The effects of crossbreeding with Norwegian Red dairy cattle on common postpartum diseases,fertility and body condition score

Norwegian Red bulls, selected in Norway, have been used for crossbreeding with Israeli Holstein on commercial farms. The aim of this project was to investigate Norwegian Red×Israeli Holstein (NRX) performance to see how the daughters perform in a different environment than the one their sires were selected in. This was done by comparing health and fertility of NRX with their Israeli Holstein (HO) counterparts. The data consisted of 71 911 HO records and 10 595 NRX records from 33 855 cows in 23 Israeli dairy herds. Calving events took place between 2006 and 2016. Five postpartum disorders (mean frequency in HO v. NRX, %) recorded by veterinarians were analyzed: anestrus (37.4 v. 41.2), metritis (40.1 v. 28.6), ketosis (11.9 v. 7.1), lameness (7.1 v. 3.1) and retained placenta (6.2 v. 4.0). The incidence of abortions was also analyzed; HO had a mean frequency of 9.9% and NRX 8.2%. These traits were defined as binary traits, with ‘1’ indicating that the disorder was present and a treatment took place at least once, or ‘0’ if the cow did not show signs of that disorder. Days open (i.e. the number of days from calving to conception), body condition score (BCS) recorded on a 1 to 5 scale and changes in BCS from calving to peak lactation were also analyzed. A logistic model was used for the health traits, while days open and BCS were analyzed with linear models. The model included breed group, herd-year of calving, birth year and parity as fixed effects. There was a significantly higher risk (odds ratio for HO v. NRX in parentheses) of ketosis (1.46), metritis (1.78), lameness (2.07), retained placenta (1.41) and abortion (1.13) in HO compared with NRX. Israeli Holstein heifers and cows in parity 3 to 6 had fewer cases of anestrus than NRX but no differences were found between the groups in parities 1 and 2. Body condition score was higher for NRX than HO and there was less change in BCS from calving to peak lactation in NRX compared with HO. Likewise, NRX had fewer days open than HO. Results indicate that crossbreeding can produce cows with better fertility that are less susceptible to postpartum disorders.     

A simple method for genomic selection of moderately sized dairy cattle populations

An efficient algorithm for genomic selection of moderately sized populations based on single nucleotide polymorphism chip technology is described. A total of 995 Israeli Holstein bulls with genetic evaluations based on daughter records were genotyped for either the BovineSNP50 BeadChip or the BovineSNP50 v2 BeadChip. Milk, fat, protein, somatic cell score, female fertility, milk production persistency and herd-life were analyzed. The 400 markers with the greatest effects on each trait were first selected based on individual analysis of each marker with the genetic evaluations of the bulls as the dependent variable. The effects of all 400 markers were estimated jointly using a 'cow model,' estimated from the data truncated to exclude lactations with freshening dates after September 2006. Genotype probabilities for each locus were computed for all animals with missing genotypes. In Method I, genetic evaluations were computed by analysis of the truncated data set with the sum of the marker effects subtracted from each record. Genomic estimated breeding values for the young bulls with genotypes, but without daughter records, were then computed as their parent averages combined with the sum of each animal's marker effects. Method II genomic breeding values were computed based on regressions of estimated breeding values of bulls with daughter record on their parent averages, sum of marker effects and birth year. Method II correlations of the current breeding values of young bulls without daughter records in the truncated data set were higher than the correlations of the current breeding values with the parent averages for fat and protein production, persistency and herd-life. Bias of evaluations, estimated as a difference between the mean of current breeding values of the young bulls and their genomic evaluations, was reduced for milk production traits, persistency and herd-life. Bias for milk production traits was slightly negative, as opposed to the positive bias of parent averages. Correlations of Method II with the means of daughter records adjusted for fixed effects were higher than parent averages for fat, protein, fertility, persistency and herd-life. Reducing the number of markers included in the analysis from 400 to 300 did not reduce correlations of genomic breeding values for protein with current breeding values, but did slightly reduce correlations with means of daughter records. Method II has the advantages as compared with the method of VanRaden in that genotypes of cows can be readily incorporated into the Method II analysis, and it is more effective for moderately sized populations.     

