Maternal Granddam Research Articles

36 Factors influencing racing performance in Polish Thoroughbreds and Purebred Arabian horses

Horse racing serves as a performance test to evaluate the speed and endurance of horses. Globally, the breed most widely used for racing is the Thoroughbred. In Poland, the Purebred Arabian horse racing sector size is comparable to that of Thoroughbreds, as the racing merit is a crucial element of the complex Polish breeding goal for Arabian horses. In many cases, the elite Thoroughbred mares – both in Poland and internationally – fail to perform as broodmares. However, the heritability of racing performance is proven to be higher in the dam line than in the sire line. In contrast, elite Polish Arabian racing mares usually produce elite racing offspring, and this relationship is observed through many generations. Polish State Studs conduct a particular racing program for the best racing mares, who are bred with race-type stallions (without the novel French-origin sire lines). The aim of this study was to identify the factors influencing the racing performance of Polish Thoroughbreds and Purebred Arabians and compare the effects of these factors in both breeds, with special emphasis put on the effect of dam's racing performance on the racing performance of their offspring. 1099 Thoroughbreds and 1022 Purebred Arabians were included in this study. The impact of each factor was evaluated using logistic and mixed linear regression models. We also created a correlation matrix to find additional dependencies between variables. In both Thoroughbreds and Purebred Arabians, a positive relationship between the racing performance of dams and their offspring was observed, except the elite Thoroughbred mares’ (4+ wins) progeny, which had 7,918% less chance ( P < 0,001) to enter the race. The chance for progeny both for entering the race and for good racing performance decreased with the dam's age. For instance, Arabian horses out of mares 13 years and older had 17,856% less chance ( P < 0,001) than the offsprings of mares aged 4–6. The age of the maternal grand-dam was significant in one of the models. Additionally, the fixed effects of the sire and maternal grandsire were significant, leading to the conclusion that at least 2 generations of ancestors must be considered while analyzing the chances of an individual performing well at the racetrack. A small percentage of the phenotypic variation explained by applied models suggests the importance of various fixed and temporary environmental effects affecting racing performance. The general conclusion is that in both breeds, the offspring of young mares with good but not elite racing performance has the best chances to win a race.

Grandparental effects in marine sticklebacks: transgenerational plasticity across multiple generations.

Nongenetic inheritance mechanisms such as transgenerational plasticity (TGP) can buffer populations against rapid environmental change such as ocean warming. Yet, little is known about how long these effects persist and whether they are cumulative over generations. Here, we tested for adaptive TGP in response to simulated ocean warming across parental and grandparental generations of marine sticklebacks. Grandparents were acclimated for two months during reproductive conditioning, whereas parents experienced developmental acclimation, allowing us to compare the fitness consequences of short-term vs. prolonged exposure to elevated temperature across multiple generations. We found that reproductive output of F1 adults was primarily determined by maternal developmental temperature, but carry-over effects from grandparental acclimation environments resulted in cumulative negative effects of elevated temperature on hatching success. In very early stages of growth, F2 offspring reached larger sizes in their respective paternal and grandparental environment down the paternal line, suggesting that other factors than just the paternal genome may be transferred between generations. In later growth stages, maternal and maternal granddam environments strongly influenced offspring body size, but in opposing directions, indicating that the mechanism(s) underlying the transfer of environmental information may have differed between acute and developmental acclimation experienced by the two generations. Taken together, our results suggest that the fitness consequences of parental and grandparental TGP are highly context dependent, but will play an important role in mediating some of the impacts of rapid climate change in this system.

