Energy intake in late gestation affects blood metabolites in early lactation independently of milk production in dairy cows

The present experiment examined the effect of offering either a high- (H) or low- (L) energy-density diet in late gestation and early lactation on physiological parameters, body condition score (BCS) and milk production in early lactation. In all, 40 multiparous Holstein cows were randomly allocated to one of four treatments in a 2 × 2 factorial design, where the factors were H- or L-energy density in a total mixed ration (TMR) both pre- and post-calving. Consequently, there were four treatment groups: HH, HL, LL and LH. The pre-calving treatment was initiated 100 days prior to expected calving; the H TMR was fed ad libitum whereas the L TMR was restricted to 10 kg dry matter/day during late lactation, and to approximately 75% of energy requirements from drying off until calving. Both diets were offered ad libitum post-calving. Feeding diet H compared to L pre-calving led to higher BCS at calving (2.68 v. 2.34, P < 0.01). Energy corrected milk yield and energy-intake post-calving were not affected by pre-calving diets. Changes in BCS and blood concentrations of non-esterified fatty acids, beta-hydroxybutyrate and glucose in early lactation showed that cows offered diet H pre-calving generally mobilised more body reserves compared to cows offered diet L pre-calving. An interaction between pre- and post-calving diets showed that cows offered diet H pre-calving had lower body tissue mobilisation when offered diet H post-calving compared to diet L. Cows offered diet L pre-calving, did not mobilise differently whether they were offered diet H or L post-calving. The pre- and post-calving diets had no effect on liver triacylglycerol, whereas liver glycogen was higher in cows on treatment HH compared to the other three treatments. Collectively, these results indicate that overfeeding should be avoided in late gestation and that a high-energy-density diet is desirable in early lactation in order to obtain a more favourable metabolic profile.     

Effects of forage NDF content and body condition score on forage intake by Holstein-Friesian dairy cows in the dry period

This study used individual weekly results for 160 non-lactating Holstein-Friesian dairy cows in the last 5 weeks of gestation to develop regression equations based on forage NDF content and individual body condition score (BCS) for predicting dry matter (DM) intake. Results were used from treatments in which cows received the same forage and no concentrates throughout the dry period. Ten different conserved forages, either grass silages or mixtures of grass silage and barley straw, were fed in six different experiments and forage NDF ranged from 452 to 689 g/kg DM. On average cows gained 390 g live weight per day, which is less than conceptus growth at this stage - suggesting some mobilisation of maternal tissues to support conceptus growth. BCS remained unchanged at 2.5 over the dry period. DM intake declined from 10.79 kg/day 5 weeks before calving to 9.32 kg/day in the week before calving, with half of this decline occurring in the final week before calving. Intake as a percentage of live weight was moderately predicted (R2 = 0.61 for the entire period) from measures of diet composition (NDF) and cow state (BCS). There were highly significant negative effects of forage NDF and increased BCS on DM intake. The effect of BCS on DM intake was greatly reduced in the week before calving, possibly as a result of a change in metabolic priorities from gaining to losing body reserves.     

Adaptation and evaluation of the GrazeIn model of grass dry matter intake and milk yield prediction for grazing dairy cows

The prediction of grass dry matter intake (GDMI) and milk yield (MY) are important to aid sward and grazing management decision making. Previous evaluations of the GrazeIn model identified weaknesses in the prediction of GDMI and MY for grazing dairy cows. To increase the accuracy of GDMI and MY prediction, GrazeIn was adapted, and then re-evaluated, using a data set of 3960 individual cow measurements. The adaptation process was completed in four additive steps with different components of the model reparameterised or altered. These components were: (1) intake capacity (IC) that was increased by 5% to reduce a general GDMI underprediction. This resulted in a correction of the GDMI mean and a lower relative prediction error (RPE) for the total data set, and at all stages of lactation, compared with the original model; (2) body fat reserve (BFR) deposition from 84 days in milk to next calving that was included in the model. This partitioned some energy to BFR deposition after body condition score nadir had been reached. This reduced total energy available for milk production, reducing the overprediction of MY and reducing RPE for MY in mid and late lactation, compared with the previous step. There was no effect on predicted GDMI; (3) The potential milk curve was reparameterised by optimising the rate of decrease in the theoretical hormone related to secretory cell differentiation and the basal rate of secretory cell death to achieve the lowest possible mean prediction error (MPE) for MY. This resulted in a reduction in the RPE for MY and an increase in the RPE for GDMI in all stages of lactation compared with the previous step; and (4) finally, IC was optimised, for GDMI, to achieve the lowest possible MPE. This resulted in an IC correction coefficient of 1.11. This increased the RPE for MY but decreased the RPE for GDMI compared with the previous step. Compared with the original model, modifying this combination of four model components improved the prediction accuracy of MY, particularly in late lactation with a decrease in RPE from 27.8% in the original model to 22.1% in the adapted model. However, testing of the adapted model using an independent data set would be beneficial and necessary to make definitive conclusions on improved predictions.     