Screening for high fertility in high-producing dairy cows

A retrospective study involving 2756 pregnancies from two commercial dairy herds in northeastern Spain determined relationships between management, production and reproductive data, and high fertility (conception before 90 days in milk) in high-producing dairy cows. High fertility was registered in 989 (35.9%) cows. The following data were recorded for each animal: herd, repeated animal (cows included two or more times within the study in which data were obtained from different lactational periods), parity (primiparous versus multiparous), previous twinning, reproductive disorders following calving (retained placenta, primary metritis) and at postpartum gynecological examination (incomplete uterine involution, pyometra and ovarian cysts), days in milk at conception, previous estrous synchronization and season of calving and conception. In order to evaluate the possible effect of high production during the peak milk yield on subsequent fertility, daily milk production at Day 50 postpartum was also recorded and cows were classified as high (> or = 50 kg) and low (< 50 kg) producers. Logistic regression analysis indicated no significant effects of herd, repeated animal, previous twinning, reproductive disorders such as primary metritis, incomplete uterine involution, pyometra and ovarian cysts, previous estrous synchronization and season of calving and insemination. Based on the odds ratio, the likelihood of high fertility increased in high-producer cows by a factor of 6.8. High fertility was less likely for multiparous cows (by a factor of 0.35) and for cows suffering placenta retention (by a factor of 0.65). High fertile cows produced a mean of 49.5 kg milk at Day 50 postpartum, in contrast to that 43.2 kg milk of the remainder cows. These findings question the negative effect of high production on fertility. Our results indicated that high individual cow milk production can be positively related to high fertility.     

Milk protein composition in purebred Holsteins and in first/second-generation crossbred cows from Swedish Red,Montbeliarde and Brown Swiss bulls

The aim of this study was to analyze milk protein composition in purebred and crossbred dairy cattle and estimate the effects of individual sources of variation on the investigated traits. Milk samples were collected from 505 cows from three commercial farms located in Northern Italy, some of which had originated from crossbreeding programs, although most were purebred Holsteins (HO). The basic crossbreeding scheme was a three-breed rotational system using Swedish Red (SR) semen on HO cows (SR×HO), Montbeliarde (MO) semen on SR×HO cows (MO×(SR×HO)) and HO semen again on MO×(SR×HO) cows. A smaller number of purebred HO from each of the herds were mated inverting the breed order (MO×HO and SR×(MO×HO)) or using Brown Swiss (BS) bulls (BS×HO) then MO bulls (MO×(BS×HO)). Milk samples were analyzed by reverse-phase HPLC to obtain protein fraction amounts (g/l) and proportions (% of total true protein). Traits were analyzed using a linear model, which included the fixed effects of herd-test-day (HTD), parity, days in milk and breed combination. Results showed that milk protein fractions were influenced by HTD, stage of lactation, parity and breed combination. The increase in protein concentration during lactation was due in particular to β-casein (β-CN), α_S1-CN and β-lactoglobulin (β-LG). The higher protein content of primiparous milk was mainly due to higher concentrations of all casein fractions. The milk from crossbred cows had higher contents and proportions of κ-CN and α-lactalbumin (α-LA), lower proportions of β-LG and greater proportion of caseins/smaller in whey proteins on milk true protein than purebred HO. The three-way crossbreds differed from two-way crossbreds only in having greater proportions of α-LA in their milk. Of the three-way crossbreds, the SR sired cows yielded milk with a smaller content and proportion of β-LG than the MO sired cows, and, consequently, a higher proportion of caseins than whey proteins. Results from this study support the feasibility of using crossbreeding programs to alter milk protein profiles with the aim of improving milk quality and cheese-making properties.     

The effect of sire predicted transmitting ability for production traits on fertility,survivability, and health of Holstein dairy cows

The major objective of this study was to evaluate, using survival analysis and multivariable regression models, the relationship of sire predicted transmitting ability (PTA) for production traits with their daughters' milk production, fat, and protein percentage (PROPCT), reproductive performance, postpartum disease incidence, and survivability. Data were collected from six large commercial dairy farms, and data analysis included 22,205 cows. Information regarding each sire's genetic evaluation included the following: PTA for fat yield (FAT), fat percentage (FATPCT), milk yield (MILK), protein yield, and PROPCT. Sire PTA was categorized into quartiles to facilitate data analysis and interpretation. Retained placenta, metritis, displaced abomasum, and clinical mastitis were diagnosed and treated by farm personnel. The overall average daily milk production, milk fat and PROPCT during the first 10 months of lactation was higher for the cows in the highest quartile of sire PTA, and cows in the lowest quartile had lower averages. There was no significant association between sire PTA for production traits and first test day fat to protein ratio or the incidence of postpartum disease. Sire PTA for MILK, FATPCT, and PROPCT were significantly associated with the hazard of pregnancy. The median days from calving to conception were 159, 155, 170, and 181 days for cows in the sire PTA for MILK quartiles 1, 2, 3, and 4, respectively. Sire PTA for PROPCT and FATPCT were also significantly associated with the hazard of pregnancy. The median days from calving to conception were 175, 189, 152, and 145 for cows in the sire PTA for PROPCT groups 1, 2, 3, and 4, respectively. Additionally, cows in the highest quartile for sire PTA for FATPCT had the lowest median days from calving to conception (144 days) and cows in lowest quartile had the highest median interval (177 days). Sire PTA for FAT was the only sire PTA significantly associated with the hazard of death/culling. When compared with the cows in the highest sire PTA for FAT quartile cows in the first, second, and third quartiles were at 1.51, 1.30, and 1.13 times higher hazard of death/culling, respectively. In conclusion, this study shows that high sire PTA for MILK and low sire PTA for milk fat and PROPCT are associated with decreased daughters' reproductive performance. Sire PTA for production traits were not found to be associated with postpartum disease incidence.     

