Short communication: Effects of dietary 5,6-dimethylbenzimidazole supplementation on vitamin B12 supply,lactation performance,and energy balance in dairy cows during the transition period and early lactation

The current study was conducted to investigate the effects of 5,6-dimethylbenzimidazole (DMB) supplementation to the feed during the transition period and early lactation on the vitamin B₁₂ supply, lactation performance, and energy balance in postpartum cows. Twenty-four prepartum Holstein dairy cows were divided into 12 blocks based on their parity and milk yield at the last lactation and were then randomly allocated to 1 of 2 treatments: a basal diet without DMB (control) or a treatment diet that contained 1.5 g of DMB/d per cow. The study started at wk 3 before the expected calving day and ended at wk 8 postpartum. The feed intake and the lactation performance were measured weekly after calving. Blood parameters were measured on d ?10, 0, 8, 15, 29, 43, and 57 relative to the calving day. Body weight was measured on the calving day and on d 57 after calving. The yields of milk, protein, and lactose in cows fed DMB were higher than in the control throughout the whole postpartum stage. On wk 8 postpartum, the vitamin B₁₂ content in the milk and sera was greater in cows fed DMB than in the control. The overall body weight loss from wk 1 to 8 postpartum was less in cows fed DMB than in the control. The plasma content of nonesterified fatty acids and β-hydroxybutyric acid was significantly lower in cows fed DMB than in the control throughout the whole experimental stage. In conclusion, dietary DMB fed during the transition period and early lactation improved the vitamin B₁₂ supply, milk production, and energy balance of postpartum dairy cows.     

Effects of intramuscular injections of folic acid,vitamin B12, or both,on lactational performance and energy status of multiparous dairy cows

The purpose of this experiment was to gain understanding on changes in energy partitioning when folic acid and vitamin B₁₂ supplements, alone or combined, were given by weekly intramuscular injections from 3 wk before the expected calving date until 7 wk postpartum. Twenty-four multiparous cows were assigned to 6 blocks of 4 cows each according to previous 305-d lactation yield to either 0 or 320 mg of folic acid and 0 or 10 mg of vitamin B₁₂ in a 2 × 2 factorial arrangement. Plasma concentration of folates was increased by folic acid supplement, and this increase was greater with the combined supplement. Vitamin B₁₂ supplement increased plasma concentration of vitamin B₁₂. Even though postpartum energy balance was similar among treatments, postpartum body condition score was higher for cows receiving folic acid supplement compared with cows that did not. Milk yield of cows receiving folic acid supplement reached a plateau earlier than for cows that did not. Fat and protein, as well as total solid concentrations and yields, were unaffected by treatments. Postpartum plasma concentrations of glucose and insulin were higher and postpartum plasma concentration of nonesterified fatty acids was lower for cows that received weekly folic acid supplement compared with cows that did not. Plasma concentration of methylmalonic acid was low and unaffected by treatments, suggesting that vitamin B₁₂ supply was not limiting, even for unsupplemented cows. Postpartum plasma concentrations of Cys, His, Phe, and Tyr were increased, whereas plasma concentration of Gly was decreased, by folic acid supplement. In the present study, supplementary folic acid altered energy partitioning in early lactation as suggested by similar milk total solid yield and postpartum energy balance, lower plasma nonesterified fatty acid concentration and body condition score losses, and higher plasma glucose and insulin concentrations for cows receiving folic acid supplement compared with cows that did not.     

Effects of prepartum dietary protein level and feed intake on postpartum lactation performance and feeding behavior of multiparous Holstein dairy cows

An experiment was conducted to determine the effects of low and high metabolizable protein (MP) diets when fed for ad libitum and controlled intake during the prepartum period on postpartum lactation performance and feeding behavior of dairy cows. Thirty-six multiparous Holstein cows were blocked by parity, expected calving date, and previous lactation milk yield at −21 d relative to expected calving and were randomly assigned to 1 of 4 close-up period dietary treatments providing low MP (LMP) or high MP (HMP) diets with controlled intake (CNI) or ad libitum intake (ALI). The concentrations of MP were 65 and 90 g/kg dry matter for LMP and HMP diets, respectively, whereas intake was controlled to supply 100 and 160% of the NRC (2001) energy requirements for CNI and ALI groups, respectively. The concentration of net energy for lactation (NE_L) in the treatment diets was 1.50 Mcal/kg. All cows were fed a similar lactation diet after calving (1.50 Mcal/kg of NE_L and 83.3 g/kg of MP). The HMP diet increased dry matter intake during the first 3 wk and tended to increase dry matter intake over the 9 wk of lactation. Meal size and eating rate increased in the ALI cows during the prepartum period. Meal frequency increased with the HMP diet during the postpartum period. Milk yield increased by 15.2% with the HMP diet over the 9 wk of lactation. The HMP diet increased energy-corrected milk (ECM) yield in CNI versus ALI cows, whereas the LMP diet increased ECM yield in ALI versus CNI cows over the 9 wk of lactation. The increase in ECM yield of LMP-ALI versus LMP-CNI cows was supported by greater body condition loss and serum β-hydroxybutyrate over the 9 wk of lactation. Taken together, these data indicate that prepartum controlled intake of a high protein diet can provide the benefits of both strategies.     

