Dairy Sheep Symposium - the Department of Animal Sciences ...

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Selection differential. The selection differential is a simple concept and refers to the difference between the selected animals and the average of the entire flock as shown in Figure 1 where the average milk production is 120 liters and the average milk production of the selected animals is 150 liters. The selection differential will be 30 liters. Figure 1: Selection differential Selected animals Flock average = 120 l Selected average = 150 l Selection differential = 30 l Combining the heritability and the selection differential, the theoretical genetic improvement per generation would be: ΔG = h 2 x Sd In the example the genetic improvement of dairy yield of the flock would be: ΔG = .30 x 30 ΔG = 9 liters Considering that in sheep the generation interval is about 3 years, the genetic improvement per year would be: ΔG /L = h 2 x Sd /3 = .30 x 30/3 = 3 liters Reducing the generation interval by using ram lambs and by breeding young ewes at 7 months of age, will greatly improved the annual genetic improvement. However, the formula is rather simplistic and geneticists in charge of selection programs prefer to use the following equation: ΔG/ L = h x σ a x I / Generation interval
Where: h = square root of heritability, which represents the accuracy of selection. The accuracy of selection is greatly improved if all environmental factors (non genetics) can be removed. Many production traits need to be adjusted for, let’s say, age of dam, sex, type of birth, birth weight, type of rearing, etc… Without using adjusting factors, gross mistakes can be made and little genetic progress will be realized. The accuracy of selection will also be improved if the performance of all relatives of the animal to be selected are taken into consideration. This is the purpose of EPDs (Estimated Progeny Difference) calculated by NSIP in the US and by ROP in Canada. σ a = amount of genetic variation between animals. The larger the variation the better and easier the selection. Without variation in a population, selection would become impossible. Generally there is no problem with not having enough variation. I = intensity of selection. Let’s say that a producer has 100 ewes producing 150 lambs of which 75 are females. Just to replace older ewes, unhealthy ewes, dead ewes, he will need to keep around 25 ewe lambs or 33% of his ewe lamb crop. According to tables, the intensity of selection is 1.1, which is very little. On the ram side he needs to keep only 3 rams or 4% of his ram lamb crop representing an intensity of selection of 2.15. In this case ram selection is twice as powerful as ewe selection. However, how can a producer select an animal that does not express the trait he is selecting for such as milk production? The only information available will be the performance of his ascendants (Dam, grand Dam etc..) and EPDs can be calculated. However the most important information, performance of half sibs or performance of his progeny, are missing. The accuracy of selection is therefore greatly reduced. The purpose of this short preamble was to demonstrate that the selection practiced by individual producers is often inaccurate and disappointing because: - The number of animals to choose from is too small resulting in no or very little intensity of selection. - The accuracy of selection is very small because of the impossibility to eliminate all or most of the environmental factors. - The producer has no mean to compare the performance of his animals to the performance of his neighbor’s animals. If he needs to purchase replacement animals (ewes or rams) he has no resource to see if the animals he is purchasing are, on average, better than his. For rapid genetic improvement, the goal of the dairy sheep industry should be to develop a national or regional breeding program which includes recording of milk production of ewes, centralized processing of milk production records and estimation of EPDs, planned mating of ewes and rams with superior EPDs, progeny testing of promising young rams and the rapid spread of superior genetics through the population by the use of artificial insemination with semen from proven rams. This is the U.S. dairy cattle model that is so successful and it is the system used on the Lacaune breed in France on which genetic gain has been an average of 2.4% for the last 30 years. The North American sheep dairy industry, however, does not have the financial means of the
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Proceedings of the 7 th Great Lakes
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ORGANIZING COMMITTEE 7 TH GREAT LAK
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Thursday, November 1 Noon Registrat
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SPEAKERS Dr. Juan-José Arranz, Dpt
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Table of Contents (continued) Lates
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eeding and were created to have hig
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Disease in the U.K. and subsequentl
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sheep production conditions in Wisc
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Pinelli, F., P. A. Oltenacu, G. Ian
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Bucket milking and elevated platfor
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Throughputs in different parlors No
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1 - Stand up as straight as possibl
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Roques J.L.. 1997. Traite des brebi
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Grade B milk quality is as follows:
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(c) Not Applicable (d) At least 10
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TOILET AND WATER SUPPLY 7. Toilet (
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(c) Drugs and medicinals shall be l
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FARMSTEAD CHEESE AND MARKETING Stev
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5. Cheese is delivered in person, w
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to participate with us, we are enga
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The key points to this plan were: Y
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Milk is supplied in two major forms
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MANAGEMENT OF A DAIRY SHEEP OPERATI
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4 3.5 3 2.5 2 1.5 1 0.5 Chart 1: Mi
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Facilities and Equipment The requir
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from the ewes at 12 to 24 hours of
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COMPARISON OF EAST FRIESIAN AND LAC
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two-year-olds in 2001. East Friesia
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Reproduction. Table 4 compares the
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six ewes were sired by Lacaune ram
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FACTORS AFFECTING THE QUALITY OF EW
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Sheep Genetic factors breed and gen
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Genetic factors The breed and genot
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Physiological factors affecting she
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Management factors affecting the qu
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sheep with one peak of milk ejectio
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An important aspect of dietary fibr
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References Alais C. (1974). Science
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Bufano G., Dario C. and Laudadio V.
