Parity Dams Research Articles

Early- and mid-lactation milk traits are associated with piglet growth during lactation.

Preweaning piglet growth is tied to milk quality and consumption. To determine the relationship of milk traits from parity 1-4 dams and piglet growth, early- and mid-lactation (day 2 and day 16) milk samples were collected from 48 litters and analyzed for protein, fat, somatic cell count (SCC), lactose, other solids (solids excluding protein and fat), total solids, and milk urea nitrogen (MUN). There were no interactions of parity by day therefore only main effects were tested. Milk volume and percent MUN were greatest (P < 0.05) from fourth parity dams. Nulliparous dams had elevated (P < 0.05) SCC. Several milk traits were different by day. Percent milk protein, fat, and total solids were greater (P < 0.05) from day 2 milk, while percent milk lactose and other solids were greater (P < 0.05) from day 16 milk. Each milk trait was categorically identified as high, moderate, or low at ¼, ½, or ¼ distribution, respectively. Mixed models were used to determine the association of individual milk traits with piglet lactation growth (gain calculated from body weights at birth, day 10, and day 25 weaning; WN). Moderate levels of day 2 milk protein were associated with the greatest (P < 0.05) gain during lactation in comparison to low and high levels. High levels of day 2 milk lactose and day 2 other solids were both related (P < 0.05) to piglet gain over the lactation period. Evaluation of day 16 milk traits with piglet gain over lactation indicated high levels of fat, other solids, and total solids had the greatest (P < 0.05) gain in comparison to moderate and low levels of each trait. Within phase of lactation weight gain, association of day 2 or day 16 milk traits with early weight gain (birth to day 10) or late weight gain (day 10 to WN) were performed. The greatest (P < 0.05) early weight gains were associated with moderate levels of day 2 protein, high levels of day 2 lactose and day 2 other solids, and low levels of day 2 MUN. High levels of day 2 milk lactose and day 16 milk fat were associated (P < 0.05) with piglet gain during late lactation (day 10 to weaning). Genetic selection or improved management that allows for favorable milk traits at critical periods of lactation for improved weight gain will improve pig production.

Dam parity structure and body condition during lactation influence piglet growth and gilt sexual maturation through pre-finishing.

Energy demands during lactation greatly influence sow body condition and piglet performance. We hypothesized that primiparous sows or sows with reduced body condition would produce piglets with reduced growth and delayed sexual maturation. Eight weekly farrowing seasons were used to evaluate sow body condition (post-farrowing, PF and weaning, WN) and piglet growth from 157 dams. Body condition was measured at PF and WN using sow calipers (last rib and hip) and 10th rib ultrasound. Sows were categorized as thin, moderate, or fat by caliper (PF or WN). Individual pig weights were recorded on approximately 1, 10, WN, 45, 100, and 145 d of age. At 100 and 145 d of age, 10th-rib backfat and loin eye area were measured on 567 pigs and first estrus was monitored in 176 gilts reserved for breeding selection beginning at approximately 170 d of age. Sows had similar (P > 0.10) PF last rib caliper measurements but at WN, first parity sows had the smallest caliper measurements compared to other parities (P < 0.05). Parities 1, 2, and 3 sows had similar (P > 0.10) loin eye area at PF; however, at WN first parity sows had the smallest loin eye area (P < 0.05; 38.2±0.63cm2). Parity 1 sows had the greatest (P < 0.05) reduction of backfat and loin eye area over the lactation period (-2.9±0.31mm and -2.6±0.49cm2, respectively). At 1 d of age and WN, piglets from first parity sows weighed the least (P < 0.05) but were the heaviest (P < 0.05) at 100 and 145 d of age. Pigs from first parity litters had larger (P < 0.05) loin eye area at 100 and 145 d of age and greater backfat (P < 0.05) at 145 d of age. Fat sows at WN (last rib or hip) had the lightest (P < 0.05) piglets at 10 d of age and WN. However, at 45 d of age, piglets from fat sows (last rib or hip) were heavier (P < 0.05) than piglets from moderate and thin sows. Tenth rib backfat at 100 and 145 d of age tended (P < 0.10) to be less in pigs reared by thin sows (PF and WN hip). Tenth rib loin eye area was similar among pigs reared by fat, moderate, or thin sows. Gilts developed in litters from fourth parity sows had (P < 0.05) delayed age at puberty in contrast to gilts from first or third parity sows (200.9±4.96 d vs. 189.0±2.29 d and 187.5±2.84 d, respectively). Although progeny body weights were typically less from first parity dams through 45 d of age, these progeny were similar or heavier at 100 and 145 d of age in contrast to progeny from other parities. Furthermore, gilt progeny from first parity dams did not have delayed pubertal attainment.

