The estimation of nutritive value of dairy cattle feed

A survey is given of different methods used for the estimation of the net energy lactation and the digestible crude protein content of forages (grass hay, grass silage, maize silage) as well as tuber crops (fodder beet, turnips, raw potatoes), by-products (dried sugarbeet pulp, pressed sugarbeet pulp), compound feeds and raw ingredients for dairy cattle. The following methods are discussed: --methods only based on chemical parameters: crude fibre and cell walls. --methods using rumen fluid from fistulated animals: the two step in vitro digestibility technique, the Hohenheim Futterwert test. --methods using enzyme (cellulase) preparations. --the near infrared reflection spectroscopy. The estimation of the energy value of raw ingredients is discussed more in detail. Formulas for the rapid calculation of the energy value of pulp and tubers are reported. The results obtained at the National Institute for Animal Nutrition in Melle-Gontrode with the two step in vitro digestion technique and a developed cellulase method are illustrated more in detail.     

奶牛分子育种的研究进展

奶牛分子育种是将来奶牛品种改良的主要工具。奶牛主效数量性状基因座育种和转基因育种主要包括构建基因图谱 ,并据此定位主效数量性状基因座或与之连锁的DNA标记 ,通过转基因技术改良奶牛重要经济性状或研究开发乳腺生物反应器。     

奶牛高效养殖生产技术

近几年,随着人们生活水平的不断提高,奶产品需求量逐年增加,我县城郊出现了以发展饲料转化率占第一位的奶牛养殖热.饲养奶牛的过程中,多数农户饲养管理粗放,在产乳技术的诸多环节上存在很多不合理性,影响了奶牛产奶性能的发挥,造成奶牛产乳量减少,效益不高.根据笔者在实际工作中的体会,简单谈一下实现奶牛高产高效的技术要点,供奶牛户参考.     

Deterministic genetic analysis of open nucleus breeding schemes for dairy cattle in developing countries

SUMMARY: A deterministic model is used to analyze the genetic properties of a two tier dairy cattle open nucleus breeding system proposed in developing countries. Theoretical selection response rates are adjusted to account for the effects of population size and structure, selection disequilibrium, sampling losses, inbreeding, and planning horizon. Optimized nucleus progeny testing, adult or juvenile multiple ovulation and embryo transfer in sib or pedigree testing schemes are used in the nucleus. All sires come from the nucleus. Females in the base herds may be recorded and selected as bull dams or donor cows in the nucleus. The predicted genetic means in the base after a given planning horizon (20 years) for a range of situations studied, is generally highest for adult sib testing, but is higher for nucleus progeny testing than for juvenile pedigree testing schemes. The genetic means are higher with more females in the nucleus and with higher reproductive and embryo transfer success rates. The genetic level of the base is higher with higher fractions of nucleus dams born in the base, but is little affected by the proportion of the total population included in the nucleus. The genetic responses are also reduced when heritability in the base is lower than in the nucleus. Policies on the formation and running of an efficient open nucleus breeding system are discussed. Key words: nucleus breeding schemes, nucleus progeny testing, multiple ovulation and embryo transfer, genetic improvement. ZUSAMMENFASSUNG: Deterministische genetische Analyse eines offenen Nukleussystems für Milchrinder in Entwicklungsl?ndern Ein deterministisches Modell wurde zur Analyse der genetischen Eigenheiten eines "Zwei-Stufen offenen Nukleuszuchtsystem" für Milchrinder für Entwicklungsl?nder verwendet. Theoretische Selektionserfolgsraten unter Berücksichtigung der Wirkungen von Populationsgr??e und Struktur, Selektionsungleichgewicht, Zufallsschwankungen, Inzucht und Planungszeitraum für optimierte Nukleusnachkommenschaftsprüfung, adulte oder juvenile multiple Ovulation und Embryotransfer mit Geschwister- oder Pedigreeprüfungspl?nen werden berechnet. Alle Vatertiere kommen von Nukleus, Muttertiere in den Basisherden z. T. leistungsgeprüft werden als Bullenmütter oder Spenderkühe im Nukleus verwendet. Das für die Basis gesch?tzte genetische Leistungsniveau eines gegebenen Planungshorizonts (20 Jahre) wird für eine Reihe von Situationen untersucht und ist im allgemeinen am h?chsten für adulte Geschwisterprüfungssysteme, aber h?her für Nukleusnachkommenschaftsprüfung als für juvenile Pedigreeprüfungspl?ne. Genetische Fortschritte sind h?her, wenn mehr weibliche Tiere im Nukleus und h?here Reproduktions- und Transfererfolgsraten existieren. Das genetische Niveau der Basis ist h?her, wenn ein h?herer Anteil von Nukleusmuttertieren aus der Basis stammt, aber es wird wenig vom Nukleusanteil der gesamten Population tangiert. Der genetische Fortschritt wird reduziert, wenn Rentabilit?t in den Basisherden niedriger als im Nukleus ist. Die Strategien zur Bildung und Management eines wirksamen offenen Nukleuszuchtsystems werden diskutiert.     

