Parous Animals Research Articles

Vaginal wall weakness in parous ewes: a potential preclinical model of pelvic organ prolapse.

Ewes develop pelvic organ prolapse (POP) and may be a suitable model for preclinical studies evaluating cell-based therapies for POP. The aim of this study was to establish a clinical score of vaginal weakness and to compare POP Quantification System (POP-Q) values in conscious nulliparous and parous ewes and determine whether ewes are a suitable POP model. Ewes (n = 114) were examined while conscious, without sedation, and standing in a V conveyer by adapting the human POP-Q measurement. Ovine POP was defined as descent to the introitus from POP-Q points Aa 3cm above the introitus on the anterior wall, Ap 3cm above the introitus on the posterior wall, or increased Ba anterior wall descent above the urethra (≥0). A test-retest showed good inter- and intrarater reliability. There was no evidence of tissue mobility at Aa, Ap, Ba (all -3cm) in nulliparous ewes (n = 14). In contrast, multiparous ewes had a median of -1 and interquartile range (IQR) (-2 to 0) for Aa, [0 (-1 to 0)] for Ap and [0 (-2.75 to 0)] for Ba (n = 33; P < 0.0001 in comparison with nulliparous) ewes. Ovine vaginal displacement was seen in 50.9% of parous ewes and was strongly associated with parity (P = 0.003). A modified POP-Q in conscious ewes was established showing that the vaginal wall of parous animals has similar regions of weakness as do women and may be similarly related to parity. Ewes appear to be a representative preclinical model of human vaginal prolapse.

Social stressors and their effects on immunity and health of periparturient dairy cows

Management practices during the periparturient period have been the focus of much research recently because during this period immune function, metabolism, and health of cows are severely challenged. Responses to stress are often classified as behavioral, immunological, neuroendocrine, and autonomic. In production systems, understanding all facets of stress response is important to correctly predict the consequences of stressors to the health and performance of animals and to prevent costly managerial changes that have minimal effect on animal well-being and performance. Common social stressors faced by periparturient animals are regrouping, overstocking, and for nulliparous animals, commingling with parous animals. In conventional dairies, feeding strategies during the periparturient period often require several group changes during the most challenging period of an animal’s life. Traditional weekly regrouping of prepartum cows increases competitive behavior at the feed bunk but it does not affect immune and metabolic responses, health and production, as long as stocking density is not overwhelming, and nulliparous and parous animals are housed separately. Stocking density of prepartum animals may be overlooked because these are nonproductive animals. Severe overstocking (200% of feeding space) of commingled nulliparous and parous pregnant animals produces neuroendocrine and metabolic changes. On the other hand, when prepartum nulliparous and parous animals are housed separately, stocking densities of up to 120% do not seem to affect innate and adaptive immunity, metabolic responses, milk yield, and reproductive performance, despite increasing negative behavior among cows. In recent experiments, when animals were ranked based on feed bunk displacement, dominant animals were more likely to be diagnosed with metritis than subordinate animals. Importantly, dominant animals with large number of interactions with pen mates (displacement at the feed bunk) were considerably more likely to be diagnosed with uterine diseases (retained placenta and metritis) and to be removed from the herd within 60d postpartum. Much has been learned about behavioral responses of cows to stressful conditions, but our understanding of neuroendocrine and immune responses to such conditions is somewhat limited. A multidisciplinary approach to research that encompasses several responses to stress and biological functions is critical.

Abstract B67: The impact of parity on the metastatic success of ovarian cancer.

