Genetic Improvement Of Milk Yield Research Articles

Cross breeding of Saudi Aradi with Damascus goats breeds for genetic improvement in the milk yield and composition

The aim of the present study was to evaluate the effects of crossing Saudi Aradi with Damascus goat breeds in improvement milk yield and composition. A total number of 366 healthy goats (150 Aradi goats, 157 Damascus goats and 59 their cross) was included in the study. Does were randomly divided into two groups and each group, Aradi does were subdivided into two subgroups; the first one was inseminated artificially from semen of bucks of the same breed and the second group was inseminated artificially from semen of Damascus breed bucks. Data were recorded for all animals during two seasons (S1, winter/Autumn, S2, spring/summer). Effects of the type of birth, breed, season, year and number of kids on milk yield (MY), fat% (F%) and protein% (P%) were statistically analyzed. The percentages of variation for milk yield and fat were moderate (38.93 % and 39.36%, respectively) but the differences between minimum and maximum were high ranged from 90.54 to 514.9 kg for milk yield and from 0.580 to 8.259% for fat%, while these variations for protein% were low (12.43%) but the difference between minimum and maximum were high ranged from 2.133 to 5.280%. The breed had a higher significant effect on milk yield and fat% (P≤ 0.01) and significant effect on protein% (P≤ 0.05). Crosses had higher protein% than Damascus and Aradi goats breeds. There was significant effect of the year on milk yield, fat% and protein% (highest level of milk yield, P≤ 0.05 and protein%, P≤ 0.01 recorded during 2006). Number of kids had highly significant effect (P≤ 0.01) on milk yield, protein and fat%. There were significant correlations among total milk yield, protein and fat% (P≤ 0.01). In conclusions, milk yield traits in Aradi goats were the lowest, so crossing with Damascus goats is the best program for upgrading and genetic improvement of milk yield in that breed.

Genetic and genomic analyses underpin the feasibility of concomitant genetic improvement of milk yield and mastitis resistance in dairy sheep.

Milk yield is the most important dairy sheep trait and constitutes the key genetic improvement goal via selective breeding. Mastitis is one of the most prevalent diseases, significantly impacting on animal welfare, milk yield and quality, while incurring substantial costs. Our objectives were to determine the feasibility of a concomitant genetic improvement programme for enhanced milk production and resistance to mastitis. Individual records for milk yield, and four mastitis-related traits (milk somatic cell count, California Mastitis Test score, total viable bacterial count in milk and clinical mastitis presence) were collected monthly throughout lactation for 609 ewes of the Chios breed. All ewes were genotyped with a mastitis specific custom-made 960 single nucleotide polymorphism (SNP) array. We performed targeted genomic association studies, (co)variance component estimation and pathway enrichment analysis, and characterised gene expression levels and the extent of allelic expression imbalance. Presence of heritable variation for milk yield was confirmed. There was no significant genetic correlation between milk yield and mastitis traits. Environmental factors appeared to favour both milk production and udder health. There were no overlapping of SNPs associated with mastitis resistance and milk yield in Chios sheep. Furthermore, four distinct Quantitative Trait Loci (QTLs) affecting milk yield were detected on chromosomes 2, 12, 16 and 19, in locations other than those previously identified to affect mastitis resistance. Five genes (DNAJA1, GHR, LYPLA1, NUP35 and OXCT1) located within the QTL regions were highly expressed in both the mammary gland and milk transcriptome, suggesting involvement in milk synthesis and production. Furthermore, the expression of two of these genes (NUP35 and OXCT1) was enriched in immune tissues implying a potentially pleiotropic effect or likely role in milk production during udder infection, which needs to be further elucidated in future studies. In conclusion, the absence of genetic antagonism between milk yield and mastitis resistance suggests that simultaneous genetic improvement of both traits be achievable.

Genetic studies on production and reproduction traits of Ongole cattle at organized farms

The study was undertaken to assess the genetic and non genetic factors affecting the productive and reproductive performance of Ongole cattle. Record (3,070) of calf weight and lactation records (2,900) of 729 Ongole cows, maintained at livestock farms (LRS, Lam, Guntur; LRS, Mahanandi; GCBF, Chadalwada; and GLF, Chintaldevi) in Andhra Pradesh, daughter of 67 bulls during 25 years from 1985 to 2009 were used in the analysis. The male calves were heavier than female calves. Low heritability estimated for lactation milk yield and reproductive traits indicated that there is less additive genetic variance in these traits and individual selection will not be helpful for improving them. Also, high genetic correlation between lactation milk yield and peak yield indicated that selection for peak yield may bring reasonable genetic improvement in milk yield of Ongole cows. The results also revealed there is a further scope for improvement in milk production and reproductive performance of the animals through better feeding and management practices.

