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Abnormal fetuses, neonates, and adult offspring derived by assisted reproductive technologies have been reported in humans and mice and have been associated with increased likelihood of certain adult diseases. To test the hypothesis that bovine females derived by assisted reproductive technologies have altered postnatal growth and adult function, a retrospective cohort study evaluated survival, growth, and production traits of offspring derived by in vitro embryo production (IVP) with conventional (IVP-conv) or reverse X-sorted semen (IVP-sexed), multiple ovulation and embryo transfer, and artificial insemination (AI) in a large dairy herd. Live calves produced by IVP were born slightly heavier compared with AI calves. In addition, IVP-sexed calves had a higher cumulative mortality from 90 to 180 d of age compared with AI offspring. Mortality of IVP-conv and multiple ovulation and embryo transfer offspring was intermediate and not different from AI or IVP-sexed offspring. The altered phenotype of offspring from IVP-sexed extended to adult milk production. Cows derived by IVP-sexed produced less milk, fat, and protein in their first lactation compared with dairy cows derived by AI. Additionally, females born to nulliparous dams had a distinct postnatal phenotype compared with offspring from parous dams even when data were restricted to offspring of surrogate females. In conclusion, procedures associated with in vitro production of embryos involving use of reverse-sorted spermatozoa for fertilization result in an alteration of embryonic programming that persists postnatally and causes an effect on milk production in adulthood. Thus, some benefits of reverse-sorted semen for genetic improvement may be offset by adverse programming events. Southeast Milk Inc. Milk Checkoff Program (Belleview, FL) L.E. "Red" Larson Endowment

Thermal stress in hot humid conditions limits cattle production. The objectives for this study were to estimate genetic parameters for hair characteristics and core body temperature under low and high temperature humidity index (THI) conditions. Hair samples were collected and measured for length and diameter. Core body temperature was measured as vaginal temperature every 15 min over a 5-d period using an iButton temperature measuring device implanted in a blank CIDR in 336 heifers from the University of Florida multibreed herd (ranging from 100% Angus to 100% Brahman). Restricted maximum likelihood procedures were used to estimate heritabilities from multiple bivariate animal models using the WOMBAT program. Estimates of heritability for hair diameter, undercoat length, topcoat length, body temperature under low THI conditions, and body temperature under high THI conditions were 0.50, 0.67, 0.42, 0.32, and 0.26, respectively. The genetic parameters estimated in this study indicate a large, exploitable genetic variance which can be selected upon to improve tolerance in cattle. Breed effects for differing compositions of Brahman and Angus were also estimated. As Brahman breed composition increased by 25% undercoat length, topcoat length, body temperature under low THI conditions, and body temperature under high THI conditions decreased by 1.32 mm, 2.94 mm, 0.11 degrees C, and 0.14 degrees C, respectively. Under both low and high THI conditions, cattle with 25% Brahman breed composition or greater maintained a significantly lower body temperature than the 100% Angus breed group. The incorporation of Brahman germplasm is recommended for herds that often experience heat stress conditions in order to increase resilience to heat stress. United States Department of Agriculture (USDA)

