Multiparous Dams Research Articles

Specific‐pathogen‐free status is associated with lower infant mortality rate in rhesus macaque (Macaca mulatta) colonies at the California National Primate Research Center

Specific-pathogen-free (SPF) rhesus macaques, Macaca mulatta, are a valuable resource in biomedical research, and demographic analysis plays a significant role in colony management. Data collection included SPF levels, gender, birth year, season of birth, birth location, rearing condition, maternal pregnancy history, and maternal age. Infant mortality in SPF rhesus macaques was compared with that in non-SPF rhesus macaques at the California National Primate Research Center over a six-year period, using Cox proportional regression analysis. In infants born to multiparous dams, the SPF infants had a significantly lower rate of mortality than non-SPF infants. There was no statistically significant difference in infant mortality between different SPF levels. Elimination of selected endemic viruses from breeding populations of rhesus macaques for the purpose of SPF colony development is associated with a significant reduction in the infant mortality rate.

Multiparity leads to obesity and inflammation in mothers and obesity in male offspring

Multiparity is an independent risk factor for obesity in parous females. In addition to being a health issue for the mother, offspring of multiparous females may also be at risk for obesity later in life. The aim of the current study was to establish a mouse model that mimics the human pathology of multiparity and determine the effects of multiparity-induced obesity (MIO) on offspring in adulthood. C57BL/6 mice were mated and studied when primiparous (1st pregnancy) or multiparous (4th pregnancy). Dams became obese with multiparity, an effect that was independent of the age of the dam. Multiparous dams also had increased markers of inflammation (JNK activation, cytokine expression) in adipose tissue and liver that was greater than inflammation in nulliparous females made obese with a high-fat diet. Placental inflammation was prevalent in multiparous vs. primiparous dams as well. Male offspring of the multiparous dams developed increased adiposity by 24 wk of age relative to the progeny of primiparous dams, although food consumption was similar in both groups. Lipid metabolism was altered in liver and fat in that mRNA levels of regulatory genes (PGC-1α) as well as metabolic genes (CPT I) and Akt phosphorylation were decreased in offspring of multiparous dams. Thus, in mice, as in humans, multiparity increases adiposity and is associated with hepatic and placental inflammation and abnormal glucose tolerance. Importantly, MIO leads to increased body fat and metabolic dysfunction in the offspring, suggesting a role in the propagation of obesity.

Reproductive Experience Affects Parental Retrieval Behaviour Associated with Increased Plasma Oxytocin Levels in Wild‐Type and Cd38‐Knockout Mice

The transition to motherhood results in a number of hormonal, neurological and behavioural changes necessary to ensure offspring growth. Once motherhood is established, further neurological and behavioural changes may result in long-term memory in mothering. Recent research has shown that postpartum motherhood enhances both nurturing behaviour and oxytocin activities. The transmembrane glycoprotein, CD38, is expressed on many neuronal cells and has been shown to play a role in social behaviours through stimulating the release of oxytocin in the hypothalamus. The present study was performed to investigate the effects of reproductive experience (primi- and multiparity, dams and sires) on the degree of parental behaviour, such as retrieval. Comparisons were performed between wild-type (Cd38 (+/+) ) and Cd38 knockout (Cd38 (-/-) ) mice of the ICR strain. Multiparous Cd38 (-/-) dams retrieved pups much faster than primiparous mice, whereas there were no significant differences between primi- and multiparous Cd38 (+/+) dams. Plasma oxytocin levels were significantly increased in multiparous dams of both genotypes. In addition, oxytocin levels in the hypothalamus and pituitary were lower in Cd38 (-/-) than in wild-type mice. ADP-ribosyl cyclase activity in the hypothalamus, but not in the pituitary, was slightly increased in Cd38 (+/+) dams. In an identical test, 40% of first-time Cd38 (+/+) sires showed retrieval. The time required to retrieval was shorter in second-time Cd38 (+/+) sires. Both first- and second-time Cd38 (-/-) sires showed only 10% retrieval behaviour. These results indicate that parental behaviour is improved by reproductive experience, especially in Cd38 (-/-) dams, and suggest that these effects may be a result of increased oxytocin levels.