Abstract Ovarian cancer is the most fatal gynecological cancer. Epithelial ovarian cancer (OvCa), the most common subtype, usually goes undetected until metastatic and often fatal stages of the disease. OvCa follows a unique form of metastasis, spreading through the peritoneal cavity and forming metastatic sites on the peritoneum. Epidemiologic data suggest that child-bearing, or parity, reduces a woman's risk of developing ovarian cancer, with more births providing greater protection. Despite the association of parity with a decreased incidence of ovarian cancer, very few studies have explored the relationship between parity and metastatic success. A recent study compared metastatic success to the omentum in 12-month-old C57Bl/6 retired breeders and 5-month-old virgin mice, reporting that parous mice are less susceptible to metastasis due to the parity-associated differences in the immune compositional profile in the omental fat band (Cohen et al. 2013). This tumor study compared mice of different ages and did not report specific numbers of pregnancies. To further investigate the role of parity number in OvCa metastasis, we designed a study that controls for age and compares mice with specific parity number. Three age-matched C57Bl/6 groups were evaluated: nulliparous (V), parous 1 (P1), and parous 3 (P3) mice. We tested the effect of parity on metastatic success in vivo with an allograft study using the C57Bl/6 syngeneic ID8 mouse ovarian surface epithelial cell line. ID8 ovarian cancer cells (106) were injected into the peritoneal cavity of V, P1 and P3 mice. In contrast to the results of Cohen at al. that utilized a different syngeneic ovarian cancer cell line, we found no significant difference in metastasis to the omentum in the parous animals, but significantly reduced metastasis to the fat-enveloped ovaries and visceral fat pads in the P3 mice. This suggests that the visceral fat adjacent to the uterus and ovaries in multi-parous animals is a unique environment, resilient to metastasis. Factors in fat tissue responsible for this phenomenon are being investigated. Citation Format: Elizabeth A. Loughran, Ryan Phan, Annemarie K. Leonard, Laura Tarwater, Marwa Asem, Yuliya Klymenko, Yueying Liu, Jing Yang, Jeff Johnson, Matthew Ravosa, M. Sharon Stack. The impact of parity on the metastatic success of ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B67.

Study on Prevalence of Sub-Clinical Mastitis in Crossbred Dairy Cattle and its Potential Risk Factors

The study was designed to determine the prevalence of sub-clinical mastitis in cross-bred dairy cattle and potential risk factors associated with the disease. The study was conducted in organized dairy farm at Jammu, and milk samples collected from 106 animals were put to MCMT (Modified Californian Mastitis Test). The overall prevalence of sub-clinical mastitis was found to be 59.43 per cent (%) and quarter level prevalence was at 34.78%. The risk factors under study; parity, age, milk yield and position of quarters, had significant influence on prevalence of sub-clinical mastitis. Prevalence was high in animals with greater than 20 litre (77.41%) of milk yield, and those falling in age group of greater than 8 years (82.92%). In relation to parity of animals and position of quarters, prevalence was maximum in six and above parity animals (78.6%), and with regard to position of quarters, mostly right hind quarters (49.39%) were affected. The pathogens isolated were mostly contagious in nature, and Staphylococcus aureus (66.67%) was most commonly found organisms.

Effect of stocking density on social, feeding, and lying behavior of prepartum dairy animals

The objectives of this study were to determine the effects of prepartum stocking density on social, lying, and feeding behavior of dairy animals and to investigate the relationship between social rank and stocking density. In total, 756 Jersey animals were enrolled in the study approximately 4 wk before expected calving date. This study used 8 experimental units (4 replicates × 2 pens/treatment per replicate), and at each replicate, one pen each of nulliparous and parous (primiparous and multiparous) animals per treatment was enrolled. The 2 treatments were 80% stocking density (80D, 38 animals per pen; each pen with 48 headlocks and 44 stalls) and 100% stocking density (100D, 48 animals per pen). Parous animals were housed separately from nulliparous animals. Animals at 254±3d of gestation were balanced for parity (parous vs. nulliparous) and projected 305-d mature-equivalent milk yield (only parous animals) and randomly assigned to either 80D or 100D. Displacements from the feed bunk were measured for 3h after fresh feed delivery on d 2, 5, and 7 of each week. Feeding behavior was measured for 24-h periods (using 10-min video scan sampling) on d 2, 5, and 7 on wk 1 of every replicate and d 2 and 5 for the following 4 wk. A displacement index (proportion of successful displacements from the feed bunk relative to all displacements the animal was involved in) was calculated for each animal and used to categorize animals into ranking categories of high, middle, and low. Seventy nulliparous and 64 parous focal animals in the 80D treatment and 89 nulliparous and 74 parous focal animals in the 100D were used to describe lying behavior (measured with data loggers). Animals housed at 80D had fewer daily displacements from the feed bunk than those housed at 100D (15.2±1.0 vs. 21.3±1.0 per day). Daily feeding times differed between nulliparous and parous animals at the 2 stocking densities. Nulliparous 80D animals spent 12.4±5.0 fewer minutes per day feeding than nulliparous 100D animals, whereas 100D parous animals tended to spend 7.6±4.5 fewer minutes per day feeding than 80D parous animals. The 2 treatments were not different in the number of lying bouts or lying-bout duration; lying time was longer for 100D on d −33, −29, and −26 and shorter on d −7, −5, and 0 than 80D. The interaction between treatment, parity, and social rank was associated with lying and feeding times. In summary, animals in the 80D treatment had a lower number of displacements from the feed bunk and spent more time lying down near parturition than 100D animals, and 80D nulliparous animals had reduced daily feeding time compared with 100D nulliparous animals. Although these results showed some potential behavior benefits of a prepartum stocking density of 80% compared with 100%, observed changes were small. However, greater stocking density cannot be recommended; more research is needed to evaluate the effects of stocking densities greater than 100% and with other breeds of cattle besides Jersey.

