Artificial insemination increases the probability of a male calf in dairy and beef cattle

The objective of this study was to determine if natural mating affected secondary sex ratio. Data consisting of 642,401 calving records from the Irish national database, during the years 2002-2005, were used in the analysis. Factors affecting the logit of the probability of a male calf being born were determined using multiple regression generalised estimating equations with sire of the calf included as a repeated effect. Month of the year at calving, sex of the previous calf born within dam, breed of service sire, parity of dam and type of mating (i.e., natural or artificial insemination) significantly (P<0.05) affected the likelihood of a male calf being born. Male calves were more likely to be born in the warmer months of the year, when the sex of the previous calf born to the same dam was male, in older cows and when the service sire was a beef breed. No significant interaction between the main effects existed. The odds of a male calf being born, following adjustment for confounding effects, varied from 1.04 to 1.08 (P<0.01) across the years of analysis when artificial insemination was used compared to natural mating. This equates to a 1% unit increase in the probability of a male calf being born following artificial insemination.     

Factors contributing to dystocia due to fetal malpresentation in beef cattle

Records on 3873 calvings over a 21-year period (1971 to 1991) from the Colorado State University Resident Instruction beef cattle herd were used to examine factors associated with malpresentations at birth. Approximately 82% of the calvings were unassisted and 18% were assisted in some manner. Of the assisted deliveries, severe traction, mild traction, malpresentation and caesarean section accounted for 44.5, 31.8, 22.4 and 1.3%, respectively, of the total. Ninety-six percent of all births were normal presentations and 4% were malpresentations. The incidence of malpresentations was affected by year, sex of calf, and sire of calf within breed. Most of the malpresentations were in the posterior dorsal position (72.8%) followed by unilateral carpal or shoulder flexion (11.4%), breech (8.2%), lateral deviation of the head (2.5%), incomplete extension of the elbow (1.9%), posterior ventral (1.3%), transverse (1.3%) and oblique ventro-vertical (0.6%). Factors influencing the incidence of posterior dorsal presentations were year, sex of calf, sire of calf within breed, and age of dam. Malpresentation heritability estimates as traits of the calf were 0.088 and 0.003 for Hereford and Angus breeds, respectively. Posterior presentation heritability estimates for Hereford and Angus cattle were 0.173 and 0.0, respectively. Heritabilities as traits of the dam and repeatabilities for malpresentation, and posterior presentation were minimal.     

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.     

Factors affecting length of gestation and birth weight of Nili-Ravi buffaloes

This study was conducted to determine the effects of various factors on gestation length and calf birth weight of Nili-Ravi buffaloes in Pakistan. Records were analyzed from 421 uneventful calvings by 274 buffaloes inseminated artificially from 1980 to 1984. Gestation averaged 308.7±0.4 days and ranged from 275 to 346 days in length. Most (57.2%) buffaloes calved from 305 to 314 days after insemination. Calf birth weight, sire of calf, month of breeding, and month of calving accounted for significant amounts of variation in lengths of gestation. Gestation length changed quadratically with calf birth weight. Buffaloes producing calves weighing about 35 kg had the shortest (about 308 days) gestation period, and buffaloes producing calves weighing either more or less than 35 kg had longer gestation periods. Calf birth weight averaged 38.2 ± 0.2 kg and ranged from 17 to 48 kg. Bull calves were heavier at birth than were heifer calves (39.0 vs. 37.5 kg). Calf birth weight increased quadratically with body weight of the dam at calving. Heavier dams produced heavier calves, and body weight of the dam at calving increased with age of the dam at calving. This study indicates that sires, dams and months of breeding could be selected to help control gestation length and birth weight of Nili-Ravi buffaloes.     

