Search
Author
Title
Vol.
Issue
Year
1st Page

Journal of Animal Science - Animal Nutrition

Effects of feeding regimen on weight gain, semen characteristics, libido, and lameness in 170- to 250-kilogram Duroc boars1

 

This article in JAS

  1. Vol. 94 No. 11, p. 4666-4676
     
    Received: July 09, 2016
    Accepted: Aug 22, 2016
    Published: October 27, 2016


    2 Corresponding author(s): jiangsiwen@mail.hzau.edu.cn
    pengjian@mail.hzau.edu.cn
 View
 Download
 Share

doi:10.2527/jas.2016-0803
  1. C. Wang*,
  2. J. L. Li†‡,
  3. H. K. Wei*,
  4. Y. F. Zhou*,
  5. J. J. Tan,
  6. H. Q. Sun,
  7. S. W. Jiang 2†§ and
  8. J. Peng 2
  1. * Department of Animal Nutrition and Feed Science, College of Animal Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
     Key Lab of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education & Key Lab of Swine Genetics and Breeding of Ministry of Agriculture, Huazhong Agricultural University, Wuhan 430070, China
     YangXiang Joint Stock Company, Guigang 537000, China
    § The Cooperative Innovation Center for Sustainable Pig Production, Wuhan 430070, China

Abstract

A 2-period field trial was conducted to determine the effects of feeding regimen on weight gain, semen characteristics, libido, and lameness in 170- to 200-kg (period 1) and 200- to 250-kg (period 2) boars. Sixty-one Duroc boars were allotted to 1 of 3 dietary treatments and 15 g/d fish oil was also provided for each experimental boar, to maintain the n-6:n-3 intake ratio at approximately 6.1:1. The energy intakes of the 3 treatment groups were controlled by basing the feed intake on a corn–soybean meal-based diet (3.11 Mcal/kg of ME) to create: 1) low energy intake group (L, n = 20, 7.3 Mcal/d of ME), 2) medium energy intake group (M, n = 20, 7.7 Mcal/d of ME), and 3) high energy intake group (H, n = 21, 8.3 Mcal/d of ME) in period 1. Feed intake was then increased to 7.6, 8.2, and 8.6 Mcal/d of ME for the 3 groups, respectively, in period 2. During the 28-wk experimental period, boar weight gain, testis volume, semen characteristics, libido, toe measurements, claw lesions, and lameness were examined, and the number of boars culled in each group was recorded to calculate the culling rate. Although there were no differences in testis volume, sperm concentration, and motility, the percentage of abnormal sperm, the percentage of claw lesions, and claw lesion scores differed among treatments (P > 0.05), and ADG was significantly increased with the increase of energy intake between the 2 periods (P < 0.05). The M and H boars had significantly greater total sperm number and functional sperm number than the L boars (P < 0.05), while no significant difference was observed between the M and H groups (P > 0.05). Nonetheless, the H boars took more time to mount the collection dummy and produce an ejaculate and, in particular, showed a greater percentage of lameness than the L and M boars (P < 0.05). Therefore, the medium energy intake regimen (energy intakes of 7.7 and 8.2 Mcal/d of ME with ADG of 454.5 and 375.3 g/d in 2 periods, respectively) improved the total sperm number and functional sperm number, and meanwhile decreased the occurrence of lameness in 170- to 250-kg Duroc boars.



INTRODUCTION

Sperm quality, libido, and lameness are related to the reproductive capacity and longevity of boars (Wilson et al., 2004; Koketsu and Sasaki, 2009) because these parameters are critical for the culling of boars at the age of 1 to 2 yr (Knox et al., 2008). It is noteworthy that boars culled because of lameness have a shorter longevity than those culled for other reasons (Koketsu and Sasaki, 2009). Therefore, improvements in sperm production and increasing boar longevity by decreasing lameness are of great importance for boar production.

The feeding regimen can affect boar weight gain, semen characteristics, libido, and lameness (Wilson et al., 2004). Evidence has shown that the semen volume and total sperm number of young boars (Brown, 1994; Hacker et al., 1994) and of adult boars (Kemp et al., 1989, 1991) are improved by increasing feed intake. However, boars fed ad libitum may grow too fast, becoming overweight, and are more likely to have foot and leg problems, which may shorten their lifespan and/or reduce their libido (Hacker et al., 1994; Jørgensen, 1995; Stern et al., 1995; Koketsu and Sasaki, 2009). Hence, debate remains regarding the ideal feeding regimen and growth rate for boars, particularly from introduction (usually at 7 to 9 mo old and 150 kg BW) to the period of stable fertility (at around 15 to 18 mo of age and ∼250 kg BW) because boars still need to grow during this period (Close and Cole, 2000; Kemp and Soede, 2001).