Genetic analysis of body weight in South African Angora kids and young goats

The data used for this study consisted of 27 485 kid records, the progeny of 599 sires and 10 077 dams, and were collected on the 2000- to 2009-born kids of 11 Angora goat studs. Variance and covariance components and ratios pertaining to direct additive genetic variation, maternal additive genetic variation, maternal permanent environmental variation, and the relationship between direct and maternal effects for birth weight (BW; kg), weaning weight (WW; kg) and body weight at 8, 12 and 16 months (W8, W12 and W16; kg) were estimated with the ASReml program. Direct additive heritability estimates of 0.22, 0.20, 0.12, 0.34 and 0.58 were obtained for BW, WW, W8, W12 and W16, respectively. Maternal heritabilities were 0.10, 0.09, 0.03 and 0.06 for BW, WW, W8 and W12, respectively, while maternal environmental effects of 0.13, 0.11, 0.06 and 0.04 were estimated for the latter traits, respectively. An unfavourable correlation of &#8211;0.38 was obtained between direct and maternal genetic effects for BW. Low to medium positive direct genetic correlations were estimated between birth weight and body weights recorded at a later stage in life. High positive direct genetic correlations were estimated among WW, W8, W12 and W16. The maternal genetic correlations obtained between birth weight and the other body weights were medium to high. Phenotypic correlations among the traits ranged from low to high. Genetic trends of body weight at different ages indicate that although not many breeders use objective measurement as a selection tool, body weight increased slightly in the 11 studs over the 10-year study period. Since reproduction and body weight should be included in a selection programme for Angora goats, the relationship between the direct and maternal additive effects should be clarified. The importance of a sufficiently structured and related pedigree, especially on the part of the dams and maternal grand dams, has been highlighted in this study. As this is one of the constraints of this data set, data collection in the Angora goat industry should continue until a suitably structured data set has been built up that could be used to estimate multi-trait breeding values for the industry.Keywords: Birth weight, genetic parameters, maternal effects, weaning weight

Bayesian estimation in maternally ancestral animal models for weaning weight of beef cattle1

The Bayesian approach was implemented for fitting several maternally ancestral models for weaning weight data of Angus calves. The goal was to evaluate to what extent genetic evaluation models with additive grand maternal effects (G), or with an ancestrally structured covariance matrix for maternal environmental effects (E), or with a sire × year interaction (ISY), or combinations thereof (GE, GSY, ESY, GESY), redistribute the additive variability and reduce the negative magnitude of the additive correlation between direct and maternal effects (r(AoAm)), when compared with the regular maternal animal model (I). All animals with records had known dams and maternal granddams. The sampling scheme induced low autocorrelations among all variables and tended to converge quickly. The signs of the estimates of r(AoAm) were consistently negative for all models fitted. The magnitudes of the estimates of r(AoAm) from models E, G, GE, ESY, and GESY were almost one-third of those from models I and ISY. Inclusion of the sire × year interaction had some effect in reducing the negative magnitude of r(AoAm), but also reduced the size of the estimates of direct (h(0)(2)) and maternal (h(m)(2)) heritabilities. In comparison, models E or G reduced the negative magnitude of r(AoAm) by 0.50 units and produced more favorable estimates of H(0)(2) and h(m)(2) than models I and ISY. The estimate of h(0)(2) from G was similar to the one from I; however, the estimated h(m)(2) was 0.04 units greater, whereas the estimate of r(AoAm) was much less negative (-0.21 vs. -0.71) than the respective estimates from I. The environmental correlation between the weaning weights of dams and their daughters (λ) was estimated to be -0.28 ± 0.03 in E and ESY, and -0.21 ± 0.03 in GE and GESY. Inclusion of the sire × year interaction effect by itself did not have much of an impact in the reduction of the estimated magnitude of r(AoAm). Rank correlations among EBV for direct effects were larger than 0.94 and did not show any appreciable difference among models, whereas the rank correlation among maternal breeding values displayed differences in the ranking between I and the other models. Models E and ESY recovered the largest amount of total additive variability with maternal effects.

P2Y12 receptor gene mutation associated with postoperative hemorrhage in a Greater Swiss Mountain dog

A novel hereditary disorder of platelets was identified across 5 generations of a family of Greater Swiss Mountain dogs. The first dog identified with the mutation bled excessively following routine ovariohysterectomy and required multiple transfusions. Coagulation screening assays, platelet counts, and von Willebrand factor antigen activity were within reference intervals. Flow cytometric studies indicated that platelets from the affected dog expressed normal levels of glycoproteins IIb and IIIa and responded to 2 platelet-activating agents, convulxin and platelet-activating factor, but not to ADP. Based on DNA studies, a 3 base-pair deletion predicted to result in elimination of a serine from the extracellular domain was identified in the gene encoding P2Y12, an ADP receptor protein located on platelet membranes. Flow cytometric analysis of platelets and studies of DNA performed concurrently on 2 unrelated Greater Swiss Mountain dogs were unremarkable. The mutation was subsequently identified in the sire, the maternal grand-dam, a maternal great grandparent, a paternal great grandparent, and a great-great grandparent. The sire was homozygous, but had not yet been identified as having a hemostatic disorder; the other 4 dogs were carriers. This is the first report of a mutation in the gene encoding the ADP receptor P2Y12 in a domestic animal. P2Y12 is the same receptor targeted by ticlopidine and clopidogrel, platelet inhibitors used in lieu of aspirin in people at risk for cardiovascular disease; thus, spontaneous bleeding is not expected unless there are other contributing factors. This disorder is particularly troublesome because spontaneous hemorrhage is absent to mild in affected dogs; however, following routine surgical procedures or trauma, excessive bleeding could occur and have possible fatal consequences.