Addition of straw to the early-lactation diet: Effects on feed intake,milk yield,and subclinical ketosis in Holstein cows

This study evaluated feed intake, milk yield, and subclinical ketosis in dairy cows in early lactation fed 2 different diets postpartum. Cows are typically offered a high-energy ration immediately after calving. We compared a conventional high-energy total mixed ration (TMR) with a transition ration that contained chopped straw. We predicted that adding chopped straw would increase dry matter intake, milk production, and indicators of energy metabolism during the first 3 wk of lactation compared to cows fed a conventional high-energy TMR. We also predicted that carryover effects would be likely for at least 2 wk after treatment ended. A total of 68 mixed-age Holstein cows were enrolled in the study 3 wk before their expected calving. All cows were managed on a single high-forage diet during the dry period. At calving, cows were allocated to 1 of the 2 diets: half to the conventional high-energy TMR (CTMR; n = 34; net energy for lactation = 1.61 Mcal/kg; neutral detergent fiber = 31.7%), and the other half to a high-forage TMR containing chopped wheat straw, equivalent to 4.27% dry matter (STMR; n = 34; net energy for lactation = 1.59 Mcal/kg; neutral detergent fiber = 33.7%) for 3 wk after calving. Cows on STMR were then shifted to CTMR for the next 2 wk to study short-term residual effects on the performance of cows. Treatments were balanced for parity, body condition score, and body weight. Feed intake was measured daily from 2 wk before to 5 wk after calving using automatic feed bins. Blood was sampled twice weekly from 2 wk before to 5 wk after calving, and β-hydroxybutyrate and glucose were measured in serum samples. Subclinical ketosis was identified using a threshold of β-hydroxybutyrate ≥1.0 mmol/L in wk 1 after calving and ≥1.2 mmol/L in wk 2 to 5 after calving. Cows were milked twice daily, and weekly samples (composite samples of morning and afternoon milkings) were analyzed to determine total solids, fat, protein, lactose, and somatic cell count. Data were analyzed in 2 separate periods: the treatment phase (wk +1, +2, and +3) and the post-treatment phase (wk +4 and +5). The addition of straw to the TMR negatively affected the dry matter intake of STMR cows during wk 2 and 3 of lactation. Daily milk yield during the first 5 wk of lactation was lower in STMR cows than in CTMR cows. Concentrations of β-hydroxybutyrate were higher in CTMR cows than in STMR cows during wk 1, but this effect was reversed during wk 2 and 3 of lactation. By 21 d in milk, STMR cows had a greater risk of developing subclinical ketosis than CTMR cows. Adding chopped wheat straw to the TMR during the first 21 d after calving lowered dry matter intake and provided no metabolic or production benefits to lactating dairy cattle.     

Effects of feeding betaine-containing liquid supplement to transition dairy cows

Betaine is a natural compound found in sugar beets that serves as a methyl donor and organic osmolyte when fed to animals. The objective was to evaluate the effect of feeding betaine-containing molasses on performance of transition dairy cows during late summer in 2 trials. In early September, cows were randomly assigned to betaine (BET) or control (CON) groups either shortly after dry off (trial 1; n = 10 per treatment) or 24 d before calving (trial 2; n = 8 per treatment) based on parity and previous mature equivalent milk yield. Cows were fed common diets supplemented either with a liquid supplement made of molasses from sugar cane and condensed beet solubles containing betaine [BET, 89.1 g/kg of dry matter (DM)] or a sugar cane molasses-based liquid supplement without betaine (CON) until 8 wk postpartum. The liquid supplements had similar nutrient contents and were fed at a rate of 1.1 and 1.4 kg DM/d for pre- and postpartum cows, respectively. Starting at their entry in the studies, cows were housed in the same freestall barn without a cooling system. After calving, all cows were housed in the same barn cooled by misters and fans and milked thrice daily. Intake was recorded daily and body weight and body condition score were assessed every 2 wk. Milk yield was recorded at each milking and composition was analyzed weekly. Blood samples were collected weekly from a subset of cows to assess concentrations of metabolites and AA. No treatment effects were apparent for DM intake and body weight in the prepartum and postpartum periods. For cows enrolled at dry off, BET supported higher milk yield (45.1 vs. 41.9 kg/d) and fat content (4.78 vs. 4.34%) and elevated plasma concentrations of nonesterified fatty acids and β-hydroxybutyrate in early lactation compared to CON. However, no differences were observed for milk yield, most milk component contents and yields, and blood metabolites between treatments for cows enrolled during the close-up period. Compared to cows in the CON group, BET cows enrolled during the far-off period tended to have lower plasma concentrations of Met, Thr, and Trp during the pre- and postpartum periods. They also had lower plasma concentrations of Lys and Phe before calving but higher plasma Gly concentration after parturition. In conclusion, feeding a betaine-containing liquid supplement from far-off through early lactation improves lactation performance but increases adipose tissue mobilization and production of ketone bodies in early lactation.     

