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Bovine embryos were produced in vitro using a 2 2 design of modified medium (KSOM or SOF) and oxygen concentration (5% or 20%). Day 7 blastocysts were transferred in bulk (n = 11, on average) to recipient heifers and recovered non-surgically at Day 14. In two replications of a Latin square, eight heifers received embryos from each combination of factors. Recovered embryos were evaluated for trophoblast length and width, as well as the presence and diameter of an embryonic disc (ED). An ED was detected in a higher percentage of embryos that had been cultured in KSOM than SOF (72% v. 46%, respectively; P < 0.05). The aim of a second series of experiments was to associate Day 14 morphology with subsequent developmental capacity. In vitro-produced blastocysts were transferred (n = 17?20) on Day 7 to each of eight heifers and recovered at Day 14. Thirty-eight blastocysts were retransferred to heifers following morphological evaluation. Embryos in which an ED with no signs of degeneration had been detected maintained more pregnancies than other embryos in which an ED had either shown signs of degeneration or had not been detected (5/8 v. 2/30, respectively; P < 0.01). Further investigation into ED integrity at the elongating stage may contribute to our understanding of pregnancy establishment and maintenance.

Cumulus removal CR at the zygote stage is necessary for most mammalian in vitroproduction IVP. Present techniques use high fluidic stresses vortexing or mechanical stress with enzymatic treatment pipetting to remove cumulus. Herein a recently developed microfluidic device for cumulus removal from zygotes is compared with traditional vortexing. Microfluidic CR µFCR increased development on day 2 20 ± 4 to 35 ± 6, p< 0.01 and blastocyst formation at day 8 33 ± 1 to 57 ± 5, p< 0.01 when compared to vortex CR. Vortexing effects on embryo development were studied; 15, 30 and 120 s vortex doses. Development at day 2 was inversely proportional to duration of vortexing. An in situtranscription assay was used to assess biochemical activity of zygotes after cumulus removal. There was a spike of RNA transcription of vortexed zygotes at 2 h post CR not seen in the microfluidic treatment. These results suggest the potential for microfluidic methods to enhance production efficiencies while providing insight into basic developmental mechanisms.

Several researchers in the U. S. and Canada have investigated the effect of row spacing on yield and other agronomic traits of small grains with variable results. The objective of this study was to compare the performance of spring barley (Hordeum vulgareL. emend Bowden) seeded in a very narrow row spacing (7.5 cm) with two row spacings (15 and 30 cm) commonly used in production agriculture and in experimental research. Three genotypes were planted at Madison, WI, in 1975 and 1976, in a St. Charles silt loam soil (Typic Hapludalf, fine‐silty, mixed, mesic) and at Arlington, WI, in 1977, in a Plano silt loam soil (Typic Arguidoll, fine‐silty, mixed, mesic). A seeding rate of 134 kg/ha was used in all row spacings. The three environments had yield levels ranging from high to low, due primarily to differences in rainfall. When results were combined over environments, 7.5 cm‐rows yielded 4% more grain than 15‐cm rows and 12% more grain than 30‐cm rows. These differences were significant, but differences were not always significant for a single environment. Straw yield response to row spacing was similar in magnitude to the grain yield response. The increased grain and straw yields in narrower rows were attributed to greater tillering. There was significantly less lodging in 7.5‐cm rows than in 15 and 30‐cm rows in the two environments in which lodging occurred. Although the grain and straw yield improvements in this study may not be large enough to encourage changing to grain drills with a row spacing narrower than 15 cm, the reduced lodging in 7.5‐cm rows may be an added advantage when lodging is substantial.

