Persistency Of Milk Production Research Articles

Genetic analysis of rumination time based on an analysis of 77,697 Israeli dairy cows

Reduction of methane emission may become necessary for sustainable milk production. Several studies indicate a relationship between rumination time and the level of methane emission. The objectives of the current study were to estimate environmental factors affecting daily rumination time in high yielding dairy cattle, genetic parameters for rumination time across parities, environmental and genetic correlations between rumination time and economic traits and to predict the consequence of inclusion of this trait in the Israeli breeding index. The data included more than 30 million daily records from 77,697 Israeli Holstein cows for rumination time and milk production. A lactation measure of daily rumination time per cow was computed as the mean of the residuals from a linear model analysis with rumination time as the dependent variable. The independent variables were parity and the square root, linear, quadradic and inverse of days in milk by parity. Because of the shape of the lactation curve for rumination time, separate linear model analyses were performed for records up to 40 DIM and records with >40 DIM. The phenotypic correlation between first and second parity lactations for rumination time was nearly 0.8, and close to 0.7 for milk. The heritability of lactation rumination time was close to 0.44 for parities 1-3. Heritability for milk production decreased from 0.5 in first parity to 0.3 in third parity. For both traits genetic correlations among parities were all >0.9. Thus, for routine genetic analysis of rumination time, records in the different parities can be considered the same trait. The genetic correlation between rumination time and milk on first parity was 0.25 and increased slightly with increase in parity. Genetic correlations between rumination time, based on the first 40 d in milk, were economically unfavorable with retained placenta but economically favorable with metritis, ketosis and displaced abdomen. Genetic correlations between rumination time and the 9 traits included in the Israeli breeding index; milk, fat, and protein production, SCS, female fertility, herd-life, milk production persistency, calving ease, and calf mortality; were all economically favorable, except for the correlation of 0.17 with SCS. With the current index, daily rumination time with a current mean of 536 min and standard deviation of 90 min is expected to increase by 11 min per day after 10 years of selection. Inclusion of this trait with a positive index weight equivalent to 10% of the index should increase rumination time by 19 min. All changes in expected gains due to inclusion of rumination time in the index were economically positive, except for fat and SCS. Inclusion of rumination time in the index should result in 1 kg less gain in fat, a miniscule gain of 0.03 for SCS; and gains of 1.5 kg protein, 0.3% female fertility and 5 d herd-life. Even though the case for a genetic correlation between rumination time and methane emission is still weak, inclusion of this trait in the commercial index may be justified, considering that equipment is now commercially available for routine recording at reasonable cost.

Estimation and comparison of different lactation persistency methods in Tharparkar cattle

The present study was undertaken to estimate the various measures of lactation persistency and to estimate effect of various non-genetic factors affecting the persistency of milk production and comparison of different persistency indices using standard error as percentage of mean in Tharparkar cattle. Total 322 lactation records of 138 Tharparkar cattle were collected from Animal Genetics and Breeding Division of National Dairy and Research Institute, Karnal from 1996 to 2018 for the estimation of lactation persistency. Lactation persistency was estimated using Ratio method (P1), Prasad method (P2), Solkner and Fuchs variation method in 200 days (P3) and 305 days (P4).The least squares of means for persistency of milk yield were 149.6 ± 3.07, 0.53 ± 0.007, 1.83 ± 0.05 and 2.28 ± 0.07 in P1, P2, P3 and P4 respectively in Tharparkar cattle. Based on standard error as percentage of mean, the best method was Prasad method (1.1%). The highest values of least squares means were found for first calvers in P1 but in P3 and P4 fourth calvers were more persistent. The cows calved during rainy season were more persistent as estimated by P1 and P2 but based on P3 and P4 winter calvers were more persistent. There was a highly significant (P<0.05) positive correlation of total milk yield with all the method of persistency indices.

