Parity Cows Research Articles

Genetic relationships between claw health traits of dairy cows in different parities, lactation stages, and herds with different claw disorder frequencies

Claw disorders affect cow welfare and profitability of farms. Not only claw disorders but also the need for trimming, known as trimming status, has been shown to be heritable. Limited knowledge is available on whether claw health traits (claw disorders and trimming status) are genetically the same trait in different parities, lactation stages, or in herds with low or high frequency of claw disorders. The aim of the current study was to estimate frequencies, heritabilities, and genetic correlations of claw health traits measured in different parities (first vs. later parities), in different lactation stages (early vs. late lactation), and in herds with different frequencies of claw disorders (low vs. high frequency). Analyses revealed that heritabilities measured in different parities, lactation stages, or herds with different trait frequencies are similar for most claw health traits. Also, genetic correlations (rg) for most claw health traits were not found to be different from unity for traits in different parities, lactation stages, or herds with different trait frequencies. Sole hemorrhage and infectious lesions were genetically different traits in first or later parities (rg=0.29±0.31 and 0.66±0.15, respectively). White line separation and infectious lesions were genetically different in early and late lactation (rg=0.53±0.20 and 0.69±0.13, respectively), and sole ulcer was genetically different in herds with low or high frequency of sole ulcer (rg=0.75±0.14). In our analysis, we did not find convincing evidence to supports the use of multiple trait models for the analysis of claw health traits treating them as different traits in different parities, lactation stages, and herds with different claw disorder frequency.

Identification of genomic regions associated with female fertility in Danish Jersey using whole genome sequence data.

BackgroundFemale fertility is an important trait in cattle breeding programs. In the Nordic countries selection is based on a fertility index (FTI). The fertility index is a weighted combination of four female fertility traits estimated breeding values for number of inseminations per conception (AIS), 56-day non-return rate (NRR), number of days from first to last insemination (IFL), and number of days between calving and first insemination (ICF). The objective of this study was to identify associations between sequence variants and fertility traits in Jersey cattle based on 1,225 Jersey sires from Denmark with official breeding values for female fertility traits. The association analyses were carried out in two steps: first the cattle genome was scanned for quantitative trait loci using a sire model for FTI using imputed whole genome sequence variants; second the significant quantitative trait locus regions were re-analyzed using a linear mixed model (animal model) for both FTI and its component traits AIS, NRR, IFL and ICF. The underlying traits were analyzed separately for heifers (first parity cows) and cows (later parity cows) for AIS, NRR, and IFL.ResultsIn the first step 6 QTL were detected for FTI: one QTL on each of BTA7, BTA20, BTA23, BTA25, and two QTL on BTA9 (QTL9–1 and QTL9–2). In the second step, ICF showed association with the QTL regions on BTA7, QTL9–2 QTL2 on BTA9, and BTA25, AIS for cows on BTA20 and BTA23, AIS for heifers on QTL9–2 on BTA9, IFL for cows on BTA20, BTA23 and BTA25, IFL for heifers on BTA7 and QTL9-2 on BTA9, NRR for heifers on BTA7 and BTA23, and NRR for cows on BTA23.ConclusionThe genome wide association study presented here revealed 6 genomic regions associated with FTI. Screening these 6 QTL regions for the underlying female fertility traits revealed that different female fertility traits showed associations with different subsets of the individual FTI QTL peaks. The result of this study contributed to a better insight into the genetic control of FTI in the Danish Jersey.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0210-3) contains supplementary material, which is available to authorized users.

Genetic Relationship of Productive Life, Production and Type Traits of Korean Holsteins at Early Lactations.