Effects of supplementary folic acid and vitamin B12 on hepatic metabolism of dairy cows according to methionine supply

The present experiment was undertaken to study the interactions between dietary supplements of rumen-protected methionine (RPM) and intramuscular injections of folic acid and vitamin B₁₂, given from 3 wk before calving to 16 wk of lactation, on hepatic metabolism of lactating dairy cows. Sixty multiparous Holstein cows were assigned to 10 blocks of 6 cows each according to their previous milk production. Within each block, 3 cows were fed a diet calculated to supply Met as 1.83% of metabolizable protein, whereas the 3 other cows were fed the same diet supplemented with 18 g of RPM calculated to provide Met as 2.23% of metabolizable protein. Within each level of Met, the cows received no vitamin supplement or weekly intramuscular injections of 160 mg of folic acid alone or combined with 10 mg of vitamin B₁₂. Liver biopsies were taken at 2, 4, 8, and 16 wk of lactation. Liver concentrations of folates and vitamin B₁₂ were increased by their respective supplements but this response to vitamin supplements was altered by methionine supply. Concentrations of total lipids and triglycerides increased in livers of cows fed RPM, whereas concentrations of cholesterol ester, cholesterol, diglycerides, phosphatidylethanolamine, and phosphatidylcholine were not affected. Folic acid, alone or combined with vitamin B₁₂, tended to increase the ratio of phosphatidylcholine to phosphatidylethanolamine. Gene expression of 5,10-methylene-tetrahydrofolate reductase, microsomal transfer protein, and phosphatidylethanolamine methyltransferase were higher in liver of cows fed RPM supplements. The relative mRNA abundance of 5,10-methylene-tetrahydrofolate reductase and methylmalonyl-CoA mutase were increased by the combined injections of folic acid and vitamin B₁₂, whereas those of methionine synthase and methionine synthase reductase were not affected by treatments. These results suggest that increasing supply of methyl groups, as preformed labile methyl groups or through methylneogenesis, affected the methylation cycle but had a limited effect on dairy cow performance. The observed effects of the combined supplement of folic acid and vitamin B₁₂ on lactational performance of dairy cows probably result from an improvement of energy metabolism during early lactation.     

Influence of methionine supply on the response of lactational performance of dairy cows to supplementary folic acid and vitamin B12

The present experiment was undertaken to determine if the effects of supplementary folic acid on lactational performance were caused by improved methylneogenesis and if the supply in vitamin B₁₂ could affect this metabolic pathway. In this eventuality, supplementary Met, a major source of preformed methyl groups, should reduce the requirements for these vitamins. Sixty multiparous Holstein cows were assigned to 10 blocks of 6 cows each according to their previous milk production. Within each block, 3 cows were fed a diet estimated to supply Met as 1.83% metabolizable protein and 3 cows were fed the same diet supplemented with 18 g of rumen-protected methionine (RPM) to supply Met as 2.23% of metabolizable protein. Within each level of Met, cows received no vitamin supplement or weekly intramuscular injections of 160 mg of folic acid alone or combined with 10 mg of vitamin B₁₂ from 3 wk before to 16 wk after calving. There was no treatment effect on dry matter intake during pre- and postcalving periods: 13.4 ± 0.4 and 21.8 ± 0.4 kg/d, respectively. Milk production was not affected by RPM supplementation. Folic acid and vitamin B₁₂ given together tended to increase milk production during the 16 wk of lactation. This effect was more pronounced during the first 4 wk of lactation: 37.5, 37.7, and 40.3 ± 0.9 kg/d for cows receiving no vitamin supplement, folic acid alone, or folic acid combined with vitamin B₁₂, respectively. Milk fat yield was not affected by treatments. Lactose, crude protein, and total solid yields were greater, in early lactation, in cows injected with folic acid and vitamin B₁₂ together but this effect diminished as lactation progressed. Intramuscular injections of folic acid alone or combined with vitamin B₁₂ tended to decrease plasma concentrations of homocysteine from 5.51 μM with no vitamin supplement to 4.54 and 4.77 ± 0.37 μM, respectively. Results of the present experiment suggest that the effects of the combined supplement of folic acid and vitamin B₁₂ on lactational performance of dairy cows were not due to an improvement in methyl groups supply, because RPM supplement, a source of preformed methyl groups, did not alter the cow responsiveness to vitamin supplements.     

Effects of folic acid and vitamin B12 supplementation on culling rate,diseases, and reproduction in commercial dairy herds

This study was undertaken to determine the effect of a combined folic acid and vitamin B₁₂ supplement given in early lactation on culling rate, metabolic disorders and other diseases, and reproduction in commercial dairy herds. A total of 805 cows (271 primiparous and 534 multiparous cows) in 15 commercial dairy herds were involved. Every 2 mo from February to December 2010 and within each herd, cows were assigned according to parity, previous 305-d milk production, and calving interval to 5 mL of either (1) saline 0.9% NaCl (control group) or (2) 320 mg of folic acid + 10 mg of vitamin B₁₂ (vitamin group). Treatments were administered weekly by intramuscular injections starting 3 wk before the expected calving date until 8 wk after parturition. A total of 221 cows were culled before the next dry period. Culling rate was not affected by treatment and was 27.5%; culling rate was greater for multiparous (32.2%) than for primiparous cows (18.8%). Within the first 60 d in milk (DIM), 47 cows were culled, representing 21.3% of total culling, and no treatment effect was noted. Ketosis incidence based on a threshold ≥100 µmol/L of β-hydroxybutyrate in milk was 38.3 ± 2.9% for the vitamin group and 41.8 ± 3.0% for the control group and was not affected by treatment. The combined supplement of folic acid and vitamin B₁₂ did not decrease incidence of retained placenta, displaced abomasum, milk fever, metritis, or mastitis. However, the incidence of dystocia decreased by 50% in multiparous cows receiving the vitamin supplement, although no effect was observed in primiparous cows. The first breeding postpartum for multiparous cows occurred 3.8 d earlier with the vitamin supplement compared with controls, whereas no treatment effect was seen for primiparous cows. Days open, first- and second-breeding conception rates, number of breedings per conception, and percentage of cows pregnant at 150 DIM were not affected by treatment. The reduced percentage of dystocia combined with the earlier DIM at first breeding for multiparous cows receiving the combined supplementation in folic acid and vitamin B₁₂ indicates that the vitamin supplement had a positive effect in older cows.     