An individual reproduction model sensitive to milk yield and body condition in Holstein dairy cows

To simulate the consequences of management in dairy herds, the use of individual-based herd models is very useful and has become common. Reproduction is a key driver of milk production and herd dynamics, whose influence has been magnified by the decrease in reproductive performance over the last decades. Moreover, feeding management influences milk yield (MY) and body reserves, which in turn influence reproductive performance. Therefore, our objective was to build an up-to-date animal reproduction model sensitive to both MY and body condition score (BCS). A dynamic and stochastic individual reproduction model was built mainly from data of a single recent long-term experiment. This model covers the whole reproductive process and is composed of a succession of discrete stochastic events, mainly calving, ovulations, conception and embryonic loss. Each reproductive step is sensitive to MY or BCS levels or changes. The model takes into account recent evolutions of reproductive performance, particularly concerning calving-to-first ovulation interval, cyclicity (normal cycle length, prevalence of prolonged luteal phase), oestrus expression and pregnancy (conception, early and late embryonic loss). A sensitivity analysis of the model to MY and BCS at calving was performed. The simulated performance was compared with observed data from the database used to build the model and from the bibliography to validate the model. Despite comprising a whole series of reproductive steps, the model made it possible to simulate realistic global reproduction outputs. It was able to well simulate the overall reproductive performance observed in farms in terms of both success rate (recalving rate) and reproduction delays (calving interval). This model has the purpose to be integrated in herd simulation models to usefully test the impact of management strategies on herd reproductive performance, and thus on calving patterns and culling rates.     

Predicting grass dry matter intake,milk yield and milk fat and protein yield of spring calving grazing dairy cows during the grazing season

Predicting the grass dry matter intake (GDMI), milk yield (MY) or milk fat and protein yield (milk solids yield (MSY)) of the grazing dairy herd is difficult. Decisions with regard to grazing management are based on guesstimates of the GDMI of the herd, yet GDMI is a critical factor influencing MY and MSY. A data set containing animal, sward, grazing management and concentrate supplementation variables recorded during weeks of GDMI measurement was used to develop multiple regression equations to predict GDMI, MY and MSY. The data set contained data from 245 grazing herds from 10 published studies conducted at Teagasc, Moorepark. A forward stepwise multiple regression technique was used to develop the multiple regression equations for each of the dependent variables (GDMI, MY, MSY) for three periods during the grazing season: spring (SP; 5 March to 30 April), summer (SU; 1 May to 31 July) and autumn (AU; 1 August to 31 October). The equations generated highlighted the importance of different variables associated with GDMI, MY and MSY during the grazing season. Peak MY was associated with an increase in GDMI, MY and MSY during the grazing season with the exception of GDMI in SU when BW accounted for more of the variation. A higher body condition score (BCS) at calving was associated with a lower GDMI in SP and SU and a lower MY and MSY in all periods. A higher BCS was associated with a higher GDMI in SP and SU, a higher MY in SU and AU and a higher MSY in all periods. The pre-grazing herbage mass of the sward (PGHM) above 4 cm was associated with a quadratic effect on GDMI in SP, on MY in SP and SU and on MSY in SU. An increase in daily herbage allowance (DHA) above 4 cm was associated with an increase in GDMI in AU, an increase in MY in SU and AU and MSY in AU. Supplementing grazing dairy cows with concentrate reduced GDMI and increased MY and MSY in all periods. The equations generated can be used by the Irish dairy industry during the grazing season to predict the GDMI, MY and MSY of grazing dairy herds.     

