The Effects of Dietary Zinc Concentration and Source on Yearling Bull Growth and Fertility

Yearling Angus bulls (n = 325) were allotted by BW into six pens of equal size. One of three dietary treatments consisting of 1) dietary Zn at 40 ppm, all supplied by zinc sulfate (ZnS); 2) dietary Zn at 40 ppm with 33.3% supplied by zinc proteinate and 66.6% supplied by ZnS (ZnPS); or 3) dietary Zn at 60 ppm, all supplied by ZnS (ZnHi) was delivered to two pen replicates. Initial and final liver biopsies were collected and analyzed for Zn concentration. Scrotal circumference and BW measures were collected at the start and conclusion of the trial. Semen from bulls intended for public sale (n = 167) was collected and evaluated for motility and morphological abnormalities. Bulls with percent normal sperm cell counts < 70% or with motility scores less than fair (motility scores = poor, fair, good, and very good) were considered classification deferred (CD). Following 126 d of treatment, bulls on the ZnHi treatment had a greater (P=0.06) increase in liver Zn concentration than bulls on the ZnS treatment, but not bulls on the ZnPS treatment (P=0.18) (‒9.8, 1.2, and 20.6 ppm for ZnS, ZnPS, and Zn Hi, respectively). No differences in scrotal circumference or ADG were detected. Bulls receiving ZnPS had higher (P<0.05) percent normal sperm cells than did bulls receiving ZnS, but not bulls receiving ZnHi (55.5, 68.9, and 62.5% for ZnS, ZnPS, and ZnHi, respectively). The frequency of CD was less (P<0.05) for bulls on ZnPS and ZnHi treatments than for bulls on the ZnS treatment. In all fertility measures observed in this trial, bulls receiving the ZnPS rated greatest, followed by bulls on ZnHi, and lastly by bulls on ZnS.     

Effects of Feed Intake Restriction on Performance and Carcass Characteristics of Finishing Beef Steers,

Crossbred steers (n = 264, 311 ± 1.6 kg initial BW) were blocked by BW, randomly assigned to one of four treatments (28 pens, 7 pens per treatment), and fed a common 90% concentrate diet to determine the effects of the severity of caloric restriction on animal performance and carcass characteristics. Treatments were 1) ad libitum access to feed for 151 d (AL100); 2) 75% of DMI by AL100 for 65 d, 95% of DMI by AL100 for 65 d, and ad libitum access to feed for 21 d (AL85); 3) 80% of DMI by AL100 for 65 d, 100% of DMI by AL100 for 65 d, and ad libitum access to feed for 21 d (AL90); and 4) 85% of DMI by AL100 for 65 d, 105% of DMI by AL100 for 65 d, and ad libitum access to feed for 21 d (AL95). Feed was offered for AL85, AL90, and AL95 based on DMI by AL100 the previous week. All steers were fed a similar quantity of DM for 4 d prior to initial, interim, and final BW determinations to minimize gastrointestinal fill differences. Overall DMI was greater (P<0.01) for AL100 than for the average of the remaining treatments and decreased linearly (P<0.01) among AL95, AL90, and AL85. Overall ADG (carcass-adjusted) was less (P<0.01) for AL85, AL90, and AL95 than for AL100, whereas overall ADG:DMI (carcass-adjusted) did not differ (P>0.10) between AL100 and the average of the remaining treatments. Overall ADG and ADG:DMI (carcass-adjusted) responded quadratically (P<0.05) with increasing DMI restriction. Hot carcass weight, longissimus area, and kidney, pelvic, and heart fat percentage were greater (P<0.05) for AL100 than for the remaining treatments and responded quadratically (P<0.10) among AL85, AL90, and AL95. Marbling score was greater (P<0.10) for AL100 than for the average of the remaining treatments, and the number of carcasses grading Prime + Choice tended to be higher (P<0.15) for AL100 and AL95. Restricting feed intake of finishing yearling steers to an average of 85 to 95% of ad libitum for 130 d of a 151-d feeding period generally resulted in slower ADG, lesser marbling scores, and carcasses that were lighter and leaner compared with yearling steers allowed ad libitum to feed and harvested after an equal number of days on feed.     

