(Co)Variance components and genetic parameter estimates for growth traits in Moghani sheep

Genetic parameters were estimated for birth weight (BW), weaning weight (WW), yearling weight (YW), average daily gain from birth to weaning (ADG1) and average daily gain from weaning to yearling (ADG2) in Moghani sheep. Maximum number of data was 4237 at birth, but only 1389 records at yearling were investigated. The data was collected from 1995 to 2007 at the Breeding Station of Moghani sheep in Jafarabad, Moghan, Iran. (Co)Variance components and genetic parameters were estimated with different models which including direct effects, with and without maternal additive genetic effects as well as maternal permanent environmental effects using restricted maximum likelihood (REML) method. The most appropriate model for each trait was determined based on likelihood ratio tests and Akaike's Information Criterion (AIC). Maternal effects were important only for pre-weaning traits. Direct heritability estimates for BW, ADG1, WW, ADG2 and YW were 0.07, 0.08, 0.09, 0.09 and 0.17, respectively. Fractions of variance due to maternal permanent environmental effects on phenotypic variance were 0.08 for ADG1. Maternal heritability estimates for BW and WW were 0.18 and 0.06, respectively. Multivariate analysis was performed using the most appropriate models obtained in univariate analysis. Direct genetic correlations among studied traits were positive and ranged from 0.37 for BW–ADG2 to 0.85 for ADG1–YW. Maternal genetic correlation estimate between BW and WW was 0.33. Phenotypic and environmental correlation estimates were generally lower than those of genetic correlation. Low direct heritability estimates imply that mass selection for these traits results in slow genetic gain.     

Crossbreeding effects on pig growth and carcass traits from two Iberian strains

An experiment of a 2×2 full diallelic cross between two contemporary Iberian pig strains (Retinto: RR, and Torbiscal: TT) was conducted to estimate the crossbreeding effects for growth and carcass traits. Phenotypic records were obtained under intensive management and consisted of two different data sets. The first set comprised growth traits until weaning and was collected at two different farms (6236 and 1208 records, respectively). Specific data included individual piglet weight at birth and at weaning at 28 days and average daily gain from birth to weaning at 28 days (ADG28) for both RR and TT and their reciprocal crosses. The second set comprised growth data from birth to slaughter (~340 days and ~160 kg) and carcass traits from 349 individuals (randomly) sampled at weaning from the first dataset. Data were analyzed through a Bayesian analysis by using a reparameterization of Dickerson’s model that allowed estimation of the posterior distributions of the following crossbreeding effects: average maternal breed effect (gM), average paternal breed effect (gP) and individual heterosis (hI). Results showed that the relative magnitude of crossbreeding effects depends on the trait analyzed. Crosses where Torbiscal strain was used as mother (RT and TT) achieved the greatest performance for all growth traits at weaning, leading to remarkable gM effects. The most outstanding example is the case of ADG28 where the probability of relevance was one. In contrast, TR cross showed the greatest differences from RR cross for all growth at slaughter and carcass traits. These differences were mainly due to hI and gP crossbreeding parameters. In particular, the posterior mean of hI was more noticeable for live weight at slaughter, average daily gain at slaughter and carcass length, while gP was more relevant for hams (kg) and loins (kg) representing from 3% to10% of average performance of traits. Hence, growth traits at weaning did not reveal any notable advantage of the crossbreeding scheme because of the superiority of the Torbiscal strain with respect to its mothering ability and the small hI. However, results from growth and carcass traits at slaughter would support the implementation of a TR crossbred system. It would allow exploitation of both the gP of the Torbiscal strain and the hI between these two Iberian pig strains. Additionally, gP estimates and phenotypic differences between reciprocal crosses might suggest signs of the presence of paternal genetic imprinting in primal cuts traits.     