It has been hypothesized that an appropriate feeding regimen may improve sperm production and also decrease the occurrence of lameness by decreasing boar ADG from introduction to the stable fertility period. Therefore, the objective of this study was to investigate the effects of feeding regimen on boar weight gain, semen characteristics, libido, and lameness in this period.


MATERIALS AND METHODS

All animal handling protocols were approved by the Animal Care and Use Committee of the College of Animal Science and Technology, Huazhong Agricultural University (Committee of Science and Technology).

Boars, Facilities, and Boar Care

To evaluate the effects of feeding regimen on weight gain, semen characteristics, libido, and lameness in 170- to 250-kg boars, 61 just-trained Duroc boars with BW of 178.1 ± 1.9 kg and age of 9.1 ± 0.1 mo (means ± SEM) were selected for this study at Yaji Mountain AI Center of YangXiang Joint Stock Company, Guangxi province, China. The experimental boars were raised in stalls (0.79 by 2.40 m), which were fully slatted with concrete slats (90 mm solid width, 23 mm slots). Automated Production Systems, which included a positive pressure ventilation system, automatic feeding system, and heating system, were used to control the indoor environment (Automated Production Systems, Assumption, IL). The ambient temperature inside the house was maintained at around 18.8°C to 26.9°C during the test period. Extra light was provided when the natural photoperiod could not meet the daylight regime of 12 h of darkness and 12 h of lighting.

Diet and Experimental Design

This trial consisted of a single-factor completely random design and was performed from May 20, 2015, to December 10, 2015, with a 1-wk adaptation period from May 20, 2015, to May 26, 2015. The study was divided into 2 successive periods based on the BW of the boars: from 170 to 200 kg BW (period 1) and from 200 to 250 kg BW (period 2). The experimental diet used in this study was formulated on the basis of corn–soybean meal according to NRC (2012), and the ingredients and calculated values of the experimental diet are shown in Table 1. Three treatment groups were created according to a recommendation on weight gain for boars at different weights (Kemp et al., 1989; Kemp and Soede, 2001), and the energy requirements for each group were calculated by estimating requirements for maintenance, growth, mating activity, and semen production, as reported by Close and Roberts (1993) and Close and Cole (2000). The energy intakes of the treatment groups were as follows: 1) 7.3 Mcal/d of ME (low energy intake group, L, n = 20), 2) 7.7 Mcal/d of ME (medium energy intake group, M, n = 20), and 8.3 Mcal/d of ME (high energy intake group, H, n = 21) in period 1, and increased to 7.6 Mcal/d of ME, 8.2 Mcal/d of ME, and 8.6 Mcal/d of ME for each group, respectively, in period 2. Moreover, our previous study had indicated that a dietary n-6:n-3 ratio approximating 6.6:1 and 400 mg/kg vitamin E supplementation improved progressive sperm motility and antioxidant status (Liu et al., 2015). Therefore, 15 g/d fish oil was also provided to maintain the n-6:n-3 intake ratio at approximately 6.1:1, and vitamin E was mixed into the experimental diet before feeding. The FA composition of the fish oil (Nanjing Senhai Biological Oils & Fats Co., Ltd., Nanjing, China) included 10% eicosapentaenoic acid, 25% docosahexaenoic acid, and 35% total n-3 PUFA. The fish oil was stabilized with an antioxidant (500 ppm of butylated hydroxytoluene, Bayer China, China). Before the acclimatization period, all the selected boars were allotted to 1 of the 3 dietary groups according to their BW, age, and semen characteristics, and they were restricted to 2.0 kg/d of the same experimental diet during the adaptation period. From May 21, 2015, the energy intakes of the boars were controlled by providing feed intake to meet the energy level designed for each treatment group. The feed intakes of the boars were corrected every 2 wk on the basis of BW, and the boars were provided access to water ad libitum throughout the entire experimental period.


View Full Table | Close Full ViewTable 1.

Composition and calculated analysis of basal diet (as-fed basis)

 
Ingredient Content
Corn, % 58.31
Soybean meal, 43% CP 20.00
Rice bran meal, % 14.70
Soybean oil, % 3.00
Monocalcium phosphate, % 0.82
Ground limestone, % 1.32
Sodium chloride, % 0.30
Met, % 0.01
Vitamin E, % 0.04
Premix,1,2 % 1.50
Total, % 100.00
Calculated analysis
ME, Mcal/kg 3.11
CP, % 15.51
Lys, % 0.77
Met + Cys, % 0.55
Thr, % 0.59
Trp, % 0.18
Total Ca, % 0.83
Total P, % 0.73
Available P, % 0.31
1Supplied per kilogram of diet: 5 mg Cu, 80 mg Fe, 50 mg Zn, 20 mg Mn, 0.14 mg I, 0.30 mg Se, 15,000 IU vitamin A, 2,400 IU vitamin D3, 50 mg 25 (OH)D, 0.48 mg menadione, 2 mg thiamin, 7.2 mg riboflavin, 3.6 mg pyridoxine, 25 mg vitamin B12, 0.48 mg biotin, 25 mg pantothenic acid, 4 mg folic acid, 400 mg niacin.
2Premix was provided by Roche vitamins co., LTD, Shanghai, China