Gene flow in a national cross-breeding beef population

Future progress in genetic improvement and the monitoring of genetic resources in beef cattle requires a detailed understanding of the population under selection. This study examines the gene flow in the UK beef population with an uncommon breeding structure involving interaction between the beef and dairy populations. British Cattle Movement Service records were used as the primary source of information, and these data were triangulated with UK government statistics, other industry information sources and existing literature to build up a profile of the UK beef industry. Estimates were made of the breed composition of suckler cows, breeding bulls and the prime slaughter population. Cross-bred animals made up 85% and 94%, respectively, of the commercial beef breeding cow and prime slaughter populations. Holstein/Friesian (through cross-breeding) made up the largest proportion of genes in both these populations with 33% and 28%, respectively. The next five most popular breeds were specialist beef breeds: Limousin (22% and 18%), Charolais (11% and 6%), Simmental (9% and 11%), Angus (7% and 8%) and Belgian Blue (6% and 6%). Combined, the top seven beef breeds accounted for 94% of beef genetics in the prime slaughter population, and 80% of this came from non-native breeds. The influence of dairy breeds in the commercial beef breeding population was highlighted by the fact that 44% of replacement commercial beef breeding females were sourced from beef-sired crosses in the dairy herd, and in total 74% of all maternal grand dams of prime slaughter animals were Holstein/Friesian. The use of selection index technology was also investigated by analysing breeding bull sale results, with the correlation between the terminal sire index and sale price of young breeding bulls being generally moderate but significant, ranging from 0.21 to 0.38 across the major beef breeds. The most influential source of genetics in the commercial suckler beef herd was natural service breeding bulls. These were mostly sourced from pedigree breeders, and accounted for 47.8% of the genetics in the prime beef population. Artificial insemination sires were responsible for 16.6% of prime beef genetics, with the remaining 35.6% coming from dairy breeds, 95% of which was Holstein/Friesian.

Postweaning growth and carcass traits in crossbred cattle from Hereford, Angus, Brangus, Beefmaster, Bonsmara, and Romosinuano maternal grandsires1,2

The objective of this study was to characterize breeds representing diverse biological types for postweaning growth and carcass composition traits in terminal crossbred cattle. Postweaning growth and carcass traits were analyzed on 464 steers and 439 heifers obtained by mating F(1) cows to Charolais and MARC III (1/4 Hereford, 1/4 Angus, 1/4 Pinzgauer, and 1/4 Red Poll) sires. The F(1) cows were obtained from mating Angus and MARC III dams to Hereford, Angus, Beefmaster, Brangus, Bonsmara, and Romosinuano sires. Traits evaluated were postweaning ADG, slaughter weight, HCW, dressing percentage, percentage of carcasses classified as USDA Choice, LM area, marbling score, USDA yield grade, fat thickness, retail product yield (percentage), and retail product weight. Maternal grandsire breed was significant (P < 0.05) for all traits. Animals with Angus grandsires grew faster and had the heaviest carcasses, with the greatest percentage of carcasses classified as USDA Choice and the greatest marbling scores when compared with other grandsire breeds. Animals with Romosinuano and Bonsmara inheritance grew slower, had the lightest weights at slaughter, the lightest carcass weights, the least percentage of carcasses classified as USDA Choice, and the least amount of marbling and fat thickness. Animals with inheritance from these 2 breeds had a more desirable yield grade with the greatest retail product yield. Maternal granddam breed was significant (P < 0.05) for marbling score, USDA yield grade, fat thickness, and retail product yield. Sex class was significant (P < 0.05) for all traits except for retail product yield. Steers grew faster, were heavier, had heavier carcasses, and were leaner than heifers. Heifers had a greater dressing percentage, a greater percentage of carcasses classified as USDA Choice, a greater LM area, and a decreased yield grade when compared with steers. Sire and grandsire breed effects can be optimized by selection and use of appropriate crossbreeding systems.