Scrotal circumference in yearling Hereford bulls: adjustment factors, heritabilities and genetic, environmental and phenotypic relationships with growth traits

Field data on 4,233 yearling Hereford bulls were analyzed using fixed and mixed model least-squares procedures to examine factors affecting scrotal circumference; determine appropriate adjustment factors; and study genetic, environmental and phenotypic relationships among scrotal circumference and growth traits. Scrotal circumference was affected by postweaning feed level; contemporary group/feed level; age of dam; and covariates age, weight and height. Of the three covariates, weight had the greatest effect, and any factor which caused an increase in weight tended to increase scrotal circumference. Quadratic effects of age, weight, height and age X age of dam interaction effects were significant or approached significance, but were of minor importance. Large contemporary group effects suggested the need for expressing scrotal circumferences as trait ratios or as deviations from contemporary group means. Scrotal circumference adjustment factors recommended for yearling Hereford bulls were .026 cm X d-1 of age and .8, .2 and .1 for sons of 2-, 3- and 4-yr old dams, respectively. Heritability of weight-adjusted scrotal circumference was .46 +/- .06 compared with .49 +/- .06 for age-adjusted scrotal circumference, indicating considerable additive genetic variation for relative scrotal size. Correlations between scrotal circumference and growth traits were moderate to high. The genetic correlation between scrotal circumference and yearling weight was the highest of these at .44 +/- .16. Potential implications of this relationship are discussed.     

Alternative Ultrasound Predictors of Beef Carcass Longissimus Muscle Area

Longissimus width and depth were measured using ultrasound in steers (n = 174), bulls (n = 323), and heifers (n = 347) at yearling and prior to harvest. Yearling and preharvest muscle dimensions and carcass muscle area of bulls were largest (P<0.01). Steers had wider and deeper (P<0.01) longissimus than heifers at yearling; however, preharvest muscle width and depth and carcass muscle area were greater (P<0.01) for heifers. From yearling to harvest, muscle width of bulls and heifers increased at a similar rate, which was greater (P<0.01) than that of steers. Significant (P<0.01) differences existed for muscle depth increase from yearling to harvest, where bulls had the highest deposition rates, heifers had intermediate rates, and steers had the lowest deposition rates. Correlations of carcass muscle area with muscle depth were large and positive (0.52 to 0.81) and slightly larger than correlations with muscle width (0.51 to 0.74). Muscle depth was the best single predictor of carcass muscle area; however, two-trait prediction models including both muscle width and depth were superior to single-trait prediction models. At yearling (preharvest), predicted and carcass muscle areas differed by more than 9.68 cm² for less than 2% (5%) of steers and heifers and less than 7% (4%) of bulls. Further, yearling and pre-harvest carcass muscle area predictions were within 4.84 cm² of carcass measurements for approximately 54 to 65% of all animals, respectively. These results indicate that ultrasound muscle width and depth may be alternative predictors of carcass muscle area and may be useful in selection of potential replacements.     

Growth, puberty, and carcass characteristics of Brahman-, Senepol-, and Tuli-sired F1 Angus bulls

