Excessive and prolonged negative energy balance (NEB) has become a major problem in the modern high yielding dairy cow, leading to metabolic disorders, poor fertility and subsequently increased culling rates. Exploring potential indicators and possible strategies to reduce excessive NEB is imperative to improving the sustainability of this system. In this study, treatment effects on animal behaviour patterns (used in assessing animal welfare) were investigated in an attempt to identify possible indicators of compromised welfare. A change in the frequency and duration of behavioural activities may be associated with an excessive NEB and prove useful in early detection of metabolic problems.

Correlation among type traits and milk production has been investigated by Meyer (1987), Brotherstone (1994) and Misztal et al (1992).One of the primary reasons for collecting and utilizing information on type traits is to aid breeders in selecting profitable functional cows for high production and suitable herd life. The objectives of this study were to estimate phenotypic and genetic correlations among milk production and udder type traits.

Genetic improvement of farm animals is the process of selecting animals of higher genetic merit than average to be parents of the next generation such that the average genetic merit of their progeny will be higher than the average of the parental generation. In practical dairy cow breeding programmes, many traits such as milk production and fitness traits (consisting of health, fertility, calving ease, temperament and length of herd life) are commonly included in breeding objectives among which milk production is the most important trait and also the main determinant of income to dairy farmers. On the other hand, age at first calving is economically important because it determines when an animal begins its productive life and therefore could influence the lifetime productivity of an animal. Moreover, age at first calving can be considered as a measure of heifer fertility performance associated with reproductive efficiency. The main aim of the present research is multivariate genetic analysis of first lactation milk yield at different calving ages of Iranian Holstein heifers in Khorasan province of Iran.

The main aim of animal breeding programmes is to increase productivity and profitability of farm livestock through genetically improving the economic merit of farm livestock (Smith, 1998). This can be achieved by increasing the mean value of a population for one or several economically important traits by the genetic improvement of the animals in this population. In dairy cow husbandry, many traits of economic importance such as milk production and reproductive traits has long been of interests for breeders to increase profitability of dairy farm enterprise. Herd life, as a complex trait associated with longevity of animals, has been long considered to be related to profitability of dairy herds due to reduce replacement costs and increase the proportion of farm resources used for the milking herd rather than for replacements (Brotherstone et al., 1998). In fact, as pointed out by Burnside et al. (1984), lifetime profitability is affected by many factors such as production per lactation, length of productive life, age at first calving, calving interval as well as input and output prices. The main objective of the present study was to estimate heritability of herd life for register and non-register Iranian Holstein heifers.

In animal breeding programmes knowledge of the genetic properties of the traits under consideration is the first prerequisite in establishing a selection criterion. Several methods such as ANOVA, ML and REML have been utilised to estimate variance and covariance components in animal breeding data which are usually originate from selection experiments. Modified ML procedure which is so-called restricted maximum likelihood (REML) has been widely used due to its statistical desirable properties. To apply the REML method, a number of algorithms such as DF-REML, EM-REML and scoring have been developed to maximise likelihood function in order to estimate variance and covariance components. Expectation-maximisation (EM-REML) is an algorithm in which first derivatives of the likelihood needs to be evaluated numerically or analytically. The main objective of the present study was to estimate phenotypic and genetic associations among milk, fat and protein yields as well as fat and protein percentages in Iranian Holstein heifers based upon applying the EM-REML method through using a multiple trait animal model.

Leptin is a 16-kDa protein that is synthesized by adipose tissue and is involved in regulation of feed intake, energy balance, fertility and immune functions. It has been shown that leptin gene influences milk performance in cattle (Liefers et al., 2002). Leptin is related to both energy metabolism and reproduction and it was shown that leptin polymorphisms had significant effect on calving interval and weight at first calving in beef cows (Almeida et al., 2003). In cattle, the leptin gene is located on chromosome 4 and consists of three exons. The aim of this study was to indicate polymorphism at the bovine leptin gene locus in Iranian Holstein dairy cows and its contribution to the first cumulative 60-d milk yield, 305-d milk yield, days to first breeding (DFB), days open (DO), and days from first breeding to conception (DFBC) in the previous lactations.

