Publication Date

5-1987

Advisor(s) - Committee Chair

Gordon Jones, James Worthington, Elmer Gray

Degree Program

Department of Agriculture

Degree Type

Master of Science

Abstract

The purpose of this study was to determine differences between littermate boars and barrows for performance and carcass traits in the Iowa and Northeast Iowa Swine Testing Stations. Data were obtained from 917 litters including 1,804 boars and 917 barrows. The data included 1,086 boars and 581 barrows from the Iowa Station at Ames, Iowa, and 718 boars and 336 barrows from the Northeast Iowa Station at New Hampton, Iowa. The Iowa Station data were obtained over a period of 12 seasons from the fall of 1979 through the fall of 1985, and the data from the Northeast Iowa Station were collected in eight seasons from the fall of 1981 through the spring of 1985. The spring testing season included pigs born from November through March, and the fall testing season included pigs born from May through September. Littermate boars and barrows from the following purebred breeds were used: Berkshire, Chester White, Duroc, Hampshire, Landrace, Poland China, Spotted, and Yorkshire.

Boars grew .03 (2.21+/-.20 vs. 2.18+/-.21) and .10 (2.21+/-.18 vs. 2.11+/-.22) pounds/day faster (P<.01) than littermate barrows in the Iowa and Northeast Iowa Stations. Boars had .58 (.80+/-.08 vs. 1.38+/-.20) inches less (P<.01) backfat than littermate barrows (N=581) in the Iowa Station. In the Northeast Iowa Station, boars were significantly (P<.01) leaner than barrows when comparing average backfat of boars with carcass backfat measurements of Ilttermate barrows at the tenth rib (.76+/-.06 vs. 1.06+/-.21) or the average of three carcass backfat measurements (.75+/-.08 vs. 1.29+/-.18 and .79+/-.05 vs. 1.31+/-.19). Boars had .67 (5.49+/-.42 vs. 4.82+/-.67) and .66 (5.62+/-.28 vs. 4.96+/-.65) square inches larger (P<.01) loin eye areas than littermate barrows in the Iowa and Northeast Iowa Stations, respectively.

The t test revealed no significant (P>.05) differences between boars and barrows for average daily gain among the eight major breeds in the Iowa Station. However, at the Northeast Iowa Station, the Duroc (2.39+/-.19 vs. 2.12+/-.21) and Hampshire (2.16+/-.17 vs. 2.07+/-.24) boars grew significantly faster (P<.01) than littermate barrows. The t test also revealed that boars averaged seven days (156.00+/-10.78 vs. 163.00+/-12.90) younger (P<.01) at 230 pounds than barrows in the Northeast Iowa Station. Although the sample size was small and the differences nonsignificant, there were some breeds in which barrows appeared to grow faster than boars. The I test for boar-barrow differences among breeds revealed that boars had significantly (P<.01) less average backfat than littermate barrows for eight major breeds in the Iowa Station and for seven breeds in the Northeast Iowa Station. For both stations, the differences in backfat thickness between boars and barrows was lowest for the Hampshire breed and the greatest differences were between boars and barrows in the Chester White, Yorkshire, Berkshire and Landrace breeds. The t test for loin eye area revealed that boars had significantly (P<.01 or .05) greater loin eye area than barrows for all breeds except Poland China in the Iowa Station and Landrace in the Northeast Iowa Station. The sex differences between littermate boars and barrows for backfat and loin eye area were significantly different (P<.01) for all years and seasons in the Iowa and Northeast Iowa Stations. The sex differences between littermate boars and barrows for backfat and loin eye area have been increasing in both stations with the largest increase occurring during the last five years. The differences between boars and barrows for days to 230 pounds were significantly different (P<.01) In all years and seasons for both stations. In comparing data for 1981 and 1985, both boars and barrows averaged ten days younger at 230 pounds In 1985 than in 1981.

Coefficients of correlation for various measurements of performance and carcass cutability between littermate boars and barrows were determined. In general, there were positive associations between boar and barrow data; however, the correlations were relatively low. The predictive value of the barrow data appears to be of little use In estimating breeding values for boars.

Although a limited number of Chester White pens were included in this study, the coefficients of correlation between littermate boars and barrows suggest that castration may have a different effect upon performance and carcass cutability of Chester White than for other breeds. Unfortunately for Chester White breeders, there appears to be a much higher positive correlation between average daily gain and beckfat thickness for Chester White boars and barrows than for other breeds. In other breeds, the correlation between growth rate and backfat is low enough to allow simultaneous progress for improving both traits. A similar desirable low correlation was found between growth rate and loin eye area for other breeds.

The coefficients of correlation between backfat and loin eye area were greater for barrows than boars, suggesting that errors of measurement may have been prevalent in the boar data. Large errors In measurement of boar backfat could account for some or all of the increased difference in backfat thickness observed between littermate boars and barrows during recent years.

Disciplines

Agriculture | Animal Sciences | Life Sciences | Meat Science

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