Postweaning growth, sexual development, libido, and carcass data were collected from two consecutive calf crops using 31 Brahman x Angus (B x A), 41 Senepol x Angus (S x A), and 38 Tuli x Angus (T x A) F1 bulls. Following weaning (by mid-September) and preconditioning, at the start of the study (late September) bulls were fed concentrate (three times each week at a rate equivalent to 4.5 kg/d) on bahiagrass pasture for approximately 250 d. At the start of the study and at 28-d intervals, BW, hip height, and scrotal circumference (SC) were measured. Concurrently at 28-d intervals, when the SC of a bull was > or = 23 cm, semen collection was attempted using electroejaculation. Ejaculates were evaluated for presence of first spermatozoa (FS), 50 x 10(6) sperm with at least 10% motility (PU), and 500 x 10(6) sperm with at least 50% motility (PP). After all bulls reached PP they were subjected to two libido tests. Carcass data were collected on all bulls (n = 110) and Warner-Bratzler shear (WBS) force values were assessed on a subset (n = 80). For both years, B x A bulls were heavier (P < 0.05) and taller (P < 0.05) than S x A and T x A bulls at the start and end of the study. However, breed type did not influence (P > 0.10) gain in BW or hip height during the study. Scrotal circumference of T x A bulls was larger (P < 0.05) than that of B x A or S x A bulls at the start of the study, but there was no effect (P > 0.10) of breed type by the end of the study. At PU and PP, B x A bulls were older (P < 0.05), heavier (P < 0.05), and taller (P < 0.05) and had larger (P < 0.05) SC than S x A and T x A bulls. Tuli x Angus bulls were younger (P < 0.05) than S x A bulls at PU and PP but had similar SC. Libido scores tended (P < 0.10) to be lower for B x A than for S x A and T x A bulls. Breed type affected (P < 0.05) carcass traits; B x A bulls had the heaviest (P < 0.05) hot carcass weight, greatest (P < 0.05) dressing percentage, larger (P < 0.05) longissimus muscle area than S x A bulls, and higher (P < 0.05) USDA yield grade than T x A bulls but greatest (P < 0.05) WBS force values. Breed type did not affect (P > 0.10) USDA quality grade. In conclusion, tropically adapted F1 bulls produced from Senepol (Bos taurus) and Tuli (Sanga) sires bred to Angus cows in Florida had lighter BW, shorter hip heights, and smaller carcasses than those from Brahman sires but reached puberty earlier and had higher libido scores and lower WBS force values.     

Crossbred bull selection for bigger scrotum and shorter age at puberty with potentials for better quality semen.

Shortening age at puberty of crossbred breeding bull is an important issue in the tropics. This study aimed at selecting crossbred bulls at earliest possible age with bigger scrotum and potential for donating quality semen. One hundred and 31 pre-joining crossbred bulls of Central Artificial Insemination Laboratory, Saver, Dhaka were examined. The bulls being trained by seeing semen collection from mature bulls were allowed ejaculation into the artificial vagina at homosexual mount during a 20 min time at three occasions, every three months. Eighty one of 131 bulls produced at least one ejaculate during the study and their mean +/- SD age and scrotal circumference (SC) were 20.3 +/- 4.7 months and 28.2 +/-2.7 cm, respectively. Bulls' body weight, body condition score (BCS) and SC influenced the attainment of their puberty (p < 0.05). Bull's body weight had positive effects on scrotal circumference and ejaculate volume (p < 0.05). Scrotal circumference positively influenced the percentages of normal spermatozoa (p < 0.05). Scrotal skin-fold thickness negatively influenced the proportion of spermatozoa with normal head (p < 0.05). Based on age at first ejaculate and SC, 29.6% bulls (n = 24) were selected by cluster analysis. Selected bulls had mean +/- SD age 17.9 +/- 2.2 months, body weight 287.3 +/-48.6 kg, SC 30.5 +/- 1.5 cm, ejaculate volume 3.4 +/- 1.3 ml, sperm motility 50.8 +/- 17.2%, total spermatozoa per ejaculate 2541.9 +/- 1699.2 million and normal spermatozoa 81.5 +/-14.5%. The selected pubertal bull group was different from the unselected pubertal bulls at MANOVA (p < 0.0001). About 30% of pubertal crossbred bulls can be selected with shorter age and larger scrotum at puberty under conditions prevailed in Bangladesh.     