Mastitis is a complex disease causing inflammation of the udder, which has been estimated to cost the dairy farmer between £40-£117/cow per year (Stott et al., 2002). Economic loss occurs as a result of discarded milk, reduced milk yield and milk quality, increased vet costs and an increase in replacement costs. The objective of this study was to examine the effect of breed on the incidence of mastitis and somatic cell counts and milk production capabilities of Holstein Friesian, Brown Swiss and Brown Swiss crossbred cows.

K-Casein (CSN3) is a phosphoglycoprotein that constitutes approximately 12% of the casein complex of bovine milk. The amount and type of CSN3 present in milk vary considerably depending on the individual cow. The use of small quantities of 2-mercaptoethanol in electrophoretic separation led three independent groups to the discovery of two distinct bands of protein denoted as A and B corresponding to CSN3. Later studies showed that the presence of these bands were due to genetic polymophism of this protein. Variant B differs from A by having isoleucine and alanine at positions 136 and 148, respectively, instead of threonine and aspartic acid in the 169 amino acid sequence. In the most cattle populations, there is a predominance of the A over the B type of CSN3 (Ng-Kwai-Hang et al. 1991). However, it has been demonstrated that CSN3 B would be more desirable than CSN3 A because this form is associated with higher casein content in milk, higher cheese-yielding capacity, more favorable cheese composition and better coagulating properties in terms of rennet clotting time and curd firmness (Ikonen et al. 1999). Therefore, it seems desirable to increase the frequencies of B type of CSN3 through appropriate selection and breeding schemes. This paper reports the genotyping for CSN3 gene and his allele frequencies done for 53 animals of Mongolian breed. Because, heretofore genotyping of CSN3 gene for this breed has not reported, moreover milk of this animals used in cheese industrial.

The persistency of dairy milk yield, which refers to the degree to which milk yield is maintained from month to month by the cow during her lactation, is an economic trait. The knowledge of persistency is important for herd management and selection strategy. The benefits of selecting for lactations that are more persistent were only speculative, because very little research has been published. As the time goes by, the more is learned about this trait and its relationship with other important traits. The persistency can be defined in several ways, as either ratios of yield in different parts of lactation period, to be derived from factors in lactation curves models as proposed by Wood (1967) or a simple statistical parameter computed from test-day yield records(3). The incomplete gamma function, which described by Wood is one of the most popular models used to describe the lactation curve: yt = atbe-ct where yt = milk yield on day t, a= a parameter to represent yield at the beginning of lactation, b and c are factors associated with the inclining and declining slope of the lactation curves, respectively. The objectives of this study were to estimate genetic and phenotypic parameters for different criteria of persistency, finding correlation between them and their relationships with 305-days milk yield, by applying REML under animal models in the Holstein dairy cattle of Iran.

Kappa Casein (◻-casein) is a protein in mammalian milk whose two common genetic variants of A and B are well known. The A variant has a Thr and Asp at positions 136 and 148, while the B variant has Ile and Ala in these positions. Difference at position 148 can be detected by PCR-RFLP (Medrano and Agiular-Cordova, 1990). These two alleles determine great differences in milk, casein, protein and fat yields as well as cheese making properties such as coagulation time and curd firmness, with a superiority for cheese production of the κ-casein BB compared to κ-casein AA milk (Lodes et al., 1996). Several internationally studies have been focused on determining the frequency distribution of the various milk protein alleles in different animals. It is important to study not only the major breeds but also those with small animal numbers (Erhardt, 1996). The aim of this study was to estimate the allelic frequency in polymorphic site of exon 4 of κ-casein gene in three Iranian native and Holstein cattle.