The present study was performed to study the genetic relationship of productive life with production and type traits of Korean Holsteins at first three lactations. The data for the analysis from 56,054, 28,997, and 11,816 animals of first, second and third parity cows which were born from 2006 to 2011 were collected by Dairy Cattle Improvement Center, National Agricultural Co-operative Federation. Milk, protein and fat yields adjusted for 305 days and average somatic cell score considered as production traits and analyzed type traits were stature, strength, body depth, dairy form, rump angle, rump width, rear leg side view, foot angle, front attachment placement, rear attachment height, rear attachment width, udder cleft, udder depth, front teat placement and front teat length. A multi trait genetic analysis was performed using Wombat program with restricted maximum likelihood animal model composed of fixed effect of birth year, farm and the random effect of animal and random residual effect according to the traits. Heritability estimates of productive life were between 0.06 and 0.13. Genetic and phenotypic correlations between production and productive life traits ranged from 0.35 to 0.04 for milk, 0.16 to 0.05 for protein and 0.18 to 0.02 f 15-0034 (2nd) 150520 or fat. Somatic cells score showed a negative genetic and phenotypic correlation with productive life and also udder type traits, indicating that the selection for higher udder traits will likely to improve resistance to mastitis and persistence in the herd. Among all dairy form type traits, udder characters such as udder cleft showed a significant relationship with productive life. However, a specific change of heritabilities or correlations were not observed with the change of parity. Moreover, further studies are needed to further confirm the significance of the above traits and the effect of parity on above relationships in order to minimize both voluntary and involuntary culling rates while improving herd health and maintaining high yielding dairy cows.

Analysis of daily body weight of dairy cows in early lactation and associations withproductive and reproductive performance

The objective of this study was to describe daily body weight (BW) changes in the first 100 days of lactation in confined dairy cows and to associate BW loss with productive and reproductive performance. Data included 26,344 daily BW measurements of 372 Holsteins calving between June 2011 and June 2012 in a commercial herd in the South of Brazil. Cows were automatically weighed and were assigned according to parity. Individual measurements were smoothed using cubic splines, generating nadir BW, days to nadir BW and the BW loss (absolute and relative values). This approach used days in milk (DIM) as a single smoothing variable. Body weight at calving differed across parities: 570.5, 653.5, and 699.9 kg, for the 1st, 2nd and 3rd and subsequent parities, respectively. Body weight at nadir also differed across parities: 521.5, 608.8, and 647.3 kg, respectively. Mean days from calving BW to nadir BW and mean loss of BW (kg) from calving to nadir BW did not differ across parities, but relative BW change (kg/100 kg) was larger in animals in first parity (-8.4 kg/100 kg) than second parity (-6.6 kg/100 kg). However, cows in first parity had more chances for good reproduction than cows in third and subsequent parities (44.0% vs. 30.7%, respectively). There was no difference in the probability of adequate reproduction (pregnant until 180 DIM) among cows with low, medium, or high milk yield. Furthermore, cows with low and medium BW loss (below 60 kg of BW change) showed more likelihood to adequate reproduction than cows with high BW loss (above 60 kg of BW): 45.5 and 45.8% vs. 24.4%, respectively. Improvements in fertility of dairy cows should be achieved by minimizing body weight loss in early lactation.

Comparative changes in monthly blood urea nitrogen, total protein concentrations, and body condition scores of Nguni cows and heifers raised on sweetveld

The objective of this study was to determine the comparative changes in the monthly blood urea nitrogen (BUN) concentration, total protein (TP) concentration in blood serum and the body condition score of Nguni cows and heifers raised on sweetveld. Twenty-four clinically healthy animals in different parities, namely Parity 1 (n = 5), Parity 2 (n = 5), Parity 3-6 (n = 9) and heifers (n = 5), were randomly selected for the study. BUN concentration, TP concentration and body condition scores of the animals were measured over 12 months. Blood samples were collected from the coccygeal vein, while body condition score was assessed once a month during weighing. Cows in Parity 1 maintained a significantly higher body condition score (2.6 ± 0.01) than all the other animals in the trial. All the cows and heifers maintained higher levels of BUN concentration (7.5 ± 0.03 mmol/L) in November, while a lower value (1.9 ± 0.03 mmol/L) was recorded in January. The TP concentration was lowest in August at 70.8 ± 2.65 g/L, before it improved to reach a peak value of 92.3 ± 2.66 g/L in March. The Nguni cows and heifers had variations in the levels of BUN and TP concentrations in the various months while maintaining a steady body condition score throughout the trial.

