Influence of dietary calcium chloride on adaptive changes in acid-base status and mineral metabolism in lactating dairy cows fed a diet high in sodium bicarbonate

Eight mature, lactating Holstein cows were assigned to two treatments in a simple changeover design to examine physiological adaptations to dietary NaHCO3 over a 2-wk period. Treatments were diets containing, on a total diet DM basis, 1) 1.4% NaHCO3 and 2) 1.4% NaHCO3 with 1.3% CaCl2 substituted for limestone. Blood samples were collected hourly, and urine samples bihourly, for 8 h postfeeding on the 1st d of the experimental period and daily at 4 h post-feeding thereafter. Hourly analysis revealed that for most variables measured, the greatest response to dietary treatments occurred at or after 4 h post-feeding. Blood pH and blood HCO3- tended to be lower, and urinary excretion of chloride higher, on 1.4% NaHCO3 plus 1.3% CaCl2 throughout the trial. Blood HCO3- and blood partial pressure of CO2 fluctuated in response to the dietary treatments but functioned to maintain blood pH fairly constant. Plasma K concentration tended to increase during the experimental period on both treatments, but overall, plasma mineral concentration was relatively unresponsive to diet, and urinary mineral excretion was an excellent indicator of dietary mineral concentration. Inherent homeostatic mechanisms appear adequate to maintain a constant internal milieu when a high NaHCO3 diet is fed for 2 wk.     

Influence of calcium chloride on systemic acid-base status and calcium metabolism in dairy heifers

Twenty heifers (12 Holsteins and 8 Jerseys) ranging from 15 to 22 mo of age (SD = 2.2 mo) and weighing 271 to 486 kg (SD = 72 kg) were offered diets containing 0, .5, 1, and 1.5% CaCl2 for 3 wk followed by a 1-wk readjustment period to evaluate the effect of CaCl2 on acid-base status, diuresis, and Ca metabolism. These evaluations were conducted under conditions simulating changes in dietary cation-anion balance that potentially can be utilized as prophylaxis for parturient paresis during transition from dry cow period to lactation. Free proton concentration in blood increased and blood bicarbonate decreased with increasing dietary CaCl2. Plasma protein and blood hematocrit were unaffected by dietary CaCl2. Plasma Ca and urinary hydroxyproline excretion also were unaffected, but urinary Ca excretion rose with increasing dietary CaCl2, possibly reflecting either increased bone mobilization or intestinal absorption of Ca. Elevating dietary Cl increased both plasma Cl and urinary Cl excretion. During the readjustment period, all differences caused by CaCl2 disappeared. Based on the responses of acid-base status and Ca metabolism to the different dietary concentrations of CaCl2, we suggest that feeding 1% CaCl2 to dry cows for 3 wk prepartum could be a suitable method to prevent parturient paresis without causing detrimental acid-base disturbances.     

Influence of dietary sodium and potassium bicarbonate and total potassium on heat-stressed lactating dairy cows

Objectives were to study effects of heat stress, 0 or .85% sodium bicarbonate, 0 or 1.0% potassium bicarbonate, and 1.0 or 1.5% total dietary potassium on production and physiological responses of dairy cows. Eighteen lactating Holsteins were assigned to shade (control) or no shade (heat stress) lots continuously for three consecutive 35-day periods and to different dietary treatments each period. Basal diet was 25% cottonseed hulls and 75% concentrate. Daytime and nighttime feed intake and production were measured the last 2 wk of each period, and milk and blood were sampled the final day of each period. Black globe temperature, rectal temperature, respiration rate, and blood pH were higher in no shade. Daytime intake was 132% greater in shade, nighttime intake was not different between environments. Milk production was about 19% greater for evening and morning milkings in shade. Daytime intake, daytime and nighttime milk production were higher with sodium bicarbonate. Potassium bicarbonate reduced intake and production. Higher total dietary potassium increased total daily milk production. Lactating cows appear adept at withstanding environmental and dietary challenges to acid-base homeostasis. Supplementation of sodium bicarbonate and 1.5% dietary potassium, but not potassium bicarbonate, were beneficial to lactating dairy cows.     