Effect of housing improvement and other factors on the growth of heifer calves on Kenyan smallholder dairy farms.

This trial evaluated average daily gain (ADG) effects of heifer calves (< 1year old) from affordable housing improvements to the roof and flooring on 150 randomly allocated smallholder dairy farms. During the 16-month data collection period, bimonthly farm visits were used to measure weight and other animal- and farm-level factors on the 187 study calves. Multivariable linear regression was used to model ln ADG and ADG during pre-weaning and post-weaning periods, respectively. Median pre-weaning and post-weaning ADGs were 0.307 (interquartile range (IQR): 0.227-0.398) and 0.487 (IQR: 0.354-0.675) kg/d, respectively. In the final pre-weaning model (p<0.050), factors positively associated with ln ADG were calf age at first acaricide application, and total number of calf pens, while factors negatively associated with ln ADG included calf mortality risk over the last 5years and calf age at first ad lib access to water. In an interaction term, for calves from parity 3+ dams, ADG was lower when milk was fed twice/day than thrice/day, with no difference in calves of lower parity dams. In the final post-weaning model, housing improvements increased ADG by 5.6%. Other factors positively associated with post-weaning ADG were feeding of calf pellets, wheat bran, maize bran, and hay. Calf age at first introduction of concentrate and calf mortality risk over the last 5years were negatively associated with ADG. In an interaction term, ADG was high when there were faecal coccidia oocysts and when calves had visual or physical contact with their dams, but low when faecal coccidia cysts were present, and these dam-calf connections were absent. In a second interaction term, ADG increased with more calf pens for female principal farmers, while remaining low for male principal farmers. In conclusion, while controlling for other factors of ADG, making affordable calf housing improvements enhanced ADG, particularly during the post-weaning period.

Phenotypic factors associated with lamb live weight and carcass composition measurements in an Irish multi-breed sheep population.

Understanding the phenotypic factors that affect lamb live weight and carcass composition is imperative to generating accurate genetic evaluations and further enables implementation of functional management strategies. This study investigated phenotypic factors affecting live weight across the growing season and traits associated with carcass composition in lambs from a multibreed sheep population. Four live weight traits and two carcass composition traits were considered for analysis namely; birth, preweaning, weaning, and postweaning weight, and ultrasound muscle depth and fat depth. A total of 427,927 records from 159,492 lambs collected from 775 flocks between the years 2016 and 2019, inclusive were available from the Irish national sheep database. Factors associated with live weight and carcass composition were determined using linear mixed models. The heaviest birth, preweaning, and weaning weights were associated with single born lambs (P < 0.001), however by postweaning, there was no difference observed in the weights of single and twin born lambs (P > 0.01). Breed class affected lamb live weight and carcass composition with terminal lambs weighing heaviest and having greater muscle depth than all other breed classes investigated (P < 0.001). Lambs born to first parity dams were consistently lighter, regardless of time of weighing (P < 0.001), while dams lambing for the first time as ewe lambs produced lighter lambs than those lambing for the first time as hoggets (P < 0.001). Greater heterosis coefficients (i.e., >90% and ≤100%) resulted in heavier lambs at weaning compared with lambs with lower levels of heterosis coefficients (P < 0.001). A heterosis coefficient class <10% resulted in lambs with greater muscle depth while recombination loss of <10% increased ultrasound fat depth (P < 0.001). Results from this study highlight the impact of multiple animal level factors on lamb live weight and carcass composition which will enable more accurate bio-economic models and genetic evaluations going forward.

