Graphical approach to evaluate genetic estimates of calf survival.

Genetic variation and resemblance among relatives are fundamentals of quantitative genetics. Our purpose was to identify bulls with a bimodal pattern of inheritance in the quest for new discoveries about the inheritance of calf survival. A bimodal pattern of inheritance for calf survival was identified in sons of Holstein bulls. A bimodal pattern of inheritance indicates 2 groups of sons resulting from an allele effect, a grandsire effect, or some other common factor. Different combinations (AA, Aa, aa) of 2 alleles at a locus cause varying phenotypes to be expressed. Bulls that are heterozygous for loci affecting reproductive performance may have a bimodal pattern of inheritance if the difference in effect of the 2 alleles is large. If the bimodal pattern is caused by an allele effect, then molecular markers can be identified for use in marker-assisted selection breeding programs. Data on predicted transmitting ability for perinatal survival for the first parity of 8,678 sons of 599 sires were collected from 1984 through 1997 from the National Association of Animal Breeders calving ease database, which included 7 Midwestern states. Sixteen bulls were identified with a potential bimodal pattern of inheritance because they had 2 distinct groups of sons. The 2 groups of sons were separated by calculating the coefficient of variation for each possible combination of sons; the combination that gave the smallest coefficient of variation difference between the 2 groups was considered the correct distribution of the sons into those groups. Bulls with a bimodal distribution were analyzed to determine the distribution of the grandsons among the maternal grandsires (MGS) of the 2 groups of the bimodal distribution. The bimodal distribution may be a result of heterozygous sires or MGS that are homozygous for low or high survival. If the bimodal distribution is caused by a MGS effect, then marker-assisted selection can still be used by evaluating the MGS instead of the sires.

Porcine sperm zona binding ability as an indicator of fertility.

The escalated use of artificial insemination in swine has increased the importance of determining fertility of a semen sample before it is used. Multiple laboratory assays have been developed to assess fertilizing potential but they have yielded inconsistent results. This experiment sought to determine the relationship between in vitro competitive zona binding ability and in vivo fertility based on heterospermic inseminations and paternity testing. The zona pellucida binding ability and fertility of sperm from 15 boars was assessed by comparing sperm from one boar with sperm from other individual boars in a pairwise fashion using four ejaculates. The relationship of zona binding ability to the mean number of piglets sired per litter for each boar as well as historic fertility data (litter size and farrowing rate) was assessed. The in vitro competition assay consisted of labeling sperm from each boar of the pair with a different fluorophore and incubating an equal number of sperm from each boar in the same droplet with porcine oocytes. The competitive assay was highly effective in ranking boars by zona binding ability (R2=0.94). Paternity testing using microsatellite markers was used to determine the mean number of piglets sired per litter for each boar during heterospermic inseminations. The pairwise heterospermic insemination assay was effective in ranking boar fertility (R2=0.59). Using historical data from these boars, average litter size and farrowing rate were correlated (r=0.81, p<0.001). However, zona binding ability was not significantly correlated with historic farrowing rate data or historic average litter size. Boar sperm zona binding ability was also not correlated significantly with the mean number of piglets sired per litter following heterospermic insemination. But the number of piglets sired by each boar was related to a combination of zona binding ability, sperm motility, normal morphology, acrosomal integrity, and the presence of distal droplets (R2=0.70). These results suggest that zona binding ability is not an accurate predictor of fertilizing ability when used alone; however, when coupled with other sperm assessments, fertility may be predicted successfully.

Effects of suckling intensity on milk yield and piglet growth from lactation-enhanced gilts.

