Lactation In Animals Research Articles

Estimation of genetic parameters for reproductive traits in Korean dairy cattle.

In Korea, dairy cattle breeding programs have historically prioritized productive, conformation traits, leading to positive improvements, yet reproductive traits have lagged in development. This study was conducted to develop the breeding program of key reproductive traits in the Korean dairy cattle population. Utilizing data from 7,596 farms and over seven million observations, we conducted quality control to rectify manual entry errors and selected traits in line with international genetic evaluation standards. Traits analyzed included heifer conception rate (HCR), interval from calving to first insemination (CF), cow conception rate (CCR), interval from first to last insemination (FL), and days open (DO). Genetic parameters were estimated using a single trait animal model for HCR and a multiple lactation animal model for CF, CCR, FL, and DO, considering contemporary group of herd-insemination year, insemination month, and monthly age (MA) as fixed effects. Results showed low heritability estimates, ranging from 0.007 to 0.035 across different traits and lactations. Theoretical reliability appears to be low on average due to the influence of heritability, but it showed sufficiently high reliability in some sires (over 0.8). In terms of genetic and phenotypic trends, capacity for reproductive traits declined for a long time until around 2014. In recent individuals, improved trend can be found. This study addressed the critical need for enhancing reproductive efficiency to complement the existing breeding goals, thereby supporting sustained economic viability in the dairy industry. The results underscore the need for improved data quality and methodological adjustments for reproduction records to enhance the genetic evaluation of dairy cattle in Korea.

Variations in hematological parameters of Brazilian Bonsmara cattle at different stages of lactation

The aim of this study was to evaluate the hematological parameters of non-lactating Bonsmara cows and cows at different stages of lactation. A total of 119 cows were used, divided into four groups according to the number of lactations. The hematological evaluations performed were erythrogram and leucogram using automated equipment. The descriptive statistical analysis of the data was performed with a 5% significance level. The experiment followed the ethical principles of animal experimentation (CEUA-UFU protocol 053/2018). Significant differences were found in first lactation animals for erythrocyte count and in second lactation animals for erythrocyte count, hemoglobin, globule volume and platelets. In third lactation animals, significant differences were found for mean corpuscular hemoglobin concentration and platelets. In non-lactating animals, the mean corpuscular hemoglobin concentration showed a significant difference. For the leukogram, significant changes were found in the third lactation animals for rods; and in the concentration of total leukocytes and lymphocytes in the non-lactating animals. This study on the hematology of Bonsmara cattle can serve as a reference base for hematological parameters and as a stimulus for further research on the subject.

Продуктивные особенности коров голштинской породы разных генетических линий

Abstract. The purpose of the study is to investigate the productive features of Holstein cows of different genetic lines. Methods. The research was carried out in two breeding enterprises of the Sverdlovsk region on the livestock of Holstein cows. Groups of animals were formed by the method of pairs of analogues, taking into account the age of animals in lactation, physiological condition, live weight, lines of breeding bulls. The coefficient of milk content was estimated by the calculation method. The lactose, fat and protein content in milk was determined using a “Bentley 150” device. Somatic cells were determined on the “Somatos-M” device. Bacterial contamination was studied using a reductase assay. Prolactin was determined by enzyme immunoassay, cortisol by immunochemiluminescent method. Results. In terms of milk yield for 305 days of lactation and protein content in milk, Montwick Chieftain cows had an advantage with a significant difference between the groups (P < 0.05). The animals of the Reflection Sovering line were the best in terms of fat content, the difference between the groups was insignificant. The lowest content of somatic cells in milk and bacterial contamination was found in animals of the Reflection Sovering and Vis Back Idial lines. The best indicators of the leukocyte profile were determined in animals of the Vis Back Idial and Montwick Chieftain lines. In terms of glucose and total protein content in the blood, cows of the Montwick Chieftain line had an advantage, in terms of the amount of urea, animals of the Montwick Chieftain and Vis Back Idial line affiliation. The highest level of total lipids in the blood is typical for cows of the Reflection Sovering line. Scientific novelty. The research results indicate the relationship of biological characteristics and milk productivity with different lines of breeding bulls. The leukocyte profile of this herd of cows of different genetic lines in breeding enterprises of the Sverdlovsk region was studied for the first time. Practical significance. The results of the research can be used in breeding enterprises in order to increase the milk productivity of cows.

