Effects of increasing days of exposure to prepartum transition diets on milk production and milk composition in dairy cows

Objective To evaluate the effects of length of exposure to prepartum transition diets on milk yield, fat and protein production. Design Prospective cohort study. The number of days that the cows were fed the prepartum transition diets was the exposure of interest. Procedures Holstein and Holstein x Jersey cows (n = 1008) were enrolled. Diets given in the far-off dry period (from end of lactation until approximately 3 weeks before expected parturition) consisted of ad libitum access to perennial ryegrass pastures. Prepartum transition diets included perennial ryegrass pasture, ryegrass silage, cereal hay, grain, grain by-product, protein meals, BioChlor(R), sodium monensin, virginiamycin or tylosin, MgSO(4), trace elements and vitamins. On a dry matter basis, these contained 16.0% crude protein, 4.2% rumen undegradable protein, and 9.9 mJ metabolisable energy/kg. Diets provided an estimated metabolisable protein balance of 286 g/day and dietary cation anion difference of -150 meq/kg dry matter. Statistical models controlled for effects of herd, calving day, breed, age and gestation period. Results Increasing length of exposure to the prepartum transition diets significantly increased the 4.0% fat- and 3.2% protein-corrected milk yield and milk-protein yield as a linear and quadratic effect. The optimal duration of exposure to the prepartum transition diets was 25 days for fat- and protein-corrected milk production and 22 days for milk protein production. Milk-fat percentage decreased significantly and linearly with increasing exposure to the prepartum transition diets; however, milk-fat yield or milk-protein percentage did not vary significantly with duration of exposure to the diets. Conclusions Increasing exposure to prepartum transition diets increased milk and milk-protein yields and decreased the milk fat-percentage, but not the milk-protein percentage or milk-fat yield. Aust Vet J 2008;86:341-351.     

Effect of prepartum compensatory nutrition regimen on metabolism and performance of dairy cows

The impact of closely controlled energy management during the dry period upon general peripartum metabolism and the subsequent lactation was evaluated in multiparous dairy cows. Eight lactating, pregnant Holstein cows were paired according to current milk production and body condition score and assigned to either the control or the stair-step compensatory nutrition (SSCN) regimen 16 weeks prior to expected calving date. Control cows were fed according to National Research Council [National Research Council., 2001. Nutrient Requirements of Dairy Cattle. 7th rev. ed. Natl. Acad. Sci., Washington, DC.] recommendations and for ad libitum intake during late lactation and the far-off dry period. The SSCN cows were subjected to dietary energy restriction [80% of net energy for lactation requirements (NE_L)] during late lactation in order to maintain body weight, followed by realimentation (130% of NE_L) during the far-off dry period to induce a compensatory response. A common diet was fed thereafter. The SSCN cows gained less body condition during late lactation and tended to gain more body condition during the far-off dry and transition periods than control cows. There was no difference in dry matter intake during the prepartum transition period and early lactation. Milk yield was not affected by treatment. Serum nonesterified fatty acids (NEFA) were not altered by dietary treatment during late lactation and the dry period; however NEFA were lower in SSCN cows at week 4 of the subsequent lactation. Serum insulin was higher in SSCN cows 8 weeks prior to parturition (end of restriction), tended to be higher at 4 weeks (end of realimentation) before calving, and was also higher at week 12 of early lactation. An SSCN regimen stimulated body condition gain of mature dairy cows during the dry period, did not affect periparturient nutrient metabolism, and led to modest improvements in metabolic parameters later in the subsequent lactation.     

Effect of reduced energy density of close-up diets on dry matter intake,lactation performance and energy balance in multiparous Holstein cows