Comparative Study of Automation and Conventional System on Production Performance in Dairy Farms

Background: The Indian dairy industry has progress consistently ever since the White revolution of the 1970s, making India, the world’s largest and fastest producer of milk with 17 per cent global share. The Indian dairy market is expected to double within the next 10 years, primarily driven by over 16-20 per cent growth in value added dairy segment. To catch this high growth potential and to meet the rising demand, a sustainable and strong dairy production system will be critical. Methods: A study was conducted between December 2018 and February 2019 at four different dairy farms. The farms were identified based on rearing systems practiced. The farms were divided into two groups where the first one (n=10 dairy cattle) utilized automatic rearing systems (the ARS farms), while the second group (n=10) had conventional rearing systems (the CRS farms).Result: Based on the results, the effect of different rearing systems on the average lactation yield in the fourth lactation was significantly higher (P≤0.05) in automatic rearing system. The lactation yield of both the treatment groups was not significant till third lactation. There was no significant difference observed in persistency of milk production in both the rearing systems. Reproductive performance of the ARS houses had better age at first calving and service period as compared to conventional house type with significant difference. By using an ARS it is possible to save time and achieve greater flexibility. The experiment indicates less man power minutes required for routine daily work like feeding, watering and milking in automatic rearing system as compare to conventional rearing system. A significant (P≤0.01) reduction in working time by comparison with a different feeding, watering and management system however can only be expected in the case of sizeable herds. It appears that not much time can be saved with herds numbering 60 animals, but flexibility for the farm manager becomes significantly greater. In view of the relatively high amount invested in ARS, the profitability of such a system must be decided on a farm by farm basis. In principle an ARS can be a good opportunity for optimizing working time and workload in dairy farming.

Metabolic and hormonal control of energy utilization and partitioning from early to mid lactation in Sarda ewes and Saanen goats

In a recent study, we observed that starch-rich diets used in mid lactation induced lower milk production persistency and higher body fat accumulation in dairy ewes compared with dairy goats. Because these species differences could be linked to hormonal mechanisms that drive energy partitioning, in the same experiment, we explored the evolution of metabolic and hormonal status during lactation to test this hypothesis. Twenty mature Sarda dairy ewes and 20 mature Saanen goats [15-134 ± 11 d in milk (DIM), mean ± SD] were compared simultaneously. In early lactation, each species was allocated to one dietary treatment: high-starch diet [HS: 20.4% starch, on dry matter (DM) basis], whereas from 92 ± 11 DIM, each species was allocated to 1 of 2 dietary treatments: HS (20.0% starch, on DM basis) and low-starch (LS: 7.8% starch, on DM basis) diets. Blood samples were collected in the morning to analyze glucose, nonesterified fatty acids (NEFA), growth hormone (GH), insulin, and insulin-like growth factor I (IGF-I). Data were analyzed using the PROC MIXED procedure of SAS with repeated measurements (SAS Version 9.0). The HS and LS diets applied in mid lactation did not affect metabolic status of the animal within species; thus, only a comparison between species was carried out. From early to mid lactation, plasma glucose concentration was higher in ewes than in goats (54.57 vs. 48.35 ± 1.18 mg/dL), whereas plasma NEFA concentration was greater in goats than in ewes (0.31 vs. 0.25 ± 0.03 mmol/L). Goats had higher plasma GH concentration and lower plasma insulin content than ewes (4.78 vs. 1.31 ng/mL ± 0.47; 0.11 vs. 0.26 μg/L ± 0.02). Plasma IGF-I concentration did not vary between species. The comparison of metabolic and hormonal status of lactating Sarda dairy ewes and Saanen goats, carried out by studying simultaneously the 2 species in the same stage of lactation and experimental conditions, suggests that the higher insulin and glucose concentration observed in Sarda ewes explains why they partitioned more energy toward body reserves than to the mammary gland, especially in mid lactation. This can justify the negative effect of high-starch diets in mid-lactating Sarda ewes. Conversely, the highest GH and NEFA concentration observed in Saanen goats explain why they partitioned more energy of starch diets toward the mammary gland than to body reserves and justify the positive effect of high-starch diet in mid lactation. Together, these different responses contribute to explain why specialized dairy goats, such as the Saanen breed, have a higher milk production persistency than specialized dairy sheep breeds, such as the Sarda.

Association between age at first calving and lactation performance, lactation curve, calving interval, calf birth weight, and dystocia in Holstein dairy cows.

