Fatty acid metabolism and deposition in subcutaneous adipose tissue of pasture- and feedlot-finished cattle.

An experiment was conducted to evaluate the effects of pasture finishing versus feedlot finishing, over time, on fatty acid metabolism in Angus crossbred steers (n = 24). Ruminal fluid, serum, and adipose tissue biopsies were obtained on d 0, 28, 84, and 140. Pasture forages and diet ingredient samples were obtained at 14-d intervals to determine nutritive value and fatty acid composition. The feedlot diet consisted of corn silage, cracked corn grain, soybean meal, and a vitamin and mineral supplement. The pasture-finished steers grazed sequentially on triticale (x Triticosecale rimpaui)/annual ryegrass (Lolium multiflorum), alfalfa (Medicago sativa)/orchardgrass (Dactylis glomerata), and a cool-season grass/legume mixture. The feedlot diet contained an average of 57% of total fatty acids as linoleic acid and 2% as linolenic acid. The pasture forages contained 9% of total fatty acids as linoleic acid and 66% as linolenic acid. Concentrations (% of total fatty acids) of linolenic acid were greater (P < 0.05) in ruminal fluid, serum, and adipose tissue of the pasture-finished steers, compared with the feedlot-finished steers. Concentrations (% of total fatty acids) of cis-9, trans-11 CLA were greater (P < 0.05) in adipose tissue of the pasture-finished steers than feedlot-finished steers. Concentrations of cis-9, trans-11 CLA in adipose tissue declined (P < 0.05) in the feedlot-finished steers from d 0 to 28 to 84. In the pasture-finished steers, concentrations of cis-9, trans-11 CLA in adipose tissue (mg/g of tissue) peaked (P < 0.05) on d 28 and remained elevated (ranged from 9.91 to 12.80 mg/g of tissue) throughout the duration of the study. In the pasture-finished steers, linolenic acid concentrations tended to peak (P = 0.07) on d 28 and remained elevated (ranged from 0.64 to 0.80% of total fatty acids) throughout the study. It appears that only a short time is needed to alter the n-3 and CLA composition of adipose tissue in cattle finished on pasture.

Blood mineral, hormone, and osteocalcin responses of multiparous Jersey cows to an oral dose of 25-hydroxyvitamin D3 or vitamin D3 before parturition.

Twenty-seven multiparous Jersey cows were randomly assigned to receive an oral bolus containing corn starch (control, CON), corn starch plus 15 mg of 25-hydroxyvitamin D(3) (25-OH), or 15 mg of cholecalciferol (D(3)) at 6 d before expected parturition. Cows were maintained in individual box stalls from 20 d before expected parturition and fed a common diet. Jugular blood samples were collected at -14, -13, -5, -4, -3, -2, -1 d before expected calving, at calving, and at 1, 3, 5, 7, 9, 11, 13, 28, 56, and 84 d postcalving. After calving, cows were housed in 1 pen in a free-stall barn and consumed a common diet. Colorimetric assays were used to analyze Ca, P, and Mg concentrations in serum. Serum concentrations of osteocalcin (OC), an indicator of bone formation, serum 25-hydroxyvitamin D(3), and parathyroid hormone (PTH) were determined in samples obtained from d -5 through d 13. The 9 control multiparous cows and 5 untreated primiparous cows were used to evaluate the effect of parity on the variables that were measured. There was no effect of parity on Ca, PTH, or 25-OH concentration. Compared with second-lactation cows and older cows (>2 lactations), first-lactation cows had greater serum OC (22.3, 32.0, and 48.3 ng/mL, respectively), indicating that younger animals were forming more bone. Blood Ca, P, and Mg decreased near the time of calving and then increased over time. Serum 25-hydroxyvitamin D(3) was greater for cows dosed with 25-OH (119.0 ng/mL) compared with those dosed with D(3) (77.5 ng/mL) or CON (69.3 ng/mL). Cows dosed with 25-OH tended to have lower serum PTH concentration, but treatments did not affect serum Ca, P, or Mg. Serum OC was greater in second-lactation cows compared with cows entering their third or fourth lactation but OC was unaffected by treatment. Although results indicated a 60% increase in serum 25-hydroxyvitamin D(3) due to a single oral dose of 25-OH before calving, the amount administered in this study apparently was not sufficient for initiation of any improvement in Ca homeostasis at parturition.