Energy intake prepartum is critically important to health,milk performance,and profitability of dairy cows.The objective of this study was to determine the effect of reduced energy density of close-up diets on dry matter intake(DMI),lactation performance and energy balance(EB) in multiparous Holstein cows which were housed in a free-stall bam and fed for ad libitum intake.Thirty-nine dry cows were blocked and assigned randomly to three groups fed a high energy density diet[HD,n = 13;6.8 MJ of net energy for lactation(NE_L)/kg;14.0%crude protein(CP)],or a middle energy density diet(MD,n = 13;6.2 MJ NE_L/kg;14.0%CP),or a low energy density diet(LD,n = 13;5.4 MJ NE_L/kg;14.0%CP) from d 21 before expected day of calving.After parturition,all cows were fed the same lactation diet to d 70 in milk(DIM).The DMI and NE_L intake prepartum were decreased by the reduced energy density diets(P 0.05).The LD group consumed 1.3 kg/d(DM) more diet compared with HD group in the last 24 h before calving.The milk yield and the postpartum DMI were increased by the reduced energy density diet prepartum(P 0.05).The changes in BCS and BW prepartum and postpartum were not affected by prepartum diets.HD group had higher milk fat content and lower lactose content compared with LD group during the first 3 wk of lactation(P 0.05).The energy consumption for HD,MD and LD groups were 149.8%,126.2%and 101.1%of their calculated energy requirements prepartum(P 0.05),and 72.7%,73.1%and 75.2%during the first 4 wk postpartum,respectively.In conclusion,the low energy density prepartum diet was effective in controlling NE_L intake prepartum,and was beneficial in increasing DMI and milk yield,and alleviating negative EB postpartum.     

Reduced energy density of close‐up diets decrease ruminal pH and increase concentration of volatile fatty acids postpartum in Holstein cows

The objective of this study was to determine the effect of reduced energy density of close‐up diets on ruminal fermentation parameters in transition cows. Fourteen Holstein dry cows were blocked and assigned randomly to three groups fed a high energy density diet (HD, 1.62 Mcal of net energy for lactation (NE_L)/kg dry matter (DM)), or a middle energy density diet (MD, 1.47 Mcal NE_L/kg DM), or a low energy density diet (LD, 1.30 Mcal NE_L/kg DM) prepartum, and were fed the same diet postpartum. The reduced energy density diets decreased the average dry matter intake (DMI) prepartum and tended to increase the DMI postpartum. The ruminal pH of the LD group was significantly higher prepartum and lower during the first week of lactation compared with the other two groups. The reduced energy density diet depressed the average ruminal concentration of propionate and butyrate prepartum, and increased the average concentration of total volatile fatty acids (VFA) postpartum. The LD group had higher populations of Butyrivibrio fibrisolvens and Ruminococcus flavefaciens relative to HD and MD groups on 7 days in milk. In conclusion, the cows fed reduced energy density diet prepartum had higher VFA concentration, but were more susceptible to subacute ruminal acidosis postpartum.     

Wheat grain as a prepartal cereal choice to ease metabolic transition from gestation into lactation in Holstein cows

Wheat grain (WG) is a unique cereal rich in easily fermentable starch and low in cation–anion difference (e.g. 5.3 mEq/100 g). The controlled prepartal dietary inclusion of WG, thus, has the potential to ease adapting the rumen microbes and papillae to the high‐starch lactation diets, stimulate feed intake, reduce hypocalcaemia by reducing extracellular alkalinity and a moderate induction of bone resorption, and improve milk yield in periparturient cows. The primary objective was to determine the effects of prepartal feeding of WG compared to barley grain plus wheat bran on metabolic and productive criteria in periparturient Holstein cows. Twenty‐four dry cows and 16 pregnant heifers were blocked based on parity and projected calving date and fed a prepartal diet containing either (i) ground WG (18% on a dry matter basis) or (ii) a conventional diet with ground barley grain and wheat bran or control diet, from 28‐day prepartum until parturition. All cows were fed the control diet during 21‐day postpartum. Prepartal dietary inclusion of WG increased prepartum feed intake, elevated blood glucose and attenuated hypocalcaemia at 7‐day prepartum and 1‐day postpartum, reduced urine pH, and increased milk fat percent and yield. Blood proteins at 7‐day prepartum were higher and placenta tended to be expelled sooner in WG‐fed cows than in other cows. Treatments did not affect milk protein, changes in body condition score; total time spent eating, ruminating and chewing; blood levels of urea nitrogen, cholesterol, and phosphorous, fecal pH, and calving difficulty. Therefore, the prepartal dietary use of WG proved effective in the simultaneous improvement of calcium and energy states, and thereby, in easing the metabolic transition from gestation into lactation in Holstein cows.     

