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Feeding Working Boars on a Commercial AI Stud

by 5m Editor
2 June 2009, at 12:00am

AI boars can be fed to a set feeding level to achieve targeted weight gains to influence longevity without affecting semen production and quality, reported R.C. Sulabo of the College of Veterinary Medicine of Kansas State University at Kansas Swine Day 2008.

Summary

The objective of the study was to determine the effects of two different feeding regimens on growth performance, semen production and quality, and longevity of boars in a commercial artificial insemination (AI) stud. A total of 30 replacement boars (PIC TR4, 375 lb and 14.2 months of age) were randomly selected and allotted to one of two treatments. The control feeding programme was the normal feeding programme of the stud; boars were fed 6.7 lb per day for the first eight weeks and then feeding was adjusted according to body condition of the individual boar. For the treatment feeding programme, boars were fed 5.8 lb per day in the first four weeks until boars reached 400 lb; afterward, boars were fed 6.0 lb per day for the duration of the study. Boars were weighed periodically to determine periodic and overall ADG. Semen was collected from each boar once a week for a total duration of 16 months. Semen production and quality was determined for each ejaculate.

Overall, treatment boars were consistently heavier than the control boars throughout the duration of the study because of their higher periodic and overall daily gains. At the end of the test, treatment boars were 32 lb heavier (P<0.15) than the control boars. A higher proportion of treatment boars (73 versus 42 per cent) were active at the end of the study, which numerically increased (P>0.35) average days in the stud (345 versus 279 days), semen collections (58 versus 49), and doses produced (1,238 versus 1,077). There were no differences (P>0.28) in the volume, sperm cell concentration, sperm cell count and doses produced per ejaculate between boars fed the two feed-ing programmes. Likewise, motility rates and proportion of normal cells in ejaculates were similar (P>0.33) between boars fed the control and treatment feeding programme.

In conclusion, AI boars can be fed to a set feeding level to achieve targeted weight gains to influence longevity without affecting semen production and quality.

Introduction

Despite the potential relationship between growth rate and reproductive performance, there is a lack of information on ideal growth rates of adult working boars. In previous studies, slow-growing boars fed at maintenance have shown significantly lower libido, semen volume and sperm output. On the other hand, providing boars with high levels of feed to achieve fast growth is thought to induce leg and libido problems. Rate of weight gain may also affect longevity and, therefore, lifetime semen production. Different feeding programmes can lead to varying rates of growth; however, different feeding regimens for AI boars have never been evaluated. Therefore, the objective of this study was to determine the effect of two different feeding regimens on growth performance, semen production and quality, and longevity of boars in a commercial AI stud.

Procedures

A total of 30 replacement boars (PIC TR4, 375 lb and 14.2 months of age) were randomly selected for this study conducted at the AI stud facilities of Zoltenko Farms, Inc., in Hardy, Nebraska.

Boars were allotted to one of two treatments in a completely randomised design; there were 15 boars (replicates) per treatment. The two experimental treatments were: (1) control and (2) treatment feeding programmes. The control feeding programme was the existing feeding programme of the stud. Upon entry to the stud, feed drops were set to 6.7 lb per day for the first eight weeks. After this initial period, feed box settings were adjusted periodically according to a subjective assessment of body condition of each boar throughout its lifetime in the stud. For the treatment feeding programme, boars were fed 5.8 lb per day for the first four weeks until boars reached 400 lb. Afterward, boars were offered 6.0 lb per day throughout the duration of the study.

In a previous study, it was determined that a 12 per cent overage was the average difference between feed box setting and the actual amount of feed dispensed in this specific stud. To provide the desired feeding levels for the treatment boars, feed boxes were set at 5.2 lb per day in weeks 0 to 4 and 5.4 lb per day throughout the rest of the study. The feed boxes for the control boars initially were set at 6.0 lb per day; however, because of the overage, the actual amount of feed presented to control boars was 6.7 lb per day in weeks 0 to eight and between 4.5 to 11.2 lb per day during the period when boars were fed according to body condition.

All boars were fed a corn-soybean meal-based diet with 10 per cent soy hulls, five per cent dehydrated alfalfa, and a boar base mix formulated to contain 0.79 per cent standardised ileal digestible lysine and 1,340 kcal ME/lb (Table 1). Boars were fed twice a day, and water was provided ad libitum. Boars were weighed periodically by using a platform scale to determine periodic and cumulative daily gains. Any adjustments of the feeder box settings during the study were also recorded. Total duration of the study was 16 months.