Association od the DdeI growth hormone gene polymorphism with some performance traits in Polish Large White and Czech Large White x Polish Large White pigs

The genotypes of growth hormone gene polymorphisms (GH-DdeI, GH-MspI, GH-HaeII, GH-ApaI, GH-CfoI) were determined in 78 pigs [Czech Large White sires (CLWsire line) x Polish Large White (PLW) sows, Polish Large White sires x Polish Large White sows], by the PCR-RFLP method. Preliminary studies found only GH DdeI polymorphism to be associated with performance traits. The associations of this polymorphism with growth and carcass traits were investigated. The linear model included the effects of candidate genes, genetic groups, sex and linear covariables of age at slaughter and body weight at weaning. The DdeI polymorphism of the GH gene showed associations with carcass length (P 相似文献   

Genetic parameters for thermoregulation and production traits in lactating sows reared in tropical climate

The objective of this study was to estimate the genetic parameters for thermoregulation traits and the relationships with performance of Large White lactating sows reared in a tropical humid climate. The thermoregulation traits were rectal temperature (RT), cutaneous temperature (CT) and respiratory rate (RR) during lactation measured in the afternoon (1200 h) and in the morning (0700 h). The production traits were sow’s average daily feed intake (ADFI), litter BW gain (LBWg) and sow’s proportion of BW change between farrowing and weaning (BWc). Complete data included 931 lactating performance on 329 Large White sows from the INRA experimental unit in Guadeloupe (French West Indies). Random regression models using linear spline functions were used for longitudinal data (RT, CT, RR and daily feed intake). Results showed that when ignoring values at the beginning and the end of lactation, the traits studied can be treated as the same trait throughout days of lactation, with fairly constant heritability and variance. However, largest heritabilities and genetic variances were estimated in mid-lactation. Heritability estimates on average performance during lactation were low to moderate for thermoregulation traits (0.35±0.09 for RT, 0.34±0.12 for CT and 0.39±0.13 for RR). Heritability estimates for production traits were 0.26±0.08 for ADFI, 0.20±0.07 for BWc and 0.31±0.09 for LBWg. Significant genetic correlations between thermoregulation traits and production traits were only obtained for ADFI and RR (0.35±0.12). From this study it can be concluded that thermoregulation traits are heritable, indicating that there are genetic differences in heat stress tolerance in lactating Large White sows.     

Sows with high milk production had both a high feed intake and high body mobilization

Selection for increased litter size have generated hyper-prolific sows that nurses large litters, however limited knowledge is available regarding the connection between milk production, feed intake and body mobilization of these modern sows. The aim of the current study was to determine what characterized sows with high milk production and nursing large litters, differences between sows of different parities and effects of lactational performance on next reproductive cycle. In total 565 sows (parity 1 to 4) were studied from 7 days before farrowing until weaning. On day 2 postpartum litters were standardized to 14 piglets. Weight and back fat thickness of sows were measured at day 7 prepartum, day 2 postpartum and at weaning. Litters were weighed at day 2 and at weaning. Pearson correlation coefficients between variables were calculated and regression models were developed. The average daily feed intake (ADFI) of the sows was 6.1±1.1 kg/day, average daily gain (ADG) of the litter was 2.92±0.53 kg/day and sows weaned 13.0±1.1 piglets. First parity sows generally had a lower ADFI and milk production and a decrease in total born piglets in next litter compared with parity 2 to 4 sows, which could be explained by a relatively higher proportion of their body reserves being mobilized compared with multiparous sows. The ADG of the litter was positively related by ADFI of the sows, litter size and BW loss and increasing the ADFI with 1 kg/day throughout lactation likely increased the ADG of the litter with 220 to 440 g/day in parity 1 to 4, respectively. Increasing the ADFI by 1 kg/day reduced the BW loss with 6.6 to 13.9 kg of parity 1 to 4 sows, respectively, during lactation, whereas increasing the average milk yield with 1 kg/day raised the BW loss with 4.3 to 21.0 kg of the four parities during lactation. The number of total born piglets in the next litter was positively related to the number of piglets born in the previous litter. In conclusion, both a high feed intake and a high mobilization of body reserves was a prerequisite for a high milk production. The sows might be very close to the physical limit of what they can ingest and future research should therefore, focus on optimizing the dietary energy and nutrient concentrations of diets for lactating hyper-prolific sows and herein distinguish between primiparous and multiparous sows.     

Genetic parameter estimates for pre-weaning performance and reproduction traits in Markhoz goats

