Immune response of postpartum dairy cows fed flaxseed

Thirty Holstein cows were allotted at calving to 10 groups of three cows blocked for similar calving dates to determine the effects of dietary fatty acids on functional properties of immunocompetent cells in early lactation and at breeding. Cows were assigned at calving to one of three isonitrogenous, isoenergetic, and isolipidic supplements based on either calcium salts of palm oil, Megalac, micronized soybeans, or whole flaxseed. On the day of AI and 20 d later, cows were injected with ovalbumin to measure the antibody response. Blood samples were taken at different times after calving (d 5, 21, 42, and 105) and after AI (d 0, 10, 20, and 40) for quantification of serum progesterone, fatty acids, and prostaglandin E2 concentrations. Isolated peripheral blood mononuclear cells were cultured to evaluate the proliferative response to concanavalin A and in vitro productions of interferon-gamma and prostaglandin E2. In general, feeding flaxseed increased serum omega-3 fatty acids concentration compared with feeding Megalac or soybeans, which decreased the omega-6 to omega-3 fatty acids ratio. There was a significant diet x day interaction for the proliferative response of mononuclear cells after calving and AI, indicating that cell responses from cows fed flaxseed were transiently reduced compared with those fed Megalac and soybeans. Moreover, during the breeding period, serum progesterone concentration was significantly greater in cows fed flaxseed compared with those fed Megalac, whereas serum concentration of prostaglandin E2 was significantly lower in cows fed flaxseed than in those fed Megalac or soybeans. Dietary treatments had no effect on the antibody response to ovalbumin and on in vitro productions of interferon-gamma and prostaglandin E2. However, interferon-gamma and prostaglandin E2 were impaired in the first 3 wk after parturition regardless of dietary treatment. These results suggest that changes in fatty acids, progesterone, and prostaglandins E2 concentrations in serum due to dietary treatment and physiological status influenced systemic immunity as shown by reduced proliferative response. However, other mechanisms must be considered and are discussed to explain dietary effect on lymphocyte proliferative response to mitogenic stimulation and other immune functions.     

Performance, metabolic, and endocrine responses of periparturient Holstein cows fed 3 sources of fat

The objective of this study was to examine the effect of feeding diets containing fat supplements enriched in either saturated fatty acids (n = 10), Ca salts of trans-octadecenoic fatty acids (tFA, n = 10) or Ca salts of safflower oil fatty acids (SFL, high in linoleic acid, n = 9) on performance, metabolic, and endocrine responses of periparturient Holstein cows. Dietary treatments were initiated at approximately 28 d before calculated calving dates and continued through 49 d postpartum. Blood samples for metabolite and hormone analyses were collected weekly beginning 1 wk before estimated calving date through 7 wk postpartum. Incorporation of tFA or SFL into the peripartum diet had no detectable effects on body weight or body condition score. Cows fed the SFL-enriched diet produced less milk fat and established a positive energy balance sooner after calving than those fed the tFA supplement. Analysis for individual fatty acids resulted in increased concentrations of trans 18:1 fatty acid and conjugated linoleic acid isomers in milk fat from cows supplemented with SFL. Across weeks, the average nonesterified fatty acids concentration in plasma was lower in cows fed the SFL-enriched diet than in those consuming the tFA-supplemented diet. Mean concentrations of plasma glucose, insulin-like growth factor-I, and progesterone were greater in cows fed the SFL-enriched diet compared with those fed the saturated fatty acid-supplemented diet. Feeding fat supplements that can suppress milk fat production during the early postpartum period may help minimize negative energy balance, reduce adipose tissue mobilization, and improve circulating concentrations of insulin-like growth factor-I and progesterone. Whether the SFL supplement would have similar effects without a decrease in milk fat production remains to be determined and warrants further investigation.     

Effect of calcium soaps of fatty acids and administration of somatotropin on milk production, preovulatory follicular development, and plasma and follicular fluid lipid composition in high yielding dairy cows

