Israeli Dairy Herds Research Articles

Effectiveness of the strain 919 bovine ephemeral fever virus vaccine in the face of a real-world outbreak: A field study in Israeli dairy herds

Bovine ephemeral fever virus (BEFV) is a globally spread arthropod-borne RNA virus that has significant economic impacts on the cattle industry. A live attenuated commercial BEF vaccine, based on the Australian BEFV strain 919, is widely used in Israel and other countries. A previous study has suggested the high effectiveness of this vaccine (ULTRAVAC BEF VACCINE™ from Zoetis®), but anecdotal reports of high BEF morbidity among vaccinated dairy herds in Israel casted doubt on these findings. To resolve this uncertainty, a randomized controlled field vaccine effectiveness study was conducted in Israel during a BEF outbreak which occurred in 2021. Eleven dairy herds were enrolled and monitored for BEF-associated morbidity and rumination alteration patterns using electronic monitoring tags (HR Tags, SCR® Dairy, Netanya, Israel). Four of the herds were naturally infected with BEFV during the outbreak, resulting in a total of 120 vaccinated and 311 unvaccinated subjects that were included in the effectiveness study. A mixed-effect Cox proportional hazard regression model was used to calculate the overall hazard ratio between vaccinated and unvaccinated cattle. This analysis demonstrated an average vaccine effectiveness of 60 % (95 % CI = 38 %–77 %) for preventing clinical disease. In addition, a non-statistically significant trend (p = 0.1) towards protection from mortality was observed, with no observation of mortality among the vaccinated groups compared to 2.61 % mortality (7/311) among the unvaccinated subjects. One hundred and thirty vaccinated and unvaccinated calves from affected and non-affected herds and with different status of morbidity were sampled and analysed by serum-neutralization test. The highest titers of BEFV-neutralizing antibodies were found in subjects that were both vaccinated and clinically affected, indicating a booster effect after vaccination. The results of the study provide evidence for the moderate effectiveness of the ULTRAVAC BEF VACCINE™ for the prevention of BEF.

Recovery Rates of Treated vs. Non-Treated Dairy Cows with Subclinical Mastitis

The term “spontaneous recovery” refers to a return to a previous condition without any external treatment. In cow mastitis, it refers to cases exhibiting visual symptoms (clinical) or an increase in somatic cell count (SCC) with no visual symptoms (subclinical), with or without identification of a pathogen, from which the animal recovers. A large retrospective analysis of data compiled from the Israeli Dairy Herd Book was performed to evaluate the occurrence of: (i) actual “spontaneous recovery” from the inflammation; (ii) recovery from the inflammation due to antibiotic treatment. In 2018, 123,958 cows from 650 herds with first elevation of SCC at monthly test-day milk yield were clustered into five SCC-cutoff levels (CL) (×103 cells/mL): CL1 (200–299), CL2 (300–399), CL3 (400–499), CL4 (500–999), CL5 (≥1000). Each cutoff level was analyzed separately, and each cow appeared only once in the same lactation and cutoff level, thus resulting in five independent analyses. Recovery was defined as decreased SCC on all three monthly test days, or on the second and third test days, set to: R1 (<100 × 103 cells/mL); R2 (<250 × 103 cells/mL). No difference was found among cutoff levels when the recovery was set to R1, with only 10–12% of the cows presenting spontaneous recovery. When the recovery was set to R2, percent spontaneous recovery was 25–27% at the three higher cutoff levels (CL3–CL5) and 35–41% at the lowest levels (CL1, CL2). Antibiotic treatment was administered to only ~10% of the cows, and in only the higher cutoff-level groups—CL4 and CL5. No difference was found between spontaneous recovery and recovery after antibiotic treatment. Moreover, percentage culled cows treated with antibiotics was significantly higher (p < 0.01) than that of non-treated culled cows (18 and 10.2, respectively), suggesting that the more severe mastitis cases were treated. We concluded that (i) actual spontaneous recovery from inflammation is low and does not depend on the number of cells in the milk at time of infection, and (ii) recovery from inflammation following antibiotic treatment is not higher.

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.

Carry-over of aflatoxin B1 to aflatoxin M1 in high yielding Israeli cows in mid- and late-lactation.