돼지에서 입붙이 사료와 대용유 급여 및 이유자돈 사양프로그램이 이유 전과 이유 후의 성장에 미치는 영향

본 연구는 이유 전과 후 돼지 사양프로그램이 성장에 미치는 영향을 구명하고자 수행되었다. 다산차(Yorkshire <TEX>${\times}$</TEX> Landrace) 모돈과 Duroc 웅돈 사이에서 태어난 총 24복(평균 10.6자돈/복)의 돼지를 3구로 나누어 포유기간 중에 "대조구"는 21일령 이유시까지 대용유와 입붙이 사료를 급여하지 않았고, "최소구"는 포유기 15일째부터 입붙이 사료를 200 gm/복/일 급여했으며, "최대구"는 7일째부터 주간에 7시간 동안 대용유와 입붙이 사료를 무제한으로 급여하였다. 대조구와 최소구로부터 이유된 돼지 중에서 실험구당 68두씩 임의로 선발된 돼지는 각각 2돈방에 수용하고 이유자돈 1, 2 및 3호 사료를 각각 7, 14 및 13일간 급여하였고, 최대구로부터 이유된 같은 수의 자돈에게는 1, 2 및 3단계 사료를 6, 10 및 18일간 급여하였다. 이후에는 모든 실험구에 육성돈 전 후기 사료를 차례로 95 및 135일령까지 급여하였다. 이상의 이유 전과 이유 후전 과정 사양시험은 분할법(split plot) 실험설계 하에 3차례 반복되었다. 포유자돈의 개시체중, 종료체중 및 일당증체량은 최대구와 최소구 대비 대조구 간에 차이가 없었다. 그러나 개시체중은 대조구에 비해 최대구가 0.17 kg 작았지만 개시체중에 보정된 최대구의 종료체중은 대조구에 비해 0.31 kg 컸던 반면 최소구와 대조구 간의 차이는 보정 후에도 거의 변하지 않았다. 자돈기 및 육성기 돼지 성장은 사양프로그램의 영향을 받지 않은 반면 55일령과 135일령 및 6일령 체중은 이유체중과 높은 상관관계가 있었다(각각 r=0.81, 0.57 및 0.76; P<0.001, 0.05 및 0.001). 결론적으로 본 결과는 포유기 초기부터 대용유와 입붙이 사료를 급여하면 체중이 낮은 자돈에 증체 효과가 있을 것이나 포유기 후기에 입붙이 사료를 제한적으로 급여하거나 1, 2단계 자돈사료 급여기간을 수일 연장해서는 자돈기 및 그 이후의 돼지 성장에 영향을 미치지 않을 것임을 시사한다. The present study was performed to investigate the effects of pre- and post-weaning feeding programs on growth of pigs. A total of 24 litters (avg. 10.6 piglets/litter) born from multiparous (Yorkshire <TEX>${\times}$</TEX> Landrace) dams <TEX>${\times}$</TEX> Duroc sires were provided with neither creep feed (CF) nor milk replacer ("CON"), 200 gm CF/litter/d from the 15th day of lactation ("MIN"), or CF and milk replacer ad libitum for 7 h during the daytime from the 7th day ("MAX") through weaning at d 21 of age. Sixty-eight weanling pigs selected randomly from each of CON and MIN were provided with phases 1, 2 and 3 nursery diets for 7, 14, and 13 days, respectively, in two pens; an equal number of piglets from MAX received the same diets for 6, 10, and 18 days, respectively. Subsequently, all pigs were fed grower 1 and 2 diets sequentially up to d 95 and 135, respectively. The entire pre- and post-weaning feeding trial was repeated three times under a split-plot design of experiment. Initial and final weights and ADG of the suckling pigs did not differ between MAX/MIN and CON. However, final wt of MAX adjusted for initial wt, which was 0.17-kg less in MAX than in CON, was greater than that of CON by 0.31kg, whereas the difference between MIN and CON in final wt barely changed after the adjustment. Growth of the animals during the nursery and growing phases was not affected by the feeding program, whereas d 55 and 135 BW, as well as d 6 BW, were highly correlated with weaning weight (r=0.81, 0.57, and 0.76; P<0.001, <0.05, and <0.001, respectively). In conclusion, results suggest that provision of creep feed and milk replacer from early lactation may be effective for increasing weight gain of light piglets, but that limited provision of creep feed during late lactation or extension of the duration of phases 1 and 2 vs. 3 nursery diets for several days is unlikely to influence the growth of pigs during the corresponding and subsequent periods.