奶牛繁殖障碍的防治

本文围绕引起奶牛繁殖障碍的3个主要因素(饲养管理不当、生殖器管疾病和繁殖技术失误),从奶牛繁殖障碍的发病原因、临床症状、诊断方法、治疗原则以及预防对策上进行了概述。     

Fit of Wood's function to daily milk records and estimation of environmental and additive and non-additive genetic effects on lactation curve and lactation parameters of crossbred dual purpose cattle

The objectives of this study were to estimate the environmental and additive and non-additive genetic effects on lactation curve and lactation parameters of crosses of Holstein (H), Brahman (B) and Brown Swiss (BS) in Olancho region in Honduras. The data consisted of 54,517 milk yield records from 192 dual-purpose crossbred cows lactating from 2000 to 2005 at the Universidad Nacional de Agricultura de Honduras (UNA). The lactation curve and lactation parameters of interest were the scaling factor to represent yield at the beginning of lactation (a), the factor associated with the inclining (b) and declining (c) slopes of the lactation curves, and the milk yield at initial day of lactation (MY₂₀), peak milk yield (MY_max), day at peak milk yield (t_max), and the total milk yield (TM) per lactation, respectively. The incomplete gamma function (Wood function) was used to estimate lactation curve and lactation parameters from daily milk records of H × B, H × BS and BS × B crossbred cows. The environmental, additive and non-additive genetic effects on lactation curve and lactation parameters were estimated using Dickerson and Kinghorn models. The coefficients of determination of fitness of Wood's function (R²) ranged from 80% to 97% with an average of 93%. The lactation curve of the crossbred cows was similar to those reported for dairy cows grazing in the tropics. Lactation parameters such as MY_max, t_max and TM were significantly (P < 0.05) influenced by environmental sources of variation suggesting the necessity of differential management strategies. The moderate to large positive phenotypic correlation of MY_max and TM indicate that one of the milk yield parameters could be used as a selection criterion to improve either one or both traits. Despite the fact that both genetic models showed similar patterns, the absolute value of the parameters varied. For both models, individual additive genetic breed effect for H breed were significant (P < 0.05) and contributed more to TM than the BS breed. In the Dickerson model, highly positive significant (P < 0.01) effect on TM for H×BS and BS×B crosses was found. The Kinghorn model did not show significant effects of dominance on this parameter. The estimate of recombination effect for all crosses involving B breed were negative and significant (P < 0.05) for positive correlated lactation curve parameters. Although the inclusion of non-additive effects on crossbreeding genetic effects were not all significant for lactation curve and lactation parameters, non-additive effects should be taken into account to improve the Honduran dairy cattle production management.     

Combining genetic test information and correlated phenotypic records for breeding value estimation

The use of marker assisted selection in the beef cattle industry to date has involved using traditional EPD in tandem with molecular test information. In the current study, a multiple-trait simulation was carried out to create a beef cattle data set using genetic parameter estimates from the literature to identify the best procedure for combining both sources of information and to assess the added benefit of the procedure. To reach these objectives, the following simulation/ analysis steps were implemented: (1) varying percentages (100, 5, or 0) of available records for the trait of interest, (2) varying percentages (100, 50, 25, or 0) of animals with molecular information, (3) scenarios where the favorable (F) or the unfavorable (U) allele was more frequent, and (4) analysis of the response due to selection over 5 generations. The data sets included 3 correlated traits in which 2 of them, birth weight and postweaning gain, had complete recording and the availability of records for the third trait (marbling score) varied. It was further assumed that molecular information was available for the third trait for a causative gene that explained 10% of the genetic variation. Estimates of Pearson correlations between true and predicted breeding values for marbling score declined as the amount of information declined, and instances in which the molecular information was recorded were always closer to the true values than in the case in which the molecular information was absent. When the U allele was more frequent, rank correlation estimates were increased among top sires, low accuracy sires, and high accuracy sires by approximately 24.9, 12.1, and 4.7% with limited marbling score records and complete genotyping compared with limited marbling score records and no genotyping. Similar results were seen when the F allele was more frequent. When there was a complete absence of recording for the trait of interest, the same trends in correlations were observed and were lower than when the trait of interest was recorded. Jointly considering molecular and phenotypic information showed a greater long-term response compared with tandem selection, showing that discrimination of candidates for selection based solely on molecular information is not optimal.     