Phenotypic and genetic parameters for milk yield in traditional Nublang cattle (Bos indicus) of Bhutan

SummaryThe Nublang is a unique dual-purpose breed ofBos indicuscattle found in Bhutan. They have been crossed with Mithun (Bos frontalis) andBos taurusbreeds in an effort to improve milk production leading to a decline in the population of purebred Nublang. An alternative to crossbreeding would be the genetic improvement of milk yield within purebred Nublang, thus allowing conservation and sustainable utilization of the pure breed. It is important to measure the genetic variability (heritability) of milk yield to assess the potential for genetic improvement within Nublang. Therefore this study estimated phenotypic and genetic parameters of milk yield using 2 052 test day milk yields from 66 cows recorded from 1997 to 2013 in the National Nublang Farm, Tashiyangphu. The average daily milk yield (DMY) was 2.12 ± 0.7 litres (N 2 052, range: 0.3–5.0 L, CV: 34 percent). Parity, month in milk and year all had a significant effect on DMY (P< 0.05). The average lactation milk yield (LMY) was 519.2 ± 151 L (N: 261, range: 115–881.7, CV: 29.1 percent) and average lactation length was 239 days. LMY was significantly influenced by parity (P< 0.05) and season of calving. The heritability of DMY and LMY was 0.22 ± 0.16 and 0.13 ± 0.20, respectively. The repeatability estimates were 0.45 ± 0.05 and 0.49 ± 0.08 for DMY and LMY, respectively. Overall the heritability and repeatability estimates of milk yields indicate potential for genetic improvement of milk yield in Nublang cattle through selection. However, it is recommended that a larger dataset is generated to enable more precise estimates of genetic parameters.

Breeding Strategies for Genetic Improvement of Dairy Cattle in Zimbabwe. 1. Genetic Evaluation

Strategies of selection within local populations and of importation of semen and embryos from countries with higher genetic merit are evaluated for genetic improvement of milk yield in Zimbabwe. Local programs are progeny testing in a closed population, progeny testing combined with semen importation to sire 30% of cows, progeny testing with foreign sires as sires of bulls, and a closed nucleus selection scheme using embryo transfer started from elite imported stock. Strategies based on continuous importation are imported semen for 30, 50, or 100% of cows and semen from elite foreign bulls used on local elite cows and bulls from elite imported embryos. Gene flow methods were used to estimate the genetic means for the strategies. In predicted genetic response at 25 yr, continuous importation of all semen from the superior exporting country ranks first; second is the importation of elite embryos to provide bulls for AI; and third is the closed nucleus scheme using embryo transfer. Schemes involving importation of semen to breed bulls with local progeny testing are intermediate, and the lowest responses come from semen imported to breed cows and from the closed local progeny-testing scheme. Ranking of the strategies is influenced by the genetic correlation of performance and by the initial genetic difference between Zimbabwe and the exporting country.

Stochastic Modeling of Multiple Ovulation and Embryo Transfer Breeding Schemes in Small Closed Dairy Cattle Populations

Genetic changes and genetic drift in three small closed dairy cattle populations were examined with a stochastic simulation model. Multiple ovulation and embryo transfer and AI techniques were simulated in three populations, two with 88 breeding females each and one with 352 breeding females. The selection goal was to maximize genetic improvement in milk yield. The reduction in genetic variation due to inbreeding and linkage disequilibrium was accounted for in the simulation. Strict restriction against inbred mating slowed genetic progress significantly in the small population but would not be consequential in the larger population. However, allowing inbred mating in the smaller population caused a rapid accumulation of inbreeding. Linkage disequilibrium was as important as inbreeding in reducing genetic variation. Genetic drift variance was much smaller in the larger population.

SELECTION LIMITS: HAVE THEY BEEN REACHED WITH THE DAIRY COW?