The potent hepatotoxin and carcinogen aflatoxin B1 (AFB1) is a common mycotoxin contaminant of grains used in animal feeds. Aflatoxin M1 (AFM1) is the major metabolite of AFB1 in mammals, being partially excreted into milk, and is a possible human carcinogen. The maximum permitted concentration of AFM1 in cows’ milk is 0.05 μg/kg in Israel and the European Union. Since milk yield and the carry-over of AFB1 in the feed to AFM1 in the milk are highly correlated, it was considered important to determine the AFM1 carry-over in Israeli-Holstein dairy cows, distinguished by world record high milk production. Twelve such cows were used to determine AFM1 carry-over following daily oral administration of feed containing ~86 μg AFB1 for 7 days. The mean carry-over rate at steady-state (Days 3–7) was 5.8% and 2.5% in mid-lactation and late-lactation groups, respectively. The carry-over appears to increase exponentially with milk yield and could be described by the equation: carry-over% = 0.5154 e0.0521 × milk yield, with r2 = 0.6224. If these data truly reflect the carry-over in the national Israeli dairy herd, the maximum level of AFB1 in feed should not exceed 1.4 μg/kg, a value 3.6 times lower than the maximum residue level currently applied in Israel.

Factors Affecting Fertility of Dairy Cows in Israel

The objectives of this review are to describe the reproductive parameters monitored in Israeli dairy herds and to evaluate their changes in recent years. Eighty percent of the cows and 70% of the farms use the Israel Cattle Breeders' Association Herdbook and about 50% of them use pedometry systems. Intensive herd medicine is practiced in 80% of the herds by Hachaklait Veterinary Services Ltd. Herd-health reports monitor calving, production and reproduction. Causal analysis explains the effects and interactions of various risk factors involved. The average of 305 days of milk production per cow increased between 2004 and 2008 from 11,200 to 11,903 kg. At the same time the first A.I. conception rate (C.R) dropped from 43.0 to 40.7% and from 35.6 to 30.5% in primiparous cows (PC) and multiparous cows (MC), respectively. The waiting period (WP) was shortened from 106.2 to 93.4 days in PC and from 99.9 to 87.3 days in MC. The undetected heat rate per herd increased from 30.3 to 38.9% and from 33.9 to 43.9% in PC and MC, respectively. The average of days open per herd dropped from 127 to 118.4 and from 127.5 to 120.5 in PC and MC, respectively. The rate of cows open by 150 days in lactation dropped from 42% (+/- 10.2) to 34.2% (+/- 8.1) and 47.1% (+/- 8.8) to 39.5% (+/- 7.1) in PC and MC, respectively. The ratio between summer inseminations and winter inseminations increased from 0.81 to 1.04 from 2000 to 2008. The calving interval (CI) average fluctuated around 424.5 (+/- 2.0) days and 417.5 (+/- 1.7) days in PC and MC, respectively. The average duration of the dry period in 2008 was 60.7 (+/- 4.7, 47-72) days. From 2004 to 2008, the average herd rate of endometritis increased from 38.1 to 46.0% and from 25.5 to 30.1% in PC and MC, respectively. The milk fat to protein ratio in the first test day of lactation has remained steady during the past 5 years. Genetic trends in the breeding values of fertility and milk showed consistent improvement from 2000 to 2006. In recent years there has been a small decline in some reproductive parameters, while at the same time others have remained unchanged. The farmer's economical viewpoint and management practices have contributed to the changes.

Sample-based assessment of the microbial etiology of bovine necrotic vulvovaginitis

A semiquantitative evaluation of potential bacterial pathogens was correlated to the severity of lesions during an outbreak of bovine necrotic vulvovaginitis (BNVV) on an Israeli dairy herd. Bacteriologic examination of 287 vaginal swabs from 104 post-calving heifers showed a highly significant correlation between Porphyromonas levii colony forming unit numbers and the clinical scores of the lesions, when assessed by an ordinal regression statistical model. No such correlation was found for the other bacteria included in the study. Nineteen samples taken for virological examinations resulted negative for bovine herpes viruses 1, 2, 4 and 5. Thus the results of this study substantiate the essential role of P. levii in the etiology of BNVV and indicate that BHV4 is not required as a predisposing factor to the syndrome.