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.     

Body condition score and live-weight effects on milk production in Irish Holstein-Friesian dairy cows

The objective of the present study was to quantify the relationships among body condition score (BCS; scale 1 to 5), live weight (WT) and milk production in Irish Holstein-Friesian spring calving dairy cows. Data were from 66 commercial dairy herds during the years 1999 and 2000. The data consisted of up to 9886 lactations with records for BCS or WT at least once pre-calving, or at calving, nadir or 60 days post-calving. Change in BCS and WT was also calculated between time periods. Mixed models with cow included as a random effect were used to quantify the effect of BCS and WT, as well as change in each trait, on milk yield, milk fat concentration and milk protein concentration. Significant and sometimes curvilinear associations were observed among BCS at calving or nadir and milk production. Total 305-day milk yield was greatest in cows calving at a BCS of 4.25 units. However, cows calving at a BCS of 3.50 units produced only 68 kg less milk than cows calving at a BCS of 4.25 units while cows calving at 3.25 or 3.00 BCS units produced a further 50 and 114 kg less, respectively. Cows that lost more condition in early lactation produced more milk of greater fat and protein concentration, although the trend reversed in cows that lost large amounts of condition post-calving. Milk yield increased with WT although the marginal effect decreased as cows got heavier. Milk fat and protein concentration in early lactation also increased with WT pre-calving, calving and nadir, although WT did not significantly affect average lactation milk fat concentration.     

Danish Holsteins Favor Bull Offspring: Biased Milk Production as a Function of Fetal Sex,and Calving Difficulty

In a previous study from 2014 it was found that US Holstein cows that gave birth to heifer calves produced more milk than cows having bull calves. We wanted to assess whether this is also true for Danish cattle. Data from 578 Danish Holstein herds were analysed with a mixed effect model and contrary to the findings in the US, we found that cows produced higher volumes of milk if they had a bull calf compared to a heifer calf. We found a significantly higher milk production of 0.28% in the first lactation period for cows giving birth to a bull calf, compared to a heifer calf. This difference was even higher when cows gave birth to another bull calf, so having two bull calves resulted in a difference of 0.52% in milk production compared to any other combination of sex of the offspring. Furthermore, we found that farmer assisted calvings were associated with a higher milk yield. Cows with no farmer assistance or with veterinary assistance during the most recent calving produced less milk. There were also indications that dams would favor a bull fetus by decreasing milk production during the second pregnancy if the calf born in the first parity was a heifer. We hypothesize that size of calves is a confounding factor for milk production. However, calving weight was not available in the present data set to test this hypothesis.     