The effect of fat and bovine somatotropin (bST) on preovulatory follicular hormones and lipids was evaluated by feeding cows for 150 d from parturition a control diet, a control diet plus 0.55 kg/d of calcium soaps of fatty acids, or a control diet with 500 mg of bST injected every 14 d. Fourteen days after a synchronized or natural estrus, cows were injected with a PGF2 alpha analogue; 48 h later, follicular fluid from all ovarian follicles > 8 mm was aspirated. Cows fed fat or injected with bST produced more milk and milk solids than did control cows, and cows on the bST treatment lost more body condition after calving than did cows on the other treatments. Both treatments changed the proportion of estradiol-active follicles (> 400 ng of estradiol/ml of follicular fluid) and the correlation between follicular fluid estradiol concentration and the total number large follicles per cow. In follicles aspirated between 60 and 90 DIM the percentage of estradiol-active follicles was 67, 40, and 0 for cows on the control, calcium soaps of fatty acids, and bST treatments, respectively. After 90 DIM, no differences existed between treatments in the percentage of estradiol-active follicles. Estradiol concentration in follicular fluid was correlated with DIM at follicle aspiration (r = 0.51). The proportion of oleic acid in free fatty acids in plasma at 50 DIM was lower in control cows and was lower in follicular fluid of estradiol-active follicles. Both calcium soaps of fatty acids and bST had a considerable effect on follicular development and activity and the composition of fatty acids in follicles.     

Hepatic lipid metabolism in transition dairy cows fed flaxseed

Thirty-three Holstein cows averaging 687 kg of body weight were allotted 6 wk before the expected date of parturition to 11 groups of 3 cows blocked within parity for similar calving dates to determine the effects of feeding different sources of fatty acids on blood parameters related to fatty liver and profile of fatty acids in plasma and liver. Cows were fed lipid supplements from 6 wk before the expected date of parturition until d 28 of lactation. Cows within each block were assigned to 1 of 3 isonitrogenous and isoenergetic dietary supplements: control with no added lipids (CO); unsaturated lipids supplied as whole flaxseed (FL; 3.3 and 11.0% of the dry matter in prepartum and postpartum diets, respectively); and saturated lipids supplied as Energy Booster (EB; 1.7 and 3.5% of the DM in prepartum and postpartum diets, respectively). Diets EB and FL had similar ether extract concentrations. Multiparous cows fed EB had lower dry matter intake and milk production, higher concentrations of nonesterified fatty acids and β-hydroxybutyrate in plasma and triglycerides (TG) and total lipids in liver, and lower concentrations of plasma glucose and liver glycogen than those fed FL and CO. Production of 4% fat-corrected milk was similar among treatments. Multiparous cows fed FL had the highest liver concentrations of glycogen on wk 2 and 4 after calving and lowest concentrations of TG on wk 4 after calving. Liver C16:0 relative percentages in multiparous cows increased after calving whereas those of C18:0 decreased. Relative percentages of liver C16:0 were higher in wk 2 and 4 postpartum for multiparous cows fed EB compared with those fed CO and FL; those of C18:0 were lower in wk 4 postpartum for cows fed EB compared with those fed CO and FL. Liver C18:1 relative percentages of multiparous cows increased after calving and were higher in wk 4 for cows fed EB compared with those fed CO and FL. The inverse was observed for liver C18:2 relative percentages. In general, diets had more significant effects on plasma concentrations of nonesterified fatty acids, β-hydroxybutyrate, and glucose and liver profiles of fatty acids, TG, total lipids, and glycogen of multiparous than primiparous cows. These data suggest that feeding a source of saturated fatty acids increased the risk of fatty liver in the transition cow compared with feeding no lipids or whole flaxseed. Feeding flaxseed compared with no lipids or a source of saturated fatty acids from 6 wk before calving could be a useful strategy to increase liver concentrations of glycogen and decrease liver concentrations of TG after calving, which may prevent the development of fatty liver in the transition dairy cow.     

Effect of feeding propionibacteria on milk production by early lactation dairy cows

This experiment was conducted to determine the effect of a direct-fed microbial agent, Propionibacterium strain P169 (P169), on rumen fermentation, milk production, and health of periparturient and early-lactation dairy cows. Starting 2 wk before anticipated calving, cows were divided into 2 groups and fed a control diet or the control diet plus 6 × 10¹¹ cfu/d of P169. Cows were changed to a lactation diet at calving, and treatments continued until 119 d in milk. Rumen fluid samples were taken about 1 wk before calving, and at 1 and 14 wk after calving. Cows fed P169 had lower concentrations of acetate (mol/100 mol of total volatile fatty acids) at all time points, greater concentrations of propionate on the first and last sampling points, and greater concentrations of butyrate on the first 2 time points. Concentrations of glucose in plasma and milk and plasma concentrations of β-hydroxybutyrate were not affected by treatment. Cows fed P169 had greater concentrations of plasma nonesterified fatty acids on d 7 of lactation. The high nonesterified fatty acids at that time point was probably related to the high production of milk during that period by cows fed the additive. Cows fed P169 during the first 17 wk of lactation produced similar amounts of milk (44.9 vs. 45.3 kg/d, treatment vs. control) with similar composition as cows fed the control diet. Calculated net energy use for milk production, maintenance, and body weight change was similar between treatments, but cows fed the P169 consumed less dry matter (22.5 vs. 23.5 kg/d), which resulted in a 4.4% increase in energetic efficiency.     