Estimation of genetic associations between reproduction and production traits based on a sire and dam line with common ancestry

Genetic parameters for survival, reproduction and production traits were estimated for a sire and dam line, originating from one Large White breed separated more than 25 years ago. The change in parameters due to different selection pressure on reproduction and production traits in both lines was also examined. Data collected between 1990 and 2007 were available for the analysis of reproduction traits in 4713 litters (sire line) and 14836 litters (dam line) and for the production traits in 58329 pigs (sire line) and 108912 pigs (dam line). Genetic parameters were estimated using a Bayesian approach. Average phenotypic differences between lines were substantial with 1.5 more piglets born in the dam line and 1.7 mm less backfat thickness (BF) in the sire line. Based on a multiple trait analysis which included both reproduction and production traits, heritabilities for survival and litter size traits in the sire (or dam) line were estimated at 0.03 ± 0.01 (0.06 ± 0.01) for percentage of stillborn piglets (SB), 0.10 ± 0.03 (0.11 ± 0.01) for total number of piglets born (NBT) and 0.09 ± 0.03 (0.09 ± 0.01) for number of piglets born alive. Heritabilities for production traits were estimated at 0.29 ± 0.01 (0.29 ± 0.01) for average daily gain, 0.50 ± 0.01 (0.42 ± 0.01) for BF and 0.41 ± 0.01 for muscle depth. Selection pressure on litter size in the dam line resulted in a slightly unfavourable correlation for SB-NBT (0.21 ± 0.11), which was only marginally unfavourable in the sire line (0.06 ± 0.24). Selection pressure on BF in the sire line may have resulted in the moderately undesirable correlation with SB (-0.46 ± 0.15), which was not significant in the dam line (-0.08 ± 0.06). Changing the base population in the dam line to animals born since the year 2000 indicated that selection pressure on different traits has altered the heritabilities and correlations of the traits within the line. The undesirable correlations between survival at birth and reproduction traits or production traits were low so that simultaneous improvement of all traits can be achieved. Heritabilities for survival at birth and reproduction traits were low, but genetic variation was substantial and extensive pedigree information can be used to improve the accuracy of breeding values, so that genetic improvement is expected to be efficient.     

Analysis of body measurements of newborn purebred Belgian Blue calves

At calving, purebred animals of the Belgian Blue (BB) breed are compromised by the incompatibility in size and shape of the dam and her calf, resulting in a very high incidence of dystocia problems. To clarify which body parts of the calf are of decisive importance to allow natural delivery and to investigate both the mean value as well as the variation among these body sizes within this breed (variation being an important condition for selection), measurements of nine body parts (body weight at birth (BW), body length (BL), length of the head (LH), shoulder width (SW), hip width (HW), heart girth (HG), withers height (WH) and the circumference of the fetlock of both the front (CFF) and the hind leg (CFH)) were assessed in 147 newborn purebred BB calves on 17 farms. Simple and partial correlations were assessed and we examined whether environmental factors (gender of the calf, parity of the cow, type of calving, season of birth and time of measurement after birth) were significantly associated with these specific calf measurements. The mean BW was 49.2 ± 7.1 kg. The average BL was 56.4 ± 4.5 cm and the mean LH was 24.4 ± 2.3 cm. Measurements obtained for SW and HW were 22.4 ± 2.2 and 22.9 ± 2.1 cm, respectively, whereas the mean WH was 71.1 ± 4.7 cm. Measurements of circumferences revealed a CFF of 17.9 ± 1.1 cm, a CFH of 18.0 ± 1.0 cm and a mean HG of 78.0 ± 5.4 cm. Partial correlations of the BW with eight body measurements were significant (P < 0.01) and ranged between 0.17 and 0.85; 0.42 and 0.88; and 0.24 and 0.88 when corrected for gender, parity and type of calving, respectively. BL (P < 0.01) and the CFF and CFH (P < 0.001) are larger in bull calves than in heifer calves. Calves born through caesarean section had broader SW (P < 0.01) and HW (P < 0.01) when compared with calves born after natural calving (defined as born per vaginam without assistance or with slight traction). Sizes of calves born out of multiparous cows were generally larger than of calves born out of heifers (SW: P < 0.001; HW: P < 0.05). As SW and HW are the broadest points of a BB calf, they are both candidates for being the limiting measures for calving ease, but the difference between HW and SW for the total data set was not different from zero (P > 0.05). In contrast to male calves in which no significant difference (between HW and SW) could be found, female calves show the difference between HW and SW that was significantly different from zero (P < 0.001); thus, in female calves, the HW is the most limiting factor of the calf's body. The significant variation in some body measures between the calves and the strong correlation within these sizes raises the possibility of selection towards smaller calves aiming to limit the dystocia problem in the BB breed. Furthermore, on the basis of our results, we were able to build equations for the farmer to use at the moment of calving containing the LH, the CF and the calf's gender to estimate SW and HW, the limiting body parts of the calf to be born naturally. Together with the knowledge of the pelvic size of the dam, this information gives the obstetrician or the farmer a more accurate prediction of the probability of natural calving at parturition.     