Biohydrogenation of unsaturated fatty acids in continuous culture fermenters during digestion of orchardgrass or red clover with three levels of ground corn supplementation.

Diet digestibility and outputs of biohydrogenation intermediates were assessed in a continuous culture of ruminal microorganisms. Orchardgrass or red clover harvested and frozen during spring or fall served as the primary substrates for fermentation. During 10-d incubations, fermenters were fed thawed forage (50 g of DM/d), forage (42 g/d) plus 8 g/d of corn, or forage (34 g/d) plus 16 g/d of corn. Effluents from the last 3 d of incubation were composited for analyses. Starch input increased from 5 to 27% of DM as corn input increased from 0 to 16 g/d. Corn input reduced (P < 0.01) pH, increased (P < 0.01) microbial DM yield, and increased (P = 0.01) digestibility of DM, NDF, CP, and nonstructural carbohydrates. Overall, apparent hydrogenation (percentage) of cis9-18:1, 18:2n-6, and 18:3n-3 was greater (P < 0.05) with orchardgrass than clover. Hydrogenation of cis9-18:1 and 18:2n-6 increased (P = 0.01), but hydrogenation of 18:3n-3 decreased (P = 0.01) linearly due to corn input, regardless of forage. As a result, output of trans11, cis15-18:2 also decreased (P = 0.01). Average output of cis9,trans11-18:2 was greater (P = 0.01) for clover (1.3 mg/d) compared with orchardgrass (0.6 mg/d), but corn input with either forage increased (P = 0.01) cis9,trans11-18:2 output by 205%. Output of trans11-18:1 was greater (P = 0.01) from orchardgrass compared with clover (174 vs. 90 mg/d), but corn increased (P = 0.01) trans11-18:1 output only from clover fermentations. Output of trans10-18:1 was greater (P = 0.01) in response to orchardgrass compared with clover (10 vs. 4 mg/d), but corn addition doubled the output regardless of forage type. Output of trans10,cis12-18:2, which did not differ due to forage type, increased (P = 0.01) twofold in response to corn. Cis9,cis11-18:2 was a primary conjugated isomer produced from forage fermentations, but its output decreased (P = 0.03) in response to corn input. When inputs of 18:2n-6 plus 18:3n-3 were less than 0.9% of total DM (clover), hydrogenation was low (87%). When 18:2n-6 plus 18:3n-3 inputs were from 1.2 to 1.5% of total DM (orchardgrass), hydrogenation averaged 96%. Despite greater hydrogenation, incremental additions of cis9-18:1 and 18:2n-6 from corn grain increased (P < 0.05) outputs of trans10-18:1, trans11-18:1, trans10,cis12-18:2, cis9,trans11-18:2, and trans,trans-18:2 in effluent. Results suggest that forage species alone or in combination with corn grain can alter hydrogenation and profiles of intermediates to varying degrees.

Reduced fatty acid synthesis and desaturation due to exogenous trans10,cis12-CLA in cows fed oleic or linoleic oil.

To determine effects of an elevated supply of cis9,trans11-18:2 (9/11CLA) or trans10,cis12-18:2 (10/12CLA) on de novo synthesis and desaturation of long-chain fatty acids, four Holstein cows fed high-oleic sunflower (OLE) or high-linoleic safflower oil (LIN) at 2.5% of DM were infused (0.625 g/h) with 9/11CLA or 10/12CLA for 48 h via the abomasum. Treatments were assigned in a 2 x 2 factorial design. The assigned diets were fed for 11 d before each 48-h infusion period. Milk samples were obtained at 12 and 0 h before infusion and at 12-h intervals from 0 to 96 h. Concentrations of trans11-18:1 and 18:2n-6 in arterial plasma phospholipid, triglyceride, and FFA fractions were greater due to feeding LIN compared with OLE. Infused 9/11CLA and 10/12CLA were incorporated into plasma triglycerides and FFA primarily. Exogenous 10/12CLA also was found in plasma phospholipids. Milk yield and DMI were not affected by treatments. Percentages and yields of protein, lactose, and SNF in milk also were not affected by treatments. Milk fat percentage and yield, however, decreased 25% from 0 to 96 h in response to infusion of 10/12CLA compared with 9/11CLA. Yields of trans11-18:1, 9/11CLA and 18:2n-6 in milk fat before infusion were higher when LIN was fed compared with OLE. Infusion of 9/11CLA, regardless of diet, increased 9/11CLA in milk fat by 44%. Although 10/12CLA was not detectable in milk fat before infusion, it averaged 6 mg/g of total fatty acids and 2 g/d after 48 h. At 48 h, recovery in milk of infused 9/11CLA was 16% compared with 8% for 10/12CLA. Yields of saturated 6:0 to 16:0, cis9-18:1, 9/11CLA, and 20:4n-6 were reduced by 10/12CLA infusion. Due to a 40% increase in the concentration of 18:0 by 48 h of 10/12CLA infusion, however, yield of 18:0 was not affected. Ratios of cis9-18:1/18:0, 9/11CLA/trans11-18:1, and 20:4n-6/18:2n-6 in milk fat decreased in response to infusion of 10/12CLA, regardless of diet. At peak concentration of 10/12CLA, reductions in cis9-18:1 and saturated 4:0-16:0 yields accounted for 36% and 53% of the decrease in total fatty acid yield. Results indicated 10/12CLA alters lipid metabolism in the bovine mammary gland by simultaneously reducing de novo synthesis and desaturation. Furthermore, milk triglyceride synthesis may have a stringent requirement for endogenously synthesized oleic acid.