Association Between Live Body Weight and Milk Urea Concentration in Holstein Cows

Use of milk urea (MU) concentration as a parameter for detection of nutritional imbalances requires identification and quantification of nutritional and nonnutritional factors that influence it. The objective of this study was to assess the relationship between live body weight (BW) and MU concentration in Holstein cows. Results for the test-day measurements at 7 dairy farms were obtained from the Israeli Dairy Herd Improvement Center and concomitant cow weights were registered in local computerized weighing systems. A total of 1996 cows and 25,485 records were studied. The overall unadjusted per-cow mean MU nitrogen concentration and BW were 15.3mg/dL (SD=3.8) and 593kg (SD=84), respectively. The linear association between BW and MU was negative and highly significant and the quadratic component of BW had a highly significant positive association with MU. There was a significant interaction between the association of MU and BW with lactation number. Sampling month, milk yield, milk fat percentage, and somatic cell count accounted for significant variation in MU. Predicted MU concentrations at different BW values were calculated for each parity group, by setting equations that included the estimates of the variables associated with MU and constant values (lactation averages) for the independent variables, with the exception of BW. Plotting of results showed exponential characteristics for the relationship between BW and predicted MU concentrations. At any of the considered BW, predicted MU concentrations were lower for first-parity cows. The trends and interactions found in the present study may contribute to improving accuracy of models designed to calculate urinary nitrogen excretion rates and normative milk urea concentrations.

Relationships between milk urea and production, nutrition, and fertility traits in Israeli dairy herds.

The objectives of this study were to identify and evaluate production and environmental factors that influence milk urea (MU) in Israeli dairy herds, to analyze the relationships between MU concentration and nutritional variables, and to examine a possible association between MU and pregnancy rate (PR). Production and environmental data were obtained from the Israeli Dairy Herd Improvement (DHI) Center (n = 1,279,600). Programmed total mixed rations (feeds and quantities) on milk-test day were collected from 42 dairy herds. Data on 36,073 cows that were inseminated close to milk-test day and pregnancy diagnosis results were obtained from the DHI data bank. Highly significant positive relationships were found between MU concentration and milk yield and fat percentage; relationships between MU and milk total protein percentage and somatic cell count were negative. Milk urea levels were higher during the summer months and were higher for adult cows. These levels increased as lactation progressed. Milk urea was positively associated with dietary levels of crude protein, ruminal digestible protein, and neutral detergent fiber contents; it was negatively associated with ration energy and nonstructural carbohydrate contents. Significant influences of specific feeds on MU were detected. A significant negative association was found between MU level and PR. Least squares means for PR for cows in the lowest and highest MU quartiles were 38.4 and 36.1%, respectively. Increasing levels of MU were negatively related to reproductive performance of dairy cows, but the risk of nonpregnancy caused by high levels of MU was lower than reported in previous studies.

Epidemiological investigations of an outbreak of intestinal atresia in two Israeli dairy herds.

An epidemiological investigation of an outbreak of intestinal atresia in Israeli Holstein-Friesian newborn calves showed a linkage with rectal palpation for early pregnancy diagnosis, performed less than 42 days after insemination. The odds of an exposed calf, i.e., one born to a dam that was diagnosed by early palpation as having intestinal atresia were 119.7 times higher than one born in normal control herds (95% CI; 7.4-1946.3). A total of 682 calves-at-risk was recorded from mid-1998 to mid-2000 and a total of 47 calves (6.9%) were born with intestinal atresia during this period. Two forms of intestinal atresia were recognized at post-mortem: atresia coli and atresia ilei.

Phenotypic characteristics of Staphylococcus aureus isolated from bovine mastitis in Israeli dairy herds.

A study of the characterization of the phenotypic patterns of Staphylococcus aureus strains isolated from bovine subclinical mastitis in Israeli dairy herds and their correlation with the severity of the disease was undertaken. A total of 400 chronically S. aureus-infected Israeli-Holstein cows, from 15 dairy herds were included in this study. Based on the results of the biochemical reactions, of the anti-biogram and phage typing, one major type of S. aureus was determined in each herd, its prevalence being between 54 and 100% of the total isolates from that same herd. The majority of the isolates were found to be non-haemolytic (62.7%). The most common phage type was 3/A,3/C,55,71, which was predominant in five herds. In two herds none of the isolates (24) were typable by this set of phages. All isolates were susceptible to methicillin, erythromycin, cephalotin, norfloxacin, trimethoprin-sulphamethoxazole and novobiocin. Most isolates were resistant to penicillin (96.6%) and 52% to oxytetracyclin. Differences in protein patterns between 50 and 36 kDa were found by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis. No correlation between any combination of the phenotypic characteristics was found when correlation was done with milk yield and somatic cell count, corresponding to the 6 months before sampling. Otherwise, a positive correlation was found between type of haemolysis and the N-acetyl-beta-glucosaminidase (NAGase) values. In milk from quarters infected with the-non-haemolytic strains, the level of NAGase was significantly lower (P < 0.05) than that from quarters infected with the haemolytic strains (69.7 and 105.9, respectively). However, the level of NAGase activity in the milk of the quarters infected with the non-haemolytic strains was significantly higher (P < 0.05) when compared to the milk of quarters infected with coagulase-negative staphylococci (43.5).