Genetic merit for milk production and reproductive success in dairy cows

The effect of genetic merit for milk production traits - fat, protein and milk yield - in dairy cows on milk production, body condition, blood metabolites, reproductive hormones, feed intake and reproductive performance was studied over a period of 2 years. Cows were grouped into two categories, based on calculated pedigree indices using multiple-trait across country evaluation (MACE). Cows of high genetic merit (HGM, n = 48 in year 1 and n = 46 in year 2) had a mean predicted difference +/- standard deviation for milk production of 475 +/- 76kg. The cows of medium genetic merit (MGM, n = 48 in both years) had a mean predicted difference for milk production of 140 +/- 68kg.The cows calved between January and April, and were offered grass silage ad libitum plus 9kg concentrates per cow per day, irrespective genetic merit, from calving to turnout in March, when they were subjected to one of three grazing systems. Cows were available for rebreeding from late April until late July of each year.High genetic merit cows had higher milk production, incurred greater body condition loss between calving and first service and had lower plasma glucose and insulin-like growth factor-1 (IGF-1) concentrations than medium genetic merit cows. Furthermore, HGM cows had lower first and second service and overall conception rates, and required more services per conception than the MGM cows.Cows that did not conceive to first service were retrospectively compared to those that conceived to first service within each genetic merit group. There were no significant differences between the HGM cows that did not conceive to first service and those that conceived to this service in terms of milk production, body condition score change between calving and first service, feed intake at first service, or in plasma concentrations of glucose, non-esterified fatty acids (NEFA) or IGF-1. Medium genetic merit cows that did not conceive to first service lost more body condition between calving and first service than did those that conceived to this service.In the present study, HGM cows had higher milk production and reduced reproductive performance in comparison with MGM cows. However, reproductive performance was not associated with milk production, feed intake or plasma concentrations of glucose, NEFA or IGF-1 between calving and first service, since there were no significant differences in these variates between high or medium genetic merit cows that did not conceive to first service and those that conceived to this service. Therefore, these variates are unlikely to be useful predictors of reproductive performance, under the conditions of the present study.     

Effect of different feeding strategies on lactation performance of Holstein and Normande dairy cows

The dairy farming systems of Western Europe are based on a simple feeding system composed of grazed and preserved grass, maize silage and concentrates in variable proportions. There is, nevertheless, a great diversity of feeding strategies between dairy farms. Over 5 years, we studied the direct and delayed effects of four feeding strategies on the lactation and reproduction performances of Holstein and Normande dairy cows. The four feeding strategies (denoted Hh, Hl, Lh and Ll) correspond to two total mixed rations applied in winter from calving to turnout (maize silage with 30% concentrate or grass silage with 15% concentrate), which were subsequently crossed with two levels of concentrate supplementation at grazing to 210 days. Each year, 72 dairy cows managed in grouped winter calving were assigned to the four strategies. Finally, the results of 325 lactations and 295 inseminated cows were analysed. The four strategies resulted in considerable variation in nutrient intake and, in particular, in differences in concentrates consumed, with values of 1407, 1026, 773 and 392 kg dry matter per cow for strategies Hh, Lh, Hl and Ll, respectively. Total milk production (7567, 7015, 6720 and 6238 kg per cow for treatments Hh, Lh, Hl and Ll, respectively), milk fat content (39.0, 37.1, 40.3 and 38.5 g/kg, respectively), milk protein content (33.0, 31.8, 33.1 and 31.6 g/kg, respectively), and the character of the lactation and body condition curves were all highly sensitive to the strategies applied. While no significant interaction was detected on total lactation yield, the Holstein cows reacted more dramatically to each dietary change at each period, compared with the Normande cows. Winter feeding did not affect the production of milk at pasture whereas, at pasture, the milk from the cows of the H groups in winter was higher in milk fat and protein content. Reproduction performance was unaffected by feeding strategy. The Holstein cows, well fed and producing the most milk (Hh and Hb), had the lowest rate of success at first artificial inseminations (21.5%). The dual-purpose Normande cows had a pregnancy rate 10 points higher than Holstein cows. This comparison of strongly contrasting feeding strategies confirms the immediate reactivity of dairy cows (in terms of milk performance and body condition) to variations of nutritive intake throughout lactation, with a weak carryover effect from feeding levels early in lactation. In contrast, reproduction performance was less sensitive to variation in nutrient supply.     

Short- and long-term effects of high milking frequency during the first 21 days of lactation on production and reproductive performance in high-lactating cows

