Document k6Q4przL61y4XQk4LYma6dpvq

120 ; CHARTERc8 :-. 1965 Guide And.Data Book ture of 90 F showed a reduced rate of spermatogenesis, although a period of 3 weeks at 70 F was sufficient to effect recovery to the normal rate.18-1* Later reports further suggest that high air temperatures may cause lowered fertility for other reasons.88 Subjecting ewes to temperatures of 100 F just before mating will cause a fertilisation failure.*1 Generally, there will be some form of degeneration of the structures of the ovum. .< Under practical-conditions, the greatest loss, in potential offspring conceived in, a high temperature. environment appears to be due to very early embryonic death.88*9 The de gree of susceptibility to adversely high.temperatures is. great est near the time of mating, but this susceptibility generally decreases as the length of rime after mating increases. A tem perature of 90 F and relative humidity of 65 percent at timn of mating will cause most of the embryo to die at an early age.9 The same conditions applied later in the gestation period will not cause death but will result in the birth of small,' weak Iambs.** The longer the period of high temperatures, especially during the last third of the gestation,,the. greater will be the number of small, weak lambs bom.8* It now appears that all reproductive processes are moreadversely affected by high air temperature when accompanied by a high relative humidity. Heat Produrtion Only a few tests of heat' production have been conducted mostly for correlation with other physiological' data. No studies, to' determine design load calculations? similar to those performed'with other farm animals, have been conducted with sheep. The ability of Iambs to generate heat is of considerable practical importance, because they are normally bom-during the most severe climatic season. One study indicated that new bom lambs were limited in heat producridn to 30 Btu per-(hr) Oh), which was five times the basal level.** The con ditionsof the tests were from 14 F to 32 F with al2 mph wind, but lambs are capable of withstanding temperatures as low the rate of'wool growth.-It appears that wool growth aids in limiting radiantheating loads1* which is significant because of their normal posture.17' as --40 F. They tend to orient to the wind direction to mini mise convective heat loss. Table 1 shows an example of the relationship between fleece . length and heat production.88,87 Reproduction' SWINE .-,-v r ' Feed conversion and daily rate of weight gain of growing Sheep.will mate ohly during certain periodsof the year, but - - swine are affected by the level of ambient air temperature.88 may sometimes' be,induced to'mate- outside the; normal Fig. 7 shows thatambient temperatures between 60and 70 F season'iT'the':natura!-environment-'isj modified. Ewes may produce maximum rates of gain. Fig. 8 shows the effect of sometimes be bred-if exposed to air. temperatures of`45 F before mating. ambient temperature on feed conversion,-and.shows that this declines (more feed consumed per pound of gain) as. tempera' A number of studies have been made into the effects of ~ tures fall below 60 F. As temperatures increase above 70 F, high temperatures on. reproduction of sheep. Over 30. years .. daily feed consumption declines and rate of gam hi reduced. ago it was. reported'that air temperature.affected the rate of If the daily air temperature cycles more than 10 F deg on spermatogenesis. Bams' kept at -an environmental tempera- ?either tide of 70 F, the daily gain by pigs will be lowered and Table ! .... Heat Production of Sheep as Related f . ` to Fleece Length**47 ladm Shorn 0.5 1.0 1.5 . 46 F At.68F \ TaiaF . . Latent8 . Total* ' Latent*. 3.15' ... 8%; . 2.08 2.15 ' 1.76" 1.73 16% 1.54 1.54 1.54 14% 26% .As 90 F Total* ' Latent8 1.54 1.54 1.54 1.54 38% 62% -- (2i-* SO - 200 L Tl"- 60 70 80 AVERAGE OAILT TEMPERATURE -P 1 ' fig. 7 :... Deviation of Average Daily Swine Gains with Temperature88 fovironmentalControl for Animals and Plants--Physiological-Considerations their feed requirements per pound of gain will be increased.88 Reasonably constant air temperatures are desirable. > The level of the air temperature in which swine are grown effect deposition am! retention of protein (carcass quality). Formation of lean meat is reportedly highest in pigs raised at temperatures between 60 and 70 F.*8 The ratio of protein to fat bw*>m less at air temperatures above and below 59 F.* There isevidence that sows are benefited bysome type of cool inginhot weather.9 - Swizte gains and feed conversion rates are not increased by high air velocities, and in many cases are adversely affected.9 Vie. 9 shows a comparison of feed utilization and gain at low 121 Heat and Moisture Heatahd moisture that must be accounted for in the venti lation or air conditioning of swine boating ore shown in'Figs? 10 and 1L** These figures are for swine weighing between 50 and' 400 lb,' housed at temperatures ranging from 50 to 90 F. These data are the. sensible and latent heats measured in a room containing hogs. Thus? a portion of the sensible heat was used to evaporate the moisture of urine, etc., and ultimately appears as latent heat. For design purposes, the'data reflect actual conditions better than metabolic heat production from .an individual hog. ; ` ' '' ` - It has been*found8* that these same data can'be'applied even where building temperatures are cycling, if the average air temperature during the cycle is used for design. The total animal heat load.and the latent load which the ventilation system must remove are greater than the values shown in Figs. 10 and U, if the air velocity around the animals is'more than about 50 fpm.*8 POULTRY .The adverse effects of high thermal environments (above 85 F) on egg production are: fewer eggs, reduced egg weight, and thinner beils.,s'S6-*7 Hens older than one year are more adversely affected by high thermal environment than younger hens. Larger hens, such as Rhode Island Beds, are more ad versely affected than smaller hens, such as White Leghorns. Hatchability also declines as temperatures increase. Although the fertility rate is~good at 70 F, it declines at 86 F. Feed re quirements increase markedly below 45 F, and activity and productivity decline below 32 F. The suggested ideal environ ment is between 55 and 75 F. ;' Poultry do not have sweat glands that are comparable to man's and latent heat dissipation is primarily through the respiratory system. Increasing the relative humidity above 70 percent, at 85 F dry-bulb temperature, produces increased respiration rate and drooping wings. However? after 7 to 10 days, respiration rates may decrease. The control of dust is a problem that may contribute to disease. A relative humidity of 70 to 75 percent is generally recommended. - - In terms of rate of gain and' efficiency,' broiler chickens have undergone tremendous-genetic improvement during the past ten years/ Older data on the subject must be used with cau tion.-Table 2 indicates feed consumption and growth of a mod- erostrain of broilers.: \ \ ; !. : >. - Supplemental heat is generally needed for newly hatched chicks. Modern strains of broilers-respond-well to .brooder temperatures of 92 F under the hovers. Thereafter, air:tem peratures may. be decreased at a rate of -7 ,F deg per week. Relative humidities of 65 to 70 percent promote good feather- +0.| t si*** || 50-200 LB 'V 12-50 L AVERAGE OAILT TEMPERATURE - P Rg. 8 .... Deviation of Pounds Feed Required per Pound Gain for Swine** Rg. 10 .... Room Sensible Heal in a Hog House"