T. A. Olson

Differences in Thermoregulatory Ability Between Slick-Haired and Wild-Type Lactating Holstein Cows in Response to Acute Heat Stress

Animals inheriting the slick hair gene have a short, sleek, and sometimes glossy coat. The objective of the present study was to determine whether slick-haired Holstein cows regulate body temperature more effectively than wild-type Holstein cows when exposed to an acute increase in heat stress. Lactating slick cows (n = 10) and wild-type cows (n = 10) were placed for 10 h in an indoor environment with a solid roof, fans, and evaporative cooling or in an outdoor environment with shade cloth and no fans or evaporative cooling. Cows were exposed to both environments in a single reversal design. Vaginal temperature, respiration rate, surface temperature, and sweating rate were measured at 1200, 1500, 1800, and 2100 h (replicate 1) or 1200 and 1500 h (replicate 2), and blood samples were collected for plasma cortisol concentration. Cows in the outdoor environment had higher vaginal and surface temperatures, respiration rates, and sweating rates than cows in the indoor environment. In both environments, slick-haired cows had lower vaginal temperatures (indoor: 39.0 vs. 39.4 degrees C; outdoor 39.6 vs. 40.2 degrees C; SEM = 0.07) and respiration rate (indoor: 67 vs. 79 breaths/ min; outdoor 97 vs. 107 breaths/min; SEM = 5.5) than wild-type cows and greater sweating rates in unclipped areas of skin (indoor: 57 vs. 43 g x h(-1)/m(2); outdoor 82 vs. 61 g x h(-1)/m(2); SEM = 8). Clipping the hair at the site of sweating measurement eliminated the difference between slick-haired and wild-type cows. Results indicate that slick-haired Holstein cows can regulate body temperature more effectively than wild-type cows during heat stress. One reason slick-haired animals are better able to regulate body temperature is increased sweating rate.

Factors influencing tenderness in steaks from Brahman cattle

The objective of this study was to identify a set of explanatory variables for Warner-Bratzler shear force and myofibril fragmentation indices after 7, 14, and 21d of aging; and sensory tenderness after 14d of aging of steaks from Brahman cattle. Insoluble collagen was negatively associated (P<0.001) with all tenderness traits across aging periods, and regression coefficients ranged from 5.69±0.49 to 9.12±0.29N for Warner-Bratzler shear force. The effect of lean color score (P<0.05) in analyses of unadjusted traits was diminished when data were adjusted for contemporary group (calves of the same sex, fed in one pen, and slaughtered the same day). Insoluble collagen may be of special importance and offer a unique opportunity to improve palatability of steaks from purebred Brahman cattle.

A novel phenotype for Laron dwarfism in miniature Bos indicus cattle suggests that the expression of growth hormone receptor 1A in liver is required for normal growth

Mutations within the growth hormone receptor (GHR) gene that lead to an inactivated or truncated GHR protein cause abnormal growth and small adult size in a variety of species (Laron dwarfism). We studied a line of miniature Bos indicus cattle that have phenotypic (small mature size) and endocrine (increased blood growth hormone and decreased blood insulin-like growth factor-I concentrations) similarities to Laron dwarfs. Liver mRNA from miniature and control cattle was used to amplify a cDNA within the coding region of the GHR. The miniature cattle had GHR mRNA size (determined by Northern blot) and cDNA sequence that were similar to control cattle and, therefore, were unlike most Laron dwarf genotypes in which the GHR gene is mutated. Amounts of mRNA from liver as well as muscle (superficial neck and longissimus) were analyzed by ribonuclease protection assay for IGF-I, total GHR, GHR 1A (inducible, liver-specific GHR mRNA), and GHR 1B (constitutive GHR mRNA). Four control and five miniature bulls were tested. As expected, liver IGF-I mRNA was decreased in the miniature cattle (approximately 12% of control; P < 0.01). The amount of the total GHR as well as GHR 1A mRNA were also decreased in liver (17% and 19% of control, respectively; P < 0.01). Other GHR mRNA, including GHR 1B mRNA, were similar for miniature and control cattle. In muscle, there was a tendency (P < 0.10) for decreased IGF-I mRNA and increased GHR mRNA in miniature compared with control cattle. In summary, a novel phenotype for Laron dwarfism in Bos indicus cattle was associated with underexpression of GHR 1A mRNA, but not other GHR mRNA variants in liver. In addition to decreased GHR 1A mRNA, the miniature cattle had decreased liver IGF-I mRNA. Full expression of GHR 1A in liver, therefore, may be required for full liver IGF-I expression and normal growth.