The effects of suckling intensity on milk yield and piglet growth were determined when lactation capacity of the sow was enhanced through overexpression of a mammary-specific transgene, bovine alpha-lactalbumin. Lactational response to increased suckling stimulation was determined by fostering litters of the same age (d 1) or 7 d older (d 7) than the day of lactation to sows nontransgenic (control) or transgenic (TG) for bovine alpha-lactalbumin. Twenty first-parity gilts were allocated to 4 treatments dependent on gilt genotype and age of litter fostered (control d 1, control d 7, TG d 1, and TG d 7). Litters were standardized to 10 piglets within 24 h postpartum, and nonbirth piglets were fostered to gilts with an equal litter BW within age groups at 36 h postpartum. Milk yield was determined by the weigh-suckle-weigh method on d 6, 9, 12, 15, and 18 of lactation. Mean daily milk yield was greater (P = 0.031) for TG gilts compared with control gilts and tended to be greater (P = 0.056) for all gilts with d-7 piglets compared with those with d-1 piglets. Daily milk yield of TG d 7 gilts increased rapidly to peak at d 9 and was greater than milk yield of all control gilts at d 9 (P < 0.01), 12 (P < 0.02), and 15 (P < 0.02). Mean daily milk yield of TG d 7 gilts was 2.1 kg greater (P = 0.002) than for control d 7 gilts and 2.0 kg greater (P = 0.004) than for TG d 1 gilts. Daily milk yield of control d 1 gilts was not different from that of TG d 1 gilts (P = 0.49) or control d 7 gilts (P = 0.63). Piglet BW gain between d 3 and 6 was greater (P < 0.01) in the TG d 7 group than for all other groups and was greater (P < 0.05) than the control groups between d 6 and 9. No difference was found when comparing accumulated BW gain of the piglets between the day of age at foster (d 1 vs. 7; P = 0.606) or between the control d 1 and control d 7 groups (P = 0.759). Accumulated BW gain of piglets suckling TG d 7 gilts from d 3 through 9 was greater (P < 0.02) than that of the other groups and continued to be greater (P < 0.05) than that of either of the control groups through d 15. However, by d 15, accumulated BW gain of piglets suckling TG d 1 gilts was no longer different (P = 0.40) from that of the TG d 7 group and was greater (P < 0.05) than that of the control d 1 group. The enhanced lactation potential of these TG gilts synergized with suckling intensity to stimulate increased milk production during early lactation, resulting in increased piglet growth.

Milk loss and treatment costs associated with two treatment protocols for clinical mastitis in dairy cows.

The objective of this study was to compare milk loss and treatment costs for cows with clinical mastitis that were given antibiotics in addition to supportive treatment or supportive treatment alone. Between January 1994 and January 1996, 116,876 daily milk records on 676 lactations were taken at the University of Illinois Dairy Research Farm. Clinical mastitis was diagnosed during 124 lactations with 25,047 daily milk records, and 1417 of the daily milk records were on days when clinical mastitis was present. Cows with clinical mastitis were randomly assigned to one of 2 treatment groups: N (supportive treatment only) or A (antibiotics in addition to supportive treatment). Extent of antibiotic and supportive treatment varied according to twice daily severity scores. Projected and actual daily milk yields were estimated utilizing a random regression test-day model, and the differences were summed over 305 d of lactation to estimate lactational milk yield loss. The actual amount of discarded milk was added to milk yield loss to determine total milk loss per lactation. A cost analysis that included milk loss and treatment costs was then performed. Cows with clinical mastitis that were given only supportive treatment lost 230 +/- 172 kg (mean +/- standard error of mean [SEM]) more milk and incurred 94 +/- 51 dollars (SEM) more cost per lactation than cows given antibiotics and supportive treatment. Cows given only supportive treatment showed a response pattern of 305-d milk yield loss and economic loss per lactation that varied 2 to 3 times as much as cows treated with antibiotics. Based on reduced milk loss, better reliability (less variable response), and lower economic loss, the addition of antibiotics to supportive treatment was more efficacious and cost effective than supportive treatment alone.

Hot topic: effects of frequent milking in early lactation on milk yield and udder health.