Prepartum stocking density: Effects on metabolic, health, reproductive, and productive responses

The objectives of the current experiment were to determine the effects of 2 prepartum stocking densities on milk yield, concentration of metabolites during the peripartum period, and health and reproductive parameters of dairy cows. Jersey cows enrolled in the experiment at 254±3 d of gestation were balanced for parity (nulliparous vs. parous) and previous lactation projected 305-d mature equivalent milk yield (parous) and assigned to 1 of 2 treatments: 80% headlock stocking density (80SD; 38 animals/48 headlocks) and 100% headlock stocking density (100SD; 48 animals/48 headlocks). The number of experimental units was 8 (4 replicates and 2 pens/treatment per replicate). In total, 154 nulliparous and 184 parous animals were enrolled in the 80SD treatment and 186 nulliparous and 232 parous animals were enrolled in the 100SD treatment. At the start of each replicate, treatments were switched within pen. Cows were milked thrice daily and monthly milk yield, fat and protein content, and somatic cell count data were recorded up to 155 d postpartum. Plasma nonesterified fatty acid concentration was measured weekly, from −18±3 to 17±3 d relative to calving, and plasma β-hydroxybutyrate was measured weekly, from 1±2 to 17±3 d relative to calving. Cows were examined 1, 4±1, 7±1, 10±1, and 13±1 d relative to calving for diagnosis of uterine diseases. Blood was sampled for determination of progesterone concentration and resumption of ovarian cycles 35±3 and 45±3 d relative to calving. Average headlock (74.1±0.4 vs. 94.5±0.3%) and stall (80.8±0.4 vs. 103.1±0.4%) stocking density was lower for the 80SD treatment compared with the 100SD treatment. Treatment did not affect incidence of retained fetal membranes (80SD=5.1, 100SD=7.8%), metritis (80SD=21.2, 100SD=16.7%), acute metritis (80SD=9.9, 100SD=9.4%), and vaginal purulent discharge (80SD=5.8, 100SD=7.9%). Concentrations of nonesterified fatty acids (80SD=251.5±6.1, 100SD=245.9±5.6μmol/L) and β-hydroxybutyrate (80SD=508.2±14.3, 100SD=490.9±13.6μmol/L) were not different between treatments. Treatment had no effect on percentage of cows removed from the herd on the first 60 d postpartum (80SD=6.1, 100SD=5.1%) and on rate of removal from the herd up to 305 d postpartum 80SD=referent, 100SD [adjusted hazard ratio (95% confidence interval)]=1.02 (0.75, 1.38). Percentages of cows pregnant to first (80SD=41.9, 100SD=48.4%) and second (80SD=49.3, 100SD=42.0%) postpartum AI were not different between treatments. Finally, treatment did not affect energy-corrected milk yield up to 155 d postpartum (80SD=33.8±0.5, 100SD=33.4±0.5kg/d). In herds with weekly or twice weekly movement of new cows to the prepartum pen and separate housing of nulliparous and parous animals, a target stocking density of 100% of headlocks on the day of movement is not expected to affect health, metabolic, reproductive, and productive parameters.