Etio-Epidemiological Studies on Diarrhoea in Cattle and Buffalo Calves

Calf diarrhoea is the most commonly encountered disease syndrome and significant cause of economic losses in dairy industry. Present investigation was undertaken to find out the prevalence of causative agents of diarrhoea in the bovine calves for a period of one year. The effect of age, sex, season and parity of dam was also studied. E. coli was the major organism (86.00 %) observed in the faecal samples of the diarrhoeic calves followed by rotavirus, Eimeria spp. and Amphistomes (15.00 % each); Toxocara spp. (12.00 %); Strongyles (9.00 %); Cryptosporidium spp. (6.00 %); Trichuris spp. (5.00 %); and Salmonella spp. and Strongyloides spp. (3.00 % each). The prevalence of rotavirus, Cryptosporidium spp. and Eimeria spp. was found significantly higher in buffalo calves and crossbred calves than cow calves and Gir / local non-descript calves, respectively. The prevalence of Toxocara spp., Amphistomes and Strongyles in diarrhoeic buffalo calves was significantly higher than cow calves. Highest prevalence of E. coli and rotavirus was observed in faecal samples of diarrhoeic calves of 0-15 days age group. Rotavirus was not detected in faecal samples of diarrhoeic calves above 60 days age. The susceptibility of bovine calves for E. coli and rotavirus was found decreased with the advancement of the age. The prevalence of Salmonella spp. in diarrhoeic faecal samples of bovine calves was observed only in 16-60 days age whereas Cryptosporidium spp. was found only in 0-30 days age. The most of the parasitic infestations were observed after 30 days of age in calves. The calves of both sexes were equally susceptible to different causative agents of diarrhoea. The prevalence of E. coli and most of the helminth ova in the faecal samples of diarrhoeic calves was found maximum during rainy season whereas the rotavirus was observed mostly during winter season. The prevalence of E. coli, Salmonella spp., rotavirus and Cryptosporidium spp. was found highest in the faecal samples of the diarrhoeic calves of first or second parity dams.

Mycoplasma hyorhinis and Mycoplasma hyosynoviae dual detection patterns in dams and piglets.

Mycoplasma hyorhinis and M. hyosynoviae are agents associated with arthritis in pigs. This study investigated the tonsillar detection patterns of M. hyorhinis and M. hyosynoviae in a swine population with a history of lameness. The plausibility of dual PCR detection of these agents in dams at one and three weeks post-farrowing and their offspring at the same time was determined. The association between M. hyorhinis and M. hyosynoviae detection in piglets and potential development of lameness in wean-to-finish stages was evaluated by correlating individual piglet lameness scores and PCR detection in tonsils. Approximately 40% of dams were detected positive for M. hyorhinis and M. hyosynoviae at both one and three weeks post-farrowing. In first parity dams, M. hyorhinis was detected in higher proportions (57.1% and 73.7%) at both weeks of sampling compared to multi-parity dams. A lower proportion of first parity dams (37.5%) were detected positive at week one with M. hyosynoviae and an increase in this proportion to 50% was identified in week three. Only 8.3% of piglets were detected positive for M. hyorhinis in week one compared to week three (50%; p<0.05). The detection of M. hyosynoviae was minimal in piglets at both weeks of sampling (0% and 0.9%). Lameness was scored in pigs 5–22 weeks of age, with the highest score observed at week 5. The correlation between PCR detection and lameness scores revealed that the relative risk of developing lameness post-weaning was significantly associated with detection of M. hyorhinis in piglets at three weeks of age (r = 0.44; p<0.05).The detection pattern of M. hyorhinis and M. hyosynoviae in dams did not reflect the detection pattern in piglets. Results of this study suggest that positive detection of M. hyorhinis in piglets pre-weaning could act as a predictor for lameness development at later production stages.

Impact of birth and rearing type, as well as inaccuracy of recording, on pre-weaning lamb phenotypic and genetic merit for live weight.