Oxidation and textural characteristics of butter and ice cream with modified fatty acid profiles.

The primary objective of this study was to evaluate oxidation and firmness of butter and ice cream made with modified milkfat containing enhanced amounts of linoleic acid or oleic acid. The influence of the fatty acid profile of the HO milkfat relating to product properties as compared with the influence the fatty acid profile of the HL milkfat was the main focus of the research. Altering the degree of unsaturation in milkfat may affect melting characteristics and oxidation rates, leading to quality issues in dairy products. Three milkfat compositions (high-oleic, high-linoleic, and control) were obtained by modifying the diets of Holstein cows. Ice cream and butter were processed from milkfat obtained from cows in each dietary group. Butter and ice cream samples were analyzed to determine fatty acid profile and firmness. High-oleic milkfat resulted in a softer butter. Solid fat index of high-oleic and high-linoleic milkfat was lower than the control. Control ice cream mix had higher viscosity compared with high-oleic and high-linoleic, but firmness of all ice creams was similar when measured between -17 and -13 degrees C. Nutritional and textural properties of butter and ice cream can be improved by modifying the diets of cows.

Trans18:1 and 18:2 isomers in blood plasma and milk fat of grazing cows fed a grain supplement containing solvent-extracted or mechanically extracted soybean meal.

Thirty Holstein cows grazing mixed clover-grass pastures for 12 wk from May through July were fed a grain supplement containing solvent-extracted soybean meal (SES), or mechanically extracted soybean meal (MES) to determine whether differences in supplemental 18:2n6 fatty acid intake altered secretion of unsaturated fatty acids. Groups of 10 cows each were fed in two equal feedings a supplement (7.3 kg/d) containing ground corn plus either 1.8 kg of SES, 2.2 kg of MES, or 2.2 kg of MES plus 30 g of methionine hydroxy analog (Alimet; MESM). Fatty acid content (% of DM) of grass and clover in pastures averaged 1.9 and 1.5%, respectively. Concentration of 18:3n3 was higher in grass compared with clover (532 vs. 454 mg/g of total fatty acids). Yield of milk (32 kg/d average) and milk components did not differ by supplements. Total blood plasma fatty acids (mg/ml) during wk 4 were higher due to MESM (1.0) compared with MES (0.6) or SES (0.6). Cows fed MESM or MES had greater concentrations of 18:2n6, trans11-18:1, and cis9,trans11-18:2 in plasma compared with cows fed SES. The additional trans11-18:1 was found exclusively in plasma triglycerides, whereas the additional cis9,trans11-18:2 was found in plasma phospholipids and free fatty acids. Daily yields of 18:2n6, trans11-18:1 and cis9,trans11-18:2 in milk fat were greater for cows fed MES or MESM compared with SES. Results indicate yields of trans11-18:1, cis9, trans11-18:2, 18:2n6, and 18:3n3 in milk fat of pasture-fed cows were enhanced by feeding a grain supplement containing mechanically extracted, rather than solvent-extracted, soybean meal.

Phosphorus partitioning during early lactation in dairy cows fed diets varying in phosphorus content.