Hypotheses of a negative association between fraternity size (size of litter in which an individual develops prior to birth or is reared following birth) and ovulation rate or litter size were tested by examining reproduction of females born or reared in varying prenatal and postnatal fraternities. Gilts were randomly assigned to develop prenatally and be reared postnatally in small or large fraternities. Dams of experimental animals were randomly assigned to one of two prenatal fraternity size treatments, either unilateral oviductal ligation (to bear a small prenatal litter) or no ligation (to bear a normal prenatal litter). Whereas this did result in differences (P< .01) in litter size at birth (small = 6.2 ± .4 vs large = 9.6 ± .9), there was considerable overlap in observed litter sizes between ligated and nonligated dams. Consequently, effects of prenatal fraternity size were examined by regression. Distinct differences in postnatal fraternity size were created by randomly assigning piglets to small (5 piglets) or large (10 piglets) postnatal fraternities within 24 h of birth. Differences in postnatal fraternity size were maintained through weaning at 3 wk (small = 4.9 ± .1 vs large = 9.4 ± .2). Weights at birth (regression of birth weight on prenatal fraternity size = −.07 ± .02, P< .01) and weaning (small = 6.09 ± .15 vs large = 5.46 ± .17 kg, P< .01) were heavier for gilts from small prenatal and postnatal fraternities, respectively, compared with gilts from large fraternities. Effects of prenatal and postnatal fraternity size on BW did not persist following weaning (P> .20). Both prenatal fraternity size (regression of fetus number on prenatal fraternity size = −.24 ± .11, P< .05) and postnatal fraternity size (small = 12.03 ± .58 vs large = 10.86 ± .68, P< .10) influenced number of fetuses at 30 d of gestation. Prenatal fraternity size also was negatively associated with ovulation rate (regression of ovulation rate on prenatal fraternity size = −.26 ± .13, P< .05). Differences in ovulation rate between postnatal fraternity classes followed the same pattern, but they were not significant. Neither prenatal nor postnatal fraternity size affected (P> .15) age at first estrus. No interactions of prenatal and postnatal fraternity size were observed for any of the traits examined (P> .15).

Weight and individual feed consumption data collected on 160 beef, dairy and beef × dairy dams and their progeny were used to estimate postweaning feed efficiency of progeny and several measures of lifetime cow efficiency for cows fed either a high or a low energy diet. Cow efficiency was expressed as the ratio of output to input where output included relative values for either progeny slaughter weights, carcass weights or trimmed wholesale cut weights plus cow weight; and input included pre- and postweaning feed consumption of progeny and lifetime feed consumption of the dam. In the first approach, life cycle cow efficiency was estimated by expressing output as a ratio to input when weight and feed consumption were weighted by their expected occurrence in a theoretical herd consisting of 100cows and 20 replacement heifers. Expected occurrence was a function of the age distribution of the cow herd and percentage calf crop. In the second approach, actual lifetime cow efficiency was estimated by expressing output as a ratio to input when all components were weighted equally. Both approaches included efficiency estimates calculated with and without cow calvage value. Diet of dam had little effect on efficiency of postweaning gain when progeny were slaughtered at age-constant end points. Dams fed low energy diets generally were equal or superior to those fed high energy diets in lifetime efficiency. Straightbred Holsteins mated to Hereford sires were less efficient than straightbred Herefords mated to Holstein sires, even though they produced progeny with heavier slaughter weights, carcass weights and trimmed wholesale cut weights, lower preweaning feed consumption and more efficient postweaning gains, in addition to possessing greater salvage value. The low efficiency ratios of Holstein dams were associated with their large metabolizable energy intake. Progeny of Simmental X Holstein and Chianina X Holstein dams tended to be more efficient than progeny of Hereford X Holstein and Angus X Holstein dams in the conversion of feed to postweaning gain. Hereford X Holstein and Simmental X Holstein dams were nearly equal in lifetime efficiency, while Angus X Holstein and Chianina X Holstein dams were slightly less efficient. Efficiency of production improved as number of progeny slaughtered increased.