Modeling homeorhetic trajectories of milk component yields,body composition and dry-matter intake in dairy cows: Influence of parity,milk production potential and breed

The control of nutrient partitioning is complex and affected by many factors, among them physiological state and production potential. Therefore, the current model aims to provide for dairy cows a dynamic framework to predict a consistent set of reference performance patterns (milk component yields, body composition change, dry-matter intake) sensitive to physiological status across a range of milk production potentials (within and between breeds). Flows and partition of net energy toward maintenance, growth, gestation, body reserves and milk components are described in the model. The structure of the model is characterized by two sub-models, a regulating sub-model of homeorhetic control which sets dynamic partitioning rules along the lactation, and an operating sub-model that translates this into animal performance. The regulating sub-model describes lactation as the result of three driving forces: (1) use of previously acquired resources through mobilization, (2) acquisition of new resources with a priority of partition towards milk and (3) subsequent use of resources towards body reserves gain. The dynamics of these three driving forces were adjusted separately for fat (milk and body), protein (milk and body) and lactose (milk). Milk yield is predicted from lactose and protein yields with an empirical equation developed from literature data. The model predicts desired dry-matter intake as an outcome of net energy requirements for a given dietary net energy content. The parameters controlling milk component yields and body composition changes were calibrated using two data sets in which the diet was the same for all animals. Weekly data from Holstein dairy cows was used to calibrate the model within-breed across milk production potentials. A second data set was used to evaluate the model and to calibrate it for breed differences (Holstein, Danish Red and Jersey) on the mobilization/reconstitution of body composition and on the yield of individual milk components. These calibrations showed that the model framework was able to adequately simulate milk yield, milk component yields, body composition changes and dry-matter intake throughout lactation for primiparous and multiparous cows differing in their production level.     

Towards a better understanding of the respective effects of milk yield and body condition dynamics on reproduction in Holstein dairy cows

The overall reproductive performance has decreased over the last decades, involving changes in cyclicity, oestrous behaviour and fertility. High milk yield (MY), low body condition score (BCS) and large body condition (BC) loss have been identified as risk factors. However, these effects are often confounded, as high MY and body lipid reserve mobilization are correlated. The aim of this study was to evaluate the respective effects of MY and BC on post-partum ovarian cyclicity, oestrus and fertility of Holstein cows. This study provides novel information, as MY and BC change were uncoupled in the overall dataset that included 98 lactations and milk progesterone profiles. Cows were assigned to two feeding-level groups: high feed, which achieved high MY and moderate BC loss throughout lactation (8410 kg, -1.17 unit from calving to nadir BCS), and low feed, which limited MY and triggered a large BC loss (5719 kg, -1.54 unit). MY and BC had different effects at different stages of the reproductive process. Cyclicity as well as non-fertilization and early embryo mortality were mainly driven by body lipid reserves, whereas oestrous behaviour and late embryo mortality were related to MY. The results point to possible uncoupling between cyclicity, oestrus and early and late embryo survival allowing compensation along the reproductive process and leading to similar final reproductive performance. In compact calving systems, which require high pregnancy rates within a short period, higher MY strategies appear unsuitable even where BCS is maintained, owing to depressed oestrous behaviour and probably increased late embryo mortality, which delays rebreeding. Similarly, strategies that compromise cyclicity and fertility by excessively low BCS are unsuitable.     

Effects of continuous lactation and short dry periods on mammary function and animal health

The dry period is required to facilitate cell turnover in the bovine mammary gland in order to optimize milk yield in the next lactation. Traditionally, an 8-week dry period has been a standard management practice for dairy cows based on retrospective analyses of milk yields following various dry period lengths. However, as milk production per cow has increased, transitioning cows from the nonlactating state to peak milk yield has grown more problematic. This has prompted new studies on dry period requirements for dairy cows. These studies indicate a clear parity effect on dry period requirement. First parity animals require a 60-day dry period, whereas lactations following later parities demonstrate no negative impact with 30-day dry period or even eliminating the dry period when somatotropin (ST) is also used to maintain milk yields. Shortened dry periods in first parity animals were associated with reduced mammary cell turnover during the dry period and early lactation and increased numbers of senescent cells and reduced functionality of lactating alveolar mammary cells postpartum. Use of ST and increased milking frequency postpartum reduced the impact of shortened dry periods. The majority of new intramammary infections occur during the dry period and persist into the following lactation. There is therefore the possibility of altering mastitis incidence by modifying or eliminating the dry period in older parity animals. As the composition of mammary secretions including immunoglobulins may be reduced when the dry period is reduced or eliminated, there is the possibility that the immune status of cows during the peripartum period is influenced by the length of the dry period.     

