McBnroB, G. E. eNo CuntsropnensoN, R. J. 1984. Effects of cold exposure on young growing lambs. Can. J. Anim. Sci. 64: 403410.The performance and development of young lambs housed at 0-r l"C or 21 -r l"C were compared in two experiments. Despite similar nutrient intakes for both treatment groups, preweaning growth rate of the cold-exposed lambs tended to be reduced. Bone growth from 4 to 9 wk of age revealed a significant effect of temperature on metatarsal length (P<0.05). By 10 wk of age morphological differences between the two groups were apparent, especially in terms of smaller ear dimensions (P<0.01), head (P<0.10) and metatarsal lengths (P<0.05) of the cold-exposed lambs. Leg bone lengths after slaughter (13 wk of age) also tended to be shorter for the lambs housed at 0'C. Organ weights measured after 11 wk of differential temperature exposure were similar for both groups except for slightly increased abomasal and thyroid weights (P<0.l0) in the cold-exposed group. Dry matter and nitrogen digestibilities of a concentrate ration fed to the weaned lambs were not affected by treatment, although nitrogen retention (glday,glg digestible N intake) was significantly lowered (P<0.05) as a result of cold exposure.
McBnroe, G. E. aNo CnnrsropnEnsoN, R. J. 1984. Effect of cold exposure on milk production and energy balance in the lactating ewe. Can. J. Anim. Sci. 64: 379_389.The lactational performances of shorn ewes chronically exposed to a thermoneutral (21 + l"C) or cold (0 + 1"C) environment were compared in two experiments. Heat production measured after 1, 2r and 41 days of cold exposure was increased by 20Vo (P<0.05), 43Vo (P<0.01) and 55Vo (P<0.001), respectively, over thermoneutral control values. In both experiments, cold exposure increased milk fat concentration (P<0.05). Milk protein and lactose concentrations were maintained in exp. lbuttendedtobeincreasedinexp.2asaresultofcoldexposure.Milkobtained from the cold-exposed ewes was characterized by a relative decrease in short-chain fatty acid secretion (P<0.01). Although milk composition was affected by cold stress, daily milk production was not significantly altered; as a consequence, total energy lost in the milk tended to be slightly higher for the cold-stressed ewes. The increased energy lost as heat and in the milk during cold exposure resulted in a net energy deficit throughout most ofthe experimental period. The present data suggest that the lactational performance of a ewe nursing a single lamb is not impaired by chronic exposure to an ambient temperature of 0"C. pressure. This apparatus allowed normal access of the ewe to feed and water but did not restrict lying, standing or nursing activities. Mrr-r pnooucrloN AND coMposITIoN. Pretreatment differences in milk yield and composition were assessed by milking the ewes at the end of the adaptation period, prior to reducing the temperature to 0'C in the two chambers housing the CE ewes. During the experimental period milk production and composition were assessed once weekly (wk 3-8 of lactation).Milk yield was determined using an oxytocinhandmilking procedure. Between 0800 and 0900 h on the day of collection each lamb was confined to a wire cage within its dam's pen. Milk was collected by injecting 5 USP oxytocin i.m. and rapidly hand-milking both halves of the udder. After milk flow had ceased, an additional 2.5 USP oxytocin was given i.m. and any residual milk stripped from the udder. The milk obtained from this first collection was discarded. The oxytocin-handmilking procedure was repeated 2.5 h later and the collected milk was weighed to the nearest gram. Daily milk yield was estimated by multiplying the 2.5-h level of milk production by a factor of 9.6. Subsamples of the collected milk were immediately strained through cheesecloth, placed in sample vials containing potassium dichromate as a preservative and stored at 4"C. Subsequently The lamb was then replaced in the cage and allowed to suckle at 3-h intervals over a total oeriod of 24 h. The quantity of milk produced-at each suckling period was determined by weighing the lamb to the nearest gram immediately prior to and following nursing, the difference in weight being taken as the weight of milk consumed. Any feces or urine voided by the lamb duri...
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