Leptin is 16 KD, a protein that is synthesized by adipose tissue, and it is involved in the regulation of feed intake energy balance, fertility and immune function. In cattle, the leptin gene is located on chromosome 4. It consists of 3 exons and 2 introns and of those only 2 exons translate into protein. Leptin treatment of animals has been shown to cause a decrease in food intake, body weight loss, fat depot weight loss and increase in energy metabolism therefore leptin not only causes a reduction in food intake but the potential body weight losses are enhanced due to an increased metabolic rate. Leptin may be involved in regulating reproduction in that if may also act as the signal to the reproductive system that sufficient body fat exists to support a successful conception and pregnancy. Lindersson et al (1998) reported QTL for milk production traits close to the leptin gene (82.8 cm). Liefers et al. (2002) reported that heifers with the sau3IA – AB genotype produce 1.32 kg/d more milk and consume 0.73 kg/2 more food compared with the sau3AI - AA genotype. They suggested that RFLP – B alleles could yield a higher milk production without negatively affecting energy balance and fertility. The aim of this study is to estimate the frequency of the leptin gene in Brown Swiss cows and the relationship between polymorphisms at the bovine leptin gene locus with variation in milk production and reproduction traits.

Declining fertility is a major problem on dairy farms throughout the United Kingdom, with a recent farm survey identifying infertility as the primary reason for culling dairy cows in Northern Ireland (Mayne et al., 2002). This decline in fertility is often attributed to the focus on milk production within the Holstein-Friesian breed, and as a consequence, there is a growing interest in alternative dairy cattle breeds and in the use of crossbreeding. Norwegian dairy cattle (NRF) have been evaluated at the Agricultural Research Institute of Northern Ireland since 2000, with a recent on-farm study indicating a significant improvement (P<0.05) in conception to 1st service with NRF compared to Holstein dairy cattle (Ferris et al., 2004). This study examines the reproductive performance of Holstein and Norwegian cattle, and of crossbred animals of these two breeds.

Calving difficulty, biologically and statistically, have special characteristics which require researchers to use more complex models for its analysis. First, it is influenced by maternal effect and therefore the models should take this aspect into account. This is why animal models with maternal effect or sire-maternal grandsire models are employed. Secondly, it is recorded subjectively using usually five scores, one for a normal delivery to five for a Caesarean parturition. In other words, calving difficulty is a discrete trait and is not distributed normally. In theory, methods for analyzing continuous data are not appropriate for categorical data. In the 1980s, researchers developed a standard threshold model (a nonlinear model) for genetic analysis of these traits (Harville et. al. 1984). In the threshold model each phenotype in the categorical scale is associated with an unobservable underlying continuous variable with normal distribution. The objective of this study was to estimate (co)variance components of calving difficulty and genetic parameters using a threshold model.

Major histocompatibility complex genes, also called bovine lymphocyte antigen (BoLA), have received attention because of their association with host immunity. The BoLA gene is located on the short arm of bovine chromosome 23. In the class II region of the BoLA gene, at least 12 loci have been described including in the class IIa region: DRA, DRB1, DRB2, DRB3, DQA, DQA2, DQB1, and DQB2; class IIb region: DYA, DYB, DIB, and DOB. Lewin H. A. (1996) identified 35 DRB3 alleles in exon 2 with a technique described by van Eijk et al. (1992) involving polymerase chain reaction (PCR) and endonuclease restriction fragment length polymorphism (RFLP). The BoLA-DRB3.2 locus is highly polymorphic; more than 54 different alleles have been reported. The BoLA-DRB3.2 alleles potentially affect many traits related to immunity, SCC, and mastitis incidence. Associations have been made with some infectious diseases of cattle and BoLA genes. Others indicated that one BoLA-DRB gene pattern was associated with resistance to Staphylococcus aureus mastitis, BoLA-DRB3.2*8, *16, *22, and *28 alleles were associated with elevated SCC and cows with BoLA-DRB3.2*16 and *24 were more susceptible to IMI caused by major mastitis pathogens. Furthermore, cows with BoLA-DRB3.2*ll, *12, and *23 alleles were more resistant to clinical mastitis and to IMI caused by major mastitis pathogens, however BoLA-DRB3.2 *16 was associated with lower SCS in Holsteins and BoLA-DRB3.2 *23 was associated with severe coliform mastitis. Most of the previous studies of the BoLA-DRB3.2 gene have involved Holstein cows or a combination of various breeds. Few studies have analyzed exclusively the BoLADRB3.2 gene of Iranian Sistani cattle and has not reported frequency of BoLA-DRB3 alleles in Russian Yaroslavl breed. The purpose of the present study was to determine the BoLA-DRB3.2 allele pattern in Iranian Sistani and Russian Yaroslavl breeds.