A field study was conducted to evaluate the influence of milking frequency (3 or 6 times/d [3x or 6x, respectively]) during the initial 21 d of lactation on milk and milk component yield and mammary gland health as indicated by somatic cell count. During 2 seasons, spring and fall, multiparous cows were milked 6 times/d until d 21 of lactation and then returned to the 3 times/d frequency for the remainder of lactation (6x; n = 9). Multiparous cows milked 3 times/d from the beginning of lactation served as a control group (3x; n = 17). With the exception of milking frequency, all other aspects of management, including housing, milk harvesting, and feeding, were identical between the groups and were consistent with industry norms. Retrospective analysis of Dairy Herd Improvement Association records was used to evaluate milk yield, milk component yield, and somatic cell scores. As expected, 6x cows produced more milk on the first test day than 3x cows. Compared with 3x cows, higher milk yields persisted for 6x cows from test day 2 through 6, indicating a persistent effect of early lactation milking frequency on milk yield potential for that lactation. Milk component yield followed a similar pattern: 6x cows produced significantly more protein, fat, and total solids than did control cows throughout the study. With regard to udder health, 6x cows had lower somatic cell counts at the first test day relative to 3x cows and had reduced somatic cell scores for the first 3 mo of lactation, which suggests that early lactation milking frequency influences the mammary gland capacity to resist infection in addition to improving milk production efficiency.

The relationship of porcine sperm zona-binding ability to fertility.

Several laboratory assays have been designed to assess the fertility potential of a semen sample before insemination, but none have been consistent and accurate predictors of fertility. To determine whether zona-binding ability may be a useful fertility predictor, we validated and used an in vitro competitive assay to measure the ability of porcine sperm to bind to the zona pellucida. The zona-binding ability of sperm from 11 boars that exhibited a broad range in average litter size and farrowing rate was determined. Sperm from each boar were compared directly with sperm from eight other boars in a systematic, pairwise fashion. Sperm from two semen samples were labeled with fluorophores at concentrations that did not affect motility or zona-binding ability. An equal number of labeled sperm from each boar was coincubated with homologous oocytes. Least squares means from analysis of variance were used to rank boars based on zona-binding ability. The competitive assay was effective in establishing a ranking of the boars (R2 = 0.62). Furthermore, there was a correlation between zona-binding ability and fertility when estimated by average litter size (r = 0.64, P < 0.05) but not when estimated by farrowing rate (r = -0.28). The explanation for this difference was that litter size and farrowing rate were poorly correlated (r = 0.14). In conclusion, a competitive zona-binding assay distinguished boars that sired either small or large litters. Competitive zona-binding ability may be useful for identifying boars with reduced fertility that produce smaller litters following insemination.

Investigation of breeding strategies to increase the probability that German shepherd dog and Labrador retriever dog guides would attain optimum size.

An optimum-sized dog guide weighs 18 to 32 kg and measures 53 to 64 cm in height at the withers when mature body size is attained. Effects of selection index with and without restrictions, independent trait selection, directional selection, stabilizing selection, and negative assortative mating were modeled using data from German shepherd dogs and Labrador retrievers raised by the Seeing Eye, Inc., Morristown, NJ from 1979 to 1997. The selection goals were to decrease mature weight and mature height in German shepherd dogs and to decrease mature weight and increase mature height in Labrador retrievers. Mature weights were recorded for 1,333 German shepherd dog offspring and their 69 dams and 17 sires, and 1,081 Labrador retriever offspring and their 51 dams and 13 sires. Mature heights also were recorded for offspring and parents, including 871 German shepherd dogs from 70 dams and 15 sires, and 793 Labrador retrievers from 40 dams and 13 sires. Selecting on mature weight alone produced the highest aggregate genetic-economic gain for German shepherd dogs compared with the selection indices with and without restrictions, generating a 2.10-kg decrease in mature weight and a correlated 0.36-cm decrease in mature height. In Labrador retrievers, selecting for mature height alone produced the highest aggregate genetic-economic gain but caused an increase in mature weight. Weighting the two traits equally but in the opposite direction without restrictions was the only index that produced the desired effect of decreasing mature weight and increasing mature height in Labrador retrievers. Response to selection for one generation of directional selection for a single trait included a 0.50-kg decrease in mature weight for German shepherd dogs, a 0.59-kg decrease in mature weight for Labrador retrievers, a 0.18-cm decrease in mature height for German shepherd dogs, and a 0.91-cm increase in mature height for Labrador retrievers. Increasing the percentage of dogs attaining optimum size may decrease the cost of production for the Seeing Eye, Inc., because fewer dogs would need to be raised and trained to provide assistance to the same number of blind individuals.

Repeatability of objective measurements on the rear legs of dairy cows.