Genetic diversity and population structure of American Red Angus cattle1

The objective of this study was to characterize the population structure and genetic diversity of registered American Red Angus cattle. Inbreeding and average relationship coefficients, effective population size, effective number of founders, and effective number of herds supplying grandparents to the population were calculated from the recorded pedigree. Inbreeding in 1960 was 10.7% and decreased until 1974 at a rate of 0.2% per year, whereas in 1975 inbreeding was 3.2% and increased until 2005 at a rate of 0.02% per year. The numerator relationship coefficients of the 10 individual paternal grandsires (PGS; sires of sires), paternal granddams (PGD; dams of sires), maternal grandsires (MGS; sires of dams), and maternal granddams (MGD; dams of dams) that had the greatest number of registered grandprogeny, with all other registered animals, increased with their birth year from 1960 on. Average numerator relationships of these with all other PGS, PGD, MGS, MGD, bulls, and sires were greater for paternal (PGS, PGD) than maternal (MGS, MGD) pathways. The effective population size was 445, with 649 effective founders. The effective numbers of herds supplying PGS, PGD, MGS, and MGD were 435, 369, 453, and 459, respectively. Inbreeding is at a low level and the effective population size is large. The effective number of founders and effective number of herds supplying grandparents is small in relation to the total number of animals and herds, indicating the disproportionate influence of a few founders and herds on the genetics of the breed. The calculated parameters indicate satisfactory genetic diversity in American Red Angus cattle.

Postweaning growth and carcass traits in crossbred cattle from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu maternal grandsires1,2

The objective of this study was to characterize breeds representing diverse biological types for postweaning growth and carcass composition traits in terminal crossbred cattle. Postweaning growth and carcass traits were analyzed on 434 steers and 373 heifers obtained by mating F1 cows to Charolais sires. Maternal grandsires represented Hereford, Angus, and MARC III (1/4 Hereford, 1/4 Angus, 1/4 Pinzgauer, and 1/4 Red Poll) dams to Hereford or Angus (British Breeds), Norwegian Red, Swedish Red and White, Wagyu, or Friesian breeds. Breed groups were slaughtered serially in each of 2 yr (2002 and 2003). Postweaning ADG, slaughter weight, hot carcass weight, dressing percentage, percentage Choice, LM area, marbling score, USDA yield grade, fat thickness, retail product yield (percentage), retail product weight, fat yield (percentage), fat weight, bone yield (percentage), and bone weight were analyzed. Maternal grandsire breed was significant (P < 0.05) for all traits except dressing percentage, percentage Choice, and LM area. Marbling score for animals with Norwegian Red, Wagyu, Swedish Red and White, British Breeds, and Friesian inheritance was 550, 544, 532, 530, and 515, respectively (SEM = 8). Retail product weight for these animals was 224, 211, 227, 223, and 223 kg, respectively (SEM = 2 kg). Maternal granddam breed was not significant for any of the traits analyzed. Grandsire breed effects can be optimized by selection and use of appropriate crossbreeding systems.

Relative economic weights of maternal versus direct traits in breeding schemes

In genetic improvement schemes, the economic values of traits in the breeding objectives depend on time and frequency of realisation in offspring generations. A measure for this is the number of discounted expressions (NDE) derived by the gene flow procedure. These were calculated for two groups of traits or trait components: “Maternal traits” realised repeatedly during the life of the dam and “direct traits” realised once in early life of an animal. Selection was considered for purebred populations with a multi-purpose objective and for populations incorporated as specialised sire or dam breeds in a three-way crossbreeding scheme. The reproductive conditions of pigs, sheep, beef and dairy cattle were taken as example. For most realistic conditions in a purebred population, the marginal economic value for a maternal trait should be weighted with a factor between 0.55 and 0.60 of that for a direct trait. Much more relative weight should be given to maternal traits in dam breeds of a crossbreeding scheme, particularly in prolific species. Economic weights of maternal traits in a sire breed are generally negligible, but not when assuming a short investment period and inefficient use of terminal sires in the commercial level. If no reciprocal crosses of both types of F 1 dams are used, maternal traits are relatively more important in the breed used as maternal granddam of the terminal product than in that used in the grandsire position. These differences are higher for less prolific species.