The effect of 2 different premilking stimulation regimens, with and without a latency period, on teat tissue condition and milking performance in Holstein dairy cows

The objectives of this study were to assess the effect of 2 different premilking stimulation regimens, with and without a latency period between tactile stimulation and the attachment of the milking unit, on the teat tissue condition and milking performance of dairy cows. In a randomized controlled crossover study, 145 Holstein cows milked 3 times daily were assigned to treatment (TRT) or control (CON) groups. Premilking udder preparation for the TRT group consisted of the application of a latency period resulting in a preparation lag time of 90 s. The only difference in the premilking udder preparation of the CON group was the absence of latency period; the milking unit was attached immediately after completion of the tactile stimulation. The average duration of total tactile stimulation in TRT and CON group was 8 ± 2 and 9 ± 2 s, respectively. The study lasted for 14 d and was split into 2 periods, each consisting of a 2-d adjustment period followed by 5 d of data collection. We assessed machine milking-induced short-term changes to the teat tissue by palpation and visual inspection postmilking. Electronic on-farm milk meters were used to assess milking characteristics (milk yield [kg/milking session], machine-on time [s], 2-min milk yield [kg], and duration of low milk flow rate [s]). Generalized linear mixed models were used to analyze the effect of treatment on the outcome variables. The odds of machine milking-induced short-term changes to the teat tissue were lower for cows that received a 90-s preparation lag time (TRT cows) compared with cows in the CON group (odds ratio [95% confidence interval; 95% CI] = 0.13 [0.08-0.20]). The least squares means (95% CI) values of cows in the TRT and CON groups were 15.4 (14.9-15.9) and 15.3 (14.8-15.8) kg, respectively, for milk yield, and 246 (239-253) and 253 (247-260) s for machine-on time. The 2-min milk yield was higher for the TRT compared with CON group cows at all the parity levels. The 2-min milk yields of animals in lactation 1, 2, and ≥3 were 5.7, 5.7, and 6.5 kg, respectively, in the TRT group and 4.6, 5.0, and 5.9 kg in the CON group. The TRT cows spent less time in low milk flow rate compared with CON cows at all parity levels. The durations of low milk flow rate of cows in lactation 1, 2, and ≥3 in the TRT group were 19, 17 and 13 s, respectively, and those in the CON group were 31, 22, and 15 s. In this study, cows that received a latency period, and thus were subjected to a 90-s preparation lag time had lower odds of exhibiting short-term changes to the teat tissue after machine milking, shorter machine-on time, higher 2-min milk yields, and lower durations of low milk flow rates. We conclude that consideration of latency period leading to a 90-s preparation lag time in the premilking stimulation regimen facilitated cows' milk-ejection reflex. This latency period can alleviate the adverse effects of vacuum-induced forces on teat tissue during machine milking, improve udder health, and promote animal well-being.

DNA methylation and gene expression changes in mouse mammary tissue during successive lactations: part I – the impact of inflammation