Reproductive Experience Alters Prolactin Receptor Expression in Mammary and Hepatic Tissues in Female Rats1

Recent studies have reported that reproductive experience in female rats alters prolactin (PRL) receptor gene expression in the brain as well as neural sensitivity to PRL. Given PRL's actions in nonneural tissues, that is, mammary tissue and liver, it was asked whether reproductive experience may also alter prolactin receptor (Prlr) gene expression in these tissues. Groups of age-matched female rats were generated with varying reproductive histories. Separate groups of primiparous (first lactation) and multiparous (second lactation) had mammary tissue and liver samples collected on Day 3 or 10 of lactation. A fifth group raised one litter to weaning and then resumed estrous cyclicity. This group and a final group of age-matched, virgin controls were killed on diestrus. Tissue was processed by quantitative PCR for expression rates of the long and short forms of Prlr mRNA as well as casein beta mRNA (mammary tissue only). Western blots were performed to quantify receptor protein content. Multiple lactations as well as lactation itself resulted in alterations in Prlr expression. Prlr gene expression in mammary tissue was increased in primiparous mothers compared with that in multiparous dams, whereas in the liver, Prlr expression was reduced during an initial lactation. In contrast, PRLR protein levels declined during lactation in mammary, but not hepatic, tissues. Overall, the results demonstrate that the prolactin receptor system is altered in nonneural tissues as a result of the female's reproductive history. The findings are discussed in the context of milk and bile production and PRL's possible role in breast cancer.

VHL Deletion Impairs Mammary Alveologenesis but Is Not Sufficient for Mammary Tumorigenesis

Overexpression of hypoxia inducible factor-1 (HIF-1)alpha, which is common in most solid tumors, correlates with poor prognosis and high metastatic risk in breast cancer patients. Because HIF-1alpha protein stability is tightly controlled by the tumor suppressor von Hippel-Lindau (VHL), deletion of VHL results in constitutive HIF-1alpha expression. To determine whether VHL plays a role in normal mammary gland development, and if HIF-1alpha overexpression is sufficient to initiate breast cancer, Vhl was conditionally deleted in the mammary epithelium using the Cre/loxP system. During first pregnancy, loss of Vhl resulted in decreased mammary epithelial cell proliferation and impaired alveolar differentiation; despite these phenotypes, lactation was sufficient to support pup growth. In contrast, in multiparous dams, Vhl(-/-) mammary glands exhibited a progressive loss of alveolar epithelium, culminating in lactation failure. Deletion of Vhl in the epithelium also impacted the mammary stroma, as there was increased microvessel density accompanied by hemorrhage and increased immune cell infiltration. However, deletion of Vhl was not sufficient to induce mammary tumorigenesis in dams bred continuously for up to 24 months of age. Moreover, co-deletion of Hif1a could not rescue the Vhl(-/-)-dependent phenotype as dams were unable to successfully lactate during the first lactation. These results suggest that additional VHL-regulated genes besides HIF1A function to maintain the proliferative and regenerative potential of the breast epithelium.