The objectives of this study were to estimate variance components and identify regions of the genome associated with traits related to embryo transfer in Holsteins. Reproductive technologies are used in the dairy industry to increase the reproductive rate of superior females. A drawback of these methods remains the variability of animal responses to the procedures. If some variability can be explained genetically, selection can be used to improve animal response. Data collected from a Holstein dairy farm in Florida from 2008 to 2015 included 926 superovulation records (number of structures recovered and number of good embryos), 628 in vitro fertilization records (number of oocytes collected, number of cleaved embryos, number of high-and low-quality embryos, and number of transferrable embryos), and 12,089 embryo transfer records (pregnancy success). Two methods of transformation (logarithmic and Anscombe) were applied to count variables and results were compared. Univariate animal models were fitted for each trait with the exception of pregnancy success after embryo transfer. Due to the binary nature of the latter trait, a threshold liability model was fitted that accounted for the genetic effect of both the recipient and the embryo. Both transformation methods produced similar results. Single-step genomic BLUP analyses were performed and SNP effects estimated for traits with a significant genetic component. Heritability of number of structures recovered and number of good embryos when log-transformed were 0.27 +/- 0.08 and 0.15 +/- 0.07, respectively. Heritability estimates from the in vitro fertilization data ranged from 0.01 +/- 0.08 to 0.21 +/- 0.15, but were not significantly different from zero. Recipient and embryo heritability (standard deviation) of pregnancy success after embryo transfer was 0.03 (0.01) and 0.02 (0.01), respectively. The 10-SNP window explaining the largest proportion of variance (0.37%) for total structures collected was located on chromosome 8 beginning at 55,663,248 bp. Similar regions were identified for number of good embryos, with the largest proportion of variance (0.43%) explained by a 10-SNP window on chromosome 14 beginning at 26,713,734 bp. Results indicate that there is a genetic component for some traits related to superovulation and that selection should be possible. Moreover, the genetic component for superovulation traits involves some genomic regions that are similar to those for other fertility traits currently evaluated. Agriculture and Food Research Initiative Grant from the National Institute of Food and Agriculture - 2013-68004-20365 United States Department of Agriculture (USDA) USDA Agricultural Research Service - 1265-31000-096-00 Southeast Milk Checkoff Program

The objective of this study was to investigate the effects of increasing doses of carvacrol (C) and/or thymol (T) on the performance, rumen fermentation, and blood and carcass parameters of Merino sheep. Eighty-four 12-week-old male Merino lambs were randomly assigned to 7 treatment groups. The sheep were fed with the same concentrate mixtures including a control diet, carvacrol 100 mg/kg (C 100 ), carvacrol 300 mg/kg (C 300 ), thymol 100 mg/kg (T 100 ), thymol 300 mg/kg (T 300 ), carvacrol+thymol 100 mg/kg (C 50 +T 50 ), and carvacrol+thymol 300 mg/kg (C 150 +T 150 ). The C and/or T supplementation did not affect the feed conversion. The lambs fed with C and/or T diets had higher rumen pH, NH 3 -N, and total volatile fatty acid (VFA) compared to those in the control group. However, essential oil supplementation did not change the molar concentration of VFA. The serum urea and glucose in C and/or T groups were not found significant on days 0, 35, and 70 compared to the control group. Slaughter weights and other carcass parameters were similar between the groups. The effects of C and/or T supplementation on the rumen and production parameters showed limited effects when lambs were fed with the high concentrate diets.

The objective of this study was to investigate the effect of processing type of feed on the fattening performance and carcass traits of Awassi ram lambs. A total of 26, three month old Awassi ram lambs were used and randomly allocated into three groups (group 1, fed with ground feed, n = 8; group 2, fed with pellet feed, n = 9; group 3, fed with extruded pellet feed, n = 9). The results showed that total weight gain and Average Daily Gain (ADG) of ram lambs during the study were 12.8 +/- 1.1 kg and 180.9 +/- 17.7 g for group 1, 12.8 +/- 0.9 kg and 252.1 +/- 21.5 g for group 2 and 14.6 +/- 0.6 kg and 287.8 +/- 23.4 g for group 3, respectively. The difference of ADG among groups were significant (p0.05). The results of the current study shows that feeding of Awassi ram lambs with extruded feed had positive effects on fattening performance, Feed Conversion Rate (FCR) and fattening period which are economically important for sheep farms.

We compared diurnal patterns of vaginal temperature in lactating cows under grazing conditions to evaluate genotype effects on body temperature regulation. Genotypes evaluated were Holstein, Jersey, Jersey x Holstein and Swedish Red x Holstein. The comparison of Holstein and Jersey versus Jersey x Holstein provided a test of whether heterosis effects body temperature regulation. Cows were fitted with intravaginal temperature recording devices that measured vaginal temperature every 15 min for 7 days. Vaginal temperature was affected by time of day (P < 0.0001) and genotype x time (P < 0.0001) regardless of whether days in milk and milk yield were used as covariates. Additional analyses indicated that the Swedish Red x Holstein had a different pattern of vaginal temperatures than the other three genotypes (Swedish Red x Holstein vs others x time; P < 0.0001) and that Holstein and Jersey had a different pattern than Jersey x Holstein [(Holstein + Jersey vs Jersey x Holstein) x time, P < 0.0001]. However, Holstein had a similar pattern to Jersey [(Holstein vs Jersey) x time, P > 0.10]. These genotype x time interactions reflect two effects. First, Swedish Red x Holstein had higher vaginal temperatures than the other genotypes in the late morning and afternoon but not after the evening milking. Secondly, Jersey x Holstein had lower vaginal temperatures than other genotypes in the late morning and afternoon and again in the late night and early morning. Results point out that there are effects of specific genotypes and evidence for heterosis on regulation of body temperature of lactating cows maintained under grazing conditions and suggest that genetic improvement for thermotolerance through breed choice or genetic selection is possible.