In the present study, records on 115,291 heifers distributed in 113 herds were used to investigate the association between age at the first calving (AFC) and lactation performance, lactation curve, the length of the first calving interval (CI), calf birth weight (CBW), and the incidence of dystocia in Holstein heifers in Iran. Based on the AFC, the heifers were classified into eight classes: AFC of 541 to 690 d, 691 to 720 d, 721 to 750 d, 751 to 780 d, 781 to 810 d, 811 to 840 d, 841 to 900 d, and 901 to 1200 d (AFC1 to AFC8, respectively). Multiple regression mixed models were used to investigate the association between AFC and lactation curve parameters, partial and 305-d lactation performance, 100- and 305-d SCS, and the length of the first calving (CI) interval. The mean (SD) and median AFC across all heifers was 760.2 (74.01) and 750 d, respectively. Of 115,291 heifers included, 28,192 and 7,602 heifers were, respectively, ≤ 720 and > 900 d when calving for the first time. More than 44% of the heifers were at 691 to 750 d (23 to 25 months) of age when calving for the first time. An increased AFC was associated with increased partial and 305-d lactation performance, 100- and 305-d SCS, initial milk yield, milk production at the peak of lactation, upward and downward slopes of the lactation curve. The 305-d fat percentage was associated with AFC; however, there was no association between AFC and 305-d protein percentage. An increased AFC was also associated with decreased milk production persistency, delayed peak time, longer CI, and higher calf birth weight. Compared to heifers calving for the first time between 691 to 780 d (23 to 26 months) of age, both increasing and decreasing AFC were associated with increased risk of dystocia. Controlling AFC is an important management factor in achieving a lower risk of dystocia, higher lactation performance, lower SCS, and shorter length of the calving interval.

Influence of levels of supplementary concentrate mixture on lactation performance of Red Sokoto does and the pre-weaning growth rate of their kids

Twenty pregnant Red Sokoto goats (liveweight, 28 ± 1.30 kg) were used in a completely randomized design to determine the effect of varying levels of concentrate on lactation performance. The concentrate, which contained 4% palm oil, was fed at levels of 1.0, 1.5, 2.0 and 2.5% of body weight of the does in addition to a basal diet of Digitaria smutsii hay offered ad libitum. The corresponding dietary treatments were designated as 1.0%C, 1.5%C, 2.0%C and 2.5%C, respectively. The goats were balanced for parity and randomly allocated to give five animals per treatment, and stall-fed individually.The intake of dry matter and daily milk production linearly and quadratically increased (P<0.05) to the levels of concentrate supplementation. Increase in level of concentrate mixture supplementation affected (P<0.05) milk fat content and milk fat yield, but not other milk constituents. Persistency of milk production was numerically higher at higher levels of concentrate supplementation. Whereas 1.0%C, 1.5%C and 2.0%C could not prevent weight loss in the does, the 2.5%C significantly (P<0.05) promoted average daily gain (11.11 g/head/day) during lactation. The dam milk yield significantly (P<0.01) accounted for 61% of variation in kids pre-weaning average daily gain (ADG). It is concluded that concentrate mixture containing 4% palm oil can be fed at 2.5% of body weight without adverse effect on total dry matter intake, while enhancing postpartum weight gains, higher milk yield, persistency of milk production, pre-weaning growth of kids in Red Sokoto goats.

Effect of Body Condition Score (BCS) on Production Performance of Sahiwal Cattle

The present investigation was carried out with the total of 18 Sahiwal cattle of 1st to 4th parity were selected for the study and distributed into three different groups based on their pre calving BCS (before 15 days of expected date of calving) namely G1 (2.50–3.00), G2 (3.25–3.75) and G3 (4.00 and above) with six animals in each group. The average fortnight milk yield increased up to 60th day and thereafter declined up to 90th day in G1, G2 and G3 group of animals, which was significant (p<0.05) up to 75th day. G3 group animals had highest average fortnightly cumulative Milk yield (Kg) in entire study period. Highest 305 days predicted lactation milk yield (2462.66 Kg/lactation) and average peak yield (16.50 Kg/animal) was obtained in G3 group animals and the lowest predicted lactation milk yield (1870.68 Kg/lactation). The 305 days predicted lactation milk yield in G2 group animals was 2356.75 Kg/lactation and average peak yield was 14.90 Kg/animal. The G3 group animals also attained their peak yield in 46 days compared to G2 and G1 group animals with 51 and 54 days, respectively. The persistency of milk production was highest in G2 group animals with 65.63% followed by G3 and G1 group animals. The studied revealed that BCS had a significant (P<0.05) effect on post-partum estrus and service period in experimental animals.