Effects of rumen-protected choline supplementation on milk production and choline supply of periparturient dairy cows

The objective of the present study was to determine the effects of rumen-protected choline (RPC) supplementation on body condition, milk production and milk choline content during the periparturient period. Thirty-two Holstein cows were allocated into two groups (RPC group - with RPC supplementation, and control group - without RPC supplementation) 28 days before the expected calving. Cows were fed the experimental diet from 21 days before expected calving until 60 days of lactation. The daily diet of the RPC group contained 100 g of RPC from 21 days before calving until calving and 200 g RPC after calving for 60 days of lactation, which provided 25 g and 50 g per day choline, respectively. Body condition was scored on days -21, 7, 35 and 60 relative to calving. Milk production was measured at every milking; milk fat, protein and choline content were determined on days 7, 35 and 60 of lactation. Body condition was not affected by RPC supplementation. Milk yield was 4.4 kg higher for the group of cows receiving supplementary choline during the 60 days experimental period and 4% fat-corrected milk production was also increased by 2.5 kg/day. Milk fat content was not altered by treatment, but fat yield was increased by 0.10 kg/day as a consequence of higher milk yield in the RPC-treated group. Milk protein content tended to increase by RPC supplementation and a 0.18 kg/day significant improvement of protein yield was detected. Milk choline content increased in both groups after calving as the lactating period advanced. However, milk choline content and choline yield were significantly higher in the RPC group than in the control group. The improved milk choline and choline yield provide evidence that some of the applied RPC escaped ruminal degradation, was absorbed from the small intestine and improved the choline supply of the cows and contributed to the changes of production variables.     

e-Cow: an animal model that predicts herbage intake, milk yield and live weight change in dairy cows grazing temperate pastures, with and without supplementary feeding

This animal simulation model, named e-Cow, represents a single dairy cow at grazing. The model integrates algorithms from three previously published models: a model that predicts herbage dry matter (DM) intake by grazing dairy cows, a mammary gland model that predicts potential milk yield and a body lipid model that predicts genetically driven live weight (LW) and body condition score (BCS). Both nutritional and genetic drives are accounted for in the prediction of energy intake and its partitioning. The main inputs are herbage allowance (HA; kg DM offered/cow per day), metabolisable energy and NDF concentrations in herbage and supplements, supplements offered (kg DM/cow per day), type of pasture (ryegrass or lucerne), days in milk, days pregnant, lactation number, BCS and LW at calving, breed or strain of cow and genetic merit, that is, potential yields of milk, fat and protein. Separate equations are used to predict herbage intake, depending on the cutting heights at which HA is expressed. The e-Cow model is written in Visual Basic programming language within Microsoft Excel^R. The model predicts whole-lactation performance of dairy cows on a daily basis, and the main outputs are the daily and annual DM intake, milk yield and changes in BCS and LW. In the e-Cow model, neither herbage DM intake nor milk yield or LW change are needed as inputs; instead, they are predicted by the e-Cow model. The e-Cow model was validated against experimental data for Holstein–Friesian cows with both North American (NA) and New Zealand (NZ) genetics grazing ryegrass-based pastures, with or without supplementary feeding and for three complete lactations, divided into weekly periods. The model was able to predict animal performance with satisfactory accuracy, with concordance correlation coefficients of 0.81, 0.76 and 0.62 for herbage DM intake, milk yield and LW change, respectively. Simulations performed with the model showed that it is sensitive to genotype by feeding environment interactions. The e-Cow model tended to overestimate the milk yield of NA genotype cows at low milk yields, while it underestimated the milk yield of NZ genotype cows at high milk yields. The approach used to define the potential milk yield of the cow and equations used to predict herbage DM intake make the model applicable for predictions in countries with temperate pastures.     

Effects of feeding propylene glycol on dry matter intake, lactation performance, energy balance and blood metabolites in early lactation dairy cows

The objectives of this study were to evaluate effects of feeding propylene glycol (PG) on feed intake, milk yield and milk composition, blood metabolites and energy balance in Holstein dairy cows from 1 to 63 days in milk. Thirty-two multiparous cows, blocked by lactation number, previous 305-day milk production and expected calving date, were arranged into four groups in a randomized block design. Treatments were: control, low PG, medium PG and high PG with 0, 150, 300 and 450 ml PG per cow per day, respectively. The supplement of food grade PG (0.998 g/g PG) was hand-mixed into the top one-third of the daily ration. Cows were fed ad libitum a total mixed ration consisting of forage and concentrate (50 : 50, dry matter basis). Feed intake, milk yield and milk components were not affected (P > 0.05) by PG supplementation. Overall, body weight (BW) loss tended (P < 0.08) to be linearly reduced, and energy status was linearly improved with increasing PG supplementation. Concentrations of glucose in plasma were higher for cows fed PG relative to control (55.6 v. 58.9 mg/dl) and linearly increased (P < 0.01) with increasing PG supplementation. Plasma concentrations of non-esterified fatty acids and beta-hydroxybutyrate were linearly increased, but urine acetoacetate concentration was quadratically changed with the highest for control diet and the lowest for 450 ml/day of PG. These results indicated that supplementation of PG in the early lactating cow diets had minimal effects on feed intake and milk production, but may potentially reduce contents of milk fat and milk protein. Supplementation of early lactating dairy cow diets with PG is beneficial in terms of improving energy status and reducing BW loss.     