Factors associated with the differential in actual gestational age and gestational age predicted from transrectal ultrasonography in pregnant dairy cows

The objective of the study was to determine (1) how gestational age predicted using transrectal ultrasonography related to actual gestational age derived as the number of days from the most recent artificial insemination date, (2) what factors, if any, were associated with the differential between the two measures, and (3) the association between this differential in gestational age and the likelihood of subsequent pregnancy loss, stillbirth, or calving dystocia. The data set contained 7340 ultrasound records from 6805 Holstein Friesian dairy cows in 175 herds. Ultrasonography assessment underestimated gestational age relative to days since last service by 0.51 days (standard error [SE]: 0.040), although the differential was less during embryonic development phase (i.e., ≤42 days of gestation; mean overestimation of 0.31 days) versus fetal development phase (i.e., >42 days of gestation; mean underestimation of 0.81 days). Predicted calving date calculated from ultrasonography was 1.41 days (SE: 0.040) later than the actual subsequent calving date and was, on average, 0.52 days later than predicted calving date, assuming a gestation length of 282 days. Parity of the dam (P < 0.05), stage of pregnancy (P < 0.001), and sex of the calf born (P < 0.001) were all associated with the differential in gestational age based on ultrasonography versus days since last service. No obvious trend among parities was evident in the difference between the methods in predicting gestational age. Ultrasonography underestimated gestational age by 0.83 (SE: 0.15) days in parity 5+ cows and underestimated gestational age by 0.41 (SE: 0.14) days in the first-parity cows. Relative to gestational age predicted from the most recent service, ultrasonography underestimated gestational age by 0.75 (SE: 0.13) days for heifer fetuses and underestimated gestational age by 0.36 (SE: 0.13) days for bull fetuses. The heritability of the differential in gestational age between the methods of prediction was low 0.05 (SE: 0.022), corroborating heritability estimates for most cow reproductive traits. Overestimation of gestational age using ultrasonography was associated with an increased likelihood of pregnancy loss (P < 0.001). Gender of calf born (P < 0.001), sire breed of calf (P < 0.001), and parity (P < 0.001) were all associated with gestation length. Gestation length was 1.27 days longer (SE: 0.01) for bull calves compared to heifer calves. Calves from beef sires had a longer gestation length than calves from dairy sires, and older parity cows had a longer gestation length than younger cows. The results highlight factors associated with differences in gestational age obtained from ultrasonography and insemination data and illustrate the value of ultrasonography for the prediction of calving date and pregnancy loss.

Biological efficiency profiles over the lactation period in multiparous high-producing dairy cows under divergent production systems

Abstract. The study examined variation in energetic-efficiency profiles among production systems and cow parities. Further, the correlation between cows' body condition score (BCS) and energetic efficiency over the lactation period was determined. Biological efficiency was defined using four measures of production efficiency and two measures of energetic efficiency. The following were measures of energetic efficiency: the net energy intake required to produce 1 kg milk solids (NEin / MS) and the proportion of net energy utilized for milk production after accounting for maintenance (NElact / (NEin- NEm)). Seven years of data were gathered from a total of 595 Holstein-Friesian cows in a long-term genetics × feeding–management interaction project. Two feeding regimes – High forage (HF) and Low forage (LF) – were applied to each of two genetic lines (Control (C) and Select (S)), giving four dairy production systems: Low Forage Control (LFC), Low Forage Select (LFS), High Forage Control (HFC) and High Forage Select (HFS). LFS was the most efficient system using all measures. Variation in the rate and scale of change at which the cows' energetic efficiency declined over lactation was significantly different (P &lt; 0.001) amongst different dairy production systems and parities. Loss of efficiency over the lactation period was lower in Select cows than in Control cows and increased with parity. The trajectory of energetic-efficiency profiles was influenced by cow genetic line, and yet the level of the efficiency profile was influenced by the feeding regime. There was a strong relationship between BCS and energetic efficiency. Continued in situ monitoring of cows' biological efficiency may enable optimal management of dairy systems.