The effect of dietary P content on P partitioning and excretion during early lactation was evaluated in 13 cows fed diets containing 0.34 (no supplementary P), 0.51, or 0.67% P. All cows were fed a common pre-partum total mixed ration (TMR) (0.28% P), followed by common TMR (0.51% P) for 7 d post-partum. On day 7, cows were randomly assigned to one of the three dietary P treatments. All treatment diets contained 16.6% CP, 15.2% ADF, 26.3% NDF, and 0.74% Ca. Total collections of milk, urine, and feces were conducted during weeks 3, 5, 7, 9, and 11 of lactation. Average body weight (591 kg), milk yield (47.9 kg/d), and DMI (25.2 kg/d) throughout the 10-wk trial were not affected by dietary P content. With increasing dietary P, however, linear increases in P intake (84.7, 135.2, and 161.5 g/d), fecal P (42.3, 87.5, and 108.6 g/d), urinary P (0.32, 1.28, and 3.90 g/d), and total P excretion (42.6, 88.8, and 112.5 g/d) were observed. Apparent P digestibility (49.0, 34.4, and 32.8% of P intake) decreased quadratically with increasing dietary P. Phosphorus balance was highly variable, but cows fed the 0.34% P diet were in negative P balance longer than were cows fed diets containing 0.51 or 0.67% P. With increasing dietary P, serum concentrations of inorganic P increased linearly, but serum Ca and Mg concentrations decreased. Increasing dietary P increased fecal and urinary P excretion in early lactation cows. Increased duration of negative P balance and changes in blood mineral concentrations suggest that cows fed low P diets mobilized more P from body reserves than cows on medium- and high-P diets.

Characterization of 18:1 and 18:2 isomers produced during microbial biohydrogenation of unsaturated fatty acids from canola and soya bean oil in the rumen of lactating cows.

Ruminal production of biohydrogenation intermediates in response to unsaturated oils was assessed using 24 Jersey cows fed a control diet or the control diet supplemented at 35 g/kg dry matter (DM) with canola, soya bean, or a mixture of equal amounts of canola plus soya bean oil for 4-weeks. Total fatty acid content averaged 63 or 35 g/kg DM for oil-supplemented diets or control. Oleic acid accounted for 6, 29, 21 or 12 g/kg DM in the control, canola, mixture, or soya bean oil diet, respectively. Linoleic acid averaged 17, 19, 26, or 33 g/kg DM and linolenic acid 5, 5, 6 or 8 g/kg DM for control, canola, mixture, or soya bean oil. Concentrations of cis12-, trans11-, trans13+14, and trans15-18:1 were 0.81, 2.99, 2.24, and 0.73 mg/g rumen fluid, respectively, in response to soya bean oil and were 126, 90, 45, and 38% greater compared with other diets. Trans11cis15-, cis9trans11- and cis9 cis11-18:2 also were greater when soya bean oil (0.30, 0.34 and 0.01 mg/g, respectively) was fed compared with other treatments (0.12, 0.21 and 0.004 mg/g, respectively). Feeding canola oil resulted in greater concentrations of trans4-, trans5-, trans6+7+8-, trans9- and trans10-18:1 (0.20, 0.25, 0.87, 0.39 and 0.70 mg/g, respectively) compared with other diets (0.09, 0.15, 0.36, 0.20 and 0.46 mg/g, respectively). Trans10cis12-18:2 concentration did not differ as a result of diet and averaged 0.002 mg/g rumen contents. The pattern of 18:1 and 18:2 isomers formed during ruminal biohydrogenation depends greatly on dietary profile of unsaturated fatty acids.

Nitrogen and phosphorus partitioning in lactating Holstein cows fed different sources of dietary protein and phosphorus.