Postweaning weight gains, feed consumptions and feed efficiencies, and slaughter weights, carcass weights and trimmed wholesale cut weights of progeny of 160 beef, dairy and beef × dairy dams fed high or low energy diets are reported. These traits represent progeny components of input and output needed to estimate lifetime cow efficiency to a slaughter end point. Diet of dam had little effect on postweaning gain, feed consumption and feed efficiency of progeny. Progeny of dams receiving the high and low energy diets also had similar slaughter weights, carcass weights and trimmed wholesale cut weights. In experiments initiated in 1964 and 1969, second and third progeny of Holstein dams had greater postweaning gains, consumed more metabolizable energy (ME) and tended to be more efficient in the conversion of feed into gain than progeny of Hereford, Hereford × dairy or Hereford × beef dams. In the first parity, Holstein progeny were second to Here ford progeny in gain and efficiency of gain. Progeny of Holstein dams had the heaviest slaughter weights, carcass weights and trimmed wholesale cut weights, but tended to have the greatest fat thickness over the longissimus muscle at the 12th rib and the lowest percentage of the carcass in trimmed wholesale cuts. Progeny of the larger breeds (Simmental × Holstein and Chianina X Holstein ) tended to gain more rapidly, consume more feed and convert the feed into gain more efficiently than progeny of the smaller breeds (Hereford X Holstein and Angus X Holstein) in the time constant postweaning interval used in an experiment initiated in 1974. Simmental × Holstein and Chianina X Holstein breed groups ranked highest in progeny output as measured by slaughter weights, carcass weights and weight of trimmed wholesale cuts. Progeny of these two breed groups had low fat thicknesses over the longissimus muscle, low dressing percentages and a high percentage of the carcass in trimmed wholesale cuts relative to Hereford X Holstein and Angus X Holstein progeny.

The precision of estimates of realized genetic parameters obtained from multiple-trait selection experiments is considered. Statistical optimality theory is used in conjunction with Monte-Carlo techniques to investigate the relationship between index weights and the variability of the estimates. Results indicate that arbitrary choice of index weights is ill advised, and that with some prior knowledge (or good guesses) about the magnitudes of the genetic parameters, index weights can be identified that yield estimates with predictable variation.

The influence of breed or breed of sire and dietary regimen on age at puberty in heifers was determined in two experiments. Exp. 1 was a 2 × 2 factorial involving animals of two breeds (Hereford and Holstein), born January through June, 1969 and fed one of two dietary regimens, High (H) and Low (L). Exp. 2 was a 4 × 2 factorial involving crossbred, autumn born heifers out of Holstein dams, sired by Angus (AF), Hereford (HF), Simmental (SF) or Chianina (CF) bulls and fed one of two dietary regimens. In Exp. 1, Herefords were older at puberty than Holsteins. In Exp. 2 CF and SF were older than AF and HF, and CF were older than SF at puberty. In both experiments, H heifers reached puberty sooner than L heifers. There were no breed or breed - of - sire × diet interactions. In Exp. 1, there was a season of birth × diet interaction (P<.01). Heifers on the H regimen that were born in the spring reached puberty earlier than winter-born H heifers while the opposite occurred among L heifers. Regression coefficients of age at puberty on birth date (January 1 = d 1) were −.69(P<.05), −.19, −1.00 (P<.005) and 1.86 (P<.01) for the Holstein H and L and Hereford H and L groups, respectively. Most of the animals in the first three groups reached puberty before June of the year following their birth, while Hereford L-fed heifers reached puberty between June and August, suggesting that date of attainment of puberty may have affected the relationship between age at puberty and birth date. In Exp. 2, the winter environment appeared to delay the onset of puberty. Most of the L heifers reached puberty in the summer, autumn or subsequent spring and few became pubertal during the intervening winter, causing a bimodal distribution of the dates of puberty attainment. Most of the H-fed heifers reached puberty before November, but puberty appeared to be delayed in those that did not. In Exp. 1, H heifers were heavier and had greater weight/height at puberty and consumed more TDN to puberty than L heifers. The opposite occurred in Exp. 2, presumably because seasons of birth differed between experiments and more L than H heifers did not reach puberty before winter in Exp. 2. Because H and L heifers reached puberty at different weights and levels of fatness, as measured by weight/height, dietary regimen did not appear to affect age at puberty by altering the time needed to attain a certain body weight or composition. We concluded that heifers fed diets low in energy reached puberty later than those fed diets high in energy and that breed or breed - of - sire differences in age at puberty were not affected by dietary regimen. Season affected age at puberty and may have altered the effect of nutrition and other factors on pubertal traits.