We examined short- and long-term effects of high milking frequency (HMF) for the first 21 days of lactation. The study included 122 Israeli Holstein cows – 32 pregnant heifers, 40 cows in second lactation and 50 cows in >second lactation. Heifers were paired according to predicted transmitting ability and cows according to energy-corrected milk (ECM) production, age, days in milk and expected calving date. Thin cows (body condition score <2.75) were not included. One cow from each pair was arbitrarily allocated to a control group milked three times daily (3× milking cows) and the counterpart to an experimental group milked six times daily for the first 21 days of lactation and then three times daily for the rest of the lactation (6× milking cows). During the first 21 days of lactation, 6× milking cows produced 9.3 kg more milk (26.5%) and 7.16 kg more ECM (19%) than the 3× milking cows. The higher milk production persisted throughout the entire lactation (305 days), as reflected by treatment×age interaction showing higher milk production for the first and second (7%) but not >second lactation cows relative to their control counterparts (−0.37%); ECM production was also higher in 6× milking first and second lactation (7.6% and 5%, respectively) but not for >second lactation cows. Furthermore, HMF had long-lasting effects, expressed as significantly higher milk production through the succeeding lactation in the previous first lactation cows (10%); a tendency toward significance in the second lactation cows relative to the controls (4.7%), but a deleterious effect on the >second lactation cows, reflected by lower milk production (−5.25%) than in controls; similar patterns were found for the ECM. For the entire 305 days of lactation, fat and protein yields were higher for first and second lactation cows, whereas protein yield for >second lactation cows was lower in the 6× milking v. control group. Given that HMF during the first 21 days of first or second lactation increases milk and ECM yields throughout the concurrent and successive lactation with no adverse effect on energy balance, mastitis, metabolic diseases or reproduction, it seems to be economically beneficial. However, caution should be paid for >second lactation cows due to absence of significant effect in the entire of the first HMF applied lactation and the deleterious effect in the succeeding lactation.     

Effect of offering rumen-protected fat supplements on fertility and performance in spring-calving Holstein-Friesian cows

The objective of this study was to evaluate the effect of two different rumen-protected fat supplements, on reproductive performance and milk production, in grass-based spring calving cows. Two hundred and one Holstein-Friesian cows with an average lactation number of 3.6 (20% first lactation, 16% second lactation and 64% third lactation or greater) were grouped into blocks of three on the basis of calving date, lactation number and previous lactation milk yield for cows of second lactation or greater and on the basis of calving date for first lactation animals. From within-blocks individual animals were assigned at random, within 10 days post-calving, to one of the following three treatments: (1) Megalac Plus 3% (MP; 0.4kg/day, containing Ca salt of palm fatty acids and Ca salt of methionine hydroxy analogue), (2) Megapro Gold (MPG; 1.5kg/day, containing Ca salt of palm fatty acids, extracted rapeseed meal and whey permeate), and (3) Control (C; unsupplemented). Cows were supplemented for on average 103 days (range 54-134 days). The average milk yield over the first 12 weeks of lactation was higher (P<0.05) for both fat supplements compared to C and was higher for MP compared to C over the full lactation. Both supplements reduced (P<0.05) milk protein concentration over the first 6 weeks of lactation. MPG increased (P<0.05) conception rate to first service compared to C. Conception rate to first service was similar (P=0.14) on MP compared to C. For pregnancy to second service, C had a higher (P<0.05) conception rate than MP. There were no significant differences between treatments in overall pregnancy rate, services per conception, number of cows served in the first 3 weeks of the breeding season or the 6-weeks in-calf rate. Comparing the combined fat treatments to C resulted in a higher (P<0.05) conception rate to first service for the fat treatments but no significant difference in overall pregnancy rate. In conclusion, fat supplements increased conception rate to first service but did not significantly affect the proportion of cows pregnant at the end of the breeding season.     

Suitability of cross-bred cows for organic farms based on cross-breeding effects on production and functional traits

Data from 113 Dutch organic farms were analysed to determine the effect of cross-breeding on production and functional traits. In total, data on 33 788 lactations between January 2003 and February 2009 from 15 015 cows were available. Holstein–Friesian pure-bred cows produced most kg of milk in 305 days, but with the lowest percentages of fat and protein of all pure-bred cows in the data set. Cross-breeding Holstein dairy cows with other breeds (Brown Swiss, Dutch Friesian, Groningen White Headed, Jersey, Meuse Rhine Yssel, Montbéliarde or Fleckvieh) decreased milk production, but improved fertility and udder health in most cross-bred animals. In most breeds, heterosis had a significant effect (P < 0.05) on milk (kg in 305 days), fat and protein-corrected milk production (kg in 305 days) and calving interval (CI) in the favourable direction (i.e. more milk, shorter CI), but unfavourably for somatic cell count (higher cell count). Recombination was unfavourable for the milk production traits, but favourable for the functional traits (fertility and udder health). Farm characteristics, like soil type or housing system, affected the regression coefficients on breed components significantly. The effect of the Holstein breed on milk yield was twice as large in cubicle housing as in other housing systems. Jerseys had a negative effect on fertility only on farms on sandy soils. Hence, breed effects differ across farming systems in the organic farming and farmers can use such information to dovetail their farming system with the type of cow they use.     