Genetic parameters for growth, mortality and reproductive performances of Markhoz goats were estimated from data collected during 1993–2010 at Markhoz goat Performance Testing Station in Sanandaj, Iran. For kid performance traits 3763 records were available for birth weight (BW), 2931 for weaning weight (WW), average daily gain (ADG) and Kleiber ratio (KR) (approximated as ADW/WW^0.75) and 3032 for pre-weaning mortality (PWM). For doe reproductive performance traits there were 2920 records available for litter size at birth (LSB), litter size at weaning (LSW), total litter weight at birth (TLWB) and litter mean weight per kid born (LMWKB), and 2182 for total litter weight at weaned (TLWW) and litter mean weight per kid weaned (LMWKW). Genetic parameters were estimated with univariate and bivariate models using restricted maximum likelihood (REML) procedures. Random effects were explored by fitting additive direct genetic effects, maternal additive genetic effects, maternal permanent environmental effects, the covariance between direct and maternal genetic effects, and common litter effects in different models for pre-weaning traits of kids. Also, in addition to an animal model, sire and threshold models, using a logit link function, were used for analyses of PWM. Models for LSB, LSW, TLWB, TLWW, LMWKB, and LMWKW included direct additive genetic effects, permanent environmental effects due to the animal as well as service sire effects. Estimated direct heritabilities were moderate for pre-weaning traits (0.22 for BW, 0.16 for WW, 0.21 for ADG, and 0.27 for KR and 0.29 for PWM), and low for reproduction traits (0.01 for LSB, 0.01 for LSW, 0.02 for TLWB, 0.03 for TLWW, 0.07 for LMWKB, and 0.06 for LMWKW). The estimates for the maternal additive genetic variance ratios were lower than direct heritability for BW (0.07) and KR (0.04). The estimate for the maternal permanent environmental variance ratios (c²) varied from 0.01 for KR to 0.07 for WW and ADG. The magnitude of common litter variance ratios (l²) was more substantial for BW (0.46) than the PWM (0.19) and KR (0.16). The estimate for the permanent environmental variance due to the animal (c²) ranged from 0.03 for LMWKB to 0.07 for TLWB and LMWKW, whereas service sire effects (s²) ranged from 0.02 to 0.04. The correlation between direct and maternal genetic effects were negative and high for BW (?0.51) and KR (?0.62). The genetic correlations between pre-weaning growth traits were positive and moderate to strong, as were genetic correlations between reproductive traits. Between BW and PWM the correlation was ?0.35. Phenotypic and environmental correlations for all traits were generally lower than genetic correlations.     

Genetic relationship between weaning weight and milk yield in Nguni cattle

A study was conducted to estimate the genetic relationship between weaning weight and milk yield in Nguni cattle. Milk yield data (n=125) were collected from 116 Nguni cows from Mara Research Station located in Limpopo Province and Loskop South Farm located in Mpumalanga Province using the weigh-suckle-weigh technique. Weaning weight data (n=19 065) were obtained from stud Nguni cattle from 146 herds distributed throughout South Africa. Estimates of (co)variance components for milk yield and weaning weight were calculated using PEST and VCE softwares. The average weaning weight, age of the calf at weaning and 24-h milk yield was 158.94 kg, 210 days and 5.25 kg/day, respectively. Heritability estimates for milk yield, direct and maternal weaning weight were 0.22±0.238, 0.47±0.039 and 0.25±0.029, respectively. Estimates of genetic correlations for milk yield and maternal weaning weight, milk yield and direct weaning weight, direct and maternal weaning weight were 0.97±0.063, −0.71±0.416 and −0.56±0.247, respectively. The results indicate that maternal weaning weight is genetically highly predictive of milk yield in Nguni cattle. Maternal breeding values for weaning weight could therefore be used as a selection criterion to improve milk yield in Nguni cattle.     

The Asp298Asn missense mutation in the porcine melanocortin-4 receptor ( MC4R) gene can be used to affect growth and carcass traits without an effect on meat quality

A promising tool to improve daily gain in pigs is the missense mutation (Asp298Asn) in the melanocortin-4 receptor (MC4R) gene, especially in the Belgian pig industry where the slow-growing Piétrain breed is very frequently used as the sire breed. The MC4R is expressed in the appetite-regulating region of the brain where it regulates feed intake and energy balance. The mutation has been associated with differences in fatness, daily gain and feed intake. However, less information on the correlated effects on meat quality is available. In order to evaluate the influence of the MC4R mutation on carcass and meat quality parameters, a total of 1155 pigs of a four-way cross were slaughtered at an average live weight of 109 kg, and data about daily live-weight gain, carcass and meat quality were collected. Allelic frequencies were 0.69 for the G-allele (298Asp variant or well-conserved variant) and 0.31 for the A-allele (298Asn variant or the mutated variant). Barrows and gilts were almost equally distributed in this population with, respectively, 49.9% and 50.1%. Moreover, independent of this mutation, the relationship between average daily gain (ADG) and carcass on the one hand and meat quality traits on the other hand was evaluated in this population. A significant positive influence of the MC4R mutation on ADG (P < 0.001) was found, accompanied by a higher fat thickness (P < 0.05) and a lower carcass lean meat content (P < 0.01), whereas muscle thickness and carcass conformation traits were not affected. The effects on meat quality traits were not significant, except for a lower shear force (P = 0.054) and a higher intramuscular fat content (P = 0.052) in AA animals. In the longissimus, pH and pork quality meter (PQM) values were not influenced, and effects on drip loss and colour were not apparent. Residual correlation coefficients between ADG and carcass lean meat content on the one hand and meat quality traits on the other hand were generally very low (|r|>0.1). Higher ADG, higher carcass fat thickness and lower carcass lean meat content were correlated with slightly lower shear force values (|r|～0.1, P < 0.05). In conclusion, in the studied population, the Asp298Asn mutation in the MC4R gene was associated with improved daily gain, higher carcass fatness and almost no effect on meat quality traits.     