Feed intake,digestibility and body weight change in Farta sheep fed hay supplemented with rice bran and/or noug seed (<Emphasis Type="Italic">Guizotia abyssinica</Emphasis>) meal

The study was conducted to determine the effect of supplementation with rice bran (RB) and /or noug seed (Guizotia abyssinica) meal (NSM) on feed intake, digestibility, and body weight (BW) change in hay based feeding of Farta sheep. Twenty five yearling Farta rams with a mean initial BW of 19.23 ± 0.28 kg were used in randomized complete block design arranged into five blocks of five animals. The five dietary treatments that consisted of hay alone (T₁), hay + RB (T₂), hay + mixture of RB and NSM at a ratio of 1:2 (T₃), hay + mixture of RB and NSM at a ratio of 2:1 (T₄) and hay + NSM (T₅) were randomly assigned to each sheep within a block. The supplements were daily offered at 300 g dry matter (DM) head⁻¹ in two equal parts at 800 and 1600 h. Supplementation improved the total DM and acid detergent fiber (ADF) intake (P < 0.05), organic matter (OM) intake (P < 0.01), crude protein (CP) intake (P < 0.001). The apparent digestibility of DM in T₅ was higher (P < 0.05) than in T₁ and T₂ and that of T₄ was also higher (P < 0.05) than in T₁. The apparent digestibility of CP in T₅ and T₄ were higher (P < 0.001) than in T₁ and T₂ and that of T₃ and T₂ were also higher (P < 0.001) than for T₁. The BW gain of experimental sheep was improved (P < 0.01) by supplementation with NSC (T₅) and/or its mixtures with RB (T₃ and T₄). The results of the study showed that supplementation with either of both mixtures of NSM and RB at 43% of total DM intake promoted better feed intake, digestibility and BW gain in Farta sheep.     

Scrotal circumference measurements on young Holstein bulls

Scrotal circumference was measured on all young Holstein bulls entering an artificial insemination center over a 57-month period. A total of 3,008 measurements were taken on 723 bulls between the ages of 5 and 18 months. Mean scrotal circumference, standard deviation, and 10th and 25th percentile statistics were calculated for each one-month interval between 5 and 18 months of age. Scrotal circumference increased as a logarithmic function of age and was best described by a quadratic regression equation. This information provides the veterinary practitioner with indices for normal scrotal circumference measurements for young Holstein bulls, and an estimate of the scrotal circumference growth curve.     

Influence of toxic endophyte-infected fescue on sperm characteristics and endocrine factors of yearling Brahman-influenced bulls

Sixteen (mean age = 1.1 +/- 0.1 yr; mean BW = 478 +/- 34 kg) Brahman-influenced bulls were used to determine the influence of fescue type on sperm characteristics and serum concentrations of prolactin, cortisol, and testosterone. Bulls were blocked by BW, scrotal circumference (SC), and pregrazing sperm characteristics and randomly assigned to graze toxic endophyte-infected (EI; 4 bulls/pasture; 2 pastures) or novel endophyte-infected (NE; 4 bulls/pasture; 2 pastures) tall fescue for 121 d. Semen was collected by electroejaculation, and SC was measured and blood samples collected monthly. Sperm were evaluated for motility and morphology with an integrated visual optical system. Overall mean concentration of prolactin was decreased more (P < 0.01) in EI bulls than NE bulls from May to August. Scrotal circumference was not affected by fescue type (P = 0.58); overall SC averaged 36.7 +/- 2.3 cm. Percentage of live sperm was not different (P = 0.24) between NE bulls (80%) than EI bulls (67%) in July and August. Bulls grazing NE fescue had more (P < 0.06) motile sperm than EI bulls in July and August. Percentages of progressive (57 vs. 38%, NE and EI, respectively; P < 0.06) and rapid (67 vs. 46%, NE and EI, respectively; P = 0.04) sperm were greater from bulls grazing NE than EI bulls in July and August. Average velocity of the smoothed sperm path and progressive velocity in a straight line from the beginning to the end of the sperm track were slower (P < 0.09) in EI bulls than NE bulls and were slower (P = 0.04) in August compared with July. Mean width of head oscillation as the sperm swims was less (P < 0.06) in August than July. Concentrations of cortisol and testosterone were not (P > 0.10) influenced by fescue type. Semen from bulls grazing EI had reduced motility and morphology than bulls grazing NE. Detrimental effects of toxic fescue may not be mediated by cortisol, testosterone, or both. Semen quality of bulls grazing toxic EI tall fescue was decreased with increased maximum ambient temperatures.     