The objective of the present study was to quantify the impact of the systematic environmental effects of both birth and rearing type on pre-weaning lamb live weight, and to evaluate the repercussions of inaccurate recording of birth and rearing type on subsequent genetic evaluations. A total of 32,548 birth weight records, 35,770 forty-day weight records and 32,548 records for average daily gain (ADG) between birth and 40-day weight from the Irish national sheep database were used. For each lamb, a new variable, birth-rearing type, reflecting both the birth and rearing type of a lamb was generated by concatenating both parameters. The association between birth-rearing type and birth weight, 40-day weight, and ADG was estimated using linear mixed models. The repercussions of inaccurate recording of birth type were determined by quantifying the impact on sire estimated breeding value (EBV; with an accuracy of ≥ 35%), where one of the lambs born in a selection of twin litter births was assumed to have died at birth but the farmer recorded the birth and rearing type as a singleton. The heaviest mean birth weight was associated with lambs born and subsequently reared as singles (5.47 kg); the lightest mean birth weight was associated with lambs born and reared as triplets (4.10 kg). The association between birth-rearing type and 40-day weight differed by dam parity (P < 0.001). Lambs reared by first parity dams as singles, irrespective of birth type were, on average, heavier at 40-day weighing than lambs reared as multiples, but as parity number increased, single-born lambs reared as twins outperformed triplet-born lambs reared as singles. Irrespective of the trait evaluated, the correlation between sire EBV estimated from the accurately recorded data and sire EBV estimated from the data with recording errors was strong ranging from 0.93 (birth weight) to 0.97 (ADG). The EBV for sires with progeny data manipulated were 0.14 kg, 0.34 kg and 5.56 g/d less for birth weight, 40-day weight and ADG, respectively, compared to their equivalent EBV calculated using accurately recorded data. Results from this study highlight the importance of precise recording of birth-rearing type by producers for the generation of accurate genetic evaluations.

Measurements of body composition during late gestation and lactation in first and second parity sows and its relationship to piglet production and post-weaning reproductive performance

The objective of this study was to characterize multiple body condition traits in a white crossbred composite population of first- and second-parity sows and, determine if these traits relate to litter production and reproductive parameters. Differences between parity or time were determined using a mixed model and reported as LSM±SE. As expected, parity 2 dams were heavier (P<0.0001; 202.5±1.57kg versus 174.1±1.35kg) than parity 1 dams. Of interest however, parity 2 dams lost more (P=0.0340) loin eye area from late gestation to weaning (−4.1±0.78cm2 versus −2.5±0.60cm2) but had a greater (P=0.0026) recovery in loin eye area from weaning to post-weaning (2.8±0.76cm2 versus 0.6±0.59cm2) versus primiparous females. However the period between weaning measurements and post-weaning measurements tended (P=0.0978) to favor parity 1 dams (16.0±0.35d) versus parity 2 dams (15.4±0.43d). Parity 2 dams also had a greater (P≤0.05) ovulation rate following weaning than parity 1 dams. Regression analyses indicated body weight of dams at several time points had a positive (P≤0.05) relationship to ovulation rate (range 0.03±0.012 to 0.05±0.013corpora luteakg−1). Piglet ADG was positively (P≤0.05) associated with dam body weight (range 0.30±0.103gkg−1 to 0.49±0.106gkg−1) and dam backfat thickness (range 0.93±0.363gmm−1 to 1.14±0.378gmm−1) regardless of parity. Regression analyses indicated interactions (P≤0.05) between parity and backfat thickness at weaning (−0.11±0.023pigletsmm−1) and post-weaning backfat thickness (−0.12±0.025pigletsmm−1) were negatively associated with number of nursed piglets weaned among parity 1 dams. Furthermore, loin eye area at weaning (−0.06±0.024pigletscm2 −1) and loss of loin eye area from late gestation to weaning (−0.05±0.020pigletscm2 −1) were negatively (P≤0.05) associated with number of nursed piglets weaned but were not influenced by parity in regression analyses. In conclusion, these data provide knowledge on differences in body composition before and after the lactation period in young dams under similar conditions. Of interest, second parity dams appear to have greater lean tissue elasticity versus primiparous females. Future studies will further refine the relationship among body composition in primiparous females and subsequent impact on sow longevity.