Calving difficulty and calf survival in beef cows fed two energy levels

Angus and Hereford yearling heifers (469) were bred to either Hereford or Angus bulls and fed either a high level (13.3 Mcal of ME) or a low level of nutrition (7.3 Mcal of ME) for the last 116 days of pregnancy. The level of calving difficulty did not differ between heifers receiving the high (H) and low (L) level of nutrition the first year (36% and 34%) but was significantly higher (P < .01) in heifers receiving H the second year (33% vs. 16%). Calves born to heifers receiving H weighed at birth 2.7 kg more (P < .01) both years than calves born to heifers receiving L. In the first year of the study the size of the pelvic opening was 10 cm larger 1 week before calving (P < .01) in heifers receiving H than in heifers receiving L. Calf survival was not related to level of nutrition, breed of dam or breed of sire either year of the study.     

Abnormal offspring following in vitro production of bovine preimplantation embryos: a field study

Data on 944 calves from 2228 in vitro-produced (IVP) bovine preimplantation embryos were compared with data on 2787 AI calves born in the same herds in 1995. Bovine preimplantation embryos were produced in vitro following ovum pick up (OPU) from donor cows and pregnant heifers in an open nucleus breeding program. After 7 d of in vitro culture on a BRL cell monolayer in the presence of 10% FCS, frozen-thawed expanded blastocysts and fresh morulae to expanded blastocysts were transferred into recipient heifers and cows at 119 contracted farms throughout the Netherlands. The pregnancy rate, as confirmed by palpation per rectum between 90 and 150 d after transfer was 43.5% for both fresh and frozen embryos. Data on IVP and AI calves were registered by the farmers. The percentage of calves with a congenital malformation and the percentage of male calves were related to the total number of calves born. Gestation length, birth weight (measured by a balance), perinatal mortality and ease of calving were analyzed in a subdataset (699 IVP and 2543 AI calves, respectively) by a comparative analysis of variance (ANOVA). The ANOVA model included herd, month of calving, sire nested within AI or IVP, parity and breed of the inseminated cow/embryo recipient, sex of calf, type of calf (AI or IVP) and two-way interactions between type of calf and sex, parity and breed. The percentage of calves with congenital malformations was 3.2% and 0.7% for IVP and AI calves, respectively. An increased incidence of hydro-allantois and abnormal spinal cords and limbs was observed in IVP calves. The percentage of male calves was significantly different between IVP and AI, 55.5% and 48.9%, respectively (Chi-square, 1 degree of freedom, P < 0.05). On the average, IVP calves showed a significant increase of birth weight by 10% (4-5 kg), a 3-d longer gestation period, 2.4% more perinatal mortality and a more difficult calving process compared to AI calves (P < 0.05). From these results it is concluded that calves produced by IVP deviate significantly from calves produced by AI.     

Testicular size at weaning in tropically-adapted beef bulls as influenced by breed of sire and dam

This study was conducted to evaluate testicular size at weaning for bulls representing diverse tropically-adapted genotypes. Calves from 2 locations were weighed and castrated at weaning. In one herd, calves were born to Brahman dams and Angus, Tuli, and Brahman sires. Body weights and paired testes weights were heavier (P < 0.01) for Angus x Brahman (AB) genotype than for Tuli x Brahman (TB) and purebred Brahman (BB) genotype calves. The testes:body weight ratio was greater (P < 0.01) for AB than for TB and BB calves. In a second herd, calves were born to Angus cows and Brahman, Tuli, and Senepol sires. Means were similar between Brahman- (BA), Tuli-(TA), and Senepol-sired (SA) calves for body weight and testes:body weight ratio. Paired testes weight was heavier (P < 0.05) for SA than BA calves. Across locations, paired testes weights were heavier (P < 0.01) for TA than TB calves but their body weights were similar. Within-herd deviations were greater (P < 0.01) for AB than BA calves for paired testes weight and testes:body weight ratio. The correlation between the proportion of Bos indicus genetic contribution and testes:body weight ratio was significantly negative. Tropically-adapted calves differed in testicular size at weaning due to breed of sire and dam effects.     