Breeding soundness examination of North American bison bulls

OBJECTIVE: To evaluate the breeding soundness examination procedure in plains bison bulls. DESIGN: Multiyear (1993 through 1997) cross-sectional clinical procedure evaluation. ANIMALS: Two hundred thirty-four 28- to 30-month-old bison bulls at Custer State Park. PROCEDURE: Breeding soundness examinations were performed on all bison bulls using 1992 Society for Theriogenology guidelines for beef cattle semen evaluation and reproductive tract examination. Linear and logistic regression analyses were used to detect correlations and associations among breeding soundness examination variables. RESULTS: Scrotal circumference (SC) was significantly correlated with body weight, percentage of normal spermatozoa, percentage of primary spermatozoal defects, and percentage of motile spermatozoa. Scrotal circumference was positively associated with increased odds of semen collection, satisfactory motility (> or = 30% motility), satisfactory morphology (> or = 70% normal spermatozoa), and simultaneous satisfactory motility and morphology. Receiver-operator characteristic curve analysis selected 29 cm as the optimal SC cutoff most predictive of simultaneous satisfactory spermatozoal motility and morphology. Only 36.2% (83/229) of the bison bulls had a SC of 29 cm or greater and satisfactory spermatozoal motility and morphology. CLINICAL IMPLICATIONS: SC is a good indicator of adequate spermatozoal motility and structure in bison. We recommend use of 30% spermatozoal motility, 70% normal spermatozoal morphology, and 29-cm SC as minimal satisfactory measurements for breeding soundness examinations of 28- to 30-month-old bison bulls that have been raised on forage-based nutrition.     

Scrotal circumference, seminal characteristics, and testicular lesions of yearling Angus bulls

The effect of age and body weight on scrotal circumference (SC), the effect of SC on percentage of sperm abnormalities and seminal characteristics, and the relationship of SC with testicular weight, epididymidal weight, degree of germinal epithelial loss (DGEL), and percentage of tubules graded 4 or greater (G4+) were studied in 37 Angus bulls. All bulls were from one herd and were examined at monthly intervals, during a 140-day weight gain test starting when they were 11 months old. The study was terminated when the bulls were slaughtered at 14 months of age. As age and body weight increased, SC increased (P less than 0.001). The incidence of sperm abnormalities decreased (P less than 0.001) as SC increased; however, seminal characteristics remained poor in bulls with SC less than or equal to 32 cm. Pathologic changes in 600 cross sections of seminiferous tubules from each bull were classified into 9 grades. The DGEL per 100 tubules was calculated by assigning a value to each grade according to the severity of loss of germinal epithelium. Tubules classified as G4+ were devoid of germinal cells and provided an index of irreversible loss of germinal epithelium. The SC was correlated positively with testicular weight (r = 0.91, P less than 0.001) and epididymal weight (r = 0.59, P less than 0.001) and negatively with DGEL (r = -0.48, P less than 0.01) and G4+ (r = -0.44, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Age adjustment factors, heritabilities and genetic correlations for scrotal circumference and related growth traits in Hereford and Brangus bulls

Field data records on 10,511 Hereford and 2,522 Brangus bulls between 330 and 430 d of age were analyzed to find age of calf and age of dam adjustment factors for yearling scrotal circumference. Age of calf adjustment factors were .024 cm/d for Hereford bulls and .041 cm/d for Brangus bulls. Sons of Hereford dams were adjusted to a 6- to 8-yr dam age basis by adding .7, .3, .2, .2 or .3 cm for dams 2, 3, 4, 5 or 8 or more years old, respectively. Age of dam adjustment factors for Brangus bulls were .8, .4, .3 and .2 for dams 2, 3, 4 or 8 or more years old, respectively. Variance and covariance components for yearling scrotal circumference and several growth traits were estimated within breed using multiple-trait models and pseudo expectations involving the solutions and the right-hand sides of the mixed-model equations. Additive heritability estimates for yearling scrotal circumference of .53 and .16 were found for Hereford and Brangus bulls, respectively. Maternal heritability estimates of .12 and .10 were found for Hereford and Brangus bulls, respectively. Genetic correlations between yearling scrotal circumference and other growth traits were positive for both sets of data indicating that selection for yearling scrotal circumference should not adversely affect other growth traits in either breed. Environmental correlation estimates between yearling scrotal circumference and adjusted birth weight and between yearling scrotal circumference and adjusted 205-d weight and adjusted 365-d height were positive and moderate in magnitude for both breeds.     