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.h(-1)/m(2); outdoor 82 vs. 61 g.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. Initiative for Future Agricultural and Food Systems Program (2001-52101-11318 )

A total of 1 200 broiler breeder eggs were collected from a commercial flock at the hen age of 37 weeks and divided into storage treatments of 5 and 15 days. Prior to storage, the eggs were further divided into pre-storage incubation (PRESI) 0 (control), 4 and 8 h treatments. Eggs in the 4 and 8 h PRESI treatment were incubated at a standard dry-bulb temperature of 38.0 degrees C. All eggs were weighed prior to and after storage, then incubated in a commercial setter and hatcher for 21 days. After the incubation, all unhatched eggs were opened to determine fertility, hatchability and embryonic death. The 4 and 8 h PRESI treatment significantly decreased hatchability results of long-term stored eggs compared to non-heated eggs. Hatchability results of eggs stored for 5 days were significantly better compared to eggs stored for 15 days. Subsequent growth performance of progeny was not significantly affected except for the main effect of egg storage on feed conversion. There were significant PRESI x egg storage interactions for apparent fertility, hatchability of total and fertile eggs and embryonic mortality. It was concluded that the PRESI treatment did not have a detrimental effect on the hatchability of broiler breeder eggs stored for 5 days and it might even increase hatchability while it had a detrimental effect on the hatchability of broiler breeder eggs stored for 15 days.

Les effets d'une pre-incubation sur l'eclosabilite des oeufs de cailles reproductrices et la croissance des cailleteaux. Un total de 1800 oeufs de caille ont ete obtenus a partir de deux troupeaux âges de 20 et 37 semaines. Avant le stockage, la moitie des oeufs a subi une pre-incubation a 37,5 °C (groupe PRESI) pendant 8 heures et l'autre moitie non (groupe temoin). Apres la pre-incubation, les oeufs du groupe PRESI comme ceux du groupe temoin ont ete stockes a 15 °C et 65 % d'humidite relative pendant 5 ou 15 j et ont ete tournes deux fois par jour. Tous les oeufs ont ete peses avant et apres stockage, puis incubes pendant 17 j dans un incubateur commercial. A la fin de cette periode, tous les oeufs non eclos ont ete casses afin de determiner la fertilite, l'eclosabilite et le stade de mortalite embryonnaire eventuelle. Le traitement PRESI 8 h a significativement ameliore l'eclosabilite des oeufs (82,6 %) par rapport au groupe temoin (79,7 %). Le taux d'eclosion des oeufs obtenus avec les jeunes reproducteurs a ete superieur (84,7 %) a celui obtenu avec les reproducteurs plus âges (77,6 %). Aucune difference significative liee a la duree du stockage n'a pu etre detectee. La croissance des jeunes n'a ete significativement modifiee que par la duree du stockage. Le poids corporel moyen a 42 j des cailleteaux issus des oeufs stockes 5 j a ete de 191,3 g alors qu'il etait seulement de 174,5 g apres 15 j de stockage. Le traitement PRESI a reduit la mortalite et l'indice de consommation (IC) des cailleteaux issus des jeunes reproducteurs, mais pas ceux des cailleteaux issus des reproducteurs plus âges. Il a egalement ameliore l'IC des cailleteaux a 42 j, notamment celui des œufs stockes pendant 15 j comparativement a ceux stockes pendant 5 j (P < 0,03). La pre-incubation (PRESI) pendant 8 h n'a pas eu d'effet negatif sur l'eclosabilite, elle peut meme ameliorer l'eclosabilite des oeufs et les performances des cailleteaux issus de jeunes reproducteurs. Des etudes complementaires restent a mettre en oeuvre pour mieux determiner la duree optimale de pre-incubation requise pour obtenir un taux d'eclosabilite maximal.