Mode of delivery is associated with different hematological profiles in the newborn calf

Several studies on babies have shown that the type of delivery can influence the hematological and immune status of the newborn. In bovine medicine, some authors reported the hematological pattern of the newborn calf, but never related it with the calving process or other perinatal factors. The purpose of the present study was to evaluate the hematological profile in newborn calves in relation to the type of delivery. A total of 41 healthy calves were enrolled; 16 Friesian calves which were born by vaginal delivery without assistance (VD), and 25 Belgian Blue calves that were born by elective Caesarean section (CS). As soon as the calves were born, a complete clinical examination was performed to verify viability and maturity. At 10 min after birth, 2 mL venous blood was collected to perform the blood gas and acid-base evaluation. Blood samples were subsequently collected from the jugular vein within 30 min after birth, and at 1, 2, 3, 7, and 14 days of age. An automatic analyzer was used to determine hemoglobin concentration (Hb), hematocrit (Ht), and red and white blood cell counts, while differential leukocyte count was performed microscopically. Statistical analysis was applied to assess differences between the groups and within the group for all parameters between each sampling time (P ≤ 0.05). All the calves were born alive, viable, and mature. There were no acidotic calves, but statistical analysis revealed many differences, as higher pH, base excess (BE) (P ≤ 0.05), PO₂ (P < 0.001), and sO₂ (P < 0.0001) in the VD group. Levels of hemoglobin concentration, hematocrit, and red blood cell number were constantly higher in CS calves (P < 0.001). In comparison with the VD calves, white blood cell and neutrophil absolute number were higher at birth and at 14 days of age in the CS group (P < 0.001 and P ≤ 0.05). The mode of delivery, therefore, seems to have an influence on the oxygenation levels and on the hematological and nonspecific immunity profile of the newborn calf.     

Predicting dystocia in heifers

The relationship of heifer size, calf size and sire on dystocia was studied in approximately one thousand Angus, Hereford X Angus and Charolais heifers bred to Angus, Hereford and Charolais bulls. Heifers were weighed and pelvic measurements taken 35 days post breeding, at midgestation, and on a random group of 135 heifers two weeks prior to calving. Dystocia score, calf birth weight, calf body length, calf hip width and calf sex were recorded at calving.Correlation coefficients for calf traits indicate that birth weight and birth weight to body measurement ratios were the most highly correlated variables with dystocia score. For traits of the dam, pelvic area was the most highly correlated variable to dystocia score, while dam weight had a low and nonsignificant correlation.Sires experiencing a higher than average incidence of dystocia had calves that were larger for all measures of body size. Individual sire differences for dystocia indicate a large number of calves and an accurate randomization of heifers bred to each bull is necessary to make precise judgements as to a bull's potential for siring easy-calving offspring.Calf size measurements were positively correlated with heifer weight and pelvic area; however, correlations tended to be low. Breed of calf, sire, heifer weight I and II and pelvic area I, II and III accounted for only 23.6% of the variation in calf birth weight.Charolais calves were larger (P<.05) and had more dystocia (P<.05) than Hereford or Angus sired calves. Hereford sired crossbred calves were larger (P<.05) and had more dystocia than Angus crossbred or straightbred calves. Angus crossbred calves were larger (P<.05) but had no more dystocia than Angus straightbred calves.Heritability estimates for calf body length (0.35) and calf hip width (0.42) indicate calf skeletal measurements were more heritable than calf birth weight (0.28).Pelvic area measurements were correlated (P<.01) with heifer weight; however, heifer weight I and II accounted for only 37% and 30% of the variability in pelvic area I and II, respectively. Average pelvic area was largest in Charolais heifers, followed by Crossbred and Angus heifers. Pelvic area growth was .275 cm²/day in Angus, .254 cm²/day in Crossbred, and .250 cm²/day in Charolais heifers.Dystocia score was most highly related to calf size and pelvic area I. Pooled over all breeds, a regression analysis showed 37% of the variability in dystocia score being accounted for by the ratio of calf birth weight to calf body length and pelvic erea I. Very little increase in the R² value occurred by the addition of the other independent variables.Histogram analyses demonstrates that a constant level of dystocia can be maintained only if pelvic area increases in proportion to calf size. However, regardless of the size of calf, heifers that had very small pelvic openings had a high rate of dystocia, just as heifers having very large calves experienced high rates of dystocia even when they had large pelves.     