The objective of this paper was to estimate the repeatability of objective measurements on the rear legs of dairy cows to see whether higher repeatability estimates could be obtained compared to the corresponding subjective linear score. Between September and November 1998, seven measurements of distance among dewclaw, hip, hock, pinbone, and thurl were taken on 73 cows from the University of Illinois dairy farm. Measurements were combined to define triangles and therefore angles reflecting rear leg structure. Three novice evaluators participated in the experiment, and, on a given day, two sets of measurements were taken by two evaluators. Cows were measured twice at a 1- to 4-wk interval. Size, evaluator, and order of measurement were included in the model as fixed effects. Cow, interactions of cow x evaluator and cow x order of measurement were random effects included in the model. The model explained over 80% of the variation for each variable. Repeatability estimates of the length measurements ranged from 0.61 to 0.89. Repeatability estimates of angles were much lower ranging from 0.00 to 0.24. The variation in natural standing position of the cow hampered the accuracy of the objective measurements. Low estimates of repeatability for angles describing rear leg suggested that objective measurements by novice evaluators were not sufficiently reliable to potentially replace the subjective linear score for rear leg curvature determined by experts. Usefulness of further investigation to find objective measurements that would give a better description of rear legs conformation compared to the corresponding current type trait was questionable.

Effects of double stocking and weighing frequency on pig performance in wean-to-finish production systems.

Two studies were carried out in different wean-to-finish barns to determine the effects of double stocking on pig growth performance. In Study 1, pigs (n = 1,560) were used in a randomized complete block design with a 2 x 2 factorial arrangement of treatments: initial stocking treatment (Single [52 pigs/pen] vs Double [104 pigs/pen] stocked for 10 wk after weaning) and weighing frequency (High [12 times during the study] vs Low [3 times]) on pig performance from weaning (5.9+/-0.01 kg BW; 17 d of age) to harvest (114+/-0.67 kg BW). Floor and feeder space per pig were 0.650 m2 and 4 cm and 0.325 m2 and 2 cm for the single- and double-stocked treatments, respectively. In Study 2, pigs (n = 1,458) were used in a randomized complete block design to evaluate two initial stocking treatments (Single [27 pigs] vs Double [54 pigs] stocked for 10 wk after weaning) on pig performance from weaning (4.8+/-0.01 kg BW; 15 d of age) to harvest (24 wk after weaning). Floor and feeder space per pig were 0.640 m2 and 3.4 cm and 0.320 m2 and 1.7 cm for single- and double-stocked pens, respectively. In both studies, double-stocked pigs were split at the end of wk 10 into two equal-sized groups of similar mean BW and CV of BW, and one group was moved to a different pen in the same building. In Study 1, performance was not affected (P > 0.10) by frequency of weighing. For the first 10 wk after weaning, the Double compared to the Single treatment had lower ADG (7.7 and 7.9%, for Studies 1 and 2, respectively; P < 0.001) and lighter pigs at wk 10 (6.8 and 7.3%, respectively; P < 0.001). During the first 10 wk in Study 1, Double compared to the Single pigs had lower ADFI (7%; P < 0.001) but similar gain:feed (P > 0.10). From wk 11 to harvest, pigs on Double and Single treatments had similar (P > 0.10) ADG in both studies and, in Study 1, ADFI was unaffected by initial stocking treatment, but double-stocked pigs had greater gain:feed (4%, P < 0.01). Double-stocked pigs required an additional 2 d to reach a fixed harvest BW (P < 0.05) in Study 1 and were lighter (4%; P < 0.05) at 24 wk after weaning in Study 2. Carcass measures were similar (P > 0.10) for double- and single-stocked pigs. Double-stocked pigs that were moved at the end of 10 wk had growth performance similar (P > 0.10) to those that remained in the original pen. In summary, double stocking reduced growth rate to 10 wk after weaning but subsequently had no effect on growth rate and improved feed efficiency.

Estimated genetic parameters for growth traits of German shepherd dog and Labrador retriever dog guides.

