Milk production and lactation length in Ankole cattle and Ankole crossbreds in Rwanda

This study assessed daily milk yield (DMY), 100-day (MY100), and 305-day (MY305) milk yield, and lactation length (LL) in purebred Ankole cattle and Ankole crossbreds, and the influence of environmental factors on these traits. Milk yield data were obtained for 865 cows and 1234 lactations and analyzed using a mixed linear model. The overall least squares mean of DMY, MY100, and MY305 across breed groups was 2.7 L (N = 1234, SD = 1.7), 262 L (N = 959, SD = 176), and 759 L (N = 448, SD = 439), respectively, while the average lactation length was 256 days (N = 960, SD = 122). All factors included (breed group, season and year of calving, and parity) were significant for yield traits, except season of calving for MY305. First-parity cows had the lowest milk production, and fourth-parity cows the highest. For all traits, pure Ankole cows had the lowest milk yield. Among the crossbreds, there was no significant difference between Ankole × Friesian, Ankole-Jersey mother × Sahiwal sire, and Ankole-Sahiwal mother × Jersey sire, or between Ankole × Sahiwal and Ankole-Sahiwal mother × Sahiwal sire. It was concluded that Ankole crosses with Friesian or Jersey can be beneficial, even under a management system of limited nutrition as in Rwanda.

     

Production objectives and breeding goals of Sahiwal cattle keepers in Kenya and implications for a breeding programme

The Sahiwal breed has been used for upgrading the East African Zebu (EAZ) for improved milk production and growth performance in the southern rangelands of Kenya. Main users of this breed are Maasai pastoralists. Until now, there has been no deliberate effort to understand why these pastoralists specifically prefer to keep Sahiwal genetic resources as well as which traits are considered important by them and what is the underlying reason for this. However, this information is regarded vital for further development of the breed. A survey was conducted between May and October 2009 among Maasai pastoralists in Kajiado and Narok counties in the Southern part of Kenya, and private ranches and government farms to identify production objectives and breeding goals of Sahiwal cattle producers. Sahiwal genetic resources were mainly kept for domestic milk production and for revenue generation through milk sales and live animals. To a limited extent, they were kept for breeding and also for multiple objectives that included insurance against risks and social functions. Production aims were influenced to varying extents by various household and farmer characteristics. Sahiwal cattle and their crosses were generally perceived to be better with respect to productive traits and fertility traits when compared to the EAZ. However, the EAZ was rated higher with respect to adaptation traits. The breeding objective traits of primary importance were high milk yield and big body size, good reproductive efficiency and relatively good adaptation to local production conditions. Performance and functional traits are important breeding goals that play a major role in fulfilling the multiple production objectives. This forms the basis for the optimisation of a breeding programme for sustainable utilisation to meet the needs of Sahiwal cattle producers.     

Sahiwal cattle in semi-arid Kenya: genetic aspects of growth and survival traits and their relationship to milk production and fertility

The aim of this study was to estimate genetic and phenotypic parameters for growth and survival traits of Sahiwal cattle in Kenya and determine their relationship to milk production and fertility. Performance records of 5,681 animals were obtained from the National Sahiwal Stud and the traits considered were: birth weight (kilogrammes), weaning weight (kilogrammes), pre-weaning average daily gain (grammes per day), post-weaning average daily gain (grammes per day), yearling weight (kilogrammes), mature weight at 36 months (kilogrammes), pre-weaning survival rate (SR), post-weaning survival rate (PSR), lactation milk yield (kilogrammes), age at first calving (days), and calving interval (days). The data was analysed using univariate and bivariate animal model based on restricted maximum likelihood methods, incorporating all known pedigree relationship among animals. The additive direct effects were more pronounced than maternal genetic effects in early and in post-yearling growth performance. The additive genetic variance and heritabilities were low for SR and PSR. The correlation between direct additive genetic and maternal genetic effect were negative for pre-yearling traits. Genetic and phenotypic correlations among growth traits and between growth and milk yield were positive, whilst those between growth and fertility were weak and negative. Correlations between survival and growth were generally low and positive. The estimates obtained in this study provide the necessary technical parameters for evaluating alternative breeding programmes and selection schemes for sustainable improvement of Sahiwal cattle.     

