Biomedical subjects

C C Chase

Publications and source records attributed to C C Chase.

At least 19 recordsLinked to original sources

PubMed2007

Genetic parameters for body weight, hip height, and the ratio of weight to hip height from random regression analyses of Brahman feedlot cattle.

The objective of this research was to assess the genetic control of BW, hip height, and the ratio of BW to hip height (n = 5,055) in Brahman cattle through 170 d on feed using covariance function-random regression models. A progeny test of Brahman sires (n = 27) generated records of Brahman steers and heifers (n = 724) over 7 yr. Each year after weaning, calves were assigned to feedlot pens, where they were fed a high-concentrate grain diet. Body weights and hip heights were recorded every 28 d until cattle reached a targeted fatness level. All calves had records through 170 d on feed; subsequent records were excluded. Models included contemporary group (sex-pen-year combinations, n = 63) and age at the beginning of the feeding period as a covariate. The residual error structure was modeled as a random effect, with 2 levels corresponding to two 85-d periods on feed. Information criterion values indicated that linear, random regression coefficients on Legendre polynomials of days on feed were most appropriate to model additive genetic effects for all 3 traits. Cubic (hip height and BW:hip height ratio) or quartic (BW) polynomials best modeled permanent environmental effects. Estimates of heritability across the 170-d feeding period ranged from 0.31 to 0.53 for BW, from 0.37 to 0.53 for hip height, and from 0.23 to 0.6 for BW:hip height ratio. Estimates of the permanent environmental proportion of phenotypic variance ranged from 0.44 to 0.58 for BW, 0.07 to 0.26 for hip height, and 0.30 to 0.48 for BW:hip height ratio. Within-trait estimates of genetic correlation on pairs of days on feed (at 28-d intervals) indicated lower associations of BW:hip height ratio EBV early and late in the feeding period but large positive associations for BW or hip height EBV throughout. Estimates of genetic correlations among the 3 traits indicated almost no association of BW:hip height ratio and hip height EBV. The ratio of BW to hip height in cattle has previously been used as an objective measure of BCS in cows or calves; it may offer a unique assessment of body dimension. Results indicated that there is substantial additive genetic variation for this trait, and it may be possible to use EBV to increase BW without increasing frame score in Brahman cattle.

Aging↗

PubMed2006

Effects of calpastatin and micro-calpain markers in beef cattle on tenderness traits.

The objective of this study was to assess the association of single nucleotide polymorphisms (SNP) developed at the calpastatin (CAST) and mu-calpain (CAPN1) genes with meat tenderness and palatability traits in populations with diverse genetic backgrounds. Three populations were used in the study. One population consisted of Bos taurus that included crossbred animals derived from Hereford, Angus, Red Angus, Limousin, Charolais, Gelbvieh, and Simmental (GPE7; n = 539). Another population consisted of Bos taurus with Bos indicus influence, including crossbred animals from Hereford, Angus, Brangus, Beefmaster, Bonsmara, and Romosinuano (GPE8; n = 580). The third population was Bos indicus and consisted of purebred Brahman (STARS; n = 444). Traits evaluated were meat tenderness measured as Warner-Bratzler shear force (WBSF; kg) at 14 d postmortem, and traits evaluated by trained sensory panels that included tenderness score, juiciness, and flavor intensity. A SNP at the CAST gene had a significant (P < 0.003) effect on WBSF and tenderness score in the GPE7 and GPE8 populations. Animals inheriting the TT genotype at CAST had meat that was more tender than those inheriting the CC genotype. The marker at the CAPN1 gene was significant (P < 0.03) for tenderness score in GPE7 and GPE8. Animals inheriting the CC genotype at CAPN1 had meat that was more tender than those inheriting the TT genotype. Markers at the CAST and CAPN1 genes were associated with flavor intensity in the GPE8 population. Animals inheriting the CC genotype at CAST and the TT genotype at CAPN1 produced steaks with an intense flavor when compared with the other genotypes. An interaction between CAST and CAPN1 was detected (P < 0.05) for WBSF on GPE8. The statistical significance of the interaction is questionable because of the limited number of observations in some cells. Markers developed at the CAST and CAPN1 genes are suitable for use in identifying animals with the genetic potential to produce meat that is more tender.

Animals↗

PubMed2005

Assessment of single nucleotide polymorphisms in genes residing on chromosomes 14 and 29 for association with carcass composition traits in Bos indicus cattle.