Effects of body condition and temporary calf removal on reproductive performance of range cows

The effects of body condition at calving and breeding and temporary calf removal prior to the start of the breeding season on reproductive performance of 323 cows from two breed groups were studied over two breeding seasons. Body condition score at calving was significantly and positively correlated with two body condition indices, which were based on weight-to-height ratio measured at calving and at the start of the breeding season. While the two body condition indices were strongly associated with the age of the cow, the body condition score, based on palpation and visual appraisal, was less affected by the age of the cow. Cows with a body condition score of 3.0 at calving had a shorter calving interval (P<0.02), higher pregnancy rate (P<0.08), and higher number of calves born (P<0.10) than cows which had body condition scores lower than 3.0 at calving. Temporary (48 h) calf removal prior to the start of the breeding season did not have a significant influence on the calving interval, pregnancy rate or the number of calves born nor on the weaning weights of their calves. Differences in reproductive performance between the two breed groups of cows were not significant.     

Effect of dam factors on milk intake and performance of Belgian Blue suckling calves

Milk intake data were collected at 4-week intervals from Belgian Blue double-muscled (BBDM) suckling calves up to 16 weeks after birth. Dams were fed at 100%, 90%, 80% or 70% of their energy requirements during a 140-day indoor period from the beginning of December to the end of April (restriction period). Afterwards, cows were turned out on pasture (re-alimentation period). Mean calving date was 3 June, but parturitions were spread over the year. A total of 521 individual milk intake (IMI) and 120 average daily milk intake (AMI, mean of IMI) records were collected. IMI amounted to 7.0 ± 2.2 kg/day and was not affected by energy level during the indoor period. It was highest in May and June. Calves born out of multiparous cows consumed more milk than those born out of primiparous cows (7.4 v. 6.2 kg per day; P = 0.001), while intake tended to be higher in female than in male calves (7.2 v. 6.8 kg per day; P = 0.044). Dam age at calving, parity, post partum weight and body condition were only weakly correlated with AMI (r 0.4). AMI was correlated with pre-weaning live-weight gain (r = 0.807) and weaning weight (r = 0.783), with a slightly higher correlation for male than for female calves. Daily live-weight gain during the suckling period was increased by 79 g per extra kg daily milk intake on average, and by 86 and 74 g, respectively, for male and female calves. Calf solid feed intake was low, even when milk intake was low. In terms of net energy intake, milk was only substituted for solid feed by 29%. It can be concluded from the calf intake that milk production in BBDM cows is comparable with that of cows from other beef breeds, but its variation is considerable, complicating an accurate estimation.     

A study of association between genetic markers in candidate genes and reproductive traits in one generation of a commercial broiler breeder hen population

Markers of alleles for three physiological candidate genes for reproductive traits, growth hormone (GHR), gonadotropin-releasing hormone receptor (GNRHR) and neuropeptide Y (NPY) were assessed for the association with the total egg production, number of double-yolked eggs and age at first egg in a single generation of a broiler breeder (Gallus gallus) pedigree dam line. Single-nucleotide polymorphisms and deletions were detected in the GHR, GNRHR and NPY genes. Genotypes were identified using a PCR-RFLP assay. The frequency of restriction enzyme+/-alleles in the population was for GHR 0.68 (NspI-) and 0.32 (NspI+), for NPY 0.78 (DraI+) and 0.22 (DraI-) and for GNRHR 0.54 (Bpu1102I+) and 0.46 (Bpu1102I-). Trait data from a total of 772 hens in 67 sire families from one generation of the pedigree dam line were recorded. However, the analysis used only the offspring of heterozygous sires to reduce the influence of selection and genetic background (n=33 sire families for GHR; n=14 sire families for NPY; n=36 sire families for GNRHR). A dominance effect of NPY on age at first egg and an additive effect of GNRHR on the number of double-yolked eggs were found (P<0.05).     

