BLAD genotypes and cow production traits in Hungarian Holsteins

Bovine Leukocyte Adhesion Deficiency (BLAD) is a recessive autosomal inherited disease in Holstein–Friesian cattle. BLAD is caused by a deficiency in a Mac‐1 (CD11b/CD18) leukocyte‐surface glycoprotein involved in the defence mechanism against infections. A granulocytopathic syndrome was described in Holstein cattle ( Hagemoser et al . 1983; Nagahata et al . 1987; Takahashi et al . 1987), and Kehrli et al . (1990) later demonstrated that this disease was equivalent to BLAD. BLAD is genetically identical and phenotypically similar to the human LAD ( Springer et al . 1984), and to the condition identified in Irish Setters (Renshaw & ; Daves 1979) . Until now BLAD has been identified in the Holstein–Friesian breed only in the United States of America (US) and in other countries importing Holstein cattle. In BLAD‐affected calves (homozygotes) there is a defect in the surface of the neutrophile granulocytes, where neutrophile migration through the vascular endothelium into the extravascular tissue cannot occur. The neutrophiles of these calves are unable to reach the inflammatoric sites. BLAD is lethal for the affected (homozygote) calves. These calves would probably be the first ones to die if a disease outbreak occurred on a given dairy farm. It is also possible that affected calves might die as a result of disease caused by normal flora. The majority of BLAD calves die before reaching 1 year of age. Some animals may live past 2 years of age but are severely stunted in growth and suffer from various infectious conditions. To detect BLAD carriers a polymerase chain reaction (PCR)‐restriction fragment length polymorphism (RFLP) test was introduced by Shuster et al . (1992), and the test was later improved among others by Tajima et al . (1993), Batt et al . (1994), Mirck et al . (1995), Tammen et al . (1996) and Zsolnai & Fésüs (1996). Due to the wide use of BLAD heterozygote US Holstein–Friesian top AI breeding bulls in many countries having black and white and Holstein–Friesian population, quite a high incidence of carriers has been reported ( Takahashi et al . 1987; Tajima et al . 1993; Jørgensen et al . 1993; Grzybowski et al . 1994; Duesmann 1994; Lüpsik et al . 1995; Kirilenko & Glazko 1995; Boichard et al . 1995; Kostetskij et al . 1966; Poli et al . 1996; Yakovlev et al . 1996; Tammen et al . 1996; Powell et al . 1996; Fésüs & ;, –; Anton 1997) . Since some breeders supposed that the reason for the spread of the BLAD defect was the better production of the carrier animals, in 1991 the Holstein Association of America implemented a BLAD control programme and many countries took similar measures as well. The majority of the few studies which have been carried out so far do not support the above hypothesis and have not demonstrated any positive effect of the BLAD gene on production traits. Jørgensen & Madsen (1994) studied the effect of the BLAD genotypes on some performance test data (weight at day 42 and at 336, daily gain, feed utilization and ultrasonic muscle area) in Danish Holsteins. Non carrier (TL) bulls showed a better feed utilization of 0.07 SFU/kg gain than BLAD‐carriers (BL). All other contrasts between carriers and non carriers were not significant. InFrance, Boichard et al . 1995) tested the putative association between the BLAD gene and five productive traits, milking ease, as well as 15 type traits, with a granddaughter design involving 620 AI bulbs. No significant association was detected. It was concluded that the recent spreading of the BLAD mutation cannot be explained by a linkage with a quantitative trait locus (QTL) for a selected trait. The daughters of 153 BL‐type Hungarian Holstein–Friesian bulls produced significantly more milk, milk fat and milk protein than the daughters of TL bulls ( Dohy et al . 1996). In a study with US Holsteins Powell et al . (1996) observed a negative effect on some selected production traits in BLAD carriers and concluded that selection against BLAD would not negatively influence herd production level. In another Hungarian study Jánosa & Dohy (1997) when analysing the progeny‐testing data of 107 Hungarian and 153 Dutch Holstein–Friesian bulls compared the INET values of the BL and TL groups and some significant advantages for the BL group were demonstrated. In their recent study with Danish Friesian bulls Jørgensen (1997) found that carriers of BLAD had poorer feed utilization than non carriers and tended to grow more slowly. In this paper some selected production traits of Hungarian Holstein–Friesian BL and TL type bull rearing cows are compared. Materials and methods Between May 1993 and September 1997 a total of 236 AI bulls, 720 breeding bull rearing cows and 266 young breeding bull candidates were BLAD‐typed. The cows originated from 21 herds. All tested animals belonged to the Holstein–Friesian breed. The effect of the cows’ BLAD status on the following production traits was estimated: age at first, second and third calving; calving interval; number of milking days in lactation, milk (kg), milk fat (%), milk fat (kg), milk protein (%), milk protein (kg); milk production (kg), milk fat (%), milk fat (kg), milk protein (%) and milk protein (kg) in 305 day lactation. All production trait data were obtained from the authorities responsible for collection and processing data for breeding‐value estimations in registered herds. DNA for the PCR‐RFLP BLAD typing was extracted from whole blood samples, occasionally from frozen semen in the case of some bulls. The primers described by Shuster et al . (1992) were used in the early stage of the studies, and later those published by Schwerin et al . (1994). Details of the typing method were given elsewhere (Fésüs & Zsolnai 1995). Later an improved and simplified method allowing simultaneous genetic typing of the κ‐casein and BLAD loci was developed. One