Growth,reproductive, and productive performance of Begait cattle under different herd management systems in northern Ethiopia

The performance of indigenous Begait cattle (498 cows, 284 calves, and 48 heifers) in northern Ethiopia was studied. System of herd management significantly (P?<?0.01) influenced all production traits. Calves in medium-input herds (MIHM) grew faster than those in low-input herds (LIHM), by 232 g/d from birth to 9 months (Gain₁) and by 385 g/d from 9 to 12 months (Gain₂). Cow’s dry period, calving interval (CI), and age at first calving (AFC) were 234, 222, and 343 days shorter for MIHM than for LIHM. Compared with LIHM, cows from MIHM had 74% higher daily milk yield (DMY) and 91% higher lactation milk yield (LMY). Calves born at wet season grew faster by 14 and 10% than those calves born in the dry season at Gain₁ and Gain₂. The subsequent CI of cows calved in the wet season had 77 days shorter, 0.45 kg DMY, and 93 kg LMY increment. The differences between production systems can be attributed to differences in management skills and access to better quality feeds. Technical intervention is needed to ensure provision of balanced rations to exploit the potential productivity of Begait cattle.     

Estimates of genetic parameters for Boran, Friesian, and crosses of Friesian and Jersey with the Boran cattle in the tropical highlands of Ethiopia: milk production traits and cow weight

Breed additive and non‐additive effects plus heritabilities and repeatabilities for milk yield per lactation (LMY), milk yield per day (DMY), lactation length (LL), annual milk yield (AMY), annual milk yield per metabolic body weight (AMYBW) and cow weight at calving (BW) were estimated for 5464 lactation records collected from purebred Boran (B), Friesian (F), and crosses of Friesian and Jersey (J) breeds with the Boran breed raised in the tropical highlands of Ethiopia. Single trait analysis was carried out by using two equivalent repeatability animal models. In the first model the genotype was fitted as a fixed group effect, while in the second model the genotype was substituted by breed additive, heterotic and recombination effects fitted as fixed covariates. Both the F and J breed additive effects, measured as a deviation from the B breed were significant (p < 0.01) for all traits, except for BW of the J. The F and J additive contributions were 2774 ± 81 and 1473 ± 362 kg for LMY, 7.1 ± 0.2 and 4.8 ± 0.8 kg for DMY, 152 ± 7 and 146 ± 31 days for LL, 2345 ± 71 and 1238 ± 319 kg for AMY, 20.6 ± 0.9 and 18.9 ± 4.3 kg for AMYBW, and 140 ± 4 and ?21 ± 22 kg (p > 0.05) for BW. The heterotic contributions to the crossbred performance were also positive and significant (p < 0.01) for all traits. The F₁ heterosis expressed as a deviation from the mid‐parent values were 22 and 66% for LMY, 11 and 20% for DMY, 29 and 29% for LL, 21 and 64% for AMY, 42 and 42% for AMYBW, and 2% (p < 0.05) and 11% for BW for the F × B and J × B crosses, respectively. The recombination effect estimated for the F × B crosses was negative and significant for LMY (?526 ± 192 kg, p < 0.01), DMY (?3.0 ± 0.4 kg, p < 0.001), AMY (?349 ± 174 kg, p < 0.05) and BW (?68 ± 11 kg, p < 0.001). For the J × B crosses the recombination loss was significant and negative only for DMY (?2.2 ± 0.7 kg, p < 0.05) and BW (?33 ± 17 kg, p < 0.05). The direct heritabilities (h²) estimated for LMY, DMY, LL, AMY and AMYBW were 0.24 ± 0.04, 0.19 ± 0.03, 0.13 ± 0.03, 0.23 ± 0.04 and 0.17 ± 0.05, respectively. Based on the genetic parameters estimated, the best breeding strategy to increased milk production under highland Ethiopian conditions is to apply selection on purebred base populations (Boran and Friesian) and then crossing them to produce F₁ dairy cows. However, for breeding decision based on total dairy merit, further investigations are needed for traits such as milk quality, reproduction, longevity and survival.     