Effect of grazing and fat supplementation on production and reproduction of Holstein cows

The objective of this trial was to investigate the effects of feeding a soybean oil refining by-product (SORB), made up mainly of sodium salts of long-chain fatty acids, on reproductive performance and productivity of 36 early lactation Holstein cows managed in a free-stall barn or on annual rye-ryegrass pasture. In this 2 × 2 factorial arrangement of treatments, cows consumed 0 or 0.5 kg/d of SORB as part of a total mixed ration for barn cows or as part of a grain supplement fed to cows on intensively, rotationally stocked pasture. Blood was sampled 3 times weekly and plasma was measured for progesterone to assess ovarian activity. Estrus activity was recorded using the HeatWatch estrus detection system. Although average 14-wk milk production (37.2 kg/d) was not different among treatments, barn cows had more persistent lactations than did grazing cows. Cows housed in the barn lost less body weight and returned to initial body weight sooner and had lower mean concentrations of plasma nonesterified fatty acids (464 vs. 261 mEq/L) than those managed on pasture. The milk fat of cows on pasture contained greater proportions of conjugated linoleic acid and linolenic acid but a corresponding 0.22 percentage unit decrease in milk fat concentration (3.39 vs. 3.16%). Cows managed on pasture had greater peak concentrations of plasma progesterone during the first estrous cycle. Cows managed on pasture and fed SORB had the greatest accumulation of plasma progesterone over the 14 wk of the study (SORB × housing interaction). These cows experienced the most mounts during their first estrus (9.3) and pregnancy rate was also greatest for this treatment (62.5%). Feeding SORB did not affect production of milk, fat, or protein. Loss of body condition was less in cows fed SORB. Ruminal fluid concentration of propionate increased and ruminal pH decreased in cows fed SORB. A lower proportion of fatty acids less than 18 carbons in length was found in the milk fat of cows fed SORB, thus indicating lower de novo synthesis of fatty acids. Higher proportions of C18:2n-6 and conjugated C18:2 were found in the milk fat of cows fed SORB. Based on concentrations of plasma progesterone, cows fed SORB experienced their first ovulation earlier (26.7 vs. 42.4 d postpartum) than did cows not supplemented with SORB. Neither housing system nor SORB supplementation influenced detection of first estrus (50.5 d) or the mean length of each estrus period (447 min).     

Effects of pre- and postfresh transition diets varying in dietary energy density on metabolic status of periparturient dairy cows

Effects of dietary energy density during late gestation and early lactation on metabolic status of periparturient cows were studied. Four weeks before expected calving, animals were fed a low (DL; 1.58 Mcal of NE_L/kg) or high energy density diet (DH; 1.70 Mcal of NE_L/kg). After calving, half of the cows from each prepartum treatment were assigned to a low (L; 1.57 Mcal of NE_L/kg) or high energy density diet (H; 1.63 Mcal of NE_L/kg) until d 20 postpartum. After d 20, all animals were fed H until d 70. Animals fed DH had a more positive energy balance during the prepartum period. Animals fed DH had higher plasma concentrations of glucose and insulin and lower concentrations of plasma nonesterified fatty acid (NEFA) on d −7 relative to calving compared with animals fed DL. No differences in blood concentrations of metabolites, insulin and liver triglycerides (TG) content were observed on d 1. Liver TG content at d 1 and 21 were more related to magnitude of change in energy intake prepartum than to energy intake in the last week of gestation. Cows fed H had higher concentrations of plasma glucose and insulin, but similar plasma NEFA during the postpartum period compared with cows fed L. Plasma concentrations of β-hydroxybutyrate (BHBA) and liver TG content on d 21 were 46 and 30% lower, respectively, for cows fed H compared with cows fed L. Interactions between prepartum and postpartum treatments indicated that negative effects of delaying higher concentrate feeding until d 21 postpartum can be partially offset by increasing concentrate in the diet before calving. Cows fed L had a higher increase in white line hemorrhage scores between prepartum and 10 wk postpartum compared with cows fed H. Energy density of prepartum diets had a minor influence on metabolic status of cows postpartum. A more favorable metabolic profile occurs when increasing the concentrate content of the diet immediately postpartum compared with delaying the increase until d 21 postpartum.     