The interaction between dietary regimen and breed or breed of sire on postpartum reproduction was examined in two experiments. Exp. 1 was a 2 × 2 factorial involving two breeds (Hereford and Holstein) and two dietary regimens, high (H) and low (L). In Exp. 2, females out of Holstein dams and sired by bulls of four breeds, Angus (AF), Hereford (HF), Simmental (SF) and Chianina (CF) were used in a 4 × 2 factorial with two dietary regimens. Postpartum traits were observed for three consecutive postpartum periods (PP1, PP2, PP3), beginning after first calving. In Exp. 1, Holsteins tended to have longer intervals to first estrus (IE) and had longer intervals to conception (IC, P<.025) than Herefords in PP1 but not in PP2 or PP3. Cows fed H diets had significantly shorter IE and IC in PP1 and PP2, but not in PP3. Interval to conception was not recorded in PP3. There were breed × diet interactions for IE in PP1 (P<.06) and PP2 (P<.10) as differences in IE between L and H diets were more pronounced for the Holsteins than for the Herefords. Though not significant, Herefords fed L diets tended to have shorter intervals between estrus and conception than other groups in PP1 and PP2. In Exp. 2, breed of sire did not significantly affect any postpartum reproductive traits. Cows fed the H diet had shorter (P<.10) intervals to first estrus in PP1 and shorter (P<.05) intervals to first ovulation (10) in PP2 than L-fed cows. Interval to first ovulation was also shorter for H-fed cows in PP1, but the differences were not significant. The differences in IE between L and H diets tended to be greater for AF and HF cows than for SF and CF animals for PP1, but the interaction was not significant. The HF cows fed L diets had longer IE in PP2 than HF cows fed H diets, but the other breed - of - sire groups were not influenced by dietary regimen, resulting in a breed of sire × diet interaction (P<.10). Multiple regression analysis indicated that cows fed L diets that produced more fat-corrected milk and consumed less total digestible nutrients (TDN) from 0 to 56 d postpartum had longer IE during PP1. Fat-corrected milk production, TDN intake, weight at calving and change in body weight from 0 to 56 d postpartum were not significantly related to IE for cows receiving H diets during PP1. Data from PP2 and PP3 were pooled across diet groups for multiple regression analysis. None of the factors included in the model were significantly related to IE. We concluded that the influence of diet on postpartum reproductive function interacted with breed and parity and that the influence of level of milk production on IE varied with dietary level and parity. Because diet influenced reproduction more in Holsteins than Herefords, the use of dairy breeds in beef production may necessitate diets higher in energy to achieve maximum reproductive performance.

Log-linear and generalized least-squares approaches to analysis of categorical data are briefly introduced. Two data sets are analyzed to illustrate the methods of analysis.

Effects of cow size on cow productivity and calf performance were evaluated in Hereford cows. Cows were divided into four size groups based on the August weight taken during the summer following breeding for the second calf crop. Wither height was also taken at that time. Differences in the weight to height ratios and condition scores of the four size groups were highly significant. Very large cows were the fattest as well as the largest in body size. Compared to the herd average, small, medium, large and very large cows weaned −1.5, +3.6, +11.2 and −6.7% weight of calf/cow exposed, respectively. Expressed as ratio to cow metabolic weight, calf weaning weight/cow exposed was 1.63, 1.39, 1.51 and 1.15 and weight of calf slaughtered/cow exposed was 4.10, 3.47, 3.77 and 2.90 for small, medium, large and very large cows, respectively. Birth weight, preweaning daily gain and adjusted weaning weight were significantly greater for calves out of medium and large cows than for calves out of small and very large cows. The significant differences in weaning weight attributable to size of dam were maintained throughout the postweaning period, but postweaning growth and efficiency of steers were not significantly affected. At a constant age, all carcass weight and weight-related traits of steers were significantly affected by cow size. At a constant weight, the effects of cow size on most carcass traits of steers were not significant.