Genetic gains from reciprocal recurrent and within-line selection for egg production in the fowl

Summary Selection for survivors percent egg production from first egg to 40 weeks of age was conducted for six generations. Within-line selection (WLS) on the basis of an index of individual records plus sire family and dam family means was compared with reciprocal recurrent selection (RRS) based on sire family selection among cross progeny. Genetically heterogeneous synthetic populations, the Cornell Control and the Purdue Pool strains were used.The responses to WLS (3.84 °) and RRS (2.57 °) were both significantly greater than zero, but were not significantly different from each other. Nevertheless, the responses were proportional to their predicted values (.363 vs. 340). The advantage of WLS was due to the mechanics of selection resulting in slightly greater selection intensity and an increased correlation between the criterion of selection and the trait being improved. On the contrary, the RRS method had a slightly larger realized heritability as would be expected in the presence of non-additive genetic variance. Four of five pure-lines selected under both methods had statistically significant declines in performance due to inbreeding depression effects. All of the results observed are comparable with known genetic theory.Some problems in comparing genetic gains from different selection methods or selection criteria are discussed.Journal Paper No. 4986 of the Purdue University Agricultural Experiment Station. Conducted in cooperation with the Regional Poultry Breeding Laboratory, Project N. C. 89. Supported in part by N. I. H. Grant No. ES00310.     

Animal performance and stress at weaning when dairy cows suckle their calves for short versus long daily durations

Calves in most dairy farms are separated from their dams either immediately or within a few hours after birth, prompting increasing concern of the society for reasons of animal welfare. The aim of this study was to identify systems to maintain cow-calf contact (CCC) that balance the benefits for calf growth and health against the negative impacts on sellable milk and stress at weaning. We tested reuniting cows and calves for 20 min before (Before-group) or 2.5 h after (After-group) morning milking (in Trial 1) or for a 9 h period between the morning and evening milkings (Half-day-group, in Trial 2). In Control-groups, calves were separated from their dam at birth and fed with artificial nipple with tank milk provided daily at 13% (Trial 1) and 14% (Trial 2) of their BW. In both trials, each practice was applied on a group of 14 dam–calf pairs (7 Holstein [Ho] and 7 Montbéliarde [Mo]). All calves were weaned at a BW of at least 100 kg. In Trial 1, the After-group was prematurely stopped when the calves were eight weeks of age as calf growth became limited (340 g/d) due to low milk intakes (2.97 kg/d). During the first eight weeks of lactation, milk yield at the parlour was 29%, 51% and 42% lower in After-, Before- and Half-day-cows respectively compared to Controls. From week 14 to 16 when all calves were separated from their dam, Before-cows still produced 25% less milk than Control-cows while Half-day-cows reached the milk yield of Control-cows within a week. There were no significant differences in milk somatic cell count and in frequency of health disorders (cows and calves) between suckling and Control-groups. Compared to Control-calves, calf growth until weaning was higher in the suckling calves in Trial 1 (861 vs 699 g/d) and similar in Trial 2 (943 vs 929 g/d). At weaning, Before- and Half-day-calves started to vocalise earlier and continued to vocalise longer than Controls. In conclusion, the best compromise between cow milk yield and calf growth is a long period of CCC (9 h) between the morning and evening milkings. Still abrupt weaning stresses both cows and calves even if CCC has been restricted before separation.     

