Boar Taint: How Much Is Too Much?

E.J. Squires, Y. Lou and J.P. Gibson

Background

The potential benefits from raising entire male pigs instead of castrates include lower feed costs and increased carcass lean yield. The costs of genetic selection programs would also be lowered if nonselected breeding stock could be sold as normal market hogs. The main reason that entire males are not raised for meat is the possibility of boar taint in the carcasses. Boar taint can be caused by high levels of boar taint (16-androstene) steroids and skatole. If entire male pigs are to be used for fresh pork production, there should be low levels of boar taint at normal market weights. Chemical tests have been developed to measure skatole and boar taint steroids in pig carcasses. Levels of boar taint steroids can be conveniently measured in salivary gland or fat, while skatole is measured in fat. The OPCAP provided a unique opportunity to obtain samples of entire male pigs for analysis of boar taint. The objectives of this study were to:

  1. determine the levels of boar taint by chemical analysis in entire male pigs slaughtered at normal market weights, and
  2. determine the effect of breed, age and slaughter weight on the levels of boar taint compounds.

Materials and Methods

Levels of skatole were measured in fat samples using the Danish colorimetric method and levels of the boar taint steroids were measured in salivary glands and fat using the chemical test developed in this lab. Boar taint compounds were measured only in entire males. Details of statistical analyses are given in Appendix 3.

Results and Discussion

Some of the key carcass parameters of the pigs slaughtered in the Ontario Pork Carcass Appraisal Project are summarized in Table 1. Entire males had decreased backfat, improved feed efficiency and increased lean compared to castrates, with no difference in average daily gain. Based on the differences in carcass value and feed costs, raising entire males would provide a return of approximately $9/pig more than castrates. Based on an average margin of $25/pig, this is an increase in profitability of 35% per pig (C.F.M. deLange, personal communication). The average levels of boar taint compounds in four breeds of pigs are reported in Table 2. Average levels of boar taint steroids in salivary gland and backfat were similar among the breeds, except for Duroc, which had much higher levels of taint steroids. Levels of skatole varied somewhat among the four breeds, with highest levels in Hampshire and lowest levels in Yorkshire males. There was a significant regression of the levels of the boar taint compounds with percent lean, with leaner animals having lower levels of boar taint steroids in salivary gland and fat and skatole in fat (regression coefficients of -0.808, ­0.0418 and -0.0045, respectively). This may be because leaner animals are less physiologically mature, and boar taint steroids increase with degree of maturity. The mean levels of boar taint compounds in entire male pigs grouped according to age or weight are given in Table 3. The pigs were divided into three categories by weight: less than 105 kg, from 105 to 115 kg and more than 115 kg; and into three categories by age: less than 170 days, from 170 to 180 days and more than 180 days. There was no significant effect of weight on levels of boar taint steroids in salivary gland. Similar results were also obtained with boar taint steroids in fat (data not shown). However, there was a significant increase in boar taint steroids in salivary gland, but not in fat of Duroc entire males with increasing age. There was no effect of age or weight class on skatole levels in entire males.

Implications

Levels of the boar taint compounds in Hampshire, Landrace and Yorkshire entire male pigs were low and did not vary significantly over the age and weight range of animals in this study. The meat for the majority of these animals would be fully acceptable to consumers. High levels of boar taint steroids were, however, found in Duroc entire males and a fairly high proportion of carcasses would produce meat with perceptible boar taint. Thus, the amount of boar taint present in modern genotype pigs other than Durocs and their crosses is generally low. Overall the large majority of purebred males would not produce tainted meat and do not deserve to be discounted in value. Work is ongoing into rapid methods of boar taint detection and on the possibility of eliminating boar taint completely, which would remove the need for carcass testing for boar taint, and open possibilities for use of entire males in commercial production. Data is needed on the levels of boar taint in crossbred males managed according to modern commercial practises.

Table 1. Least squares means of carcass parameters by sex.
Trait
Barrow
Gilt
Boar
Slaughter weight (kg)
105.5 a
103.8 b
109.4 c
ADG (kg/day)
0.888a
0.823b
0.886a
Backfat at 100 kg (mm)
15.22a
13.19b
11.94c
Feed efficiency
2.74a
2.74a
2.46b
Estimated yield (new) (%)
59.5a
61.4b
61.4b
Lean in 3 primals (%)
50.8a
54.0b
55.1c
Dressing %
79.0b
79.4a
78.5b
abc Values within a row with shared superscripts are not significantly different (P < 0.05).

Table 2. Least squares means of boar taint compounds in four breeds of entire male pigs.
Breed
Duroc
Hampshire
Landrace
Yorkshire
16-androstene steroids (ug/g SG1)
57.3a
27.6b
27.5b
29.2b
16-androstene steroids (ug/g fat)
1.99a
1.16b
0.99b
0.99b
Skatole (ug/g fat)
0.14a
0.16b
0.15ab
0.12c
1 SG = salivary gland. abc Values within a row with shared superscripts are not significantly different (P < 0.05).

Table 3. Levels of boar taint compound in entire male pigs according to weight and age.

Least squares means1 of boar taint steroids in salivary gland (ug/g).
Duroc
Hampshire
Landrace
Yorkshire
Weight range
<105 kg
59.3
30.8
30.2
28.1
105-115 kg
56.6
25.8
26.9
28.6
>115 kg
61.7
31.6
26.8
30.4
Age range
<170 days
53.5
25.5
28.3
30.2
170-180 days
64.6
31.0
29.5
30.4
>180 days
70.4
30.3
30.8
30.1
1 s.e. of least squares means range from 3.8 to 6.2.

Least squares means1 of skatole in fat (ug/g).
Duroc
Hampshire
Landrace
Yorkshire
Weight range
<105 kg
0.145
0.136
0.150
0.125
105-115 kg
0.137
0.182
0.143
0.115
>115 kg
0.137
0.154
0.166
0.125
Age range
<170 days
0.137
0.164
0.151
0.121
170-180 days
0.147
0.147
0.146
0.124
>180 days
0.132
0.179
0.162
0.112
1 s.e. of least squares means range from 0.007 to 0.019.