Body Weight, Testis Volume, and Toe Measurement

To investigate the ADG of the boars as well as the changes in testis volume and toe size, the BW and testis length and width were measured at wk 0, wk 8, and wk 29, while the toe sizes were estimated only at wk 0 and wk 29. A tape was used to determine the length and width of the paired testes, and the volume was calculated according to a formula described by Young et al. (1986). The toe length, toe width, horn height, and horn length of the inside and outside toes on the front and rear feet were measured, respectively, by referring to Calabotta et al. (1982) and Kornegay et al. (1983), using a digital vernier caliper with a measurement range of 0 to 150 mm (GuangLu Digital Measurement and Control Co., LTD, Guilin, China). The toe measurements of the front feet were made when the boars mounted the collection dummy, and the rear feet were measured during the night while the boars rested. All measurements were performed by 1 trained observer to avoid inter-observer variation.

Semen Characteristics and Libido

The semen collection of experimental boars were restricted between 0900 to 1130 h on different day, with a frequency of 3 times every 2 wk. Semen samples were collected from the boars at wk 0, wk 6, wk 8, wk 10, wk 12, wk 14, wk 16, wk 18, wk 20, wk 22, wk 24, wk 26, and wk 28 by the gloved-hand technique, and the gelatinous fraction was strained from the ejaculate through 4 layers of cotton-mesh gauze. The semen volume was measured by weighing each ejaculate and using the conversion formula of 1 g of semen being equal to 1 mL. A sperm density meter was used to estimate the sperm concentration of fresh semen (Fujihira Industry Co., LTD, Tokyo, Japan). Briefly, the fresh semen sample was sucked with a capillary, which was matched with the sperm density meter and then determined. The sperm concentration was evaluated 3 times by the same step for each semen sample. A phase contrast microscope (ML-210JZ; Nanning SongJinTianLun Biological Technology Co., LTD, Nanning, China) was used to examine sperm motility and sperm morphology. To determine sperm motility, the ejaculates were diluted 1:1 (vol/vol) immediately with isothermal Beltsville Thawing Solution (JinLi Livestock Equipment Co., LTD, Wuhan, China) and a 10-μL aliquot of the sperm sample was placed on a prewarmed (37°C) microscope slide and covered with a cover glass. Each slide was evaluated 3 times, and at least 5 microscopic fields of vision were examined by the same technician (Beorlegui et al., 1997). To examine sperm morphology, an eosin stain-dried method described by Kozink et al. (2004) was used, and sperm with head defects, neck and mid-piece defects, tail defects, and excess residual cytoplasm were counted using a bright field optical microscope at 400× (Shipley, 1999). The total sperm number and functional sperm number were calculated according to the formulae described by Smital et al. (2004) and Wolf and Smital (2009). When semen was collected, boar libido was evaluated by reference to a standard that was characterized by recording: 1) the time boars entered to first mount, 2) the time taken to start ejaculation, and 3) the duration of ejaculation at wk 0, wk 8, wk 19, and wk 28 (Louis et al., 1994a,b; Estienne et al., 2008).

Claw Lesions, Lameness, and Culling Rate

A scoring system based on the claw lesion scoring guide (Zinpro Corporation, Edina, MN) was used to estimate the claw lesions of the boars at wk 0,wk 8, wk 19, and wk 29 (Calderón Díaz et al., 2013). The lesion types included toe growth, dew claw, heel overgrowth and erosion, heel sole crack, white line, cracked wall horizontal, and cracked wall vertical. For each type, lesions were scored from 0 (no lesion) to 3 (severe lesion) depending on the severity, and the total score was calculated by summing the scores for all areas of all feet. Similar to the toe measurements, the front feet were inspected for lesions when the boars mounted the collection dummy and the rear feet were examined during the night while the boars rested. To evaluate locomotory ability, a scoring system from 0 (not lame) to 5 (severely lame) was used at wk 0, wk 4, wk 8, wk 12, wk 19, wk 23, wk 27, and wk 29 (Main et al., 2000). A new classification criterion that used 2 categories—normal (0 to 2) and lameness (3 to 5)—was used in this study to determine whether the boars were lame or not (Cador et al., 2014). During the entire experimental period, the boars culled from each group were recorded to calculate the culling rate.