Effects of nursing frequency and parity on the productive, metabolic and reproductive parameters of beef cows

Nursing restriction and parity might be stressful factors influencing the challenging post-partum period. This experiment aimed to evaluate the effects of nursing frequency (in multiparous dams) and parity on faecal glucocorticoid metabolites after calving in beef cows ( n = 64). Also, the role of these effects on productive, metabolic and reproductive functions was assessed. From the day after calving, forty-six Parda de Montaña cows were assigned at random to three nursing frequencies: once-daily nursing (1 × 30 min at 0800 h) (RESTR1), twice-daily nursing (2 × 30 min at 0800 and 1530 h) (RESTR2) and ad libitum nursing (ADLIBC). Eighteen heifers were maintained with free access to their calves as in the ADLIB cow's group (ADLIBH). Data were analysed through analysis of variance and survival analysis. The faecal glucocorticoid metabolites during the first three days post-partum were not affected by either calf management or parity ( P > 0.10) but they were greater at 12 h post-partum than in subsequent samplings ( P < 0.05). Cow average daily gain (ADG) was greater in RESTR1 than in RESTR2 and ADLIBC ( P < 0.05). However, milk yield and calf ADG were lower in RESTR1 than in the rest (P < 0.05). These traits did not differ between parities ( P > 0.10). Serum triglycerides and urea were not affected by calf management or parity ( P > 0.10). Peripheral cholesterol and IGF-I did not differ among suckling systems ( P > 0.10), but their mean concentration was lower in ADLIBC than in ADLIBH ( P < 0.05). Serum NEFA was lower in RESTR1 than in RESTR2 and ADLIBC on weeks 7 and 9 of lactation ( P < 0.05). Both RESTR1 and RESTR2 treatments showed lower serum NEFA than ADLIBC on week 11 post-partum ( P < 0.05). Serum NEFA were greater in ADLIBC than in ADLIBH on week 1 and after week 7 of lactation ( P < 0.05). Serum β-hydroxybutyrate was lower in RESTR1 and RESTR2 than in ADLIBC ( P < 0.05). Calf management did not affect significantly the interval to first post-partum ovulation or oestrus ( P > 0.10) but ADLIBC had shorter post-partum intervals to first ovulation than ADLIBH ( P < 0.05). In conclusion, calf restriction and parity were factors that did not affect cow's welfare after parturition. Twice-daily and ad libitum suckled cows showed a similar productive and metabolic behaviour which differ from their once-daily suckled counterparts. This response did not trigger remarkable differences in the reproductive parameters of cows. Ad libitum suckled cows had different metabolic traits compared to heifers, as well as a shorter duration of the post-partum anoestrus than ad libitum suckled first-calf dams.

The Effect of Parity of the Dam on Sexual Maturation, Serum Concentrations of Metabolic Hormones and the Response to Luteinizing Hormone Releasing Hormone in Bull Calves

The objectives of this study were to determine the effect of parity of the dam on age at which a scrotal circumference (SC) ≥ 28 cm was attained and the LH response to Luteinizing Hormone Releasing Hormone (LHRH) in bull calves. We also wanted to confirm, in a large group of bull calves, that the LH response to LHRH could be used to select early maturing bulls. Body weight and SC of the bull calves were measured every other week. At 15, 20 and 25 weeks of age, calves received 4.12 nm/kg body weight of LHRH ischio-rectally and blood samples were taken every 15 min for 4 h. Calves from primiparous and multiparous dams were separated into two sub-groups based on age at which an SC ≥ 28 cm was attained (early or late). An SC ≥ 28 cm was attained earlier in calves born to multiparous as compared with primiparous dams (p < 0.05). At 20 and 25 weeks of age, peak serum LH concentrations (LH-peak) and area under the LH response curve (LH-AUC) in response to LHRH were higher (p < 0.01) in calves born to multiparous as compared with primiparous dams. In calves born to multiparous dams the LH-peak at 15 and 25 weeks of age and the LH-AUC at 15 weeks of age were lower (p < 0.05) in calves that attained an SC ≥ 28 cm early as compared with late. The LHRH-challenge test sensitivity and specificity ranged from 46% to 86%. We concluded that parity of the dam affected age at which SC ≥ 28 cm was attained and the LH response to LHRH in bull calves. Serum LH responses to LHRH at 15 and 25 weeks of age, in calves born to multiparous dams, show some promise for development into a test to select early maturing bull calves.

