Factors affecting milk yield and reproductive performance

Dairy Herd Improvement testing records of 201 dairy herds of sizes from under 100 to over 1000 cows and herd average milk yields from under 5,000 to over 10,000 kg were studied. Average days to first postpartum breeding tended to be less in herds of over 500 cows. Herds of 300 to 600 cows had highest production per cow. Herds with higher average yields averaged shorter intervals to first postpartum breeding and fewer days open. Days open included farrow cows arbitrarily assigned 305 days open. Number of breedings changed little as herd yield increased, but days open for highest producing herds averaged one estrous period shorter than for low producing herds, suggesting better detection of estrus. For the individual cow, high yield or associated factors have a small but real antagonistic association with reproductive efficiency. Days to first breeding, to last breeding, and days open increased .27, .80, and .61, and number of breedings increased .014 for each 100 kg increase in 180-day yield of fat-corrected milk. The record averages of high-producing herds indicate this antagonism may be overshawdowed by good management; effective estrus detection probably is a major factor.

Genetic aspects of lactation curves

Parameters of lactation curves were defined by a gamma-type function for 113,705 lactations from the California Dairy Herd Improvement Association. Heritabilities and genetic correlations were estimated from a mixed-model analysis of paternal half sisters for first, second, third, and later lactations. Daily milk production on day 6 postpartum was estimated from production at first test-day to reduce the percentage of atypical lactations to less than 1% instead of an expectation of 30% without estimating production for day 6. The natural logarithm of the gamma-type function was ln(yt) = ln(a) + b ln(t) - ct, where yt was daily milk production in the tth week and ln(a), b, and c were coefficients. Persistency (c-(b+1)), week of peak yield (b/c), peak yield (a(b/c)be-b), and coefficient of determination were estimated from coefficients for each lactation. Heritabilities in first lactation were: ln(a) . 10 +/- .01, b .06 +/- .01, c .14 +/- .02, persistency .02 +/- .01, week of peak yield .02 +/- .01, peak yield .23 +/- .02, and determination .03 +/- .01. Heritabilities for later lactations were similar. Cows in first lactation had lower ln(a), lower peak yield, lower c, greater persistency, and took longer to reach peak yield than did cows in later lactations. Genetic and phenotypic correlations indicated that selection for increased peak yield would be associated with increased ln(a), b, and c without changing persistency or week of peak yield.

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.

Milk and fat yields decline in bovine leukemia virus-infected Holstein cattle with persistent lymphocytosis

Effects of bovine leukemia virus (BLV) infection on milk and fat yields were studied by using data collected from Holstein cows over a 6-year period. Milk and fat yields in BLV-infected cows with persistent lymphocytosis (PL) declined significantly relative to their BLV-infected non-PL herdmates. Declines were most pronounced in cows older than 6 years. The estimated loss to the dairy industry due to PL is more than $42 million annually. A major histocompatibility complex class I (BoLA-A) allele that has been previously associated with resistance to PL was associated with longevity and realization of milk production potentials, indicating that genetic resistance to PL will have an economic benefit in herds where BLV is endemic.

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.

Multiple concurrent stressors in chicks. 1. Effect on weight gain, feed intake, and behavior

Effects of multiple concurrent stressors on Hubbard x Hubbard chicks (Days 10 to 17 posthatch) were studied in a 2(6)-factorial experiment that employed as treatments aerial ammonia (A, 0 or 125 ppm), beak trimming (B, sham handled or beak trimmed/cauterized), coccidiosis (X, gavage with 0 or 6x10(5) sporulated Eimeria acervulina oocysts), intermittent electric shock (E, 0 or between 2.9 and 8.7 mA), heat stress (H, 30.4 or 34.8 C) and continuous noise (N, 80 or 95 dB). All stressors, except noise, decreased weight gain (G), increased coefficient of interindividual variation in gain (CV-G), and decreased feed intake (F) and feed conversion efficiency (G/F). Of a possible 57 interactions, only four were significant for G, two for CV-G, and of a possible 26 interactions, only two were significant for F, none for G/F. As number of simultaneous stressors ("order") increased, G, F, and G/F decreased and CV-G increased, all linearly. Time chicks spent standing was increased by X; time spent eating increased by X; and time spent drinking decreased by H. No effect of order and few stressor interactions were detected for the behaviors. Although behavior results were inconclusive with respect to synergism, antagonism, or additivity of stressors' effects, performance results indicated that chicks responded to each stressor occurred singly or concurrently with up to five others. The results suggest that in practical production situations, where ordinarily poultry experience more than one stressor at the same time, effects of multiple concurrent unrelated stressors on performance may be estimable to a first approximation by summing effects of respective stressors when acting alone.