Effect of prepartum dietary energy on condition score, postpartum energy, nitrogen partitions, and lactation production responses

Objectives were to examine the effects of feeding to alter body condition at calving on subsequent full lactation production performance and feed intake, on BW and periparturient blood traits, and on complete energy and N balances and ration digestibility during wk 6, 10, and 14 postpartum. Thirty pluriparous Holstein cows were assigned randomly to two energy intakes from wk 33 of previous lactation through the dry period to create either normal (7.2) or thin (5.8) mean body condition scores at calving (9 = fat, 1 = thin). The thin group was fed 0 kg hominy feed daily; the normal group was fed 2.7 kg daily to supplement forage DM available ad libitum during this period. When compared with the normal group, cows in the thin condition group exhibited less negative body fat balance (-206 vs. -507 g/d); similar milk yield, DM intake, N partitions, and nutrient digestibilities; and lower fat test (3.2 vs. 4.1%) during the balance measurements. Whole blood and serum traits were within normal physiological ranges. Full lactation measurements were similar between treatments except that milk fat percentage was lower and DM intake (as percentage of BW), was higher in the thin condition group. Although mean BW at calving was more (651 vs. 599 kg) for normal condition cows, condition scores and BW were not significantly different at 14 wk postpartum; BW curves indicated similar rates of recovery of weight thereafter. Cows considered underconditioned at parturition mobilized less body fat after calving, resulting in reduced milk fat concentration without significant effects on milk yield, protein, SNF, DM intake, or nutrient utilization.     

Short communication: A positive relationship between the first ovulation postpartum and the increasing ratio of milk yield in the first part of lactation in dairy cows

The aim of the present study was to examine the relationship between characteristics of the lactation curve, on the basis of daily milk yield, and ovulation within 3 wk postpartum as an indicator of early return to luteal activity in dairy cows. Lactation records from 46 lactating Holstein cows between calving and 305 d postpartum were studied. Milk samples were collected twice weekly between d 7 and 100 for later determination of progesterone concentrations. Occurrence of an early first ovulation was determined by an increase in milk progesterone by 3 wk after calving. Milk yield was recorded daily until 305 d postpartum, and average yield was calculated weekly. The lactation curve was characterized by 8 indices on the basis of the weekly average of milk yield as follows: a) first-week milk yield; b) peak milk yield; c) actual 305-d milk yield; d) peak week; e) difference in milk yield between the first week and peak week; f) difference in milk yield between the peak week and last week (43rd week postpartum); g) ratio of increase in milk yield between wk 1 and the week of peak yield; and h) ratio of decline in milk yield between the week of peak yield and the last week. Indices g and h were calculated as linear. The number of cows having ovulated by 3 wk postpartum was 22 (47.8%). The resumption of ovarian cycles with normal luteal phases occurred earlier in ovular cows than in anovular cows (32.0 d vs. 57.1 d). Although total milk yield did not differ between ovular and anovular cows, the ratio of increase in milk yield from the first week to the peak week (index g) in ovular cows was smaller compared with that of anovular cows (1.71 vs. 2.54). In addition, the ratio of increase in milk yield from the first week to the third week postpartum was greater in anovular cows by 3 wk postpartum (ovular = 1.43 ± 0.23 vs. anovular = 2.32 ± 0.29). In conclusion, the present study demonstrates that a greater increasing ratio of milk yield during early lactation may delay resumption of ovarian cycles after parturition. Therefore, this study is the first to demonstrate statistically that a smaller increasing ratio of milk yield (index g) during early lactation may have a beneficial effect on the first ovulation by 3 wk postpartum.     

Effects of supplements of folic acid, vitamin B12, and rumen-protected methionine on whole body metabolism of methionine and glucose in lactating dairy cows

The present experiment was undertaken to determine the effects of dietary supplements of rumen-protected methionine and intramuscular injections of folic acid and vitamin B₁₂, given 3 wk before to 16 wk after calving, on glucose and methionine metabolism of lactating dairy cows. Twenty-four multiparous Holstein cows were assigned to 6 blocks of 4 cows each according to their previous milk production. Within each block, 2 cows were fed a diet estimated to supply methionine as 1.83% metabolizable protein, equivalent to 76% of methionine requirement, whereas the 2 other cows were fed the same diet supplemented daily with 18 g of rumen-protected methionine. Within each diet, the cows were administrated either no vitamin supplement or weekly intramuscular injections of 160 mg of folic acid plus 10 mg of vitamin B_12. To investigate metabolic changes at 12 wk of lactation, glucose and methionine kinetics were measured by isotope dilution using infusions of 3[U-¹³C]glucose, [¹³C]NaHCO₃ and 3[1-¹³C,²H₃] methionine. Milk and plasma concentrations of folic acid and vitamin B₁₂ increased with vitamin injections. Supplementary B-vitamins increased milk production from 34.7 to 38.9 ± 1.0 kg/d and increased milk lactose, protein, and total solids yields. Whole-body glucose flux tended to increase with vitamin supplementation with a similar quantitative magnitude as the milk lactose yield increase. Vitamin supplementation increased methionine utilization for protein synthesis through increased protein turnover when methionine was deficient and through decreased methionine oxidation when rumen-protected methionine was fed. Vitamin supplementation decreased plasma concentrations of homocysteine independently of rumen-protected methionine feeding, although no effect of vitamin supplementation was measured on methionine remethylation, but this could be due to the limitation of the technique used. Therefore, the effects of these B-vitamins on lactation performance were not mainly explained by methionine economy because of a more efficient methylneogenesis but were rather related to increased glucose availability and changes in methionine metabolism.     