Objective of this study was to assess the association of SNP in the diacylglycerol O-acyltransferase 1 (DGAT1), thyroglobulin (TG), and micromolar calcium-activated neutral protease (CAPN1) genes with carcass composition and meat quality traits in Bos indicus cattle. A population of Brahman calves (n = 479) was developed in central Florida from 1996 to 2000. Traits analyzed were ADG, hip height, slaughter weight, fat thickness, HCW, marbling score, LM area, estimated KPH fat, yield grade, retail yield, sensory panel tenderness score, carcass hump height, and cooked meat tenderness measured as Warner-Bratzler shear force at 7, 14, and 21 d postmortem. Single nucleotide polymorphisms previously reported in the TG and DGAT1 genes were used as markers on chromosome 14. Two previously reported and two new SNP in the CAPN1 gene were used as markers on chromosome 29. One SNP in CAPN1 was uninformative, and another one was associated with tenderness score (P < 0.05), suggesting the presence of variation affecting meat tenderness. All three informative SNP at the CAPN1 gene were associated with hump height (P < 0.02). The TG marker was associated with fat thickness and LMA (P < 0.05), but not with marbling score. No significant associations of the SNP in the DGAT1 gene were observed for any trait. Allele frequencies of the SNP in TG and CAPN1 were different in this Brahman population than in reported allele frequencies in Bos taurus populations. The results suggest that the use of molecular marker information developed in Bos taurus populations to Bos indicus populations may require development of appropriate additional markers.

Animals↗

PubMed2005

A new single nucleotide polymorphism in CAPN1 extends the current tenderness marker test to include cattle of Bos indicus, Bos taurus, and crossbred descent.

The three objectives of this study were to 1) test for the existence of beef tenderness markers in the CAPN1 gene segregating in Brahman cattle; 2) test existing CAPN1 tenderness markers in indicus-influenced crossbred cattle; and 3) produce a revised marker system for use in cattle of all subspecies backgrounds. Previously, two SNP in the CAPN1 gene have been described that could be used to guide selection in Bos taurus cattle (designated Markers 316 and 530), but neither marker segregates at high frequency in Brahman cattle. In this study, we examined three additional SNP in CAPN1 to determine whether variation in this gene could be associated with tenderness in a large, multisire American Brahman population. One marker (termed 4751) was associated with shear force on postmortem d 7 (P < 0.01), 14 (P = 0.015), and 21 (P < 0.001) in this population, demonstrating that genetic variation important for tenderness segregates in Bos indicus cattle at or near CAPN1. Marker 4751 also was associated with shear force (P < 0.01) in the same large, multisire population of cattle of strictly Bos taurus descent that was used to develop the previously reported SNP (referred to as the Germplasm Evaluation [GPE] Cycle 7 population), indicating the possibility that one marker could have wide applicability in cattle of all subspecies backgrounds. To test this hypothesis, Marker 4751 was tested in a third large, multisire cattle population of crossbred subspecies descent (including sire breeds of Brangus, Beefmaster, Bonsmara, Romosinuano, Hereford, and Angus referred to as the GPE Cycle 8 population). The highly significant association of Marker 4751 with shear force in this population (P < 0.001) confirms the usefulness of Marker 4751 in cattle of all subspecies backgrounds, including Bos taurus, Bos indicus, and crossbred descent. This wide applicability adds substantial value over previously released Markers 316 and 530. However, Marker 316, which had previously been shown to be associated with tenderness in the GPE Cycle 7 population, also was highly associated with shear force in the GPE Cycle 8 animals (P < 0.001). Thus, Marker 316 may continue to be useful in a variety of populations with a high percentage of Bos taurus backgrounds. An optimal marker strategy for CAPN1 in many cases will be to use both Markers 316 and 4751.

Animals↗

PubMed2004

Social and breed effects on the expression of a PGF2alpha induced oestrus in beef cows.