Overview of genetic evaluation in dairy cattle

It is costly and time‐consuming to carry out dairy cattle selection on a large experimental scale. For this reason, sire and cow evaluations are almost exclusively based on field data, which are highly affected by a large array of environmental factors. Therefore, it is crucial to adjust for those environmental effects in order to accurately estimate the genetic merits of sires and cows. Index selection is a simple extension of the ordinary least squares under the assumption that the fixed effects are assumed known without error. The mixed‐model equations (MME) of Henderson provide a simpler alternative to the generalized least squares procedure, which is computationally difficult to apply to large data sets. Solution to the MME yields the best linear unbiased estimator of the fixed effects and the best linear unbiased predictor (BLUP) of the random effects. In an animal breeding situation, the random effects such as sire or animal represent the animal's estimated breeding value, which provides a basis for selection decision. The BLUP procedure under sire model assumes random mating between sires and dams. The genetic evaluation procedure has progressed a long way from the dam‐daughter comparison method to animal model, from single trait to multiple trait analysis, and from lactational to test‐day model, to improve accuracy of evaluations. Multiple‐trait evaluation appears desirable because it takes into account the genetic and environmental variance‐covariance of all traits evaluated. For these reasons, multiple‐trait evaluation would reduce bias from selection and achieve a better accuracy of prediction as compared to single‐trait evaluation. The number of traits included in multiple‐trait evaluation should depend upon the breeding goal. Recent advances in molecular and reproductive technologies have created great potential for quantitative geneticists concerning genetic dissection of quantitative traits, and marker‐assisted genetic evaluation and selection.     

The importance of haplotype length and heritability using genomic selection in dairy cattle

Reliabilities for genomic estimated breeding values (GEBV) were investigated by simulation for a typical dairy cattle breeding setting. Scenarios were simulated with different heritabilites ( h ²) and for different haplotype sizes, and seven generations with only genotypes were generated to investigate reliability of GEBV over time. A genome with 5000 single nucleotide polymorphisms (SNP) at distances of 0.1 cM and 50 quantitative trait loci (QTL) was simulated, and a Bayesian variable selection model was implemented to predict GEBV. Highest reliabilities were obtained for 10 SNP haplotypes. At optimal haplotype size, reliabilities in generation 1 without phenotypes ranged from 0.80 for h ² = 0.02 to 0.93 for h ² = 0.30, and in the seventh generation without phenotypes ranged from 0.69 for h ² = 0.02 to 0.86 for h ² = 0.30. Reliabilities of GEBV were found sufficiently high to implement dairy selection schemes without progeny testing in which case a data time-lag of two to three generations may be present. Reliabilities were also relatively high for low heritable traits, implying that genomic selection could be especially beneficial to improve the selection on, e.g. health and fertility.     

Effects of meloxicam on reproduction parameters in dairy cattle

This study was carried out in dairy cattle with the NSAID meloxicam to investigate possible drug effects on different reproductive parameters as well as on the progeny. Forty-one cows received intravenous injection of either meloxicam (Metacam^® 20 mg/mL solution for injection) or placebo at a dose volume of 7.5 mL/100 kg, corresponding to a dose of 1.5 mg meloxicam/kg, i.e. three times the recommended therapeutic dose. Treatment was performed in each phase of reproduction, i.e. once prior to breeding, twice shortly after breeding, once at the beginning of the second and third trimester of gestation and once at the end of the third trimester of gestation. Offspring of the cows were weighed and clinically examined for vitality at birth and after 28 days. No relevant difference between the meloxicam and control group was found in the reproductive performance of the cows or in the body weight development or vitality of the calves.     