Evaluation of tropically adapted straightbred and crossbred beef cattle: Heifer age and size at first conception and characteristics of their first calves

The objectives of this work were to estimate genetic effects for age and size at estimated time of first conception, and temperament in straightbred and crossbred heifers (n = 554) produced from Romosinuano, Brahman, and Angus cattle, and to evaluate first-parturition performance of heifers, including calf birth weight, occurrence of calving difficulty, occurrence of poor vigor in their newborn calves, and calf mortality. At approximately 7 mo of age, weaned heifers were pastured with Mashona or Tuli bulls until confirmed pregnant. Body weight, hip height, exit velocity (m/s), and chute temperament score (1 = calm, no movement; 5 = continuous movement, struggling) were recorded at 28-d intervals until heifers averaged 19 mo of age. Age at first conception was estimated as age at calving minus 285 d. Regression analyses were used to estimate BW and hip height at age of first conception. Brahman heifers were older, heavier, and had greater hip height than other straightbred groups (P < 0.05) and most crossbred groups. Brahman and reciprocal Brahman-Angus heifers had greater (P < 0.05) exit velocity than Romosinuano and Angus heifers. Brahman sire and dam breed chute temperament scores were greater (P < 0.05) than those of all other breed groups. Estimates of heterosis for age at first conception were -53.7 ± 9.5 (-11%), -56 ± 10.1 (-11%), and -92.9 ± 11 d (-18%) for Romosinuano-Brahman, Romosinuano-Angus, and Brahman-Angus, respectively (P < 0.01). Heterosis was detected (P < 0.04) for Romosinuano-Brahman for BW (12 ± 4.3 kg, 3.7%) and hip height (1.3 ± 0.6 cm, 1%) at first conception. Maternal heterosis for calf birth weight was 3.6 ± 0.5 (12%) and 2.4 ± 0.6 kg (8.6%) for Romosinuano-Angus and Brahman-Angus. In Romosinuano-Brahman and Brahman-Angus, heterosis for exit velocity was 0.23 ± 0.09 (10%) and 0.5 ± 0.1 m/s (21%). The direct breed effect of Romosinuano was to reduce age (-58.2 ± 18.9 d), BW (-57.6 ± 10.5 kg), and hip height (-2.6 ± 1.1 cm) at the time of first conception (P < 0.01), and the direct Brahman effects (P < 0.001) were large and numerically positive for these traits (169.8 ± 20.8 d, 93.3 ± 11.6 kg, and 14 ± 1.2 cm). Use of Romosinuano in crossbreeding programs with Brahman may be useful for decreasing the age at first conception. The larger birth weights of calves born to Romosinuano-Angus cross heifers would not be desirable in southern cow-calf operations.

Growth and reproductive development from weaning through 20 months of age among breeds of bulls in subtropical Florida

To determine the effect of breed on growth and reproductive development, weaned bulls in each of 2 yr were managed as a single group for approximately a year. In Year 1, the study group consisted of 24 Angus, 24 Brahman, 20 Hereford and 14 Senepol bulls, while in Year 2, it contained 25 Angus, 17 Brahman. 13 Romosinuano and 9 Nellore x Brahman bulls. Body and testicular growth measurements were recorded at 6-wk intervals. At approximately 1 yr of age and quarterly thereafter (4 periods), bulls were evaluated for libido, pubertal status, and GnRH-induced LH and testosterone secretion. Significant breed-by-age interactions occurred for most growth measurements. Brahman bulls (Bos indicus ) were (P < 0.05) older and heavier at puberty than Angus, Hereford, Senepol and Romosinuano bulls (Bos taurus ). Libido scores were lowest for Brahman and Nell ore x Brahman bulls (Bos indicus ). highest for Angus and Hereford bulls (temperate Bos taurus breeds) and intermediate for Senepol and Romosinuano bulls (tropical Bos taurus breeds; P < 0.05). Differences were not consistent among breeds or between years for GnRH-induced LH secretion. In both years, basal testosterone concentrations and areas under the GnRH-induced testosterone curve were higher (P < 0.05) for Angus and Hereford bulls (temperate breeds) than for Brahman, Senepol, Romosinuano and Nellore x Brahman bulls (tropical breeds). In conclusion, reproductive development of Senepol and Romosinuano bulls (tropical Bos taurus breeds) was more similar to Angus and Hereford bulls (temperate Bos taurus breeds) than to Brahman and Nellore x Brahman bulls (Bos indicus ).