Effects of dry period length on milk production and energy balance in two cow breeds

Shortening the dry period (DP) has been proposed as a strategy to improve energy balance (EB) in cows in early lactation. This study evaluated the effects of shortening the DP on milk yield (MY), EB and residual feed intake (RFI) in two breeds; Swedish Red (SR) and Swedish Holstein (SH). Cows were blocked by breed and parity and then randomly assigned to one of two treatments; short DP of 4 weeks (4W, n=43) or conventional DP of 8 weeks (8W, n=34). Cows were kept and fed under the same conditions, except for the 4 weeks when the 4W group were still lactating prepartum and thus kept with the lactating cows. Milk yield and BW were recorded and body condition score (BCS) was rated from 10 weeks prepartum to 12 weeks postpartum. Dry matter intake (DMI) was recorded for lactating cows postpartum. Milk yield was reduced by 6.75 kg/day during the first 12 weeks postpartum (P<0.001) for the 4W cows compared with 8W cows, but there was no significant difference in total MY (3724 kg compared with 3684 kg, P=0.7) when the milk produced prepartum was included. Protein content was higher in 4W cows (3.42%) than in 8W cows (3.27%) (P<0.001) postpartum. In the 8W group, cows lost more BCS after calving (P<0.05). Cows of SR breed had higher BCS than cows of SH breed (SR=3.7, SH=3.2, P<0.001), but no differences in BW were found between breed and treatment. Energy balance was improved for cows in the 4W group (P<0.001), while feed efficiency, expressed as RFI, was reduced for 4W cows than for 8W cows (5.91 compared with −5.39, P<0.01). Shortening the DP resulted in improved EB postpartum with no difference between the breeds and no milk losses when including the milk produced prepartum.     

Effects of partially replacing barley or corn with raw and micronised CDC SO-I oats on productive performance of lactating dairy cows

Recently, a new genotype of oat (cv. CDC SO-I, containing low-hull lignin and high-fat groat), has been developed. The objective of this study was to determine the effects of partially replacing barley and corn with the new oat and its micronisation on lactating performance of dairy cows. In a double 4 × 4 Latin square design, eight lactating dairy cows (732 ± 46 kg body weight [BW]; parity 4 ± 2) received total mixed rations with a forage-to-concentrate ratio of 50:50 (DM basis). The four treatments were: T1, barley only (control); T2, raw oat, replacing 42% barley of T1; T3, micronised oat, replacing 42% barley of T1; and T4, raw oat and corn blend, replacing 100% barley of T1. The results showed that dairy cows fed the new oats (T2, T3) produced more fat (p < 0.05) and more fat corrected milk (p < 0.10) than cows fed barley only (T1). The performance of cows fed the new oat and corn blend (T4) was not significantly different from other treatments. The micronisation significantly reduced protein degradability (74 vs. 63%, p < 0.05), but increased starch degradability (87 vs. 93%, p < 0.05) of the new oat. However, the overall results suggested that micronisation did not show a significant impact on milk production. The newly developed CDC SO-I oat can replace 42% barley (in T1) as a concentrate supplement in dairy total mixed rations with an increased yield of milk fat and fat corrected milk.     

Dietary carbohydrate composition modifies the milk N efficiency in late lactation cows fed low crude protein diets