Effect of dam parity on litter performance, transfer of passive immunity, and progeny microbial ecology1

Litter performance and progeny health status may be decreased in progeny derived from primiparous sows but improve with increasing parity. The objective was to evaluate litter performance, the production and passive transfer of Ig, and fecal microbial populations in progeny derived from first parity (P1) compared with fourth parity (P4) dams. Litter performance was recorded for P1 (n = 19) and P4 (n = 24) dams including number of pigs/litter (total born, born live, stillbirths, mummified fetuses, prewean mortality, and pigs weaned) and average litter and piglet BW at birth (d 0), d 7, d 14, and at weaning (average d 19). Blood samples were collected from all dams on d 90 and 114 of gestation and d 0 of lactation. Colostrum and milk samples were collected from each dam on d 0, 7, and 14 of lactation for quantification of IgG and IgA. Blood and fecal samples were collected from each litter (n = 6 pigs/litter) on d 1, 7, and 14 after parturition. Circulating IgG and IgA concentrations were quantified in all blood samples. Denaturing gradient gel electrophoresis (DGGE) was used to characterize similarity and diversity of fecal microbes among progeny. Progeny of P1 dams had decreased average litter BW at d 7 (25.7 vs. 30.0 kg; P < 0.03) and decreased average piglet BW throughout the experiment (d 0, 7, 14, and 19; P < 0.001) compared with P4 progeny. No parity × day interactions were observed with respect to immunoglobulin or microbial analyses. Concentrations of IgA tended to be greater (P = 0.09) in samples of colostrum and milk obtained from P4 compared with P1 dams. Serum IgG concentrations were greater (P < 0.02) in P4 progeny compared with P1 progeny. Results of DGGE revealed that P1 progeny had increased (P < 0.001) microbial similarity on d 7 and decreased (P < 0.03) microbial similarity on d 14 compared with P4 progeny. Progeny of P1 dams tended (P = 0.07) to have a greater Shannon's diversity index compared with P4 progeny on d 1, and P1 progeny had a greater (P < 0.03) Shannon's diversity index compared with P4 progeny on d 7. Litter performance, passive transfer of immunity, and progeny microbial ecology were affected by dam parity.

Direct and maternal genetic effects for body weight and price of calves sold for veal production1

The aim of this study was to estimate direct and maternal genetic parameters for age at sale (AS, d), BW (kg), price (PR, €/kg), and market value (MV, €/calf) of Brown Swiss male calves (Bos taurus) from first- (n = 6,719) and second- (n = 4,405) parity dams marketed at livestock auctions from 2003 to 2007, and destined for veal production. Market value was calculated as the product of PR and BW. Restricted maximum likelihood procedures incorporating multiple trait animal models were used to infer genetic parameters for AS, BW, and PR, whereas estimates for MV were from single trait models. Bivariate analyses treating performance of calves from first- and second-parity cows as different traits were also performed. Direct heritabilities for AS, BW, and cattle prices ranged from 0.046 to 0.090, 0.078 to 0.130, and 0.064 to 0.152, respectively, and the corresponding maternal heritabilities varied from 0.020 to 0.030, 0.036 to 0.079, and 0.020 to 0.045, respectively. Direct genetic correlations between the traits were generally moderate to high and negative, whereas direct-maternal relationships were moderate to low. Genetic correlation between the same trait recorded on calves from first- and second-parity dams was less than unity, but generally high and positive, suggesting that AS, BW, PR, and MV can be treated as the same traits across parities. As calf price is routinely collected at auctions and shows genetic variation, it can be genetically improved.

A general approach to mixed effects modeling of residual variances in generalized linear mixed models

We propose a general Bayesian approach to heteroskedastic error modeling for generalized linear mixed models (GLMM) in which linked functions of conditional means and residual variances are specified as separate linear combinations of fixed and random effects. We focus on the linear mixed model (LMM) analysis of birth weight (BW) and the cumulative probit mixed model (CPMM) analysis of calving ease (CE). The deviance information criterion (DIC) was demonstrated to be useful in correctly choosing between homoskedastic and heteroskedastic error GLMM for both traits when data was generated according to a mixed model specification for both location parameters and residual variances. Heteroskedastic error LMM and CPMM were fitted, respectively, to BW and CE data on 8847 Italian Piemontese first parity dams in which residual variances were modeled as functions of fixed calf sex and random herd effects. The posterior mean residual variance for male calves was over 40% greater than that for female calves for both traits. Also, the posterior means of the standard deviation of the herd-specific variance ratios (relative to a unitary baseline) were estimated to be 0.60 ± 0.09 for BW and 0.74 ± 0.14 for CE. For both traits, the heteroskedastic error LMM and CPMM were chosen over their homoskedastic error counterparts based on DIC values.