The Parity-Associated Microenvironmental Niche in the Omental Fat Band Is Refractory to Ovarian Cancer Metastasis

Ovarian cancer is an insidious and aggressive disease of older women, typically undiscovered before peritoneal metastasis due to its asymptomatic nature and lack of early detection tools. Epidemiologic studies suggest that child-bearing (parity) is associated with decreased ovarian cancer risk, although the molecular mechanisms responsible for this phenomenon have not been delineated. Ovarian cancer preferentially metastasizes to the omental fat band (OFB), a secondary lymphoid organ that aids in filtration of the peritoneal serous fluid (PSF) and helps combat peritoneal infections. In the present study, we assessed how parity and age impact the immune compositional profile in the OFB of mice, both in the homeostatic state and as a consequence of peritoneal implantation of ovarian cancer. Using fluorescence-activated cell sorting analysis and quantitative real-time PCR, we found that parity was associated with a significant reduction in omental monocytic subsets and B1-B lymphocytes, correlating with reduced homeostatic expression levels of key chemoattractants and polarization factors (Ccl1, Ccl2, Arg1, and Cxcl13). Of note, parous animals exhibited significantly reduced tumor burden following intraperitoneal implantation compared with nulliparous animals. This was associated with a reduction in tumor-associated neutrophils and macrophages, as well as in the expression levels of their chemoattractants (Cxcl1 and Cxcl5) in the OFB and PSF. These findings define a preexisting "parity-associated microenvironmental niche" in the OFB that is refractory to metastatic tumor seeding and outgrowth. Future studies designed to manipulate this niche may provide a novel means to mitigate peritoneal dissemination of ovarian cancer.

Risk factors of Q fever in sheep and goat flocks with history of abortion

The purpose of this study was to determine the individual- and flock-level risk factors of Q fever in sheep and goat flocks in Iran. A total of 970 sera including 803 ovine and 167 caprine samples from 43 sheep and goat flocks in the Southwest, Central, and Western Iran were collected randomly. A questionnaire was administered to each visited farm to gather information for investigation of suggested risk factors. The CHEKIT Q fever ELISA kit was used to identify specific antibodies against Coxiella burnetii in sheep and goats. The results showed that the flock level prevalence of Q fever was 100 %. Among the studied risk factors, significant association was observed for seropositivity with area, breed, and parity on individual level and presence of ticks on flock level. Central Iran significantly had the highest prevalence followed by Southwest and Western Iran which could be due to favorable climatic conditions for aerosol transmission of C. burnetii in this area. Native breed had the highest prevalence (28.9 %) of Q fever followed by mixed (22.2 %) and Afshari (13.3 %) breed (P < 0.05). Seropositivity increased with parity, and third parity animals had the highest prevalence (29.3 %). There was significant association between presence of tick on the farm with seroprevalence of Q fever; farms with tick contamination had higher prevalence compared to tick-free farms (27.3 vs 20.3 %, respectively, P = 0.04). In conclusion, the present study demonstrated the relatively high prevalence of Q fever in sheep and goat flocks in Iran. Further, the native breed and third parity animals on individual level and presence of tick on flock level are considered the most important risk factors for C. burnetii infection.