ABSTRACT Mastitis is among the main reasons women cease breastfeeding, which leads to them supplementing breast milk with artificial formula. In farm animals, mastitis results in significant economic losses and the premature culling of some animals. Nevertheless, researchers do not know enough about the effect of inflammation on the mammary gland. This article discusses the changes to DNA methylation in mouse mammary tissue caused by lipopolysaccharide-induced inflammation (4 h post-injection of lipopolysaccharide). We analysed the expression of some genes related to mammary gland function, epigenetic regulation, and the immune response. The analysis focused on three comparisons: inflammation during the first lactation, inflammation during second lactation with no history of inflammation, and inflammation during second lactation with previous inflammation. We identified differentially methylated cytosines (DMCs), differentially methylated regions (DMRs), and some differentially expressed genes (DEGs) for each comparison. The three comparisons shared some DEGs; however, few DMCs and only one DMR were shared. These observations suggest that inflammation is one of several factors affecting epigenetic regulation during successive lactations. Furthermore, the comparison between animals in second lactation with and without inflammation, with no inflammation history during first lactation showed a different pattern compared to the other conditions in this experiment. This indicates that inflammation history plays an important role in determining epigenetic changes. The data presented in this study suggest that lactation rank and previous inflammation history are equally important when explaining mammary tissue gene expression and DNA methylation changes. Abbreviations: RRBS, reduced representation bisulfite sequencing; RT–qPCR, real-time quantitative polymerase chain reaction; MEC, mammary epithelial cells; TSS, transcription start site; TTS, transcription termination site; UTR, untranslated region; SINE, short interspersed nuclear element; LINE, long interspersed nuclear element; CGI, CpG island; DEG, differentially expressed gene; DMC, differentially methylated cytosine; DMR, differentially methylated region; GO term, gene ontology term; MF, molecular function; BP, biological process

Teat open lesions can lead to challenges at milking time on dairies in the Northeast United States.

During evaluations of teat skin by the authors using National Mastitis Council procedures, teat open lesions (TOL) have been more commonly identified in dairies in the Northeast United States over the last 10 years. The TOL described here are found in all stages of lactation and in any age lactating cow, which is unique from TOL that present mainly in first lactation animals just after calving. Cows with these TOL exhibit more abnormal cow behaviors during the milking event. Based on the authors' subjective field evaluations, dry teat skin condition appears to be a significant risk factor. Although there is a paucity of published literature, the other risk factors that the authors have observed are exposure to wind and significant temperature fluctuations, wet bedding, certain bedding additives, and occasionally mechanical, chemical, or thermal trauma. Teat open lesions have been observed in herds with all the common types of bedding. Treatment and preventative measures have focused on supporting skin conditions through higher emollients in the postmilking teat disinfection (PMTD) and controlling the environmental conditions to which the teat is exposed. This includes an evaluation of cow positioning in the stall as well as bedding levels, which influence bedding contamination. The accuracy of PMTD application can also have an influence. The objective of this narrative review was to search the current literature describing TOL, identify knowledge gaps, describe the authors' field experience with TOL on dairy operations in the Northeast United States, and identify opportunities for future research.

Donkey milk composition is altered by lactation stage and jennies age

The aim of this study was to evaluate whether lactation stage and animal age influence the milk composition of grazing donkeys. Jennies were maintained in an exclusively free-range system during the summer season and grazed on a mixed pasture of native grass. Milk samples were collected by manual milking twice a day, two days a week. Acidity, density, total solids, solids-non-fat, fat, protein, casein, lactose, somatic cell count (SCC), and the proportion of nitrogen fractions of the milk were determined. Milk production was 0.61 kg/animal/day. Lactose, fat, acidity, SSC, and whey protein were not affected by the lactation stage. However, milk total solids, solids-non-fat, protein, casein, and nitrogen fractions (non-protein nitrogen and true protein) decreased as the lactation stage progressed. Total solids and protein decreased with the lactation stage, whereas aging was associated with increased protein and fat concentration in milk. These results indicate that the impact of jenny's age on milk fat was lower than on protein content; for every year of age, milk fat percentage increased by 0.023 and milk protein increased 0.13% units. Therefore, the lactation stage and jenny's age are the determinants of milk composition in grazing donkeys.