Short communication: Associations of udder edema with health,milk yield,and reproduction in dairy cows in early lactation

Udder edema (UE) is a common condition of cows around calving, but its effects are not well characterized. The objectives of this study were to determine the associations of UE with the incidence of health disorders and with milk yield and reproduction in dairy cows in early lactation. On 3 commercial farms, UE was scored weekly on 1,346 cows, on a scale of 0 to 3, from 1 wk before calving to 3 wk after calving. Among cows with complete UE scores, 30% never had edema, 12% had edema only prepartum, 11% had it only postpartum, and 48% had edema prepartum and in at least 1 wk postpartum. Udder edema was associated with a greater incidence of clinical mastitis before 30 d in milk (5 vs. 2%). Subclinical ketosis (blood β-hydroxybutyrate ≥1.2 mmol/L) was more prevalent at wk 2 (11 vs. 6%) postpartum among cows with UE. No association was observed of UE with other diseases or culling in early lactation. In a subset of 912 cows with complete UE and 3 test-days of milk yield data, differences were observed in yield at test d 1 among UE categories. Cows with UE only prepartum produced less milk (39.9 kg/d) than cows with UE postpartum only (42.4 kg/d) and cows with UE both prepartum and postpartum (41.6 kg/d), none of which differed from cows without UE (40.9 kg/d). Udder edema was not associated with the prevalence of anovulation, or the time to or probability of pregnancy at first insemination, yet to 300 d in milk, cows that had UE postpartum had a shorter time from calving to pregnancy than cows without UE. The associations of UE with health and productivity are mixed, and the mechanisms underlying UE and its effects merit further investigation.     

Assessing feed efficiency in early and mid lactation and its associations with performance and health in Holstein cows

Objectives were to evaluate the associations between residual dry matter (DM) intake (RFI) and residual N intake (RNI) in early lactation, from 1 to 5 wk postpartum, and in mid lactation, from 9 to 15 wk postpartum, and assess production performance and risk of diseases in cows according to RFI in mid lactation. Data from 4 experiments including 399 Holsteins cows were used in this study. Intakes of DM and N, yields of milk components, body weight, and body condition were evaluated daily or weekly for the first 105 d postpartum. Milk yield by 305 d postpartum was also measured. Incidence of disease was evaluated for the first 90 d postpartum and survival up to 300 d postpartum. Residual DM and N intake were calculated in early and mid lactation as the observed minus the predicted values, which were based on linear models that accounted for major energy or N sinks, including daily milk energy or N output, metabolic body weight, and daily body energy or N changes, and adjusting for parity, season of calving, and treatment within experiment. Cows were ranked by RFI and RNI in mid lactation and categorized into quartiles (Q1 = smallest RFI, to Q4 = largest RFI). Increasing efficiency in mid lactation resulted in linear decreases in RFI (depicted from Q1 to Q4; ?0.93, ?0.05, ?0.04, and 0.98 kg/d), DMI (16.0, 16.9, 17.3, and 18.4 kg/d), net energy for lactation (NE_L) intake (26.8, 28.4, 29.0, and 30.8 Mcal/d), and NE_L balance (?9.0, ?8.1, ?8.2, and ?5.5 Mcal/d) during early lactation, but no differences were observed in body NE_L or N changes or yield of energy-corrected milk in the first 5 wk of lactation. Residual DM intake in mid lactation was associated with RFI (Pearson r = 0.43, and Spearman ρ = 0.32) and RNI (r = 0.44, ρ = 0.36) in early lactation, and with RNI in mid lactation (r = 0.91, ρ = 0.84). Similarly, RNI in mid lactation was associated with RNI in early lactation (r = 0.42, ρ = 0.35). During the first 15 wk postpartum, more efficient cows in mid lactation consumed 3.5 kg/d less DM (Q1 = 19.3 vs. Q4 = 22.8 kg/d) and were more N efficient (Q1 = 31.6 vs. Q4 = 25.8%), at the same time that yields of milk (Q1 = 39.0 vs. Q4 = 39.4 kg/d), energy-corrected milk (Q1 = 38.6 vs. Q4 = 39.3 kg/d), and milk components did not differ compared with the quartile of least efficient cows. Furthermore, RFI in mid lactation was not associated with 305-d milk yield, incidence of diseases in the first 90 d postpartum, or survival by 300 d postpartum. Collectively, rankings of RFI and RNI are associated and repeatable across lactation stages. The most feed-efficient cows were also more N efficient in early and mid lactation. Phenotypic selection of RFI based on measurements in mid lactation is associated with improved efficiency without affecting production or health in dairy cows.     