Infant development in two aquarium bottlenose dolphins

The behavioral development of two aquarium bottlenose dolphin calves, one male (born to a primiparous mother) and one female (born to a multiparous mother), was examined. From birth to 9 weeks of age, a total of 558.7 h of nursing and behavioral data were collected using focal sampling methods. Data from both calves revealed a pattern of increasing independence as they aged, but there were significant differences between the two calves. Suckling rates, mean suckles per bout, suckling bout rates, and bout durations for the male calf were higher than those for the female calf throughout the study. These frequencies declined significantly over time in the male's case but not in the female's case. Her suckling durations (lock-on time) were longer than his. The male spent more time in infant position (under the mother) than the female calf and less time swimming in echelon position (alongside the mother). Over time, the male spent less time in infant position, and the female calf spent more time socializing and less time echelon swimming. Both calves decreased the amount of time spent close to their mothers over the 9 week period, and the mothers decreased their role in proximity maintenance over time. We suggest that factors related to maternal primiparity caused the male calf to develop an effective compensatory response of frequent nursing and spending more time in infant position. Both calves survived and were healthy at the end of the observation period. © 1995 Wiley-Liss, Inc.     

The periparturient rise in fecal egg counts in three strains of Florida native ewes and its value in predicting resistance of lambs to Haemonchus contortus

The periparturient rise in fecal egg counts in three strains of Florida Native ewes and its value in predicting resistance of lambs to Haemonchus contortus. International Journal for Parasitology16: 185–189. Significant (P < 0.05) differences in the magnitude of the periparturient rise in fecal egg counts (PPR) occurred in ewes of three strains of Florida Native sheep. Non-lambing ewes (n = 12) and lactating University strain ewes (n = 31), a strain selected over a 26-year period for parasite resistance by survival at pasture without anthelmintic treatment, had lower fecal egg counts than ewes of either Maxcy strain (n= 17), a commercial strain treated regularly with anthelmintics, or Backlinie strain (n = 16), a strain of Florida Native sheep that had some crossbreeding to Hampshire and Suffolk in their genotype and were regularly treated with anthelmintics. Whereas both Maxcy and Backlinie ewes showed a pronounced PPR, none occurred in non-lambing ewes (n=12) and the slight rise in fecal egg counts observed in University ewes was not significantly different from that of the non-lambing ewes. Backlinie ewes having twin lambs (n = 5) had a higher PPR than Backlinie ewes with single lambs (n = 11) or Maxcy ewes with single lambs (n = 15), but all three groups had higher PPRs than University ewes with single lambs (n = 27). No differences occurred in fecal egg counts of non-lambing ewes regardless of strain. Six weeks after weaning fecal egg counts of all ewes were uniformly low regardless of strain or prior lactation status.Ram lambs born to these ewes showed no significant strain differences in Haemonchus contortus burdens after experimental infection, deworming with levamisole and reinfection, although University lambs (n= 13) had lowest mean worm burdens at necropsy (2437) followed by Maxcy lambs (n= 12, mean =3106) and Backlinie lambs (n= 13, mean =3670). There was no significant correlation between worm burdens in these lambs and the magnitude of the PPR in their dams. Eight to 16 weeks after turn out to a common parasite-infested pasture ewe lambs (n = 13) born to University ewes had lower fecal egg counts than similar ewe lambs (n=8) born to Backlinie ewes. Prior to this time differences were not significant and egg counts were generally low. The magnitude of the PPR in their dams was not significantly correlated with fecal egg counts or PCVs of individual ewe lambs.     

Prevalence and Associated Risk Factors of Toxocara vitulorum Infections in Buffalo and Cattle Calves in Three Provinces of Central Cambodia

The prevalence and associated risk factors of Toxocara vitulorum infection in buffalo and cattle calves was studied in 3 provinces in central Cambodia. Fecal samples were collected from 517 calves between the age of 1-15 weeks and processed for nematode egg counts by a modified McMaster method. A total of 64 calves were found to excrete T. vitulorum eggs in their feces (12.4%; 95% exact CI: 9.7-15.5). The mean fecal egg count was 2,798 EPG (SD=16,351; range=0-224,400). A multivariable generalized linear mixed model showed higher odds of T. vitulorum infection for buffalo versus cattle, for animals aged 4-8 weeks versus younger and older ones, and for animals with strongyle infection. There was no association with fecal consistency. Farmers should be aware of the potential impact of T. vitulorum, and treat their calves at the age of 2-3 weeks with anthelmintics such as benzimidazoles or pyrantel.