Factors affecting the persistency of milk production in Jersey crossbred cattle

Factors affecting the persistency of milk production in Jersey crossbred cattle

Genetic analysis of persistency in HF crossbred cattle at an organized farm of northern India.

The present study was undertaken to estimate effect of various genetic and non-genetic factors on persistency of milk production and to identify the most appropriate persistency method that fits best in our environment. In the present study, effects of different non-genetic factors, viz. year, season, days to attain peak yield, and genetic group based on the level of exotic inheritance on persistency of milk yield in crossbred cattle were studied. Data comprised of 686 first lactation daily milk yield records of crossbred cattle that were maintained at GADVASU dairy farm over a period of 25years from 1991 to 2015 were utilized to calculate persistency coefficients by four methods, viz., Ludwick and Peterson method (P1), Mahadevan method (P2), ratio method (P3), and Prasad et al. method (P4). Overall least squares means for persistency by Ludwick and Peterson method (P1), Mahadevan method (P2), ratio method (P3), and Prasad et al. method (P4) were 0.896 ± 0.096, 1.385 ± 0.224, 187.207 ± 26.398, and 0.621 ± 0.098, respectively. Effect of sires was significant (P < 0.05) on P2 and P4 methods. Effect of genetic group on all four methods was non-significant. Period of calving had significant (P < 0.01) effect on persistency of milk yield (P2, P3, and P4 methods). Effect of season of calving on persistency of milk yield was found to be significant in all estimates obtained by the four methods. Summer and autumn calvers were most persistent whereas spring and winter calvers were least persistent for (P2, P3, and P4 methods). Persistency of milk yield was significantly (P < 0.05) affected by days to attain peak yield in P1 and P2 methods. Maximum persistency was obtained in animals attaining peak at 41-57days of lactation and minimum in < 41days for Mahadevan method and ratio method. The highest heritability of persistency and minimum value of standard error was estimated as 0.275 ± 0.11 for the Mahadevan method followed by the Prasad method (0.197 ± 0.10) by half sib correlation method. The maximum coefficient of variation which indicates available variability was estimated as 20.788% for persistency by the Mahadevan method followed by 18.969% for the Prasad method. The highest correlation was also observed between P1 and P3 methods by Spearman's and Pearson's correlation for least squares breeding value of the sires. On the basis of heritability, standard error of heritability, and coefficient of variation, it can be concluded that the Mahadevan method followed by the Prasad method suits best to our environment for animals in first lactation as well as they can be utilized for effective selection for higher persistency in crossbred animals of Punjab.

Milk production and milk composition of the Boutsko bred of ewes in Epirus

A flock of 244 hill sheep of the indigenous Boutsko breed of Epirus (NW of Greece), 1-6 years old, reared under a transhumance system was used to study their milk productivity for a period of 14 months (March - June of next year). In addition three groups of ewes, aged 3 to 4 years (group A with 10 ewes suckling a single male lamb, group Βwith 10 ewes suckling a single female lamb and group C with 10 ewes suckling twin lambs) were kept under the same conditions of nutrition and management with the rest of the above flock. They were studied for a 26-week lactation period (4-week suckling period. 22-week milking period) to assess the effect of sex and number of lambs suckled on milk yield, milk composition and body reserves. The results of the study have been summarized as follows: 1) Lactation period (suckling period=4 weeks, milking period=32 weeks) was very long (36 weeks). Throughout milking period milk production of the ewes was 93.7 Kg. Of this 82.3% was produced during the winter period and 17.7% during the summer period. Persistency of milk production was low. One month after weaning of lambs the milk yield of ewes was reduced by 49% and 44% of the level at weaning for singlesuckled and twin-suckled ewes, respectively. 2) Throughout lactation, milk yield and milk composition were not affected by sex of lambs suckled. However, milk yield of ewes was affected by the number of suckled lambs; twin-suckled ewes produced more milk during the suckling period ( + 15.7%, Ρ &lt; 0.05) and milking period (+21.8%, Ρ &lt; 0.05) than those of single-suckled ewes. Fat, protein and dry matter concentration of milk was lower (P&lt;0.05) in twin-suckled ewes than in single-suckled ewes. Concentration of all milk constituents was affected by stage of lactation (P&lt;0.05).