Statistical Analysis

For data analysis, each individual boar was considered as an experimental unit and all analytical procedures were performed with SAS (version 9.2; SAS Inst. Inc., Cary, NC). The data were tested for normality and homoscedasticity by means of Shapiro–Wilk and Levene’s tests, respectively, before analysis. The square root [x], log10 [x], and arcsine square root [x] transformations were used when the distribution was not normal or was heteroscedastic. Data of body weight, testis volume, libido, and semen characteristics were analyzed using repeated-measures analysis of variance (Proc MIXED), and the fixed effects of diet, wk, and their interactions were included in this statistical model. When significant treatment differences were detected, the PDIFF option of the LSMEANS statement of the MIXED procedure was used to compare individual least squares means (Liu et al., 2015; Nemechek et al., 2015). The data on toe size measurements were analyzed statistically using the GLM procedure of SAS. The scores for claw lesions were tested using the Kruskal–Wallis test (Proc NPAR1WAY). Fisher’s exact test was performed to analyze the differences among treatments in the percentage of claw lesions and lameness (Quinn et al., 2015). In all statistical analyses, the significance level was set at 5%.


RESULTS

Body Measurements

As shown in Table 2, the H boars had a greater ADG (P < 0.05) than L boars, but there was no difference between M and L or M and H boars in period 1 (P > 0.05). In period 2, as well as in the entire experimental period (from 170 to 250 kg BW), the ADG significantly increased with the increase of energy intake (P < 0.01). Differences in testis volume among the groups were not significant in period 1, period 2, or the entire experimental period (P > 0.05; Table 2).


View Full Table | Close Full ViewTable 2.

Body measurements from boars with different feeding regimens

 
Treatment1
P-value
Item L M H SEM2 L vs. M L vs. H M vs. H
No. of boars 20 20 193
BW, kg
wk 0 178.5 178.4 179.4 5.7 0.99 0.85 0.84
wk 8 202.8b 205.8ab 210.7a 4.8 0.41 < 0.05 0.20
wk 29 249.6c 263.2b 274.0a 3.9 < 0.01 < 0.01 < 0.01
Testis volume, cm3
wk 0 1162.2 1244.0 1143.0 90.3 0.23 0.78 0.14
wk 8 1508.6 1644.3 1519.3 106.9 0.11 0.90 0.14
wk 29 1991.0 2140.0 2011.6 163.9 0.25 0.88 0.33
Period 1: from wk 0 to wk 84
ADG, g/d 398.4b 454.5ab 512.9a 44.5 0.18 < 0.01 0.12
Change in testis volume, cm3 346.3 400.3 376.3 69.7 0.34 0.60 0.67
Period 2: from wk 8 to wk 295
ADG, g/d 306.5c 375.3b 413.9a 22.5 < 0.01 < 0.01 < 0.05
Change in testis volume, cm3 482.4 495.7 492.3 121.1 0.89 0.92 0.97
Entire experiment period: from wk 0 to wk 296
ADG, g/d 332.7c 396.3b 442.1a 14.3 < 0.01 < 0.01 < 0.05
Change in testis volume, cm3 828.8 896.0 868.6 33.1 0.56 0.74 0.82
a–cLsmeans within a row with different superscripts significantly differ (P < 0.05).
1L = low energy intake; M = medium energy intake; H = high energy intake.
2SEM = Pooled SEM.
3Two boars were culled due to lameness in the H group.
4Period 1 was defined basing on BW from 170 to 200 kg.
5Period 2 was defined basing on BW from 200 to 250 kg.
6Entire experiment period was defined basing on BW from 170 to 250 kg.

Semen Characteristics

The semen volume, total sperm number, and functional sperm number of the M and H boars were significantly greater than those of the L boars (P < 0.05), and these parameters of the M boars did not differ from those of the H boars in either period (P > 0.05; Table 3). As shown in Fig. 1, there was an effect of time on semen characteristics (P < 0.01). The semen volume at wk 6 (P < 0.05), wk 14 (P < 0.05), and wk 28 (P < 0.01); the total sperm number at wk 14, wk 18, and wk 28 (P < 0.05); and the functional sperm number at wk 14 (P < 0.05) of the H boars were greater than those in the L boars. There was a slight tendency for an elevation of the total sperm number and functional sperm number at wk 6 (P = 0.06) and wk 28 (P = 0.09), respectively, in the H boars compared with the L boars. The M boars presented a greater semen volume at wk 28 (P < 0.01) and a greater total sperm number and functional sperm number at wk 14 (P < 0.05) than the L boars (Fig. 1). No significant dietary effect was observed for sperm concentration, sperm motility, and the percentage of abnormal sperm (P > 0.05; Fig. 2).


View Full Table | Close Full ViewTable 3.

