Browsing by Author "Bett, Rawlynce C."

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    Cattle Breeds: Extinction or Quasi-Extant?
    (Multidisciplinary Digital Publishing Institute, 2013-08-27) Bett, Rawlynce C.; Okeyo, Mwai A.; Malmfors, Birgitta; Johansson, Kjell; Agaba, Morris; Kugonza, Donald R.; Bhuiyan, A. K. F. H.; Filho, Anibal E. Vercesi; Mariante, Arthur S.; Mujibi, Fidalis D.; Philipsson, Jan
    Uniquely selected breeds bred over thousands of years of domestication in a wide range of environments have been declared extinct over the last century. Still more breeds are at risk of becoming extinct and the rate continues to accelerate. Assessing the current status and possible future dynamics of livestock breeds is therefore a critical step in the management of Animal Genetic Resources (AnGR). This study applies a qualitative approach to comprehensively analyze cattle genetic resources in selected countries in order to better understand the risk status of cattle breeds and those that need to be considered extinct and/or quasi-extant. The status of each breed, i.e., not at risk, critical, endangered and extinct, was verified using information available at the Domestic Animal Diversity Information System (DAD-IS) web site, as well as cattle statistics (where available) and a breed survey. In most examples, breeds listed as extinct have played important roles in the development of new breeds, and should not be classified as extinct, unless proven otherwise, given that even breeds existing in vivo are developing. Therefore, a new risk status quasi-extant for this category of cattle breeds is suggested. In addition, based on the findings of this study, the concept of breed needs to be questioned as relates to it being a good measure of genetic diversity. Further investigations of the situation of cattle breeds (and other livestock species) in more countries/continents using similar categories are deemed necessary.
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    Frontiers | Milk Composition for Admixed Dairy Cattle in Tanzania
    (Frontiers Media, 2018-04-24) Cheruiyot, Evans K.; Bett, Rawlynce C.; Amimo, Joshua O.; Mujibi, Fidalis D. N.
    It is well established that milk composition is affected by the breed and genotype of a cow. The present study investigated the relationship between the proportion of exotic genes and milk composition in Tanzanian crossbred dairy cows. Milk samples were collected from 209 animals kept under smallholder production systems in Rungwe and Lushoto districts of Tanzania. The milk samples were analyzed for the content of components including fat, protein, casein, lactose, solids-not-fat (SNF), and the total solids (TS) through infrared spectroscopy using Milko-Scan FT1 analyzer (Foss Electric, Denmark). Hair samples for DNA analysis were collected from individual cows and breed composition determined using 150,000 single nucleotide polymorphism (SNP) markers. Cows were grouped into four genetic classes based on the proportion of exotic genes present: 25–49, 50–74, 75–84, and >84%, to mimic a backcross to indigenous zebu breed, F1, F2, and F3 crosses, respectively. The breed types were defined based on international commercial dairy breeds as follows: RG (Norwegian Red X Friesian, Norwegian Red X Guernsey, and Norwegian Red X Jersey crosses); RH (Norwegian Red X Holstein crosses); RZ (Norwegian Red X Zebu and Norwegian Red X N’Dama crosses); and ZR (Zebu X GIR, Zebu X Norwegian Red, and Zebu X Holstein crosses). Results obtained indicate low variation in milk composition traits between genetic groups and breed types. For all the milk traits except milk total protein and casein content, no significant differences (p < 0.05) were observed among genetic groups. Protein content was significantly (p < 0.05) higher for genetic group 75–84% at 3.4 ± 0.08% compared to 3.18 ± 0.07% for genetic group >84%. Casein content was significantly lower for genetic group >84% (2.98 ± 0.05%) compared to 3.18 ± 0.09 and 3.16 ± 0.06% for genetic group 25–49 and 75–84%, respectively (p < 0.05). There was no significant difference (p < 0.05) between breed types with respect to milk composition traits. These results suggest that selection of breed types to be used in smallholder systems need not pay much emphasis on milk quality differences as most admixed animals would have similar milk composition profiles. However, a larger sample size would be required to quantify any meaningful differences between groups.