Reproductive experience alters corticosterone and CBG levels in the rat dam

Reproductive experience has significant effects on the brain, behavior and hormone profiles of the mother. Recent work has demonstrated that primiparous rats exhibit decreased dendritic arborizations in the hippocampus, and enhanced hippocampus-dependent spatial memory performance at the time of weaning compared to nulliparous and, to a lesser degree, multiparous rats. Interestingly, enhanced spatial learning and reduced dendritic arbors are seen in nulliparous female rats exposed to chronic stress or repeated corticosterone administration. Based on these observations, we hypothesized that corticosterone may be altered in primiparous rats compared to multiparous and nulliparous rats. The present study investigated whether the levels of circulating corticosterone and its binding protein, corticosteroid binding globulin (CBG), are altered with reproductive experience and pup-exposure during late pregnancy and the postpartum. Total serum corticosterone and CBG were assayed from five groups; multiparous, primiparous, nulliparous, primip-no-pups, and sensitized rats during gestation (days 14 and 19) and the postpartum period (days 1, 5, 14, 21, and 35). Results show that primiparous rats had significantly elevated total corticosterone on postpartum day 1. In addition, primiparous and multiparous rats had significantly lower CBG throughout the postpartum period than all other groups, with primiparous rats exhibiting lower levels than multiparous rats during mid-lactation. These data suggest that free corticosterone is elevated in both primiparous and multiparous dams and is elevated to a greater degree in primiparous compared to multiparous dams during lactation. Corticosterone and CBG levels were positively correlated with specific maternal behaviors during the first week postpartum in parturient rats, but not in sensitized rats, suggesting a role for corticosterone in the modulation of maternal behavior in parturient rats alone.

Impacts of Dystocia on Health and Survival of Dairy Calves

The objectives of this study were to determine incidence of stillbirths and heifer-calf morbidity and mortality, and their association with dystocia on 3 Colorado dairies. A total of 7,380 calvings produced 7,788 calves on 3 Colorado dairy operations between October 1, 2001, and November 5, 2002. Dystocia score and calf status (alive vs. dead) were recorded at calving. Calves that were born alive, but died before 24h of age, also were recorded as stillborn. Heifer calves were monitored for 120 d to evaluate morbidity and mortality. More than half (51.2%) of calves born to primiparous dams, compared with 29.4% of calves born to multiparous dams, required assistance during calving. A larger percentage of bull calves (40.0%) required assistance compared with heifer calves (33.0%). Proportion of stillborn calves was 8.2% overall, with bull calves, twin calves, calves born to primiparous dams, and those born to dams having dystocia having a larger stillbirth percentage compared with heifer calves, singletons, calves born to multiparous dams, and unassisted calvings, respectively. Multiple logistic regression models were constructed to evaluate stillbirths and heifer health while accounting for the clustering of calves within dairy. The models included dystocia score, parity, and season of calving as explanatory variables for heifer events and also calf gender, and single or twin birth for the stillbirth models. Heifer calves born to dams having severe dystocia had greater odds of stillbirth [odds ratio (OR) = 20.7] and treatment of respiratory disease (OR = 1.7), digestive disease (OR = 1.3), and overall heifer mortality (OR = 6.7). Calf gender and dam parity interacted with calving ease to affect stillbirths. For calves having severe dystocia, heifer calves and calves born to multiparous dams were at increased risk of stillbirth compared with bull calves and calves born to primiparous dams, respectively. Survival analysis demonstrated that severe dystocia was associated with stillbirths and deaths up to 30 d of age. Relatively simple interventions have the potential to significantly reduce the impact of dystocia on calf mortality and morbidity on dairy farms. Education of farm management and personnel in strategies to reduce dystocia and its effect on calf health should be a priority according to the results of this study.