Comparison between different selection indices for some productive traits in Friesian cows

Data pertaining to 3,977 records collected over a period of 29 years for Friesian cows were utilized for the present study. Records were analyzed for actual total milk yield (TMY), 305-day milk yield (305d-MY), lactation period (LP) and days open (DO) by VCE 6.0 software while, selection indices (SI) using one phenotypic standard deviation as REV1 and Lamont method as REV2. Estimates of direct heritability were low and ranged from 0.02 to 0.23 while, maternal heritability were low and ranged from 0.03 to 0.028. The correlation coefficients between all studied traits were highly significant and ranged between 0.82 to 0.93. The results indicated that reducing interval of days open (DO) could be brought about by improving the farm managerial aspects. The selection criteria of different indices proved that the index I1which incorporated TMY, 305d-MY, LP and DO was the best (RIH = 0.49) and (RE % = 100.00). This index could effectively anticipate in genetic improvement of all the traits of the study; I1 = 0.144 (TMY) + 0.503 (305day/MY) + 1. 619 (LP) + 1.150 (DO). The application of this index I1 led to a predictive genetic gain of TMY, 305d-MY, LP and DO by 359.4 kg, 279.5 kg, 15.3 days and 3.2 days, respectively. The correlation coefficient between I1 and the total economic value was 0.49 while, the heritability estimate of the index was 0.86. Conclusively, such an index can help the investor in the field of dairy cattle to select the best animals in early lactation and in subsequent generation’s traits as well; which leads to an increase in economic return.

Subclinical ketosis: Prevalence and risk factor analysis in early lactation dairy cattle of Thrissur district

Present study was conducted in Kerala Veterinary and Animal Sciences University farms, various organized and unorganised farms and individual households in Thrissur district during the period of May 2021 to April 2022 with the objectives of estimation of prevalence of subclinical ketosis (SCK) by screening dairy cows on 14th and 28th day post-partum. Multiparous cows with a blood beta-hydroxy butyrate (BHB) value ≥ 1.2 mmol/L without any overt clinical signs were considered as positive for SCK. One hundred and fourteen animals from second to seventh lactation were screened for SCK. Prevalence of SCK was 23.7 per cent on 14th day and 14.04 per cent on 28th day with a total prevalence of 27.2 per cent. Occurrence of SCK was highest in animals in second lactation (54.8 per cent) with more occurrence in crossbred Holstein Friesian cows. Maximum number of positive cases were observed in dairy cows of age between four to six years (54.8 per cent). Body condition score of diseased animals were higher than normal animals. Prevalence was highest in animals calved between months of July to September and 58.1 per cent of affected animals had male calf. Concurrent abnormalities during transition period were also assessed based on clinical examination and farm records.

Dairy cows with different milk urea nitrogen breeding values display different grazing behaviours

The objective of this study was to describe the diurnal pattern of grazing behaviour of multi-parous dairy cows divergent for milk urea N breeding values (MUNBV) and the consistency of these differences across different sward compositions (perennial ryegrass [RG; Lolium perenne L.] or ryegrass with plantain [Plantago lanceolata L.; RGPL]) and stages of lactation (early and late lactation). Jaw movement recorders were fitted to 24 animals in early lactation and 16 cows in late lactation, in early lactation 12 cows were assigned to the ryegrass diet and 12 cows assigned to the plantain diet, in late lactation 8 cows were assigned to ryegrass with the remaining 8 cows assigned to the plantain diet. For each diet half of the animals during both stages of lactation were classified as high for MUNBV and the other half as low for MUNBV. Low MUNBV animals had more mastications per bite over the day (P < 0.01) with a one-unit decrease in MUNBV resulting in 0.07 more bites per mastication during the first two grazing bouts, as well as differences in the temporal distribution of grazing bouts compared with high MUNBV cows. A one-unit decrease in MUNBV resulted in a 0.11 ± 0.02 increase in mastications per bite during the first grazing bout across both stages of lactation and sward composition. Ingestive behaviour has a large impact on the physical features of ingesta and thereby rumen function. The results of this study indicate that dairy cows divergent for MUNBV grazing the same forage apply different grazing strategies in terms of oral processing of ingesta and diurnal meal pattern. These results present potential explanatory variables for phenotypical differences observed in dairy cows divergent for MUNBV.