Development of an index to rank dairy females on expected lifetime profit

The objective of this study was to develop an index to rank dairy females on expected profit for the remainder of their lifetime, taking cognizance of both additive and nonadditive genetic merit, permanent environmental effects, and current states of the animal including the most recent calving date and cow parity. The cow own worth (COW) index is intended to be used for culling the expected least profitable females in a herd, as well as inform purchase and pricing decisions for trading of females. The framework of the COW index consisted of the profit accruing from (1) the current lactation, (2) future lactations, and (3) net replacement cost differential. The COW index was generated from estimated performance values (sum of additive genetic merit, nonadditive genetic merit, and permanent environmental effects) of traits, their respective net margin values, and transition probability matrices for month of calving, survival, and somatic cell count; the transition matrices were to account for predicted change in a cow’s state in the future. Transition matrices were generated from 3,156,109 lactation records from the Irish national database between the years 2010 and 2013. Phenotypic performance records for 162,981 cows in the year 2012 were used to validate the COW index. Genetic and permanent environmental effects (where applicable) were available for these cows from the 2011 national genetic evaluations and used to calculate the COW index and their national breeding index values (includes only additive genetic effects). Cows were stratified per quartile within herd, based on their COW index value and national breeding index value. The correlation between individual animal COW index value and national breeding index value was 0.65. Month of calving of the cow in her current lactation explained 18% of the variation in the COW index, with the parity of the cow explaining an additional 3 percentage units of the variance in the COW index. Females ranking higher on the COW index yielded more milk and milk solids and calved earlier in the calving season than their lower ranking contemporaries. The difference in phenotypic performance between the best and worst quartiles was larger for cows ranked on COW index than cows ranked on the national breeding index. The COW index is useful to rank females before culling or purchasing decisions on expected profit and is complementary to the national breeding index, which identifies the most suitable females for breeding replacements.

Genetic and non-genetic analysis for milk production and reproductive traits in Holstein cattle in Egypt

This study was carried out to investigate genetic, non-genetic affecting factors and estimate genetic parameters for milk production and reproductive traits of Holstein cows via animal model. The data was obtained from a commercial farm (Safi Masr for Developing the Animal Resources), located in the Nile Delta, Dakahlia, Egypt. Data included 4791 records of 1797 cows, 794 dams and 67 sires that represented the period from 2002 to 2012. The means and coefficient of variability (CV%) of milk traits as total milk yield (TMY), 305 day milk yield (305-dMY), lactation period (LP) and dry period (DP) were 5787.8 kg (31.1%), 4695 kg (22.1%), 332 day (14.9%) and 72.3 day (27.7%), respectively. Also, the means (CV%) of reproductive traits as days open (DO) and age at first calving (AFC) were 157.9 day (22.6%) and 30.5 month (16.8%), respectively. Sire, dam, parity of cow, year and season of calving had significant effects on traits studied. Heritability estimated were 0.223, 0.184, 0.112, 0.118, 0.105 and 0.285 for TMY, 305-dMY, LP, DP, DO and AFC, respectively. Estimated r G and r P among milk production traits were positive but it takes negative trend with DP and DO. Moderate heritability estimates and positive genetic correlation for most of traits studied suggested that genetic improvement of these traits would be achieved via multi-trait selection.

Devising an indicator to detect mid-term abortions in dairy cattle: a first step towards syndromic surveillance of abortive diseases.