Maternal grandsire, granddam, and sire breed effects on growth and carcass traits of crossbred cattle1,2

Postweaning growth, feed efficiency, and carcass traits were analyzed on 1,422 animals obtained by mating F1 cows to F1 (Belgian Blue x British breeds) or Charolais sires. Cows were obtained from mating Hereford, Angus, and MARC IIIHereford, 1/4 Angus, 1/4 Pinzgauer, and 1/4 Red Poll) dams to Hereford or Angus (British breeds), Tuli, Boran, Brahman, or Belgian Blue sires. Breed groups were fed in replicated pens and slaughtered serially in each of 2 yr. Postweaning average daily gain; live weight; hot carcass weight; fat depth; longissimus area; estimated kidney, pelvic, and heart fat (percentage); percentage Choice; marbling score; USDA yield grade; retail product yield (percentage); retail product weight; fat yield (percentage); fat weight; bone yield (percentage); and bone weight were analyzed in this population. Quadratic regressions of pen mean weight on days fed and of cumulative ME consumption on days fed were used to estimate gain, ME consumption and efficiency (Mcal of ME/kg of gain) over time (0 to 200 d on feed), and weight (300 to 550 kg) intervals. Maternal grandsire breed was significant (P < 0.01) for all traits. Maternal granddam breed (Hereford, Angus, or MARC III)was significant (P < 0.05) only for fat depth, USDA yield grade, retail product yield, fat yield, fat weight, and bone yield. Sire breed was significant (P < 0.05) for live weight, hot carcass weight, longissimus area, and bone weight. Sex class was a significant (P < 0.001) source of variation for all traits except for percentage Choice, marbling score, retail product yield, and fat yield. Interactions between maternal grandsire and sire breed were nonexistent. Sire and grandsire breed effects can be optimized by selection and use of appropriate crossbreeding systems.

Genetic parameters for lamb weight at different ages and wool production in Baluchi sheep

AbstractThe Baluchi breed is the most common native breed of Iran adapted to harsh environments in the eastern parts of the country. The data used in the present study, collected from two research flocks at the Abbasabad sheep breeding station in north-east Iran, included 20 534 animals descended from 363 sires, 5992 dams, 282 maternal grandsires, and 2865 maternal granddams during the period 1966 to 1989. The traits recorded were: birth weight (BW), weaning weight (WW), weight at 6 months (W6), weight at 12 months (YW), pre-weaning gain (WG), post-weaning gain (PWG), lamb fleece weight (LFW), ewe fleece weight sheared before first joining (FW1) and adult ewe fleece weight (FW). Genetic parameters, estimated with restricted maximum likelihood and a two-trait animal model, were similar in the two flocks. Direct heritabilities for the various body weight traits were moderate and varied between 0·13 and 0·32, while the maternal heritabilities were low and varied between 0·01 and 0·12. Direct and maternal genetic correlations between WW and weights at later ages were moderate to high (0·59 to 0·96). Direct heritabilities of weight gain measures varied between 0·12 and 0·19, while no significant maternal influence on either of these weight gain measures could be detected. The estimates of direct genetic correlation between WG and PWG were positive and varied between 0·54 and 0·74, while negative maternal genetic correlation (0·17 on average) between WG and PWG was detected. For LFW, direct heritability was low and no maternal heritability could be shown. For FW1, both direct and maternal genetic influences were demonstrated (0·07 to 0·26). Direct genetic correlation between LFW and FW1 was very low and close to zero, while maternal genetic correlation was positive and relatively high (0·72 on average). The relative contributions to phenotypic variance from variance components due to common environmental effects ranged from 0·01 to 0·15 for all traits. The repeatability of FW was low (0·03 to 0·12).