A desirable dog guide weighs 18 to 32 kg and measures 53 to 64 cm in height at the withers as an adult. Heritabilities and genetic correlations were estimated for birth weight, 42-d weight, mature weight, and mature height for 2,334 German shepherd dogs and 2,028 Labrador retrievers raised by the Seeing Eye, Inc., Morristown, NJ, from 1979 to 1997. Data included 5,006 observations for German shepherd dogs from 113 dams and 33 sires and 4,123 observations for Labrador retrievers from 89 dams and 29 sires. A mixed effects model was considered with sex and birth year as fixed effects. Random effects were animal, maternal, and litter incorporating all pedigree information available. A derivative-free REML method was used to estimate parameters. The maternal component was higher than the additive genetic component for birth weight. Heritability of mature weight was estimated as 0.57 +/- 0.07 for German shepherd dogs and 0.44 +/- 0.07 for Labrador retrievers. Mature height heritability was estimated as 0.35 +/- 0.08 for German shepherd dogs and 0.46 +/- 0.08 for Labrador retrievers. Selection for lighter dogs at maturity is predicted to decrease the average mature height, and selection for taller dogs at maturity is predicted to increase the average mature weight. The estimated genetic parameters will aid in the development of strategies to increase the probability of breeding dogs for optimum mature size.

Breed and sex differences in growth curves for two breeds of dog guides.

A desirable dog guide weighs 18 to 32 kg as an adult. Male and female German shepherd dogs and male and female Labrador retrievers were weighed between birth and 18 mo of age, with at least one weight recorded after 290 d of age. Growth curves were constructed from 10,484 observations on 880 dogs using the Gompertz function in the form Wt = W(max)exp(-e[-(t-c)/b]), where Wt is weight at time t, Wmax is mature body weight, b is proportional to duration of growth, c is age at point of inflection, and t is age in days. Estimates for mature body weight were 2.4 +/- .3 kg higher for Labrador retrievers than for German shepherd dogs and 4.7 +/- .2 kg higher for males than for females. Male Labrador retrievers were closest to the upper limit for desirable weight, with an average estimated mature weight of 31.4 +/- .3 kg. Duration of growth, 4b + c, was not different between the breeds; however, the estimate for males was 8 +/- 5d longer than for females. Female Labrador retrievers had the shortest estimate for growth of 319 +/- 6 d. The estimate for age at the point of inflection was 3.6 +/- 1.2 d greater for males than for females, but not different between breeds. A better understanding of growth curves for dog guides may aid in estimating mature weight at a young age, thus allowing earlier breeding and training decisions to be made and increasing genetic change per year.

Comparison of antibiotic administration in conjunction with supportive measures versus supportive measures alone for treatment of dairy cows with clinical mastitis.

OBJECTIVE: To determine whether antibiotic and supportive treatment would improve outcome for dairy cows with naturally developing clinical mastitis, compared with supportive treatment alone. DESIGN: Randomized controlled trial. ANIMALS: 124 cows in one herd with 172 episodes of clinical mastitis. PROCEDURE: Cows were examined at the onset of clinical mastitis, assigned a severity score, and randomly assigned to receive antibiotic (intramammary administration of cephapirin, i.v. administration of oxytetracycline, or both) and supportive treatment (administration of oxytocin, stripping of affected glands, and, in severely affected cows, administration of flunixin meglumine or fluids) or supportive treatment alone. Treatment was continued until 24 hours after signs of clinical mastitis resolved (clinical cure). Milk samples from affected glands were submitted for bacterial culture before initial treatment and every 2 weeks thereafter until the causative organism was no longer isolated (bacteriologic cure). RESULTS: When mastitis was caused by Streptococcus spp or coliform bacteria, clinical cure rate by the tenth milking was significantly higher if antibiotics were used. Bacteriologic cure rate at 14 days was significantly higher when antibiotics were used, particularly if mastitis was caused by Streptococcus spp. Cows receiving antibiotics developed fewer subsequent episodes of clinical mastitis during the 60 days after the initial episode of mastitis and had less severe clinical disease than cows that did not. CLINICAL IMPLICATIONS: Results suggest that, in herds in which mastitis is often caused by environmental bacteria, antibiotic and supportive treatment may result in a better outcome for cows with clinical mastitis than supportive treatment alone.

Dietary variety via sweetening and voluntary feed intake of lactating dairy cows.