Parturient hypocalcemia in jersey cows fed alfalfa haylage-based diets with different cation to anion ratios

Jersey cows were fed three alfalfa haylage-based diets with different cation-anion balances beginning 6 wk preceding third or later calving and ending 24 to 36 h postpartum. Sodium and Cl as percentages of dietary DM were .08 and 1.66 in diet 1 (anionic, 5 cows), .44 and .91 in diet 2 (intermediate, 6 cows), and 1.60 and .34 in diet 3 (cationic, 6 cows). Cation-anion balances were 22, 60, and 126 meq/100 g DM; Ca:P ratios averaged 4:1. Cows fed diet 1 in comparison with cows fed diets 2 or 3 over 6 wk had similar concentrations of Ca, P, and Na but higher concentrations of Mg and K in plasma and higher urinary excretions of Ca and Mg. Concentrations of 1,25-dihydroxyvitamin D 3 d before parturition were higher in cows fed diet 1 than in cows fed diets 2 or 3. Within 36 h after calving, mean concentrations of Ca in plasma (mg/dl, range) of cows fed diets 1 to 3, respectively, were 7 (8.7 to 6.2), 6.5 (7.8 to 3.9), and 6.3 (7.8 to 3.8). Number of cases of clinical milk fever by diet were 0 of 5, 2 of 6, and 1 of 6 cows. Alteration of dietary cation-anion balance by addition of Cl may effectively reduce incidence and severity of parturient hypocalcemia.     

Comparison of methods for the synchronization of estrous cycles in dairy cows. 1. Effects on plasma progesterone and manifestation of estrus

Dairy cows (n = 571) were treated with 1) one or two injections of prostaglandin F2 alpha given 11 or 14 d apart, 2) two injections given 14 d apart and a progesterone coil inserted 8 d after the first injection for a 7-d period; or 3) a coil inserted for 7 d and prostaglandin injected 1 d before its removal. Cows given two prostaglandin injections that conceived had higher progesterone concentrations during the luteal phase preceding AI than did cows that did not conceive. Cows with progesterone coils that conceived did not have higher progesterone concentrations than did cows that did not conceive. Older cows had lower progesterone concentrations than younger ones, and they appeared in estrus earlier after treatment. In four daily observations, 75% of cows were seen in estrus within 7 d after treatment. Cows mounting two or more times had a conception rate (62%) similar to that of cows that stood to mount. Fewer cows (56%) treated with prostaglandin that had low concentrations of progesterone appeared in estrus than did cows with high progesterone (84%). Cows treated with prostaglandin differ from cows treated with progesterone coils in respect to manifestation of estrus and to the relationship between plasma progesterone and conception.     

Prevalence of periparturient diseases and effects on fertility of seasonally calving grazing dairy cows supplemented with concentrates

The objectives were to characterize the prevalence of periparturient diseases and their effects on reproductive performance of dairy cows in seasonal grazing farms. A total of 957 multiparous cows in 2 farms (555 in farm A and 402 in farm B) were evaluated and diseases characterized. At calving, dystocia, twin birth, stillbirth, and retained fetal membranes were recorded and grouped as calving problems. On d 7 ± 3 and 14 ± 3 postpartum, cows were evaluated for metritis and on d 28 ± 3 for clinical endometritis based on scoring of the vaginal discharge. From parturition to 30 d after artificial insemination (AI), prevalence of mastitis, lameness, and digestive and respiratory problems were recorded. For subclinical diseases, diagnosis was based on blood samples collected from 771 cows and analyzed for concentrations of Ca, nonesterified fatty acids (NEFA), and β-hydroxybutyrate. Cows were considered as having elevated NEFA concentration if the concentration was ≥0.70 mM, subclinical ketosis if the β-hydroxybutyrate concentration was ≥0.96 mM, and subclinical hypocalcemia if the Ca concentration was ≤2.14 mM. Ovaries were scanned on d 35 ± 3 and 49 ± 3 postpartum for determination of estrous cyclicity. All cows were enrolled in a timed AI program and inseminated on the first day of the breeding season: on average, 86 d postpartum. Overall, 37.5% (359/957) of the cows presented at least 1 clinical disease and 59.0% (455/771) had at least 1 subclinical health problem. Prevalence of individual diseases was 8.5% for calving problems, 5.3% for metritis, 15.0% for clinical endometritis, 13.4% for subclinical endometritis, 15.3% for mastitis, 2.5% for respiratory problems, 4.0% for digestive problems, 3.2% for lameness, 20.0% for elevated NEFA concentration, 35.4% for subclinical ketosis, and 43.3% for subclinical hypocalcemia. Clinical and subclinical diseases had additive negative effects on reproduction, delaying resumption of estrous cyclicity and reducing pregnancy per AI (P/AI). Occurrence of multiple diseases further reduced reproductive efficiency compared with a single disease. Individually, subclinical hypocalcemia, elevated NEFA concentration, metritis, and respiratory and digestive problems reduced estrous cyclicity by d 49 postpartum. Elevated NEFA concentration, calving problem, metritis, clinical and subclinical endometritis, and digestive problems reduced P/AI on d 65 after AI. Moreover, calving problems and clinical endometritis increased the risk of pregnancy loss between gestation d 30 and 65. Serum concentrations of Ca and NEFA were negatively correlated, and both were associated with prevalence of uterine diseases. In conclusion, periparturient diseases were highly prevalent in seasonally calving grazing dairies and affected cows had delayed resumption of estrous cyclicity, reduced P/AI, and increased risk of pregnancy loss.     