Endocrine Characteristics of a Miniature Condition in Brahman Cattle: Circulating Concentrations of Some Growth-Related Hormones

Abstract Four miniature Brahman calves born in 1988 and 1989, along with four contemporary sex-matched Brahman control calves, were used in experiments to determine circulating concentrations of insulin-like growth factor I (IGF-I), growth hormone (GH), insulin, triiodothyronine, and thyroxine, and plasma glucose response to insulin challenge. The effect of plane of nutrition on plasma concentrations of IGF-I and insulin was also determined and a clinical screen of blood chemistries was conducted to determine effects of calf type. Plasma IGF-I was six times higher in control calves compared with miniature calves (209.0 vs 35.0 ng/ml; P = 0.001). However, miniature calves had mean plasma GH about six times higher (37.8 vs 6.2 ng/ml; P = 0.004) and had twice as many secretory episodes (9 vs 4.5; P = 0.005) over an 8-hr sampling period. Plasma concentrations of triiodothyronine (2.54 vs 1.80 ng/ml) and thyroxine (88.8 vs 56.2 ng/ml) were higher in control compared with miniature calves (P = 0.001), but concentrations of triiodothyronine and thyroxine in both calf types were within normal ranges. Although miniature calves displayed similar plasma glucose concentrations to controls, hypoglycemic response to insulin challenge tended to be greater in miniature calves. Nutritional regulation of circulating IGF-I appeared to be intact in miniature as well as control calves, as evidenced by a reduction in plasma IGF-I concentration following a decrease in plane of nutrition, and a subsequent increase in plasma IGF-I concentration following realimentation. Serum urea nitrogen was lower (P = 0.02) in control compared with miniature calves. These data describe a miniature condition in Brahman cattle that is manifested by apparently normal proportioned growth but small stature, and that is associated most notably with abnormally low circulating concentrations of IGF-I in the presence of paradoxically high circulating concentrations of GH.

Genome-wide association study and ancestral origins of the slick-hair coat in tropically adapted cattle.

The slick hair coat (SLICK) is a dominantly inherited trait typically associated with tropically adapted cattle that are from Criollo descent through Spanish colonization of cattle into the New World. The trait is of interest relative to climate change, due to its association with improved thermo-tolerance and subsequent increased productivity. Previous studies localized the SLICK locus to a 4 cM region on chromosome (BTA) 20 and identified signatures of selection in this region derived from Senepol cattle. The current study compares three slick-haired Criollo-derived breeds including Senepol, Carora, and Romosinuano and three additional slick-haired cross-bred lineages to non-slick ancestral breeds. Genome-wide association (GWA), haplotype analysis, signatures of selection, runs of homozygosity (ROH), and identity by state (IBS) calculations were used to identify a 0.8 Mb (37.7–38.5 Mb) consensus region for the SLICK locus on BTA20 in which contains SKP2 and SPEF2 as possible candidate genes. Three specific haplotype patterns are identified in slick individuals, all with zero frequency in non-slick individuals. Admixture analysis identified common genetic patterns between the three slick breeds at the SLICK locus. Principal component analysis (PCA) and admixture results show Senepol and Romosinuano sharing a higher degree of genetic similarity to one another with a much lesser degree of similarity to Carora. Variation in GWA, haplotype analysis, and IBS calculations with accompanying population structure information supports potentially two mutations, one common to Senepol and Romosinuano and another in Carora, effecting genes contained within our refined location for the SLICK locus.

Variability of hair coat and skin traits as related to adaptation in Criollo Limonero cattle.