The effects of choice of diets on feed intake were studied using 12 lactating Holstein cows. A switchback design was used that had three periods and two sequential blocks. Diets were 1) a control total mixed ration (TMR), which consisted of alfalfa haylage, corn silage, and a concentrate mixture based on ground corn and soybean meal (25:25:50 on a dry matter basis) and 2) a sweetened TMR in which a brown sugar food product constituted 1.5% of the dietary dry matter. Treatments consisted of the control TMR fed on both sides of divided feed bunks, the sweetened TMR fed on both sides of divided feed bunks, or both TMR fed on alternating (daily) sides of divided feed bunks in tie stalls. Periods were 2 wk in duration, and cows averaged 67 and 53 d of lactation at the start of blocks 1 and 2, respectively. The dry matter intake, body weight, milk yield, and percentages of milk fat, protein, and solids not fat were similar when either TMR was fed alone. A choice of control TMR or sweetened TMR did not affect any of these variables. The dry matter intake, body weight, milk yield, and milk protein percentage were affected by block; however, these effects were probably caused by differences between the blocks in environment and stage of lactation. The results of this experiment might have been affected by the composition of the control TMR, its similarity to the sweetened TMR, availability of both diets simultaneously when a choice was offered, and use of a TMR instead of separate feeds or simpler mixtures.

An inherited platelet function defect in a Simmental crossbred herd.

An inherited bleeding disorder, resembling Simmental hereditary thrombopathy (SHT), has been identified in a Simmental crossbred herd. In an affected bull calf, initially evaluated because of excessive bleeding from a vaccination site, the platelet aggregation response to the agonist, adenosine-diphosphate (ADP) was essentially absent and the aggregation response to platelet activating factor (PAF16) was reduced by at least 70%. The initial laboratory assessment of platelet function in the dam and sire yielded results which were within normal limits. The sire was not available for further testing. The dam, also a daughter of this sire, was subsequently shown to have a partially reduced aggregation response to ADP. Of 18 other offspring of the sire evaluated, 6 were also identified as having a partially impaired aggregation response. The maximum aggregation response to ADP and PAF16 in these 6 calves was approximately 50% of the level exhibited by unaffected animals. In contrast, the coagulation profiles were normal for all animals except for a heifer calf which also exhibited a partially impaired aggregation response. The plasma level of the coagulation protein, factor XI, was reduced in this heifer calf which suffered a fatal hemorrhage following dehorning. This report appears to be the 1st to have identified animals putatively heterozygous for SHT on the basis of the in vitro platelet aggregation response to ADP.

Evidence that systemic relaxin promotes moderate water consumption during late pregnancy in rats.

The protein hormone relaxin is secreted by the ovaries throughtout the second half of the 23 day pregnancy in the rat. We recently reported that neutralization of endogenous relaxin with monoclonal antibodies for rat relaxin decreases water consumption during the daily light period during the second half of pregnancy in rats. The apparent effects of relaxin on water consumption, however, were extremely modest. One explanation for the failure to observe a greater relaxin-dependent effect on water consumption is failure of the monoclonal antibody for rat relaxin to neutralize all circulating relaxin. A second explanation is that circulating relaxin has only slight effects on water consumption. This investigation was conducted with an experimental model in which circulating relaxin was removed in order to re-examine the effects of relaxin on water consumption during the daily light period in late pregnancy in rats. On day 9 (D9) of pregnancy, before the presence of relaxin (R) in the circulation, primiparious pregnant rats were ovariectomized (O) or sham ovariectomized (C). Throughout the remainder of pregnancy, rats were treated with combinations of either progesterone (P) and estrogen (E, group OPE) or progesterone, estrogen and porcine relaxin (group OPER) in doses that restore physiological parameters to values similar to those that occur during the second half of pregnancy in intact rats. Progesterone and estrogen were administered by Silastic tubing implants and porcine relaxin was administered via miniature osmotic pump. Sham-ovariectomized animals received either the hormone vehicles (group SC) or no implants (group IC). Water consumption was measured daily from D4 to D20 at both 0700 and 2100 h which was when the lights went on and off respectively. Water consumption increased as pregnancy continued from D10 to D20 during the daily 10 h dark periods (P < 0.01), but not during the 14 h light periods for all four groups. Daily water consumed by rats in group OPE was significantly lower (P < 0.05) than that consumed by shamovariectomized rats from D17 to D20 and lower than that consumed by rats in group OPER on D20. During the dark period there was no difference in water consumption among groups. During the light period, however, group OPE consumed significantly less water (P < 0.05) than group C from D18 to D22. Moreover, there was a consistent tendency (P < 0.13) for the water consumption to be greater in rats in group OPER than in those in the relaxin-deficient group OPE during the daily light period from D11 to D20 of pregnancy. We conclude that the increase in water consumption that occurs during the daily dark periods during the second half of pregnancy is not attributable to circulating relaxin. Circulating relaxin promotes only modest increases in water consumption during the daily light periods during late pregnancy in the rat.