Bovine abortion surveillance is essential for human and animal health because it plays an important role in the early warning of several diseases. Due to the limited sensitivity of traditional surveillance systems, there is a growing interest for the development of syndromic surveillance. Our objective was to assess whether, routinely collected, artificial insemination (AI) data could be used, as part of a syndromic surveillance system, to devise an indicator of mid-term abortions in dairy cattle herds in France. A mid-term abortion incidence rate (MAIR) was computed as the ratio of the number of mid-term abortions to the number of female-weeks at risk. A mid-term abortion was defined as a return-to-service (i.e. a new AI) taking place 90 to 180 days after the previous AI. Weekly variations in the MAIR in heifers and parous cows were modeled with a time-dependent Poisson model at the département level (French administrative division) during the period of 2004 to 2010. The usefulness of monitoring this indicator to detect a disease-related increase in mid-term abortions was evaluated using data from the 2007–2008 episode of bluetongue serotype 8 (BT8) in France. An increase in the MAIR was identified in heifers and parous cows in 47% (n = 24) and 71% (n = 39) of the départements. On average, the weekly MAIR among heifers increased by 3.8% (min-max: 0.02–57.9%) when the mean number of BT8 cases that occurred in the previous 8 to 13 weeks increased by one. The weekly MAIR among parous cows increased by 1.4% (0.01–8.5%) when the mean number of BT8 cases occurring in the previous 6 to 12 weeks increased by one. These results underline the potential of the MAIR to identify an increase in mid-term abortions and suggest that it is a good candidate for the implementation of a syndromic surveillance system for bovine abortions.

Evaluation of on-farm tools for colostrum quality measurement

The objectives of this study were to determine the immunoglobulin G (IgG) content of colostrum on Alberta dairy farms and to determine which on-farm tool, the colostrometer or the Brix refractometer, was more highly correlated with IgG content as determined by radial immunodiffusion (RID). Colostrum samples (n=569) were collected between February and July 2012 from 13 commercial dairy farms in central Alberta, with herds ranging in size from 60 to 300 lactating cows. Immunoglobulin G content was determined directly by RID and indirectly by a colostrometer (specific gravity) and Brix refractometer (total solids). The Spearman correlation was used for the colostrometer and Brix refractometer data. According to RID analysis, 29.1% of the colostrum samples contained <50mg/mL IgG. Concentrations ranged from 8.3 to 128.6mg/mL IgG, with a median of 65.1mg/mL. Third or greater parity cows had higher colostral IgG content (69.5±1.98mg/mL) than second parity (59.80±2.06mg/mL) or first parity (62.2±1.73mg/mL) cows. The colostrometer data were more highly correlated with RID results (r=0.77) than were the Brix refractometer data (r=0.64). Specificity and sensitivity were determined for the colostrometer and Brix refractometer compared with a cut-point of 50mg/mL IgG as determined by RID. The highest combined value for sensitivity and specificity occurred at 80mg/mL for the colostrometer (84.1 and 77.0%, respectively) and 23% Brix (65.7 and 82.8%, respectively). This study indicates that although the colostrometer data are better correlated with true IgG values, the user-friendly Brix refractometer is a more specific tool to detect colostrum of adequate quality.

Genotype by environment interaction for livability of dairy calves from first parity cows

Death of calves around parturition is a matter of concern for dairy farmers. Relatively high stillbirth rates and unfavourable trends have been reported for Holstein heifers in the Netherlands and several other countries. In our study, we investigated herd differences, genetic parameters and genotype by environment interaction for heifer calf livability. A large dataset with data from calvings between 1993 and 2012 of Dutch dairy farms was used. There were considerable differences between herds in livability of calves from heifers, with averages ranging from 74% to 95%. Both herds with relatively high and low averages showed the same negative trend between 1993 and 2012, with largest declines in herds with the lowest averages. We found that heritability and genetic variation of first parity livability were substantially larger in herd environments where the likelihood of stillbirth was high v. environments where stillbirth was at a low level. The genetic correlations between herd environment levels were all very close to unity, indicating that ranking of sires was similar for all environments. However, for herds with a relatively high stillbirth incidence selecting sires with favourable breeding values is expected to be twice as profitable as in herds with a relatively low stillbirth incidence.