Effect of exogenous bovine somatotropin on mammary lipid metabolism and milk yield in lactating dairy cows

Eight lactating Holstein cows were used to study the effect of bovine somatotropin on mammary lipid metabolism, milk production, and milk composition. Eight cows were injected with either excipient (n = 4) or 50 IU somatotropin/d (n = 4). A 2-wk adjustment period preceded a 10-d period when treatments were administered. On d 9, serial blood samples were collected from 2 to 5 h post-injection to determine concentrations of somatotropin and metabolites in plasma. Mammary tissue biopsies were obtained 2 to 3 h after a.m. milking on d 10 to determine lipoprotein lipase activity and in vitro rates of acetate incorporation into fatty acids and acetate oxidation by mammary tissue slices. Activity of lipoprotein lipase in milk and mammary tissue and rate of acetate metabolism by mammary tissue were not affected by treatment. The following means for placebo and somatotropin, respectively, were: milk production (21.5 and 24.8 kg/d), milk fat (3.8 and 4.0%), and 4% FCM (20.7 and 25.1 kg/d). Plasma concentrations of somatotropin (3.0 and 43.4 ng/ml) and free fatty acids (105.6 and 219.5 mu eq/L) were significantly elevated with somatotropin. The injection of somatotropin into lactating dairy cows did not affect the mechanisms of fatty acid synthesis or metabolism evaluated in this study.     

Long-acting insulins alter milk composition and metabolism of lactating dairy cows

This study investigated the effect of 2 different types of long-acting insulin on milk production, milk composition, and metabolism in lactating dairy cows. Multiparous cows (n = 30) averaging 88 d in milk were assigned to one of 3 treatments in a completely randomized design. Treatments consisted of control (C), Humulin-N (H; Eli Lilly and Company, Indianapolis, IN), and insulin glargine (L). The H and L treatments were administered twice daily at 12-h intervals via subcutaneous injection for 10 d. Cows were milked twice daily, and milk composition was determined every other day. Mammary biopsies were conducted on d 11, and mammary proteins extracted from the biopsies were analyzed by Western blot for components of insulin and mammalian target of rapamycin signaling pathways. Treatment had no effect on dry matter intake or milk yield. Treatment with both forms of long-acting insulin increased milk protein content and tended to increase milk protein yield over the 10-d treatment period. Analysis of milk N fractions from samples collected on d 10 of treatment suggested that cows administered L tended to have higher yields of milk protein fractions than cows administered H. Milk fat content and yield tended to be increased for cows administered long-acting insulins. Lactose content and yields were decreased by treatment with long-acting insulins. Administration of long-acting insulins, particularly L, tended to shift milk fatty acid composition toward increased short- and medium-chain fatty acids and decreased long-chain fatty acids. Plasma concentrations of glucose and urea N were lower for cows administered long-acting insulins; interactions of treatment and sampling time were indicative of more pronounced effects of L than H on these metabolites. Concentrations of nonesterified fatty acids and insulin were increased in cows administered long-acting insulins. Decreased concentrations of urea N in both plasma and milk suggested more efficient use of N in cows administered long-acting insulins. Western blot analysis of mammary tissue collected by biopsy indicated that the ratios of phosphorylated protein kinase b (Akt) to total Akt and phosphorylated ribosomal protein S6 (rpS6) to total rpS6 were not affected by long-acting insulins. Modestly elevating insulin activity in lactating dairy cows using long-acting insulins altered milk composition and metabolism. Future research should explore mechanisms by which either insulin concentrations or insulin signaling pathways in the mammary gland can be altered to enhance milk fat and protein production.     

Dietary sodium bicarbonate and magnesium oxide for early postpartum lactating dairy cows: effects on production, acid-base metabolism, and digestion

