AGE RANGE AND SOW BODY ARE STILL KEY FACTORS

By Dan Bussieres, Groupe Ceres Inc.

As most swine producers know, gilts are the foundation of all sow herds, and thus all aspects related to gilt development prior to entrance into the herd are important.

Many different recommendations are found in swine literature and in the field regarding the “ideal” stage of first breeding. It is not clear whether this comes from different characteristics of the genetic lines or from the fact that age, body weight and degree of fatness (measured by the back fat thickness) are interrelated. A number of parameters need to be taken into account and the interactions between each of them and the gilt performance and longevity need to be determined. Besides the genetic component of the female, the plane of nutrition and growth pattern is suspected to be a major contributor that will influence those parameters.

Data for all gilts was entered into PigCHAMP software. Data were extracted and imported into an excel file for data analysis and statistical analysis were done using the Statistix software model,

HyLife is Canada’s largest swine producer. HyLife conducted a thorough analysis of the impact on breeding age, weight at breeding, and back fat at breeding on gilt lifetime performance. The analysis was conducted on the Fast Genetic 276 female line, from a 1200 sows unit within the HyLife production system.

All Fast Genetic 276 gilts that entered the sow barn between June 2005 and June 2010 were included in this data set. Monitoring was done throughout the Q-Barn period and during the whole productive life until the female was either cull or died. Sows that were still in production were not included in the data set. On total, over 2000 sow lifetime records were collected.

At breeding, all gilts had their back fat measured using an Ultra Scan Noveko device with a lineal probe. The back fat was measured and the P2 site (last rib and 2.5 inches from the median line). At the same time, gilt weight was recorded by weighing the gilt individually and the age of the gilt was noted.

Data for all gilts was entered into PigCHAMP software. Data was extracted and imported into an excel file for data analysis and statistical analysis were done using the Statistix software model.

RESULTS

For each of the body condition traits, we looked at the impact on litter size (total born) average over each parity and also at the average number of parities completed during the female life cycle. Using both litter size and the average parity per traits class, we calculated the lifetime female productivity. For the needs of this article we will only present the lifetime productivity data for each of the breeding traits.

EFFECT OF BACK FAT AT FIRST BREEDING

The gilts were divided in five back fat categories. Extremely thinner and fatter sows -- representing a low percentage of the gilt in the data-set were excluded from the analysis.

BACK FAT VERSUS LIFETIME PRODUCTIVITY AS TOTAL BORN

Overall results showed an average of 58.99 piglets total born lifetime. Back fat class positively influences (P<0.01) lifetime TB piglets. One class difference (+3 mm) improves lifetime TB by 3.7 piglets. The low correlation coefficient (R2 = 0.14) indicates that BF may not be the only contributing factor of the overall sow productivity.

BACK FAT AT BREEDING VS. AGE

Increasing age at first breeding increased back fat thickness (P<0.01). Within each BF class, large differences in age of females at first breeding exists, as shown by the low correlation coefficient between BF at breeding and age (R2 = 0.22). This means that as back fat at first breeding has an impact on lifetime performance, it does not necessary mean a swine producer needs to raise a heavier and older gilt in order to achieve a higher back fat level. As within each age category, there is variation in gilt back fat level. When breeding gilt to an older age and heavier weight it is important to consider the significant consequences on their production as you will see in the following part of the article.

EFFECT OF AGE AT FIRST BREEDING

Age at breeding was divided in six different age class categories, each spanning a 14-days age spread.

AGE VERSUS LIFETIME PRODUCTIVITY AS TOTAL BORN

The analysis of variance shows a non-significant effect of age class at first breeding on lifetime TB (P<0.60). The graph shows that productivity is maximum for the 229-243 day class, and nearly as good for the 215-229 day class as for the 243-257 day class. Regressed linearly over all age classes (from less than 201 up more than 284 days), age class affects negatively TB by 0.92 per each age class (P<0.07).

EFFECT OF BODY WEIGHT AT FIRST BREEDING

For the body weight at breeding, we divided the weight classes into five different weight categories each of them within a 15

BW AT FIRST BREEDING VERSUS LIFETIME PRODUCTIVITY AS TOTAL BORN

The influence of body weight class at first breeding on lifetime TB is significant (P<0.04) when calculated across all BW classes. Gilts in the 145-160kg class perform the best, though not significantly as per the Tukey test results; those of the two extreme classes show a numerically lower productivity level.

AGE AT FIRST BREEDING VERSUS BODYWEIGHT

Revisiting breeding age and breeding weight impact on lifetime productivity considerations, we should consider whether best age at breeding for lifetime productivity matches with the best weight at breeding.

The graph below shows that for the targeted age class at breeding of 229-243 days, the average breeding weight should be about 156 kg. This is, therefore, in line with the observed lifetime performance that were optimized when gilt were bred in the 145-160 kg weight range.

DISCUSSION AND CONCLUSIONS

The major findings of this evaluation are as follows.

Adiposity level (as estimated by the back fat thickness) at first breeding has a major influence on lifetime productivity expressed as total born. A positive influence is seen up to the 20-23 mm class. This finding is contrary to the common recommendation specifying a maximum level of back fat, which would suggest a detrimental effect of a certain degree of adiposity. On the other hand, although back fat will increase as weight and age of the gilt increase, there are still large variations in back fat levels within female of each age and weight class categories.

Adiposity level at first breeding has a major influence on lifetime productivity expressed as total born...This finding is contrary to the common recommendation specifying a maximum level of back fat, which would suggest a detrimental effect of a certain degree of adiposity.

Age at first breeding was not found to influence any major productivity parameter. Too young an age of gilts (as in the 201-215 day class) is linked to smaller litters than older ages of females. Longevity does not differ between age classes except for gilts older than 243-257 days. Productivity is maximized for the 229-243 day class.

Body weight at first breeding maximizes lifetime productivity for the 145-160 kg classes although no major differences were found when looking at the previous weight classes (130-145 kg).

Following this evaluation, practical recommendations on ideal stage at first breeding for Fast 276 gilt have been identified.

• Age range: minimum 210 with ideally an average breeding age of 225-250 days
• Sow body weight should be then in the 145-160 kg range with a minimum weight at breeding of 135 kg.
• In terms of lifetime average daily gain, at the targeted breeding weight and age, we would expect the gilt to present a lifetime ADG of 600 to 700 g/day. This would represent for the gilt developer period from 28 kg and above, an ADG of 700 to 850 g/day.
• For the back fat level, we recommend selecting the fatter sow within the appropriate age and weight group. With the current Fast sow female and with proper nutrition and growth during the gilt development, average back fat at breeding should be in the 14-20 mm range with an average of 15-16 mm.

Age at first breeding was not found to influence any major productivity parameter.

This study was vital for HyLife in determining the impact on breeding age, weight at breeding, and back fat at breeding on gilt lifetime performance.

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DAN BUSSIERES Dan has been involved in swine nutrition and research since his career began. He graduated from Laval University, Quebec in 1996 with a degree in Animal Science and worked for feed and genetic companies until 2004. Dan became a co-owner of Groupe Ceres Inc. in 2005. The company provides nutrition service, genetic sales, feed supply sales and pork production primarily in eastern Canada. As a consultant, Dan oversees the nutrition and R&D departments for Canada’s largest swine producer, HyLife, based in Manitoba.

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