Factors Affecting Birth Weights of Swine.
نویسندگان
چکیده
The data were taken from the breeding and farrowing records of the Animal Husbandry Section of the IOWA GRICULTURAL EXPERIMENT STATION during the years 1915 and 1917 to 1930 inclusive. The data were collected in connection with other experiments2 not planned expressly to make this study possible. Yet no practice was followed which seems likely to have affected the birth weights in a way which would have invalidated this analysis. The data analyzed are the birth weights of 506 litters containing 3639 pigs, all of which were produced by gilts about one year old at the time of farrowing. The time of weighing ranged from immediately after birth in some cases to a little more than twelve hours after birth in a few cases. Some pigs had suckled before being weighed but others had not. All litters were farrowed in the months of April and May, except nine in June, one in July and three in August. The breeds included purebred or high grade Poland Chinas, Tamworths, Hampshires and six different crosses. Over 71 percent of all these litters were purebred or high grade Poland Chinas. To determine the importance of each factor affecting birth weight, FISHER'S (1930) method of analyzing variance was used. The percentage of the variance which disappears when a certain variable is held constant may be used to express the closeness of the relation between that variable and birth weight (table 3). For those accustomed to think in terms of correlation coefficients, it is easy to understand such a proportion as equivalent to a squared primary correlation coefficient between birth weight
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عنوان ژورنال:
- Genetics
دوره 19 4 شماره
صفحات -
تاریخ انتشار 2003