The variation in hair coat and skin histology traits of Criollo Limonero cattle was analyzed using 213 Criollo Limonero females. Skin biopsies were obtained from slick-haired (N = 16) and normal-haired (N = 14) animals. Measured traits included hair length (HL), color coat (CC), number of hair follicles per square centimeter (NHF), sweat glands per square centimeter (NSG), sweat glands size (SGS), sebaceous glands per square centimeter (NSBG), blood vessels per square centimeter (NBV), and thickness of epidermis (TE). Hair length differed (P < 0.001) between slick- and normal-haired animals (4.9 ± 0.12 vs 10.9 ± 0.20, respectively). Differences (P < 0.01) in CC (Bayo = 144/67.6% vs Red = 69/32.4%) and HL (slick-haired = 199/93.4% vs normal-haired = 14/6.5%) were found. Distribution of slick- and normal-haired animals differed (P < 0.01) between bayo-coated and red-coated (139/62.2% vs 9/4.2%; respectively). Most (P < 0.05) red-coated animals belonged to a single family. No differences (P > 0.05) were found between slick-haired and normal-haired animals in NHF (637 ± 164 vs 587 ± 144, respectively), NSG (556 ± 134 vs 481 ± 118, respectively), NSBG (408 ± 87 vs 366 ± 77, respectively), NBV (1628 ± 393 vs 1541 ± 346, respectively), and TE (1.24 ± 0.14 vs 1.32 ± 0.12, respectively). However, SGS was greater (P < 0.01) in slick-haired than normal-haired animals. In conclusion, Criollo Limonero cattle are predominantly bayo-coated, slick-haired, with a reduced number of hair follicles relative to Zebu cattle, sweat and sebaceous glands in proportion to hair follicle numbers, and with a high blood flow irrigating the skin. There is a sub-group of red-coated animals with yellow or cream skin, thicker epidermis, and with a higher frequency of normal-haired animals. It appears that the slick hair gene has been favored by natural selection in this breed.

A miniature condition in Brahman cattle is associated with a single nucleotide mutation within the growth hormone gene

Miniature Brahman cattle at the USDA ARS Subtropical Agriculture Research Station in Brooksville, FL have normal proportioned growth but are approximately 70% of mature height and weight when compared with Brahman cattle in the same herd. Pedigree analyses suggest that the condition is inherited through a recessive allele. The miniature Brahman cattle in the Brooksville herd have been used for studies of growth and reproduction, but the underlying causative mutation is unknown. Presumably, the miniature condition could arise from a mutation in the GH gene. The objective, therefore, was to clone the GH cDNA from Brooksville miniature Brahman cattle, compare its sequence to normal Brahman cattle, and test the biological activity of the native GH protein. Messenger RNA was isolated from the pituitary, and a cDNA for the protein coding region of the GH gene was amplified by reverse-transcription polymerase chain reaction (PCR) from each of 2 miniature Brahman bulls. The cDNA were cloned into plasmid vectors, and top and bottom strands were sequenced by automated DNA sequencing. The sequence of both cDNA clones derived from miniature cattle differed from Bos indicus GH (GenBank AF034386) at base number 641 because there was a cytosine (C) instead of a thymine (T). The C to T change encoded a mutation (threonine to methionine) at amino acid 200 (T200M mutation). The mutation was confirmed by sequencing of an additional 2 miniature cattle and comparing their sequence to 2 normal cattle. The threonine is located in the fourth alpha helix of GH and is 1 of 8 amino acids that participate in binding of GH to the GH receptor. Twelve miniature Brahman and 9 normal Brahman cattle were tested by using a restriction fragment length polymorphism analysis that employed the BsmBI restriction enzyme (specific for the mutated nucleotide). The 12 miniature Brahman cattle were homozygous for the mutation (-/-). Seven of the normal Brahman cattle were homozygous for the wild-type allele (+/+), and 2 were heterozygous (+/-). When tested in a cell-based bioassay, GH isolated from the pituitary of -/- cattle (n=4) had approximately 60% activity when compared with GH isolated from the pituitary of +/+ cattle (n=5). In summary, miniature Brahman cattle were homozygous for a single nucleotide polymorphism that encodes a mutation in an amino acid involved in binding of GH to the GH receptor. Cattle of normal size had at least 1 copy of the normal GH allele. Threonine 200 in bovine GH is required for normal growth in cattle.

A Spatial Scan Statistic for Stochastic Scan Partitions

Abstract This article develops a spatial scan statistic for homogeneity analysis of point processes that utilizes stochastic scan partitions. The derivation of the sampling distribution for the statistic yields an exact test. This test has the potential for improved power over conventional alternatives when the point process is embedded in an underlying continuous random field and is recommended in situations for which the location of subregions of nonhomogeneity in the point process correspond to regions in the underlying field that can be segmented as distinct from their surroundings. The application to the detection of clustered microcalcifications in digital mammography is investigated as a motivating example.