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Cowan R.T., Robinson J.J., McHattie
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Folman Y., Volcani R. and Eyal E. (
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Kalantzopoulos G. (1994). Influence
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McHattie I., Fraser C., Thompson J.
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Peart J.N. (1970). The influence of
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Ranieri M.S. (1993). La variazione
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Treacher T.T. (1970). Effects of nu
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EVALUATION OF SENSORY AND CHEMICAL
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ing, the cheeses were brined for 18
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The FFA concentrations generally in
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Table 1. Composition of pasteurized
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Table 6. Body and texture scores 1
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Present Development of Selection Sc
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Breed Usage in Europe Crossbreeding
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nearly 1. As a consequence this cha
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Table 5. Repeatabilities and phenot
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percentage is not expected to resul
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Improved AI technique Artificial in
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Identifying major genes or QTL rela
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Figure 5. Half-sib families and QTL
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In the case of cheese the problem i
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Emanuelson, U., Danell, B., Philips
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Rothschild, M. F., Soller, M. (1997
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teat placement in dairy ewes (Fern
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that of the average milking time. M
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1988) and active expulsion of fat f
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References Barillet, F., and F. Boc
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Table 1. Least squares means ± SEM
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Table 3. Simulation of parlor throu
Page 138 and 139: EFFECT OF REDUCING THE FREQUENCY OF
Page 140 and 141: Individual ewe milk production (mor
Page 142 and 143: dimanche soir sur les brebis de rac
Page 144 and 145: A B A Morning milk yield, kg B Adj.
Page 146 and 147: Background and History: Most sheep
Page 148 and 149: Percent 100 80 60 40 20 0 87 Effect
Page 150 and 151: Fall Lambing Percentage 100 90 80 7
Page 152 and 153: THE EFFECT OF GROWTH RATE ON MAMMAR
Page 154 and 155: After puberty, the mammary gland re
Page 156 and 157: Many trials have examined the mamma
Page 158 and 159: From these results the authors conc
Page 160 and 161: Onset of Puberty and Reproductive P
Page 162 and 163: Similarly, calves, heifers, and cow
Page 164 and 165: McCann, M. A., Goode, L., Harvey, R
Page 166 and 167: DISCUSSION Stability of Frozen Raw
Page 168 and 169: analyzed for titratable acidity, sy
Page 170: 411-416. Wendorff, W.L. 1998. Updat
Page 175 and 176: Recent Outbreaks involving Cheddar
Page 177 and 178: testing on raw milk at the farm. Th
Page 179 and 180: THE AUSTRALIAN SHEEP DAIRY INDUSTRY
Page 181 and 182: The University of Western Australia
Page 183 and 184: Heterosis did not seem to intervene
Page 185 and 186: Lambs The problem of weaning lambs
Page 187: GROUP BREEDING SCHEME: A FEASIBLE S
Page 191 and 192: Second step. All members enroll in
Page 193 and 194: The structure and movement of anima
Page 195 and 196: CAN THE OVARY INFLUENCE MILK PRODUC
Page 197 and 198: dividing the amount of milk obtaine
Page 199 and 200: the CL there were significant diffe
Page 201 and 202: etween milkings. Finally, this woul
Page 203 and 204: Table 1. Least squares means ± SEM
Page 205 and 206: A Daily milk yield (kg) A B Milk fl
Page 207 and 208: Progesterone (ng/ml) 8 6 4 2 0 CLY:
Page 209 and 210: milk volume within the cistern (Mar
Page 211 and 212: Results Treatment milk yield increa
Page 213 and 214: Reports in dairy cattle concerning
Page 215 and 216: Muir, D.D., D.S. Horne, A.J.R. Law,
Page 217 and 218: Milk yield (kg) 1.4 1.2 1.0 0.8 0.6
Page 219 and 220: A Milk protein (%) A A Milk protein
Page 221 and 222: TAPPE FARM TOUR Jon & Kris Tappe, T
Page 223: a little special attention every da
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