Milk production and somatic cell counts: A cow-level analysis

The objectives of this study were to quantify the relationship between 24-h milk loss and lactation milk loss due to mastitis at the cow level. For the year 2009, individual cow test-day production records from 2,835 Ontario dairy herds were examined. Each record consisted of 24-h milk and component yields, stage of lactation (days in milk, DIM), somatic cell count (SCC, ×103 cells/mL) and parity. The modeling was completed in 2 stages. In stage 1, for each animal in the study, the estimated slope from a linear regression of 24-h milk yield (kg), adjusted for DIM, the quadratic effect of DIM, and the 24-h fat yield (kg) on ln(SCC) was determined. In stage 2, the estimated slope were modeled using a mixed model with a random component due to herd. The fixed effects included season (warm: May to September, cool: October to April), milk quartile class [MQ, determined by the rank of the 24-h average milk yield (kg) over a lactation within the herd] and parity. The estimated slopes from the mixed model analysis were used to estimate 24-h milk loss (kg) by comparing to a referent healthy animal with an SCC value of 100 (×103 cells/mL) or less. Lactation milk loss (kg) was then estimated by using estimated 24-h milk loss within lactation by means of a test-day interval method. Lactation average milk loss (kg) and SCC were also estimated. Lastly, lactation milk loss (kg) was modeled on the log scale using a mixed model, which included the random effect of herd and fixed effects, parity, and the linear and quadratic effect of the number of 24-h test days within a lactation where SCC exceeded 100 (×103 cells/mL; S100). The effect of SCC was significant with respect to 24-h milk loss (kg), increasing across parity and MQ. In general, first-parity animals in the first MQ (lower milk yield animals) were estimated to have 45% less milk loss than later parity animals. Milk losses were estimated to be 33% less for animals in first parity and MQ 2 through 4 than later parity animals in comparable MQ. Therefore, the relative level of milk production was found to be a significant risk factor for milk loss due to mastitis. For animals with 24-h SCC, values of 200 (×103 cells/mL), 24-h milk loss ranged from 0.35 to 1.09kg; with 24-h SCC values of 2,000 (×103 cells/mL), milk loss ranged from 1.49 to 4.70kg. Lactation milk loss (kg) increased significantly as lactation average SCC increased, ranging from 165 to 919kg. The linear and quadratic effect of S100 was a significant risk factor for lactation milk loss (kg), where greatest losses occurred in lactations with 5 or more 24-h test days where SCC exceeded 100 (×103 cells/mL).

Effects of continuous lactation and short dry periods on mammary function and animal health

The dry period is required to facilitate cell turnover in the bovine mammary gland in order to optimize milk yield in the next lactation. Traditionally, an 8-week dry period has been a standard management practice for dairy cows based on retrospective analyses of milk yields following various dry period lengths. However, as milk production per cow has increased, transitioning cows from the nonlactating state to peak milk yield has grown more problematic. This has prompted new studies on dry period requirements for dairy cows. These studies indicate a clear parity effect on dry period requirement. First parity animals require a 60-day dry period, whereas lactations following later parities demonstrate no negative impact with 30-day dry period or even eliminating the dry period when somatotropin (ST) is also used to maintain milk yields. Shortened dry periods in first parity animals were associated with reduced mammary cell turnover during the dry period and early lactation and increased numbers of senescent cells and reduced functionality of lactating alveolar mammary cells postpartum. Use of ST and increased milking frequency postpartum reduced the impact of shortened dry periods. The majority of new intramammary infections occur during the dry period and persist into the following lactation. There is therefore the possibility of altering mastitis incidence by modifying or eliminating the dry period in older parity animals. As the composition of mammary secretions including immunoglobulins may be reduced when the dry period is reduced or eliminated, there is the possibility that the immune status of cows during the peripartum period is influenced by the length of the dry period.

Effect of vacuum level on milk flow traits in Mediterranean Italian buffalo cow

The aim of this study was to determine the effects of six different working vacuum levels (range 37–52 kPa) on the milk production, milk flow rate and milking times of Mediterranean Italian buffalo. A total of 801 milk flow curves of 450 animals of different parity and at different stages of lactation were recorded at random by electronic milk flow meters (Lactocorder®) over a period of 12 weeks. The vacuum level did not significantly affect the individual milk production per milking (average 4.02±0.06 kg). Lower vacuum level resulted in a decrease in average and peak flow rate (P<0.001), and an increase in effective milking time between attaching the teat cup and reaching the value of 0.20 kg/min at the end of milking (P<0.001). Vacuum levels of 37 and 40 kPa provided good milkability conditions, in which the plateau phase was longer than the decline phase while lag time was not affected by vacuum level.

BRCA1 Basal-like Breast Cancers Originate from Luminal Epithelial Progenitors and Not from Basal Stem Cells

Breast cancers in BRCA1 mutation carriers frequently have a distinctive basal-like phenotype. It has been suggested that this results from an origin in basal breast epithelial stem cells. Here, we demonstrate that deleting Brca1 in mouse mammary epithelial luminal progenitors produces tumors that phenocopy human BRCA1 breast cancers. They also resemble the majority of sporadic basal-like breast tumors. However, directing Brca1 deficiency to basal cells generates tumors that express molecular markers of basal breast cancers but do not histologically resemble either human BRCA1 or the majority of sporadic basal-like breast tumors. These findings support a derivation of the majority of human BRCA1-associated and sporadic basal-like tumors from luminal progenitors rather than from basal stem cells. They also demonstrate that when target cells for transformation have the potential for phenotypic plasticity, tumor phenotypes may not directly reflect histogenesis. This has important implications for cancer prevention strategies.