Nitrogen emissions from dairy cows can be readily decreased by lowering the dietary CP concentration. The main objective of this work was to test whether the milk protein yield reduction associated with low N intakes could be partially compensated for by modifying the dietary carbohydrate composition (CHO). The effects of CHO on digestion, milk N efficiency (milk N/N intake; MNE) and animal performance were studied in four Jersey cows fed 100% or 80% of the recommended protein requirements using a 4×4 Latin square design. Four iso-energetic diets were formulated to two different CHO sources (starch diets with starch content of 34.3% and NDF at 32.5%, and fiber diets with starch content of 5.5% and NDF at 49.1%) and two CP levels (Low=12.0% and Normal=16.5%). The apparent digestible organic matter intake (DOMI) and the protein supply (protein digestible in the small intestine; PDIE) were similar between starch and fiber diets. As planned, microbial N flow (MNF) to the duodenum, estimated from the urinary purine derivatives (PD) excretion, was similar between Low and Normal CP diets. However, the MNF and the efficiency of microbial synthesis (g of microbial N/kg apparently DOMI) were higher for starch v. fiber diets. Milk and milk N fractions (CP, true protein, non-protein N (NPN)) yield were higher for starch compared with fiber diets and for Normal v. Low CP diets. Fecal N excretion was similar across dietary treatments. Despite a higher milk N ouput with starch v. fiber diets, the CHO modified neither the urinary N excretion nor the milk urea-N (MUN) concentration. The milk protein yield relative to both N and PDIE intakes was improved with starch compared with fiber diets. Concentrations of β-hydroxybutyrate, urea and Glu increased and those of glucose and Ala decreased in plasma of cows fed starch v. fiber diets. On the other hand, plasma concentration of albumin, urea, insulin and His increased in cows fed Normal compared with Low CP diets. This study showed that decreasing the dietary CP proportion from 16.5% to 12.0% increases and decreases considerably the MNE and the urinary N excretion, respectively. Moreover, present results show that at similar digestible OM and PDIE intakes, diets rich in starch improves the MNE and could partially compensate for the negative effects of Low CP diets on milk protein yield.     

Comparison of performance and metabolism from late pregnancy to early lactation in dairy cows with elevated v. normal body condition at dry-off

Excessive mobilization of body reserves during the transition from pregnancy to lactation imposes a risk for metabolic diseases on dairy cows. We aimed to establish an experimental model for high v. normal mobilization and herein characterized performance, metabolic and endocrine changes from 7 weeks antepartum (a.p.) to 12 weeks postpartum (p.p.). Fifteen weeks a.p., 38 pregnant multiparous Holstein cows were allocated to two groups that were fed differently to reach either high or normal body condition scores (HBCS: 7.2 NE_L MJ/kg dry matter (DM); NBCS: 6.8 NE_L MJ/kg DM) at dry-off. Allocation was also based on differences in body condition score (BCS) in the previous and the ongoing lactation that was further promoted by feeding to reach the targeted BCS and back fat thickness (BFT) at dry-off (HBCS: >3.75 and >1.4 cm; NBCS: <3.5 and <1.2 cm). Thereafter, both groups were fed identical diets. Blood samples were drawn weekly from 7 weeks a.p. to 12 weeks p.p. to assess the serum concentrations of metabolites and hormones. The HBCS cows had greater BCS, BFT and BW than the NBCS cows throughout the study and lost more than twice as much BFT during the first 7 weeks p.p. compared with NCBS. Milk yield and composition were not different between groups, except that lactose concentrations were greater in NBSC than in HBCS. Feed intake was also greater in NBCS, and NBCS also reached a positive energy balance earlier than HBCS. The greater reduction in body mass in HBCS was accompanied by greater concentrations of non-esterified fatty acids, and β-hydroxybutyrate in serum after calving than in NBCS, indicating increased lipomobilization and ketogenesis. The mean concentrations of insulin across all time-points were greater in HBCS than in NBCS. In both groups, insulin and IGF-1 concentrations were lower p.p than in a.p. Greater free thyroxine (fT4) concentrations and a lower free 3-3′-5-triiodothyronine (fT3)/fT4 ratio were observed in HBCS than in NBCS a.p., whereas p.p. fT3/fT4 ratio followed a reverse pattern. The variables indicative for oxidative status had characteristic time courses; group differences were limited to greater plasma ferric reducing ability values in NBSC. The results demonstrate that the combination of pre-selection according to BCS and differential feeding before dry-off to promote the difference was successful in obtaining cows that differ in the intensity of mobilizing body reserves. The HBCS cows were metabolically challenged due to intense mobilization of body fat, associated with reduced early lactation dry matter intake and compromised antioxidative capacity.     

Effects of alfalfa silage storage structure and roasting corn on ruminal digestion and microbial CP synthesis in lactating dairy cows