Milk and fat production in dairy cattle influenced by advanced subclinical bovine leukemia virus infection

Genetic potentials (pedigree-estimated breeding value) for milk and for fat were compared in cows grouped according to subclinical stage of bovine leukemia virus infection. Genetic potential for milk production was significantly greater in seropositive cows with persistent lymphocytosis (622 +/- 72 kg) and in seropositive hematologically normal cows (554 +/- 34 34 kg) than in seronegative herdmates (418 +/- 53 kg). When 305-day twice-daily-milking mature equivalent milk production records for the current lactation were adjusted for genetic potential, bovine leukemia virus-infected cows that were hematologically normal had significantly greater milk production than did seronegative herdmates, suggesting that early bovine leukemia virus infection was positively associated with milk yield. Genetic potential for fat production was significantly greater for cows with persistent lymphocytosis (21 +/- 2 kg) than for other seropositive (16 +/- 1 kg) and seronegative herdmates (13 +/- 2 kg); however, 305-day twice-daily-milking mature equivalent fat production for the current lactation was not significantly different between the groups. Thus, cows with persistent lymphocytosis did not produce fat according to their genetic potential. As an apparent consequence of tendencies for greater milk yield and less fat production, milk fat percentage was significantly reduced in cows with persistent lymphocytosis (3.33 +/- 0.09%) and other seropositive cows (3.48 +/- 0.05%) relative to seronegative herdmates (3.67 +/- 0.07%). These results suggest a need to reevaluate the economic impact of bovine leukemia virus infection on the dairy industry.

Effects of formaldehyde treated soybean meal on milk yield, milk composition, and nutrient digestibility in the dairy cow

The nutritional value of soybean meal that had been treated with formaldehyde (.3 g/100 g) to inhibit microbial degradation of soybean meal protein in the rumen was investigated. Four experimental diets were fed ad libitum during wk 4 to 43 of lactation to Holstein cows randomly assigned to diets in a 2 x 2 factorial arrangement of dietary crude protein (12 and 14%) and formaldehyde treatment (untreated and treated soybean meal). Concentrate, corn silage, and alfalfa-grass hay provided 53.0, 35.4, and 11.6% of the daily intake of dry matter. Analysis of covariance revealed that digestibility of dietary crude protein by cows fed formaldehyde treated soybean meal was lower than by cows fed untreated soybean meal (62.4 versus 65.4%). Similar quantities of milk, 4% fat-corrected milk, milk fat, and milk solids-not-fat (overall means of 7998, 7402, 281, and 660 kg/301 days of lactation) were produced by cows fed different diets. This was true whether the data were summarized during peak production (day 22 to 63), during days 22 to 119 when crude protein intake did not meet requirements, or during the complete experiment (days 22 to 301 of lactation). Milk protein (total nitrogen x 6.38) produced by cows fed soybean meal treated with formaldehyde was less than by cows fed untreated soybean meal during days 22 to 63 and during days 22 to 119 (47 versus 44 kg/cow and 103 versus 97 kg/cow). Changes in body weight of cows during lactation were similar among treatments. Treating soybean meal with .3 g formaldehyde/100 g may decrease availability of soybean meal protein for use by lactating dairy cows.

Monoclonal antibodies specific for rat relaxin. IV. Passive immunization with monoclonal antibodies during the antepartum period reduces cervical growth and extensibility, disrupts birth, and reduces pup survival in intact rats

The purpose of this investigation was to use an approach targeted specifically on endogenous relaxin to determine the influence of antepartum (days 20-22) relaxin on cervical modifications and birth in the rat. To that end, a monoclonal antibody specific for rat relaxin, designated MCA1, was used to neutralize endogenous relaxin in intact pregnant rats. MCA1 or PBS vehicle was administered iv to intact rats daily from days 20-22 of pregnancy. Cervices were removed at 1200 h on day 22. Cervices obtained from MCA1-treated rats were less extensible than cervices obtained from PBS-treated control rats. Furthermore, wet weight, dry weight, water content, and uronate content were lower in cervices obtained from MCA1-treated rats than in cervices from PBS-treated controls. Birth and maternal behavior of MCA1-treated and PBS-treated control rats were observed continuously from 2100 h on day 22 until day 2 postpartum (d2PP). MCA1-treated rats exhibited significantly prolonged durations of litter delivery as well as reduced incidences of live pups on d2PP compared with controls. There were lower incidences of normal maternal behavior observed at birth and on d1PP with MCA1-treated rats than with control rats. In addition, little or no milk was observed in the abdomen of most live pups of MCA1-treated rats on d2PP, whereas abundant milk was observed in the abdomen of all live pups of control rats. The mean live pup weight on d2PP was lower in the litters of MCA1-treated rats than in control litters. The present study indicates that in the rat endogenous relaxin is needed during the antepartum period for normal cervical growth and extensibility, normal litter delivery, and high postpartum pup survival. This work supports the hypothesis that the influence of endogenous relaxin on birth is attributable, at least in part, to its effects on the cervix.