Peripartum responses of dairy cows fed energy-dense diets for 3 or 6 weeks prepartum

Pregnant cows (n = 189) in two commercial dairy farms were assigned randomly to be fed energy-dense diets for either 3 or 6 wk before expected calving. Cows fed diets for less than or equal to 26 d were designated the short (S) treatment group, and those fed greater than 26 d were the long (L) treatment group. Cows in L tended to have improved energy status during the first 2 wk postpartum, as indicated by higher insulin concentrations and a tendency for lower nonesterified fatty acid concentrations. Treatment did not affect plasma beta-hydroxybutyrate concentrations. Cows in L tended to gain more body condition during the late dry period. Total body condition loss from parturition through 6 wk postpartum was not different between treatments, but the rate of change varied over this period. Cows in S lost more body condition during the first 3 wk postpartum than cows in L. In farm 1 only, cows in L lost more body condition from 3 to 6 wk postpartum and had a higher incidence of metritis and a longer interval to first service than cows in S. Cows in L had higher milk protein content through 60 d in milk compared with cows in S. Additionally, cows in L in farm 1 produced 4.4 kg/d less milk, tended to have lower milk fat content and yields, and higher somatic cell counts through 150 d in milk than cows in S. Overall, increasing the length of time cows were fed the energy-dense diet prepartum elicited significant changes in farm 1, but had little effect in farm 2. Based on these results, L treatment may improve energy status immediately postpartum, but long-term effects varied between farms, perhaps due to other unmeasured management differences.     

Response of High Producing Dairy Cows in Early Lactation to the Feeding of Heat-Treated Whole Soybeans

Fifty-eight multiparous cows were assigned randomly to one of two rations. Control cows received a concentrate mixture that contained 20% soybean meal as the protein supplement, and the experimental cows were fed a concentrate that contained 25% heat-treated whole soybeans. The experimental period started 10 d after calving and continued for 15 wk.Experimental cows peaked later in milk production (5 vs. 3 wk) but at a higher level (39.8 vs. 39.4 kg/d) than control cows. Although milk production was less during the first 4 wk, experimental cows surpassed the controls in wk 5 and increased the advantage to 2.0 kg/cow/d by wk 15. For the total 15-wk period, average milk production was 37.0 kg/d for the experimental cows compared with 36.2 kg/d for the controls.Total dry matter intake, lactation efficiency, body weight, and reproductive performance were similar for both treatments. Cows fed heated soybeans consumed more metabolizable energy, 61.6 vs. 60.4 Mcal/d for controls. Cows on experimental diet also had higher free fatty acids in plasma (5.6 vs. 4.8 mg/100 ml) and triglycerides (25.0 vs. 20.9 mg/100 ml). The acetate-to-propionate ratio of rumen acids was significantly lower in the experimental group (3.36 vs. 3.61).     