To evaluate dietary N and P partitioning, 36 Holstein cows grouped by parity were assigned at calving to diets supplemented with soybean meal (S) or a combination of S and blood meal (B). Diets S and B were formulated to contain 16.2% CP and 0.35% P using mono- and dicalcium phosphate (PM) or wheat bran (WB) as the supplemental source of P. Actual dietary P contents were 0.38, 0.36, 0.34, and 0.34% for SPM, BPM, SWB, and BWB. Two-day total collections of feces, urine, and milk were conducted between 30 and 45 d in milk (DIM), then all cows were fed a control diet until 120 DIM. Between 120 and 150 DIM, cows were again fed the diet assigned at calving, then 2-d total collections of feces, urine, and milk were conducted. Milk production was similar for cows fed diets containing WB (SWB or BWB) when compared with cows fed PM. However, DMI tended to be lower, and P intake and total P excretion were lower in response to WB (20.7 kg/d, 71.9 g/d, and 40.3 g/d) compared with cows fed PM (23.0, 86.7, and 46.8 g/d). Apparent digestibility of dietary P did not differ due to source of supplemental P, averaging 45% across diets. The lower P intake by cows fed WB resulted in lower absorbed P and lower retained P (32.2 and 7.5 g/d) compared with those fed PM (40.6 and 13.4 g/d). Apparent N digestibility, urinary N, and N retention were not affected by P source. Blood meal decreased apparent N digestibility and absorbed N, and also decreased P retention compared with S. In later lactation, cows retained proportionately more absorbed N and P in body tissue and secreted less in milk than they did in early lactation. Results indicated the organic source of P (phytate-P) in WB can be used to provide a substantial portion of the P needed in dairy cattle diets after peak lactation, but the amount of WB in the diet during early lactation should be limited to prevent suppression of DMI and P retention.

Effect of degradability of dietary protein and fat on ruminal, blood, and milk components of Jersey and Holstein cows.

Twelve Holstein cows and 12 Jersey cows were used in six 4 x 4 Latin squares to investigate the effects of the degradability of dietary protein and supplemental dietary fat on milk components. Dietary dry matter contained 16% crude protein with two concentrations of ruminally undegradable protein (RUP) obtained by substituting blood meal for a portion of the soybean meal. Treatments were 1) 29% RUP, 0% added fat; 2) 29% RUP, 2.7% added fat (Ca soaps of fatty acids); 3) 41% RUP, 0% added fat; and 4) 41% RUP, 2.7% added fat. The dry matter of the total mixed ration fed at 1000 and 1400 h consisted of 30% corn silage, 29% alfalfa haylage, and 41% concentrate. Supplemental dietary fat depressed dry matter intake by 6.2%. Plasma urea N was greater at 0700 and 1600 h for Jerseys fed diets containing added fat and greater at 0700 h for Holsteins fed diets containing 41% RUP than for Holsteins fed 0% added fat and 29% RUP. When averaged across both breeds, milk production increased 7.1%, and production of 4% fat-corrected milk by Jerseys increased 8.4%, in response to added dietary fat. Milk protein was reduced when Holstein diets contained 41% RUP. Milk protein content was reduced 7.1 and 3.9%, and milk urea N was increased 4.9 and 8.5%, by added fat and 41% RUP in both breeds, respectively. Added fat reduced the concentration, but not the yield, of milk components. Substitution of blood meal decreased the concentration and yield of milk protein and casein N.

Intake, site, and extent of nutrient digestion of lactating cows grazing pasture.

The objective of this study was to determine intake and site and extent of nutrient digestion of lactating cows grazing pasture with or without energy supplementation. Four dual-cannulated (rumen and proximal duodenum) cows were randomly assigned to two groups to graze mixed cool season grass legume pasture with either no supplement or with 6.4 kg of cracked corn and mineral mix daily in a switchback design with three 2-wk periods. Markers (Cr2O3 and Co-EDTA) were used to estimate intake, duodenal flow, fecal output, and fractional rates of passage from the rumen. Daily OM intake was similar between diets, but OM intake of pasture was lower when cows were fed corn. Apparent OM and NDF digestibilities in the rumen and total digestive tract were lower when cows were supplemented with corn than when they consumed pasture only. Supplemental corn decreased ruminal NH3 N (22 vs. 17 mg/dl) and increased N recovery at the duodenum (86% vs. 75% of N intake). Nonammonia, nonmicrobial N flowing to the duodenum was 67% of the total NAN flow. Corn increased energy intake of grazing cows, but decreased herbage intake and digestibility.

Dietary and ruminally derived trans-18:1 fatty acids alter bovine milk lipids.