Social organization and breed effects following PGF2alpha were studied in mature Angus, Brahman and Senepol cows allocated into two groups (each A = 5, B = 5 and S = 5). Variables including interval to oestrus onset (IEO), oestrous duration (DE), total mounts received (TMR), and oestrous intensity (IE) were derived via HeatWatch. Breed-type influenced IEO (B = 42.6 +/- 6.7 h; S = 54.6 +/- 6.0 h; and A = 27.8 +/- 5.8 h; p < 0.003). Within breeds, dominant B (69.4 +/- 13.3 h) and S (65.5 +/- 7.4 h) cows were slower (p < 0.05) to be detected in oestrus than subordinate (38.1 +/- 4.4 h) and intermediate (40.6 +/- 6.0 h). However, within A, dominant cows (16.4 +/- 12.5 h) were detected in oestrus earlier (p < 0.05) than intermediate (44.3 +/- 9.2 h) and subordinates (32.7 +/- 5.1 h). Angus (21.5 +/- 2.4 h) and B (22.1 +/- 3.0 h) cows had longer (p < 0.01) DE than S (9.1 +/- 2.8 h). Dominants (20.4 +/- 3.0) and intermediates (20.2 +/- 2.3 h) cows had longer DE (p < 0.04) than subordinates (12.1 +/- 2.1 h) although the interaction breed x social order showed that dominant S had shorter DE than dominant A and B (10.1 +/- 3.3; 34.8 +/- 6.0 h; and 20.0 +/- 6.4 h, respectively; p < 0.001). Angus cows had less TMR than B (p < 0.02) and tended to be less than S cows (p < 0.06). Overall, greatest (p < 0.008) IE occurred in the first 9 h after onset of oestrus with no breed effect (p > 0.05). Dominant cows tended (p < 0.10) to have less TMR (3.2 +/- 0.7 mounts) than subordinate (4.1 +/- 0.4 mounts) and intermediate (4.7 +/- 0.6 mounts) throughout, especially 3-6 h after oestrus onset (p < 0.07). Breed and social order both influence PGF2alpha-induced oestrus behaviour.

Animals↗

PubMed2004

Genetic and nongenetic influences on vigor at birth and preweaning mortality of purebred and high percentage Brahman calves.

The objectives of this study were to assess the risk associated with proportion Brahman inheritance, cow age, dystocia, and birth date weather conditions on calf vigor at birth (n = 3,253) and preweaning mortality (n = 3,631), and to estimate heritabilities for these traits. Calves that had poor vigor at birth and calves that died before weaning were coded 1, and those that had adequate birth vigor or survived to weaning were coded 0. Traits were analyzed using GLM. Year (1951 to 2002), cow age, calfgender, minimum temperature on date of birth (two levels: < 5.6 degrees C; or > 5.6 degrees C), and occurrence of dystocia were main effects in models. The proportion of Brahman inheritance in calves was modeled as a covariate. Males had greater odds of poor birth vigor (odds ratio = 1.44, 95% confidence interval = 1.14 to 1.82). The odds of death before weaning for steers relative to heifers approached significance (P = 0.07; odds ratio 1.41, 95% confidence interval 0.97 to 2.04). Calves born to young (3-yr-old) or very old (13 yr or older) cows had greater (P < 0.05) odds of poor vigor and death before weaning than calves of 5-yr-old cows. Calves with difficult births had 2.59 times greater odds of poor birth vigor (95% confidence interval 1.40 to 4.79) and 12.9 times greater odds of death before weaning (95% confidence interval 8.14 to 20.39) than calves born with no dystocia. Calves born on days with minimum temperatures of 5.6 degrees C or less had greater odds of poor vigor (odds ratio 1.97, 95% confidence interval 1.50 to 2.59) and of death before weaning (odds ratio 1.64, 95% confidence interval 1.27 to 2.13) than did calves born on days with higher minimums. The occurrence of rainfall on date of birth did not influence calf vigor at birth or preweaning mortality (P > 0.85). Purebred Brahman calves had 24.7 times greater odds (95% confidence interval 8.23 to 73.97) of poor vigor than 2/3 Brahman calves. The regression coefficient estimate for fraction of Brahman inheritance approached significance (P = 0.07) for preweaning mortality. Estimates of direct and maternal heritability were 0.09 +/- 0.05 and 0.10 +/- 0.04 for birth vigor, and 0.06 +/- 0.05 and 0.09 +/- 0.04, respectively, for preweaning mortality. Some exploitable genetic variation exists for these traits, but management of other factors may yield more immediate improvement than selection.

Age Factors↗

PubMed2004

Maternal and reproductive performance of Brahman x Angus, Senepol x Angus, and Tuli x Angus cows in the subtropics.