Ulcerative lymphangitis and coronet lesions in an Israeli dairy herd infected with Corynebacterium pseudotuberculosis

An Israeli dairy herd which had experienced a severe outbreak of Corynebacterium pseudotuberculosis infection in 1991 suffered a second outbreak in 1998, the first time since the disease was first...

Clinical, bacteriological and epidemiological aspects of clinical mastitis in Israeli dairy herds

A 4-year retrospective study was performed to determine the clinical, bacteriological and epidemiological aspects of acute clinical mastitis in seven Israeli dairy herds. A total of 1124 clinical mastitis cases were detected by abnormal changes in the milk and udder with concurrent decrease of at least 25% in daily milk production. A total of 1190 quarters were affected with clinical mastitis in 1089 cows. The rear quarters had a higher incidence risk (64.7% of quarter cases) than the front quarters. The annual herd-year-incidence varied from 4.2 to 126.8 cases/100 cows/year. The whole-lactation incidence risk (LIR) was 20.8 per 100 lactations. LIR increased from the first to fifth lactation and then decreased. Most clinical mastitis cases were associated with coliform bacteria (60.2% of cases), environmental streptococci (18.6%), coagulase-negative staphylococci (8.7%) and samples from which no bacterial growth was detected (8.1%). Most cases of clinical mastitis occurred in the early stages of lactation, with 51.4% of all cases, 52.3% of coliform cases and 54.6% of environmental streptococci mastitis cases occurring during the first 4 months of lactation. The median days in milk at diagnosis was 118 days. The incidence was lower in the dry summer months. The ratio of peak to low incidence was 1.62 with a calculated peak incidence in January.

Epidemiology of bovine abortions in Israeli dairy herds

Routine monitoring of abortions is carried out on most Israeli Kibbutz dairy herds. The reports include both descriptive epidemiology and multivariable analysis. Data are presented according to parity, trimester, abortion curves and sire. Results are produced in the form of abortions per 10 000 cows-days-at risk, proportion of aborted cows by 260 days of gestation, abortion per confirmed pregnancy, and adjusted odds ratios. For 58048 pregnancies from 111 herds in 1995, the respective abortion density, proportion of aborted cows, and abortions per confirmed pregnancy were 4.2, 5.9%, and 10.2%. Among parities, heifers had the lowest, and cows of second parity the greatest risk of fetal death (respective odds ratios 0.6 and 1.3) compared to all other parities pooled together. The greatest risk of fetal death was observed in the first, and the lowest in the second trimesters of pregnancy (odds ratios 1.9 and 0.6, respectively). Recurrent risk ratio for abortion in the same lactation was high (odds ratio 2.7). Respective proportions of aborted cows with and without a previous abortion were 17.5% and 5.9%. Odds of aborting after twinning in multiparous cows was 1.3 greater than for those having a single calf. Risk of abortion in the autumn and early winter was greater than that in the summer months. Increased risks of abortion were associated with eight sires out of the 233 used (odds ratios of mates to abort ranged from 1.9 to 3.9). One, two and three peaks of abortions were established in 53.2%, 24.3%, and 0.9% of the 111 herds studied in 1995. None were detected in 21.6% of the herds.

Spread of lumpy skin disease in Israeli dairy herds

Fourteen of the 17 dairy herds in Peduyim, an Israeli village, became infected with lumpy skin disease during a period of 37 days in August and September 1989. One cow in one neighbouring village and four cows in another neighbouring village also became infected, probably through being treated by a veterinarian who treated cows in Peduyim. Circumstantial evidence suggests that the original infection was brought to Peduyim and spread by stable flies (Stomoxys calcitrans) carried by the wind from foci of the disease at El Arish in northern Sinai, or at Ismailiya and the Nile delta in Egypt. All the cattle and the small flocks of sheep and goats in the village were slaughtered.