The objective of this experiment was to quantify the effects of unroasted or roasted ground-shelled corn (GSC), when fed with alfalfa ensiled in bag, bunker, or O2-limiting tower silos on ruminal digestion and microbial CP synthesis in lactating dairy cows. The roasted corn was heat-treated in a propane-fired roasting system. Alfalfa was harvested as second cutting from fields with regrowth of the same maturity. A portion of each field was allotted to each silo. The diets with 3 × 2 factorial arrangement of treatments were fed to six multiparous rumen-cannulated Holstein cows in a cyclic change-over design with five 21-day periods. Experimental diets were comparable and averaged (on dry matter (DM) basis): 410 g/kg alfalfa silage (AS), 150 g/kg corn silage, 350 g/kg GSC, 50 g/kg soybean meal, 40 g/kg roasted soybeans, 177 g/kg CP, 264 g/kg NDF and 250 g/kg starch. Nutrient flow was quantified by the omasal sampling technique with use of three markers (Co, Yb and indigestible NDF). Continuous infusion of 10% atom excess (15NH4)2SO4 was used to label microbial CP. None of the interactions between storage structure of dietary AS and corn type were significant. DM intake was not different among dietary treatments, averaging 24.5 kg/day across diets. Means of ADF digested in the rumen for cows fed diets with AS from bag, bunker and O2-limiting tower silo were 2.1, 1.7 and 2.1 kg/day, respectively, and was lower in cows fed AS from the bunker silo. This response may partly be a reflection of the higher intake of ADF by cows fed AS ensiled in the O2-limiting tower silo compared with the bunker. There was a slightly greater supply of fermentable substrates for cows fed diets with roasted compared with unroasted GSC. The small increases in yield of milk protein and lactose observed in the previous production trial in cows fed diets containing roasted corn may have occurred because of greater supply of fermentable substrates.     

Effects of the level of feed intake and ergot contaminated concentrate on ruminal fermentation and on physiological parameters in cows

The aim of the present study was to examine the effects of ergot contaminated feed concentrate at differing levels of feed intake on ruminal fermentation, and on various physiological parameters of dairy cows. Twelve double fistulated (in the rumen and the proximal duodenum) Holstein Friesian cows were fed either a control diet (on a dry matter (DM) base: 60% maize silage, 40% concentrate) or a diet containing ergot alkaloids (concentrate contained 2.25% ergot resulting in an ergot alkaloid concentration of the daily ration between 505 and 620 (μg/kg DM) over a period of four weeks. Daily feed amounts were adjusted to the current performance which resulted in a dry matter intake (DMI) variation between 6.0 and 18.5 kg/day. The resulting ergot alkaloid intake varied between 4.1 and 16.3 (μg/kg body weight when the ergot contaminated concentrate was fed. Concentrations of isovalerate, propionate and ammonia nitrogen in the rumen fluid were significantly influenced by ergot feeding, and the amount of ruminally undegraded protein, as well as the fermentation of neutral detergent fibre, tended to increase with the ergot supplementation at higher levels of feed intake, which might indicate a shift in the microbial population. Other parameters of ruminal fermentation such as ruminai pH, fermented organic matter as a percentage of intake, or the amount of non-ammonia nitrogen measured at the duodenum were not significantly influenced by ergot feeding. The activities of liver enzymes (aspartate aminotransferase, γ-glutamyltransferase, glutamate dehydrogenase, creatine kinase) in the serum were not affected by ergot feeding. The rectal measured body temperature of the cows significantly increased after ergot administration (p=0.019). Thus, body temperature can be regarded as a sensitive parameter to indicate ergot exposure of dairy cows.     

Replacement of grass and maize silages with lucerne silage: effects on performance,milk fatty acid profile and digestibility in Holstein-Friesian dairy cows

In total, 20 multiparous Holstein-Friesian dairy cows received one of four diets in each of four periods of 28-day duration in a Latin square design to test the hypothesis that the inclusion of lucerne in the ration of high-yielding dairy cows would improve animal performance and milk fatty acid (FA) composition. All dietary treatments contained 0.55 : 0.45 forage to concentrates (dry matter (DM) basis), and within the forage component the proportion of lucerne (Medicago sativa), grass (Lolium perenne) and maize silage (Zea mays) was varied (DM basis): control (C)=0.4 : 0.6 grass : maize silage; L20=0.2 : 0.2 : 0.6 lucerne : grass : maize silage; L40=0.4 : 0.6 lucerne : maize silage; and L60=0.6 : 0.4 lucerne : maize silage. Diets were formulated to contain a similar CP and metabolisable protein content, with the reduction of soya bean meal and feed grade urea with increasing content of lucerne. Intake averaged 24.3 kg DM/day and was lowest in cows when fed L60 (P<0.01), but there was no effect of treatment on milk yield, milk fat or protein content, or live weight change, which averaged 40.9 kg/day, 41.0, 30.9 g/kg and 0.16 kg/day, respectively. Milk fat content of 18:2 c9 c12 and 18:3 c9 c12 c15 was increased (P<0.05) with increasing proportion of lucerne in the ration. Milk fat content of total polyunsaturated fatty acids was increased by 0.26 g/100 g in L60 compared with C. Plasma urea and β-hydroxybutyrate concentrations averaged 3.54 and 0.52 mmol/l, respectively, and were highest (P<0.001) in cows when fed L60 and lowest in C, but plasma glucose and total protein was not affected (P>0.05) by dietary treatment. Digestibility of DM, organic matter, CP and fibre decreased (P<0.01) with increasing content of lucerne in the diet, although fibre digestibility was similar in L40 and L60. It is concluded that first cut grass silage can be replaced with first cut lucerne silage without any detrimental effect on performance and an improvement in the milk FA profile, although intake and digestibility was lowest and plasma urea concentrations highest in cows when fed the highest level of inclusion of lucerne.     