To determine the maternal and reproductive performance of F1 cows in the subtropics, 42 Brahman x Angus, 34 Senepol x Angus, and 50 Tuli x Angus cows were bred to Angus bulls to calve first and subsequently bred to Charolais bulls to calve as 3- to 8-yr-olds. Age at first calving did not differ among crossbred cows. Angus-sired calf birth weights were heavier (P < 0.01) from Senepol x Angus than either Brahman x Angus or Tuli x Angus cows. Weaning weights of Angus-sired calves were heavier (P < 0.01) from Brahman x Angus (213.5 kg) than either Senepol x Angus (194.9 kg) or Tuli x Angus (191.5 kg) cows. As 3- to 8-yr-old cows, calf birth weights were heavier (P < 0.05) from Senepol x Angus compared with Brahman x Angus but not Tuli x Angus cows. Weaning weights of Charolais-sired calves were heaviest (P < 0.05) from Brahman x Angus cows (268.9 kg), lightest from Tuli x Angus cows (233.4 kg), and intermediate from Senepol x Angus cows (245.0 kg). Calf crop born and calf crop weaned were lowest (P < 0.05) for Senepol x Angus cows (76.9 and 70.2%) and did not differ between Brahman x Angus (89.0 and 86.1%) and Tuli x Angus (94.7 and 86.5%) cows. Tuli x Angus cows tended (P < 0.10) to have a lower percentage of unassisted births and lower (P < 0.10) calf survival to weaning than Brahman x Angus cows but not Senepol x Angus cows. As 3- to 8-yr-olds, weaning weight per cow exposed was greatest (P < 0.05) for Brahman x Angus (234.2 kg), least (P < 0.05) for Senepol x Angus (173.0 kg), and intermediate (P < 0.05) for Tuli x Angus (209.1 kg) cows. Also as 3- to 8-yr-olds, efficiency (205-d calf weight per 100 kg of cow exposed) was similar for Brahman x Angus (42.2) and Tuli x Angus cows (40.7), and both were greater (P < 0.01) than for Senepol x Angus cows (33.8). These data indicate that, in the subtropics, maternal and reproductive performance of Tuli x Angus cows, but not Senepol x Angus cows, was comparable to Brahman x Angus cows, except for lower calf survivability and weaning weight.

Animals↗

PubMed2004

Differences in heat tolerance between preimplantation embryos from Brahman, Romosinuano, and Angus breeds.

Exposure to 41 degrees C reduces development of embryos of heat-sensitive breeds (Holstein and Angus) more than for embryos of the heat-tolerant Brahman breed. Here it was tested whether embryonic resistance to heat shock occurs for a thermotolerant breed of different genetic origin than the Brahman. In particular, the thermal sensitivity of in vitro produced embryos of the Romosinuano, a Bos taurus, Criollo-derived breed, was compared to that for in vitro produced Brahman and Angus embryos. At d 4 after insemination, embryos > or = 8 cells were randomly assigned to control (38.5 degrees C) or heat shock (41 degrees C for 6 h) treatments. Heat shock reduced the proportion of embryos that developed to the blastocyst stage on d 8 after insemination. At 38.5 degrees C, there were no significant differences in development between breeds. Among embryos exposed to 41 degrees C, however, development was lower for Angus embryos than for Brahman and Romosinuano embryos. Furthermore, an Angus vs. (Brahman + Romosinuano) x temperature interaction occurred because heat shock reduced development more in Angus (30.3 +/- 4.6% at 38.5 degrees C vs. 4.9 +/- 4.6% at 41 degrees C) than in Brahman (25.1 +/- 4.6% vs. 13.6 +/- 4.6%) and Romosinuano (28.3 +/- 4.1% vs. 17.5 +/- 4.1%). Results demonstrate that embryos from Brahman and Romosinuano breeds are more resistant to elevated temperature than embryos from Angus. Thus, the process of adaptation of Brahman and Romosinuano breeds to hot environments resulted in both cases in selection of genes controlling thermotolerance at the cellular level.

Animals↗

PubMed2003

Differences between Brahman and Holstein cows in response to estrus synchronization, superovulation and resistance of embryos to heat shock.