Genetic theory suggests that at some point genetic progress for milk production might plateau either through exhaustion of genetic variability or through development of antagonistic genetic relationships between milk yield and components of fitness. Although there have been no long-term selection experiments with dairy cattle, empirical evidence from field data indicates that selection limits for increased milk production have not been reached nor will they be in the foreseeable future. The rate of genetic improvement in milk yield is accelerating. Rather than witnessing a decline in genetic variability, as genetic theory would indicate, we seem to be experiencing an increase in genetic variability as production levels increase with time which is likely due to improved management allowing for greater expression of genetic variability. There is some evidence of genetic antagonisms between milk yield and fitness traits, fertility and health measures in particular, and this could impose a limit to selection for increased milk production. The solution to this problem is probably through improved management of high producing cows, to reduce stress associated with high production. Key words: Dairy cattle, selection, genetic variation

Selection of dairy bulls on half-sister records

SUMMARYA scheme is described for the genetic improvement of milk yield in a large population of dairy cows, based on half-sister selection of young bulls, as an alternative to the normal procedure of progeny testing. The results indicate that the suggested scheme would lead t o an eventual rate of genetic progress very similar to the progeny testing scheme. However, the annual cost of the new scheme is less than a progeny testing scheme, largely because the ‘laying off’ of candidate bulls, to await selection, is completely eliminated. In addition, improvement of the dairy cows shows up sooner in the new scheme; by the 10th year from the start the cumulative genetic improvement is four times greater than for progeny testing.

Potential of Deshi Cattle of lndia for Dairy Production

There were 1,405 lactation records of 336 cows at the Central Livestock Research-cum-Breeding Station, Haringhata, India from 1958 to 1968 used to estimate the potential dairy merit of Deshi cattle. This breed is native to northeast India and one of the smallest breeds in India (mature females 200kg and males 250kg). Averages and standard deviations for milk yield (exclusive of that suckled), age of first calving, calving interval, lactation length, days open, and days dry were 412±178kg, 44.5±6.8 months, 419±90 days, 264±81 days, 135±86 days, and 139 ± 80 days. Mortality, culling, and retention rates for females from birth to first calving were 24, 27, and 49%. Lactation number, season of calving, and death of calf early in lactation had significant effects on milk yield. Repeatabilities of milk yield, lactation length, calving interval, dry period, and days open were .42, .19, .21, .03, and .23 with corresponding heritabilities .64, .19, .09, .19, and .27. Heritability for age of first calving was .84. Confounding by some environmental effects probably biased heritability estimates upward. Potential genetic improvement of milk yield by mass selection was estimated at 8% per year. Contemporary Jersey×Deshi crosses exceeded Deshi for milk yield, age of first calving, lactation length, calving interval, and days open by ×923kg, −15 months, +41, −84, and −96 days. Atleast one generation of crossing with European breeds is recommended over mass selection of Deshi.

Genetic parameters for test-day milk yield in tropical Holstein Friesian cattle fitting a multiple-lactation random regression animal model

Accurate estimates of genetic parameters are essential for genetic improvement of milk yield in dairy cattle and for setting up breeding programmes. Estimates of genetic parameters from test-day models, particularly for Holstein Friesian cattle maintained in tropical environments, are scant in the literature. The objective of this study was therefore to estimate genetic parameters for milk yield by fitting a multiple-lactation random regression animal model (RRM) based on data from Ethiopian Holstein Friesian herds. Data were used from the first three lactations of cows that calved between 1997 and 2013. The data comprised 13 421 test-day milk yield records from 800 cows from two large dairy herds. Variance components were estimated using the average information restricted maximum likelihood method fitting an RRM. Heritability estimates for first, second, and third lactations ranged from 0.20 to 0.26, 0.15 to 0.27, and 0.17 to 0.28, respectively. Heritability estimates ranging from 0.15 to 0.28 indicate that effective genetic improvement should be accompanied by a corresponding improvement of the production environment. Across-lactation genetic correlations between first and second, second and third, and first and third lactations, expressed on a 305-day yield basis, were 0.88, 0.83, and 0.70, respectively. These genetic correlations, less than or equal to 0.88, indicate that different lactations are different traits. For an accurate evaluation of the genetic merit of animals for milk yield, lactations should be treated as different, but correlated traits in a multiple-lactation analysis.Keywords: Genetic correlation, heritability, Legendre polynomial, test-day model