Genetic variation in serological response to Mycobacterium avium subspecies paratuberculosis and its association with performance in Irish Holstein–Friesian dairy cows

Paratuberculosis, also referred to as Johne's disease, is a contagious and chronic disease in ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP) . Few estimates of the genetic variation in measures of susceptibility to MAP are available in the literature and even less have attempted to elucidate the genetic associations between measures of susceptibility to MAP and performance in dairy cattle. The objectives of this study were to estimate the genetic variation in serological response to MAP in 4789 Holstein–Friesian dairy cows from 44 Irish dairy herds, and to quantify its genetic association with performance traits measured in the first three lactations of genetically related animals. Univariate mixed linear and threshold animal models were used to estimate variance components and genetic correlations were estimated using bivariate animal linear mixed models; MAP serological response was treated as a continuous variable and dichotomous variable. The prevalence of MAP in the sample population was 4.4%. This figure cannot be extrapolated to the national dairy herd as the sample population was biased towards herds with increased likelihood of MAP infection. Estimates of heritability for MAP serological response varied from 0.07 to 0.15 depending on the model of analysis and whether serological response was treated as continuous or binary; standard errors varied from 0.024 to 0.062. Genetic correlations between MAP serological response and lactation milk, fat and protein yield were negative or close to zero although not always more than two standard errors from zero; stronger negative genetic correlations were evident in older parity animals. Serological response to MAP was not genetically correlated with milk fat concentration but was positively genetically correlated with milk protein concentration in first lactation and negatively correlated with calving interval. There was little or no genetic association between serological response to MAP and survival. Results from this study corroborate previous international suggestions that selection for reduced serological response to MAP is possible, although this does not necessarily imply a concurrent selection for either reduced prevalence of clinical disease or increased resistance to MAP infection.

Pregnancy in the mature adult mouse does not alter the proportion of mammary epithelial stem/progenitor cells

IntroductionIn humans, an early full-term pregnancy reduces lifetime breast cancer risk by up to 50% whereas a later pregnancy (>35 years old) can increase lifetime risk. Several mechanisms have been suggested, including changes in levels of circulating hormones, changes in the way the breast responds to these hormones, changes in gene expression programmes which may alter susceptibility to transformation and changes to mammary stem cell numbers or behaviour. Previous studies have shown that the mammary tissue isolated from both virgin and parous mice has the ability to repopulate a cleared mammary fat pad in transplant experiments. Limited dilution transplant assays have demonstrated that early pregnancy (at 5 weeks of age) reduces stem/progenitor cell numbers in the mouse mammary epithelium by twofold. However, the effects on stem/progenitor cell numbers in the mammary epithelium of a pregnancy in older animals have not yet been tested.MethodsMice were put through a full-term pregnancy at 9 weeks of age, when the mammary epithelium is mature. The total mammary epithelium was purified from parous 7-week post-lactation and age-matched virgin mice and analysed by flow cytometry and limiting dilution cleared fat pad transplants.ResultsThere were no significant differences in the proportions of different mammary epithelial cell populations or numbers of CD24+/Low Sca-1- CD49fHigh cells (stem cell enriched basal mammary epithelial compartment). There was no significant difference in stem/progenitor cell frequency based on limiting dilution transplants between the parous and age-matched virgin epithelium.ConclusionsAlthough differences between parous and virgin mammary epithelium at later time points post lactation or following multiple pregnancies cannot be ruled out, there are no differences in stem/progenitor cell numbers between mammary epithelium isolated from parous animals which were mated at 9 weeks old and virgin animals. However, a recent report has suggested that animals that were mated at 5 weeks old have a twofold reduction in stem/progenitor cell numbers. This is of interest given the association between early, but not late, pregnancy and breast cancer risk reduction in humans. However, a mechanistic connection between stem cell numbers and breast cancer risk remains to be established.