A general approach to mixed effects modeling of residual variances in generalized linear mixed models

We propose a general Bayesian approach to heteroskedastic error modeling for generalized linear mixed models (GLMM) in which linked functions of conditional means and residual variances are specified as separate linear combinations of fixed and random effects. We focus on the linear mixed model (LMM) analysis of birth weight (BW) and the cumulative probit mixed model (CPMM) analysis of calving ease (CE). The deviance information criterion (DIC) was demonstrated to be useful in correctly choosing between homoskedastic and heteroskedastic error GLMM for both traits when data was generated according to a mixed model specification for both location parameters and residual variances. Heteroskedastic error LMM and CPMM were fitted, respectively, to BW and CE data on 8847 Italian Piemontese first parity dams in which residual variances were modeled as functions of fixed calf sex and random herd effects. The posterior mean residual variance for male calves was over 40% greater than that for female calves for both traits. Also, the posterior means of the standard deviation of the herd-specific variance ratios (relative to a unitary baseline) were estimated to be 0.60 ± 0.09 for BW and 0.74 ± 0.14 for CE. For both traits, the heteroskedastic error LMM and CPMM were chosen over their homoskedastic error counterparts based on DIC values.

Cumulative t-link threshold models for the genetic analysis of calving ease scores

In this study, a hierarchical threshold mixed model based on a cumulative t-link specification for the analysis of ordinal data or more, specifically, calving ease scores, was developed. The validation of this model and the Markov chain Monte Carlo (MCMC) algorithm was carried out on simulated data from normally and t4 (i.e. a t-distribution with four degrees of freedom) distributed populations using the deviance information criterion (DIC) and a pseudo Bayes factor (PBF) measure to validate recently proposed model choice criteria. The simulation study indicated that although inference on the degrees of freedom parameter is possible, MCMC mixing was problematic. Nevertheless, the DIC and PBF were validated to be satisfactory measures of model fit to data. A sire and maternal grandsire cumulative t-link model was applied to a calving ease dataset from 8847 Italian Piemontese first parity dams. The cumulative t-link model was shown to lead to posterior means of direct and maternal heritabilities (0.40 ± 0.06, 0.11 ± 0.04) and a direct maternal genetic correlation (-0.58 ± 0.15) that were not different from the corresponding posterior means of the heritabilities (0.42 ± 0.07, 0.14 ± 0.04) and the genetic correlation (-0.55 ± 0.14) inferred under the conventional cumulative probit link threshold model. Furthermore, the correlation (> 0.99) between posterior means of sire progeny merit from the two models suggested no meaningful rerankings. Nevertheless, the cumulative t-link model was decisively chosen as the better fitting model for this calving ease data using DIC and PBF.

Cumulative t-link threshold models for the genetic analysis of calving ease scores

In this study, a hierarchical threshold mixed model based on a cumulative t-link specification for the analysis of ordinal data or more, specifically, calving ease scores, was developed. The validation of this model and the Markov chain Monte Carlo (MCMC) algorithm was carried out on simulated data from normally and t4 (i.e. a t-distribution with four degrees of freedom) distributed populations using the deviance information criterion (DIC) and a pseudo Bayes factor (PBF) measure to validate recently proposed model choice criteria. The simulation study indicated that although inference on the degrees of freedom parameter is possible, MCMC mixing was problematic. Nevertheless, the DIC and PBF were validated to be satisfactory measures of model fit to data. A sire and maternal grandsire cumulative t-link model was applied to a calving ease dataset from 8847 Italian Piemontese first parity dams. The cumulative t-link model was shown to lead to posterior means of direct and maternal heritabilities (0.40 ± 0.06, 0.11 ± 0.04) and a direct maternal genetic correlation (-0.58 ± 0.15) that were not different from the corresponding posterior means of the heritabilities (0.42 ± 0.07, 0.14 ± 0.04) and the genetic correlation (-0.55 ± 0.14) inferred under the conventional cumulative probit link threshold model. Furthermore, the correlation (> 0.99) between posterior means of sire progeny merit from the two models suggested no meaningful rerankings. Nevertheless, the cumulative t-link model was decisively chosen as the better fitting model for this calving ease data using DIC and PBF.