Semen parameters from boars with different feeding regimens

 
Treatment1
P-value
Item L M H SEM2 L vs. M L vs. H M vs. H
Period 1: from 170 to 200 kg of BW3
No. of boars 20 20 21
Semen quality parameters
Semen volume, mL 142.1b 158.4a 156.7a 10.0 0.02 0.04 0.82
Sperm motility, % 83.6 84.2 83.9 1.1 0.48 0.71 0.75
Abnormal sperm, % 16.0 14.1 13.5 3.5 0.50 0.36 0.80
Sperm concentration, ×106/mL 226.8 229.8 247.9 13.1 0.46 0.06 0.24
Total sperm number, ×109/ejaculate 31.3b 36.0a 38.7a 3.0 0.02 < 0.01 0.40
Functional sperm number, ×109/ejaculate 22.0b 26.1a 28.0a 2.5 0.02 < 0.01 0.53
Period 2: from 200 to 250 kg of BW4
No. of boars 20 20 196
Semen quality parameters
Semen volume, mL 169.6b 184.0a 191.8a 10.7 0.04 < 0.01 0.35
Sperm motility, % 85.49 85.45 85.93 0.6 0.87 0.39 0.31
Abnormal sperm, % 13.43 13.83 12.90 2.4 0.94 0.74 0.68
Sperm concentration, ×106/mL 270.3 285.0 279.7 14.9 0.27 0.53 0.64
Total sperm number, ×109/ejaculate 45.3b 52.3a 53.3a 4.2 0.03 0.02 0.88
Functional sperm number, ×109/ejaculate 33.8b 38.8a 40.3a 3.6 0.04 0.03 0.69
Entire experiment period: from 170 to 250 kg of BW5
No. of boars 20 20 196
Semen quality parameters
Semen volume, mL 163.2b 178.1a 184.7a 9.5 0.03 < 0.01 0.37
Sperm motility, % 85.0 85.2 85.6 0.6 0.88 0.31 0.39
Abnormal sperm, % 14.0 13.9 12.8 2.4 0.87 0.47 0.57
Sperm concentration, ×106/mL 260.2 272.2 272.3 12.1 0.21 0.22 0.99
Total sperm number, ×109/ejaculate 42.1b 48.5a 50.5a 3.5 < 0.01 < 0.01 0.56
Functional sperm number, ×109/ejaculate 31.1b 35.8a 38.0a 2.9 < 0.01 < 0.01 0.42
a,bLsmeans within a row with different superscripts significantly differ (P < 0.05).
1L = low energy intake; M = medium energy intake; H = high energy intake.
2SEM = Pooled SEM.
3Period 1 was from wk 0 to wk 8.
4Period 2 was from wk 8 to wk 28.
5Entire experiment period was from wk 0 to wk 28.
6Two boars were culled due to lameness in the H group.
Figure 1.
Figure 1.

Effects of feeding regimen on semen volume (A), total sperm number (B), and functional sperm number (C) during a 28-wk period. Values were means ± SEM, n = 20–21. The lines represent data from boars on the L (dotted), M (dashed), and H (solid) groups. L, low energy intake; M, medium energy intake; H, high energy intake. The letters (A,B or a,b) show significant differences between any 2 groups, P < 0.01 or P < 0.05. NS represents no significance among treatments (P > 0.05).

 
Figure 2.
Figure 2.

Effects of feeding regimen on sperm concentration (A), progressive sperm motility (B), and the percentage of abnormal sperm (C) during a 28-wk period. Values were means ± SEM, n = 20–21. The lines represent data from boars on the L (dotted), M (dashed), and H (solid) groups. L, low energy intake; M, medium energy intake; H, high energy intake. NS represents no significance among treatments (P > 0.05).

 

Toe Measurements, Claw Lesions, and Lameness

The toe measurement data are shown in Table 4. Toe measurements for all areas of all feet were not significantly different (P > 0.05) among the treatments at wk 0, but the toe length, horn height, and horn length of H boars were greater at wk 29 than those of L boars (P < 0.05). Throughout the entire experimental period, the H boars had a greater growth rate, demonstrated by all toe measurements, than the L boars (P < 0.05), while these parameters for the M boars were not significantly different from those of the L and H boars (P > 0.05).


View Full Table | Close Full ViewTable 4.