Induction of a novel histone deacetylase 1/c‐Myc/Mnt/Max complex formation is implicated in parity‐induced refractoriness to mammary carcinogenesis

Refractoriness to carcinogen-induced increases in epithelial cell proliferation is a very important characteristic of parous mammary glands. We found that N-methyl-N-nitrosourea (MNU)-induced proliferative burst in the mammary ductal epithelium was blocked in parous glands but not in age-matched virgin (AMV) glands. The inhibition of the proliferative burst in MNU-treated parous mammary glands coincided with the upregulation of Mnt, a Myc-suppressor, and the formation of histone deacetylase 1/Mnt/Max complexes that unexpectedly contained c-Myc. These complexes formed on the promoters of Myc targets, such as ornithine decarboxylase, cyclin D2, and transforming growth factor beta1 genes, in quiescent fibroblasts, and were disassembled in serum-stimulated cells. These results suggest that the complexes also function as transcription repressors of the growth-related Myc targets in MNU-treated parous mammary glands. Using the chemical mammary carcinogenesis model of human c-Ha-ras transgenic (Tg) rats, we confirmed that parity protected the mammary glands at the postinitiation phase of tumorigenesis. Although the incidence of 7,12-dimethylbenz[alpha]anthracene-induced palpable tumors was reduced from 61.5% in the AMV Tg rats to 28.5% in the parous animals, the incidence of early neoplastic lesions in the parous rats was the same as that in the AMV rats. Restriction fragment length polymorphism analysis detected mutations in the human c-Ha-ras gene in most of the normal-appearing parous Tg glands, as well as in the virgin glands. We propose that accelerated formation of HDAC1/c-Myc/Mnt/Max complexes in response to carcinogen exposure results in down-regulation of growth-related genes, leading to the refractoriness of parous mammary glands at the postinitiation phase of carcinogenesis.

Management Risk Factors Associated with Stillbirth

The success of parturtion depends on a variety of cow and herd factors. It has been previously documented that the rate of stillbirth in Holstein cattle is approximately 10-15% in first parity animals and 5-7% in multiparous animals. Stillbirth is defined as delivery of a dead calf or a calf that is born alive but dies within the first 24 hours of life. Stillbirth can have both direct and indirect impacts on cow and calf health. Therefore, identification of key risk factors and implementation of changes to routine protocols aimed at reducing the occurrence of these calving disorders will benefit the dairy operation.

Seasonality of calving in Nili-Ravi buffaloes, purebred Sahiwal and crossbred cattle in Pakistan

Pattern of calving was documented in Nili-Ravi buffaloes and compared with Sahiwal cattle and Sahiwal (x Friesian or Jersey) crossbreds. Lactation records of 9,174, 22,499 and 656 of Nili-Ravi buffaloes, Sahiwal and crossbred cattle in Punjab province of Pakistan were used for comparison. Punjab province of Pakistan has harsh summers and mild winters. Pattern of calving in first and later parity was different in Sahiwal cows but similar in buffaloes and crossbreds. Calving frequency was highest in January (13.2%) for Sahiwal and in August for buffaloes (17.8%) and crossbred cattle (15.2%). Lowest calvings were recorded in October for Sahiwal (5.2%) and in April for buffaloes (2.5%) and crossbred cattle (3.5%). Winter (January-February) is, thus, the calving season for Sahiwals and Autumn (August-September) is the calving season of buffaloes and crossbred cattle. Calving pattern in crossbreds was more similar to buffaloes than to Sahiwals. Seasonality of calving index (1– ratio of number of calvings in month with fewest calvings and number of calvings in month with most calvings) was 86, 60 and 77 in buffaloes, Sahiwal cattle and crossbred cattle, respectively. Comparison of first and later parity animals indicated that first parity Sahiwals were more seasonal in calving than in their later parity (82 vs 53) while later parity crossbreds were more seasonal calvers than first parity crossbreds (86 vs 59). In buffaloes on the other hand, first and later parity animals had more pronounced but similar seasonality of calving (88 vs 85). Seasonality of calving is more pronounced in buffaloes than Sahiwal and crossbred cattle in Pakistan.