Semen was collected from each boar once a week on a dummy by using the hand glove technique with an average rest period of 5.3 days. The first collection was performed a week prior to the start of the experiment. For semen production, the volume of each ejaculate was measured immediately after collection. The concentration and number of sperm cells and the number of doses per ejaculate were also determined. Semen quality was assessed on the basis of sperm motility and the rate of normal cells per ejaculate. Each ejaculate was also evaluated for morphological defects such as distal and proximal droplets, loose heads, acrosome defects, pouch formations and abnormal mid-pieces. Semen collections were trashed for the presence of morphological defects, poor motility, bloody semen or sterility. Trashed collections (due to morphological defects) were recorded with the date and reason for trashing. Boars were removed according to the culling standards of the stud. The date and reason for culling were recorded. Because three of the boars in the control feeding programme were culled early because they were untrainable for semen collections, only 12 control boars were included in the analysis.

Data were analysed by using the GLM procedure of SAS for a completely randomised design with boar as the experimental unit. Treatments were separated by using the LSMEANS statement and the PDIFF option of SAS. An alpha level of 0.05 was used to assess the significance between least square means.

Results and Discussion

The effect of the two feeding programmes on live weight of boars in a commercial AI stud is shown in Figure 1. Boars on the control feeding programme were 2.1 per cent heavier (446 versus 437 lb) than the boars on the treatment feeding programme after the initial eight-week period. This was expected because control boars were provided 0.7 to 0.9 lb more feed and had greater daily gains (weeks 0 to 8: 1.14 versus 0.97 lb per day) during this period. However, control boars became lighter (week 14: 452 versus 464 lb) than the treatment boars immediately after the initial period. This change in the weight trend reflects the adjustment in the feeding programme when control boars were fed according to body condition. After week 14, boars on the treatment feeding programme were consistently heavier than the boars on the control feeding programme throughout the duration of the study. Treatment boars were significantly heavier (P<0.06) at weeks 18, 34 and 54. At the end of the test, treatment boars were 32 lb heavier (P<0.15) than the control boars.


Figure 1. Effect of different feeding regimens on live weight of boars in a commercial AI stud.
(Control = 6.7 lb per day for wk 0 to 8 and then fed according to body condition, Treatment = 5.8 lb per day for wk 0 to 4 and then 6.0 lb per day until end of the study).

Except from weeks 0 to 4 (Figure 2), boars on the treatment feeding programme achieved higher periodic daily gains as boars increased in weight from 400 to 500 lb (wk 4 to 24: 0.67 versus 0.55 lb per day) and 500 to 600 lb (wk 24 to 64: 0.33 versus 0.28 lb per day), though differences were not significant (P>0.32). Overall daily gains of treatment boars were numerically higher (P<0.39; 0.51 versus 0.46 lb per day) than those of boars on the control feeding programme. With the treatment feeding programme, boars showed a steady decline in daily gains from 0.84 lb per day in week 4 to 0.33 lb per day at week 64 (Figure 3).

The variation in weight gains of individual treatment boars is shown in Figure 4. At a constant feed box setting, weight gains varied from boar to boar in each period. This may reflect animal differences or daily variations in the actual amount of feed dispensed from each feed box. However, all of the treatment boars were on a positive plane of growth throughout the study.


Figure 2. Effect of different feeding regimens on periodic and overall daily gains of boars in a commercial AI stud
(Control = 6.7 lb per day for wk 0 to 8 then fed according to body condition, Treatment = 5.8 lb per day for wk 0 to 4 and then 6.0 lb per day until end of the study).

Figure 3. Effect of different feeding regimens on the pattern of growth rates of boars in a commercial AI stud
(Control = 6.7 lb per day for wk 0 to 8 then fed according to body condition, Treatment = 5.8 lb per day for wk 0 to 4 and then 6.0 lb per day until end of the study).

Boars on the control feeding programme showed a more erratic pattern of growth rates with wide swings in daily gains throughout the study (Figure 3). Boars on the control feeding programme had greater (P<0.14) ADG than the treatment boars from weeks 0 to 4 (1.04 versus 0.84 lb per day) and from weeks 54 to 64 (0.70 versus 0.33 lb per day). In contrast, control boars had lower (P<0.14) daily gains than the treatment boars from weeks 8 to 14 (0.31 versus 0.75 lb per day) and 28 to 34 (0.15 versus 0.46 lb per day).