Toe measurements of inside (I) and outside (O) toes on front (F) and rear (R) feet from boars with different feeding regimens

 
Treatment1
P-value
Item L M H SEM2 L vs. M L vs. H M vs. H
No. of boars 20 20 192
wk 0
Horn length, mm
FI 23.4 23.4 23.8 0.7 0.96 0.47 0.50
FO 25.0 25.8 26.1 0.9 0.26 0.14 0.71
RI 25.1 25.6 25.3 0.9 0.50 0.74 0.73
RO 28.5 27.3 28.8 1.3 0.26 0.82 0.18
Toe width, mm
FI 31.7 31.3 31.3 0.8 0.58 0.60 0.98
FO 35.5 34.1 34.9 1.1 0.11 0.53 0.32
RI 30.3 29.1 29.4 1.0 0.14 0.30 0.67
RO 34.5 33.5 34.0 1.0 0.19 0.52 0.51
Horn height, mm
FI 36.1 37.3 36.1 1.2 0.22 0.99 0.22
FO 37.4 39.3 38.2 1.2 0.07 0.50 0.27
RI 40.9 39.9 40.2 1.6 0.45 0.58 0.84
RO 43.6 41.7 42.8 1.9 0.20 0.58 0.48
Toe length, mm
FI 50.3 51.9 51.6 1.4 0.08 0.18 0.67
FO 53.6 54.0 54.2 1.2 0.68 0.56 0.86
RI 54.1 54.4 55.0 1.4 0.75 0.43 0.63
RO 57.8 57.5 58.5 1.6 0.78 0.63 0.45
wk 29
Horn length, mm
FI 29.2c 30.2b 31.3a 0.4 < 0.01 < 0.01 < 0.01
FO 30.7c 32.1b 33.2a 0.6 < 0.01 < 0.01 < 0.05
RI 30.1b 31.0ab 32.0a 0.6 0.06 < 0.01 0.06
RO 32.9b 32.2b 34.5a 0.7 0.19 < 0.01 < 0.01
Toe width, mm
FI 38.1 37.6 38.5 0.8 0.36 0.51 0.27
FO 42.7 41.6 43.0 0.9 0.16 0.66 0.07
RI 34.3 33.9 35.0 0.8 0.61 0.30 0.13
RO 38.1 38.6 38.8 1.1 0.56 0.46 0.87
Horn height, mm
FI 42.4b 43.9a 43.6a 0.8 < 0.05 < 0.05 0.70
FO 44.9b 46.5a 46.3a 0.8 < 0.05 < 0.05 0.76
RI 46.0 46.0 46.2 1.2 0.99 0.83 0.82
RO 49.5 50.4 50.0 1.2 0.37 0.58 0.74
Toe length, mm
FI 56.7b 58.4a 59.2a 1.0 < 0.05 < 0.01 0.40
FO 60.2 61.1 61.4 1.3 0.38 0.29 0.77
RI 59.3b 60.7a 62.0a 1.0 < 0.05 < 0.01 0.12
RO 63.1b 65.0a 66.6a 1.2 < 0.05 < 0.01 0.14
Change in toe sizes (from wk 0 to wk 29)
Horn length, mm
FI 5.8b 6.8ab 7.5a 0.7 0.09 < 0.01 0.29
FO 5.7 6.3 7.1 1.1 0.49 0.11 0.36
RI 5.0b 5.4b 6.7a 0.7 0.34 < 0.01 < 0.05
RO 4.4 4.9 5.8 1.0 0.54 0.10 0.31
Toe width, mm
FI 6.5b 6.3b 7.7a 0.6 0.63 < 0.05 < 0.01
FO 7.2 7.5 8.1 0.8 0.65 0.18 0.36
RI 4.0b 4.8ab 5.5a 0.5 0.07 < 0.01 0.12
RO 3.6b 4.5ab 5.2a 0.9 0.32 < 0.05 0.59
Horn height, mm
FI 6.2b 6.6ab 7.5a 0.7 0.60 < 0.05 0.12
FO 7.4 7.3 8.2 0.8 0.78 0.24 0.15
RI 5.1b 6.1ab 6.7a 0.8 0.18 < 0.05 0.38
RO 5.9b 7.3ab 8.7a 0.9 0.08 < 0.01 0.07
Toe length, mm
FI 6.3b 6.5ab 7.6a 0.7 0.77 < 0.05 0.07
FO 6.6b 7.1ab 8.2a 1.1 0.59 < 0.05 0.23
RI 5.2b 6.3ab 7.0a 0.7 0.07 < 0.01 0.20
RO 5.3b 6.5ab 8.1a 1.3 0.24 < 0.01 0.13
a–cLsmeans within a row with different superscripts differ (P < 0.05).
1L = low energy intake; M = medium energy intake; H = high energy intake.
2SEM = Pooled SEM.

The findings for claw lesion and lameness are presented in Tables 5 and 6. Although the percentage of claw lesions and the claw lesion scores in the H boars were slightly greater than in the L and M boars, these 2 parameters were not significantly different among treatment groups (P > 0.05). Interestingly, the H boars had a significantly greater percentage of lameness than the L and M boars at wk 27 and wk 29 (23.8% vs. 0% and 5%, respectively; P < 0.05). In addition, 2 boars (9.5%, 2/21) were culled due to lameness from the H group, but no boars were culled (0%, 0/20) from the L and M groups.