Effect of butaphosphan and cyanocobalamin on postpartum metabolism and milk production in dairy cows

The aim of this study was to determine the effect of butaphosphan and cyanocobalamin (BTPC) supplementation on plasma metabolites and milk production in postpartum dairy cows. A total of fifty-two Holstein cows were randomly assigned to receive either: (1) 10 ml of saline (NaCl 0.9%, control group); (2) 1000 mg of butaphosphan and 0.5 mg of cyanocobalamin (BTPC1 group); and (3) 2000 mg of butaphosphan and 1.0 mg of cyanocobalamin (BTPC2 group). All cows received injections every 5 days from calving to 20 days in milk (DIM). Blood samples were collected every 15 days from calving until 75 DIM to determine serum concentration of glucose, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), cholesterol, urea, calcium (Ca), phosphorus (P), magnesium (Mg), aminotransferase aspartate (AST) and γ-glutamyltransferase (GGT). The body condition score (BCS) and milk production were evaluated from calving until 90 DIM. Increasing doses of BTPC caused a linear reduction in plasma concentrations of NEFA and cholesterol. Supplementation of BTPC also reduced concentrations of BHB but it did not differ between the two treatment doses. Milk yield and milk protein had a linear increase with increasing doses of BTPC. A quadratic effect was detected for milk fat and total milk solids according to treatment dose, and BTPC1 had the lowest mean values. Concentrations of glucose, urea, P, Mg, AST, GGT, milk lactose and BCS were not affected by treatment. These results indicate that injections of BTPC during the early postpartum period can reduce NEFA and BHB concentrations and increase milk production in Holstein cows.     

Effects of a ruminally protected B-vitamin supplement on milk yield and composition of lactating dairy cows

It is not clear if B vitamins supplied to the small intestine of dairy cows from dietary and rumen microbial sources are provided in sufficient quantity to maximize animal performance. Our objective was to determine effects of adding a ruminally protected B vitamin blend supplement, containing biotin, folic acid, pantothenic acid and pyridoxine, to the diet of high producing dairy cows on their productivity. Two dairy facilities located in California (USA) were used, one with mid lactation Holstein cows (Experiment 1) and the other with early lactation Holstein cows (Experiment 2). In each Experiment, cows were randomly assigned to treatment in a 2 × 2 crossover design with 28 d (Experiment 1) or 35 d (Experiment 2) experimental periods. In Experiment 1, milk and milk fat yield were unaffected by treatment, although milk fat proportion was lower (37.1 versus 36.3 g/kg; P<0.01), but milk protein yield was higher (1.21 versus 1.24 kg/d; P=0.02) in cows fed B vitamins. In Experiment 2, milk (39.60 versus 40.46 kg/d; P=0.02), milk fat (1.40 versus 1.47 kg/d; P<0.01) and milk protein yield (1.10 versus 1.16 kg/d; P<0.01), as well as milk energy output (113.2 versus 117.8 MJ/d; P<0.01) were all higher with B vitamin feeding. Body condition score (BCS) increased more with B vitamin feeding in Experiment 2, but was unaffected in Experiment 1. Body locomotion score (BLS) increased with B vitamin feeding in both experiments (P=0.01 and < 0.01, respectively), possibly an indication of reduced locomotory ability. Overall, productivity of high producing lactating dairy cows responded positively to feeding a mixture of ruminally protected B vitamins, although differences in the extent of the positive responses between experiments perhaps suggests that early lactation cows, with lower DM intake to milk yield ratios, may be more responsive to ruminally protected B vitamins than mid lactation cows, with higher DM intake to milk yield ratios.     

Once-a-day milking of Holstein and Montbéliarde cows for 7 weeks in mid-lactation