Effects of an immunomodulatory feed additive on body weight,production parameters,blood metabolites,and health in multiparous transition Holstein cows

The study investigated the impact of feeding OmniGen‐AF^® (OG; Phibro Animal Health, Quincy, IL) from dry‐off to week 4 of lactation at two doses on production performance and metabolic adaptation of multiparous Holstein cows. Forty‐eight cows were blocked and assigned randomly to three treatments: OG was fed at 0 g/head/day (CON), 60 g/head/day (OG60), or 90 g/head/day (OG90). No difference was observed in dry matter intake (DMI) throughout the experiment, whereas feeding OG tended to decrease the percentage body weight change (PWC) on week 2. Although colostrum yield was not affected by treatment, colostrum IgG production of OG90 tended to be higher than that of CON. OG supplementation did not affect overall milking performance but decreased milk SCC during the first 4 weeks of lactation. In prepartum, OG supplementation decreased the concentrations of serum albumin and calcium, and increased serum globulin. OG supplementation tended to increase serum total protein, globulin, and calcium contents postpartum. Furthermore, reduced incidence of mastitis and udder edema were observed. In conclusion, supplementing cows with OG from dry‐off period reduces or modulates the inflammation responses associated with parturition, potentially resulting in improved postpartum health, while feeding OG more than 60 g/head/day did not warrant further benefits.     

Effect of fat supplementation during transition period on plasma leptin and non‐esterified fatty acid concentrations in Holstein cows

The objective of this experiment was to investigate the effect of fat supplementation during the transition period on pre and postpartum body weight (BW), body condition score (BCS), non‐esterified fatty acids (NEFA), glucose and leptin concentrations in Holstein cows. Holstein cows (n = 15) received a low fat diet (LF; 1.61 Mcal net energy for lactation (NEL)/kg of dry matter [DM]), moderate fat diet (MF; 1.68 Mcal NEL/kg DM) or a high fat diet (HF; 1.74 Mcal NEL/kg DM) for 4 weeks prior to calving. All cows were fed similar lactation diets ad libitum (1.74 Mcal NEL/kg DM) for 30 days after calving. Increasing diet energy density during transition period had no effect on prepartum DMI, BCS, BW, glucose and NEFA concentrations (P > 0.05); but leptin concentrations and energy balance (EB) were affected by treatments (P < 0.05). Animals fed HF had less plasma leptin prepartum. After parturition, BW, milk production, milk fat, protein, urea nitrogen and plasma glucose concentrations were affected by prepartum diets (P < 0.05). Fat supplementation prepartum did not affect postpartum NEFA. In conclusion, prepartum fat supplementation decreased leptin concentration prepartum.     

The impact of cow nutrition in the dry period on colostrum quality and immune status of calves

The objective of the study was to evaluate the effect of energy contents in a dry period diets in "7+1" feeding strategy of dry cow including 7 weeks of the dry period (far-off) and 1 week of a close-up period, on colostrum quality and the immune status of calves. Forty Holstein multiparous cows were dried at 56d before the expected date of calving and were assigned to the higher energy diet group (HE; 0.69 UFL/kg DM, NDF 52% DM), or the lower energy diet group (LE; 0.61 UFL/1kg DM, NDF 56% DM). From -7d to the expected calving date up to 21 d of lactation, all cows were fed the same fresh, lactation diet. Samples of colostrum were collected within 2h after parturition and its density, dry matter content and concentrations of immunoglobulins, fat, protein, lactose, urea and somatic cell counts were measured. Calves were weighed 2 h after calving and on the 21d of life. On 3d and 21d of calves' life blood samples were collected and the concentration of IgG, IgA, IgM, insulin-like growth factor 1 (IGF-1) as well as total protein and albumin concentrations were determined. Treatments had no significant effect on composition of colostrum and serum immunoglobulins and IGF-1 concentration. In both groups the weight of calves at birth was similar, still daily body weight gain during 21 day of rearing period in HE group was higher than in the LE group (P=0.05).     

干奶期不同能量摄入水平对产后奶牛生产性能的影响

将围产期健康奶牛30头随机分为3组．分别于产前28d开始饲喂NRC标准日粮（能量摄入100％组）、NRC标准增加20％日粮（能量摄入120％组）和NRC标准减少20％日粮（能量摄入80％组）．产后各组奶牛均饲喂标准日粮，至产后56d结束，观察干奶期不同能量摄入水平对产后奶牛生产性能的影响。结果表明，高能量组奶牛产后干物质采食量和产奶量均显著低于其他2组，并且体质量消耗明显。由此认为，干奶期能量摄入水平是影响和调节产后干物质摄入量、产乳量和能量平衡状态的重要因素。     

Effects of different starch sources on metabolic profile, production and fertility parameters in dairy cows