Factors influencing fertility of Holstein dairy cows: a multivariate description

Eighty-two multiparous cows of high and low genetic merit were fed one of two isonitrogenous (19.3% crude protein), isoenergetic (11.3 MJ of metabolizable energy) diets that differed in ratio of rumen-undegradable protein to rumen-degradable protein. Factors that influenced reproductive performance were investigated using logistic regression and survival analysis. Significant associations were identified between reproductive performance and indicators associated with nutrient balance. Cows with higher dry matter intake were more likely to show signs of estrus at first ovulation and to become pregnant by d 150 of lactation. Increased ratio of plasma glucose to 3-hydroxybutyrate was associated with a greater probability of estrous expression at first ovulation. Concentrations of plasma cholesterol were positively associated with expression of estrus at first ovulation, interval from calving to conception, and likelihood of conception and pregnancy. Greater concentrations of nonesterified fatty acids in plasma were associated with a lower probability of conception by d 150 of lactation. Increased yield of fat-corrected milk during early lactation was negatively associated with expression of estrus at first ovulation and probability of pregnancy by d 150 of lactation. Cows of high genetic merit were less likely to show signs of estrus at first ovulation. Cows fed the high rumen-degradable-protein diet that also lost more body weight during early lactation were less likely to conceive at first service and to have a prolonged interval from calving to conception. Continued selection for increased production of milk and a more negative nutrient balance during early lactation may reduce reproductive performance particularly for cows fed high concentrations of rumen-degradable protein.     

Use of 1 alpha-hydroxyvitamin D3 in prevention of bovine parturient paresis. 8. Maternal and neonatal plasma calcium, parathyroid hormone, and vitamin D metabolites concentrations

Thirteen Israeli Friesian cows (3.71 average calvings) in the second or later lactation, fed a daily diet containing 90 g of Ca and 50 g of P, were injected once intramuscularly with 700 micrograms 1 alpha-hydroxy-vitamin D3 in order to investigate its placental transfer and its subsequent metabolism in the neonate. The injection of the vitamin 96 to 24 h before calving slightly increased plasma Ca at parturition, whereas uninjected controls displayed a prominent hypo-calcemia. On the 10th and 20th d after calving, difference in the plasma Ca concentration of the two groups was not significant. At parturition, plasma parathyroid hormone concentration was significantly higher and plasma 1,25-dihydroxyvitamin D lower in the control than in the treated cows. At parturition the plasma concentrations of Ca, parathyroid hormone, hydroxyproline, and 24,25-hydroxyvitamin D were higher in the calves than in their dams. Plasma concentrations of 25-hydroxyvitamin D were markedly higher and 1,25-hydroxyvitamin D was slightly higher in cows than in their offsprings.     

Starch source and content in postpartum dairy cow diets: effects on plasma metabolites and reproductive processes

The objective of this study was to examine the effects of dietary starch source and content in the immediate postpartum period on plasma metabolites and hormones and ovarian follicular development. One of 3 diets was fed in a randomized block design to 40 cows from calving until 70 d in milk. The diets contained 45% alfalfa silage (AS), 45% barley silage (BS), or 41% barley silage and 4% supplemental starch (SS) on a dry matter basis. All diets contained 45% barley-based concentrate and 10% alfalfa hay. Resulting starch levels were 25.2, 23.3, and 26.7% for AS, BS, and SS, respectively. Body condition was scored every other week and dry matter intake and milk yield were recorded daily. Milk samples were obtained weekly and blood samples were taken at calving and then every other week to determine concentrations of glucose, insulin, insulin-like growth factor-1, β-hydroxybutyrate, and nonesterified fatty acids. Transrectal ultrasonography was performed twice per week from 7 d after calving until first ovulation or 62 d in milk in all cows. For a subset of 7 AS-, 8 BS-, and 9 SS-fed cows, a complete estrous cycle was monitored for ovarian dynamics, and blood samples were collected every second day for progesterone and estradiol. Luteinizing hormone pulsatility was also determined (5 cows/treatment) approximately 15 d postcalving. Treatment had no effect on body condition score, dry matter intake, blood metabolites, milk yield, or milk fat and protein contents, but BS-fed cows had significantly higher levels of milk urea nitrogen compared with SS cows. Cows fed SS (31 d) tended to have a shorter interval from calving to first ovulation than cows fed AS (43 d) or BS (38 d). The incidence of double first ovulations was higher in cows fed SS (46%) compared with those fed BS (0%). Treatment had no effect on LH pulse frequency or amplitude, ovarian dynamics, or progesterone and estradiol concentrations during the observed estrous cycle. Energy balance did not differ among cows fed the 3 diets. Overall, dietary starch source and concentration had little effect on productivity or metabolic status of postpartum cows.     