This study aimed at comparing the effects of once-a-day (OAD) milking during the descending phase of lactation between cows from the two most common breeds in France (Holstein and Montbéliarde). This study was carried on during two successive summers on a total of 50 Holstein and 38 Montbéliarde cows. During 7 weeks, half of the cows from each breed was milked OAD while the other half was milked twice a day (TAD). The animals were also followed for the next 3 or 5 weeks when they were all milked TAD, to check for any residual effect of OAD milking. The behaviour of OAD cows was observed around milking time. The incidence of diseases, the main performance variables (milk production, milk flow rate, live weight and body condition score), the detailed composition of milk (fat, protein, lactose, somatic cells, minerals, pH, free fatty acid (FFA), nitrogen fractions and enzymes) and some technological variables (clotting time and curd firmness) were measured on all cows.Some signs of disturbance were observed in the OAD cows at the time when milking was omitted: some cows mooed, some went close to the exit of the paddock, some leaked milk prior to milking. However, these signs disappeared after 2 days. After the experimental period, the live weight and the body condition score of TAD and OAD cows did not differ significantly. OAD cows produced 4.5 kg/day less than TAD (P < 0.001), this being more marked in Holstein (5.7 kg/day, P < 0.001) than Montbéliarde (3.3 kg/day, P < 0.001) cows. The milk contents of fat, whey protein, casein, total protein and phosphorus, and its plasminogen activity, were higher with OAD cows while lactose and FFA contents, and lipoprotein lipase activity were lower, with no interaction observed with breed. During the subsequent 3 weeks, when all cows were again milked TAD, OAD cows still produced 1.7 kg/day less milk (P < 0.01) with slightly higher fat and protein content.OAD milking for 7 weeks during the descending phase of lactation decreased milk production but increased milk content of most components, with a low residual effect. Montbéliarde cows were less affected by OAD milking than Holstein cows.     

Induction of twinning in Holstein and Japanese black cows by ipsilateral frozen embryo transfer

Induction of twinning by ipsilateral nonsurgical transfer of two frozen-thawed Japanese Black bovine embryos to each of 20 Holstein and 26 Japanese Black cows, that had been kept under a stable in private farm conditions, was examined. The cows were monitored every 20 days from Day 25 to Day 65 of gestation for pregnancy and fetus survival (estrus is Day 0). Seventy-five per cent (15 of 20), 65.0% (13 of 20) or 60.0% (12 of 20) and 61.5% (16 of 26), 53.8% (14 of 26) or 50.0% (13 of 26) of Japanese Black cows were diagnosed pregnant at 25, 45 and 65 days after transfer by ultrasonic echography. Embryonic losses were observed between Days 25 and 65 in 29.2% (7) Holstein and 31.8% (7) Japanese Black cows. The twin pregnancy rate in Holstein and Japanese Black cows decreased with time; 60.0% (9 of 15) vs. 37.5% (6 of 16) at Day 25; 53.8% (7 of 13) vs. 28.6% (4 of 14) at Day 45 and 41.7% (5 of 12) vs. 15.4% (2 of 13) at Day 65. At calving, Holstein cows produced five sets of twins and seven single calves, and Japanese Black cows two sets of twins and 11 single calves. The twinning rate in Holstein cows was higher (P < 0.05) than that in Japanese Black cows, 41.7% (5 of 12) vs. 15.4% (2 of 13). The calf birth weight in Holsteins was heavier (P < 0.05) than that in Japanese Black dams (24.5 kg, 33.6 kg vs. 19.3 kg, 25.5 kg for twin and single calves). The placental weight in Holstein dams calving twins was heavier than that in Holstein dams calving a single calf or in Japanese Black dams calving either twins or a single calf (6.6 kg vs. 3.5 kg, 4.6 kg or 2.8 kg). The number of placentome in Holstein dams calving twins was also higher (P < 0.05) than that in Holstein dams calving a single calf or Japanese Black dams (103.5 vs. 41.8, 67.9, 33.0). The number of placentome was approximately double in dams calving twins than that of dams calving a single calf.     

Relationship between serum nonesterified fatty acids at calving and the incidence of periparturient diseases in Holstein dairy cows

The objective was to describe the relationship between concentration of serum nonesterified fatty acids (NEFAs) at calving and the incidence of periparturient disorders in Chilean Holstein dairy cows (Bos taurus). The study was conducted at two dairies (central Chile) with 700 milking cows each and similar management. Between July 2006 and March 2007, 350 cows were selected, and concentrations of serum NEFAs were determined at calving. The incidence of milk fever (MF), retained fetal membranes (RFMs), metritis, and clinical mastitis from calving to 100 d in lactation were consistently recorded. The relationship between concentration of serum NEFAs at calving and the incidence of periparturient diseases was determined using logistic regression. The main explanatory variable was concentration of serum NEFAs at calving. The incidence of MF, RFM, metritis, and mastitis was 5.4%, 15.6%, 10.8%, and 14.4%, respectively. There was no association between concentration of NEFAs at calving and the incidence of these conditions when the median value of NEFAs (0.9 mEq/L) was used as a cutoff. However, when the 75th percentile (1.2 mEq/L) was used as the cutoff, cows with values <1.2 mEq/L were 0.45 and 0.32 times as likely to develop clinical mastitis and MF, respectively, compared with cows with values ≥1.2 mEq/L. When the 90th percentile (1.6 mEq/L) was used as a cutoff, cows with values <1.6 mEq/L were 0.25 times as likely to develop clinical mastitis compared with cows with values ≥1.6 mEq/L. As a continuous variable, for every 0.1 mEq/L increment in NEFAs at calving, cows were 1.11 times more likely to experience clinical mastitis. In conclusion, cows with NEFA concentrations ≥1.2 mEq/L had a higher incidence of clinical mastitis and MF than that of cows with values <1.2 mEq/L.     