The objective of the study was to determine the effect of replacing triticale (high rumen degradable starch) with maize grain (low rumen degradable starch) during the transition period and the first 120 days of lactation on metabolic and hormonal profile indices, milk production and fertility performance in cows. Forty-eight Holstein-Friesian dairy cows were divided into 4 groups: TT (2.5 kg triticale grain/cow per day supplemented from 14 days prepartum to day 120 postpartum), TM (2.5 kg triticale grain/cow per day supplemented from day 14 before parturition to calving, and then 2.5 kg maize grain to 120 days of lactation), MT (2.5 kg maize grain/cow per day supplemented from day 14 before parturition to calving, and then 2.5 kg triticale grain to 120 days of lactation), MM (2.5 kg maize grain/cow per day supplemented from 14 days prepartum to day 120 postpartum). Blood samples were collected 3 weeks and 1 week before calving and on days 14, 56 and 70 of lactation, and they were analyzed in terms of concentrations of glucose, insulin, leptin, insulin-like growth factor I, nonesterified fatty acids, triglycerides, cholesterol, blood urea nitrogen and activities of aspartate aminotransferase and gamma glutamyl transpeptidase. Milk samples were collected twice a day at weekly intervals and analyzed for fat, protein and lactose. Milk yield and individual dry mater intake were recorded at weekly intervals. Body condition was estimated 3 weeks before calving, on parturition day and on days 14, 56 and 120 of lactation. Replacing triticale grain with maize grain in the transition period and during lactation positively affected fertility of lactating cows. An increased first service conception rate and shortening of the days open period was observed in MM and TM groups in comparison to those found in group MT (P < or = 0.05). The lowest number of services per conception was recorded in groups MM and TM (P < or = 0.05). Although the impact of milk production and the most of the blood indices were not significantly affected by this treatment, the results of the study suggest that maize grain in the transition period and lactation might be a more effective energy source for dairy cows than triticale grain.     

Stability of plasma metabolites and hormones in parturient dairy cows

Metabolic changes that accompany the transition from parturition to lactation in dairy cows were studied. To measure these changes, plasma samples were obtained from 20 mature Holstein-Friesian dairy cows 10 days before through 10 days after parturition. They were analyzed for glucose, free fatty acids (FFA), lactic acid, ketone bodies, glucocorticoids, insulin, and growth hormone concentration. Lactic acid and glucocorticoids remained constant during the experiment, except for the day of parturition itself. In the prepartum period, changes were not detected in concentrations of hormones (glucocorticoids, insulin, and growth hormone), whereas, plasma metabolites began changing prior to parturition. Most evident were prepartum increased in FFA, ketones, and glucose. Postpartum plasma glucose concentration rapidly returned to prepartum concentrations. Plasma concentration of FFA and ketone bodies remained elevated for longer periods.     

Association of rumen fill score and energy status during the close‐up dry period with conception at first artificial insemination in dairy cows

Recent studies have shown significant associations between prepartum energy status and postpartum fertility in dairy cows; therefore, the assessment of energy status by blood metabolites and metabolic hormones and suitable improvement of management during the prepartum period may enhance reproductive performance. Rumen fill score (RFS) is associated with feed intake; however, it is unknown whether RFS is also related to blood parameters. Therefore, this study investigated the relationship between RFS and energy status during the prepartum period, and their associations with conception at first artificial insemination (AI) after parturition. In 42 multiparous Holstein cows, RFS assessment and blood sampling were carried out twice a week during 3 weeks of the peripartum period. Ovarian cycles until AI were evaluated by measuring milk progesterone levels. Before calving, positive correlations were observed between RFS and total cholesterol, and RFS did not change in pregnant cows at first AI after parturition, whereas in non‐pregnant cows, RFS decreased gradually as the calving day approached. After calving, non‐pregnant cows showed lower energy status compared with pregnant cows, and some non‐pregnant cows showed anovulation and cessation of estrous cycle. In conclusion, RFS during the close‐up dry period is related to real‐time energy status, and is associated with postpartum energy status and conception at first AI in dairy cows. © 2016 Japanese Society of Animal Science     

干奶期不同能量摄入对围产期乳牛血液葡萄糖胰高血糖素和胰岛素浓度的影响

将围产期健康乳牛30头随机分为3组，分别于产前第28d开始饲喂标准日粮（能量摄入i00％组）、标准日粮增加20％的日粮（能量摄入120％组）和标准日粮减少20％的日粮（能量摄入80％组），产后备组乳牛均饲喂标准泌乳日粮，至产后第56d结束，观察干奶期不同能量摄入水平对围产期健康乳牛血液葡萄糖、胰高血糖素和胰岛素浓度的影响。结果表明，产前低能饲喂可以增加围产期乳牛血浆葡萄糖浓度，干奶期不同能量摄入水平对围产期健康乳牛血液葡萄糖、胰高血糖素和胰岛素浓度起重要调节作用。     