Characterizing Anti-Müllerian Hormone (AMH) concentration and change over time in Holstein dairy cattle

The objective of this study was to characterize circulating Anti-Müllerian Hormone (AMH) concentrations in a population of Holstein heifers and examine the impact that life events and stage of life have on those concentrations. Virgin, Holstein heifers (n = 105) 13 ± 0.8 months old were heat detected using tail-chalk, bred via artificial insemination and pregnancy checked 32+ days later. Serum samples for AMH were collected upon enrollment (heifer), at 5–20 days in milk (fresh) and at 45–60 days in milk (pre-breeding). Transrectal ultrasonography was performed upon enrollment (heifer) and at 45–60 days in milk (pre-breeding) to determine antral follicle count (AFC), cyclicity status, and uterine health. Heifers were blocked into thirds by AMH concentration: HIGH (>354 pg/mL; n = 34), MID (183–354 pg/mL; n = 35) and LOW (<183 pg/mL; n = 36), with distribution re-evaluated at subsequent samplings (fresh, pre-breeding). As heifers, age and conception risk to first service were not impacted by AMH (P > 0.05). Reason for leaving the herd, health incidences and calving difficulty were not impacted by AMH (P > 0.05). AFC and cyclicity had a positive impact on heifer AMH (P < 0.01). AFC and AMH in heifers were highly correlated (0.56, P < 0.001). AFC for heifers differed by AMH group with the HIGH group having the greatest AFC (8.76), followed by the MID (5.87), then the LOW (3.53) group (P < 0.0001). However, this association was not evident in the pre-breeding group (P > 0.05). From the heifer to the fresh sample, average AMH dropped from 313.15 pg/mL to 160.01 pg/mL (P < 0.0001). Average AMH at the pre-breeding sample was 183.23 pg/mL, which was lower than the heifer sample (P < 0.0001), but not different from the fresh sample (P > 0.05). AFC and AMH at the heifer sample had a positive impact on AMH at the fresh sample (P < 0.01) and pre-breeding AMH was positively impacted by both the fresh and heifer AMH concentration (P < 0.001). Most animals kept their AMH categorization through all three time points with more of the LOW AMH animals maintaining their categorization than the other groups. However, 32.1% of animals changed their AMH categorization from the heifer sample to the fresh sample, with 53.8% moving to a lower AMH categorization (corresponding to lower AMH) and 46.2% moving to a higher AMH categorization (corresponding to higher AMH). No differences were seen in circulating AMH based on health events however, differences in AMH concentration over time indicate a drop in circulating AMH post-calving. Circulating AMH concentration as a pre-breeding heifer is highly indicative of circulating AMH concentration as a first lactation animal and may be used to predict an adult animal’s AMH concentration. However, it is necessary to compare AMH concentrations to herdmates as published AMH values vary widely from herd to herd. In addition, sampling time should be considered when determining AMH categorization of animals as circulating AMH concentration immediately post-calving may not be indicative of an animal’s true AMH categorization.

INFLUENCE OF PROLACTIN (PRL) AND BETA-LACTOGLOBULIN (BLG) GENES ON INDICATORS OF DAIRY PERFORMANCE IN COWS OF THE BELARUSIAN BLACK-AND-WHITE BREED

The results of the studies showed that by the prolactin gene (PRL), the highest yield was found in the first-calf heifers with the PRLBB genotype by 4.7% -10.5% as compared to herd-mates of other genotypes; and in cows of the second and third lactations – with the PRLAB genotype – by 2.6-10.6%. In terms of milk fat, animals with the PRLAB genotype had a higher rate than animals with the PRLAA and PRLBB genotypes by 0.04-0.17 pp, with the second and especially third lactation animals having the most noticeable changes. By the beta-lactoglobulin (BLG) gene, animals with the BLGAA genotype had a higher yield rate for 305 days of lactation in the first-calf heifers; in cows of the second lactation – animals with the BLGAB genotype, and in cows of the third lactation – with the BLGBB genotype. By the content of butterfat and protein in milk, on the contrary,the highest rates in the first calf heifers had animals with the PRLBB genotype; in the second-lactation cows – PRLAB, and in the third-lactation cows – with the PRLAA genotype.