Genetic improvement in milk yield in Egyptian Buffaloes

Genetic improvement in milk yield in Egyptian Buffaloes

Environmental and Genetic Factors Affecting Milk Production of Butana Cattle in the Sudan

Summary A study was made of the production records of 353 Butana cows with 1,311 calvings during the years 1943–57 in a governmental dairy farm herd on the north of Atbara, Northern Province, Sudan. Prom the performance records of this herd, it was found that (a) heifers averaged 44 months old at first calving, (b) the average interval between consecutive calvings was 416 days, and (c) the average milk yield in 253 days was 3,129 lb, with a standard deviation of 1,709 lb. The records also showed highly significant differences between all production traits at different years. No real differences were evident in milk yield records due to month of calving or age of cows in lactation. Based on reported data, repeatability estimates of single-record milk yield, calving intervals, lactation periods, and dry periods were: 0.415±0.037, 0.111±0.039, 0.415±0.043, and 0.221±0.037, respectively. Heritability of a single-record milk yield was estimated as 0.278±0.232 and of two records as 0.302±0.286. Further statistical analysis showed that the total generation length was 25.87 yr, and it is estimated that the annual genetic improvement in milk yield has amounted to about 0.7% of the herd average. Most of this improvement has been brought about by the selection of the sires used.

Environmental and genetic factors affecting milk production of Butana cattle in the Sudan

Summary A study was made of the production records of 353 Butana cows with 1,311 calvings during the years 1943–57 in a governmental dairy farm herd on the north of Atbara, Northern Province, Sudan. Prom the performance records of this herd, it was found that (a) heifers averaged 44 months old at first calving, (b) the average interval between consecutive calvings was 416 days, and (c) the average milk yield in 253 days was 3,129 lb, with a standard deviation of 1,709 lb. The records also showed highly significant differences between all production traits at different years. No real differences were evident in milk yield records due to month of calving or age of cows in lactation. Based on reported data, repeatability estimates of single-record milk yield, calving intervals, lactation periods, and dry periods were: 0.415±0.037, 0.111±0.039, 0.415±0.043, and 0.221±0.037, respectively. Heritability of a single-record milk yield was estimated as 0.278±0.232 and of two records as 0.302±0.286. Further statistical analysis showed that the total generation length was 25.87 yr, and it is estimated that the annual genetic improvement in milk yield has amounted to about 0.7% of the herd average. Most of this improvement has been brought about by the selection of the sires used.

An analysis of the Entebbe herd of Nganda cattle in Uganda

In the herd of Nganda cattle at the Government Livestock Experiment Station, Entebbe, Uganda, it was found that of the known environmental factors affecting milk production, the more important ones were age (in lactations) and length of the calving interval preceding the second and third lactations. The correlations between performance in different lactations of the same animal were high for lactation milk yield (0·73) and average daily milk yield (0·62) and low for calving interval (0·21) and dry period (0·15). The repeatability of lactation length was intermediate (0·42). The heritability values were around 0·3 for the weight measurements, around 0·2 for yield characteristics and around 0·1 for length of lactation and age at first calving.The sires used in the breeding programme at Entebbe made little impact on production performance in the herd. The estimated genetic improvement in milk yield through selection of dams of cows was also low. It is argued from comparison with results from other parts of the tropics that superior genotypes for milk production are difficult to come by among indigenous cattle in these areas and that we should therefore look for other opportunities and methods to move ahead faster in the future.

Population and Production Characteristics of Red Sindhi Cattle in Ceylon

Summary The mechanism of population changes in the 16-year history of a large herd of Red Sindhi cattle in Ceylon indicates that there is a considerable reserve of fecundity in these animals that could be utilized to enable the population to double itself, if necessary, every 8 years. This would involve increasing the rearing proportion to 0.33 and the average reproductive life to five lactations and keeping down mortality rates at 20%. The prevailing generation interval is about 6 years. Analyses of the production statistics of the herd show that sufficient variability exists in regard to most characters affecting milk production to warrant the possibility of a reasonably rapid advance in production in future years. Such improvement appears possible in the following directions: reduction of age at first calving, shortening of calving intervals and dry periods, and increase of lactation lengths. The coefficients of variation of total milk yield and average daily milk yield too are large enough to permit rapid improvement. Estimates of genetic changes in the herd through selection of breeding females have also been made. The various factors that would enable a greater selection pressure to be applied for accelerating annual genetic improvement in milk yield in tropical cattle are discussed.