KSU Swine Day 2006: Predicting Boar Growth Rates

By R. C. Sulabo, J. Quackenbush, R. D. Goodband, M. D. Tokach, S. S. Dritz, J. M. DeRouchey, and J. L. Nelssen - This article is a collection of papers presented during KSU's Swine Day 2006.

8 January 2007

5 minute read

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Summary

There is almost no information on ideal growth rates for adult boars, but estimates can be made if the relationship between boar weight and age is known. Therefore, this study was aimed to predict growth rates in adult working boars in a commercial boar stud. A total of 214 adult working boars from two genetic lines in a commercial boar stud were individually weighed on a platform scale.

Age of the boar was recorded at the time of weighing. A regression equation to predict boar weight as a function of age was developed by using PROC REG of SAS. The model was used to predict BW on a daily basis, and ADG was derived as the difference between two predicted BW values. Factorial estimates of daily ME requirement and feeding rates were determined. The energy requirement for weight gain was computed by using the predicted ADG as a guide in setting target weight gains.

Results showed a positive curvilinear response (P<0.01) to describe the relationship between boar weight and age. Predicted ADG decreased in a curvilinear manner as the boars aged. In conclusion, on-farm growth rates can be predicted effectively by relating weight with age, taken from a representative number of boars in a given farm population. These data can then be used to develop farm-specific feeding programs or to set different growth curves for experimental purposes.

Introduction

Weight gain is inevitable in breeding boars because they enter the boar stud at a young age and light weight. It is typical for working boars to start their reproductive life between 300 and 350 lb, and gain more than 250 lb throughout their lifetime. The relationship between growth rate and reproductive performance of breeding boars may be important. In previous studies, slow-growing boars fed at maintenance have shown significantly decreased libido, semen volume, and sperm output.

On the other hand, fast-growing boars fed at high rates are thought to have increased leg and libido problems. Rate of weight gain may also have an impact on longevity, and thus affect lifetime semen production. But the ideal growth rate for adult working boars remains unclear.

This lack of information on growth rates of adult boars during their lifetime is a major challenge, but estimates can be made if the relationship between body weight and age of the boar is known. Moreover, predicting growth rates can be very helpful in developing appropriate feeding programs that can be used to set different growth curves. Therefore, this study aimed to predict growth rates in adult working boars in a commercial boar stud.

Procedures

A total of 214 adult working boars from two genetic lines (180 TR4 and 34 L-380 PIC, Franklin, KY) were used in this study. Boars were selected to obtain the widest possible range in age and weights. Boars were individually weighed on a platform scale, and age of the boar was recorded at the same time. Boars were fed and housed in a commercial boar stud according to standard procedures of the farm. Diets were not manipulated for this study. All boars were fed a corn-soybean meal diet with 10% soy hulls and 5% dehydrated alfalfa, formulated to meet or exceed suggested lysine and energy requirements.

A regression equation to predict boar weight by using age of the boar was developed by using PROC REG of SAS. This model was used to predict BW for a specific age on a daily basis. Then, ADG was derived as the difference between consecutive predicted BW values. The ADG for a specific weight range is computed by taking the average of the predicted ADG of the lowest and highest value of the weight range desired.

Daily ME requirement (Mcal ME/d) and feeding rates (lb/d) under thermoneutral conditions were estimated by using the factorial approach. Requirements for maintenance, weight gain, mating activity, and sperm production were individually determined by using regression equations, and were added to estimate total daily ME requirement. The energy requirement for weight gain was determined by using the predicted ADG as a guide in setting target weight gains.

The accuracy of feed drops in the facility was previously tested, and an average of 12% overage from the desired feed setting was determined. This was then used to adjust the feed box setting to obtain the desired feed allocation for each weight range. Finally, a phase-feeding program for adult working boars was developed from the estimates for daily ME requirement.