应用VCE4.0估计长白猪生长性状的遗传参数

应用PEST和VCE4.0对温氏长白猪的主要生长性状进行了遗传分析。利用温氏水台原种猪场1998～2002年的6344头长白猪生长性能测定记录,运用多性状动物模型REML方法估计主要生长性状的遗传参数。估计遗传力的变化范围为0.207～0.493,性状达30kg体重日龄（AGE30）、达100kg体重日龄（AGE100）、30～100kg平均日增重（ADG）和100kg体重活体背膘厚（FAT）的估计遗传力分别是0.207、0.396、0.304和0.493;FAT/ADG、FAT/AGE100、ADG/AGE100、ADG/AGE30和AGE30/AGE100的各自遗传相关为-0.343、0.180、-0.941、-0.48和0.745;它们的表型相关分别为-0.139、0.138、-0.829、-0.026 和 0.565;AGE30、AGE100、ADG和FAT的窝效应估计结果分别为0.194、0.156、0.157和0.043。     

Effect of dietary fat or starch supply during gestation and/or lactation on the performance of sows, piglets' survival and on the performance of progeny after weaning

Two trials were carried out to compare the effects of fat or starch inclusion in sow's diet on sow and litter performance. In each trial, sows were assigned to one of two treatments. In trial 1, the sows were fed diets containing either soybean oil (5%, treatment GL5) or cornstarch (11.3%, GL0) from day 35 of gestation to weaning. Daily net energy and nutrient allowance were equalised during gestation. In trial 2, the same treatments were applied only after farrowing (treatments L5 and L0, respectively). Within each trial, a batch of piglets was studied until slaughter. In trial 1, adipose cell development and total lipid content were determined on some pigs at weaning (n = 6/treatment) and at slaughter in dorsal subcutaneous adipose tissue (n = 13/group at least) and in muscle (n = 46/group at least). Piglets' birth weight was not affected by treatment in trial 1. Survival rates at birth and after 24 h of life were higher in treatment GL5 (4.0% v. 7.5% stillborn piglets in GL0 treatment, P < 0.05; 8.7% v. 12.6% of piglets alive at 24 h of age died in treatment GL0, P = 0.06). Subsequently, overall survival rate until weaning was higher in treatment GL5 (81.4% v. 75.7% of total born piglets, P = 0.03), but litter size at weaning was not significantly affected (11.3). Litter growth rate before weaning was increased when a fat-enriched diet was provided during gestation and lactation (+140 g/day per litter; P < 0.01) and to a lower extent when provided only after farrowing (+90 g/day; P < 0.05). Energy supply through fat did not decrease the mobilisation of the sow's body reserve and backfat thickness loss was even higher with treatment GL5 (P < 0.05). After weaning, pigs' average daily gain, feed : gain ratio and carcass lean content were not affected by the energy source supplied before and/or after farrowing. At weaning, the number of adipose cells in the dorsal subcutaneous adipose tissue and in the Longissimus dorsi muscle was higher in the GL5 pigs. Muscle lipid content at weaning did not differ between treatments, but it was higher at slaughter, around 110 kg, in the GL5 pigs (3.46% v. 2.58%, P < 0.001).     