Genetics of heat tolerance for milk yield and quality in Holsteins

Tropical and sub-tropical climates are characterized by high temperature and humidity, during at least part of the year. Consequently, heat stress is common in Holstein cattle and productive and reproductive losses are frequent. Our objectives were as follows: (1) to quantify losses in production and quality of milk due to heat stress; (2) to estimate genetic correlations within and between milk yield (MY) and milk quality traits; and (3) to evaluate the trends of genetic components of tolerance to heat stress in multiple lactations of Brazilian Holstein cows. Thus, nine analyses using two-trait random regression animal models were carried out to estimate variance components and genetic parameters over temperature–humidity index (THI) values for MY and milk quality traits (three lactations: MY×fat percentage (F%), MY×protein percentage (P%) and MY×somatic cell score (SCS)) of Brazilian Holstein cattle. It was demonstrated that the effects of heat stress can be harmful for traits related to milk production and milk quality of Holstein cattle even though most herds were maintained in a modified environment, for example, with fans and sprinklers. For MY, the effect of heat stress was more detrimental in advanced lactations (−0.22 to −0.52 kg/day per increase of 1 THI unit). In general, the mean heritability estimates were higher for lower THI values and longer days in milk for all traits. In contrast, the heritability estimates for SCS increased with increasing THI values in the second and third lactation. For each trait studied, lower genetic correlations (different from unity) were observed between opposite extremes of THI (THI 47 v. THI 80) and in advanced lactations. The genetic correlations between MY and milk quality trait varied across the THI scale and lactations. The genotype×environment interaction due to heat stress was more important for MY and SCS, particularly in advanced lactations, and can affect the genetic relationship between MY and milk quality traits. Selection for higher MY, F% or P% may result in a poor response of the animals to heat stress, as a genetic antagonism was observed between the general production level and specific ability to respond to heat stress for these traits. Genetic trends confirm the adverse responses in the genetic components of heat stress over the years for milk production and quality. Consequently, the selection of Holstein cattle raised in modified environments in both tropical and sub-tropical regions should take into consideration the genetic variation in heat stress.     

Performance and financial consequences of stillbirth in Holstein dairy cattle

Stillbirth is an economically important trait on dairy farms. Knowledge of the consequences of, and the economic losses associated with stillbirth can help the producer when making management decisions. The objectives of this study were to determine the effects of stillbirth on productive and reproductive performance as well as financial losses due to stillbirth incidence in Iranian Holstein dairy farms. Economic and performance data were collected from nine Holstein dairy farms in Isfahan and Khorasan provinces of Iran from March 2008 to December 2013. The final data set included 160 410 calving records from 53 265 cows. A linear mixed model was developed to evaluate the effects of stillbirth on performance of primiparous and multiparous cows separately and overall. An economic model was used to estimate the economic losses due to stillbirth. The incidence of stillbirth cases per cow per year was 4.2% on average (3.4% to 6.8% at herd level). The least square means results showed that a case of stillbirth significantly (P<0.05) reduced 305-day milk production in multiparous cows and overall, but had no significant effects on primiparous cows production performance (P>0.05). Overall, a case of stillbirth reduced 305-day milk yield by 544.0±76.5 kg/cow per lactation. Stillbirth had no significant effects on 305-day fat and protein percentages in either primiparous or multiparous cows. Overall, cows that gave birth to stillborn calves had significantly increased days open by 14.6±2.6 days and the number of inseminations per conception by 0.2 compared with cows that gave birth to live calves (P<0.01). In general, the negative productive and reproductive effects associated with stillbirth were smaller and non-significant for primiparous cows compared with multiparous cows. The financial losses associated with stillbirth incidence averaged US$ 938 per case (range from $US 767 to $US 1189 in the nine investigated farms). The loss of a calf was not the only cost associated with stillbirth, as it accounted for 71.0% of the total cost. The costs of dystocia (7.6%) and culling and replacement expenses (6.3%) were the next most important costs associated with stillbirth. These results can be used to assess the potential return from management strategies to reduce the occurrence of stillbirths.