The functional effects and mechanisms by which fibroblast growth factor 2 (FGF2) controls bovine mammary epithelial cells: Implications for the development and functionality of the bovine mammary gland.

Fibroblast growth factor (FGF) signaling plays essential roles in tissue development and homeostasis. Accumulating evidence reveals that fibroblast growth factor 2 (FGF2) regulates ductal elongation, which requires cell proliferation and epithelial expansion in the mammary gland. However, the function and mechanisms by which FGF2 controls functionality of epithelial cells is less well defined. Here, we demonstrate the functional effects of FGF2 on bovine mammary epithelial (MAC-T) cells and the intracellular signaling mechanisms for these FGF2-induced actions. The current results show that treatment of MAC-T cells with a recombinant FGF2 induced cell proliferation and cell-cycle progression with increased expression of proliferating cell nuclear antigen and cyclin D1. Moreover, FGF2 increased phosphorylation of serine/threonine protein kinase (protein kinase B [AKT]), extracellular signal-regulated kinases 1 and 2 (ERK1/2), Jun N-terminal kinase (JNK), 70 kDa ribosomal S6 kinase (P70S6K), 90 kDa ribosomal S6 kinase (P90S6K), ribosomal protein S6 (S6), and cyclin D1 proteins. These FGF2-induced activations of signaling pathway proteins were inhibited by blocking AKT, ERK1/2, or JNK phosphorylation. The effect of FGF2 to stimulate MAC-T cell proliferation was mediated by activation of FGF receptors (FGFR) and AKT, ERK1/2, and JNK mitogen-activated protein kinase pathways in response to FGF2 stimulation. Furthermore, expression and activation of endoplasmic reticulum (ER) stress-related factors and ER stress-induced MAC-T cell death was reduced by FGF2. Together, these results suggest that the FGF2-FGFR-intracellular signaling cascades may contribute to maintaining and/or increasing numbers of mammary epithelial cells by inducing proliferation of mammary epithelial cells and by protecting cells from ER stress responses. Therefore, this study provides evidence that FGF2 signaling is a positive factor for mammary gland remodeling and for increasing persistency of milk production.

Comparison of pure Holsteins to crossbred Holsteins with Norwegian Red cattle in first and second generations

A total of 1922 first generation crossbred cows born between 2005 and 2012 produced by inseminating purebred Israeli Holstein cows with Norwegian Red semen, and 7487 purebred Israeli Holstein cows of the same age in the same 50 herds were analyzed for production, calving traits, fertility, calving diseases, body condition score, abortion rate and survival under intensive commercial management conditions. Holstein cows were higher than crossbreds for 305-day milk, fat and protein production. Differences were 764, 1244, 1231 for kg milk; 23.4, 37.4, 35.6 for kg fat, and 16.7, 29.8, 29.8 for kg protein; for parities 1 through 3. Differences for fat concentration were not significant; while crossbred cows were higher for protein concentration by 0.06% to 0.08%. Differences for somatic cells counts were not significant. Milk production persistency was higher for Holstein cows by 5, 8.3 and 8% in parities 1 through 3. Crossbred cows were higher for conception status by 3.1, 3.6 and 4.7% in parities 1 through 3. Rates of metritis for Holsteins were higher than the crossbred cows by 7.8, 4.6 and 3.4% in parities 1 to 3. Differences for incidence of abortion, dystocia, ketosis and milk fever were not significant. Holstein cows were lower than crossbred cows for body condition score for all three parities, with differences of 0.2 to 0.4 units. Contrary to comparisons in other countries, herd-life was higher for Holsteins by 79 days. A total of 6321 Holstein cows born between 2007 and 2011 were higher than 765 progeny of crossbred cows backcrossed to Israeli Holsteins of the same ages for milk, fat and protein production. Differences were 279, 537, 542 kg milk; 10.5, 17.7, 17.0 kg fat and 6.2, 12.9, 13.2 kg protein for parities 1 through 3. Differences for fat concentration were not significant, while backcross cows were higher for protein percentage by 0.02% to 0.04%. The differences for somatic cell score, conception rate, and calving diseases other than metritis, were not significant. Holstein cows were lower than backcross cows by 1.5% to 2.5% for conception status in parities 1 to 3 and lower for body condition score for parities 1 and 2, with differences in the range of 0.06 to 0.09 units. Culling rates were higher, and herd-life lower for the crossbred cows. The gains obtained in secondary traits for crossbred cows did not compensate for the major reduction in production.