IGF-1基因对长白×蓝塘猪资源群生产性能的遗传效应分析

利用F2代设计建立了由216头F2代个体组成的长白×蓝塘猪资源群,应用PCR-RFLP方法检测F2代个体IGF-1基因的多态性;通过固定模型方法估计了IGF-1不同基因型的最小二乘均值,同时采用混合模型方法分析不同性状IGF-1基因型的遗传效应,并由此计算IGF-1基因的加性和显性效应.固定模型和混合模型方法的分析结果都表明,IGF-1不同基因型对猪断奶后日增重有显著影响,AA型的遗传效应显著比AB型高20.58 g(P=0.0347),IGF-1基因对该性状的加性和显性效应分别为1.78 g和-18.81 g;对胴体组成性状也有影响,AA型和AB型对骨率的遗传效应分别极显著低于BB型5.22%(P= 0.0008)和5.19%(P=0.0007),IGF-1基因对该性状的加性和显性效应分别为-2.61%和-2.58%;AA型胴体瘦肉量的遗传效应显著比AB型少0.45 kg(P=0.0264),IGF-1基因对该性状的加性和显效应分别为0.16 kg和0.61 kg;AA型和AB型皮脂率的遗传效应比BB型分别高8.81%(P=0.0206)和7.64%(P=0.0431),对该性状的加性和显性效应分别为4.41%和3.24%.因此,IGF-1基因的遗传效应分析说明该基因对断奶后日增重、骨率、胴体瘦肉量和皮脂率等4个性状有显著的遗传影响;而加性和显性效应估计值的大小表明,IGF-1基因的遗传效应只有在皮脂率性状上加性效应相对显性效应比较高,可以作为主基因对该性状进行有效选择.     

The Norwegian sheep breeding scheme: description, genetic and phenotypic change

The developments in Norwegian sheep breeding since the early 1990s are reviewed. For the largest breeding population, the Norwegian White Sheep, results are presented for both genetic and phenotypic changes. Of the nine traits that make up the aggregate genotype, the largest gain per year, in per cent of the corresponding phenotypic average, was found for carcass grade (1.66%) and carcass weight (0.99%), number of lambs born at 1, 2 and 3 years of age (0.32% to 0.60%) and the maternal effect on weaning weight (0.26%). For fat grade, a genetic deterioration was estimated. This may be due to the too small weighting of this trait in the aggregate genotype and the true genetic parameters being somewhat different from the estimates in the prediction of breeding values. For lamb as well as ewe fleece weight, genetic change was close to zero - interpreted as mainly a correlated response to other traits in the aggregate genotype. Data for the two traits of fleece weight were, respectively, selected and few. Thus, phenotypic change was calculated for all traits except for fleece weight, and in addition for number of lambs at weaning, being indirectly selected for through number of lambs born. For all traits, with the exception of fat grade, advantageous phenotypic change was estimated. For weaning and carcass weight, the phenotypic change was less than the genetic change, while the opposite was observed for carcass and fat grade and number of lambs born. The latter traits can be more easily controlled by environmental actions, and the results thus exemplify the interdependency between environmental and genetic change.     

Sexual dimorphism and direct and maternal genetic effects on body weight in mice

Summary Genetic and phenotypic parameters for three-, six- and eight-week body weight and for weight gain between three and six weeks of age were estimated from data collected over 14 generations in a randombred control population. Genetic parameters were also estimated for sexual dimorphism in body weight and gain. Heritability estimates were substantial for body weight at all ages and for body weight gain. Additive maternal variances were also large. Estimates of the covariance between direct and maternal genetic effects were negative and substantial for three- and six-week weights and gain. Also the covariance between maternal effects on weaning weight and direct genetic effects on six- and eight-week weights were negative. These results indicate a consistent antagonism between maternal and direct genetic effects in this population.The analysis of sexual dimorphism yielded estimates of 0.87±.09 and 0.71±.14 for the correlation between additive direct effects on males and females for six-week weight and body weight gain respectively. Corresponding heritability estimates were 0.07±.09 and 0.11±.09. Heritability estimates for sexual dimorphism in three- and eight-week weights were negative.Journal Paper No. 3687 of the North Carolina State University Agricultural Experiment Station. This investigation was supported in part by NIH Grant No. GM11546.     