Relationship between litter size and perinatal and pre-weaning survival in pigs

AbstractThe objective of this study was to analyse the relationship between direct and maternal genetic effects on litter size and piglet survival. The analyses were performed on records from 26 564 Landrace litters and 15 103 Yorkshire litters from first parity dams in Finnish herds. The trivariate model fitted total number of piglets born, proportion alive at birth and proportion survived from birth until 3 weeks as traits of the litter. The model included direct genetic and maternal genetic effects for all traits. In Landrace pigs, maternal heritabilities were estimated to be 0·11 for total number born, 0·06 for proportion alive at birth, and 0·08 for proportion survived from birth until 3 weeks. The corresponding estimates for the Yorkshire breed were 0·14, 0·06 and 0·01. All heritability estimates of direct effects were below 0·05. In the Landrace breed, there was a negative correlation of -0·39 between maternal genetic effects on total number born and maternal genetic effects on proportion survived from birth until 3 weeks and a negative correlation of -0·41 between direct and maternal genetic effects on proportion survived from birth until 3 weeks. These correlations were not significant in the Yorkshire breed. The results show that selection for number born in total alone will lead to a deterioration in the maternal ability of sows. Selection for pre-weaning survival could be achieved by selecting on direct and maternal components jointly.

Effects of twinning on gestation length, retained placenta, and dystocia.

Constraints to maximal productivity from twinning in beef cattle include increased incidence of dystocia and retained placenta, longer postpartum interval, and lower conception rate. Incidence and cause(s) of the shorter gestation length and of the increased retained placenta and dystocia associated with twinning were evaluated for 3,370 single and 1,014 twin births produced in a population of cattle selected for natural twin births. Gestation length was shorter for twin than for single pregnancies (275.6 vs. 281.3 d, P<.01) and likely contributed to the higher incidence of retained placenta associated with twin births (27.9 vs. 1.9%; P<.01). Incidence of retained placenta was also higher in the spring (March-April) than in the fall (August-September) calving season (18.3 vs. 11.4%; P<.01). The higher incidence of dystocia with twins than with singles (46.9 vs. 20.6%, P<.01) was primarily due to abnormal presentation (37.0 vs. 4.5%, respectively) of one or both twin calves at parturition. First- (40.5%) and second- (22.7%) parity dams with a single birth had more (P<.01) dystocia than older dams (13.4%), whereas dystocia was not affected (P>.10) by parity with twin births. Because of the shorter gestation length and the increased incidence of retained placenta and(or) dystocia, achievement of increased productivity with twinning in cattle necessitates intensive management of twin-producing dams and their calves during the calving season. Management of the increased dystocia can be facilitated by preparturient diagnosis of twin pregnancies, enabling timely administration of obstetrical assistance to facilitate delivery of twin calves and to increase their neonatal survival.