Digestibility, Milk Production, and Udder Health of Etawah Goats Fed with Fermented Coffee Husk

This study was carried out to assess the utilization of coffee husk fermented by Pleurotus ostreatus as feed supplement by measuring the digestibility, milk production and udder health of Etawah goats suffered from subclinical mastitis (+1). There were three experimental diets consisted of T0 (control diet/basal diet without fermented coffee husk), T1 (basal diet with 6% fermented coffee husk) and T2 (basal diet with 6% fermented coffee husk soaked in crude palm oil for an hour before using). Basal diet consisted of napier grass (60%) and concentrate (40%). The results showed that supplementation of lactating Etawah does with fermented coffee husk did not affect the palatability of the diets, but increased the protein and crude fiber consumption (P<0.05). There was no significant effect on nutrient digestibility and milk production while milk composition (protein, fat, total solid) increased in supplemented groups (P<0.05). The persistency of milk production and the somatic cells count were not different. There was an improvement of somatic cells count on supplemented groups. In conclusion, fermented coffee husk could be used as feed supplement without any negative effects on digestibility and milk production. The positive effects to udder health could be expected from including fermented coffee husk in diets. Key words: coffee husk, Etawah goat, fermented, performance, supplement

Utilization of Bioslurry on Maize Hydroponic Fodder as a Corn Silage Supplement on Nutrient Digestibility and Milk Production of Dairy Cows

The research was conducted to study the effect of addition of 7% DM maize hydroponic fodder (MHF) in corn silage on digestibility and milk production of dairy cows. The experiment used a completely randomized block design with two treatments, and four replications. The treatments were dairy cows fed with grass (Pennisetum purpureum), corn silage, and concentrate (R0), and dairy cows fed with grass (P. purpureum), corn silage, concentrate, and MHF (R1). This research used eight dairy cows with initial average milk production of 13.01±2.96 L/d. MHF was produced in a hydroponic system using bioslurry as a fertilizer enriched with mineral fertilizer. Variables observed were chemical composition of bioslurry, nutrient content of ration, daily dry matter intake, nutrient digestibility, Total Digestible Nutrient (TDN), and Digestible Energy (DE). Data were analyzed with ANOVA, except for milk production using ANCOVA. Supplementation of MHF resulted a higher total dry matter intake on R1 than R0 (P<0.05), 12.99±0.063 kg/head/d, and 11.98±0.295 kg/head/d, respectively. The digestibility of nutrients were not affected by the addition of MHF. Energy consumption in R1 was also higher than R0 (P<0.05), 49.95±0.36 Mkal/kg, and 46.11±0.54 Mkal/kg, respectively. Supplementation of MHF also increased nitrogen consumption, R1 was higher than R0 (P<0.05), 318.3±2.3 g/head/d, and 295.9±3.5 g/head/d, respectively, and could maintain the persistency of milk production at the end of lactation. It can be concluded that supplementation of MHF in corn silage can increase dry matter intake, energy consumption, and nitrogen consumption, also can maintain nutrient digestibility and maintain persistency of milk production during late lactation of dairy cows.Key words: bioslurry, dairy cow, greenhouse fodder, nutrient digestibility

When Should We Stop Breeding Dairy Cows?

The decision of when to start and when to stop breeding cows during a lactation is often a challenging one for dairy producers. This 3-page fact sheet presents practical rules on how to determine when to stop breeding Holstein dairy cows based on persistency of milk production and break-even point for milk production. Written by Klibs N. Galvão and Albert De Vries, and published by the UF Department of Veterinary Medicine-Large Animal Clinical Sciences, July 2014.&#x0D; VM202/VM202: When Should We Stop Breeding Dairy Cows? (ufl.edu)

