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

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Similarly, calves, heifers, and cows sired by bulls with high genetic potential for milk production were found to have higher circulating levels of blood GH than animals sired by bulls from a random population (Akers, 1985). Sejrsen et al. (2000) noted that at the same level of feeding, the genetic capacity for higher milk production is positively correlated with the genetic capacity for higher growth. Therefore, for groups with greater milk yield potential, optimum daily gain would be higher, and for an individual with higher milk yield potential, gain above the optimum would have less negative impact on lifetime milk production. And, within a prepubertal group or breed, at an optimum feed level, a higher genetically-based growth rate will be reflected in higher milk yield (Figure 5), whereas a higher growth rate due to increased feeding will be reflected in reduced milk yield potential. Figure 5. Illustration of the expected change in optimal daily gain with the increased genetic potential in milk yield in Danish dairy cattle from the 1980’s to the 2000’s. The relationship between feeding level and milk yield is unchanged and the higher optimal daily gain is achieved at the same feeding level. From Sejrsen et al., 2000. Conclusions Milk production is limited by the number of secretory cells in the udder. Diets excessive in energy, prior to puberty, inhibit the growth of the mammary epithelial tissue that will later sprout the milk-producing alveolar cells, and thus also limit lifetime milk yield. It is therefore recommended that dairy sheep producers should restrict the energy intake of replacement ewe lambs to about 65 to 75% of their ad-libitum intake. This will increase the rate of mammary growth and increase the total amount of epithelial tissue that will later develop into milk-secreting alveolar cells. The negative impact of high-energy diets on ewe lambs is greatest starting at about 4 to 6 weeks of age and declines over the next few months of age, due to both the reduced concentration of circulating growth hormone and the lessening influence of growth hormone on mammary tissue. At the end of this phase of rapid duct extension, the absolute amount of ductal tissue, the degree of ductal penetration into the mammary fat pad, and the final size of the fat pad, will be primary determinants of the ultimate size of the adult lactating mammary gland.
Early puberty, especially before 20 weeks of age, may substantially reduce mammary gland development in rapidly-reared ewe lambs by curtailing both the rate and the duration of the allometric growth phase. Increased feed levels after 20 weeks have less influence on mammary development and can improve liveweight at breeding. Acknowledgements This study was funded by a grant from the Northeast Sustainable Agriculture Research & Education (SARE) Program. The authors are also grateful for the technical assistance provided by Mr Bruce Clement, UNH Cooperative Extension, Keene, NH, and by Dr. Michael Akers, Department of Dairy Science, Virginia Tech, Blacksburg, VA. Literature cited Akers, R.M. 1985. Lactogenic hormones: binding sites, mammary growth, secretory cell differentiation, and milk biosynthesis in ruminants. J. Dairy Sci. 68:501-519. Anderson, R. R. 1975. Mammary gland growth in sheep. J. Anim. Sci. 41:118-123. Forsyth, I.A. 1996. The insulin-like growth factor and epidermal growth factor families in mammary cell growth in ruminants: action and interaction with hormones. J. Dairy Sci. 79:1085-1096. Harrison, R. D., Reynolds, I. P., and W. Little. 1983. A quantitative analysis of mammary glands of dairy heifers reared at different rates of live weight gain. J. Dairy Res. 50:405-412. Hohenboken, W.D., Foldager, J., Jensen, J., Madsen, P., and Andersen, B B. 1995. Breed and nutritional effects and interactions on energy intake, production and efficiency of nutrient utilization in young bulls, heifers, and lactating cows. Acta. Agric. Scand. Sect. A Anim. Sci. 45:92-98. Houseknecht, K. L., Boggs, D. L. Campion, D. R., Sartin, J. L, Kiser, T. E., Rampacek, G. B., and H. E. Amos. Effect of dietary energy source and level on serum growth hormone, insulin-like growth factor-1, growth and body composition in beef heifers. J. Anim. Sci. 66:2916-2923. Hovey, R.C., McFadden, T. B., and R. M. Akers. 1999. Regulation of mammary gland growth and morphogenesis by the mammary fat pad: a species comparison. J. Mamm. Gland. Biol. and Neoplasia. Vol. 4, no. 1, 53-68. Johnsson, I. D. 1988. The effect of prepubertal nutrition on lactation performance by dairy cows. In: Nutrition and Lactation in the Dairy Cow. P.C. Garnsworthy (Ed.) Butterworths, London. pp. 171-192. Johnsson, I. D. and I. C. Hart. 1985. Pre-pubertal mammogenesis in the sheep. 1. The effects of level of nutrition on growth and mammary development in female lambs. Anim. Prod. 41:323-332. Johnsson, I. D. and J. M. Obst. 1984. The effects of level of nutrition before and after 8 months of age on subsequent milk and calf production of beef heifers over three lactations. Anim. Prod. 38:57-68. Johnsson, I. D., Hart, I. C., and A. Turvey. 1986. Pre-pubertal mammogenesis in the sheep. 3. The effects of restricted feeding or daily administration of bovine growth hormone and bromocriptine on mammary growth and morphology. Anim. Prod. 42:53-63. Johnsson, I. D., Hart, I. C., Simmonds, A. D., and S. V. Morant. 1985. Pre-pubertal mammogenesis in the sheep. 2. The effects of level of nutrition on the plasma concentrations of growth hormone, insulin, and prolactin at various ages in female lambs and their relationship with mammary development. Anim. Prod. 41:333-340.
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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
Page 112 and 113: percentage is not expected to resul
Page 114 and 115: Improved AI technique Artificial in
Page 116 and 117: Identifying major genes or QTL rela
Page 118 and 119: Figure 5. Half-sib families and QTL
Page 120 and 121: In the case of cheese the problem i
Page 122 and 123: Emanuelson, U., Danell, B., Philips
Page 124 and 125: Rothschild, M. F., Soller, M. (1997
Page 126 and 127: teat placement in dairy ewes (Fern
Page 128 and 129: that of the average milking time. M
Page 130 and 131: 1988) and active expulsion of fat f
Page 132 and 133: References Barillet, F., and F. Boc
Page 134 and 135: Table 1. Least squares means ± SEM
Page 136 and 137: 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 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 and 188: GROUP BREEDING SCHEME: A FEASIBLE S
Page 189 and 190: Where: h = square root of heritabil
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
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Reports in dairy cattle concerning
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Muir, D.D., D.S. Horne, A.J.R. Law,
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Milk yield (kg) 1.4 1.2 1.0 0.8 0.6
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A Milk protein (%) A A Milk protein
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TAPPE FARM TOUR Jon & Kris Tappe, T
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a little special attention every da
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