Twenty-four postpartum cows were used to determine the effects of suckling and exogenous gonadotropin-releasing hormone (GnRH) on pituitary-ovarian function and reproductive performance. Twelve cows were suckled, and calves were removed from the other 12 within 24 hr after birth. Six cows in the suckled group (S) and six in the nonsuckled group (NS) were injected with 250 µg GnRH on day 5 postpartum (parturition = day 0). The remaining animals in each group were injected with saline. Pituitary response to GnRH was estimated by measuring serum luteinizing hormone (LH) concentrations in blood collected hourly beginning 2 hr before and continuing until 9 hr after injection. Ovarian structures were observed by laparoscopy on days 5 and 8 postpartum. Injection of GnRH caused an increase (P<.05) in circulating LH concentrations in all animals. LH concentrations were highest 2 hr after injection. The area under the LH response curve was greater (P<.05) for NS than for S cows. Average daily LH concentrations during the first 25 days postpartum were higher in NS (2.4 ± .4 ng/ml) than in S cows (1.5 ± .3 ng/ml) because no ovulations occurred in the S group during this period. Ovaries of NS cows had greater (P<.01) follicular volume on day 5 than did ovaries of S cows (1,194 mm3vs195 mm3) because of a greater number of medium and large follicles, but estrogen concentrations were not significantly different on day 5 (NS = 6.7 ± .9 pg/ml; vsS= 7.4 + 1.8 pg/ml). On day 8, follicular volume was increased in GnRH cows and S cows (GnRH = 2,338 mm3vsno GnRH = 588 mm3and NS = 2290 mm3vsS = 637 mm3). Estrogen concentrations on day 8 were higher in S + GnRH cows (9.3 ± 2.1 pg/ml) than in S + saline (4.9 ± .6 pg/ml), NS + saline (5.7 ± .9 pg/ml) and NS + GnRH (6.3 ± .7 pg/ml) cows. Day to day repeatability of estrogen concentrations within animals, within treatment groups was estimated by intraclass (intracow) correlations. Correlations of estrogen values determined from days 6 to 25 were .38, .69, .56 and −.03 for the S + saline, S + GnRH, NS + saline and NS + GnRH groups, respectively. Correlation coefficients between LH and estrogen were .06, .08, .63 and .36 for the NS + GnRH, NS + saline, S + GnRH and S + saline groups, respectively. Intervals from parturition to first estrus and first ovulation were shorter (P<.01) for NS cows (14.9 and 9.6 days) than for S cows (57.6 and 36.8 days). Progesterone concentrations after first ovulations indicated the occurrence of short luteal phases in all NS cows. They had shorter intervals from calving to conception than S cows but required more inseminations per conception. GnRH treatment of NS cows had no significant effect on any intervals. However, five of the six S + GnRH-treated cows had shorter (P<.05) intervals to conception than dis S + saline-treated cows. It was concluded that calf removal hastens reestablishment of postpartum reproductive activity by eliminating a suppressive effect on pituitary gonadotropin release caused by suckling, which in turn causes hastened ovarian follicular development.

A model for swine fecundity that includes the effect of fraternity size is given. Over a range of plausible values for the parameters of the model, the dam-daughter correlation for number born tended to be negative. Thus, selection of replacement gilts born and reared in large litters would not bring about desirable genetic changes in litter size.