Influence of the dam and sire on size at birth and subsequent growth, milk production and fertility in dairy heifers

Genetic selection has resulted in larger cows with high milk production potential but a tendency for poor fertility. In multiparous cows fetal development competes for nutrients with concurrent milk production. This study tested the hypotheses that (a) maternal age and milk yield during pregnancy alter calf birth size and (b) birth weight influences subsequent productivity and fertility. Concurrently born Holstein–Friesian heifers ( n = 65) with multiparous dams and three sires were monitored from birth to the end of their first lactation to assess effects of birth weight on growth, milk production and fertility. Calves were analyzed as three subgroups: low (L), average (A) and high (H) birth weight (BW) calves ( n = 21–22 per group). LBW calves were born 10 kg lighter than HBW calves and remained significantly lighter throughout the study. They were generally smaller in other measured indices (length, height, girth, ponderal index) between birth and 9 months and were more likely to have older dams (lactations 3–6) with higher peak yields (>42 kg/day). Milk production parameters were indistinguishable between the 3 birthweight groups and metabolic parameters (IGF-I, insulin, glucose) measured around first calving were unaffected. HBW offspring were more likely to have persistent corpora lutea following their first calving and other fertility parameters also tended to be worse. Sire influenced gestation length but not birth size. Sire heritability estimates showed that weight, IGF-I and insulin concentrations after first calving and fertility in the first lactation were all heritable. The results support the hypothesis that high milk production in the dam may predispose to birth of a smaller calf. Smaller birth size did not, however, have any subsequent adverse effects on productivity or fertility in the first lactation and sire was more influential at this stage.

Organochlorine contaminant exposure and associations with hematological and humoral immune functional assays with dam age as a factor in free-ranging northern fur seal pups ( Callorhinus ursinus)

Potential effects of organochlorine contaminant (OC) exposure on humoral immune function and health of free-ranging northern fur seals were investigated. Forty-two “neonates” were captured for blood sample collection and re-sampled as “pups” 29–51 days later. OCs were extracted from whole blood to identify polychlorinated biphenyl congeners and chlorinated pesticides by high performance liquid chromatography. Humoral immune function was assessed by antibody responses to vaccination and immunoglobulin concentrations. Additional health status indicators included leukocyte counts and haptoglobin concentrations. Mean OC concentrations were higher in neonates than at recapture. Neonates of young dams had higher mean OC concentrations than neonates of older dams. A higher proportion of old dam’s pups developed a twofold or greater increase in antigen-specific antibodies compared to young dam’s pups. Higher OC exposure and poor immune responses in first-born pups may indicate a higher risk of secondary morbidity and mortality than pups of multiparous dams.

Intake and hedonics of calcium and sodium during pregnancy and lactation in the rat

These experiments sought to distinguish whether increased calcium intake during pregnancy and lactation in the rat is due to arousal of a specific calcium appetite, with altered taste hedonics, as occurs with sodium depletion, to reduced taste sensitivity, or to the hyperdipsia of reproduction. We find that, during pregnancy and lactation, CaCl 2 intake is not increased more (in fact less) than intakes of control tastants, MgCl 2 and quinine HCl, and multiparous dams do not have a greater calcium intake than primaparous dams. Changes in taste reactivity to CaCl 2 and to NaCl do not correlate with changes in intake of these minerals during pregnancy or lactation, suggesting that alterations in hedonics or sensitivity do not explain the increased intake of these minerals. Taken together with the increased intake of all the tastants, it may be that the increased intakes of calcium and sodium during reproduction are not due to respective specific appetites or to a general mineral appetite but rather to the reproduction-increased ingestion that may meet all the dam's increased mineral and nutrient requirements. Differences in the degree of increased intakes of tastes may be due to specific alterations in their transduction during reproduction.