Non-lactational traits of importance in dairy cows and applications for emerging biotechnologies

Dairy cattle have traditionally been selected for their ability to produce milk and milk components. The traditional single-minded approach to selection of dairy cattle has now changed and secondary traits are being included in selection indices by decreasing the emphasis on production. Greater emphasis on non-production traits reflects the industry's desire for functional dairy cattle. Six broad categories of non-lactational traits are discussed in this review. They are: type; growth, body size and composition; efficiency of feed utilisation; disease resistance, e.g. udder health as measured by somatic cell score; reproduction; and management. Most of these traits can be found within selection indices worldwide, although relative emphasis varies.

The non-lactational traits mentioned above are quantitative, meaning that the phenotype in the whole animal represents the sum of lesser traits that cannot be easily measured. The physiological mechanisms that underlie quantitative traits are extremely complex. Genetic selection can be applied to quantitative traits but it is difficult to link successful genetic selection with the underlying physiological mechanisms. The importance that the bovine genome sequence will play in the future of the genetics of dairy cattle cannot be understated. Completing the bovine genome sequence is the first step towards modernising our approach to the genetics of dairy cattle.

Finding genes in the genome is difficult and scanning billions of base pairs of DNA is an imperfect task. The function of most genes is either unknown or incompletely understood. Combining all of the information into a useable format is known as bioinformatics. At the present time, our capacity to generate information is great but our capacity to understand the information is small. The important information resides within subtle changes in gene expression and within the cumulative effect that these have.

Traditional methods of genetic selection in dairy cattle will be used for the foreseeable future. Most non-lactational traits are heritable and will be included in selection indices if the traits have value. The long-term prognosis for genome science is good but advances will take time. Genetic selection in the genome era will be different because DNA sequence analysis may replace traditional methods of genetic selection.     

Non-lactational traits of importance in dairy cows and applications for emerging biotechnologies

Dairy cattle have traditionally been selected for their ability to produce milk and milk components. The traditional single-minded approach to selection of dairy cattle has now changed and secondary traits are being included in selection indices by decreasing the emphasis on production. Greater emphasis on non-production traits reflects the industry's desire for functional dairy cattle. Six broad categories of non-lactational traits are discussed in this review. They are: type; growth, body size and composition; efficiency of feed utilisation; disease resistance, e.g. udder health as measured by somatic cell score; reproduction; and management. Most of these traits can be found within selection indices worldwide, although relative emphasis varies. The non-lactational traits mentioned above are quantitative, meaning that the phenotype in the whole animal represents the sum of lesser traits that cannot be easily measured. The physiological mechanisms that underlie quantitative traits are extremely complex. Genetic selection can be applied to quantitative traits but it is difficult to link successful genetic selection with the underlying physiological mechanisms. The importance that the bovine genome sequence will play in the future of the genetics of dairy cattle cannot be understated. Completing the bovine genome sequence is the first step towards modernising our approach to the genetics of dairy cattle. Finding genes in the genome is difficult and scanning billions of base pairs of DNA is an imperfect task. The function of most genes is either unknown or incompletely understood. Combining all of the information into a useable format is known as bioinformatics. At the present time, our capacity to generate information is great but our capacity to understand the information is small. The important information resides within subtle changes in gene expression and within the cumulative effect that these have. Traditional methods of genetic selection in dairy cattle will be used for the foreseeable future. Most non-lactational traits are heritable and will be included in selection indices if the traits have value. The long-term prognosis for genome science is good but advances will take time. Genetic selection in the genome era will be different because DNA sequence analysis may replace traditional methods of genetic selection.     