Enquête sur la dermatophilose des bovins laitiers en Israël

In Israel, dermatophilosis was found to inflict severe lesions, especially in first-calving cows during the first weeks post-parturition. Decreased milk production (by 40% on average) was also noted. Acute exudative dermatitis was observed in these animals. Severely reacting animals (570 in 38 kibbutz herds and 15 animals in 4 family herds) were treated with antibiotics. All these animals also suffered either from endometritis/metritis or mastitis. The "tumoral" form of dermatophilosis was observed on 3-week-old or younger calves. Dermatophilosis was especially prevalent (89.4%) in dairy herds in which intensive showering of lactating cows is practised during the spring and summer months, in comparison to the family herds where the morbidity rate was lower (6.6%). Morbidity rates were found to be higher in the humid Mediterranean Coastal Plain (66.3%) than in the arid or semi-arid regions (Negev and Arava Valley) of Southern Israel (3.7%). Five clinical forms of dermatophilosis and the epizootiological aspects of the disease in Israeli dairy herds are described. It is concluded that a reduction in the prevalence of dermatophilosis could be achieved by decreasing the frequency and the intensity of showering currently applied under the kibbutz management system.

An outbreak of Corynebacterium pseudotuberculosis infection in an Israeli dairy herd

An outbreak of Corynebacterium pseudotuberculosis infection in an Israeli dairy herd appeared in four clinical forms: cutaneous, mastitic, visceral and a mixed form. Only cows were affected and susceptibility increased with age. Most cases occurred during a short period in the summer months. The total morbidity rate was 13.7 per cent involving 41 cows. Thirty cows were affected by the cutaneous form, five by the mastitic form, four by the mastitic and cutaneous forms, one by the mastitic and visceral forms and one by the visceral form. The cutaneous form appeared as one or two pyogranulomatous lesions affecting the body or head. Subclinical to severe clinical mastitis was found in the mastitic form. In the visceral form the upper and lower respiratory system were affected by multiple purulent lymphadenitis. All the cutaneous lesions recovered irrespective of treatment. Mastitis did not respond to treatment and severely affected milk production in most cases. All the isolates of C pseudotuberculosis were nitrate reductase negative. Most isolates were sensitive to norfloxacin, cephalothin, methicillin, kanamycin and furazolidone and resistant to ampicillin, lincomycin and neomycin.

Epidemiological study on factors influencing fertility indices in Israeli dairy herds

The objective of this study was to determine feeding factors connected with differences in the fertility of Israeli Kibbutz dairy herds. In an epidemiological case-control survey, data from 30, low-fertility Kibbutz dairy herds having a mean overall conception rate of 35% in multiparous cows were compared with the data from 30, high-fertility Kibbutz dairy herds having a mean overall conception rate of 48% in multiparous cows. Nutritional factors accounted for 67% of the differences between low-fertility and high-fertility herds in the overall conception rate of multiparous cows, while only 4.8% could be related to the body condition during the dry period. Among the factors which occurred more frequently in the low-fertility than in the high-fertility herds were 1) a higher average protein density and lower energy/protein ratio was fed during lactation and 2) a single feeding group was maintained for all lactating cows. 3) There were phytoestrogens in the silage or alfalfa hay, fed during lactation. 4) Faulty dry period was instituted, which was defined as the presence of at least one of the following three practices: a) the daily feed was above 3 kg of high lactation mix; b) more than 15 Mcal of net energy per day was given during the first part of the dry period; c) more than 30% of the cows were obese during the dry period. Three or more risk factors were found in one high-fertility herd and in 20 low-fertility herds. This finding emphasizes the importance of identifying and removing risk factors as a possible means for improving the reproductive performance of herds.