Effects of supplementation with ruminally protected choline on performance of multiparous Holstein cows did not depend upon prepartum caloric intake

Objectives were to evaluate the effect of prepartum energy intake on performance of dairy cows supplemented with or without ruminally protected choline (RPC; 0 or 17.3 g/d of choline chloride; 0 or 60 g/d of ReaShure, Balchem Corp., New Hampton, NY). At 47 ± 6 d before the expected calving date, 93 multiparous Holstein cows were assigned randomly to 1 of 4 dietary treatments in a 2 × 2 factorial arrangement. Cows were fed energy to excess [EXE; 1.63 Mcal of net energy for lactation/kg of dry matter (DM)] or to maintenance (MNE; 1.40 Mcal of net energy for lactation/kg of DM) in ad libitum amounts throughout the nonlactating period. The RPC was top-dressed for 17 ± 4.6 d prepartum through 21 d postpartum (PP). After calving, cows were fed the same methionine-balanced diet, apart from RPC supplementation, through 15 wk PP. Liver was biopsied at ?14, 7, 14, and 21 d relative to parturition. Cows fed EXE or MNE diets, respectively, consumed 40 or 10% more Mcal/d than required at 15 d before parturition. Cows fed the MNE compared with the EXE diet prepartum consumed 1.2 kg/d more DM postpartum but did not produce more milk (41.6 vs. 43.1 kg/d). Thus, PP cows fed the EXE diet prepartum were in greater mean negative energy balance, tended to have greater mean concentrations of circulating insulin, fatty acids, and β-hydroxybutyrate, and had greater triacylglycerol in liver tissue (8.3 vs. 10.7% of DM) compared with cows fed the MNE diet prepartum. Cows fed RPC in transition tended to produce more milk (43.5 vs. 41.3 kg/d) and energy-corrected milk (44.2 vs. 42.0 kg/d) without increasing DM intake (23.8 vs. 23.2 kg/d) during the first 15 wk PP, and tended to produce more milk over the first 40 wk PP (37.1 vs. 35.0 kg/d). Energy balance of cows fed RPC was more negative at wk 2, 3, and 6 PP, but mean circulating concentrations of fatty acids and β-hydroxybutyrate did not differ from those of cows not fed RPC. Despite differences in energy balance at 2 and 3 wk PP, mean concentration of hepatic triacylglycerol did not differ between RPC treatments. Feeding RPC reduced the daily prevalence of subclinical hypocalcemia from 25.5 to 10.5%, as defined by concentrations of total Ca of <8.0 mg/dL in serum in the first 7 d PP. Pregnancy at first artificial insemination tended to be greater for cows fed RPC (41.3 vs. 23.6%), but the proportion of pregnant cows did not differ by 40 wk PP. Heifers born from singleton calvings from cows fed RPC tended to experience greater daily gain between birth and 50 wk of age than heifers from cows not supplemented with RPC. Feeding RPC for approximately 38 d during the transition period tended to increase yield of milk for 40 wk regardless of amount of energy consumed during the pregnant, nonlactating period.     

Supplementation of dairy cow diets with calcium salts of long-chain fatty acids and nicotinic acid in early lactation.

Forty multiparous Holstein cows were assigned to one of four treatments 15 d postpartum according to milk yield during wk 2 postpartum to examine the effects of supplementing niacin, Ca salts of long-chain fatty acids, and their interaction. Treatments were control, niacin (12 g/d), Ca salts of long-chain fatty acids (3% of dietary DM), or a combination of niacin and Ca salts. On d 99 postpartum, all cows were fed the control treatment for 2 wk to evaluate residual effects. Milk and FCM yields, blood plasma NEFA and beta-hydroxybutyrate concentrations, and apparent total tract hemicellulose digestibility were increased; milk protein percentage, milk SNF percentage, and blood plasma glucose concentrations were reduced by treatments containing the Ca soaps. Niacin supplementation increased milk protein content and yield but reduced blood plasma beta-hydroxybutyrate concentration. During the residual period, in which all cows received the control treatment, milk yield and plasma NEFA concentration remained elevated, milk protein and SNF contents remained depressed, and milk fat content was reduced for cows previously supplemented with Ca salts of long-chain fatty acids. Methionine and phenylalanine uptakes by the mammary gland were enhanced by niacin supplementation. Results indicated that dairy cattle in early lactation yielded more milk when their diets were supplemented with Ca salts of long-chain fatty acids and that niacin supplementation increased milk protein content and yield.     