Genetic analysis of days open in beef cattle

The aim of this work was to analyse the genetic parameters affecting days open (DO) in beef cattle to evaluate its potential as criterion of selection. The present study characterises DO as a trait with considerable genetic variability, relative to that usually found for reproduction traits, especially for heifers and second calving cows. The estimates of heritability for the trait ranged from 0.091 for cows with 10 or more calvings to 0.197 for second calving cows. The genetic correlations estimated for DO in different parities are situated between 0.9 and 1, showing that the genes affecting the trait are substantially the same across parities of the dam. A substantial permanent environment (around 9%) seems to affect DO performance. Permanent environmental factors seem to be especially important in younger cows. Genetic correlation between DO and calving interval was positive and very high (1.0), while those between DO and gestation length and calving date were negative from low to moderate (−0.089 and −0.308, respectively). DO can be used in improvement programs of beef cattle as an early indicator of reproductive performance of the cow.     

Trends in the reproductive performance of Holstein dairy cows in Iran

The study was undertaken to determine the trends in the reproductive performance of Holstein dairy cows in Iran during 1994 to 2008. Reproductive performance data for 528,034 lactations of 246,132 cows in 1,822 Holstein dairy herds of Iran were used. The potential effect of calving season, herd, parity, calving year, as well as herd size and 305-day milk production on reproductive performance traits was investigated using multiple regression models. The least squares means of age at first calving decreased by 3.1 (±0.06) days per year from 806.5 (±96.3) days in 1994 to 788 (±89.9) days in 2008. The least squares means of calving interval increased 1.02 (±0.03) days per year from 394.1 (±65) days in 1994 to 413.2 (±81) days in 2008. Greater 305-day milk production was associated with an average increase of 6.55 (±0.08) days in calving interval per 1,000-kg increase in milk yield. Larger herd size was associated with an average decrease of 0.22 (±0.02) days in calving interval per 50 cows per herd. The mean number of days dry was 88.6 (±51.3) days and increased by 0.82 (±0.02) days per year. In conclusion, reproductive performance in Holstein dairy herds has generally decreased, whereas herd size and milk production have increased over time. Producers may make significant improvements in herd reproduction by reviewing management strategies including the sire selection, reproductive management, inseminator training and techniques, and improved estrous detection. Moreover, it may be advisable for the fertility traits to be included in the genetic selection indices to reduce the rate of reproductive decline.     

Enhancing milk and fertility performances using selection index developed for Indian Murrah buffaloes

Selection for genetically superior Murrah buffaloes under Network Project on Buffalo Improvement, India, is presently based on milk yield, and it was observed that even in the absence of any direct selection pressure applied on fertility, there has been a downward trend in fertility associated with the selection for milk yield. The aim of the study was to develop selection indices which include fertility besides milk yield in Murrah buffaloes. Data pertaining to 1,224 lactation records spread over a period of 19 years were recorded and analyzed in the study. The negative association of pregnancy rate (fertility) with a 305-day milk yield (?0.08?±?0.04) and wet average (?0.12?±?0.02) indicated the importance of incorporating fertility trait in the construction of selection index. Four types of selection indices were constructed and evaluated. Two indices were developed using expected producing ability 305-days milk yield (EPAMY) with 6.5 and 4 % fat in milk along with expected fertilizing ability (EFA). The other two indices developed consist of expected producing ability wet average (EPA WA) and EFA. The index involving (EPA WA and EFA) was found to be a more effective selection criterion in our herd, as the accuracy of index was more (0.61), in comparison to the index involving EPA MY and EFA. The robustness of selection index was assessed by increasing the relative economic values of included traits by 25 and 50 %, and accuracy of the index remains almost stable without much change. The developed selection strategy involving EPA WA and EFA should be considered for the genetic evaluation of Murrah buffaloes, as it has a potential for maximizing the lifetime reproduction and production performances of the breed.     