Analysis of fertility indices of cows with reproductive disorders and of normal cows in herds with low and normal fertility

Semiannual computer printouts of reproductive disorders diagnosed in high producing Israeli dairy herds were evaluated for a comparison of fertility indices of diseased and normal cows in low (LFH) and normal fertility herds (NFH). In 16,910 cows, conception rates to first AI in cows with reproductive disorder were >50% below those in normal cows (P<0.001). For both groups of cows, conception rates were lower in LFH (P<0.0001). A comparison of fertility indices between LFH (5, 171 cows) and NFH (14,573 cows) revealed, in addition a higher overall conception rate and a lower percentage of cows still open on Day 150 post partum (problem cows, (P<0.0001), as well as a higher pregnancy rate for NFH (P<0.001), for cows with reproductive disorder and for normal cows in these herds. In herds with predominantly uterine-related reproductive disorder, a high incidence of postpartum anestrus was seen infrequently; while in herds with a high incidence of postpartum anestrus, postbreeding anestrus was equally high (P<0.05 − 0.001). In general reproductive disorder have been shown to have long-term negative effects on fertility indices in both LFH and NFH, but with more serious consequences in LFH. Since a sizeable percentage of normal cows can be identified, reproducing normally under identical management conditions, cows in both kinds of herds with reproductive disorder must be less resistant to environmental stress. Thus, while cows with reproductive disorders maintained their general health and their high level of productivity, they responded either immediately with uterine disturbances or they refused to cycle properly, and they conceived later. A case can be made that all reproductive disorders represent disease entities influenced by management factors.

Comparison of proven sires from five Holstein-Friesian strains in high-yield Israeli dairy herds

Nulliparous Israeli Holstein heifers were inseminated in 111 high-producing dairy herds with 9411 doses of semen from 26 proven sires of five national strains: Canada (CA), New Zealand (NZ), Sweden (SW), Israel (IS) and United States (US); 4914 calves were born and 1483 F 1 daughters were milk recorded. Significant differences among strains were found for all traits analyzed. Mates of NZ sires and daughters of IS sires were most favorable for calving traits and mates of SW sires and daughters of CA sires were least favorable. NZ daughters were smallest, and CA daughters were largest and most favorable for udder conformation traits. SW daughters were least favorable for conformation traits, but had the highest conception rate. US daughters had the lowest conception rate. The ranges of strain effects for milk, fat and fat percentage were 1551 kg, 27 kg and 0.28%, respectively. IS daughters were highest for dairy character and milk and fat production, but lowest in fat percentage. NZ daughters were lowest in milk and fat production, but highest in fat percentage. The correlations between predicted differences for kg fat and kg milk and fat percentage were 0.96 and −0.85, respectively. Within-strain correlations between sire evaluations for milk in each of the countries of origin and IS were 0.84, 0.80, 0.51 and 0.01, for US, SW, CA and NZ, respectively. The results provide a basis for comparison of sire evaluations among US, CA, SW and IS.

Nutritional influence on fertility in Israeli dairy herds with an average 305-day production per cow of 8000 kg of fat-corrected milk

Fertility and nutritional data from 13 Israeli-Holstein Kibbutz dairy herds, which were milking a total of 3314 cows and heifers, with an average 305-day production of 8,649 Kg of fat-corrected milk, were collected, compared and analyzed. The following fertility data were observed: Overall conception rate (OCR), 39.2%. Retained placenta, 7.65%. Metritis, 5%. Anestrus, 9.9%. Suspected early embryonic resorption, 5.3%. Repeat breeders, 12.2%. Problem cows (not pregnant 150 days postpartum), 22.5%. These herds were divided into two production groups. One group consisted of 8 herds producing 8,000–8,500 Kg. (average 8,253 Kg); and the other group of 5 herds producing 8,900–9,800 Kg (average 9,284 Kg). There was no significant difference in the fertility data obtained from these two groups. A division of these 13 herds into 3 groups based on overall conception rate was made as follows: 4 herds with high OCR, above 45%; 6 herds with medium OCR, 35–41%; and 3 herds with low OCR, less than 31%. There were no significant differences between these 3 groups of herds in percentages of retained placenta, metritis, anestrus and suspected early embryonic resorption. The percentage of repeat breeders was 6.9 in the high group, 9.4 in the medium group and 20.6 in the low group. All three differences were significant. The percentage of problem cows was 16.5%, 22.5%, and 30.6%, respectively. There was a significant difference between the high and low OCR groups. An analysis of the nutritional data showed that in the first half of the lactation period (high production period) there was a significant difference between all 3 groups in the percentage of roughage fed. In the second half of the lactation period the difference in digestible protein fed to the high and low OCR groups was nearing significance. The overall amount of energy fed during this same period was 17.9 Scandinavian Feeding Units (SFU) in the high; 16.7 SFU in the medium, and 15.9 SFU in the low group. None of these differences was statistically significant.