EFFECT OF PROLACTIN (PRL) AND BETA-LACTOGLOBULIN (BLG) GENES ON INDICATORS OF DAIRY PERFORMANCE IN COWS OF RED BELARUSIAN BREED GROUP

Studies show that according to the prolactin gene (PRL), the highest milk yield was determined in the first-calf heifers with the PRLAB genotype by 2.5%, and in cows of the second and third lactations – with the PRLAA genotype by 0.8-7.0%. In terms of fat and milk protein content, animals with the PRLAB genotype had higher rate than those with the PRLAA genotype by 0.1-0.2 pp, the second and especially third lactation animals having the most noticeable changes. For the beta-lactoglobulin (BLG) gene, animals with the BLGBB genotype had the higher rate of milk yield for 305 days of lactation, as well as the amount of milk fat and lactoprotein. With an increase in the lactation ordinal number, the difference in these indices between the BLGAB and BLGAA herdmates increased.

Fodder beet to support early and late lactation milk production from pasture, is it worth the risk?

High yielding crops such as maize (Zea mays L.) and fodder beet (FB; Beta vulgaris L), are commonly used to extend lactation and increase animal productivity from pastoral dairy systems. Financial modelling to compare costs and benefits of different crops is useful for decision making, but such modelling often fails to account for potential animal health risks which can be associated with feeding supplements. A multi-component, whole-farm modelling approach was used to predict milk solids (MS, milk fat + protein) production and the economic farm surplus (EFS: operating surplus – adjustments) between 2016 and 2018 for an irrigated farm in Canterbury (South Island) and a non-irrigated farm in the Waikato (North Island), of New Zealand. The financial risk of the dairy business was measured using the ratio between mean return on assets (ROA) minus an assumed 5% risk-free ROA, and the standard deviation of ROA was calculated from 300 combinations of climate, milk, and feed price, land appreciation, and interest rate. Four scenarios of autumn and spring supplementation of pasture were considered at each geographical location; imported maize silage (Base), a crop of maize silage grown on the milking platform (MSC; area used to produce milk), a crop of FB grown on the milking platform (FBC), and a FB crop with an outbreak of acute (1% stock fatality) and subacute ruminal acidosis (5% decline of feed intake) across the entire herd (FBAC). The MSC scenario improved EFS by 5.8% compared with Base in both the irrigated and the dryland system. The predicted response to MSC reflected greater milk production, lower feed expenses, and shorter crop rotation, compared with either Base, FBC, or FBAC. While FBC increased EFS by 4.8% compared with Base under irrigation, EFS was similar to Base under dryland conditions ($2711 and $2759/ha, respectively). The limited advantage of growing FB under dryland conditions reflect reduced herbage supply due to the extended crop duration of FB compared with maize silage. Model predictions suggest that FBAC will increase the financial risk by reducing milk production and EFS by 6.5% (irrigated) and 7.1% (dryland) compared with Base. In the absence of any adverse health risks, farm performance from the FBC scenario was comparable to that of MSC under irrigated conditions. However, in dryland conditions, and when the potential economic cost of acute and sub-acute ruminal acidosis is considered, there is little advantage to growing FB on the milking platform.

Renal Programming by Transient Postnatal Overfeeding: The Role of Senescence Pathways.

BackgroundEarly nutrition influences the risk of chronic kidney diseases (CKDs) development in adulthood. Mechanisms underlying the early programming of altered renal function remain incompletely understood. This study aims at characterizing the role of cell senescence pathways in early programming of CKD after transient postnatal overfeeding.Materials and MethodsReduced litters of 3 mice pups and standard litters of 9 mice pups were obtained to induce overfed animals during lactation and control animals, respectively. Animals were sacrificed at 24 days (weaning) or at 7 months of life (adulthood). Body weight, blood pressure, kidney weight, and glomerular count were assessed in both groups. Senescence pathways were investigated using β-Galactosidase staining and Western blotting of P16, P21, P53, P-Rb/Rb, and Sirtuin 1 (Sirt1) proteins.ResultsEarly overfed animals had a higher body weight, a higher blood pressure at adulthood, and a higher glomerular number endowment compared to the control group. A higher β-Galactosidase activity, a significant increase in P53 protein expression (p = 0.0045) and a significant decrease in P-Rb/Rb ratio (p = 0.02), were observed at weaning in animals who underwent early postnatal overfeeding. Protein expression of Sirt1, a protective factor against accelerated stress-induced senescence, was significantly decreased (p = 0.03) at weaning in early overfed animals.ConclusionEarly postnatal overfeeding by litter size reduction is associated with increased expression of factors involved in cellular senescence pathways, and decreased expression of Sirt 1 in the mouse kidney at weaning. These alterations may contribute to CKD programming after early postnatal overfeeding.

