Browsing by Author "Callahan, Stuart Russell"

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    Effects of group-size-floor space allowance during the nursery phase of production on future litter size and retention of sows through three parities
    Callahan, Stuart Russell; Cross, A. J.; DeDecker, A. E.; Lindemann, M. D.; Estienne, Mark J. (Oxford University Press, 2020-01-01)
    We previously reported that reduced floor space allowance caused by increasing the number of gilts per pen decreased growth and affected blood chemistry and immunology. The current objective was to determine effects of nursery group-size-floor space allowance on future litter sizes and retention in the breeding herd through three parities in sows. A 3 × 3 factorial arrangement of treatments was employed with 2,537 gilts classified as large (6.92 ± 0.06 kg), medium (5.60 ± 0.06 kg), or small (4.42 ± 0.06 kg), and placed in nursery pens of 14, 11, or 8 pigs to allow 0.15, 0.19, or 0.27 m2 floor space/pig, respectively. After the nursery and grow-finish periods, 1,453 gilts selected for breeding were relocated to one of 11 sow farms. Total litter size and pigs born alive increased (P < 0.01) with increasing parity and total litter size was 12.94, 13.28, and 13.99 (SE = 0.13) and pigs born alive was 12.21, 12.64, and 13.23 (SE = 0.11) for Parities 1, 2, and 3, respectively. There was a tendency (P = 0.08) for a quadratic relationship of group-size-floor space allowance and total litter size (13.39, 13.54, and 13.27 [SE = 0.13] for gilts allowed 0.15, 0.19, or 0.27 m2 floor space/pig, respectively). A linear effect of size of pig at weaning (P = 0.03) on pigs born dead was detected and was 0.64, 0.75, and 0.75, for small, medium, and large size pigs, respectively. There was no effect of group-size-floor space allowance on the percentages of gilts completing zero (P = 0.36), one (P = 0.35), two (P = 0.32), or three (P = 0.50) parities. In contrast, the percentage of small gilts that failed to complete one parity was greater (P < 0.05) and the percentage completing one parity (P < 0.05) was less than for either large or medium gilts. Abortion rate was greater (P < 0.01) in gilts classified as small (2.51%) or medium (1.36%) at weaning compared with those classified as large (0.20%). Size at weaning did not affect the proportion of gilts completing two (P = 0.88) or three (P = 0.72) parities. Group-size-floor space allowance during the nursery phase of production did not have remarkable effects on future litter sizes or retention in sows. Likewise, size of pig at weaning did not affect litter size and pigs born alive. Compared with larger pigs, however, more pigs classified as small at weaning and entering the breeding herd did not complete a parity and displayed a greater abortion rate.
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    Effects of nursery floor space allowance on growth, physiology, and immunology of replacement gilts
    Callahan, Stuart Russell (Virginia Tech, 2013-10-16)
    In U.S. swine herds, sow removal rates due to death and voluntary and involuntary culling exceed 50% annually. This loss poses an economic problem for producers because the cost of acquiring replacement females is great. Although research has shown that crowding in the nursery has negative impacts on growth, research describing effects of crowding on subsequent reproductive performance and longevity in sows is lacking. This experiment was conducted to determine the impacts of crowding during the nursery phase of production on growth, physiology, and immunology in replacement gilts. Gilts (22.3 ± 3.2 d of age and 5.6 ± 0.6 kg BW) were subjected to floor space allocations of 0.15, 0.19, or 0.27 m2/pig during a 7-wk nursery period. Floor space allocations were achieved by altering the number of pigs per pen (14, 11, and 8 gilts/pen, respectively). As was expected, reduced floor space allowance in the nursery negatively affected growth performance although there was inconclusive physiological and immunological evidence to suggest that pigs were experiencing highly stressful conditions. Although feed intake was not measured, changes in blood counts and blood chemistry for gilts allowed reduced floor space were similar to other studies that reported negative effects of crowding on feed consumption. Further study of the gilts involved in this study will aim to determine if there are any links between the effects of crowding during the nursery and subsequent reproductive performance and longevity in the breeding herd.
  • Immunological castration temporarily reduces testis size and function without long-term effects on libido and sperm quality in boars
    Clark-Deener, Sherrie; Lugar, Drew William; Rhoads, Michelle; Callahan, Stuart Russell; Prusa, Ken J.; Estienne, Mark J. (2016-10-27)
    The objective was to determine the effects of immunization against gonadotropin releasing hormone on reproductive characteristics in boars. Seventy-two boars were used in a randomized design with three treatments: single immunization (SI) or double immunization (DI) with Improvest® (Zoetis Animal Health, Florham Park, NJ, USA) and intact controls (no Improvest®; CNT) (n = 24/group). At 10, 15, 20, 25, and 40 wk of age, blood was collected and serum harvested to evaluate testosterone concentrations. Testosterone concentrations were less for DI boars compared to CNT boars and SI boars at 20 and 25 wk (P < 0.001), but not 40 wk of age. At wk 25, 18 pigs (n = 6/ group) were sacrificed and testes were removed, weighed, and measured and seminiferous tubules were examined and scored using histological slides of testes parenchyma. A sample of backfat was assessed for boar taint aroma. All testicular measurements and weights and seminiferous tubule scores were less for DI boars compared to SI and CNT boars (P < 0.001). More (P < 0.05) SI and CNT boars had detectable boar taint aroma than DI boars. Libido was assessed at 32, 36, 47, 60, and 63 wk of age and semen collected at 60 wk of age was analyzed for indicators of quality. There was no treatment effect (P = 0.41) on libido. Semen volume, gel weight and total number of sperm cells were not different among treatments. Sperm concentration was greater for DI than SI (P = 0.01), and tended to be greater for DI compared to CNT (P = 0.10). Sperm motility tended to be greater for DI boars compared to CNT boars (P = 0.066). The results show that there are no permanent effects of immunocastration on reproductive characteristics in boars.