In two experiments with cows in early lactation fed 40% corn silage and 60% concentrate diets (dry basis), we examined effects of 1.0% dietary sodium bicarbonate and .8% magnesium oxide in a 2 x 2 factorial arrangement on performance, acid-base metabolism, and digestion. In Experiment 1 with 20 Holstein and 4 Jersey cows, intake and milk production were not affected by treatment through 12 wk postpartum. In digestion trials at 3, 6, 9, and 12 wk postpartum, addition of magnesium oxide increased digestibility of dry matter 1.8% units by sodium bicarbonate whereas acid detergent fiber digestion increased 9 to 12% units with addition of either buffer. In Experiment 2, with four fistulated Holstein cows in a Latin square design, intake per unit body weight was increased .18% units by dietary sodium bicarbonate while milk production was unaffected. Dry matter and acid detergent fiber digestion were increased slightly by sodium bicarbonate plus magnesium oxide addition whereas nitrogen balance increased 23 g/day in cows fed magnesium oxide alone. Because of the low fiber content of the ration, milk fat percent increased .5 to .9% by addition of either buffer in both experiments and resulted in corresponding increased in fat-corrected milk. Sodium bicarbonate and magnesium oxide prevented rapid declines in rumen pH associated with feeding in Experiment 2, which related to changes in acid detergent fiber digestion. Blood acid-base metabolites were relatively unchanged by treatment in either experiment. Urinary bicarbonate and net acid excretion rates were changed on the average by +41 and +43 meq/h by sodium bicarbonate or magnesium oxide but could not be related to changes in intake and production.     

Influence of niacin and whole cottonseed on intake, milk yield and composition, and systemic responses of dairy cows

Twenty-four Holstein cows (early postpartum) were used in a randomized complete block design with a 2 X 2 factorial arrangement of treatments to compare effects of nicotinic acid (niacin) and whole cottonseed. Cows were fed individually isonitrogenous complete mixed rations ad libitum, containing corn-soy concentrate, corn silage, chopped coastal bermudagrass hay, and either 1) 0% niacin and 0% whole cottonseed, 2) 0% niacin and 15% whole cottonseed, 3) .03% niacin and 0% whole cottonseed, or 4) .03% niacin and 15% whole cottonseed. Dry matter and energy consumption, actual milk yield, total milk solids, and milk fat yield were not affected by treatment. Either niacin or whole cottonseed increased milk fat percentage and 4% fat-corrected milk. Milk protein percentage and yield were higher with niacin supplementation but tended to be lower with cottonseed feeding. The milk protein depression with whole cottonseed was alleviated by niacin due to stimulation of mammary casein synthesis. Supplemental niacin tended to elevate glucose and insulin in blood plasma, but whole cottonseed tended to reduce these plasma components. Plasma urea nitrogen was higher in cows fed whole cottonseed. Plasma-free tryptophan tended to be slightly higher in cows receiving supplemental niacin.     

Effects of hot,humid weather on milk temperature,dry matter intake,and milk yield of lactating dairy cows

Lactating cows were exposed to moderate and hot, humid weather to determine the effect of increasing ambient temperature, relative humidity, or temperature-humidity index (THI) on intake, milk yield, and milk temperature. Minimum and maximum temperatures averaged 17.9 and 29.5 degrees C (cool period) and 22.5 and 34.4 degrees C (hot period), and minimum and maximum THI averaged 63.8 and 76.6 (cool period) and 72.1 and 83.6 (hot period). Environmental conditions had minor effects on intake and milk yield during the cool period. During the hot period, the THI 2 d earlier and mean air temperature 2 d earlier had the greatest impact on milk yield and DMI, respectively. Both breeds maintained milk temperature within normal ranges during the cool period, but Holstein and Jersey p.m. milk temperatures averaged 39.6 and 39.2 degrees C during the hot period. Current day mean air temperature during the hot period had the greatest impact on cow p.m. milk temperature, and minimum air temperature had the greatest influence on a.m. milk temperature. Dry matter intake and milk yield declined linearly with respective increases in air temperature or THI during the hot period and milk temperature increased linearly with increasing air temperature. Dry matter intake and milk yield both exhibited a curvilinear relationship with milk temperature. Environmental modifications should target the effects of high temperatures on cow body temperature and should modify the environment at critical times during the day when cows are stressed, including morning hours when ambient temperatures are typically cooler and cows are not assumed to be stressed.     

Effects of fatty acid supplements on milk yield and energy balance of lactating dairy cows