The objectives of this study were to determine whether dietary fish oil enhances production of trans-18:1 isomers in the bovine rumen and whether flow of ruminally derived and/or dietary trans-18:1 to the small intestine is correlated with milk fat production. Four lactating Holstein cows with cannulas in the rumen and proximal duodenum were fed diets with 0% supplemental fat (control diet), 3% hydrogenated tallow fatty acids (HTFA diet), 1.5% menhaden oil plus 1.5% stearic acid (MO+SA diet), or 1.5% soybean oil plus 1.5% partially hydrogenated soybean oil (SBO+HSBO diet) in a 4 x 4 Latin square design. Intakes of trans-18:1 were 0, 12, 0 and 69 g/d when cows were fed the control, HTFA, MO+SA and SBO+HSBO diets, respectively. However, the extent of 18:1 + 18:2(n-6) + 18: 3(n-3) biohydrogenation in the rumen was reduced by consumption of the MO+SA and SBO+HSBO diets. As a result, flow of trans-18:1 to the duodenum was 163 g/d for MO+SA-fed cows and 152 g/d for SBO+HSBO-fed cows compared with 38 g/d for cows fed the HTFA and control diets. Incomplete biohydrogenation accounted for all of the trans-18:1 flow when the MO+SA diet was fed. Compared with results when the HTFA and control diets were fed, milk fat percentage was lower and concentration of trans-18:1 in milk fat was higher when the MO+SA and SBO+HSBO diets were fed. Across all treatments, milk fat percentage decreased linearly with the amount of trans-18:1 flowing to the duodenum and the concentration of trans-18:1 in milk fat. Results indicate that bovine milk fat percentage is depressed by trans-18:1, whether derived from the diet or from incomplete biohydrogenation of unsaturated fatty acids.

Effects of dietary calcium and age on parathyroid hormone, calcitonin and serum and milk minerals in the periparturient dairy cow.

Ten pregnant heifers and 10 pregnant cows (three or more pregnancies) were assigned to groups of five and fed either the recommended (low) amount of calcium or excess (high) calcium in their diet for 4 wk before parturition to determine the influence of prepartum calcium intake and age on hormonal control of peripartum calcium homeostasis. After parturition all groups received a diet with calcium adequate for lactation. Jugular blood samples from 21, 14, 7, 6, 5, 4, 3, 2, and 1 d prepartum through 0, 1, 2, 3, 5, 7, 14 and 21 d postpartum were assayed for concentration of parathyroid hormone, calcitonin, calcium, magnesium and phosphorus. Heifers and cows receiving high calcium diets had higher calcium and lower parathyroid hormone in blood serum before parturition than animals receiving the low calcium diets. Cows, but not heifers, fed high calcium diets exhibited severe hypocalcemia at parturition, remained hypocalcemic for 3 d and had low serum calcitonin. Regardless of dietary group, concentrations of parathyroid hormone and magnesium in serum increased after the first week of lactation. Feed intake during lactation, corrected for metabolic body weight, was similar for both dietary treatments and ages. Milk production per kilogram metabolic body weight was highest during the first week of lactation for cows fed low calcium diets before parturition. There was no correlation between hypocalcemia and loss of calcium in colostrum or milk. Feeding low dietary calcium to cows in the prepartum period was effective in the prevention of severe hypocalcemia at parturition. In contrast, dietary treatment of heifers had no effect on serum calcium concentration at parturition.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive and metabolic characteristics of dairy cattle supplemented with beta-carotene.

Seventy-eight Holstein cows alternately were assigned at calving to receive beta-carotene supplementation or act as controls to determine effects of beta-carotene on reproduction and carotene, luteinizing hormone, progesterone, insulin, glucose, and glucagon concentrations in blood plasma. Cows were fed a corn silage-based complete ration. Biweekly jugular blood samples were collected beginning the week after parturition through 90 days. At day 30, supplemented cows received 600 mg synthetic beta-carotene daily for 60 days. Plasma carotene reached a peak of 2.45 micrograms/ml compared to 1.50 micrograms/ml in controls. Supplementation significantly increased plasma carotene but had no effect on luteinizing hormone, progesterone, insulin, glucose, glucagon, or reproductive measures. Days to first heat, days to first breeding, days open, and services per conception averaged 74, 74, 95, and 1.7 for supplemented cows and 64, 76, 102, and 1.9 for control cows. Progesterone increased as lactation progressed. Somatic cells were not different between supplemented and control cows. Supplementation of beta-carotene did not improve reproductive efficiency or alter luteinizing hormone, progesterone, insulin, glucose, or glucagon in blood plasma or affect somatic cells in milk.