Signatures of contemporary selection in the Israeli Holstein dairy cattle

Strong selection in the Israeli Holstein dairy cattle population over the last three decades should have left clear signatures of selection. Two experimental approaches were applied to detect evidence of contemporary selection based on the 54K BeadChip genotypes of ~1000 Israeli Holstein bulls: (i) the long-range haplotype test, which searches for structural evidence resulting from selective sweep, and (ii) direct analysis of the changes in haplotypes frequencies over time combined with linkage disequilibrium blocks haplotype-based association analysis. Ten traits were analyzed: the PD07 Israeli selection index, milk, milk fat, % fat, milk protein, % protein, somatic cell score, female fertility, milk production persistency and herd life. The long-range haplotype test detected ~15% of the 3288 haplotypes that showed significant positive frequency trends (P < 0.05) and was significantly correlated with the substitution effects of the haplotypes and the selection intensities for the different traits. Thirty signatures of recent selection, which correspond to both approaches and affect the Israeli PD07 selection index, were identified on 17 of the 29 autosomes. The second experimental approach also was used to estimate the selection intensity of the different traits. The correlation between the selection intensities for the traits analyzed, derived from changes in haplotype frequencies in the population of bulls, and those derived from trait-based analysis of the cow population was 0.93 over all traits. Thus, the changes in haplotypes frequencies in the bulls' population accurately estimate genetic trends in the general cow population and can be used to detect signatures of recent selection.

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

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

Temporal changes in plasma concentrations of hormones and metabolites in pasture-fed dairy cows during extended lactation

This experiment measured variations in plasma concentrations of metabolic hormones and metabolites in cows undergoing extended lactations of up to 670 d at 2 planes of nutrition. Thirty-seven Holstein-Friesian cows that calved in late winter were selected for varying milk yield and then managed for a lactation of 670 d by delaying breeding until approximately 450 d in milk (DIM). Cows grazed fresh pasture supplemented with pasture silage or hay and crushed wheat or triticale grain. Dietary intake was reduced by approximately 1.8kg (dry matter) grain/cow per day for 19 of the cows from 300 DIM until the end of lactation to assess the effect of restricted energy intake on the persistency of milk production. Samples of blood were collected monthly from each cow to measure plasma concentrations of selected hormones and metabolites. Dietary restriction beyond 300 DIM reduced yields of milk, protein, and fat, but did not alter the proportion of cows reaching the 670-d lactation target. Dietary restriction had no effect on cow BW or plasma concentrations of any hormones or metabolites. Overall, blood plasma concentrations of insulin-like growth factor-I, leptin, and glucose were elevated from 301 to 600 DIM compared with 0 to 300 DIM, whereas concentrations of growth hormone and nonesterified fatty acids were lower after 300 DIM. Plasma concentrations of insulin and prolactin were unaffected by stage of lactation, but prolactin concentrations increased during summer. These changes were consistent with a decrease in milk yield and an increase in the partitioning of nutrients to body tissue gain, primarily adipose tissue, throughout the later stages of the extended lactation. Cows that continued milking beyond 600 DIM had increased plasma concentrations of growth hormone and decreased concentrations of glucose and leptin compared with cows that milked <600 DIM. These differences, coupled with reduced body weight gain, indicated an increased priority for nutrient partitioning to milk production at the expense of body tissue gain throughout the extended lactation period in cows with greater lactation persistency.

Optimisation of the breeding value model of Simmental bull sires

In this research 245 cows were included. They are daughters of ten sires, and they realized 548 lactations in the period from year 2000 to 2003. Data were used from two cattle farms, "Backa" and "Pobeda" that are located on government property "Krivaja". In this research influences of systematic factors like farm, year, season or lactation have been included. Breading values are evaluated for all qualities (milk yield, fat yield, fat percentage and persistency of milk production). Sires are ranked based on average milk yield of his daughters.

Sodium fertilizer application to pasture. 10. A comparison of the responses of dairy cows with high and low milk yield potential

Current recommendations for the intake of sodium of lactating dairy cows are related to milk yield. A study was conducted to compare the responses of cows of high and low milk production potential to the application of sodium fertilizer to grazed perennial ryegrass pasture. The application of sodium fertilizer increased the intake of herbage dry matter (DM), the time that cows spent grazing and the biting rate. It also increased the concentration of sodium, magnesium and calcium in herbage and decreased the concentration of potassium. Applying sodium fertilizer increased milk yield and milk fat concentration and decreased somatic cell count in the milk of cows of low‐production potential only, whereas it increased persistency of milk production in the cows of high‐production potential. The concentration of lactose in milk increased in both groups after the application of sodium fertilizer. It is concluded that the optimum dietary sodium concentration for grazing cows does not increase with milk yield, and that most immediate advantage will be gained from increasing the sodium concentration in herbage for low‐yielding cows.