Saturated and unsaturated fatty acid supplements (FS) were evaluated for effects on yield of milk and milk components, concentration of milk components including milk fatty acid profile, and energy balance. Eight ruminally and duodenally cannulated cows and 8 noncannulated cows were used in a replicated 4 × 4 Latin square design experiment with 21-d periods. Treatments were control and a linear substitution of 2.5% fatty acids from saturated FS (SAT; prilled, hydrogenated free fatty acids) for partially unsaturated FS (UNS; calcium soaps of long-chain fatty acids). The SAT treatment did not change milk fat concentration, but UNS linearly decreased milk fat in cannulated cows and tended to decrease milk fat in noncannulated cows compared with control. Milk fat depression with UNS corresponded to increased concentrations of trans-10, cis-12 conjugated linoleic acid and trans C18:1 fatty acids in milk. Milk fat profile was similar for SAT and control, but UNS decreased concentration of short- and medium-chain FA. Digestible energy intake tended to decrease linearly with increasing unsaturated FS in cannulated and noncannulated cows. Increasing unsaturated FS linearly increased empty body weight and net energy gain in cannulated cows, whereas increasing saturated FS linearly increased plasma insulin. Efficiency of conversion of digestible energy to milk tended to decrease linearly with increasing unsaturated FS for cannulated cows only. Addition of SAT provided little benefit to production and energy balance, whereas UNS decreased energy intake and milk energy yield.     

Effect of feeding macerated alfalfa silage on nutrient digestibility and milk yield in lactating dairy cows

Five feeding studies were conducted with 141 lactating Holstein cows comparing macerated and control alfalfa silage harvested at two cuttings in each of 2 yr. Overall, silage made from macerated alfalfa contained more ash (suggesting improved soil contamination); greater fiber and lower nonprotein nitrogen (NPN) content suggested greater fermentation in the silo. In a digestion study, two diets were fed containing [dry matter (DM) basis] 72% of either control or macerated second-cutting alfalfa. Apparent digestibility of neutral detergent fiber and acid detergent fiber (ADF) was increased by maceration, and similar changes in digestibility were observed with Yb or indigestible ADF as marker; indigestible ADF was used as a marker in later studies. Lactation trials were conducted with first- and second-cutting alfalfa from each year. In each study, diets were formulated from alfalfa silage plus concentrate based on processed high moisture ear corn; mean compositions were (DM basis): negative control (61% control alfalfa silage), macerated (61% macerated alfalfa silage), and positive control (50% control alfalfa silage). All diets contained 2% crude protein from either roasted soybeans or low-solubles fish meal; soybean meal was added to make the positive control isonitrogenous (but not equal in ruminal undergraded protein). Milk yield was greater on macerated than negative control in two of four trials but not different in the other two trials. Yields of milk and milk components were not different between macerated and positive control in one of four trials. Versus the negative control, milk fat synthesis was depressed on macerated alfalfa in one trial. Overall performance on macerated versus negative control indicated greater apparent digestibility of organic matter (OM), greater yield of milk, protein, and solids not fat, but lower milk fat content. Yields of milk and milk components were greater overall on positive control versus macerated. Estimation of net energy for lactation (NEL) from maintenance, milk yield, and body weight gain indicated that control and macerated alfalfa silage contained, respectively, 1.36 and 1.42 Mcal of NEL of OM, an increase of about 5% due to maceration of alfalfa in these trials.     

Dietary cation-anion difference effects on performance and acid-base status of lactating dairy cows: a meta-analysis

A meta-analysis was conducted to examine potential empirical relationships between dietary cation-anion difference (DCAD) (Na + K - Cl) and the response of lactating dairy cows. The database was developed from 12 studies published between 1984 and 1997 that included a total of 17 trials, 69 dietary treatments, and 230 cows. Results indicated that DCAD affected performance of lactating dairy cows. Maximum milk yield and feed intake were reached when DCAD was 34 and 40 meq/100 g of feed dry matter, respectively. Blood pH and HCO3 concentrations increased with DCAD, indicating an improved acid-base balance of lactating dairy cows. Changes in urinary pH and urinary excretion of Na, K, and Cl were consistent with varying DCAD, thus dietary acidity or alkalinity. The effects of DCAD were likely mediated via modification of acid-base status in the cows.     

Effects of sodium carbonate on milk yield, milk composition, and blood components of dairy cows in early lactation

Eighteen multiparous Friesian cows were paired according to lactation number and expected calving date and assigned randomly to one of two diets in a crossover design experiment to study effects of sodium carbonate on milk yield, milk composition, blood metabolites plus Na, and K in early lactation. Diets were concentrate containing either 0 or 1.2% sodium carbonate (as fed) for ad libitum intake plus 7.0 kg of wet brewers grains and 5.5 kg of long-stemmed alfalfa hay per cow daily. Dry matter intake, milk yield, milk protein percentage and yield, and percentages of milk lactose and milk SNF were not significantly affected. Compared with the control diet, the sodium carbonate treatment increased milk fat percentage (3.98 vs. 3.53%) and yield (1.23 vs. 1.07 kg/d), 4% FCM yield (30.9 vs. 28.2 kg/d) and milk total solids (12.47 vs. 12.04%). No significant differences were observed in blood plasma concentrations of glucose, CP, urea, acetate, beta-hydroxybutyrate, triglycerides, FFA, Na, or K when sodium carbonate was added to diets for early lactation cows.     