Response to a glucose tolerance test in early-lactation Holstein cows receiving a supplementation of biotin,folic acid,and vitamin B12

The aim of the study was to evaluate glucose and insulin metabolism of cows receiving a supplementation of biotin (B₈), folic acid (B₉), and vitamin B₁₂ (B₁₂) during the transition period. According to a 2 × 2 factorial arrangement, 32 cows were randomly assigned to 9 incomplete blocks according to their previous 305-d milk yield. Within each block, cows were randomly assigned to 1 of the following levels of biotin from ?27 to 28 d relative to the parturition: (1) no biotin supplement (B₈?) or (2) 20 mg/d of dietary biotin (B₈+). Within each level of biotin, the cows received either (1) 2-mL weekly intramuscular injections of saline 0.9% NaCl (B₉B₁₂?) or (2) 2.6 g/d of dietary folic acid and 2-mL weekly intramuscular injections of 10 mg of vitamin B₁₂ (B₉B₁₂+). An intravenous glucose tolerance test was performed at 25 d in milk. Baseline plasma glucagon, glucose, and nonesterified fatty acid concentrations did not differ among treatments. For B₉B₁₂+ cows, baseline plasma insulin concentration and maximal glucose concentration after glucose administration were greater when also combined with biotin compared with no biotin combination, whereas there was no effect in B₉B₁₂? cows. There was no treatment effect on time to reach half-maximal glucose and insulin concentrations, glucose positive incremental area under the curve, and glucose and insulin clearance rates. Regarding insulin results, maximal plasma concentration and positive incremental area under the curve were respectively 51 and 74% greater for cows receiving the B₈ supplement than for cows who did not. Moreover, plasma nonesterified fatty acid concentration nadir tended to be reached later for B₈ cows. Insulin peak was reached earlier for cows in the group B₉B₁₂+ than cows in B₉B₁₂?, regardless of B₈ supplementation. Under the current conditions, our results suggested that cows receiving a B₈ supplement had a reduced insulin sensitivity in early lactation. Insulin response was faster for B₉B₁₂+ cows, but this was not translated into further improvements following the glucose administration challenge.     

Effect of rumen-protected choline on performance, blood metabolites, and hepatic triacylglycerols of periparturient dairy cattle

The effects of a dietary supplement of rumen-protected choline on feed intake, milk yield, milk composition, blood metabolites, and hepatic triacylglycerol were evaluated in periparturient dairy cows. Thirty-eight multiparous cows were blocked into 19 pairs and then randomly allocated to either one of 2 treatments. The treatments were supplementation either with or without (control) rumen-protected choline. Treatments were applied from 3 wk before until 6 wk after calving. Both groups received the same basal diet, being a mixed feed of grass silage, corn silage, straw, and soybean meal, and a concentrate mixture delivered through transponder-controlled feed dispensers. For all cows, the concentrate mixture was gradually increased from 0 kg/day (wk −3) to 0.9 kg of dry matter (DM)/d (day of calving) and up to 8.1 kg of DM/d on d 17 postcalving until the end of the experiment. Additionally, a mixture of 60 g of a rumen-protected choline supplement (providing 14.4 g of choline) and of 540 g of soybean meal or a (isoenergetic) mixture of 18 g of palm oil and 582 g of soybean meal (control) was offered individually in feed dispensers. Individual feed intake, milk yield, and body weight were recorded daily. Milk samples were analyzed weekly for fat, protein, and lactose content. Blood was sampled at wk −3, d 1, d 4, d 7, d 10, wk 2, wk 3, and wk 6 and analyzed for glucose, nonesterified fatty acids, and β-hydroxybutyric acid. Liver biopsies were taken from 8 randomly selected pairs of cows at wk −3, wk 1, wk 4, and wk 6 and analyzed for triacylglycerol concentration. We found that choline supplementation increased DM intake from 14.4 to 16.0 kg/d and, hence, net energy intake from 98.2 to 109.1 MJ/d at the intercept of the lactation curve at 1 day in milk (DIM), but the effect of choline on milk protein yield gradually decreased during the course of the study. Choline supplementation had no effect on milk yield, milk fat yield, or lactose yield. Milk protein yield was increased from 1.13 to 1.26 kg/d at the intercept of the lactation curve at 1 DIM, but the effect of choline on milk protein yield gradually decreased during the course of the study. Choline supplementation was associated with decreased milk fat concentration at the intercept of the lactation curve at 1 DIM, but the effect of choline on milk fat concentration gradually decreased as lactation progressed. Choline supplementation had no effect on energy-corrected milk yield, energy balance, body weight, body condition score, and measured blood parameters. Choline supplementation decreased the concentration of liver triacylglycerol during the first 4 wk after parturition. Results from this study suggest that hepatic fat export in periparturient dairy cows is improved by choline supplementation during the transition period and this may potentially decrease the risk for metabolic disorders in the periparturient dairy cow.     