不同能量摄入水平对奶牛产乳性能及血液中Leptin和NPY浓度的影响研究

将30头围产期健康奶牛随机分为3组,每组均为10头,其中Ⅰ组为对照组,Ⅱ组和Ⅲ组为试验组;Ⅰ、Ⅱ、Ⅲ组分别于产前第28d开始饲喂标准日粮(能量摄入100%组)、标准日粮增加20%能量(能量摄入120%组)和标准日粮减少20%能量(能量摄入80%组),产后各组奶牛均饲喂标准泌乳日粮,至产后第56d结束,观察不同能量摄入水平对产后奶牛产乳性能及血液中瘦素(Leptin)和神经肽Y(NPY)浓度的影响。试验结果表明,产前饲喂低能日粮不仅提高了产后奶牛产乳性能,而且提高了产后奶牛血液中Leptin和NPY浓度。可见,奶牛不同能量摄入水平与产奶量及血液中Leptin和NPY浓度之间存在着密切的关系。     

Effect of reduced energy density of close-up diets on dry matter intake,lactation performance and energy balance in multiparous Holstein cows

Energy intake prepartum is critically important to health, milk performance, and profitability of dairy cows. The objective of this study was to determine the effect of reduced energy density of close-up diets on dry matter intake (DMI), lactation performance and energy balance (EB) in multiparous Holstein cows which were housed in a free-stall barn and fed for ad libitum intake. Thirty-nine dry cows were blocked and assigned randomly to three groups fed a high energy density diet [HD, n = 13; 6.8 MJ of net energy for lactation (NE_L)/kg; 14.0% crude protein (CP) ], or a middle energy density diet (MD, n = 13; 6.2 MJ NE_L/kg; 14.0% CP), or a low energy density diet (LD, n = 13; 5.4 MJ NE_L/kg; 14.0% CP) from d 21 before expected day of calving. After parturition, all cows were fed the same lactation diet to d 70 in milk (DIM). The DMI and NE_L intake prepartum were decreased by the reduced energy density diets (P < 0.05). The LD group consumed 1.3 kg/d (DM) more diet compared with HD group in the last 24 h before calving. The milk yield and the postpartum DMI were increased by the reduced energy density diet prepartum (P < 0.05). The changes in BCS and BW prepartum and postpartum were not affected by prepartum diets. HD group had higher milk fat content and lower lactose content compared with LD group during the first 3 wk of lactation (P < 0.05). The energy consumption for HD, MD and LD groups were 149.8%, 126.2% and 101.1% of their calculated energy requirements prepartum (P < 0.05), and 72.7%, 73.1% and 75.2% during the first 4 wk postpartum, respectively. In conclusion, the low energy density prepartum diet was effective in controlling NE_L intake prepartum, and was beneficial in increasing DMI and milk yield, and alleviating negative EB postpartum.     

干奶期奶牛不同能量摄入对其肝脏胰岛素受体mRNA表达的影响

将健康围产期奶牛30头随机分为3组,预产前28 d分别饲喂奶牛标准日粮（能量摄入100%组）、标准日粮增加20%日粮（能量摄入120%组）和标准日粮减少20%日粮（能量摄入80%组）,产后各组奶牛均饲喂标准的产奶日粮,至产后56d结束,采用半定量RT-PCR方法,观测干奶期不同能量摄入水平对围产期健康奶牛肝脏胰岛素受体（IR）基因表达的影响.试验结果表明,干奶期低能饲喂奶牛,产后肝脏IR mRNA表达增加,提示低能饲喂有利于调节奶牛产后血糖平衡.     