Embryos from Bos indicus are more resistant to elevated culture temperature (i.e. heat shock) than embryos from some Bos taurus breeds. The present experiment was designed to determine if Brahman embryos have greater resistance to heat shock than Holstein embryos at a stage in development before the embryonic genome was fully activated. A second objective was to test breed effects on estrus synchronization and superovulation responses. A total of 29 Brahman and 24 Holstein cows were subjected to estrus synchronization using gonadotropin releasing hormone (GnRH) and prostaglandin F2alpha (PGF2alpha) superovulation. Embryos were collected at 48 h and day 5 after insemination. There was a tendency for a lower proportion of Brahmans to be detected in standing estrus than Holsteins. There were no differences between breeds in the proportion of cows detected in estrus using both tailpaint and standing estrus as criteria or in interval from PGF2alpha to estrus. The degree of synchrony in estrus was greater for Brahmans. Superovulation response was generally similar between breeds. At 48 h after insemination, there was a tendency for a greater proportion of Brahman oocytes to have undergone cleavage. Uncleaved oocytes were cultured for an additional 24 h-at this time, cleavage rate was similar between breeds. When embryos reached the 2-4-cell stage, they were heat-shocked for 4.5 h at 41 degrees C. This heat shock reduced the proportion of embryos that developed to the blastocyst stage but there was no breedxtreatment interaction. At day 5 after insemination, the number of embryos recovered was too low to allow comparison of breed effects. In conclusion, genetic effects on cellular thermotolerance that make Brahman embryos more resistant to heat shock are not expressed at the 2-4-cell stage. There were few differences between Brahman and Holstein in response to estrus synchronization and superovulation. The fact that cleavage tended to occur earlier in Brahman than Holstein embryos suggests breed differences in timing of ovulation, fertilization or events leading to cleavage.

Animals↗

PubMed2003

Genetic divergence in cellular resistance to heat shock in cattle: differences between breeds developed in temperate versus hot climates in responses of preimplantation embryos, reproductive tract tissues and lymphocytes to increased culture temperatures.

The detrimental effects of heat stress on fertility in cattle are less pronounced in heat-tolerant breeds. Although these genetic differences reflect differences in thermoregulation, cells from heat-tolerant breeds are less adversely compromised by increased temperature (that is, heat shock) than cells from heat-sensitive breeds. Experiments were performed to test the hypothesis that cells and tissues from two thermotolerant breeds (Brahman and Senepol) are better able to survive and function after exposure to increased temperature than cells and tissues from two thermosensitive breeds (Holstein and Angus). Exposure of embryos at>eight-cell stage at day 5 after insemination to heat shock of 41.0 degrees C for 6 h decreased development to the blastocyst stage and the number of cells per embryo. However, the deleterious effect of heat shock on blastocyst formation and the number of cells per embryo was less pronounced for Brahman than for Holstein and Angus breeds. Embryos from Senepol cows had very low development and it was not possible to determine heat shock effects in this breed. In contrast to the sensitivity of embryos to heat shock, there was no effect of a 41.0 degrees C heat shock on [(3)H]leucine incorporation into proteins secreted by oviductal or endometrial explants. Lymphocytes from Brahman and Senepol cows were more resistant to heat-induced apoptosis than lymphocytes from other breeds. Heat shock reduced lymphocyte glutathione content but the magnitude of the decrease was not affected by breed. In conclusion, embryos from Brahman cows are more resistant to heat shock than embryos from Holstein or Angus cows. Genetic differences are also present in thermotolerance for apoptosis response in lymphocytes, with Brahman and Senepol cattle being more resistant to heat shock than Angus and Holstein breeds. It is likely that the evolutionary forces that led to the Brahman and Senepol breeds being adapted to hot climates resulted in the selection of genes controlling resistance to cellular heat shock.

Analysis of Variance↗

PubMed2003

Effect of sire on mu- and m-calpain activity and rate of tenderization as indicated by myofibril fragmentation indices of steaks from Brahman cattle.

The objectives of this study were to assess the influence of sire on mu- and m-calpain activities, to evaluate the relationships of activities of these enzymes to other traits related to beef palatability, and to assess the influence of sire on the rate of tenderization (as measured by myofibril fragmentation index [MFI]) in Brahman longissimus muscle. Brahman calves (n = 87), sired by nine bulls, were born, weaned, fed, and slaughtered in central Florida. Traits evaluated were mu- and m-calpain activities and MFI after 1, 7, 14, and 21 d of aging. Other traits were analyzed to determine their associations with mu- and m-calpain activity and MFI, including calpastatin activity, percentage of raw and cooked lipids, Warner-Bratzler shear force (WBSF) values after 7, 14, and 21 d of aging, and sensory panel rating of tenderness, juiciness, and connective tissue amount after 14 d of aging. Data were analyzed using a model with sire, sex, year, and slaughter group (calves of the same sex slaughtered on the same date) as fixed effects, and adjusted to a constant adjusted 12th-rib fat thickness. Sire affected mu-calpain activity (P < 0.04), calpastatin activity (P < 0.01), d-14 MFI (P < 0.02), d-7 WBSF (P < 0.05), d-14 WBSF (P < 0.04), and sensory panel juiciness score (P < 0.01), but not (P < 0.75) m-calpain activity. Measures of tenderness and palatability were generally moderately to strongly correlated (both simple and residual correlations) with calpastatin and m-calpain activity. Myofibril fragmentation index residuals (adjusted for all model components except sire) after all aging periods were fitted using nonlinear regression to the exponential curve (MFI(i) = kappa0 + kappa1 exp[kappa2 t(i)] + epsilon(i), where t(i) represents aging in days, k0 is ultimate MFI after aging, kappa1 is the difference between initial and ultimate MFI, kappa2 is the rate of increase in MFI, and epsilon(i) is the error term associated with the ith observation, assumed to be independent and identically distributed normally). Sires had different estimates and combinations of estimates, which were used to plot MFI change with time. These curves visually differed for sires and suggested that postmortem tenderization extent and rate differ as well. Use of a combination of these estimated parameters in a selection/carcass sorting program represents an alternative consideration for tenderization improvement programs.