Relationships Among Growth Characteristics of Replacement Angus Heifers

Angus heifers (n = 88) were used over 3 yr to determine the relationship between two sets of traits considered to be indicators of growth. Data were collected at weaning (7 to 8 mo), yearling (10 to 11 mo), andprebreeding (13 to 14 mo) and included BW, hip height (HH), hip width (HW), pelvic height (PH), pelvic width (PW), lactate dehydrogenase (LDH) activity, longissimus area (LA), and backfat thickness (BKFAT). Measurements were grouped into two sets of traits; Set 1 included BW, HH, HW, and LDH activity; Set 2 included PH, PW, LA, and BKFAT. Weight was correlated (P < 0.01) with all variables studied except LDH activity. At weaning, heifers with lower LDH activity had a larger PH just prior to the breeding season. The first canonical variate between Set 1 measurements at weaning or yearling was correlated (r > 0.8; P < 0.01) with Set 2 measurements at prebreeding. Additional linear combinations of Set 1 traits at weaning and yearling were correlated (r > 0.48; P < 0.01) with Set 2 traits at prebreeding. These results suggest that the Set 1 measurements, as early as at weaning, could be used as indicators of Set 2 variables at prebreeding. The canonical coefficients of Set 1 traits were used to rank heifers as either above or below the mean. Ranking heifers based on Set 1 measurements at weaning resulted in a greater (P < 0.01) percentage of heifers calving as 2-yr olds. Correlations between Set 1 and Set 2 traits suggest that external measurements coupled with LDH activity could be used in identifying replacement beef heifers that have larger pelvic dimensions at breeding and a greater frequency of calving as 2-yr olds.     

Estimation of genetic parameters and effects of cytoplasmic line on scrotal circumference and semen quality traits in Angus bulls

The purpose of this study was to estimate the heritability of scrotal circumference (SC) and semen traits, genetic correlations between SC and semen quality traits, and the effect of cytoplasmic line on SC and semen traits. Breeding soundness exam (BSE) data were collected on registered Angus bulls at 4 ranches over 7 yr. The American Angus Association provided historical pedigree information to estimate the effect of cytoplasmic line on SC and semen quality traits. After editing, the evaluated data set contained 1,281 bulls with breeding soundness exam data that traced back to 100 founder dams. Data were analyzed using a 2-trait animal model to obtain heritability, genetic correlation between SC and semen quality traits, as well as the effect of cytoplasmic line as a random effect for SC, percent motility (MOT), percent primary abnormalities (PRIM), percent secondary abnormalities (SEC), and percent total abnormalities (TOT) using multiple-trait derivative-free REML. Fixed effects included source ranch and collection year, and test age was used as a covariate. Estimates of heritability for SC, MOT, PRIM, SEC, and TOT were 0.46, 0.05, 0.27, 0.23, and 0.25, respectively. Genetic correlations between SC and MOT, PRIM, SEC, and TOT were 0.36, -0.19, -0.11, and -0.23, respectively. The proportions of phenotypic variance accounted for by cytoplasmic line for SC, MOT, PRIM, SEC, and TOT were <0.001, 0.013, 0.023, 0.002, and <0.001, respectively. Genetic correlations between SC and semen quality traits were low to moderate and favorable. Cytoplasmic line may have a marginal effect on MOT and PRIM, but is likely not a significant source of variation for SC, SEC, or TOT.     