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.

Embryonic mortality attributed to inherited deficiency of uridine monophosphate synthase

The deficiency of uridine-5'-monophosphate synthase is inherited as an autosomal recessive trait in Holstein-Friesian cattle. Heterozygotes are characterized by half normal activity of uridine monophosphate synthase, as measured in erythrocytes. Matings between heterozygotes for the deficiency have produced 31 pregnancies lasting at least one month, but only 23 full-term calves, including 9 homozygous normal and 14 heterozygotes. That the eight embryos were not carried to term is consistent with the probability of a homozygous-deficient genotype and are lost around 40 d of gestation. Although the homozygous deficiency of uridine monophosphate synthase is lethal embryonically in cattle, homozygotes for the analogous human condition have been born alive.

Postpartum distribution of costs and disorders of health

More than 17,000 events from 1,305 lactations of 551 cows in two herds were analyzed to quantify the distribution of costs and disorders of health during a lactation. Categories were mammary, reproduction, locomotion, digestion, respiration, other, insemination, and total. The largest costs and most disorders were associated with initiation of lactation rather than period of peak daily milk yield. Mammary and reproductive costs were 71% of total health cost in the first 30 days postpartum. Mammary and reproductive costs were 55% of the total health cost in an average 30-day interval. Insemination cost was 50% of the total health cost between 60 to 89 days postpartum. Parturition and extended days open were periods of large reproductive cost. Postpartum distributions of health cost and health disorders were similar implying that the prices assigned for severity added little information to counting disorders.

Inheritance of UMP synthase in dairy cattle

The inheritance of uridine-5'-monophosphate (UMP) synthase in dairy cattle was consistent with a two-allele, single-autosomal-locus model. Two phenotypes were associated with different levels of the enzyme in bovine erythrocytes. The predominant phenotype (assumed normal) had twice the concentration of UMP synthase as the second phenotype (deficient). A one-to-one correspondence between enzyme level and genotype identified one homozygote as normal, the heterozygote as deficient, and the other homozygote as unobserved. Three alternative hypotheses were rejected. The deficiency as homozygous recessive was rejected because 20 matings between assumed normal males and deficient females resulted in 10 normal and 10 deficient offspring. The hypothesis that the deficiency was homozygous dominant was rejected because the 95 percent confidence interval about the observed gene frequency, 0.0024 to 0.0146, did not contain the estimated gene frequency for equilibrium between an average 10(-5) mutation rate and selection against the deficiency as homozygous dominant. Analyses of female relatives implicated one bull as deficient (96 percent probability), as he had, independently, 2 deficient daughters, 5 deficient granddaughters from untested dams, and 3 deficient great-granddaughters from untested ancestors. The hypothesis that the deficiency was sex-linked was rejected because 3 of 9 tested sons of the putative deficient bull were deficient. Calf mortality is expected in 25 percent of matings between deficient animals.

Hormonal control of the cervix in pregnant gilts. I. Changes in the physical properties of the cervix correlate temporally with elevated serum levels of estrogen and relaxin

The time course of changes in the physical properties of both the uterine and vaginal portions of the cervix were studied during the last two thirds (days 40 to approximately 115) of pregnancy in the gilt. To obtain insight concerning the hormonal control of these physical changes, serum levels of relaxin, estrone, 17 beta-estradiol, and progesterone were also determined. Throughout midpregnancy, the extensibility (softness), lumen diameter, and wet weight of the uterine portion of the cervix were less than those of the vaginal portion of the cervix. After day 80, marked and sustained increases in these three physical parameters occurred in the uterine portion of the cervix whereas slight (extensibility) or moderate (lumen diameter and wet weight) increases occurred in the vaginal portion of the cervix. By day 110, extensibility, lumen diameter, and wet weight of the uterine portion of the cervix were similar to those of the vaginal portion of the cervix. Because the uterine portion of the cervix has a relatively firm consistency and small lumen throughout most of pregnancy, we conclude that it probably plays a more important role than the vaginal portion of the cervix in protecting the uterus and its contents during pregnancy. The marked changes in the physical properties of the uterine portion of the cervix are temporally correlated with elevated serum estrogen levels (days 80-100) or estrogen and relaxin levels (day 100 to term). We conclude that estrogen or, more likely, estrogen and relaxin in combination may promote the modifications in the physical properties of the cervix that occur during the last 35 days of gestation.