Genetic parameters for feed intake and efficiency in lactating beef cows

Genetic parameters of feed intake and efficiency and production traits for lactating beef cows were estimated from data collected from 1980 to 1988 at the Elora Beef Research Centre, Guelph, Ontario. Estimates were obtained using restricted maximum likelihood (REML) with an individual animal model with year–season–treatment, sex of calf, parity, breeding system, covariate daily change of backfat depth and direct genetic and permanent environmental effects. The data included 1174 observations, 511 cows, 369 dam–maternal grand dam pairs and 245 sires of cows. Feed efficiency for milk was calculated as milk yield relative to energy consumed for milk and maintenance and residual feed consumption as estimated energy intake minus energy requirements as estimated by the National Research Council. Heritabilities for Herefords alone and total data, respectively, were estimated to be 0.02 and 0.11 for cow's daily ME intake (MEI), 0.26 and 0.26 for daily milk yield (DMY), 0.45 and 0.33 for milk fat percentage (MFP), 0.29 and 0.40 for metabolic body weight (MBW), 0.21 and 0.10 for calf weaning weight as a proportion of cow weight at weaning (PPW), 0.18 and 0.11 for feed efficiency for milk (FE), and 0.23 and 0.03 for residual feed consumption (RFC). Genetic correlations of output (DMY) and input (MEI) were 0.31 for Hereford and 0.75 for the total data. Genetic correlations of RFC with both output (DMY) and input (MEI) were low. Genetically, PPW was positively associated with FE and DMY and negatively associated with MBW. Key words: Genetic parameters, feed efficiency, lactation, beef cow

Genetic parameters for feed intake and efficiency in dry pregnant beef cows

Genetic parameters of feed efficiency and traits relative to feed efficiency for dry pregnant beef cows were estimated from data collected from 1980 to 1988 at the Elora Beef Research Centre, Guelph, Ontario. Measurements of individual feed intake were available for 90 d immediately before calving. Estimates of parameters were obtained using derivative-free restricted maximum likelihood (DFREML), with an individual-animal model with year-season, sex of fetus, parity breeding system, covariate daily backfat change, and genetic and permanent environmental effects. The data included 729 observations, 337 cows, 278 dam–maternal grand dam pairs, and 208 sires of cows. Feed efficiency for pre-calving gain of fetus was calculated as pre-calving gain relative to energy consumed for maintenance and pregnancy, with adjustment of intake for weight change by National Research Council (NRC) standards (FE) or by regression analysis (FER). Residual feed consumption was calculated as energy intake minus energy requirements, with requirements estimated by NRC standards (RFC) or by regression (RFCR). Heritabilities for Hereford alone and total data, respectively, were 0.03 and 0.16 for daily metabolizable energy intake (MEI); 0.20 and 0.44 for metabolic body weight (MBW); 0.28 and 0.22 for fetal pre-calving average daily gain (PADG); 0.11 and 0.05 for FE; 0.28 and 0.20 for FER; 0.01 and 0.04 for RFC; and 0.03 and 0.22 for RFCR. Genetic and phenotypic correlations indicated a positive association of energy intake with pre-calving fetal gain and weight of cow, although correlations with weight of cow were low. Residual feed consumption for the total data was not genetically associated with MEI or PADG, moderately associated with MBW, and highly negatively associated with FE. Key words: Genetic parameter, feed efficiency, pregnancy, beef

Genetic relationships of lamb weight, maternal ability, and mature ewe weight in Swedish finewool sheep.

Genetic parameters were estimated for weights of lambs from birth to 1 d before slaughter and mature ewe weight (EMW) using REML procedures and single- and two-trait animal models. The data consisted of weight registrations from 5,001 animals descended from 131 sires, 788 dams, 48 maternal grandsires, and 530 maternal granddams in an experimental flock with Swedish finewool sheep. Direct heritabilities increased with lamb age from .07 for birth weight to .21 for weight before slaughter. Maternal heritabilities declined with age from .30 to .07. Direct-maternal genetic correlations were positive and increased with age from .11 for birth weight to .73 for weight before slaughter. For daily gain during shorter periods, direct heritability increased from .07 for the period from birth until 3 wk of age to .14 for the period from weaning until 1 d before slaughter. The values for maternal heritabilities were .16 and .03, respectively. The direct-maternal genetic correlations ranged from -.11 to .59. The direct heritability for EMW varied between analyses from .29 to .63. A nonsignificant maternal heritability of .22 was noted for EMW. Direct genetic correlations between EMW and various lamb weights varied between .36 to .85. Genetic correlations between direct effects on EMW and maternal effects on lamb weights varied between .39 and .53. Direct and maternal genetic correlations between the lamb weights were positive. The results showed that the maternal influence on lamb weights decreased with age. It was indicated that positive genetic relationships exist between ewe weight and maternal effects on lamb weight. Therefore, selection for larger lamb weights alone will not only increase ewe weights but also improve the maternal ability to the ewe.