Genetic parameters between slaughter pig efficiency and growth rate of different body tissues estimated by computed tomography in live boars of Landrace and Duroc

In this study, computed tomography (CT) technology was used to measure body composition on live pigs for breeding purposes. Norwegian Landrace (L; n = 3835) and Duroc (D; n = 3139) boars, selection candidates to be elite boars in a breeding programme, were CT-scanned between August 2008 and August 2010 as part of an ongoing testing programme at Norsvin's boar test station. Genetic parameters in the growth rate of muscle (MG), carcass fat (FG), bone (BG) and non-carcass tissue (NCG), from birth to ～100 kg live weight, were calculated from CT data. Genetic correlations between growth of different body tissues scanned using CT, lean meat percentage (LMP) calculated from CT and more traditional production traits such as the average daily gain (ADG) from birth to 25 kg (ADG1), the ADG from 25 kg to 100 kg (ADG2) and the feed conversion ratio (FCR) from 25 kg to 100 kg were also estimated from data on the same boars. Genetic parameters were estimated based on multi-trait animal models using the average information-restricted maximum likelihood (AI-REML) methodology. The heritability estimates (s.e. = 0.04 to 0.05) for the various traits for Landrace and Duroc were as follows: MG (0.19 and 0.43), FG (0.53 and 0.59), BG (0.37 and 0.58), NCG (0.38 and 0.50), LMP (0.50 and 0.57), ADG1 (0.25 and 0.48), ADG2 (0.41 and 0.42) and FCR (0.29 and 0.42). Genetic correlations for MG with LMP were 0.55 and 0.68, and genetic correlations between MG and ADG2 were -0.06 and 0.07 for Landrace and Duroc, respectively. LMP and ADG2 were clearly unfavourably genetically correlated (L: -0.75 and D: -0.54). These results showed the difficulty in jointly improving LMP and ADG2. ADG2 was unfavourably correlated with FG (L: 0.84 and D: 0.72), thus indicating to a large extent that selection for increased growth implies selection for fatness under an ad libitum feeding regime. Selection for MG is not expected to increase ADG2, but will yield faster growth of the desired tissues and a better carcass quality. Hence, we consider MG to be a better biological trait in selection for improved productivity and carcass quality. CT is a powerful instrument in conjunction with breeding, as it combines the high accuracy of CT data with measurements taken from the selection candidates. CT also allows the selection of new traits such as real body composition, and in particular, the actual MG on living animals.     

Polymorphisms in the 5' regulatory region of myostatin gene are associated with early growth traits in Yorkshire pigs

Myostatin is a negative regulator of skeletal muscle mass. The present study cloned the 5' regulatory region of porcine myostatin gene, screened its polymorphisms and analyzed their associations with early growth traits in Yorkshire pigs. The results indicated that a fragment length polymorphism and a polymorphism concerning two nucleotide changes exist in the 5' regulatory region of porcine myostatin gene. At sites 435 and 447, allele A and allele B have the haplotypes of A-G and G-A, respectively. The allelic frequency of B is 0.475 in Yorkshire pigs. No homozygous BB genotype was detected in 9 Laiwu Black pigs. Allele B was found to have positive effect on body weight on day 21 (BW21) (P＜0.01), body weight on day 28 (BW28) (P＜0.05), body weight on day 70 (BW70) (P＜0.05), average daily gain from birth to 21 d (ADG1) (P＜0.01), average daily gain from birth to 28 d (ADG2) (P＜0.05) and average daily gain from 21 d to 70 d (ADG3) (P＜0.01), respectively. The additive effect of allele B on BW21, BW28, BW70, ADG1, ADG2 and ADG3 was 0.596±0.205 kg (P=0.0041), 0.498±0.200 kg (P=0.0136), 1.409±0.551 kg (P=0.0112), 28.39±9.74 g P=0.0041), 17.78±7.15 g (P=0.0136) and 37.00±16.92 g (P=0.0304), respectively, whereas its effect on average daily gain from 28 d to 70 d (ADG4) was not significant (P＞0.1), although BB individuals are superior in average daily gain to AA and AB.     

Genetic parameters for performance,feed efficiency,and carcass traits in Senepol heifers