A retrospective analysis of factors contributing to calf mortality and dystocia in beef cattle

Records of 2191 calvings from the Clemson University Beef Physiology Unit between 1981 and 1993 were analyzed to determine factors affecting malpresentation, mortality and dystocia. Only 20 (0.91%) parturitions involved malpresentation: posterior presentation (n=14), leg deviations (n=3), head deviations (n=2) and breech birth (n=1). Dystocia affected calf mortality within 24 h of birth (P<0.05), with mortality increasing as the severity of dystocia increased. There was an overall 4.5% death loss within 24 h of birth, with 4 and 7% mortality rates for calves from multiparous and primiparous dams, respectively (P<0.05). Mortality was higher for bull vs heifer calves (P<0.05). Ninety-four percent of calvings were unassisted, while 6% were assisted births. Dystocia was greater (P<0.01) in primiparous (17%) than in multiparous dams (4%). In births involving dystocia, 28.1% required mild traction, 69.3% required heavy traction and 2.6% required Cesarean section. Birth weights associated with normal births and mild traction (36 and 36 kg) were lighter than those associated with heavy traction and Cesarean section (40 and 42 kg, respectively; P<0.05). In conclusion, malpresentations were too few to be of significance, and dystocia influenced mortality within 24 h of birth. Calf birth weight and parity of dam explained most of the observed variations in dystocia.

Gender and parity: Potential sources of variance in ACTH-induced memory reactivation in weanling rats

The effect of ACTH on retention of Pavlovian fear conditioning was investigated in weanling rats. No influence of ACTH on memory was observed in male and female pups of primiparous dams. Male offspring of multiparous dams displayed increased retention with the ACTH reactivation treatment, as indexed by three behavioral measures. Female offspring of multiparous dams, as well as those of primiparous dams, demonstrated linear ACTH dose-dependent increases in vacillatory activity, but no facilitation of memory. Collectively, the present data extend the generality of ACTH-induced memory reactivation to include the attenuation of infantile amnesia, but also suggest that this effect is constrained by gender of the offspring and maternal parity.

Performance of crossbred progeny of Trangie Fertility Merino and Booroola Merino rams and Poll Dorset ewes. 1. Lamb birth weight, survival and growth

Merino rams of the Trangie Fertility and Booroola strains were joined to Poll Dorset ewes in single sire mating groups over 3 years. Forty sires produced a total of 1250 lambs in 885 litters from 451 ewes. Lamb birth weight averaged 4.1 kg, 80.8% of lambs survived to 3 days of age and growth rates to weaning (mean 93 days) averaged 289 g/day. Lambs with Trangie Fertility sires grew 15 g/day faster and were 1.3 kg heavier at weaning than those lambs with Booroola sires (P&lt;0.001). There were no effects of sire strain on birth weight or lamb survival. Birth weight increased with dam liveweight in mid-pregnancy (P&lt;0.001), and weaning weight and growth rate increased with dam liveweight at joining (P&lt;0.001). Survival of lambs was predominantly a function of birth weight. Lambs weighing 4 kg at birth from primiparous dams had survival rates of 76% compared with 88% for lambs from multiparous dams (P&lt;0.01). No lamb under 2.0 or over 6.3 kg survived, and 48% of deaths occurred within 1 day of birth. Dystocia, particularly of heavy, single-born lambs, caused 53% of observed lamb deaths. For the traits birth weight, lamb survival, weaning weight and growth rate, the direct heritabilities were 0.24 � 0.10, 0.05 � 0.05, 0.19 � 0.10 and 0.12 � 0.08 respectively; the corresponding maternal heritabilities were 0.08 � 0.05, 0.05 � 0.04, 0.05 � 0.05 and 0.07 � 0.05 respectively; and the common environmental effects among litter mates (c2) were 0.57 � 0.08, 0.47 � 0.08, 0.15 � 0.08 and 0.13 � 0.08 respectively.

Early Embryo Development in Senescent Golden Hamsters.

Golden hamster embryos were recovered from aged multiparous dams (15 to 16 months old), and young nulliparous females (3 to 4 months old) after mating with fertile males. The numbers of embryos and fetuses were counted at 1-cell, morula or blastocyst, and 8-day stages, respectively. The average number of normal per dam was without significant difference, although slightly larger in young nulliparous females (young group) than in senescent multiparous females (aged group). However, the average number of anomalous per dam increased significantly in the aged group. The average number of the embryos at morula or blastocyst stage per dam was significantly large in the young group. The average numbers of deciduae and fetuses, which were recovered from females at 8 days after mating, decreased significantly in the aged group. The frequency of appearance of mitotic metaphases in first-cleavage embryos decreased significantly in the aged group. These results indicate that the aging of dams causes delay of fertilization, or asynchronous development of embryos and degeneration of the resultant embryos through the embryo development. In senescent golden hamster females, large numbers of unfertilized eggs, shell eggs without cytoplasm, which were previously ovulated and then degenerated, were recovered. They were accumulated in oviducts or uterotubal junctions.