Effect of polymorphisms at the STAT5A and FGF2 gene loci on reproduction, milk yield and lameness of Holstein cows

The objective of this study was to investigate the association of polymorphisms at the STAT5A and FGF2 gene loci with fertility, lactation milk yield and lameness in dairy cattle. Five hundred and eighteen primiparous Holstein cows were included in the study. Several reproductive traits were considered including conception rate (0/1) at first insemination, conception rate (0/1) in a 305-day lactation, number of inseminations per conception, interval (days) from calving to conception for cows that conceived in the first 305 days of lactation and age at first calving. Milk yield and lameness incidence were also recorded. Genotyping was performed using PCR-RFLP. The effect of allele substitution at each gene locus on reproductive traits, milk yield and lameness was assessed with single-trait mixed linear models. No significant associations were found between reproduction traits and any of the studied polymorphisms, apart from age at first calving, for which STAT5A polymorphism had a suggestive effect (P = 0.077). In addition, no significant effect of any polymorphism on lameness was found. Replacement of the C by G allele at the STAT5A locus was associated with a significant (P < 0.05) increase in lactation milk yield, suggesting that this locus could be considered in gene assisted selection for the genetic improvement of milk production.     

The benefit of native uniqueness in a local red cattle breed from Northern Germany

During last decades, native uniqueness decreased in local livestock breeds due to the introgression of high‐yielding breeds. Recovery of native uniqueness became important because of conservation aspects regarding native genetic diversity and native traits. Thereby the expectation exists, that the relation between native uniqueness and genetic gain is contradictory. The aim of this study was to explore the influence of native uniqueness on performance traits and the total merit index in a local red cattle breed from Northern Germany. Data contained a pedigree file of 178,255 Red Dual‐Purpose cattle, 809 target genotypes and 3,581 reference genotypes from introgressed breeds. Native genetic contributions were tested for correlation with performance traits of milk yield, longevity, foundation, somatic cells, fertility and maternal calving and the total merit index. The study revealed that native uniqueness is favourably related to longevity (0.16), foundation (0.23), and somatic cells (0.08), and the total merit index (0.10). Selection on native uniqueness could probably lead to an increased longevity, udder health and genetic gain of the Red Dual‐Purpose cattle. Moreover, it was shown that the Red Dual‐Purpose cattle was not upgraded through introgression of high‐yielding breeds.     

Milk yield and lactation length of Ghana Sanga and its crosses with the Friesian Raised under agropastoral system

Milk yield traits and lactation length of two breeds of cattle raised on natural pasture with little or no supplementation were assessed. A total of 42 573 daily milk records on 98 Friesian-Sanga cows collected over a period of 10 years and 17 790 daily milk records on 72 Sanga cows spanning a 6-year period were used in the study. Traits examined for each breed were daily milk yield, total milk yield, 305-day milk yield, 305-day milk yield/day and lactation length. Friesian-Sanga cows outperformed their Sanga counterparts in all traits studied. Friesian-Sanga cows had an average daily milk yield of 1.35?±?0.00 kg; average total milk yield of 266?±?12 kg; average 305-day milk yield of 339?±?10 kg; average 305-day milk yield/ day of 1.11?±?0.03 kg and mean lactation length of 201.1?±?6.9 days. Average values for Sanga cows were 1.01?±?0.00 kg as daily milk yield; 162?±?12 kg as total milk yield; 244?±?10 kg as 305-day milk yield; 0.80?±?0.03 kg as 305-day milk yield/day. Mean lactation length for Sanga cows was 164.1?±?9.4 days. Season of calving significantly (P?<?0.05) influenced daily milk yield of Friesian-Sanga cows and all traits of Sanga cows with animals calving in the major rainy season surpassing those that calved in the minor and dry seasons. Daily milk yield for both Friesian-Sanga and Sanga cows was significantly (P?<?0.05) influenced by season of lactation. Daily milk yield gradually declined from second parity towards the sixth parity for Friesian-Sanga cows. A gradual increase in daily milk yield from first to third parity was observed in Sanga cows. Year of calving significantly influenced all traits for both breeds. Genetic improvement in milk yield traits and lactation length is achievable for both breeds of cattle as co-efficient of variation of traits were moderate to high.     

Effects of bovine leukemia virus infection on production and reproduction in dairy cattle.