Improving feed efficiency is a key breeding goal in the beef cattle industry. In this study, we estimated the genetic parameters for feed efficiency and carcass traits in Senepol cattle raised in tropical regions. Various indicators of feed efficiency [gain to feed ratio (G:F), feed conversion ratio (FCR), residual weight gain (RG), residual intake and body weight gain (RIG), and residual feed intake (RFI)] as well as growth [final BW, average daily gain (ADG), and DM intake (DMI)], and carcass [rib-eye area (REA), backfat thickness (BF), intramuscular fat score, and carcass conformation score] traits were included in the study. After data editing, records from 1 393 heifers obtained between 2009 and 2018 were used for the analyses. We fitted an animal model that included contemporary group (animals from the same farm that were evaluated in the same test season) as the fixed effect, and a linear effect of animal age at the beginning of the test as a covariate; in addition to random direct additive genetic and residual effects. The (co)variance components were estimated by Bayesian inference in uni- and bivariate analyses. Our results showed that feed efficiency indicators derived from residual variables such as RG, RIG, and RFI can be improved through genetic selection (h² = 0.14 ± 0.06, 0.13 ± 0.06, and 0.20 ± 0.08, respectively). Variables calculated as ratios such as G:F and FCR were more influenced by environmental factors (h² = 0.08 ± 0.05 and 0.09 ± 0.05), and were, therefore, less suitable for use in breeding programs. The traits with the greatest and impact on genetic progress in feed efficiency were ADG, REA, and BF. The traits with the greatest and least impact on growth and carcass traits were RG and RFI, respectively. Selection for feed efficiency will result in distinct overall effects on the growth and carcass traits of Senepol heifers. Direct selection for lower RFI may reduce DMI and increase carcass fatness at the finishing stage, but it might also result in reduced growth and muscle deposition. Residual BW gain is associated with the highest weight gain and zero impact on REA and BF, however, it is linked to higher feed consumption. Thus, the most suitable feed efficiency indicator was RIG, as it promoted the greatest decrease in feed intake concomitant with faster growth, with a similar impact on carcass traits when compared to the other feed efficiency indicators.     

Effect of daily concentrate intake at weaning on performance of Belgian Blue double-muscled rearing calves

Weaning at a different daily concentrate intake was investigated during a 140-d experimental period, using 54 male and 68 female newborn Belgian Blue double-muscled animals. They were divided into three comparable groups and received milk at 10% of their birth weight up to weaning. Concentrate was levelled off at a maximum daily intake of 3 kg, while grass hay was freely available. Weaning occurred at a daily concentrate intake level (CL) of 0.5, 0.75 and 1.0 kg, respectively. Weaning at an increased CL prolonged the milk-feeding period by 13.1 and 14.6 days, and resulted in a higher pre- and post-weaning growth rate (p < 0.05). Daily gain during the entire experimental period averaged 0.84, 0.85 and 0.88 kg for the respective groups (p = 0.065). Daily concentrate intake was not different among groups, with only a small effect of CL on intake around weaning. Early weaning resulted in a significant reduction of hay intake (p = 0.032). Total daily net energy intake increased slightly with a higher CL at weaning, so that energy conversion was slightly improved, amounting to 17.7, 17.6 and 17.4 MJ/kg gain, respectively. Energy balance during the first week after weaning was negative for CL 0.5 kg (-22%), while it was close to 0 for CL 0.75 kg (-2%) or positive for CL 1.0 kg. Most effects of CL at weaning were similar for males and females, but male calves tended to have a higher intake and a faster growth rate than females. It can be concluded that weaning should be delayed until Belgian Blue double-muscled calves consume at least 0.75 kg per day or more for reasons of welfare, although performance was hardly improved by weaning at a daily concentrate intake of more than 0.5 kg per day.     

Effects of castration and weaning conducted concurrently or consecutively on behaviour,blood traits and performance in beef calves

The objectives of this study were to evaluate the effects of Burdizzo castration and abrupt weaning on the behaviour, blood traits and performance of beef calves when weaning was conducted concurrently or consecutively to castration. In total, 64 male beef calves aged between 6 and 7 months were assigned to a 2×2 factorial design with the following treatment groups (n=16 animals per treatment): (1) castrated and concurrently weaned in week 0 (CAS-WEA); (2) castrated in week 0 and weaned in week 4 (CAS-CON); (3) bulls weaned in week 0 (BUL-WEA); and (4) bulls weaned in week 4 (BUL-CON). The behaviour of the calves was observed for 3 days following weaning. Blood was collected weekly from weeks 0 to 5 and analysed for the acute-phase protein haptoglobin, and neutrophil and lymphocyte percentages. BW was recorded weekly from weeks 0 to 7. Animals were slaughtered at 17 months and weight, dressing percentage and carcass classifications were recorded. On day 1 after weaning, the number of vocalizations (calls/10 min) was higher in BUL-WEA (7.2) and CAS-WEA (5.4) than in calves of CAS-CON (2.8) and BUL-CON (2.9) groups (P<0.05). From days 1 to 3 vocalizations decreased in all groups. CAS-CON and BUL-CON animals spent 20% lying on day 1 after weaning compared with 40% in CAS-WEA and BUL-WEA calves (P<0.05). The haptoglobin concentration decreased during the first 5 weeks after weaning in all groups independent of the castration, weaning group or its interaction (P>0.05). WEA groups showed an increased average daily gain (ADG) during weeks 0 to 3 and a reduced ADG during 4 to 7 weeks in comparison with CON animals. At slaughter, bulls were about 80 kg heavier than castrates and had a superior dressing percentage and carcass classification (P>0.05). In conclusion, weaning had a greater effect on the number of vocalizations, standing/walking and lying behaviour and ADG compared with Burdizzo castration. In comparison with undertaking the procedures separately, concurrent castration and weaning neither affected behaviour and haematological parameters nor impaired performance. There was no evidence that the concurrent application of both treatments markedly increased the stress response compared with their application at intervals of a few weeks.     