Effects of prepartum metabolizable protein supply and management strategy on lactational performance and blood biomarkers in dairy cows during early lactation

Our objective was to investigate the effects of prepartum metabolizable protein (MP) supply and management strategy on milk production and blood biomarkers in early lactation dairy cows. Ninety-six multigravida Holstein cows were used in a randomized complete block design study, blocked by calving date, and then assigned randomly to 1 of 3 treatments within block. Cows on the first treatment were fed a far-off lower MP diet [MP = 83 g/kg of dry matter (DM)] between ?55 and ?22 d before expected calving and then a close-up lower MP diet (MP = 83 g/kg of DM) until parturition (LPLP). Cows on the second treatment were fed the far-off lower MP diet between ?55 to ?22 d before expected parturition and then a prepartum higher MP diet (MP = 107 g/kg of DM) until calving (LPHP). Cows on the third treatment had a shortened 43-d dry period and were fed the prepartum higher MP diet from dry-off to parturition (SDHP). After calving, cows received the same fresh diet from d 0 to 14 and the same high diet from d 15 to 84. Data were analyzed separately for wk ?6 to ?1 and wk 1 to 12, relative to parturition. Dry matter intake from wk ?6 to ?1 was not different between LPHP and LPLP and increased for SDHP compared with LPLP. In contrast, dry matter intake for wk 1 to 12 postpartum did not change for LPHP versus LPLP or for SDHP versus LPLP. Compared with LPLP cows, LPHP cows had lower energy-corrected milk yield and tended to have decreased milk fat yield during wk 1 to 12 of lactation. Conversely, yields of energy-corrected milk and milk fat and protein were similar for SDHP compared with LPLP. Plasma urea N during wk ?3 to ?1 increased for LPHP versus LPLP and for SDHP versus LPLP; however, no differences in plasma urea N were observed postpartum. Elevated prepartum MP supply did not modify circulating total fatty acids, β-hydroxybutyrate, total protein, albumin, or aspartate aminotransferase during the prepartum and postpartum periods. Increased MP supply prepartum combined with a shorter dry period (SDHP vs. LPLP) tended to increase whole-blood β-hydroxybutyrate postpartum; however, other blood metabolites were not affected. Taken together, under the conditions of this study, elevated MP supply in close-up diets reduced milk production without affecting blood metabolites in multiparous dairy cows during early lactation. A combination of a shorter dry period and increased prepartum MP supply (i.e., SDHP vs. LPLP) improved prepartum dry matter intake without modifying energy-corrected milk yield and blood biomarkers in early lactation cows.     

Postpartum supplementation of fermented ammoniated condensed whey improved feed efficiency and plasma metabolite profile

Postpartum dietary supplementation of gluconeogenic precursors may improve the plasma metabolite profile of dairy cows, reducing metabolic disorders and improving lactation performance. The objective of this trial was to examine the effects of supplementation with fermented ammoniated condensed whey (FACW) postpartum on lactation performance and on profile of plasma metabolites and hormones in transition dairy cows. Individually fed multiparous Holstein cows were blocked by calving date and randomly assigned to control (2.9% dry matter of diet as soybean meal; n = 20) or FACW (2.9% dry matter of diet as liquid GlucoBoost, Fermented Nutrition, Luxemburg, WI; n = 19) dietary treatments. Treatments were offered from 1 to 45 d in milk (DIM). Cows were milked twice a day. Dry matter intake and milk yield were recorded daily and averaged weekly. Individual milk samples from 2 consecutive milkings were obtained once a week for component analysis. Rumen fluid was collected (n = 3 cows/treatment) at 4 time points per day at 7 and 21 DIM. Blood samples were collected within 1 h before feeding time for metabolite analysis and hyperketonemia diagnosis. Supplementation of FACW improved feed efficiency relative to control; this effect may be partially explained by a marginally significant reduction in dry matter intake from wk 3 to 7 for FACW-supplemented cows with no detected FACW-driven changes in milk yield, milk protein yield, and milk energy output compared with control. Also, there was no evidence for differences in intake of net energy for lactation, efficiency of energy use, energy balance, or body weight or body condition score change from calving to 45 DIM between treatments. Supplementation of FACW shifted rumen measures toward greater molar proportions of propionate and butyrate, and lesser molar proportions of acetate and valerate. Cows supplemented with FACW had greater plasma glucose concentrations in the period from 3 to 7 DIM and greater plasma insulin concentrations compared with control. Plasma nonesterified fatty acid and β-hydroxybutyrate concentrations were decreased in cows supplemented with FACW compared with control cows in the period from 3 to 7 DIM. These findings indicate that FACW may have improved the plasma metabolite profile immediately postpartum in dairy cows. Additionally, supplementation of FACW resulted in improved feed efficiency as accessed by measures of milk output relative to feed intake.     

Response of Holstein cows to corn gluten meal used to increase undegradable protein in early or later lactation.

Supplemental corn gluten meal was used to raise CP by 1.1 to 1.5 percentage units and undegradable intake protein from 35 to 39% of CP in the corn-based diet of parity 1 or greater Holstein cows to study effects of undegradability, parity, stage of lactation, and interactions on DMI, milk yield and composition, BW, and related traits during complete lactations. Cows were assigned at calving to treatments (n = 30, 8 primiparous): control, supplement wk 1 to 8 postpartum (early), or supplement wk 9 to 44 postpartum (late). Total lactation means were not affected significantly by treatments. Supplementation with undegradable protein enhanced forage and, thus, total DMI in later lactation by pluriparous cows; it apparently spared BW loss wk 1 to 8 postpartum and enhanced BW recovery thereafter in first lactation cows with no effect in older cows. Effects of supplementation on milk yield were small, and they were negative in early lactation and generally positive in late lactation; effects were positive on fat test in early lactation for both parity categories but distinctly negative for parity 1 cows in late lactation. Supplementation of undegradable protein in late lactation also decreased milk protein content in parity 1 cows and raised it in older cows. Data suggest that Lys may have been first-limiting, followed by Ile in early lactation and Met in late lactation, and that AA adequacy may be more important than undegradability in ration protein balancing. For most traits measured, treatment by parity interactions were significant, indicating that parity 1 cows did not respond in the same way as older ones to protein supplementation.     