These big changes in growth rates of the control boars suggest a cyclic pattern of increasing and decreasing feed allocation of individual boars to either reduce or compensate body condition (Figure 5). Boars were fed as much as 11.2 lb per day when they were below the farm’s acceptable body condition and as little as 4.5 lb per day when individual boars were believed to need to lose condition. At this low level of feeding, boars were potentially being fed close to or below their maintenance requirements. This also highlights another problem – the boar stud failed to account for the differences between the feed box settings and the actual amount of feed dispensed.


Figure 4. Variation in daily weight gains of treatment boars fed at constant feed box settings (5.8 lb per day at 375 to 400 lb and 6.0 lb per day at 400 to 600 lb BW)

Figure 5. Feed box adjustments of individual boars in the control feeding programme

It is important to check and account for these differences to accurately develop feeding programmes.

Using the factorial approach, the authors determined the predicted weight gains of the treatment boars on the basis of their actual feed allocation (Table 2). The estimated total energy intake of the boars was 7.8 Mcal ME/d in weeks 0 to 4 and 8.1 Mcal ME/d from weeks 4 until the end of the study. The total energy requirement of the treatment boars for maintenance, mating activity and sperm production increased from 5.86 Mcal ME at 376 lb to 8.03 Mcal ME at 607 lb BW. Therefore, the estimated ME difference for weight gain declined from 1.94 to 0.07 Mcal ME/d.

This shows that with the constant feed allocation at 5.4 lb per day, the total energy intake of the boars approached maintenance as BW increased from 376 to 607 lb. The predicted weight gains of the treatment boars declined linearly from 0.88 to 0.03 lb per day for the entire duration of the study.

The predicted weight gains of the treatment boars were plotted against their actual weight gains (Figure 6). The slope of the line for the actual weight gains (-0.0878) was 92.2 per cent of the slope of the predicted weight gains (-0.0952), which indicates close agreement. The actual weight gains of the treatment boars were slightly greater than the predicted weight gains, which may be due to (1) differences in the energy value of some of the ingredients (i.e., soybean hulls) accounted in the feed formulation, (2) variations in the actual amount of feed dispensed from the boxes, or (3) differences between the predicted and actual animal efficiencies.


Figure 6. Predicted and actual daily weight gains (lb per day) of treatment boars

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At the end of the 16-month study, a higher proportion of active boars (73 versus 42 per cent) were maintained in boars fed the treatment feeding programme (Figure 7). For the 10 control boars, five were culled because of poor semen quality, three were untrainable, one had a leg injury, and one died (identified as a twisted gut). All four boars culled from the treatment group were culled because of poor semen quality. Because there was a higher number of active boars maintained until the end of the test, boars under the treatment feeding programme had greater total production days (+55 per cent; 5,173 versus 3,345 days), semen collections (+47 per cent; 874 versus 593) and doses produced (+47 per cent; 18,569 versus 12,619) than the control group (Table 3). However, the average production days (345 versus 279 days per boar), number of semen collections (58 versus 49 collections per boar), and number of doses produced (1,238 versus 1,077 doses/boar) were only numerically improved (P>0.35) in boars fed the treatment feeding programme.

There were no differences between the two treatments in the total and average number of semen collections trashed. However, the percentage of trashed collections was higher in the control group than in the treatment group (8.3 versus 4.6 per cent). The rate of morphological defects in trashed collections from the control and treatment groups was the same, with distal and proximal droplets making up more than half of the trashed collections.

In terms of semen characteristics, there were no differences (P>0.28) in the volume, sperm cell concentration, sperm cell count and doses produced per ejaculate between boars fed the two feeding programmes (Table 4). In other studies, plane of nutrition was found to significantly affect semen volume, especially in young boars. However, these differences were obtained when comparisons were made between boars fed above and below their nutrient requirements, which is not the case in the present study.

Likewise, motility rates and proportion of normal cells in ejaculates were similar (P>0.33) between boars fed the control and treatment feeding programmes. These results are consistent with previous studies in which varying levels of feed or energy intake of boars did not influence any semen quality variable.


Figure 7. Effect of different feeding regimens on percentage of active boars in a commercial AI stud.
(Control = 6.7 lb per day for wk 0 to 8, then fed according to body condition, Treatment = 5.8 lb per day for wk 0 to 4 and then 6.0 lb per day until end of the study)



In conclusion, AI boars can be fed to a set feeding level to achieve targeted weight gains to influence longevity without affecting semen production and quality. Because many of the reasons for culling may not have been entirely due to feeding regimen, more research is required to validate that feeding regimen influences longevity of boars in the stud.

Further Reading

- You can view other papers presented at Kansas Swine Day 2008 by clicking here.


June 2009