Milk yield and season of calving in buffaloes and cattle in Pakistan

Seasonality of calving and its association with milk yield was analyzed in Nili-Ravi buffaloes and compared with Sahiwal cattle and Sahiwal (x Friesian or Jersey) crossbreds. Records of 9,174 lactations of Nili-Ravi buffaloes from four institutional herds, 22,499 lactations from five Sahiwal herds and 656 lactations from a crossbred cattle herd were used for comparison. All the herds were located in Punjab province of Pakistan where environment is tropical. Month of calving was important source of variation in lactation milk yield of Nili-Ravi buffaloes and Sahiwal cattle but not in crossbred cattle (due to wide variation). Interactions of month of calving with parity as well as with herd were significant (P<0.01) both for buffaloes and Sahiwal cattle. First parity lactation milk yield averaged 1813±23.2, 1305±11.0 and 2459±81.8 litres while averages of later parity animals were 1926±19.0, 1527±7.6 and 2842±54.2 litres for Nili-Ravi buffaloes, Sahiwal and crossbred cattle, respectively. Milk yield pattern in crossbreds was more similar to buffaloes than to Sahiwals. Yet, crossbreds calving in June produced statistically similar but numerically higher lactation milk yield (2950±170 litres) than other months but this was not true for buffaloes and Sahiwals. Buffaloes and Sahiwal cows calving in January-February produced better lactation yields than those calving in other months. Different pattern of milk yield in the three dairy species can be used advantageously for sustainable milk supply throughout the year.

Association between body condition score and live weight in pasture-based Holstein-Friesian dairy cows

The objective was to quantify the strength of the relationship between body condition score (BCS) and live weight (LW) in pasture-based Holstein-Friesian dairy cattle, and to determine the kg LW per unit BCS. A total of 26021 test-day records with information on both BCS (1-10 scale, where 1 is emaciated and 10 is obese) and LW across 1110 lactations from one research farm were used in the analysis. Correlation and regression analyses were used to determine the degree of association between BCS and LW in different parities, stages of the inter-calving interval and years. Correlations between BCS and LW were relatively consistent, with the mean correlation between BCS and LW across all data of 0.55 implying that differences in BCS explain approximately 30% of the variation in LW. Significantly different regressions of LW on BCS were present within stage of inter-calving interval by parity subclasses. Excluding calving, LW per unit BCS varied from 17 kg (early to mid lactation in parity 1) to 36 kg (early lactation in parity 4 and 5). However, LW per unit BCS was greatest at calving varying from 44 kg in first parity animals to 62 kg in second parity animals. On average, 1 BCS unit equated to 31 kg LW across all data.

Lactation weight loss influences subsequent reproductive performance of sows

In order to examine the effect of different lactation weight losses of sows of different parity on subsequent reproductive performance, the present trial was performed in German ( n = 4) and Slowakian ( n = 11) indoor pig breeding units ( n = 1677 sows evaluated). Weaning-to-service-intervals, farrowing rates and total-born litter sizes in sows with different lactation weight losses were compared. Sows were categorized according to lactation weight losses of <5%, 5–10%, 11–15%, 16–20%, >20%. Lactation weight losses exerted a quadratic effect ( P < 0.01) on weaning-to-service-intervals. When analyzed across parity categories, with parity category included as a fixed effect, the weaning-to-service-intervals appeared to be minimized at lactation weight losses of <5%. Weaning-to-service-intervals increased ( P < 0.05) when lactation weight losses increased above 5% for parity 1 sows, but not until lactation weight losses exceeded 10% for animals of parity 2 and more. There was a parity effect observed at lactation weight losses of <10%, P < 0.05, but the difference was not significant any more at lactation weight losses of >10%. Lactation weight losses >10% had a negative ( P < 0.05) effect on subsequent farrowing rates to first service. The difference was higher ( P < 0.01) in sows with lactation weight losses >20%. Lactation weight losses exerted a negative ( P < 0.001) effect on total-born litter sizes in parity 1 versus parity >5 and parity 1 versus parity 2–5 sows at lactation weight losses of >10%. Conclusion: As weight loss of sows during lactation increases subsequent reproduction performance decreases.