ production and cis-9 14:1 and CH₄ production (r = −0.47). Myristic acid had no effect on the contents of CLA or trans-10 18:1 and trans-11 18:1 isomers in milk. These results suggest that MA could be used to inhibit the activities of methanogens in ruminant animals without altering the conjugated linoleic acid and trans-18:1 fatty acid profile in milk.     

Influence of carbohydrate source on ruminal fermentation characteristics, performance, and microbial protein synthesis in dairy cows

Eight multiparous Holstein cows (676 ± 57 kg of body weight; 121 ± 17 d-in-milk) were used in a replicated 4 × 4 Latin square design to determine the effects of 4 sources of carbohydrate on milk yield and composition, ruminal fermentation, and microbial N flow to the duodenum. Four cows in one of the Latin squares were fitted with permanent ruminal cannulae. Diets contained (DM basis) 50% forage in combinations of alfalfa hay and barley silage, and 50% concentrate. The concentrate portion of the diets contained barley, corn, wheat, or oats grain as the primary source of carbohydrate. Intake of DM ranged from 24.0 to 26.2 kg/d, and it tended to be lower in cows fed the wheat-based diet compared with those fed the barley-based diet; consequently, milk yield tended to be lower in cows fed the wheat-based diet compared with those fed the barley-based diet. Cows fed the barley- or wheat-based diets had a lower milk fat content compared with those fed the corn-based diet. Ruminal fermentation characteristics were largely unaffected by the source of dietary carbohydrate, with similar ruminal pH and volatile fatty acid and ammonia concentrations for the first 6 h after the morning feeding. Dietary treatment did not affect total tract apparent digestibility of DM, organic matter, and neutral detergent fiber; however, total tract apparent digestibility of starch in cows fed the oats-based diet was higher compared with those fed the corn-and wheat-based diets. Nitrogen that was used for productive purposes (i.e., N secreted in milk + N apparently retained by the cow) tended to be lower in cows fed the wheat-based diet compared with cows fed the barley-, corn-, or oats-based diets. Urinary purine derivative (PD) excretion was similar in cows fed the barley-, corn-, and wheat-based diets; however, purine derivative excretion was higher in cows fed the barley-based diet compared with those fed the oats-based diet. Consequently, estimated microbial N flow to the duodenum was 49 g/d higher in cows fed the barley-based diet compared with those fed the oats-based diet. Improved production performance with corn and barley diets appeared to be due to greater nutrient absorption than in cows fed oats and wheat diets, rather than improved nutrient utilization efficiency.