The SLICK haplotype (http://omia.angis.org.au/OMIA001372/9913/) in cattle confers animals with a short and sleek hair coat. Originally identified in Senepol cattle, the gene has been introduced into Holsteins. The objectives of the current study were to determine (1) whether lactating Holsteins with the slick hair phenotype have superior ability for thermoregulation compared with wild-type cows or relatives not inheriting the SLICK haplotype, and (2) whether seasonal depression in milk yield would be reduced in SLICK cows. In experiment 1, diurnal variation in vaginal temperature in the summer was monitored for cows housed in a freestall barn with fans and sprinklers. Vaginal temperatures were lower in slick-haired cows than in relatives and wild-type cows. In experiment 2, acute responses to heat stress were monitored after cows were moved to a dry lot in which the only heat abatement was shade cloth. The increases in rectal temperature and respiration rate caused by heat stress during the day were lower for slick cows than for relatives or wildtype cows. Moreover, sweating rate was higher for slick cows than for cows of the other 2 types. In experiment 3, effects of season of calving (summer vs. winter) on milk yield and composition were determined. Compared with milk yield of cows calving in winter, milk yield during the first 90 d in milk was lower for cows calving in the slimmer. However, this reduction was less pronounced for slick cows than for wild-type cows. In conclusion, Holsteins with slick hair have superior thermoregulatory ability compared with non-slick animals and experience a less drastic depression in milk yield during the summer. USDA National Institute of Food and Agriculture (Washington, DC) (2010-85122-20623) (2013-68004-20365) Southeast Milk Inc. Milk Check-off Program

Heat stress has an important effect on the welfare of livestock and causes significant changes in biological functions. This study was carried out to investigate the behavioral differences of Brown Swiss (BS) and Holstein (H) feedlot cattle reared in a hot environment. All of the cattle were housed in a semi-open feedlot barn. The individual behavioral response variables measured were feeding, drinking, rumination, standing, resting, locomotor activity and elimination (urinating and defecating). For each animal, behavioral observations were recorded at 10 mm intervals for 1 h starting at 06:00, 10:00, 13:00, 16:00, 20:00 and 23:00 h. The effect of breed, time of the day and hour of observation and the interactions of these factors were included in the model. The data were analyzed using the PROC GLM procedure in SAS. There were significant interactions between breed and time of observation for rumination (p < 0.001), standing (p < 0.001), resting (p < 0.01), time of feeding and locomotor activities (p < 0.05). Overall, feeding behavior was greater for BS cattle (p < 0.05). Resting behavior was greater for H (p < 0.01) and was primarily observed late at night (23:00 h). The observed effects of breed on behavior within the observation times from 06:00 to 23:00 h were significant (p < 0.05 and p < 0.001) except for the hour of observation beginning at 10:00 h (p > 0.05). BS cattle exhibited more frequent standing behavior at 13:00 h, whereas H cattle exhibited more frequent standing behavior at 16:00 h (p < 0.01). The welfare of male H feedlot cattle was concluded to be more affected than that of male BS feedlot cattle when the ambient temperature was high.