Estimation of genetic parameters for heat stress,including dominance gene effects,on milk yield in Thai Holstein dairy cattle

Heat stress in tropical regions is a major cause that strongly negatively affects to milk production in dairy cattle. Genetic selection for dairy heat tolerance is powerful technique to improve genetic performance. Therefore, the current study aimed to estimate genetic parameters and investigate the threshold point of heat stress for milk yield. Data included 52 701 test‐day milk yield records for the first parity from 6247 Thai Holstein dairy cattle, covering the period 1990 to 2007. The random regression test day model with EM‐REML was used to estimate variance components, genetic parameters and milk production loss. A decline in milk production was found when temperature and humidity index (THI) exceeded a threshold of 74, also it was associated with the high percentage of Holstein genetics. All variance component estimates increased with THI. The estimate of heritability of test‐day milk yield was 0.231. Dominance variance as a proportion to additive variance (0.035) indicated that non‐additive effects might not be of concern for milk genetics studies in Thai Holstein cattle. Correlations between genetic and permanent environmental effects, for regular conditions and due to heat stress, were ? 0.223 and ? 0.521, respectively. The heritability and genetic correlations from this study show that simultaneous selection for milk production and heat tolerance is possible.     

Congenital defects inheritance of AI boars: Genetic parameters and breeding value estimation procedures

Genetic and phenotypic parameters were estimated for the congenital defects atresia ani (AA), intersexuality (IS), cryptorchidism (CR) and scrotal hernia (SH) in Dutch Landrace (DL) and Dutch Yorkshire (DY) pigs, based on data collected in Herdbook defects inventarization during 1976–1984 in the progeny of 194 DL and 294 DY AI boars.Heritabilities were estimated using analysis of variance with correction for categorical data type, and using the proband method derived by Falconer. The results of both methods differed considerably. Using the ANOVA estimates for CR and SH, and the proband estimates for AA and IS, h_HS² ranged between 0.16 and 0.35, and h_FS² between 0.34 and 0.94, indicating large non-additive genetic and maternal effects. Genetic correlation coefficients, estimated by the proband method, generally differed significantly from zero.Frequency distributions of the percentage affected litters per sire were approximated with chi-square functions; for AA and IS, estimated df of these functions were <1, indicating little between-sires variation of this percentage. For CR and SH, estimated df ranged between 1.5 and 4.8, indicating a more quantitative inheritance pattern for these traits.Based on the assumption of a quantitative inheritance pattern for CR and SH, and an oligogeneous one for AA and IS, selection criteria for AI boars were derived following the usual selection index approach, giving higher weights to traits with larger h², larger economical value and taking into account the variation present in the population, as indicated by the chi-square functions.     

Characterisation of the repeat breeding syndrome in Swedish dairy cattle

Repeat breeding (RB), defined as cows failure to conceive from 3 or more regularly spaced services in the absence of detectable abnormalities, is a costly problem for the dairy producer. To elucidate the occurrence of RB in Swedish dairy herds and to identify risk factors of the syndrome totally 57,616 dairy cows in 1,541 herds were investigated based on data from the official Swedish production-, AI- and disease-recording schemes. The characteristics of the RB syndrome were studied on both herd and individual cow level. The effects of risk factors on the herd frequency of RB were studied by logistic regression. A generalised linear mixed model with logit link, and accounting for herd-level variation by including a random effect of herd, was used to study the individual animal risk for RB. The total percentage of RB animals was 10.1% and the median proportion of RB animals in the herds studied was 7.5%. The proportion of RB cows in herds increased with decreased herd sizes with decreased average days from calving to first AI, with increased herd incidence of clinical mastitis, with decreased reproductive disorders, and increased other diseases treated by a veterinarian. On animal level, the risk factors were milk yield, lactation number, difficult calving or dystocia, season at first service, days in milk at first service and veterinary treatment for reproductive disorders before the first service. Cows being an RB animal in the previous lactation had a higher risk of becoming an RB animal also in the present lactation. In conclusion our results show that the repeat breeding syndrome is a multifactorial problem involving a number of extrinsic factors as well as intrinsic factors coupled to the individual animal.     

Estimation of additive, maternal and non-additive genetic effects of preweaning growth traits in a multibreed beef cattle project