of the primers was changed and the resulting new primer differed in two base pairs from that described by Mirck et al . (1995). At present DyNAzyme is used instead of Taq. As a result of the above changes, the amplification is simpler and the quality of the electrophoretic pattern is improved (Zsolnai & ; Fésüs 1996) . Data analysis was performed using factorial analysis of variance ( SPSS USER’S GUIDE 1993), assuming fixed models (see below), and the F ‐test was applied to demonstrate significance of differences. The level of significance was a priori determined at 0.05. Statistical models for various traits are as follows (Neter & Wasserman 1974): I: Days between calvings, agewhere μ is the mean, a is the effect of herd, c is the effect of year of calving, k is the treatment effect (BLAD group BL, TL); and ɛ is the random error. II: Production traits (milk (kg), fat (kg) and so on)where α is the intercept, a, c and K are as given above, d is the effect of parity, X is the age at calving as a covariate, and ɛ is the random error. Results and discussion In Hungary the BLAD problem was mentioned for the first time in 1994 by Mészáros (1994). Hungary has one of the largest US Holstein–Friesian population in Europe. Many of the AI breeding bulls in earlier years and at present are closely related to two Osborndale Ivanhoe descendants, namely to Carlin‐M Ivanhoe Bell and Penstate Ivanhoe Star, and these bulls, like Osborndale Ivanhoe, were of the BL type. M észáros drew attention to the importance of BLAD typings in Hungary. The first BLAD typings were made in late 1993 for the Hungarian Artificial Insemination Co. (Gödöllö, Nagyremete) and some months later the BLAD eradication programme of the Hungarian Holstein–Friesian Breeding Association was started. In this country‐wide marker assisted selection (MAS) programme AI breeding bulls, bull rearing cows as well as young breeding bull candidates are being BLAD typed. The BL genotype frequency values estimated for AI bulls and for bull rearing cows ( Fésüs et al . 1997) are close to the values obtained in the US, and considering the predominantly US origin of Hungary’s Holstein–Friesian population, this is not surprising. Because of the controlled semen and embryo importation and the introduction of the BLAD eradication programme, the number of BL individuals will be considerably reduced in the near future in the Hungarian Holstein–Friesian population. Some BL‐type breeding animals are still being used in planned matings; in this way the birth of carrier calves can be avoided. The results of comparisons of production traits of BL and TL bull rearing cows are shown in Table 1. 1 . BLAD‐genotype effects on some selected production traits of Hungarian Holstein–Friesian bull rearing cowsTotalBLTLProduction
traitsnx̄nx̄nx̄Signifi‐ 
canceAge at first calving426  797.0042  805.00384  797.000.319at second calving1571 234.00161 249.001411 233.000.574at third calving661 663.0071 656.00591 664.000.405Calving interval (days)223  429.0023  456.00200  427.000.161Number of milking days in whole lactation649  379.0065  380.00584  379.000.622Milk (kg)64911 263.006511 503.0058411 236.000.474Milk fat (%)649   3.5365   3.59584   3.530.131Milk fat (kg)649  396.0065  411.00584  395.000.142Milk protein (%)649   3.2265   3.21584   3.220.285Milk protein (kg)649  362.0065  371.00584  361.000.277305‐day lactation milk production6499 733.00659 854.005849 720.000.788Milk fat (%)649   3.4965   3.53584   3.470.171Milk fat (kg)649  336.0065  345.00584  335.000.184Milk protein (%)649   3.1765   3.17584   3.170.334Milk protein (kg)649  308.0065  312.00584  307.000.385None of the differences between BL‐TL‐type cows proved to be statistically significant in the case of the production traits examined in this study. The lack of association of the BL type with production indicates that the presence of the autosomal recessive BLAD mutation does not result in a higher level of production in Hungarian Holstein–Friesian cows. These findings are in accordance with the results of most earlier studies ( Jørgensen & Madsen 1994; Boichard & Amigues 1995; Powell et al . 1996; Jørgensen & Madsen 1997), but are in contrast to former investigations on Hungarian Holsteins, where some significant productive advantages were demonstrated for the daughters of BL‐type AI bulls (Dohy et al . 1996; Jánosa & Dohy 1997). In the present study the influence of the cows’ own BLAD genotype on some production traits has been estimated, and the authors believe that this approach has provided more reliable information to be used in selection. Since the calf deaths occurring in the post‐weaning period represent a major source of reduced profitability in most dairy units, the selection against BLAD carriers is highly justified. The selection approach, applying the available DNA test, can be a quick and efficient way of removing the disadvantageous BLAD mutation from the Hungarian Holstein–Friesian population. The results presented in this paper indicate that the application of such selection in the Hungarian Holstein–Friesian population will not result in reduced cow productivity. Literature data on the origin, occurrence and production effects of the recessive inherited disorder BLAD (bovine leukocyte adhesion deficiency) in the Holstein–Friesian breed are discussed. Most studies carried out so far have indicated no significant advantages for the BL type and it has been concluded that selection against BLAD would not negatively influence herd production level. In this paper some selected production traits of Hungarian Holstein–Friesian BL and TL type bull rearing cows are compared. None of the differences between BL and TL type cows proved to be statistically significant in the case of the production traits studied. The application of selection against BLAD in the Hungarian Holstein–Friesian population will not reduce cow productivity.