Risk factors for respiratory disease mortality in lambs

A retrospective cohort study used records from a large flock of sheep in Illinois, USA in logistic regression models to identify risk factors for respiratory disease mortality (RM) in lambs born from 1986 to 1991 ( n = 6806). The flock of several purebred and crossbred lines was intensively managed in open-front barns from birth to weaning (56 days) and fattened in slotted-floor barns. Annual postnatal mortality ranged from 12% to 19% of lambs born. Potential risk factors examined were gender, lamb breed, birth weight, lambing location, number of siblings at birth and rearing, birth vigor, and the dam's parity, milk supply and udder condition. RM occurred in 4.3% of lambs that survived the first 24 h after birth, and this rate was fairly stable over all years of the study (3.3–5.0%). One model compared RM cases with all lambs surviving the first day of age and a second model compared RM cases with all lambs surviving to weaning (56 days of age). In the first model, there was increased risk for RM in ram lambs (OR = 1.9), purebred Suffolks (OR = 2.0), lambs from first parity dams (OR = 1.9), and lambs from dams with poor milk production (OR = 2.2). Lambs with average birth weight were at slightly lower risk for RM than light or heavy weight lambs (OR = 0.8). The second model identified similar factors, with ram lambs, Suffolks, and lambs from dams at first parity or with poor milk supply at increased RM risk (OR = 2.0, 2.3, 2.0, and 2.3, respectively) and average weight lambs at lower risk for RM (OR = 0.7). A strong birth vigor reduced risk for RM (OR = 0.7). Variables not included in final models included lambing location, number of siblings at birth/rearing, and the dam's udder condition. Although factors such as breed and gender may not generally be manipulated to decrease RM, other factors such as birth weight and the dam's milking ability can be improved to reduce respiratory disease mortality. Awareness of variations in RM risk within a population can enhance early response to potential outbreaks, reducing losses.

Behavioral patterns and proximate reason of young male separation in Misaki feral horses

The present investigation was undertaken to study the proximate reasons why and the behavioral patterns of young male Misaki feral horses when they left their natal band or mothers. We observed a total of ten young males twice a month from January 1988 to December 1995. Almost all young males left their natal band or mothers at between 1 and 4 years of age. We found that, during the separation process, all the young males from first parity dams returned several times after the initial separation, indicating a strong attachment between primiparous mares and their male offspring. The other five separated only once without rejoining. Our observations showed five variable behavior patterns of young males at separation time, depending on the consort relation between their mothers and harem stallion and the reason for separation at that time. Eight young males separated in the non-breeding season at average 2.1 years and the other two separated in the breeding season at average 3 years and the average difference was not significant. These results revealed that 80% of the young males separated voluntarily when the natural resources become poor whereas 20% separated when their siblings were born.

Genetic Analysis of Growth Patterns of Black and White Dairy Heifers

Monthly BW to 600 d of age along with BW at first calving of 743 heifers were analyzed to estimate the genetic relationship between BW at first calving and other growth variables. The Von Bertalanffy function and a two-phase logistic function were used to fit growth patterns of individual heifers. The two-phase logistic function fitted the data more adequately than did the Von Bertalanffy function. Calves from first parity dams were born at a lower degree of maturity than calves from third parity dams. Calves with a high proportion of Holstein genes had a higher BW both at first calving and at maturity. Heritabilities of the variables of the Von Bertalanffy and the two-phase logistic function ranged from 0.02 to 0.31 and 0.15 to 0.26, respectively. Estimated mature BW had a highly negative correlation with rate of maturation (–0.56 to –0.82); BW at first calving had a high genetic correlation (0.74 to 0.90) with estimated mature BW and a negative correlation with maturation rate (–0.18 to –0.40). Results of this study indicated that BW at first calving can be used as an indirect trait when mature BW is included in the breeding goal.

Genetic parameters for body weight and growth in Dutch Black and White replacement stock

Abstract Genetic parameters for body weight and growth were estimated using data on 631 Black and White growing dairy heifers, from 60 sires, and born between 1982 and 1990. Body weights were collected monthly and by linear interpolation adjusted to weights at 10, 20, 30, 40 and 50 weeks of age, at breeding, at 26 and 13 weeks before calving and at calving. Also weight at 2 days after calving was recorded. Heifers were fed a restricted amount of concentrate and ad libitum roughage. Data were analyzed using an animal model, considering year-season, parity of dam, and genetic group as fixed effects. Average age and weight at calving were 733 days and 508 kg, respectively. Unadjusted average daily gains from birth to 50 weeks of age and from breeding to calving were 731 (SD 68) and 527 (SD 107) g day −1 , respectively. Heifers born from second and third parity dams were on average 3.1 and 5.2 kg heavier than heifers born from first parity dams. Heifers with > 80–100% HF genes were nearly 30 kg heavier at calving than 100% DF heifers. Heritabilities for body weights ranged from 0.41 to 0.64. Growth from birth to 50 weeks had a heritability of 0.48, while growth during pregnancy had a heritability of 0.19.