Optimal Breeding Strategies for Calving Ease

Calving ease is of economic importance in dairy cattle and should be considered in breeding programs. Economic values of direct and maternal calving ease were derived based on cost-benefit analysis and gene flow methodology. Marginal returns from dystocia reduction in primiparous dams were −$43 per phenotypic standard deviation compared with $300 for production. For an average mate, numbers of discounted expressions for sires to breed replacements were .58, .44, and .63 for direct and maternal calving ease and production. Discounted expressions for direct calving ease were higher when sires were mated to primiparous versus multiparous dams. Three alternative breeding strategies were compared: 1) separate selection of sires as mates of primiparous and multiparous cows, based on their respective optimal indexes for direct and maternal calving ease, 2) selection based on the optimal index for an average mate, and 3) selection on direct calving ease only. Strategies 2 and 3 allowed for assortative mating of sires with favorable direct calving ease to primiparous females subsequent to selection. Strategy 2 resulted in maximal economic response. Optimal standardized index weights under Canadian circumstances were approximately 100:9:7 for production:direct calving ease:maternal calving ease. Inclusion of calving ease traits had a minor effect (<.5%) on selection responses and efficiency but would provide proper guidelines to producers. Greatest benefits of genetic evaluations for calving ease were obtained through assortative mating.

Cadmium-induced bone loss: Increased susceptibility in females

An overview is presented of studies on effects of Cd on (1) female mice during pregnancy and lactation and after ovariectomy and (2) bone organ/cell culture systems. The gastrointestinal absorption of Cd increased two- to threefold in mouse dams during pregnancy and lactation, with both the kidneys and duodenum of the dam showing striking increases in Cd deposition. Dietary Cd at 5 or 50 μg g−1 caused a dose-dependent decrease in femur Ca content in multiparous mouse dams but not in nonpregnant controls. In addition, dietary Cd at 50 μg g−1 significantly increased the loss of bone mineral that occurs normally in mice after removal of the ovaries. In cultures of fetal rat limb bones prelabeled with 45Ca, Cd at 10 nM (1 ng g−1) caused a release of 70% of the 45Ca, similar to the release caused by 10 nM parathyroid hormone. This level of Cd also caused a fivefold increase in the number of multinucleated osteoclast-like cells formed during invitro incubation of progenitor-enriched mononuclear bone marrow cells. These results support the view that Cd exposure contributed to the pathogenesis of Itai-Itai disease among multiparous, postmenopausal women in Japan and provide evidence that Cd may act directly on bone.

Inheritance of Calf Mortality for Brown Swiss Cattle

Worksheets with reports of calf mortality were voluntarily submitted by dairy producers to the Brown Swiss Cattle Breeders Association. Objective was to assess genetic and nongenetic factors influencing calf mortality of Brown Swiss. Multiple births were removed prior to analysis. Three traits recorded and analyzed were dead at birth, death through 2nd d after birth including dead at birth, and death from 1st to 7th d of life. Male calves were more likely to be dead at birth, to die through 2nd d, and to die from 1st to 7th d of life than female calves. Dead birth was greater for calves from primiparous than multiparous dams; however, death from 1st to 7th d did not differ by parity status of dam. Death from 1st to 7th d was greater from December to May than from June to November. Heritabilities for Brown Swiss were .05, .07, and .04 for dead at birth, dead through 2nd d, and death from 1st to 7th d, respectively. Mortality rates and heritabilities were similar to estimates for Holsteins from the literature. Rank correlations of sires for transmilling abilities of calf mortality and production were near zero.