Heat stress compromises production, fertility, and health of dairy cattle. One mitigation strategy is to select individuals that are genetically resistant to heat stress. Most of the negative effects of heat stress on animal performance are a consequence of either physiological adaptations to regulate body temperature or adverse consequences of failure to regulate body temperature. Thus, selection for regulation of body temperature during heat stress could increase thermotolerance. The objective was to perform a genome-wide association study (GWAS) for rectal temperature (RT) during heat stress in lactating Holstein cows and identify SNPs associated with genes that have large effects on RT. Records on afternoon RT where the temperature-humidity index was >= 78.2 were obtained from 4,447 cows sired by 220 bulls, resulting in 1,440 useable genotypes from the Illumina BovineSNP50 BeadChip with 39,759 SNP. For GWAS, 2, 3, 4, 5, and 10 adjacent SNP were averaged to identify consensus genomic regions associated with RT. The largest proportion of SNP variance (0.07 to 0.44%) was explained by markers flanking the region between 28,877,547 and 28,907,154 bp on Bos taurus autosome (BTA) 24. That region is flanked by U1 (28,822,883 to 28,823,043) and NCAD (28,992,666 to 29,241,119). In addition, the SNP at 58,500,249 bp on BTA 16 explained 0.08% and 0.11% of the SNP variance for 2- and 3-SNP analyses, respectively. That contig includes SNORA19, RFWD2 and SCARNA3. Other SNPs associated with RT were located on BTA 16 (close to CEP170 and PLD5), BTA 5 (near SLCO1C1 and PDE3A), BTA 4 (near KBTBD2 and LSM5), and BTA 26 (located in GOT1, a gene implicated in protection from cellular stress). In conclusion, there are QTL for RT in heat-stressed dairy cattle. These SNPs could prove useful in genetic selection and for identification of genes involved in physiological responses to heat stress. United States Department of Agriculture (USDA) (2010-85122-20623) United States Department of Agriculture (USDA) (2013-68004-20365) Southeast Dairy Inc. Milk Checkoff Program

The present study was carried out to determine the sex of the fertilized white layer eggs with using morphological measurements. A total of 300 Super Nick White Layer (54 wks of age) eggs were incubated and sexed in the end of incubation period. Before incubation egg length, width and weight were measured. The egg volume and shape index were estimated with using these measurements for each egg. The effect of egg weight and replicate number was not significant on the sex of the hatching chick (p > 0.05). The effects of egg shape index (p = 0.001), egg length (p = 0.0018), egg width (p < 0.01) and volume (p = 0.004) of the egg had significant effect on the sex of hatching chick. According to the results of the current study, morphological measurements of the pre-incubated egg might be an indicator of sex of the hatching chick. The shape index and egg volume were more informative for the likelihood of the sex of hatching chick. According to the positive results of the current study, it is possible to incubate more female chicks with using the morphological measurements of egg. This may increase the incubation capacity and decrease the number male chicks that are killed at layer hatcheries.

Genetic selection for body temperature during heat stress might be a useful approach to reduce the magnitude of heat stress effects on production and reproduction. Objectives of the study were to estimate the genetic parameters of rectal temperature (PT) in dairy cows in freestall barns under heat stress conditions and to determine the genetic and phenotypic correlations of rectal temperature with other traits. Afternoon PT were measured in a total of 1,695 lactating Holstein cows sired by 509 bulls during the summer in North Florida.. Genetic parameters were estimated with Gibbs sampling, and best linear unbiased predictions of breeding values were predicted using an animal model. The heritability of RT was estimated to be 0.17 +/- 0.13. Predicted transmitting abilities for rectal temperature changed 0.0068 +/- 0.0020 degrees C/yr from (birth year) 2002 to 2008. Approximate genetic correlations between RT and 305-d milk, fat, and protein yields, productive life, and net merit were significant and positive; whereas approximate genetic correlations between TIT and somatic cell count score and daughter pregnancy rate were significant and negative. Rectal temperature during heat stress has moderate heritability, but genetic correlations with economically important traits mean that selection for RT could lead to lower productivity unless methods are used to identify genes affecting RT that do not adversely affect other traits of economic importance. National Research Initiative Competitive from the USDA National Institute of Food and Agriculture - 2010-85122-20623

The cooling performance of a traditional (control) and two stage evaporative pad cooling system (experiment), including pad and fan with tunnel ventilation, for poultry houses and the growth performance of broilers reared in these systems was compared in a study performed during extreme summer temperatures. The experimental unit had a two stage pad cooling system, which consisted of underground tubes and a box, followed by a pad cooling system with tunnel ventilation. The control unit had a traditional evaporative cooling system, including pad and fan with tunnel ventilation. Air temperature, relative humidity, and saturation efficiency were used to determine the cooling performance of the systems. Live body weight gain, feed conversion ratio, and mortality rate were used to monitor the growth performance of broilers raised in these systems. The air temperature and relative humidity of incoming house and exhausted air in the two stage pad cooling system were found to be significantly lower than those of the traditional system (P < 0.05). The cooling efficiency or saturation efficiency in the two stage cooling system was found to be slightly greater than that of the traditional system. Body weight gain was also significantly influenced by the cooling system (P < 0.05). The results indicated that two stage pad cooling is a more efficient method to alleviate heat stress in broilers during heat stress conditions and to improve growth performance.