干奶期不同能量水平对奶牛血中神经肽 Y和生长激素浓度的影响

将健康围产期奶牛30头随机分为3组．预产前28d按奶牛营养需要分别饲喂100％、120％、80％能量日粮，产后各组奶牛均饲喂标准的产奶日粮，至产后56d结束，观测干奶期不同能量摄入水平对围产期健康奶牛血中神经肽Y和生长激素浓度的影响。结果表明，干奶期低能量日粮饲喂，奶牛血中神经肽和生长激素浓度均高于其他2组，从产前14d至产后28d组间差异显著（P〈0.01；P〈0.05），提示低能量饲料饲喂干奶期奶牛，产后能量负平衡得到缓解。     

Effects of forage-to-concentrate ratio in prepartum diet on the dry matter intake and milk yield of periparturient cows during hot weather

The objective of this experiment was to study the effect of prepartum diets on dry matter intake (DMI) around parturition and on milk production in early lactation during a hot summer. Nine cows due to calve in July or August were assigned to two groups and fed either control (group C; four cows) or high‐concentrate (group H; five cows) diets to meet 110% of their energy requirements from 18 days before the expected calving date to parturition. The proportion of concentrate in the control diet was 35%, and that in the high‐concentrate diet was 45%. For 21 days after parturition, all cows were fed the same diets for lactation ad libitum. The DMI of cows in group H almost met their energy requirements. In group C, the DMI was decreased relative to group H and the concentration of plasma non‐esterified fatty acids was significantly higher (P < 0.05) before parturition. Therefore, the cows in group C were thought to be energy deficient before parturition. After parturition, there were no significant differences in DMI between the two groups. The milk yield of cows in group H tended to be higher than that of cows in group C at 21 days after parturition. Milk protein yield was significantly higher (P < 0.05) in group H 21 days after parturition relative to group C. There were no significant differences in milk composition between the two groups.     

Effect of grazing pasture with a low selenium content on the concentrations of triiodothyronine and thyroxine in serum, and GSH-Px activity in erythrocytes in cows in Chile

AIM: To determine the effect of grazing pasture that had a low selenium (Se) concentration on serum concentrations of triiodothyronine (T3) and thyroxine (T4), and erythrocyte glutathione peroxidase (GSH-Px) activity in dairy cows. METHODS: Forty pregnant Friesian cows were grazed on pasture that contained 0.03-0.04 ppm Se on a dry matter (DM) basis. Two months before parturition, 20 cows were randomly selected and treated with 1 mg Se/kg bodyweight subcutaneously, as barium selenate (Group Se-S). The other group (Se-D) was not supplemented. Blood samples were taken before supplementation (-60 days) and 30, 60, 90, 180 and 270 days after parturition, for determination of concentrations of T3 and T4 in serum, and GSH-Px activity in erythrocytes. RESULTS: Erythrocyte GSH-Px activity in the Se-D group was <60 U/g haemoglobin (Hb) throughout the experiment. Supplementation increased (p<0.05) activities to >130 U/g Hb throughout lactation. Mean serum concentrations of T4 in Se-D and Se-S cows increased from 23.7 (SEM 0.7) and 23.4 (SEM 0.8) nmol/L, respectively, in the prepartum period to 69.6 (SEM 0.1) and 67.6 (SEM 0.2) nmol/L, respectively, at 180 days of lactation (p<0.01), and no effect of Se supplementation was evident. Serum concentrations of T3 in Se-D cows decreased (p<0.05) from 1.6 (SEM 0.1) nmol/L prepartum to 1.0 (SEM 0.2) nmol/L at the beginning of lactation, and remained lower (p<0.05) than those in the Se-S cows which did not decrease after calving and ranged from 1.9 (SEM 0.1) to 2.4 (SEM 0.2) nmol/L throughout lactation. CONCLUSIONS: Serum T3 concentrations decreased during early lactation in unsupplemented cows grazing pastures low in Se (0.03-0.04 ppm) and both serum T3 and erythrocyte GSHPx activities were consistently lower throughout lactation compared with Se-supplemented cows. Se supplementation had no effect on serum T4 concentrations.     

Factors affecting the calcium, magnesium and phosphorus content of beef cow milk.

This paper reports the calcium, magnesium and phosphorus content of milk from Shorthorn cattle during the five month calf nursing period as well as the effect of prepartum administration of a single intramuscular dose of vitamin D3 or of 25-hydroxyvitamin D3 on the milk mineral constituents. The colostrum of the group which received 25-hydroxyvitamin D3 was found to contain a higher percentage of calcium on the second and third day than the colostrum of control cows or those receiving D3. No differences occurred in colostrum magnesium or phosphorus contents due to prepartum treatment. Calcium, magnesium and phosphorus concentrations were all high in the first day of lactation, but declined until the third day after parturition. Milk calcium, magnesium and phosphorus content of individual cows was not uniform throughout the lactation and the variation was different for different cows.