Effects of dietary fiber on intake, milk yield, and digestion by lactating dairy cows during cool or hot, humid weather

Lactating cows were offered diets with increasing neutral detergent fiber concentrations to determine the effects on intake, milk yield and composition, blood hormones, and nutrient digestion during cool or hot weather conditions. Tifton 85 bermudagrass hay was substituted for corn silage so that the forage portion of diets were: 1) 40% corn silage (control), 2) 32.4% corn silage, 7.6% bermudagrass, 3) 24.8% corn silage, 15.2% bermudagrass, or 4) 17.2% corn silage, 22.8% bermudagrass (dry basis). Dietary neutral detergent fiber concentrations (% dry matter) were 30.2, 33.8, 37.7, and 42.0, respectively. Intake of dry matter declined with increasing dietary neutral detergent fiber during cool and hot periods, but intake adjusted for cool weather treatment differences did not change further during hot weather. Milk yield declined linearly with increasing neutral detergent fiber during cool weather and changed quadratically during hot weather. Milk temperature declined with increasing dietary neutral detergent fiber for the p.m. milking during the cool period and declined with increasing dietary neutral detergent fiber for the a.m. and p.m. milkings during the hot period. Digestibility of neutral detergent fiber improved and ruminal turnover of particulate digesta was increased with greater dietary neutral detergent fiber content. No dietary fiber level by hot weather interaction was observed, suggesting that total energy intake may have and a greater effect on milk yield than dietary fiber content during hot, humid weather.     

Effects of intraruminal infusion of sodium,potassium, and ammonium on hypophagia from propionate in lactating dairy cows

The objective of this experiment was to evaluate effects of salt type on hypophagic effects of intraruminal infusion of propionate in lactating dairy cows. Our working hypothesis is that oxidative metabolism of propionate causes satiety by increasing hepatic ATP concentration and decreasing the discharge rate of the hepatic vagus. We hypothesized that hypophagic effects of propionate are reduced by ammonium and potassium. We speculated that ammonium infusion lowers hepatic ATP concentration because ATP is used for urea synthesis and potassium increases the discharge rate of the hepatic vagus. Eight ruminally cannulated Holstein cows in midlactation were used in a duplicated 4 x 4 Latin square design experiment. Treatments were intraruminal infusion of propionic acid, ammonium propionate, sodium propionate, and potassium propionate. Treatment solutions were 0.93 M for propionate and 0.67 M for salts among the treatments except for propionic acid. Treatment solutions were infused over 14 h starting 2 h before feeding at 17.9 ml/min, which is equivalent to 16.7 and 11.9 mmol/min for propionate and salts, respectively. Infusion of ammonium propionate decreased dry matter intake compared with sodium propionate and potassium propionate (P < 0.04; 11.0 vs. 14.0 and 13.9 kg/12 h) by decreasing meal frequency without affecting meal size, indicating that ammonium delayed the sense of hunger. No difference in DMI and feeding behavior was observed between infusion of sodium and potassium propionate. Contrary to the hypothesis, ammonium infusion did not reduce hypophagic effects of propionate, possibly because the urea cycle indirectly stimulated oxidative metabolism in the liver by generating oxidizable carbon from amino acid catabolism.     