The effect of feed rations containing high moisture crimped corn ensiled with microbial inoculant or chemical additive on milk production and metabolism of dairy cows

The study evaluated the effects of crimped corn preserved either with organic acids or with a microbial inoculant on a range of metabolic and production indicators of dairy cows. Two hundred and sixty in-calf, second and third parity cows were selected into pairs on basis of age, parity, milk production in previous lactation, days in milk and body condition score with the greatest possible conformity within pairs. Cow pairs were assigned into a 2-period crossover experiment (2 × 45 days) and kept in separate groups within the same shed. Dietary treatments were TMR with crimped corn preserved with either organic acids (treatment K) or microbial inoculant (treatment B). Ten superbly matched cow-pairs were selected to form nucleus pairs for metabolic studies. The preservatives had no effect on the nutrient content of crimped corn. Crimped corn preserved with the microbial inoculant were found mouldy, predominantly with Mucor sp. at a number high enough to inhibit the growth of lactic acid bacteria, and had significantly higher pH and ammonium concentration compared to the chemical treatment. The milk yield of treatment K cows was significantly higher than that of treatment B cows with identical feed intake. Blood beta-hydroxy-butyrate concentration was lower and blood aspartate amino transferase activity higher with treatment K compared to treatment B. Results of this study suggest the superiority of total mixed rations containing chemically preserved crimped corn in terms of ammonia and microbiological indicators of crimped corn, significantly higher milk yield, and balanced energy metabolism.

Effects of Gonadotropin Releasing Hormone Analogue in Enhancements of Pregnancy in Repeat Breeding Dairy Cows in and around Mekelle, Tigray, Ethiopia

Clinical trial was carried out to evaluating the effects of GNRH analogue (buserelin acetate) along with AI in repeat breeding cross breed cows on enhancement of pregnancy. The trial was also aimed at evaluation of dose variation on conception rate. Sixty six cross breed dairy cattle which were apparently healthy, exhibits estrus regularly were selected and assigned randomly in to three equal groups(A,B and C); two treated groups and one control group. Group A (n=22) cattle were injected intramuscularly a 20 µg buserelin acetateat along with AI and Group B (n=22) cattle have injected with dose of 10µg Buserelin acetate. Group C (n=22) cattle were receive no treatment and considered as a control group, given a single service. These cows were examined for pregnancy after three months through rectal palpation. Additional history was taken from herd owners. The pregnancy rates recorded were 68%, 59% and 32% in the cattle grouped with A, B and C respectively. The conception rates of the treated groups exceeds control group by 36% and 27% respectively. Treated groups showed a significant statistical variation (P<0.05) as compared to control group. Dose variation between two treated groups has an effect on pregnancy rate with significant variation. Other observed finding was that treated first and second parity cows became more responsive to therapy than those with more than two parity with a significant variation (P<0.05). The study revealed that the use of GNRH analogue therapy at the time of AI can enhance pregnancy rate. This would be helpful and cost effective to minimize financial losses incurred from milk production loss, managmental and feed cost. This might be achieved through reducing calving interval and treating repeat breeding cases. The benefit cost ratio indicates that individual cow could benefit small holder farmer by 140 USD within a single month.

Influence of Replacement of Soya By-products with Soya Pulp on Milk Yield, Composition and Blood Parameters in Dairy Cows

The present experiment was conducted to evaluate the effect of replacing soya by-products with soya pulp at varying levels on milk yield, milk composition and blood parameters in dairy cows. Twenty cows of same parity, age and average milk yield (15–25 l/d) were distributed in four treatment groups (T1, T2, T3 and T4) of five animals each. Cows in all the groups were fed basal diet consisting of maize fodder, maize silage, concentrate mixture and wheat straw (NRC, 2001). The soya byproducts in the concentrate mixture were replaced with soya pulp at 0, 10, 20 and 30% levels in groups T1, T2, T3 and T4, respectively. All the diets were iso-nitrogenous. The animals of group T1 served as control. Significantly (P<0.05) higher DM and intake milk yield were observed in group T3 and lower (P<0.05) values were recorded in groups control and T2. There was no adverse effect of inclusion of soya pulp at varying levels on milk composition like fat, SNF and total solids which were similar among the groups. There was no deleterious effect of soya pulp on blood metabolites viz., glucose, total protein and blood urea nitrogen. It was concluded that soya pulp can replace other soya byproducts viz., soya bean meal and full-fat soya in the concentrate mixture up to 30% without any adverse effect on DM intake, milk yield and milk composition in dairy cows.