Comparison of methods for the synchronization of estrous cycles in dairy cows. 2. Effects of progesterone and parity on conception

Three experiments with 571 dairy cows indicated that significantly more primiparous cows given two prostaglandin F2 alpha injections 14 d apart conceived within 30 d of first AI than did cows given two injections 11 d apart (84 vs. 62%). Fewer multiparous cows given two injections 14 d apart and inseminated after estrus conceived than did cows given two injections and a progesterone intravaginal coil inserted 8 d after the first injection (42 vs. 66%). Fewer cows given one injection of prostaglandin and inseminated at estrus conceived than did cows given two injections 14 d apart and a progesterone coil (39 vs. 66%). Conception rates of cows given two prostaglandin injections were positively related to plasma progesterone concentrations 2 and 4 d before the second injection (r = .81 and .86). Cows with progesterone concentrations below 5 ng/ml, 2 d before the second prostaglandin injection, and synchronized by two prostaglandin injections or by two injections and a progesterone coil had conception rates of 36 and 63%, respectively. Cows with progesterone concentrations above 5 ng/ml had a conception rate of 75 and 46% in the two treatments, respectively. Conception after estrus synchronization depends on the method and on the plasma concentrations of progesterone. Progesterone coils may be used before AI to enhance fertility in cows with low progesterone concentrations.     

Effects of altering dietary cation-anion difference on calcium and energy metabolism in peripartum cows

Our objective was to determine the effects of varying dietary cation-anion differences (DCAD: meq[(Na + K) - (Cl + S)]/100 g of dry matter) in prepartum diets on Ca, energy, and endocrine status prepartum and postpartum. Holstein cows (n = 21) and heifers (n = 34) were fed diets with varying amounts of CaCl2, CaSO4, and MgSO4 to achieve a DCAD of +15 (control), 0, or -15 meq/100 g of dry matter for the last 24 d before expected calving. Dietary Ca concentration was increased (by CaCO3 supplementation) with decreasing DCAD. Plasma ionized Ca concentrations prepartum and at calving in both cows and heifers increased with reduced DCAD in the diet. At calving, plasma ionized Ca concentration was 3.67, 3.85, and 4.35 for cows and 4.44, 4.57, and 4.62 mg/dl for heifers fed diets containing +15, 0, and -15 DCAD, respectively. All heifers had normal concentrations of plasma ionized Ca (>4 mg/dl) at calving. Also at calving, plasma concentrations ofparathyroid hormone and calcitriol were less in cows and heifers fed diets containing reduced DCAD, but the plasma concentration of hydroxyproline was not affected by diet. Prepartum dry matter intake, energy balance, and body weight gains were lower and concentration of liver triglyceride was higher for heifers but not cows fed the -15 DCAD diet. Also, nonesterified fatty acids the last week prepartum were positively correlated with liver triglyceride for heifers but not cows. Feeding of anionic salts plus CaCO3 to reduce DCAD to -15 and increase Ca in prepartum diets prevents hypocalcemia at calving in cows, but decreases prepartum dry matter intake and increases the concentration of liver triglyceride in heifers. That heifers maintained calcium homeostasis at calving regardless of diet but ate less when fed the -15 DCAD diet suggests that they should not be fed anionic salts before calving.     

Impact of prepartum dietary phosphorus intake on calcium homeostasis at parturition

A study was conducted to determine the impact of dietary P intake on vitamin D metabolism and incidence of parturient paresis in aged dairy cows. Thirty dairy cows (10/group) were fed one of three experimental diets for approximately 28 d precalving. Phosphorus intake was .7, 1, or 3 times daily maintenance requirement and Ca intake was three times daily maintenance requirement for all cows. There was a 20% incidence of parturient paresis in each group. Prepartum dietary P intake had no effect on precalving or calving plasma Ca concentrations. Cows fed the low P (.7 times) diet had higher plasma Ca at 3 and 5 d postcalving than did cows fed P at 1 or 3 times maintenance. Plasma phosphorus concentrations reflected dietary P intake. Dietary P intake had no effect on plasma Mg, free hydroxyproline, 1,25-dihydroxyvitamin D, or 24,25-dihydroxyvitamin D concentrations. The range in dietary P from .7 to 3 times maintenance requirement had no effect on the incidence of parturient paresis. However, it did appear to influence Ca homeostasis during the postpartum period as cows fed the low P diet had higher plasma calcium concentrations postcalving. This may be a result of the low P diet enhancing intestinal C absorption by a vitamin D-mediated transport mechanism.