Effects of sodium bicarbonate and sodium sesquicarbonate on animal performance, ruminal metabolism, and systemic acid-base status

Six rumen-fistulated lactating Holstein cows were arranged in a replicated 3 x 3 latin square design with 3-wk periods and offered diets containing concentrate and corn silage in a 60:40 ratio (DM basis). Treatments were: 1) basal diet, 2) basal diet with 1% NaHCO3, and 3) basal diet with 1% sodium sesquicarbonate. There were no differences among treatments in milk production, milk protein, or 3.5% FCM, but sodium sesquicarbonate increased milk fat percentage (3.89, 3.94, 4.06%) compared with that of the control. Rumen pH was higher for cows fed buffered diets than for control cows. Urine pH was higher for cows fed NaHCO3 diet than for those fed sodium sesquicarbonate and control diets. No differences were detected among treatment means for molar percentage of isobutyrate, isovalerate, or total VFA, Dietary sesquicarbonate addition increased molar percentage of acetate, decreased propionate, and resulted in a higher acetate:propionate ratio compared with the cows fed NaHCO3. However, molar percentage of butyrate and valerate decreased in cows fed sodium sesquicarbonate when compared with those fed the control diet. No differences among treatment means were detected for blood pH, pCO2, or HCO3.     

Effects of milk fever, ketosis, and lameness on milk yield in dairy cows

The effects of milk fever, ketosis, and lameness were studied using data from 23,416 Finnish Ayrshire cows that calved in 1993 and were followed for one lactation (i.e., until culling or the next calving). Monthly test day milk yields were treated as repeated measurements within a cow in a mixed model analysis. Disease index variables were created to relate the timing of a disease to the measures of test day milk. Statistical models for each parity and disease included fixed effects of calving season, stage of lactation, and disease index. An autoregressive correlation structure was used to model the association among the repeated measurements. The milk yield of cows contracting milk fever was affected for a period of 4 to 6 wk after calving; the loss ranged from 1.1 to 2.9 kg/d, depending on parity and the time elapsed after milk fever diagnosis. Despite the loss, cows with milk fever produced 1.1 to 1.7 kg more milk/d than did healthy cows. Milk yield started to decline 2 to 4 wk before the diagnosis of ketosis and continued to decline for a varying time period after it. The daily milk loss was greatest within the 2 wk after the diagnosis, varying from 3.0 to 5.3 kg/d, depending on parity. Cows in parity 4 or higher were most severely affected by ketosis; the average total loss per cow was 353.4 kg. Lameness also affected milk yield; milk loss of cows diagnosed with foot and leg disorders varied between 1.5 and 2.8 kg/d during the first 2 wk after the diagnosis.     

Effects of dietary cation-anion difference and potassium to sodium ratio on lactating dairy cows in hot weather

Forty-two lactating Holstein cows 188 ± 59 d in milk were used in an 8-wk randomized complete block trial with a 2 × 3 factorial arrangement of treatments. The objective was to determine the effects of high dietary cation-anion difference (DCAD) and K:Na ratio on milk yield and composition and blood acid-base chemistry. Treatments included DCAD concentrations of 45 or 60 mEq (Na + K −Cl)/100 g of feed dry matter and K:Na ratios of 2:1, 3:1, or 4:1. Mean DCAD values were later determined to be 41 and 58. Dry matter intake was similar across treatments. Yield of milk and energy corrected milk were lower for the 3:1 K:Na ratio compared with 2:1 and 4:1 ratios. Blood urea N was lower for the highest DCAD, suggesting that DCAD possibly reduced protein degradation or altered protein metabolism and retention. Mean temperature-humidity index was 75.6 for the duration of the trial, exceeding the critical value of 72 for all weeks during the treatment period. Cows maintained relatively normal body temperature with mean a.m. and p.m. body temperature of 38.5 and 38.7°C, respectively. These body temperatures suggest that cows were not subject to extreme heat stress due to good environmental control. Results of this trial indicate that the greatest effect on milk yield occurs when either Na or K is primarily used to increase DCAD, with the lowest yield of energy-corrected milk at a 3:1 K:Na ratio (27.1 kg/d) compared with ratios of 2:1 (29.3 kg/d) and 4:1 (28.7 kg/d). Results also suggest that greater DCAD improves ruminal N metabolism or N utilization may be more efficient with a high DCAD.     