View Full Table | Close Full ViewTable 5.

Scores of claw lesion from boars with different feeding regimens

 
Treatment1
Item L M H SEM2 P-value
wk 0 0.7 0.6 0.4 0.5 0.1087
wk 8 1.3 1.3 1.5 0.7 0.7249
wk 19 2.0 2.1 2.9 1.1 0.7101
wk 29 3.1 2.9 3.9 1.3 0.9125
1L = low energy intake; M = medium energy intake; H = high energy intake.
2SEM = Pooled SEM.

View Full Table | Close Full ViewTable 6.

The percentage of claw lesion and lameness, culling rate from boars with different feeding regimens

 
Treatment1
Item
L
M
H
No. of boars
20
20
21
Periods % n2 % n2 % n2 P-value
The percentage of claw lesion
    wk 0 40.0 8 30.0 6 19.0 4 0.3383
    wk 8 40.0 8 50.0 10 61.9 13 0.4055
    wk 19 55.0 11 60.0 12 66.7 14 0.7599
    wk 29 75.0 15 65.0 13 76.2 15 0.8314
The percentage of lameness
    wk 0 0.0 0 0.0 0 0.0 0
    wk 4 0.0 0 0.0 0 0.0 0
    wk 8 0.0 0 0.0 0 0.0 0
    wk 12 0.0 0 5.0 1 4.8 1 1.0000
    wk 19 0.0 0 5.0 1 4.8 1 1.0000
    wk 23 0.0 0 5.0 1 4.8 1 1.0000
    wk 27 0.0b 0 5.0ab 2 23.8a 5 0.0399
    wk 29 0.0b 0 5.0ab 2 23.8a 5 0.0399
Boar culling rate
From wk 0 to wk 29 0.0 0 0.0 0 9.5 23 0.3224
a–b% within a row with different superscripts differ (P < 0.05).
1L = low energy intake; M = medium energy intake; H = high energy intake.
2Numbers of boars within claw lesion of lameness in each group.
3The 2 boars culled due to lameness were used to calculate for the percentage of lameness.

Libido

As shown in Table 7, boars in the H group took more time to mount the collection dummy and produce an ejaculate than the L and M boars in period 1, period 2, and the entire experimental period (P < 0.05). The M boars took less time to mount the collection dummy and produce an ejaculate than the L boars in period 1 (P < 0.05), but there was no difference between the M and L groups in period 2 (P > 0.05). During the entire experimental period, there was a slight tendency for M boars to take less time to mount and produce an ejaculate when compared with the L boars (P = 0.06, P = 0.10, respectively). There was no difference in the duration of ejaculation among the treatments in period 1, period 2, and the entire experimental period (P > 0.05).


View Full Table | Close Full ViewTable 7.

Libido from boars with different feeding regimens

 
Treatment1
P-value
Item L M H SEM2 L vs. M H L vs. H
Period 1: from 170 to 200 kg of BW3
No. of boars 20 20 21
Boar libido
Time to mount firstly, s 47.5b 30.6c 64.4a 8.7 0.02 0.02 < 0.01
Time to ejaculation, s 145.3b 110.9c 173.4a 12.3 < 0.01 0.04 < 0.01
Duration of ejaculation, s 269.5 281.2 294.1 25.7 0.55 0.23 0.53
Period 2: from 200 to 250 kg of BW4
No. of boars 20 20 196
Boar libido
Time to mount firstly, s 83.6b 58.0b 136.9a 23.3 0.18 < 0.01 < 0.01
Time to ejaculation, s 200.7b 183.0b 286.1a 43.3 0.62 0.02 < 0.01
Duration of ejaculation, s 368.2 408.6 402.5 30.7 0.11 0.18 0.81
Entire experiment period: from 170 to 250 kg of BW5
No. of boars 20 20 196
Boar libido
Time to mount firstly, s 65.6b 44.3b 100.6a 13.5 0.06 < 0.01 < 0.01
Time to ejaculation, s 178.0b 146.9b 229.8a 23.5 0.10 < 0.01 < 0.01
Duration of ejaculation, s 319.9 344.9 348.4 23.5 0.17 0.13 0.85
a–cLsmeans within a row with different superscripts significantly differ (P < 0.05).
1L = low energy intake; M = medium energy intake; H = high energy intake.
2SEM = Pooled SEM.
3Period 1 was from wk 0 to wk 8.
4Period 2 was from wk 8 to wk 28.
5Entire experiment period was from wk 0 to wk 28.
6Two boars were culled due to lameness in the H group.


DISCUSSION

Given that the ideal feeding regimen and growth rate for boars remain controversial, particularly from introduction to the period of stable fertility, this study was designed to determine the appropriate feeding regimen for Duroc boars in this period. The results showed that, with increasing energy intake, the semen volume, total sperm number, and functional sperm number of boars were elevated, in parallel with the ADG. However, the percentage of lameness and the culling rate of boars were also increased by increasing the ADG.