Animals↗

PubMed2003

Estimated genetic parameters for palatability traits of steaks from Brahman cattle.

Heritabilities and genetic and phenotypic correlations were estimated from carcass and beef palatability data collected from Brahman calves (n = 504) born in central Florida from 1996 to 2000. Traits evaluated included Warner-Bratzler shear force (after 7, 14, and 21 d of aging), panel tenderness score, connective tissue amount, juiciness, flavor intensity, and off flavor (after 14 d of aging), percentages of raw and cooked lipids, and milligrams per gram of muscle calpastatin activity. Parameters were estimated using an animal model and derivative-free restricted maximum likelihood procedures. Estimated heritabilities for d 7, 14, and 21 shear force were 0.14,0.14, and 0.06, respectively, indicating that improvement in these traits by selection would be slow. Estimated heritabilities of sensory panel attributes were 0.11, 0.12, 0.05, 0.04, and 0.01 for tenderness, connective tissue amount, juiciness, flavor intensity, and off flavor, respectively. The estimated heritabilities for percentages of raw and cooked lipids, and calpastatin activity were 0.34, 0.17, and 0.07, respectively. Most of the estimated genetic correlations among palatability traits and for palatability traits with fat thickness, marbling score, and loin muscle area were consistent with other estimates from the literature. Results indicated that improvement in tenderness based on selection for favorable shear force, sensory panel tenderness, or calpastatin activity would be slow; therefore, postslaughter intervention programs should also be considered.

Animals↗

PubMed2003

Evidence of a major gene influencing hair length and heat tolerance in Bos taurus cattle.

Evidence was found that supports the existence of a major gene (designated as the slick hair gene), dominant in mode of inheritance, that is responsible for producing a very short, sleek hair coat. Cattle with slick hair were observed to maintain lower rectal temperatures (RT). The gene is found in Senepol cattle and criollo (Spanish origin) breeds in Central and South America. This gene is also found in a Venezuelan composite breed, the Carora, formed from the Brown Swiss and a Venezuelan criollo breed. Two sets of backcross matings of normal-haired sire breeds to Senepol crossbred dams assumed to be heterozygous for the slick hair gene resulted in ratios of slick to normal-haired progeny that did not significantly differ from 1:1. Data from Carora x Holstein crossbred cows in Venezuela also support the concept of a major gene that is responsible for the slick hair coat of the Carora breed. Cows that were 75% Holstein: 25% Carora in breed composition segregated with a ratio that did not differ from 1:1, as would be expected from a backcross matinginvolving a dominant gene. The effect of the slick hair gene on RT depended on the degree of heat stress and appeared to be affected by age and/or lactation status. The decreased RT observed for slick-haired crossbred calves compared to normal-haired contemporaries ranged from 0.18 to 0.4 degrees C. An even larger decrease in RT (0.61 degrees C; P < 0.01) was observed in lactating Carora x Holstein F1 crossbred cows, even though it did not appear that these cows were under severe heat stress. The improved thermotolerance of crossbred calves due to their slick hair coats did not result in increased weaning weights, possibly because both the slick and normal-haired calves were being nursed by slick-haired dams. There were indications that the slick-haired calves grew faster immediately following weaning and that their growth during the cooler months of the year was not compromised significantly by their reduced quantity of hair. In the Carora x Holstein crossbred cows there was a positive effect of slick hair on milk yield under dry, tropical conditions.

Age Factors↗

PubMed2003

Escherichia coli O157:H7 prevalence in fecal samples of cattle from a southeastern beef cow-calf herd.

