Paternal half-sib heritability and genetic correlation estimates were obtained utilizing data from 578 Hereford bulls from 66 sires. Bulls were maintained in three lines (weaning weight, postweaning gain and control) of an ongoing selection project. Growth performance traits studied were adjusted 205-d weaning weight, 365-d weight, individual feed efficiency, sonoray fat thickness and postweaning gain. Heritability estimates for these traits were .15 +/- .17, .33 +/- .19, .46 +/- .21, .28 +/- .18 and .52 +/- .21, respectively. Scrotal measurements taken were circumference of both testes and length and diameter of right testis at 205 and 365 d of age. Heritability estimates were .08 +/- .20, .07 +/- .20 and .28 +/- .24 at 205 d, and .44 +/- .24, .16 +/- .21 and .40 +/- .24 at 365 d, respectively. Excised testes traits, circumference, right testis length, diameter and weight, total sperm in the testes and sperm/gram of testes had heritability estimates of .21 +/- .26, .19 +/- .26, .02 +/- .24, .63 +/- .27, .14 +/- .21 and -.13 +/- .18, respectively. Genetic correlations of scrotal measurements at 205 d with scrotal measurements at 365 d and excised testes traits were negative. Scrotal measurements at 365 d had high positive genetic correlations with excised testes size, weight and total sperm. These relationships suggest that selection for increase of scrotal size at 365 d should increase testes size and weight and sperm numbers. Genetic correlations of weights and gain with scrotal measurements at 365 d and excised testes characteristics were moderate to high, in a favorable direction. Genetic correlations of testes traits with feed efficiency were essentially zero, while those with fat thickness were moderately positive. These results suggest that increasing testes size should not adversely affect growth performance traits except through the reduction in selection intensity.

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SummaryTwo hundred barrows and gilts were slaughtered at 100, 113 and 127 kg live weight. The sample was comprised of 36 litters, of which six litters within each breed of sire (Duroc, Hampshire and Yorkshire) were classified as fat litters (2.36 cm) and six litters classified as lean litters (2.16 cm) on the basis of litter mean backfat probes taken at 68 kg live weight.Growth traits were evaluated from 9 weeks of age until the designated slaughter weight. Carcasses from the first replication (18 litters) were evaluated for percentage separable lean, fat and bone and those from the second replication (18 litters) were evaluated for percentage closely trimmed lean cuts.The fat and lean groups had similar carcass length, longissimus muscle area and percentage closely trimmed lean cuts. The fat group had significantly thicker backfat, lower percentage separable lean and a higher percentage separable fat than the lean group. The three weight groups tended to have similar average daily gains and feed efficiencies for the total test period. As slaughter weight increased from 100 to 127 kg there was an increase in carcass backfat thickness (P<.05) and longissimus muscle area (P<.01). Percentage separable lean, fat and bone of carcass were similar at each of the three slaughter weights. The 127 kg group tended to have lower percentages closely trimmed lean cuts a Journal

Data on 118 Duroc, Yorkshire and reciprocal cross boars were utilized to evaluate the effect of crossbreeding on mating behavior. Boars were penned with an estrous gilt on 2 consecutive days. Number of mounts (proper and improper), sexual interest score and whether a successful mating occurred were recorded. Times at which each of these events occurred were recorded also, allowing calculation of times to first mount, to final mount and to completion of mating. Most importantly, more crossbred boars completed a mating than purebred boars (69 vs 27%). Crossbreds had greater sexual interest (P less than .05), more mounts and a higher proportion of properly oriented mounts (P less than .05). Crossbreds also began mounting activity (first mount, first proper mount and final mount; P less than .05) earlier and required less time to complete a mating (P less than .05) than purebred boars. Heterosis values for number of proper and improper mounts, proportion of proper mounts and sexual interest were 2, 53, 32 and 52%, respectively. Time to first mount, to final mount and to completing mating had heterosis values of -34, -29 and -20%, respectively. Scrotal measures taken at 140 and 168 d and at post-trial castration, as well as excised testes measures and sperm numbers, showed heterosis; however, no consistent associations between these traits and behavior traits were found. These data suggest that crossbred boars were more sexually active than purebred boars, perhaps due to an advanced physiological or behavioral stage.