EFFICIENCY OF FEED UTILIZATION BY THREE-BREED CROSS STEERS

Feed efficiencies, defined as feed-to-gain or weight ratios, were computed on 1046 steers reared between 1973 and 1978 at the Brandon Research Station. The progeny were out of 10 specific F1 crosses of dams mated to Charolais (C), Simmental (S), Limousin (L), and Chianina (Chi) bulls with none of the F1 dams being backcrossed. Dam crosses included the Hereford × Angus (HA) and crosses sired by C, S, and L bulls out of Hereford (H), Angus (A), and Shorthorn (N) dams. Feed-to-gain ratios were calculated on a live animal postweaning basis (for both a 140-d test and total liveweight gain from on-test to slaughter) and a carcass basis (hot carcass weight and rough or untrimmed lean, fat, and bone weights of combined cuts). The combined cuts were the rib, long loin (comprising the short loin and the sirloin butt), and round. In the live animal traits, the progeny from the 10 F1 dam crosses did not differ, but on a carcass basis, the progeny from the "exotic" crosses had better feed-to-gain ratios than the HA cross. Differences among the progeny of the "exotic" crosses included: C crosses &lt; L crosses, "exotic" × A and "exotic" × N &lt; "exotic" × H for hot carcass weight; "exotic" × N &lt; "exotic" × H for rough weight of the combined cuts; S crosses &lt; L crosses and "exotic" × N &lt; "exotic" × A for fat and bone weights of the combined cuts; and "exotic" × N &lt; "exotic" × H for fat weight of the combined cuts. There were no significant breed of dam's sire (maternal grandsire) × breed of dam's dam (maternal grand-dam) effects. Differences in breed of dam's sire were C &lt; S for 140-d test, C &lt; L for total liveweight gain, and S &lt; L for bone weight of the combined cuts. Breed of dam's dam differences were N &lt; (A = H) for fat weight of the combined cuts. Breed of terminal sire effects revealed that the progeny from the S and C breeds were similar for all measures of feed efficiency and the L and C breeds were only similar for feed efficiencies expressed on a carcass basis. Progeny from the Chi breed were comparable to the progeny from the C breed but not to the progeny from the S and L breeds in these traits. Key words: Beef cattle, breed crosses, steers, feed efficiency

Maternal heterosis and grandmaternal effects in beef cattle: postweaning growth and carcass traits.

Crossbred steer and heifer progeny from 5-, 6- and 7-yr-old dams produced in a four-breed diallel crossing experiment involving the Brown Swiss, Red Poll, Hereford and Angus maternal grandsires and maternal granddams were evaluated for postweaning growth and carcass traits to estimate breed mean maternal heterosis, maternal heterosis for specific breed cross females, average maternal heterosis for all crosses, breed grandmaternal effects and net breed effects in crosses. All progeny evaluated were born in 1979 and 1980 and were sired by 7/8 or 15/16 Simmental bulls. Average maternal heterosis was significant for 200-d weight in heifers but not in steers and was not significant for final weight (444-d) in either heifers or steers. The effects of maternal heterosis on postweaning growth were not important. Differences among breeds in mean maternal heterosis values were small for growth-related traits. Breeds did not differ (P greater than .05) in grandmaternal effects for growth-related traits; Brown Swiss tended to be highest, Red Poll lowest, with Hereford and Angus intermediate. Differences in net breed effects in crosses favored Brown Swiss over the three other breeds and were generally significant for growth traits. Average maternal heterosis, though generally positive, was not significant for carcass traits on either an age-constant or weight-constant basis. Differences among breeds were small in grandmaternal effects, specific heterosis and net effects in crosses for carcass traits associated with both weight or composition; generally the Brown Swiss breed was favored on carcass traits associated with weight in the age-constant analysis and generally had a higher lean-to-fat ratio than the three other breeds in both the age-constant and weight-constant analyses.