The purpose of this study was to determine the effects of bovine leukemia virus (BLV) infection on production, reproduction and longevity in dairy cattle. The study population was a commercial Holstein dairy herd of approximately 400 milking cows. Cattle were tested for antibodies to BLV at least annually for three years and when culled. Four groups of culled cows were compared: seronegative cows (n = 79), seropositive cows without lymphocytosis (n = 176), seropositive cows with lymphocytosis (> or = 9,000 lymphocytes/microliter) (n = 74), and seropositive cows with lymphosarcoma (n = 29). Seropositive groups of cows were bred more times and had longer calving intervals than seronegative cows. The seropositive groups had greater 305-day ME (mature equivalent) FCM (3.5% fat-corrected milk) per lactation and were older when culled than seronegative cows. However, the percent fat per lactation was greater in seronegative cows. In the last complete lactation, differences in 305-day ME FCM, days open and cull age between groups were reduced and none were significant (p > 0.05). In the cull lactation, only cows with lymphocytosis had reduced milk production relative to seronegative cows, although this difference was not significant. After adjustment for initial production and reproductive values, only seropositive nonlymphocytotic cows were culled at a significantly older age than seronegative cattle. Lymphocytotic cows were culled four months younger on average than nonlymphocytotic seropositive cows. Hence, BLV infected cows had greater milk production on average than uninfected cows. Adverse effects of BLV infection were primarily limited to lymphocytotic cows which were culled earlier and had reduced milk production in the cull lactation.     

Association analysis of novel polymorphisms in 2′, 5′‐oligoadenylate synthetase gene with reproductive traits in indigenous and cross‐bred cattle of Indian Origin

2′, 5′‐Oligoadenylate synthetases (OAS) are important components of an interferon‐mediated antiviral pathway. No polymorphisms in exonic regions of bovine OAS1 gene have been identified and associated with reproduction traits. The objective of the study was to detect and evaluate the effects of mutations in exonic region of bovine OAS1 gene with reproduction traits in cattle. DNA samples collected from 250 individual cows of two Indian dairy breeds (Sahiwal and Frieswal) of cattle were used in the study. The genetic variants of the OAS1 gene were identified with polymerase chain reaction–single‐strand conformation polymorphism (PCR‐SSCP) and sequence analysis using seven set of primer pairs. The PCR‐SSCP analysis revealed polymorphism in the fragments comprising of exon 2, exon 5 and first fragment of exon 6 while the fragments of exons 1, 3, 4 and second fragment of exon 6 were monomorphic in Sahiwal and Frieswal cattle. The mutations in the amplified region comprising of exon 2 were found to have significant association with age at first breeding and calving, service period, dry period and pregnancy rate. Significant associations were found between SNPs in the exon 5 and service and dry periods of the animal, whereas the genetic variants in the first fragment of the exon 6 showed significant association with age at first breeding and calving. To our knowledge, this study demonstrated for the first time that the polymorphisms in OAS1 gene were associated with reproductive traits and it can be chosen as a candidate gene for improvement of reproductive performance of cattle.     

中国荷斯坦牛乳房性状、体型总分与产奶性状的相关分析

研究利用武汉市58头公牛的971头女儿2006—2007年间的体型性状鉴定记录及2001—2007年间的生产性能测定记录,配合动物模型,采用REML方法进行参数估计,探讨了乳房性状、体型总分与产奶性状之间的关系。结果表明:乳房性状与产奶性状之间的表型相关较小。后乳房宽度与产奶性状之间存在强的遗传正相关(0.44～0.89)。后乳房高度与305 d产奶量(0.27)、305 d乳脂量(0.16)存在遗传正相关,而与305 d乳蛋白量(-0.32)存在遗传负相关。前乳房附着与产奶性状基本不存在相关。悬韧带与305 d产奶量存在遗传正相关(0.79)。乳房深度与305 d产奶量存在遗传负相关(-0.20)。体型总分与305 d产奶量、305 d乳脂量、305 d乳蛋白量存在较强的遗传正相关,故加强乳房性状和体型总分的选择对提高奶牛的生产性能有益。     