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.

Effects of prostaglandins on the bovine corpus luteum: granules, lipid inclusions and progesterone secretion

Corpora lutea collected at 15, 30 and 60 min after prostaglandin F2 alpha (PGF2 alpha) treatment were compared to control corpora lutea at 60 min after saline treatment. There were decreases (P less than 0.05) in the relative percentages of cytoplasm occupied by granules in large luteal cells (LLC) by 30 min and in small luteal cells (SLC) by 60 min. Differences were not observed among the groups for lipid inclusions. Luteal progesterone was decreased at all post-PGF2 alpha treatment times when compared to 60-min controls (P less than 0.05). PGF2 alpha was then compared with prostaglandin F1 alpha (PGF1 alpha), prostaglandin E1 (PGE1), and 17-phenyl-18,19,20-trinor-prostaglandin F2 alpha (17-phenyl-PGF2 alpha) in 60-min trials with plasma progesterone and luteinizing hormone (LH) determined every 5 min. LH was not affected by these treatments. Like PGF2 alpha, 17-phenyl-PGF2 alpha induced a greater loss of granules from LLC then SLC. 17-phenyl-PGF2 alpha also induced an increase in the lipid content of LLC. Treatments with PGF2 alpha and 17-phenyl-PGF2 alpha were associated with decreased concentrations of luteal progesterone but PGF1 alpha and PGE1 were without effect on this variable. In contrast to PGF1 alpha, PGE1 increased both luteal progesterone and the area occupied by cytoplasmic granules. The latter effect was greater in LLC than SLC.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection and prevalence of UMP synthase deficiency among dairy cattle

A partial deficiency of UMP synthase has been detected in Holstein dairy cattle. Since affected females secrete milk with elevated concentrations of orotate, milk orotate was used to screen for the condition among 880 cows in 17 randomly selected Holstein herds in Illinois. Mean orotate was 85.0 +/- 1.5 microgram/ml milk and 17 cows had milk orotate in excess of 170 micrograms/ml. Including the latter animals, 42 cows were evaluated for erythrocyte UMP synthase and 15 were found to be partially deficient. Thus, at least 1.7 percent of all cows had the condition; this is a minimal estimate because the initial screen was milk orotate and this may be low, particularly early in lactation. Deficient cows had half the level of UMP synthase as normal, nondeficient cows (1.30 +/- 0.06 vs. 2.79 +/- 0.10 units/ml). The binomial classification of deficient versus normal accounted for 72 percent of the variation noted in UMP synthase. Milk orotate was significantly elevated in deficient cows (337.8 +/- 31.3 micrograms/ml), validating its use as a screening device. Urinary orotate also was higher for deficient cows (28.4 +/- 5.2 vs. 9.2 +/- 0.8 micrograms/ml) and differentiated the two groups as well as milk orotate. Normal and deficient cows did not differ in milk lactose concentrations. Erythrocyte UMP synthase also was measured in 85 Holstein bulls used for artificial insemination and 6 had low levels of UMP synthase (1.39 +/- 0.19 vs. 2.92 +/- 0.05 units/ml); the binomial classification accounted for 42 percent of the variation. The partially deficient animals identified appear to be heterozygotes for a condition expected to be lethal in the homozygous state.

Effects of ruminal exposure on the amino acid profile of heated and formaldehyde-treated soybean meal

Rumen cannulated Holstein steers, fed corn silage and a corn-soybean grain mixture twice a day, were used to compare the effectiveness of heat and formaldehyde treatments in preserving the amino acid profile of soybean meal exposed to ruminal fermentation for 12 h. Formaldehyde treatments were 0, .3, .6, and .9 g/100 g soybean meal. Defatted soybean flakes treated at 250, 250, 215, and 180 degrees C for 30, 20, 20, and 25 min, respectively, and unheated soybean meal comprised the heat treatments. The in situ polyester bag technique was used to obtain estimates of ruminal degradation of the treated and untreated soybean meals and to obtain undegraded residues from the soybean meals following 12 h of rumen exposure. Diaminopimelic acid was used to assess the extent of bacterial contamination. Significant amounts of apparent diaminopimelic acid were detected in unexposed samples (2.0 to 7.6% of soybean nitrogen) and in residues (4.8 to 12.7% of residue nitrogen). Significant differences in amino acid contents were detected between untreated and heat-treated soybean meals and their respective residues. Formaldehyde treatment was effective in preserving the original amino acid profile of soybean meal.