Although a recommendation has been made that the ADG should be 500 and 400 g/d in 150- to 200-kg and in 200- to 250-kg boars, respectively (Kemp et al., 1989; Kemp and Soede, 2001), whether this is suitable for the modern lines of boars in regard to semen production and lameness remains unclear. The energy requirements for maintenance, growth, mating activity, and semen production in boars have been reported by Close and Roberts (1993) and Close and Cole (2000), and these can be adjusted to control the ADG (Wilson et al., 2004). Therefore, 3 groups, based on energy intake, were created to determine an appropriate feeding regimen and growth rate to improve sperm production and meanwhile decrease lameness in boars. The results showed that the ADG was 452.5 and 365.2 g/d, which was equivalent to 58.3 and 45.1 g/Mcal ME intake in period 1 and period 2, respectively, in the present study. Similarly, Louis et al. (1994b) reported that boars weighing 171.7 kg with an energy intake of 6.82 Mcal/d of ME had an ADG of 387 g/d, which was equivalent to 56.7 g/Mcal ME intake. When the BW of boars increased to 219 kg with an energy intake of 11.2 Mcal/d of ME, the ADG was increased to 516 g/d, which was equivalent to 46.1 g/Mcal ME intake (Kemp et al., 1989). This indicated that the ADG of boars at different stages of growth could be controlled by the levels of energy intake used in this study.

It is widely accepted that an increase of energy intake has a positive impact on semen volume and total sperm number in boars (Kemp et al., 1989, 1991; Brown, 1994) and rams (Oldham et al., 1978; Alkass et al., 1982), which may be because increased feed intake may increase the proportion of seminiferous tubular epithelium to testicle volume and the cross-sectional area of seminiferous tubules (Oldham et al., 1978). The H and M boars in the current study had greater semen volume, total sperm number, and functional sperm number than the L boars with the energy intake increasing from 7.3 to 8.3 and from 7.6 to 8.6 Mcal/d of ME in period 1 and period 2, respectively (including fish oil supplementation). Similarly, Kemp et al. (1989) reported that the total sperm number was increased significantly, from 89 × 109 to 130 × 109 cells per week, when the energy intake was increased from 5.9 to 11.2 Mcal/d of ME. This indicates that semen production may be improved by increasing energy intake.

However, increasing energy intake may lead excessively rapid growth, which causes boars to be overweight and more likely to suffer from foot and leg problems, which may shorten their lifespan (Jørgensen, 1995; Stern et al., 1995; Koketsu and Sasaki, 2009). The percentage of claw lesions and the claw lesion scores were greater in the H boars than in the L and M boars, but the differences in these 2 parameters were not significantly different among treatments in the present study, which is in agreement with a previous study by Quinn et al. (2015). This is presumably because boars raised in pens with concrete slatted floors are more vulnerable to claw lesions than those raised in stalls (Gjein and Larssen, 1995; Anil et al., 2005; Pluym et al., 2011). We found that the H boars, with greater ADG, had a greater percentage of lameness and culling rate than the L and M boars in this study, which was in line with a previous study that reported that a very high ADG (485 g/d) from 96 kg to first service was related to premature culling for lameness (Tarrés et al., 2006). The reason may be that excessively rapid growth of pigs increases the weight-bearing pressure on bones. Brennan et al. (1987) reported that the mild mechanical stress caused by a 15% increase in BW causes focal degenerative changes in young swine, which may predispose pigs to osteoarthrosis and osteochondrosis at maturity.

Additionally, the results showed that high energy intake increased the time taken by the boars to mount the semen-collection dummy and start ejaculating, which were measured to represent libido in this study. Similarly, boars on a greater plane of nutrition decease courting behavior activities that are associated with libido (Hacker et al., 1994). Conversely, other studies have suggested that energy intake has little effect on boar libido (Kemp et al., 1989, 1991). The differences between this study and that of Kemp et al. (1989, 1991) and Louis et al. (1994a) may be due to the different methods of evaluation (Mwansa and Makarechian, 1991) and different housing types used (Hacker et al., 1994), respectively.

In conclusion, the medium energy intake regimen (energy intakes of 7.7 and 8.2 Mcal/d of ME with ADG of 454.5 and 375.3 g/d in the 2 periods, respectively) improved the total sperm number and functional sperm number and meanwhile decreased the occurrence lameness by optimizing ADG in 170- to 250-kg Duroc boars, which may improve boar longevity.

 

References

Footnotes


Comments
Be the first to comment.



Please log in to post a comment.
*Society members, certified professionals, and authors are permitted to comment.