The proportion of fecal samples culture-positive for Escherichia coli O157:H7 was determined for samples collected from 296 beef cows on pasture in a single Florida herd in October, November, and December 2001. The overall proportion of samples that cultured positive was 0.03. The proportion of cows that were culture-positive on at least one occasion was 0.091. No effect of pregnancy status or nutritional regimen on the proportion of culture-positive samples for E. coli O157:H7 was detected. We detected a breed effect on the shedding of E. coli O157, with Romosinuano cows having a lower (P < 0.01) proportion of samples culture-positive than Angus or Brahman cows. This difference might have resulted from the presence of confounding variables; however, it also might represent evidence of breed-to-breed genetic variation in E. coli O157 shedding. Further research is warranted to evaluate breed as a possible risk factor for shedding of this important foodborne pathogen. Further substantiated findings could indicate that breed is a cow-calf-level critical control point of E. coli O157:H7.

Animals↗

PubMed2002

Inheritance of resistance of bovine preimplantation embryos to heat shock: relative importance of the maternal versus paternal contribution.

Brahman preimplantation embryos are less affected by exposure to heat shock than Holstein embryos. Two experiments were conducted to test whether the ability of Brahman embryos to resist the deleterious effects of heat shock was a result of the genetic and cellular contributions from the oocyte, spermatozoa, or a combination of both. In the first experiment, Brahman and Holstein oocytes were collected from slaughterhouse ovaries and fertilized with spermatozoa from an Angus bull. A different bull was used for each replicate to eliminate bull effects. On day 4 after fertilization, embryos >or= 9 cells were collected and randomly assigned to control (38.5 degrees C) or heat shock (41 degrees C for 6 hr) treatments. The proportion of embryos developing to the blastocyst (BL) and advanced blastocyst (ABL; expanded and hatched) stages was recorded on day 8. Heat shock reduced the number of embryos produced from Holstein oocytes that developed to BL (P < 0.001, 55.6 +/- 4.2% vs. 29.8 +/- 4.2%) and ABL (P < 0.01, 37.7 +/- 3.6% vs. 12.2 +/- 3.6%) on day 8 as compared to controls. In contrast, heat shock did not reduce development of embryos produced from Brahman oocytes (BL = 42.1 +/- 4.8% vs. 55.6 +/- 4.8% for 38.5 and 41 degrees C, respectively; ABL = 17.6 +/- 4.2% vs. 32.4 +/- 4.2%). In the second experiment, oocytes from Holstein cows were fertilized with semen from bulls of either Brahman or Angus breeds. Heat shock of embryos >or= 9 cells reduced development to BL (P < 0.002) and ABL (P < 0.005) for embryos sired by both Brahman (BL = 54.3 +/- 7.7% vs. 23.4 +/- 7.7%; ABL = 43. +/- 7.4% vs. 7.9 +/- 7.4%, for 38.5 and 41 degrees C, respectively) and Angus bulls (BL = 57.9 +/- 7.7% vs. 31.0 +/- 7.7%; ABL = 33.6 +/- 7.4% vs. 18.4 +/- 7.4%, for 38.5 and 41 degrees C, respectively). There were no breed x temperature interactions. Results suggest that the oocyte plays a more significant role in the resistance of Brahman embryos to the deleterious effects of heat shock than the spermatozoa.

Animals↗

PubMed2002

Relationship between serum insulin-like growth factor-I and genotype during the postpartum interval in beef cows.