The effects of milk yield and stage of lactation on the partitioning of nutrients in lactating dairy cows

The objective of the experiment was to examine, using indirect calorimetry, the effects of milk yield and stage of lactation on the response in milk and body tissue energy, and heat production, to a reduction (decrement) in nutrient intake (assessed as metabolizable energy intake). Eight lactating dairy cows, four representing each of two stages of lactation [either mean initial days in milk (DIM) 158 (SD 6.1) or 414 (SD 51.1)] were used. Each cow underwent four 17-d periods incorporating two physiological states [number of mammary glands milked: either four (periods 1 and 2), or two (periods 3 and 4)], and two levels of metabolizable energy intake within each physiological state [either sufficient to meet requirements for zero tissue balance plus 10 MJ/d (periods 1 and 3)] or these allowances reduced by 20 MJ/d in the subsequent period (periods 2 and 4, respectively). Partitioning was calculated from the changes in metabolizable energy intake, milk energy, tissue energy, and heat production between DIM groups and between four and two gland milking (milk yield) components of the study. Partitioning of the changes in metabolizable energy intake was not influenced by DIM, but milk yield response was greater in the early lactation cows compared with the late group. Cows milked in four glands (higher milk yield) partitioned a significantly greater proportion of decremental changes in metabolizable energy intake to milk energy and less to tissue energy, than when milked in only two glands (lower milk yield).     

Supplemental feeding with glycerol or propylene glycol of dairy cows in early lactation--effects on metabolic status, body condition, and milk yield

The objective of this field study was to evaluate the effect of supplemental feeding with glycerol or propylene glycol to dairy cows in early lactation on metabolic status, body condition and milk yield. In total, 673 newly calved cows from 12 commercial Swedish dairy herds were randomized to daily supplementation with 450 g of glycerol (GLY), 300 g of propylene glycol (PG), or nothing (control, CON). Supplements were fed twice daily from 0 to 21 d in milk (DIM) as a top dress on concentrates. For each cow, data on parity, breed, calving date, monthly test-day milk yield, and cases of diseases were collected. Blood samples were taken at approximately 2, 5, and 8 wk postpartum (pp) and analyzed for glucose, β-hydroxybutyrate (BHBA), nonesterified fatty acids (NEFA), and insulin. Samples taken within 3 wk pp were also analyzed for insulin-like growth factor 1 (IGF-1). Measurements of body condition score (BCS) and heart girth (HG) were obtained at approximately 2 and 5 wk pp and at time of first insemination. The effects of supplemental feeding with GLY or PG on the plasma concentrations of glucose, NEFA, BHBA, insulin, and IGF-1, and BCS, HG, and occurrence of disease were analyzed. No differences in BCS or HG or in plasma concentrations of glucose, BHBA, NEFA, or IGF-1 were found between the control group and any of the treatment groups. Cows in the GLY group had lower plasma insulin concentrations during DIM 0 to 63 compared with group CON, but no difference in insulin was found between the PG group and the CON group. Cows supplemented with GLY had a higher milk yield (kg of milk and kg of energy-corrected milk) during the first 90 DIM. Cows in the PG group tended to yield more milk during the same period. No differences in the occurrence of diseases were seen between the groups. In conclusion, supplementation with GLY in early lactation did increase milk yield without a subsequent decrease of metabolic status, and supplementation with PG tended to do the same.     

Comparison of claw health and milk yield in dairy cows on elastic or concrete flooring

This article reports on the effects of elastic (rubber) flooring compared with concrete flooring on claw health and milk yield in dairy cows. Milk yield and activity data of 53 complete lactations from 49 cows were recorded by an automatic milking system in the University of Munich Livestock Center dairy herd. Cows were kept in a loose housing system on concrete-slatted or rubber-matted slatted flooring. Claws were trimmed and measured linearly in combination with claw lesion diagnosis 3 times during one lactation period (including the transition phase). An automatic milking system recorded milk yield and activity. The net horn growth of the claws increased on elastic flooring. Therefore, correct and frequent claw trimming is at least as important for claw health in dairy herds kept on rubber flooring as for those on concrete-slatted flooring. Cows housed on rubber had an increased incidence of sole ulcers. Sole hemorrhages (except for hemorrhages associated with sole ulcers) occurred less frequently on rubber than on concrete. Results concerning digital dermatitis were difficult to assess, because manual manure scraping on rubber required sprinkling the flooring twice daily, which additionally moistened the digital skin of the cows. This might explain the greater incidence of digital dermatitis on elastic flooring. The incidence of clinically lame cows did not differ between flooring types. Cows showed greater activity on rubber, most likely caused by the more comfortable walking surface compared with the concrete-slatted flooring. The greater activity may indicate better overall health of high-yielding dairy cows on rubber flooring. Milk yield, however, did not differ between flooring types.