Many studies were already focussing on ways to improve the nutritional quality of milk fat. The most popular way to improve nutritional quality is by feed supplementation; however these methods present certain disadvantages. Most important is that this improvement is not sustainable. If the supplementation stops, the nutritional quality disappears. A genetic improvement however is complementary to feeding and has the additional advantage to create additional value for the animals through selection. However studying the genetics of nutritional quality of milk fat requires a lot of data. The objectives of this study were to use medium infrared spectrometry to get this data and, by using these predicted quantities of fatty acids in milk and milk fat, to study the differences in fatty acids profiles of milk within and across breeds.

In Western Patagonia (Chile), sheep production is a key contributor to the local economy. Sheep production in Patagonia is largely based on the Corriedale, a dual-purpose breed used for apparel wool and prime lamb production. Over the last decade the relative value of sheep meat compared with wool production has greatly increased. Consequently, there is interest in using terminal sire breeds to improve growth and carcass quality in lambs. In view of this background a study is being undertaken to investigate the relative performance of four sire breeds across a range of sheep systems in Western Patagonia. This paper reports on the results from the first year of this two-year programme.

The construction of selection indices for sheep improvement programmes requires reliable estimates of the genetic and phenotypic correlations among traits in the selection objective and the criteria on which selection is based. Parameter estimates for growth, ultrasonic predictors of body composition and slaughter traits are scarce for sheep reared in a hill environment in comparison to the information available for terminal sire breeds (Conington et al., 1998). The aim of this study was to estimate the genetic parameters of growth and carcass characteristics of lambs reared in a hill environment when slaughtered at a constant level of finish.

Systems analysis enables us as to know how the genetic, management, or environmental changes affect the system or how the system should be used for testing new hypothesis (Cartwright, 1979). Modelling is a major tool in this respect. The objective of this study was to develop two computer programs with year-by-year flow chart presentation to adopt the optimum-design, two-breed crossbreeding systems for self-contained meat sheep enterprises. The economic consequences based on the user-input data envisaged for a 10-year time period.

Many studies have been carried out to determine the quantity and quality of mohair production, and high variation reported by some workers for fleece trait in Angora goats (1, 2, 3, and 4). But very little is known about mohair production in colour coated Markhoz goats. The objective of this study was to determine the fleece characteristics, analyse the effects of some environmental factors on fleece traits and estimate the heritability for the average fibre diameter and yearling fleece weight in Markhoz goats.

Animal maturity is an important concept in the meat industry, with emphasis on producing less mature (i.e. “physiologically younger”) animals with superior carcase characteristics such as greater tenderness and lower fatness. Unfortunately the concept of ‘maturity’ remains poorly defined. Where specified, ‘maturity’ usually refers to some proportion or index expressed relative to the mature state, in which the animal is in anatomical and/or compositional equilibrium. However indices of maturity referenced to body weight or composition (e.g. muscle:bone ratio) are problematic for assessing genotypic effects in modern prime lamb production, where terminal sires may be selected for specific compositional traits such as rapid muscle growth or low body fat. In such cases it may be preferable to define other indices such as skeletal maturity, by staging development in relation to longitudinal bone growth and mineral maturation and thus lead to a better understanding of musculoskeletal development in sheep.