Comparative Study on Chemical Composition and Mineral Contents of Milk at Different stages of Lactation in Murrah Buffalo

The study was carried out to evaluate the chemical composition and mineral content of buffalo milk collected at different stages of lactation. The samples were collected from three different groups like early lactating animals, mid lactating animals and late lactating animals, these samples were analyzed for chemical composition and mineral contents. The obtained results showed that the main milk constituents were found to be at higher levels in the individual samples of mid lactating animals. The values of Fat, Solids Not Fat and Total Solids ranged between 3.8±0.37%, 11.47±0.51% and 14.35±0.76% respectively for early lactating animals, 6.03±0.75%, 10.36±0.49% and 16.39±.0.90% for mid lactating animals, 4.35±0.69%, 10.92±0.5% and 15.2±0.67% for late lactating animals. Keywords : late lactating animals, FAO , Bubalus bubalis, casienates Cite this Article Hency Rose, Niyas E, Smitha J Lukose, Shibu Simon, Reni John, Jith John. Comparative Study on Chemical Composition and Mineral Contents of Milk at Different stages of Lactation in Murrah Buffalo. Research &amp; Reviews: Journal of Dairy Science &amp; Technology . 2020; 9(1): 1–9p.

FEED ADDITIVES AND LACTATING ANIMALS: RESEARCH AND APPLICATIONS

FEED ADDITIVES AND LACTATING ANIMALS: RESEARCH AND APPLICATIONS

Implications of adapting autumn grazing management on spring herbage production––The effect on late lactation milk production and the subsequent response in early lactation animal performance

The importance of increased grass availability in the diet of the early lactation dairy cow in spring-calving pasture-based systems is widely reported. To combat the effect of low over winter growth rates, closing swards earlier in autumn can allow for greater accumulation of herbage for grazing in spring. The aim of this study was to identify the impact of three autumn closing treatments (varying closing rotation dates); (1) Early – September 25th to November 9th, (2) Normal – October 10th to November 24th and (3) Late – October 25th to December 9th, on late lactation milk production and early lactation milk production in the subsequent spring. The goal was to identify the optimum recommendations for autumn closing management to achieve increased milk production in spring resulting from increased grass availability, without compromising on animal performance in late lactation. There was no effect of autumn closing treatment on late lactation milk yield or milk solids yield. There was, however, a decline in milk protein concentration, associated with the diet change at housing of the early closed treatment (−1.6 g/kg milk) and normal treatment (−0.7 g/kg milk) in autumn compared with the late closed treatment (41.5 g/kg milk), as a result of the increased silage fed during this period (473.2, 345.8 and 163.8 kg DM/cow, respectively). Each one day increase in closing resulted in an extra 16 kg DM/ha in pre-grazing herbage mass on February 1st of the subsequent year (R2 = =0.502). The resulting increases in pre-grazing herbage mass contributed to increased daily herbage allowance (DHA; +2.9 kg DM/cow) and total dry matter intake (+1.3 kg DM/cow) for the early treatment in spring compared with the normal and late closed treatment. Each 1 kg increase in DHA resulted in an increase of 0.38 kg milk/cow/day. A greater proportion of silage was required cumulatively on the early closed treatment (628 kg DM/cow) in contrast to the late closed treatment (419 kg DM/cow) between the autumn and spring period. However, the increased milk production associated with the increased grass availability in spring outweighed the cost associated with the increased silage requirement. Closing the farm early in autumn offers significant advantages in terms of higher DHA, increased dry matter intake and higher milk yields the following spring. Therefore, it is recommended the closing rotation should begin in late September and cease by mid-November, where there is a high demand for grass in early spring.

