| Modern dairy production must include the use of contemporary technology inboth management and genetic improvement of the dairy herd. The complexity ofdairy management necessitates the use of management software that considersnutritional requirements, milk production and quality, animal weight and conditionand other factors pertinent to efficient dairy production. Consistent improvement ofgenetic merit for milk yield is necessary on modern dairies to remain competitiveand profitable. Consequently, the objectives of this research were to adapt dairymanagement software to improve efficiency of production and to evaluate geneticimprovement strategies for three groups of dairy cattle: unimproved Holstein crosses,improved Holstein crosses, and purebred Holsteins for production in northwestChina.1. Three systems for genetic improvement of dairy cattle were implementseveral years ago to compare the productivity of a system of backcrossing unselectedHolstein bulls to Yellow cattle, backcrossing Holstein bulls selected for improvedmilk production to Yellow cattle, and a purebred Holstein system where bulls areselected for improved milk production. Traits evaluated over the years includedgrowth performance, lactation performance, reproductive performance, and linearbody measurements. Research results showed: Improved-hybrids mature weight issignificantly heavier than unimproved hybrids;12-month hip height of improvedhybrids is significantly higher than hybrids (P <0.05);15-month body length ofimproved-hybrids and unimproved hybrids is significantly higher than the purebredcattle (P <0.05); Birth weight, and6,12, and15month weight of generation3issignificantly higher than those of generation1(P <0.05); body weight at2,6,12,and15month, body height, body length, heart girth, and paunch girth generation3issignificantly higher than those of generation2, and those of generation2weresignificantly higher than generation1(P<0.05). The305d butterfat yield,305d milkprotein yield of improved-hybrids were significantly higher than those of purebredHolsteins (P <0.1); the305-d milk yield of improved hybrids was232kg and418 kg greater than that of purebred Holstein cows and unimproved hybrids respectively.Generation2305d milk yield was significantly higher than that of generation0(P <0.05) while parity2and3305d milk yield were significantly higher than that ofparity1(P <0.05); Reproductive performance of purebred Holstein cows (days tofirst breeding, days open and calving interval) was significantly greater than that ofunimproved hybrids (P <0.05). Days to first service of the improved hybrids were34days earlier than that of purebred Holstein. In body appearance characteristics,purebred Holsteins were significantly higher than unimproved hybrids in total score,body structure grade, udder score, milk character score, while the hybrids weregreater than purebred Holstein in rump score and limb hoof score. In generation2,body structure grade, limb hoof grade, udder score, milk character score were greaterthan that of generation0. Generation1cattle were greater than generation3cattle inrump score, while second parity body structure scores, limb hoof scores, udderscores and total scores were significantly higher than first parity scores. After thesecond parity, body scores decreased with each succeeding parity.2. The research used PCR-SSCP and DNA sequence analysis to study thegenetic variation of2loci (GH, GHR). Polymorphisms in the4th intron and in the5th exon in the growth hormone gene (GH), and in the8th exon in the growthhormone receptor (GHR) gene on the aforementioned three cow groups wereidentified and association analyses were done to relate growth performance andlactation performance to these polymorphisms. The results showed that thepolymorphism of GH in the4th intron was based on the mutation of Câ†'T in2017bpposition. There was an interaction of breed group and GH genotype for305d milkyield,305d butterfat yield,305d milk protein yield and305d lactose yield. Allele Thad a positive effect on lactation performance,15month weight, and heart girth at2months and6months of age. The CC type was significantly greater than the TT type(P <0.05) for body weight body length, and paunch girth at12and15months of age;body height of15months, and heart girth of6and15months of age. The CC and CTgenotypes in the improved-hybrids were greater than the TT genotypes for matureweight, and heart girth at2months and6months of age (P <0.05); Purebred CC and CT genotypes were greater than TT genotypes in mature weight, and heart girth at2months and6months of age (P <0.05). The polymorphism of GHR in the8th exonwas based on the mutation of Tâ†'A in4962bp position, with phenylalanine changedto tyrosine. Association analysis showe that allele T had a positive effect on growthperformance. Genotypte ATwas greater than genotype AA in weight at6monthsand15months of age, body height at6months and12months of age, and bodylength, heart girth, and paunch girth at6months of age (P <0.05). For unimprovedhybrids, the AT genotype was greater than the AA genotype in weight at6monthsand15months of age, and body length at6months of age (P <0.05). In theimproved hybrids, genotype AT was greater than genotype AA in weight, bodyheight, body length, and heart girth at6months of age and paunch girth at6monthsand12months of age (P <0.05). In the purebreds genotype AT was greater thangenotype AA inbody height at6and12months of age, body length at6months ofage, and heart and paunch girth at2months of age (P <0.05). There was littleevidence of any effect of GHR genotype with lactation performance.3. Research adapted a dairy management software package for use innorthwestern China. The software includes cattle, lactation, breeding, feeding, andfinancial management modules, as well as an early warning system and a module foreconomic benefit analysis. Use of this software requires the input of data related to aspecific dairy to compute the aforementioned analyses. In addition, the software alsocan effectively assist in breeding and improve the efficiency of the small andmedium-sized dairy production operations. The system has been put into operationin Gansu Lintao dairy farm, and it has greatly improved the production managementlevel and economic benefits for this dairy. |
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