Scrotal circumference adjustment factors for age and weight differences in beef bulls

Scrotal circumference measurements were analyzed to develop appropriate adjustment factors for age and body weight differences in beef bulls. Age, body weight, and scrotal circumference measurements were collected on 863 Angus, 753 Polled Hereford, and 302 Simmental bulls from the Missouri tested bull sale, 1169 Polled Hereford bulls from the American Polled Hereford Association, and 465 Polled Hereford and 264 Simmental bulls from Nichols Farms in Bridgewater, Iowa. Within sources, data were subdivided into appropriate subsets and then each subset was statistically analyzed. Adjustment factors to remove differences in scrotal circumference due to age and body weight were developed for bulls of each of the 3 breeds studied.     

Effects of Artificial Insemination vs Natural Service Breeding on Production and Reproduction Parameters in Dairy Herds

The effects of four combinations of AI and natural service (NS) breeding on production and reproduction parameters were analyzed using Holstein Dairy Herd Improvement herd summary records for years 1999 through 2002. Herds were assigned to breeding systems (BS) by percentage of NS usage as follows: 1) 0%, 2) 1 to 20%, 3) 21 to 89%, and 4) 90 to 100%. Regions were North, Midsouth, and South. Herd sizes were small (<100 cows), medium (100 to 249 cows), and large (>250 cows). The mean percentages of AI and NS usage over 4 yr by BS were 1) 100%, 0%; 2) 92.9%, 7.1%; 3) 54.2%, 45.8%; and 4) 1.0%, 99.0%. Actual calving interval was shorter (P<0.05) for BS4 compared with the other systems. Herds using a combination of AI and NS (BS2 and BS3) had longer actual calving intervals than did herds in BS1 (P<0.05). Days dry and the percentage of dry periods between 40 to70 d were less for BS1 (P<0.05). The percentage of cows leaving the herd was significantly less for BS4. The percentage of cows leaving the herd for reproductive reasons was greater for BS1 (P<0.05). Overall reproductive efficiency as measured by the percentage of cows in milk and herd milk yield was greater (P<0.05) for BS1 and declined as the percentage of NS increased. Actual calving interval, days dry, and percentage of dry periods between 40 to 70 d were less in the North (P<0.05). Percentage of cows in milk and herd milk yield were greater in the North (P<0.05). Herd milk yield was greater (P<0.05) for large-size herds and decreased with declining herd size.     

Evaluation of American Wagyu sires for scrotal circumference by age and body weight

Thirty-six percent of American Wagyu bulls do not meet the current minimum standards set by the Society of Theriogenology for the breeding soundness exam. In contrast, only 15% of bulls of domestic breeds do not meet the minimum standards. Scrotal circumference measurements of Wagyu are smaller than those of other breeds. The objective of this research was to describe scrotal circumference of Wagyu bulls as it relates to age and BW. The data set consisted of 190 Wagyu bulls housed at two locations. One hundred forty-one bulls constituted the first set of data (location 1); scrotal circumference was measured one to six times per bull aged between 13 and 70 mo. Ninety-four of the bulls underwent semen evaluation for motility and morphology. Forty-nine bulls constituted the data set for which scrotal circumference and BW was measured one to nine times per bull between 5 and 21 mo of age (location 2). Mean scrotal circumference of bulls within each age group was as follows: 12 to 14 mo, 29.8 0.2 cm (mean +/- SE); 15 to 17 mo, 31.8 +/- 0.2 cm; 18 to 20 mo, 32.9 +/- 0.3 cm; 21 to 24 mo, 31.8 +/- 0.5 cm; and > 24 mo, 35.5 +/- 0.2 cm. Both age and BW were highly correlated to scrotal circumference (r = 0.81 and 0.82, respectively). Within each age group, there were a percentage of bulls that did not meet the minimum standard for scrotal circumference set by the Society of Theriogenology. The percentages were as follows: 12 to 14 mo, 46%; 15 to 17 mo, 25%; 18 to 20 mo, 33%; 21 to 24 mo, 42%; and > 24 mo, 32%. Morphology and motility were > 50% each in 91% of the bulls between ages 12 and 20 mo at location 1. Based on these data, it is recommended that Wagyu bulls be evaluated with the breed-specific minimum standards for scrotal circumference of 26 cm from 12 to 14 mo, 29 cm from 15 to 17 mo, and 30 cm from 18 to 20 mo of age.     