Pasture allowance, duration, and stage of lactation—Effects on early and total lactation animal performance

Pasture availability in early spring can be limited due to climatic effects on grass production, increasing the likelihood of feed deficits in early lactation of spring-calving pasture-based systems. We hypothesized that restricting pasture allowance (PA) when animals are at peak milk production will have more negative implications on milk production compared with restricting animals before this period. A total of 105 cows were assigned to 1 of 7 grazing treatments from March 14 to October 31, 2016 (33 wk). The control treatment was offered a PA to achieve a postgrazing sward height > 3.5 cm and mean pasture allowance of 15.5 kg of dry matter per cow. The remaining treatments were offered a PA representing 60% of that offered to the control for a duration of 2 or 6 wk from March 14 (mid-March; MMx2 and MMx6), March 28 (end of March; EMx2 and EMx6), or April 11 (mid-April; MAx2 and MAx6). Within grazing treatment, animals were also assigned to 1 of 2 calving dates (early and late) based on days in milk (DIM) on March 14. Early calved (EC) cows were ≥36 DIM, while late calved (LC) were ≤35 DIM. Restricting PA for 2 and 6 wk reduced daily milk yield (-1.6 and -2.2 kg/cow, respectively), cumulative milk protein yield (-4.0 and -6.3 kg/cow, respectively), and cumulative milk solids yield (-5.8 and -9.5 kg/cow, respectively) in the first 10 wk of the experiment. Daily milk yield was similar across the treatments at the end of the 33-wk period (16.8 kg/cow, average of all treatments), as was daily milk solids yield (1.40 kg/cow). Cows in the EC group produced less milk over the first 10 wk of the experiment (20.0 kg/cow per day) compared with the LC animals (22.1 kg/cow per day). However, body weight was greater (+15 kg/cow) in the EC animals compared with the LC, while body condition score was similar (2.85). This outcome indicates that animals that are restricted later in early lactation (circa onset of peak milk production) partition a greater proportion of available energy to maintenance, resulting in greater losses in milk production. These data indicate that despite the immediate reduction in milk production, restricting intake of grazing cows to 80% of that required to achieve spring grazing targets for postgrazing sward height for up to 6 wk may be used as a method of managing short-term pasture deficits on farm with minimal effects on total lactation performance.

Uso de aditivos microbianos de inclusão direta para vacas leiteiras no terço médio da lactação

Quinze vacas Holandês, com 156±53 dias em lactação, produção média de leite 31,4±0,5 kg/d e peso corporal médio de 665±16 kg foram utilizadas com o objetivo de avaliar o uso de aditivos microbianos na dieta. O delineamento experimental adotado foi o de quadrado latino 3 x 3, com cinco repetições. Os tratamentos foram: DFM-B (Ruminobacter amylophilum, Ruminobacter succinogenes, Succinovibro dextrinsolvens, Bacillus cereus, Lactobacillus acidophilus, Enterococus faecium em carbonato de cálcio); DFM-BL (Bactérias e veículo inerte associado a 6x109/g de células vivas e 2x108/g de células mortas de Sacharomyces cerevisiae) ou Controle - 10g de carbonato de cálcio. Os aditivos foram fornecidos em cápsulas por ingestão forçada duas vezes ao dia. A suplementação de animais em terço médio de lactação com DFM-B ou DFM-BL não alterou o consumo, produção e composição de leite, eficiência alimentar, peso e escore de condição corporal. No entanto, animais suplementados com DFM-B tenderam a ter menor pH ruminal, menor excreção de alantoína na urina, maior Nitrogênio ureico no leite (NUL) e menor digestibilidade da matéria seca. Animais suplementados com DFM-BL tenderam a ter menor contagem de células somáticas no leite e maior tempo de mastigação diária, sugerindo que a suplementação associada de bactérias e leveduras tem maior potencial benéfico do que a utilização de apenas bactérias.