Behavioural Responses of Primiparous and Multiparous Dairy Cows to The Milking Process over an Entire Lactation

Abstract The objective of this study was to examine associations between milking temperament, parity and milk production traits in primiparous and multiparous dairy cows. Twenty-one primiparous and nineteen multiparous Holstein Friesian cows were involved in the investigation on a Hungarian dairy farm. Cows’ stepping behaviour, milk yield and average milking speed were recorded once a month over an entire lactation, during morning milking. Milking temperament was scored by direct human observation on a 5-point-scale (1=very nervous, 5=very quiet) during udder preparation and milking. Multiparous cows showed a little more excitable behaviour at milking than during udder preparation (Mann-Whitney U=14165.00, P=0.032), and they were calmer at premilking preparation than primiparous cows (Mann-Whitney U=14046.00, P=0.001). Milking temperament of multiparous cows during udder preparation was associated with milking speed: nervous cows let down their milk slower (F=9.102, df= 1, P=0.003). Further experiments are needed to repeat the milking temperament test along with sensors measuring heart rate variability of cows in order to better understand the milking behaviour of cows.

Effect of inbreeding and some other factors on lactation length in Malvi cows

The data for the present investigation pertained to 1647 observations of lactation length (LL) on Malvi cattle maintained at Govt. Cattle Breeding Farm, Agar, District Shajapur (M.P.), covering a period of 48 years from 1962 to 2009. The least squares analysis of variance revealed the mean lactation length in these cows to be 263.85±6.95 days and the trait was significantly affected by sire (P< 0.01), period of calving (P< 0.01), season of calving (P< 0.01) and parity of the cow (P< 0.01). Although, inbred cows had lower lactation length as compared to non-inbred cows, the effect of inbreeding was not significant. Heritability estimate for lactation length in the herd was obtained as 0.08±0.11. It was concluded that to improve the lactation length in this herd, ameliorative managerial practices should be adopted along with avoidance of inbreeding.

Effect of Feeding Formaldehyde Treated Rapeseed and Cottonseed Cakes on Milk Yield and Composition at Various Stages of Lactation and Parity in Jersey Cows

The aim of this study was to document the response of lactating Jersey cows to feeding of formaldehyde treated oil cakes of rapeseed and cottonseed on milk yield and composition at various stages of lactation and parity. Formaldehyde treatment of oil cakes was performed at 1% of crude protein, and these treated cakes were used in preparing treatment concentrate mixture. The experiment was carried out for 40 days using 27 lactating Jersey cows differing in parity 1–3, 4–6 and ≥7 with different stages of lactation i.e. early (1–3 m), mid (4–6 m) and late (7–9 m) in each lactation groups. The animals were grouped into Control and Treatment. For first 10 days, cows of Control group were offered with a control concentrate and thereafter same animals were grouped as Treatment group and fed the same concentrate having both the protein meals treated with formaldehyde, along with ad libitum access to barley green fodder and wheat straw. The milk yield and its component yield were decreased linearly as lactation advanced and the differences were significant (P<0.05) between early and late lactation. The highest increment (P<0.05) in milk yield was noted in early lactation (0.69 kg/d) and least during late lactation (0.56 kg/d). Milk SNF yield was improved (P<0.05) up to the tune of 40 g/d in mid lactation cows only. With respect to parity, the highest (P<0.05) milk yield was observed in 1st-3rd parity and lowest after 7th parity, while milk fat% followed the reverse trend upon feeding formaldehyde treated oil cakes, while other parameters like fat and SNF percentage did not differ due to treatment. Furthermore, milk fat yield was increased (P<0.05) to the extent of 50 g/d and 20 g/d in 1st-3rd and above 7th parity cows, respectively. It was concluded that feeding of concentrate mixture containing formaldehyde treated oil cakes (rapeseed and cottonseed) economically improved yield of milk and milk components. Furthermore, the treatment effect was more pronounced during early lactation and in lower (1–3) parity Jersey cows.