种公牛阴囊周径与其体重、体高间的相关性研究

测定了山东银香伟业集团中大种公牛站1998～2003年引进的西门塔尔(XM)、盖普威(德国黄牛GL)、利木赞(LM)、荷斯坦(HS)四个品种62头种公牛阴囊周径(SC)、体高,体重,并对SC与体重、体高、年龄进行相关性分析.结果表明:西门塔尔、盖普威(德国黄牛)、利木赞、荷斯坦这四个品种的SC与体重、体高呈正相关,并且同品种不同年龄阶段SC与体重、体高呈高度正相关,同品种不同年龄阶段以及不同品种的同一年龄阶段,SC表现为差异显著(P＜0.05).为引进牛品种的选育工作提供依据.     

Genetic associations between accumulated productivity, and reproductive and growth traits in Nelore cattle

The total meat yield in a beef cattle production cycle is economically very important and depends on the number of calves born per year or birth season, being directly related to reproductive potential. Accumulated Productivity (ACP) is an index that expresses a cow's capacity to give birth regularly at a young age and to wean animals of greater body weight. Using data from cattle participating in the “Program for Genetic Improvement of the Nelore Breed” (PMGRN — Nelore Brasil), bi-trait analyses were performed using the Restricted Maximum Likelihood method based on an ACP animal model and the following traits: age at first calving (AFC), female body weight adjusted for 365 (BW365) and 450 (BW450) days of age, and male scrotal circumference adjusted for 365 (SC365), 450 (SC450), 550 (SC550) and 730 (SC730) days of age. Median estimated ACP heritability was 0.19 and the genetic correlations with AFC, BW365, BW450, SC365, SC450, SC550 and SC730 were 0.33, 0.70, 0.65, 0.08, 0.07, 0.12 and 0.16, respectively. ACP increased and AFC decreased over time, revealing that the selection criteria genetically improved these traits. Selection based on ACP appears to favor the heaviest females at 365 and 450 days of age who showed better reproductive performance as regards AFC. Scrotal circumference was not genetically associated with ACP.     

Effects of Calcium Salts of Long-Chain Fatty Acids on Growth,Reproductive Performance,and Hormonal and Metabolite Concentrations in Pubertal Beef Heifers and Postpartum Cows

Pubertal Angus heifers and postpartum Angus cows were used to study the effects of supplemental calcium salts of long-chain fatty acids (CLCFA) added to forage-based diets on growth, reproductive performance, and hormonal and metabolite concentrations. In Experiment 1, heifers were fed corn (control; n = 20) or corn plus Megalac® (CLCFA; n = 20). Supplements were isoenergetic and fed for 123 d prior to breeding. Blood samples, BW, and hip heights were obtained on d 0, 32, 60, 88, 123, and 260. Growth, serum leptin, early pregnancy progesterone concentrations, and reproductive performance, except for calving rate, were not different. Calving rate for heifers fed ClCFA tended to be greater (P=0.12) than that of heifers fed a control diet. Serum cholesterol increased (P<0.01) over time only in heifers fed ClCFA; however, ClCFA increased (P<0.01) concentrations of serum triglycerides only on d 32 and 123. Experiment 2 was conducted to determine the effects of ClCFA on reproductive performance of postpartum cows receiving chelated (CHEL; n = 36) or inorganic (INORG; n = 38) mineral supplements. Beginning 28 d prior to estrus synchronization, cows within each mineral group were fed the control diet or the diet containing corn plus CLCFA, as in Experiment 1, for 54 d. Blood samples and BW were obtained on d 0, 28, and 56. Weight loss was greater (P<0.01) in cows receiving INORG supplements than in cows receiving CHEL supplements; however, CLCFA reduced (P<0.01) the amount of BW lost in cows receiving INORG supplements but not in cows receiving CHEL supplements. Overall, concentrations of serum cholesterol and triglyceride and reproductive performance, excluding calving interval, were not significantly affected by CLCFA. Calving interval tended to be longer (P=0.06) in cows fed CLCFA.