奶牛外貌评分与产奶量相关性研究

某奶牛场随机取30头奶牛,测定其305d产奶量及10个体型外貌评分性状,计算产奶量与体型性状之间的相关系数,求得产奶量的各自通径系数,研究奶牛10个体型性状与生产效率性状之间的关系。结果表明,整体评分与305d产奶量之间存在弱正相关（P〉0．05）;10个评分性状中,后乳房高度和宽度与305d产奶量呈极显著相关（P〈0．01）。乳房中隔和乳房深度与305d产奶量呈显著相关（P〈0．05）。整体外貌评分、后乳房宽度、乳房中隔越高则产奶量也越高,后乳房高度和乳房中隔是对产奶量起主要作用的性状。     

The economic value of days open in Holstein cows in Japan based on simulated changes in conception rate

Increasing herd‐life length and culling parity with increasing conception rate (CR) is necessary to increase lifetime profit from dairy cow production. Economic values of days open (DO) were determined by calculating changes in fertility traits, herd‐life length, and milk yield when the simulated CR were changed in increments of 1% from ?5% to 5% from the basal levels, which were obtained for Hokkaido and regions other than Hokkaido separately. When CR increased, number of artificial inseminations, DO, and milking length decreased. Furthermore, culling parity, and annual milk yield increased. Herd‐life length increased in Hokkaido and decreased in the other regions. The economic values of CR were 1,623.8 to 946.8 yen and of DO were 857.4 to 399.0 yen. Relative economic values of milk yield to days open per genetic standard deviation were higher in the other regions than in Hokkaido where the economic effect of selection for DO was expected to be equal to selection for 305‐day milk yield and herd life. If the survival rate of multipara cows in the other regions increases, then the economic value of DO would similarly increase in Hokkaido.     

Environmental factors affecting milk,fat and protein yields in Jersey cattle in Zimbabwe

A study was carried out to establish the factors affecting milk, butterfat and protein yields in Zimbabwean Jersey cattle. A total of 10,986 unedited 305-day lactation records were obtained from Zimbabwe Livestock Identification Trust containing 25 herds, with cows calving in the period 1996–2008. The general linear model procedure of the Statistical Analysis Systems version 9.1.3 was used to determine the environmental factors. Herd-year-season, calving interval, days dry and both the linear and quadratic effects of age at calving fitted as covariates significantly (P < 0.0001) affected the milk, fat and protein yields. Herd-year-season accounted for 36%, 36% and 35% to the total variation in milk, fat and protein yields, respectively. Milk, fat and protein yields increased with an increase in calving interval. The optimum dry period for milk, fat and protein yields obtained was 60–75 days dry. The relationship between the production traits and age at calving was both linear and quadratic, implying that milk, fat and protein yields increase with the age of the animal. It is thus necessary to preadjust data for these environmental factors when carrying out genetic evaluations of production traits in dairy cattle.     

产犊季节对荷斯坦牛第一胎泌乳性能的影响

[目的]为了研究不同产犊季节对荷斯坦奶牛第一胎泌乳性能的影响,以便为长江中下游地区荷斯坦奶牛合理安排配种时间提供科学依据。[方法]利用海丰奶牛场有限公司2009年引进2480头澳系进口荷斯坦牛产犊季节及其第一胎泌乳性能的数据,分析不同产犊季节对第一胎泌乳天数、全泌乳期实际产奶量、305d校正奶量、305d脂肪产量和305d蛋白产量的影响。[结果]表明:不同产犊季节对第一胎泌乳天数和全泌乳期产奶量影响极显著(P0.01),显著影响305天脂肪产量(0.01P0.05),春季产犊的奶牛泌乳天数最长(358±10d),而冬季产犊的奶牛泌乳天数最短(299±18d),春季与夏季产犊奶牛的全泌乳期产奶量显著高于秋季、冬季产犊奶牛(P0.05),夏季产犊奶牛305d脂肪产量最高。[结论]综合各产犊季节样本量及相应泌乳性能,认为该场澳系进口荷斯坦牛最适宜产犊季节为夏末秋初,此时泌乳性能最好。该结果对同类地区引进澳系进口荷斯坦牛繁殖与生产管理有借鉴作用。