Blood calcium concentration and performance in periparturient and early lactating dairy cows is influenced by plant bioactive lipid compounds

Previous studies ex vivo suggested that plant bioactive lipid compounds (PBLC) can increase ruminal calcium absorption. Therefore, we hypothesized that PBLC feeding around calving may potentially counteract hypocalcemia and support performance in postpartum dairy cows. The corresponding aim of the study was to investigate the effect of PBLC feeding on blood minerals in Brown Swiss (BS) and hypocalcemia-susceptible Holstein Friesian (HF) cows during the period from d −2 to 28 relative to calving and on milk performance until d 80 of lactation. A total of 29 BS cows and 41 HF cows were divided each into a control (CON) and PBLC treatment group. The latter was supplemented with 1.7 g/d menthol-rich PBLC from 8 d before expected calving to 80 d postpartum. Milk yield and composition, body condition score and blood minerals were measured. Feeding PBLC induced a significant breed × treatment interaction for iCa, supporting that PBLC increased iCa exclusively in HF cows; the increase was 0.03 mM over the whole period and 0.05 mM from d 1 to 3 after calving. Subclinical hypocalcemia was seen in one BS-CON and 8 HF-CON cows and 2 BS-PBLC and 4 HF-PBLC cows. Clinical milk fever was detected only in HF cows (2 HF-CON and one HF-PBLC). Other tested blood minerals, such as sodium, chloride, and potassium, as well as blood glucose, were neither affected by PBLC feeding nor breed, nor were their 2-way interactions, except for higher sodium levels in PBLC cows on d 21. Body condition score showed no effect of treatment, except for a lower body condition score in BS-PBLC compared with BS-CON at d 14. Dietary PBLC increased milk yield, milk fat yield, and milk protein yield at 2 consecutive dairy herd improvement test days. As indicated by treatment × day interactions, energy-corrected milk yield and milk lactose yield were increased by PBLC on the first test day only, and milk protein concentration decreased from test d 1 to test d 2 in CON only. The concentrations of fat, lactose, and urea, as well as somatic cell count, were not affected by treatment. The weekly milk yield over the first 11 wk of lactation was 29.5 kg/wk higher for PBLC versus CON across breeds. It is concluded that the applied PBLC induced a small but measurable improvement of calcium status in HF cows in the study period and had additional positive effects on milk performance in both breeds.     

Effects of dry period length and concentrate protein content in late lactation on body condition score change and subsequent lactation performance of thin high genetic merit dairy cows

Improving body condition score of thin cows in late lactation is necessary, because cows that are thin at drying off exhibit decreased fertility postpartum and are at increased risk of disease and of being culled in the subsequent lactation. Offering a diet low in crude protein (CP) content in late lactation may help to improve body condition score (BCS) at drying off, whereas imposing an extended dry period (EDP) has been advocated as another way to increase BCS at calving. To test these hypotheses, 65 thin cows (mean BCS 2.25 at 14 wk precalving) were managed on 1 of 3 treatments between 13 and 9 wk prepartum: normal protein control {NP; grass silage + 5 kg/d of a normal protein concentrate [228 g of CP/kg of dry matter (DM)]}, low protein [LP; grass silage + 5 kg/d of a low-protein concentrate (153 g of CP/kg of DM)], or EDP (cows dried off at 13 wk precalving and offered a grass silage-only diet). Both NP and LP cows were dried off at wk 8 prepartum, after which all cows were offered a grass silage-only diet until calving. After calving, all cows were offered a common diet (supplying 11.1 kg of concentrate DM/cow per day) for 19 wk. Between 13 and 9 wk prepartum, LP cows had lower DM intake, milk yield, and body weight than NP cows. Whereas EDP cows had lower serum β-hydroxybutyrate and fatty acid concentrations than those of NP cows, BCS at wk 9 prepartum did not differ between treatments. Cows on the LP treatment continued to have lower DMI and BW than those of NP and EDP cows between 8 wk prepartum and calving, but only EDP cows had a higher BCS at calving. Treatment did not affect calving difficulty score or calf birth weight. Although all cows were offered a common diet postpartum, cows on the LP treatment had lower DM intake and milk fat + plus protein yield than cows on any other treatment during the 19-wk period postpartum, but we found no differences in any postpartum indicator of body tissue reserves. The treatments imposed from wk 13 to 9 prepartum had no effect on any fertility or health parameters examined postpartum. Extending the dry period for thin cows improved their BCS at calving but did not allow these cows to achieve the target BCS of 2.75, and we found no beneficial effects of this treatment on cow performance postpartum. Offering a lower-protein diet to thin cows in late lactation did not improve BCS at calving above that of cows on a normal protein diet, but had unexplained long-term negative effects on cow performance.