Evaluation of breed as a risk factor for atresia coli in cattle.

Systematic review of published cases and a hospital-based case-control study were completed to evaluate breed as a risk factor for atresia coli in cattle. Systematic review of 37 published studies indicated that atresia coli has been diagnosed in 10 cattle breeds and 12 countries, with the marked preponderance of cases occurring in Holstein-Friesian calves (485/514 cases, 94%). Epidemiologic analysis based on 28,373 cattle < 2 mo of age admitted to North American veterinary schools between 1964 and 1993 identified 291 cases of atresia coli in 13 breeds, with the marked preponderance of cases occurring in Holstein-Friesian calves (228/291, 78%). Holstein-Friesian cattle were at significantly greater risk for the condition than all other dairy cattle breeds (crude odds ratio 4.55, P < 0.0001) and all other cattle breeds (crude odds ratio 7.12, P < 0.0001), whereas there was no difference in the odds ratio between dairy cattle (not Holstein-Friesian) and beef cattle (crude odds ratio 1.68, P = 0.11). Atresia coli probably occurs secondary to vascular insufficiency of the developing colon. Holstein-Friesian cattle may be genetically predisposed to atresia coli, possibly because their developing colon grows at a faster rate and/or to a greater extent than that in other cattle breeds. Early or vigorous palpation per rectum of the amniotic vesicle appears to increase the risk of atresia coli in a genetically predisposed fetus, probably through palpation-induced damage to the developing colonic vasculature.

Evaluation of udder health and mastitis in llamas.

OBJECTIVE: To investigate intramammary infections in llamas, identify the pathogens responsible, and determine whether effects of intramammary infection could be detected by use of mastitis indicator tests commonly used for cows. DESIGN: Observational study. ANIMALS: 100 llamas on 10 farms. PROCEDURE: Milk samples were evaluated by bacterial culturing and by determination of somatic cell count (SCC), using direct microscopic and automated counting methods, California Mastitis Test score, pH, and N-acetyl-beta-d-glucosaminidase activity. Correlation coefficients were determined among the various mastitis indicator tests, and test results were determined for milk from infected and uninfected glands. RESULTS: Evidence of intramammary infection was evident in 76 of 369 (21%) milk samples, with 54 of 94 (57%) llamas having at least 1 infected gland. Staphylococcus sp other than Staphylococcus aureus were the predominant pathogens. None of the llamas had clinical signs of mastitis, and significant differences were not detected in SCC, California Mastitis Test score, pH, or N-acetyl-beta-d-glucosaminidase activity between infected and uninfected samples. California Mastitis Test scores were negative or trace for 307 of 313 (98%) samples, and SCC were low. In contrast, pH and N-acetyl-beta-d-glucosaminidase activity of milk from uninfected glands were higher than values reported for milk from uninfected cows, and neither variable was significantly correlated with the number of somatic cells in samples of llama milk. CLINICAL IMPLICATIONS: Although intramammary infections develop in llamas, inflammation (mastitis) appears to be rare. Values for mastitis indicator tests used for cows cannot be directly extrapolated to llamas. Subclinical mastitis is apparently not an important problem in llamas in the United States.

Visualization of inheritance patterns from graphic representation of additive and dominance relationships between animals.