Estimates of (co)variance components due to direct and maternal effects for body weights in Jamunapari goats

Estimates of (co)variance components were obtained for weights at birth, weaning and at 6, 9 and 12 months of age in Jamunapari goats maintained at the Central Institute for Research on Goats, Makhdoom, Mathura, India, over a period of 23 years (1982 to 2004). Records of 4301 kids descended from 204 sires and 1233 does were used in the study. Analyses were carried out by restricted maximum likelihood (REML), fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Six different animal models were fitted for all traits. The best model was chosen after testing the improvement of the log-likelihood values. Direct heritability estimates were inflated substantially for all traits when maternal effects were ignored. Heritability estimates for weights at birth, weaning and at 6, 9 and 12 months of age were 0.12, 0.18, 0.13, 0.17 and 0.21, respectively. Maternal heritability of body weight declined from 0.19 at birth to 0.08 at weaning and was near zero and not significant thereafter. Estimates of the fraction of variance due to maternal permanent environmental effects were 0.09, 0.13 and 0.10 for body weights at weaning, 6 months and 9 months of age, respectively. Results suggest that maternal additive effects were important only in the early stages of growth, whereas a permanent environmental maternal effect existed from weaning to 9 months of age. These results indicate that modest rates of genetic progress appear possible for all weights.     

Genetic correlations between reproduction of crossbred ewes and the growth and carcass performance of their progeny

Genetic correlations were estimated between first cross ewe reproduction traits and growth and carcass traits of their second cross lamb progeny. The 2460 crossbred ewes were progeny of 74 maternal breed sires and mainly Merino dams. The ewes had 3 joinings to terminal sire rams with 6824 joining records resulting in 9002 lambs born and 7176 lambs slaughtered. The ewe reproduction traits included: fertility, litter size, ewe rearing ability or lamb survival, number of lambs born (NLBj) and weaned (NLWj) per ewe joined, with traits reflecting ewe productivity being total litter weight weaned (TWWj) per ewe joined and the component trait average lamb weaning weight in the litter (AWW). The lamb growth traits included weight of the lambs at birth (BWT), weaning (WWT) and post weaning (PWWT) as well as growth rate pre and post weaning. The lamb carcass traits included hot carcass weight (HCWT), dressing yield (DRESS%), fat depth (FatGR, FatC), eye muscle depth (EMD) and area (EMA) and meat quality traits (colour and pH). The genetic correlations were estimated by bivariate mixed models using ASReml. The genetic correlations between the composite reproduction traits of the ewes and the post-weaning growth rate of their lambs were high (0.67 for NLBj and 0.65 for NLWj). There were moderate positive correlations between NLWj and WWT (0.36), PWWT (0.49) and pre weaning growth (0.36) and NLBj with PWWT (0.31). BWT was negatively correlated with litter size (−0.34) and positively with ewe rearing ability (0.38). Most of the other genetic correlations were smaller than their standard errors which generally ranged from 0.2 to 0.3. The genetic correlations for HCWT with all the ewe reproduction traits were positive and moderate (0.29–0.53) and high with the ewe productivity traits that included weight of lambs (TWWj 0.98 and AWW 0.96). The genetic correlations among the other traits were variable and had high standard errors, generally ranging from 0.1 to 0.5. However there were generally negative and unfavourable genetic correlations between the reproduction traits and DRESS% and meat colour L*, whereas those with carcass fat (FatC and FatGR) were generally negative and favourable.