Influence of estrus on dry matter intake,water intake and BW of dairy cows

The objectives of this study were to analyze whether dry matter intake (DMI), water intake (WI) and BW were influenced by estrus. A second objective was to determine whether correlations exist among these traits in non-estrous days. Data collection included 34 Holstein-Friesian cows from the research farm ‘Haus Riswick’ of the Agricultural Chamber North Rhine-Westphalia, Germany. On an individual basis, daily DMI and daily WI were measured automatically by a scale in the feeding trough and a WI monitoring system, respectively. BW was determined by a walk-through scale fitted with two gates – one in front and one behind the scale floor. Data were analyzed around cow’s estrus with day 0 (the day of artificial insemination leading to conception). Means during the reference period, defined as days −3 to −1 and 1 to 3, were compared with the means during estrus (day 0). DMI, WI and BW were affected by estrus. Of all cows, 85.3% and 66.7% had reduced DMI and WI, respectively, on day 0 compared with the reference period. Lower BW was detected in 69.2% of all cows relative to the reference period. During the reference period, average DMI, WI and BW were 23.0, 86.6 and 654.8 kg. A minimum DMI of 20.4 kg and a minimum BW of 644.2 kg were detected on the day of estrus, whereas the minimum WI occurred on the day before estrus. After estrus, DMI, WI and BW returned to baseline values. Intake of concentrated feed did not seem to be influenced by estrus. Positive correlations existed between daily DMI and daily WI (r=0.63) as well as between cows’ daily BW and daily WI (r=0.23). The results warrant further investigations to determine whether monitoring of DMI, WI and BW may assist in predicting estrus.     

Influence of energy and nutrient supply pre and post partum on performance of multiparous Simmental,Brown Swiss and Holstein cows in early lactation

A study was conducted to evaluate the effects of pre partum (PRE) and post partum (POST) dietary energy and nutrient supply (E) and their interactions on feed intake, performance and energy status in dairy cows of three breeds. In this experiment, the effects of three energy and nutrient supply levels (low (L), medium (M), high (H)), both pre-calving and post-calving, were investigated, using a 3×3 factorial arrangement of treatments. In both phases (84 days pre- and 105 days post-calving) E levels applied to a total of 81 multiparous cows of breeds Simmental (SI), Brown Swiss (BS) and Holstein–Friesian (HF; n=27 for each breed), were 75%, 100% and 125% of recommendations of the German Society of Nutrition Physiology (GfE). Dry matter intake (DMI) was restricted, if energy intake exceeded target values. Pre partum DMI and energy intake were different as designed, liveweight and body condition score (BCS) of SI cows were higher, but EB was lower, compared to BS and HF cows. Milk yield and composition were influenced by all three main experimental factors (E_PRE, E_POST, breed). Energy-corrected milk yield was 25.6, 28.6 and 30.1 kg/day for L_PRE, M_PRE and H_PRE as well as 21.5, 30.1 and 32.6 kg/day for L_POST, M_POST and H_POST, respectively. Numerically, only for milk protein content the interactions E_PRE×E_POST and E_PRE×breed reached significance. Impact of energy supply pre-calving was more pronounced when cows had lower energy supply post-calving and vice versa. On the other hand, milk yield response of cows to energy supply above requirements was greater for cows that were fed on a low energy level pre partum. Impact of energy level pre partum was higher for HF cows, showing that their milk production relies to a greater extent on mobilization of body reserves. Increasing energy supply pre partum led to a more negative energy balance post partum, mainly by increasing milk yield and content, whereas feed intake was slightly reduced. Increasing energy supply post partum enhanced milk yield as well as milk protein and lactose content. Calculated energy balance corresponded well with liveweight and BCS change. Response of milk yield to increasing energy supply followed the principle of diminishing returns, since energy was increasingly partitioned to body retention. Increasing energy supply pre partum enhances milk yield and content post partum, but exacerbates negative energy balance and its consequences.