The objective of this study was to determine the effect of genotype and week postpartum on serum concentrations of IGF-I, body condition score (BCS), BW, and ovarian function in beef cows. Cows from the following genotypes were utilized in two consecutive years: Angus (A x A; n = 9), Brahman (B x B; n = 10), Charolais (C x C; n = 12), Angus x Brahman (A x B; n = 22), Brahman x Charolais (B x C; n = 19) and Angus x Charolais (A x C; n = 24). Serum concentrations of IGF-I, BCS, and BW were determined between wk 2 and 9 postpartum. Rectal ultrasound was used to determine days postpartum to first medium (6 to 9 mm) and first large (> or = 10 mm) follicle. Averaged across genotype, BCS decreased (P < 0.05) from 5.0 +/- 0.1 on wk 3 to 4.8 +/- 0.1 on wk 6 postpartum, and BW decreased (P < 0.05) between wk 2 and 3 and again between wk 4 and 9 postpartum. Averaged over year and week postpartum, serum IGF-I concentrations were greatest (P < 0.05) in B x B cows (46 +/- 5 ng/mL) compared with all other genotypes; lowest in A x A (12 +/- 4 ng/mL), C x C (13 +/- 4 ng/mL), and A x C cows (18 +/- 3 ng/mL); and intermediate (P < 0.05) in A x B (28 +/- 3 ng/mL) and B x C (26 +/- 3 ng/mL) cows compared with all other genotypes. Serum IGF-I concentrations did not change (P > 0.10) with week postpartum in C x C, A x A, and A x C cows, but increased (P < 0.05) between wk 2 and 7 postpartum in B x C, A x B, and B x B cows. Average interval to first medium (16 +/- 2 d) and first large (35 +/- 2 d) follicle did not differ (P > 0.10) among genotypes. Serum IGF-I concentrations correlated with BCS (r = 0.53 to 0.72, P < 0.001) but not with days to first large follicle (r = -0.19 to -0.22, P > 0.10). Averaged across genotypes, cows that lost BCS postpartum had lower (P < 0.01) serum IGF-I concentrations. Cows that calved with adequate BCS (i.e., > or = 5) had greater (P < 0.01) serum IGF-I concentrations postpartum than cows that calved with inadequate BCS (i.e., < 5) but days to first large and medium follicle did not differ (P > 0.10). In conclusion, concentrations of IGF-I in serum differed among genotypes and were associated with BCS but not days to first large or medium follicle in postpartum beef cows.

Animals↗

PubMed2002

Estimated genetic parameters for carcass traits of Brahman cattle.

Heritabilities and genetic and phenotypic correlations were estimated from feedlot and carcass data collected from Brahman calves (n = 504) in central Florida from 1996 to 2000. Data were analyzed using animal models in MTDFREML. Models included contemporary group (n = 44; groups of calves of the same sex, fed in the same pen, slaughtered on the same day) as a fixed effect and calf age in days at slaughter as a continuous variable. Estimated feedlot trait heritabilities were 0.64, 0.67, 0.47, and 0.26 for ADG, hip height at slaughter, slaughter weight, and shrink. The USDA yield grade estimated heritability was 0.71; heritabilities for component traits of yield grade, including hot carcass weight, adjusted 12th rib backfat thickness, loin muscle area, and percentage kidney, pelvic, and heart fat were 0.55, 0.63, 0.44, and 0.46, respectively. Heritability estimates for dressing percentage, marbling score, USDA quality grade, cutability, retail yield, and carcass hump height were 0.77, 0.44, 0.47, 0.71, 0.5, and 0.54, respectively. Estimated genetic correlations of adjusted 12th rib backfat thickness with ADG, slaughter weight, marbling score, percentage kidney, pelvic, and heart fat, and yield grade (0.49, 0.46, 0.56, 0.63, and 0.93, respectively) were generally larger than most literature estimates. Estimated genetic correlations of marbling score with ADG, percentage shrink, loin muscle area, percentage kidney, pelvic, and heart fat, USDA yield grade, cutability, retail yield, and carcass hump height were 0.28, 0.49, 0.44, 0.27, 0.45, -0.43, 0.27, and 0.43, respectively. Results indicate that sufficient genetic variation exists within the Brahman breed for design and implementation of effective selection programs for important carcass quality and yield traits.

Animals↗

PubMed2001

Adverse impact of heat stress on embryo production: causes and strategies for mitigation.

The production of embryos by superovulation is often reduced in periods of heat stress. The associated reduction in the number of transferable embryos is due to reduced superovulatory response, lower fertilization rate, and reduced embryo quality. There are also reports that success of in vitro fertilization procedures is reduced during warm periods of the year. Heat stress can compromise the reproductive events required for embryo production by decreasing expression of estrus behavior, altering follicular development, compromising oocyte competence, and inhibiting embryonic development. While preventing effects of heat stress can be difficult, several strategies exist to improve embryo production during heat stress. Among these strategies are changing animal housing to reduce the magnitude of heat stress, utilization of cows with increased resistance to heat stress (i.e., cows with lower milk yield or from thermally-adapted breeds), and manipulation of physiological and cellular function to overcome deleterious consequences of heat stress. Effects of heat stress on estrus behavior can be mitigated by use of estrus detection aids or utilization of ovulation synchronization treatments to allow timed embryo transfer. There is some evidence that embryonic survival can be improved by antioxidant administration and that pharmacological treatments can be developed that reduce the degree of hyperthermia experienced by cows exposed to heat stress.

Animals↗