Heat stress has important effects on the welfare of livestock. The effects of heat stress in cattle include changes in biological functions and behaviors. The aim of this study was to investigate the behavioral differences between light and heavy feedlot cattle reared in a hot environment. Sixteen male Holstein feedlot cattle were allocated to light (353.8 +/- 15.5 kg, n = 8) and heavy (737.1 +/- 15.8 kg, n = 8) groups according to their live weight and were kept in a semi-open feedlot barn. The individual behavioral response variables measured were standing, lying, feeding, drinking, ruminating, locomotor activity and elimination (urinating and defecating). The effects of group, day, observation time, replicate and all interactions were included in an explanatory statistical (GLM) model. The data were analyzed using the PROC GLM procedure of SAS. Overall, the heavy cattle spent more time standing (P < 0.001), lying (P < 0.001), and eliminating (P < 0.05) compared to the light group. In contrast, the light group spent more time eating, drinking and ruminating (P < 0.001). Locomotor activity did not differ significantly between groups (P > 0.05). During the day, heavy cattle spent more time standing (at 1600 hours) and less time eating in comparison with the light cattle (P < 0.001) (at 1300 and 1600 hours). Light and heavy feedlot cattle behaved differently in a hot environment. The findings of the study indicate that the welfare of the heavy Holstein feedlot cattle was impacted negatively when the ambient temperature was high (at 1300 hours).

Several temperature-humidity indexes (THI) have been used to estimate the degree of thermal stress experienced by dairy cows. The present objectives were to develop equations using meteorological variables that predicted rectal temperature of lactating cows in a subtropical environment and compare the goodness of fit of these equations to those using 8 different THI. Rectal temperature was measured between 1500 and 1700 h in 1,280 lactating Holstein cows in north central Florida between August and December. Meteorological data recorded in the barn where cows were located included dry bulb temperature (T(db)), relative humidity (RH), dew point temperature, and wind speed. Wet bulb temperature was calculated. In the first series of analyses, regression analysis was used to model rectal temperature using the meteorological variables as well as THI. The r(2) using T(db) (0.41) was slightly less than for models using all but one THI (r(2) between 0.42 and 0.43). The r(2) for equations using T(db) could be improved by adding RH (r(2) = 0.43) or RH and RH(2) (r(2) = 0.44) to the model. In the second analysis, regression analysis was performed using forward selection, backward elimination, and stepwise selection procedures with the meteorological variables. All models gave a similar goodness of fit (r(2) = 0.44). An analysis of variance with rectal temperature as a class variable was performed to determine the least squares means of meteorological measurements associated with hyperthermia. A T(db) of 29.7 degrees C was associated with rectal temperature of 39 degrees C, and a T(db) of 31.4 degrees C was associated with rectal temperature of 39.5 degrees C. In conclusion, T(db) is nearly as good a predictor of rectal temperatures of lactating Holsteins in a subtropical environment as THI. Estimates of values of meteorological variables associated with specific rectal temperatures should prove valuable in relating environmental conditions to the magnitude of hyperthermia experienced by heat-stressed cows.

This study was made to compare physical chick quality indicators such as chick length and feather colour and their effects on the uniformity and subsequent growth performance in broiler. For this reason; 600 day old male chicks were used. Chicks were classified into two groups on the basis of their feather colour: deep and light yellow. Then, chicks in each group were further divided into three groups as small, middle and large according to their body length. The length of the middle group animals was varied between 18.0–18.3 cm, while that of the largest group was greater than 18.3 cm and the small group was lesser than 18.0 cm. A positive correlation between chick length and chick weight was observed in all groups at the 0 day of age. Body length uniformity in day old chick was more important than body weight uniformity. Longer chicks exhibited better growth potential throughout the experiment. The feeding efficiency and survival rate of longer chicks were numerically greater compared to smaller chicks. There were no significant differences for subsequent growth parameters in feather colour groups. Consequently; length of day old chick can be used as important criteria for selection of higher quality chicks having better growth performance.