Comparative responses of lactating cows to total mixed rations or computerized individual concentrates feeding

A trial was conducted in a commercial dairy herd in which the concentrate part of the ration was fed individually to a group of cows through computerized self-feeders. Performance results were compared with those of a group fed TMR of 65 to 67% concentrates. Rationing of individual concentrates was according to parity, milk yield, milk yield potential, BW changes, and bunk feed-stuffs. Mean intake of concentrates per cow was about 1 kg/d lower in the individually supplemented cows. This was partly compensated for by a higher intake of bunk feedstuffs. Overall daily milk yield per cow was similar to those receiving a TMR in first parity cows, higher in second parity cows, and lower in third and greater parity cows. The higher performance of the second parity cows was achieved in all milk yield potential classes, and the lower yield in subsequent lactations was due to lower performance in low and high potential classes. The individually supplemented cows gained less BW than those in the TMR group. Milk yield per unit of BW was better than milk yield as a variable to refine individual cow supplementation strategy for allocation of concentrates. Results also suggest that the same criteria used for supplementation of concentrates can be beneficial to cows' assignments and movements among different TMR groups. Computerized dispensing of concentrates, when applied properly, can economize on consumption of concentrates when grouping and feeding different TMR are impossible.

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.

Rare earth elements as markers for rate of passage measurements of individual feedstuffs through the digestive tract of ruminants

Rumen and in vitro abomasal fluid incubations of four feeds, soybean meal (SBM), 0.3% formaldehyde-treated SBM, cottonseed meal and ground corn, each labeled with one of two markers (Sm and La) were conducted to estimate the extent of marker movement from the feeds. Feeds were marked by spraying acidic solutions of the marker movement from the feeds. Feeds were marked by spraying acidic solutions of the markers uniformly over the feeds. Concentration of marker on the feeds, on the feed residues remaining in polyester bags after 12 hours of incubation in the rumen, and on the feed residues after 12 hours of incubation in the rumen and 3 hours of in vitro incubation in abomasal fluid were determined by neutron activation. Initial concentration of the markers on the feeds was used as a covariable in analysis of the restricted randomized block design. Marker concentration of Sm and La, for all feeds, averaged 1115 +/- 44 and 1503 +/- 44 ppm after the rumen incubation and 959 +/- 54 and 1666 +/- 54 ppm after the combined incubations and differed (P less than 0.01) from the mean initial marker concentration of 1294 +/- 42 ppm. Abomasal incubations allowed estimation of marker movement (contamination) between bags. For both markers, increases (P less than 0.01) were observed in marker contamination when compared to initial levels. Marker contamination increased from 2.5 +/- 0.8 to 20.1 +/- 0.1 and 10.7 +/- 0.8 ppm for Sm and La, respectively. Data indicate significant marker movement and suggest that Sm and La, when applied to feeds by this method, are not suitable markers for estimating passage rates of individual feedstuffs.

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.

Lactation potential as a criterion for strategy of feeding total mixed rations to dairy cows

A trial was conducted from freshening to 30 wk postpartum to evaluate assignment of cows into production potential groups based on early lactation performance to optimize the time for switching from high to medium nutrient concentration TMR. Cows received a TMR formulated for early lactation until wk 4 of lactation and a high nutrient concentration TMR until 13, 19, or 25; the high TMR was followed by a medium nutrient concentration TMR until the end of the trial. Cows were assigned to high, medium, or low potential groups separately for parities 1, 2, and > or = 3 based on daily 3.5% FCM production as a percentage of BW measured during wk 6 and 7 of lactation. Low potential cows tended to partition energy intake into BW gain earlier in lactation than medium and high potential cows. For low potential cows, an early transfer to medium TMR moderated BW gain with no negative effect on production. High potential cows maintained their BW on the high ration; however, early transfer negatively affected production. Classification of individual cows into potential groups based on early lactation performance can serve as a useful tool for TMR feeding strategy later in lactation.

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.

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.