Short communication: Economics of sex-biased milk production

In a recent data study using 2.4 million lactations of 1.5 million cows, it was reported that gestation of a female calf in the first parity increases cumulative milk production by approximately 445kg over the first 2 lactations. The reported effect in this study is large and remarkable because it has not been found before. To our knowledge, the economic implications of this or any other sex bias have not been studied. The objective of the current study was to quantify the reported influence of fetal sex across lactations by using a simulation model of a dairy herd including youngstock. Two scenarios were evaluated and compared with a scenario in which cows and heifers were exclusively bred with conventional (nonsexed) semen. In the first scenario, sexed semen was used moderately—on 30% of all heifers and 30% of the first parity cows. A second scenario was studied in which sexed semen was used intensively—on all heifers and 50% of the first-parity cows. The simulated proportion of cows giving birth to 2 consecutive heifers increased from 23% when using exclusively conventional semen up to 31 and 48% when using sexed semen moderately and intensively, respectively. The proportion of cows having 2 consecutive bulls decreased from 27% (conventional semen only) to 20 and 8% when using sexed semen moderately and intensively, respectively. When incorporating the sex bias in the simulation model, the simulated milk yield in the scenario in which sexed semen was used moderately increased by 48kg of energy-corrected milk (ECM) per cow/yr, compared with only 36kg of ECM when not incorporating the sex bias in the model. For the scenario in which sexed semen was used intensively, milk yield increased by 66 and 99kg of ECM when excluding and including the sex bias, respectively. The economic implications of the assumed sex bias were €4.0 and €9.9 per cow/yr, in the scenarios in which sexed semen was used moderately and intensively, respectively.

Economics of milk yield losses in one dairy farm in Macedonia associated with clinical mastitis

Mastitis remains one of the major disease in dairy herds, causing profound economic losses to the entire milk production chain due to changes in the milk quality and milk yield. A one year cross-sectional longitudinal survey was carried out to evaluate milk yield losses associated with occurrence of clinical mastitis cases in one dairy herd. Cows that had clinical mastitis and clinically healthy cows during lactation were included in the study. The traits analyzed were the average of the monthly test day milk yields, cow parities and days in lactation while first case of clinical mastitis was occurred. For these purpose there were recorded data for monthly test day milk yield of the cows at the 2nd, the 3rd and the 4th monthly test day (TD). TDs were chosen according to the average number of days in lactation to diagnose the first case of clinical mastitis. According these criteria, the 2nd and the 3rd TD were made before the diagnosis of the first lactation case of clinical mastitis, while the 4th TD was made after the diagnosis. Monthly test day milk yields were treated as repeated measurement within an animal in General Linear Model (GLM). Statistical model included fixed effect of cow parity and covariance of days in lactation when the first case of clinical mastitis was occurred. Estimated lactation incidence risk (LIR) for CM in observed population of dairy cows was 21.49%. Regardless parities, the first case of clinical mastitis in dairy herd occurred on the average 108.09±83.182 days in lactation. The LIR tended to significantly increased (p&lt;0.001) with increasing the cow parity, as risk factor for occurrence of clinical mastitis. Before contracting the disease, cows with clinical mastitis yielded more milk than did healthy cows. Mastitis clearly affected the milk yield and the difference between the milk yield of the healthy cows and the cows after clinical mastitis was statistically significant. There was a significant decrease in the milk yield before and after the diagnosis of clinical mastitis case (p&lt;0.001). The estimated daily milk yield losses per cow suffered from case of clinical mastitis, between the 3rd TD and the 4th TD, range from 0.9 kg to 26.0 kg, or average 9.6 kg/day. According this, the monthly milk yield losses per mastitic cow, between the 3rd TD and the 4th TD, were 288 kg. If we take in consideration the price of one kg milk of 0.32 euro, than the total daily economic losses per mastitic cow will be around 3 euro’s and monthly losses per cow will be around 92 euro. Regardless of the time of occurrence during the lactation, mastitis had a long-lasting effect on milk yield; cows with clinical mastitis did not reach their premastitis milk yields during the remainder of the lactation after onset of the disease. The daily milk yield must be taken in consideration for more rapid economic analysis of milk losses associated with occurrence of clinical mastitis in dairy herds.