Maternal heterosis and grandmaternal effects in beef cattle: preweaning traits.

Crossbred progeny from females, 3 yr old and older, representing Brown Swiss (B), Red Poll (R), Hereford (H) and Angus (A) maternal grandsires and maternal granddams in a diallel crossing experiment were evaluated to estimate breed mean maternal heterosis (mean hMi) for each breed, maternal heterosis for specific breed cross females (hMij), average maternal heterosis for all crosses (mean hM) and breed grandmaternal effects (gM'i) for preweaning calf traits. Estimates of mean hM were significant for birth date and weight, 200-d weight and 200-d weight/cow exposed. Even though calves with crossbred dams weighed more at birth, they did not differ from calves with straightbred dams in frequency of calving assistance. The estimates of hMij were similar for most crosses and most traits, except 200-d weight and 200-d weight/cow exposed. The largest heterotic advantage was exhibited by progeny of BH reciprocal cross females, which exceeded crossbred progeny from BB and HH females for 200-d weight/cow exposed by 35.9 kg. The smallest heterotic effect was exhibited by crossbred progeny of RA reciprocal cross females. Progeny with R maternal granddams exhibited a higher (P less than .05) live calf born and weaned percentage than progeny with H maternal granddams. Progeny with B maternal granddams were born later (P less than .05) in the calving season than progeny with R maternal granddams. Progeny with A maternal granddams exhibited a lower frequency of calving assistance than progeny with H maternal granddams, and progeny with H maternal granddams were heavier (P less than .05) at 200 d than progeny with R maternal granddams. There was a tendency for estimates of breed grandmaternal effects (gMi) to exhibit an inverse relationship with estimates of breed maternal effects (gMi).

Estimation of Genetic Change in the Registered Holstein Cattle Population

We examined pedigrees of 440,702 males and 526,956 females born during 1960 through 1979 and registered in the herdbook of the Holstein Association. Annual trends in genetic merit of sires, dams, maternal grandsires, and maternal granddams were determined from their estimated transmitting abilities. Genetic merit of parents changed substantially after more accurate procedures for estimating transmitting abilities were introduced in 1968. Rates of change for genetic merit of sires were larger than corresponding changes in dams. Annual genetic change for the male and female populations was estimated by two methods. The sum of annual changes in the average estimated transmitting abilities of sires and dams yielded estimates of annual genetic change. In addition, estimates of annual genetic change were obtained by doubling trends in the animals’ average estimated transmitting abilities. Both methods yielded similar results in the female population. For 1971 to 1979, annual genetic change for females was approximately +55kg milk, +1.5kg milk fat, and −.007 milk fat percentage. In the male population, estimates differed between methods. Smaller estimates of annual genetic change resulted from doubling the rate of change in the bulls’ average Predicted Differences. This method should yield more accurate estimates of genetic change when bulls with genetic evaluations are representative of the population. Estimates of annual genetic change for 1971 to 1979 from the latter method were 84kg milk, 2.6kg milk fat, and −.006 milk fat percentage.

HOURLY DISTRIBUTION OF TIME OF PARTURITION IN BEEF COWS

Data on 1151 calvings recorded over a 4-yr period at the Agriculture Canada Research Station, Brandon, Manitoba were analyzed to examine the influence of various factors on the time of day of calving of beef cows. Factors examined were year of calving, sex of calf, age of cow, weight of cow, calf birth weight and breed type. The hourly distribution of calvings was relatively uniform over the 24-h period. Slightly more calves were born from 0700 h to 1900 h (51.5%) than between 1900 h and 0700 h. Breed of maternal grandsire and of maternal granddam were the only factors that appeared to influence the time of parturition. Percentages of calves born during the day (0700–1900 h) having Hereford, Charolais, Simmental and Limousin grandsires were 59.0, 54.2, 51.0 and 45.6, respectively, whereas 55.9, 55.6 and 41.0% of the calves from Hereford, Angus and Shorthorn granddams, respectively, were born during the day. The hourly distribution of 212 potentially abnormal calvings was significantly uneven. The highest incidence of abnormal calving occurred from 1100 h to 1500 h (22.2%) and the lowest from 2300 h to 0300 h (12.1%). Key words: Beef cows, parturition, hourly distribution