Evaluation of pedigrees of normal and affected individuals help to suggest possible patterns of inheritance. Because large numbers of individuals are involved in studies of genetic disease, classic two-dimensional family tree charts are difficult to draw. Instead, DFA plots of graduated circles, weighted by dominance relationships, inbreeding, and additive relationships between individuals can be plotted above, on, and below the diagonal. Base animals without phenotypic measurements contribute information for computation of approximate dominance relationship, inbreeding, and additive relationships, but are not explicitly in the graph. Plotting only a set of randomly selected animals for each combination of phenotypes improves the visualization effect, especially when pedigrees are large or when computer resources are limited. For deficiency of uridine monophosphate synthase and interdigital hyperplasia, DFA plots showed higher densities of additive and dominance relationships among affected animals. However, DFA plots did not show clear patterns of inheritance for heel erosion, laminitis, or sole ulcers because environmental effects were important for those traits. Grouped graduated circles also improved visualization. The function of DFA plots is comparable with statistical scatter plots that display data to help examine statistical approaches. The DFA plots serve as a first approach to evaluate genetic hypotheses before a more complex model is fit.

Utilization of supplemental fat by dairy cows fed diets varying in content of nonstructural carbohydrates.

Sixteen Jersey cows were used in a Latin square design to determine milk production and composition when the cows were fed supplemental fat in diets varying in nonstructural carbohydrate content. Eight cows were used in a second experiment to assess ruminal fermentation and nutrient digestibilities. Diets were 1) high nonstructural carbohydrates, no added fat; 2) high nonstructural carbohydrates, 2.5% added fat; 3) low nonstructural carbohydrates, no added fat; and 4) low nonstructural carbohydrates, 2.5% added fat. Diets consisted of alfalfa haylage, corn silage, and concentrate (22:22:56, DM basis). Soyhulls replaced corn grain in diets 3 and 4; high and low diets contained 37.3 and 27.2% nonstructural carbohydrate. The DMI, milk production, and milk fat content were not affected by fat or nonstructural carbohydrates, although milk production tended to be higher when cows were fed fat. Fatty acid composition and N distribution of milk were unchanged by nonstructural carbohydrates. Supplemental fat decreased contents of CP, casein N, and true protein N in milk. Low nonstructural carbohydrates increased total VFA concentration and percentage of acetate and decreased percentages of propionate and butyrate in ruminal fluid. Total fatty acid digestibility decreased when cows were fed fat. Digestibilities of fiber components and total fatty acids were higher for diets low in nonstructural carbohydrates. Dietary content of nonstructural carbohydrates did not affect production of milk or milk components by Jersey cows fed supplemental fat.

Monoclonal antibodies specific for rat relaxin. VIII. Passive immunization with monoclonal antibodies throughout the second half of pregnancy reduces water consumption in rats.

Recent studies demonstrated that exogenous relaxin promoted drinking in nonpregnant rats. The purpose of this investigation was to determine the influence of endogenous relaxin on water consumption in pregnant rats. To that end, a monoclonal antibody specific for rat relaxin, designated MCA1, was used to passively neutralize endogenous relaxin throughout the second half of pregnancy in intact rats. Five milligrams of highly purified MCA1 were administrated iv to rats daily from days 12-22 of pregnancy. Controls received either a monoclonal antibody for fluorescein (monoclonal antibody control) or PBS (vehicle control). The amount of water consumed and both the total duration of water consumption and the total number of episodes when water was consumed were determined daily during both dark and light periods for all treatment groups. From days 13-22 of pregnancy, all three of these parameters of water consumption increased during the 10-h dark period (P < 0.01), but not during the 14-h light period. The mean daily water consumption in MCA1-treated rats was significantly less than that in controls (P < 0.05). Relaxin's effects on water consumption were limited to the 14-h light period (P < 0.01). No difference was found in daily water consumption between the MCA1-treated and control groups during the 10-h dark period. There was a tendency during the light period for both the total duration of water consumption (P = 0.06) and the total number of episodes when water was consumed (P = 0.13) to be less in MCA1-treated rats than in controls. Food consumption and body weight increased as pregnancy progressed, but no differences were found among the three treatment groups. We conclude that endogenous relaxin has effects on water consumption. It promotes water consumption during the daily light period in the second half of pregnancy in rats. Thus, relaxin may be a dipsogenic agent.