Data from purebred and crossbred calves, consisting of Afrikaner (AF), Charolais (CH), Simmental (ST) and Hereford and Aberdeen Angus combined (HA), were analyzed to estimate breed additive effects, breed maternal effects, average individual heterosis and average maternal heterosis. The traits studied were birthweight (BW), weaning weight (WW) and preweaning average daily gain (ADG) (kg). A multiple regression procedure was used for the estimation of these genetic effects and for predictions for breed crosses that were not included in the data set. Crosses containing higher proportions of CH or ST were heavier at birth and weaning than the other crosses and purebreds. The direct effects of BW were negative and significant (P < 0.05), except that of the CH, which was the highest. The regression coefficients were ?24.87, ?18.16, ?22.80 and ?27.02 for AF, CH, ST and HA, respectively. The maternal effects were not significant. Both average individual and average maternal heterosis regression coefficients were also not significant for BW. Regression coefficients of both direct and maternal effects for WW were not significant and were characterized by large standard errors. Average individual heterosis and average maternal heterosis regression coefficients were, however, significant (P < 0.01) and the values were 5.34 and 2.19, respectively. A similar pattern was observed for ADG, except for the regression coefficients of the maternal effects, which were significant, with larger estimates for AF and ST reflecting their superior mothering ability. The values were 0.01, 0.13, 0.13, 0.03; ?0.82, ?0.85, ?0.85, ?0.81; 0.03 and 0.01 for direct effects and maternal effects of AF, CH, ST and HA; and average individual heterosis and average maternal heterosis, respectively. Means and standard errors of purebreds and their F₁ crosses not included in the dataset were predicted.     

Simultaneous Bayesian estimation of genetic parameters for curves of weight,feed intake,and residual feed intake in beef cattle

Rates of gain and feed efficiency are important traits in most breeding programs for growing farm animals. The rate of gain (GAIN) is usually expressed over a certain age period and feed efficiency is often expressed as residual feed intake (RFI), defined as observed feed intake (FI) minus expected feed intake based on live weight (WGT) and GAIN. However, the basic traits recorded are always WGT and FI and other traits are derived from these basic records. The aim of this study was to develop a procedure for simultaneous analysis of the basic records and then derive linear traits related to feed efficiency without retorting to any approximation. A bivariate longitudinal random regression model was employed on 13,791 individual longitudinal records of WGT and FI from 2,827 bulls of six different beef breeds tested for their own performance in the period from 7 to 13 mo of age. Genetic and permanent environmental covariance functions for curves of WGT and FI were estimated using Gibbs sampling. Genetic and permanent covariance functions for curves of GAIN were estimated from the first derivative of the function for WGT and finally the covariance functions were extended to curves for RFI, based on the conditional distribution of FI given WGT and GAIN. Furthermore, the covariance functions were extended to include GAIN and RFI defined over different periods of the performance test. These periods included the whole test period as normally used when predicting breeding values for GAIN and RFI for beef bulls. Based on the presented method, breeding values and genetic parameters for derived traits such as GAIN and RFI defined longitudinally or integrated over (parts of) of the test period can be obtained from a joint analysis of the basic records. The resulting covariance functions for WGT, FI, GAIN, and RFI are usually singular but the method presented here does not suffer from the estimation problems associated with defining these traits individually before the genetic analysis. All the results are thus estimated simultaneously, and the set of parameters is consistent.     

Comparison of models for estimation of genetic parameters for mature weight of Hereford cattle

Genetic parameters of mature weight are needed for effective selection and genetic evaluation. Data for estimating these parameters were collected from 1963 to 1985 and consisted of 32,018 mature weight records of 4,175 Hereford cows that were in one control and three selection lines that had been selected for weaning weight, for yearling weight, or for an index combining yearling weight and muscle score for 22 yr. Several models and subsets of the data were considered. The mature weight records consisted of a maximum of three seasonal weights taken each year, at brand clipping (February and March), before breeding (May and June), and at palpation (August and September). Heritability estimates were high (0.49 to 0.86) for all models considered, which suggests that selection to change mature weight could be effective. The model that best fit the data included maternal genetic and maternal permanent environmental effects in addition to direct genetic and direct permanent environmental effects. Estimates of direct heritability with this model ranged from 0.53 to 0.79, estimates of maternal heritability ranged from 0.09 to 0.21, and estimates of the genetic correlation between direct and maternal effects ranged from -0.16 to -0.67 for subsets of the data based on time of year that mature weight was measured. For the same subsets, estimates of the proportions of variance due to direct permanent environment and maternal permanent environment ranged from 0.00 to 0.09 and 0.00 to 0.06, respectively. Using a similar model that combined all records and included an added fixed effect of season of measurement of mature weight, direct heritability, maternal heritability, genetic correlation between direct and maternal effects, proportion of variance due to direct permanent environmental effects, and proportion of variance due to maternal permanent environmental effects were estimated to be 0.69, 0.13, -0.65, 0.00, and 0.04, respectively. Mature weight is a highly heritable trait that could be included in selection programs and maternal effects should not be ignored when analyzing mature weight data.