Daryl L. Kuhlers

Effect of dietary restrictions on growth performance and carcass quality of pigs selected for lean growth efficiency

Sixty-four pigs, 32 selected for lean growth efficiency and 32 controls selected randomly, were used to investigate the effect of genotype and realimentation diets on growth performance and carcass quality of pigs subjected to marginal dietary restrictions during the grower phase. When pigs weighed approximately 20 kg, 16 pens containing two gilts and 16 pens containing two castrated males were randomly assigned within genetic lines to grower diets and finisher diets in a 2×2×2 factorial arrangement of treatments. Grower diets contained 0.421 or 0.765 g lysine/MJ DE, whereas finisher diets contained 0.421 or 0.612 g lysine/MJ DE. Genotype had no effect on growth performance, but select line pigs had better carcass quality (P≤0.05) and seemed to utilize amino acids more efficiently for growth than control line pigs as indicated by lower blood urea nitrogen (P≤0.07). During the grower phase, pigs fed the high-amino acid grower diet grew faster and more efficiently (P<0.01) and had less ultrasound backfat (P<0.001) than those fed the low-amino acid diet. Although some grower×finisher diet interactions were observed, there was no indication that pigs subjected to early amino acid restrictions exhibited compensatory weight gain, or had different amino acid requirements in the subsequent phase. The rate of lean accretion was similar between pigs fed the low- and high-amino acid grower diets regardless of genotype, indicating that compensatory lean tissue growth may have occurred in pigs subjected to early amino acid restrictions. Furthermore, restricted pigs had better feed efficiency in the subsequent phase, which may have a positive impact on the environment by reducing the excretion of unutilized nutrients. Select line pigs fed the low-amino acid grower diet had lower overall weight gain compared with other groups (genotype×grower, P<0.001). The results imply that pigs selected for lean growth efficiency may be less tolerant of early amino acid restrictions, and offering a grower diet containing adequate amino acids might be important in optimizing overall growth performance.

Longevity and maternal productivity of F1 crossbred landrace sows managed in two different gestation systems

Longevity and maternal productivity of 83 Duroc-Landrace (DL), 86 Hampshire-Landrace (HL) and 87 Yorkshire-Landrace (YL) sows were evaluated. Half of the sows of each cross were penned by cross in pasture lots during gestation. The remaining sows were confined in individual-sow gestation stalls. The 3 crosses of sows were bred in all possible combinations to 16 Duroc, 19 Hampshire and 19 Yorkshire boars. Litter sizes and weights at birth, 21 and 56 days were summed across 4 parities for each sow to form maternal productivity variables for each stage of production. The 256 sows farrowed 844 litters. A greater percentage of HL sows confined in gestation stalls completed 4 lactations than confined YL sows (88.0 vs 69.8%, P < 0.10). In the pasture gestation system, more total live pigs were produced at birth, 21 and 56 days in 4 parities by DL (40.0, 32.5, 30.9) and HL (38.2, 30.9, 30.2) sows, respectively, than by YL (31.1, 24.7, 24.3) sows (P < 0.10). In the pasture gestation system, DL (66.3, 168.9) and HL (56.5, 159.0) sows produced more kilograms of litter weight at birth (P < 0.10) and 21 days (P < 0.05), respectively, than YL (45.6, 124.8) sows. Confined HL (173.6) sows produced more kilograms of litter weight at 21 days in 4 parities than confined YL (143.1) sows (P < 0.10). Results from this study indicate that the breed of crossbred sows used in a production unit should be selected for the type of gestation system used on the farm.

Growth of channel catfish (Ictalurus punctatus), blue catfish (I. furcatus), and their F1, F2, F3, and F1 reciprocal backcross hybrids in earthen ponds.

The F1 hybrid between a channel catfish female (Ictalurus punctatus) × a blue catfish (I. furcatus) male outperforms both parental species in most environments. However, reproductive isolating mechanisms between the species made it difficult to mass produce the F1 hybrid for commercialization until recent improvements in hormone usage. This study was undertaken to mix the genomes of the 2 species in an attempt to obtain faster-growing catfish that would eventually be easier to reproduce. Despite the recent improvements, it would still be advantageous to have an animal that does not require hormone dosing for reproduction and does not require the growing of 2 separate species by breeders. Additionally, a F1 backcross or a multigeneration backcross has the possibility of being an improvement compared to an F1 hybrid. At low density, there was no difference in growth between channel catfish and channel-blue F1 hybrids. At higher densities, the F1 hybrid grew faster (666 g) than channel catfish (577 g), blue catfish × F1 (520 g), F1 × F1 (508 g), F1 × channel catfish (436 g), blue catfish (396 g), F1 × blue catfish (379 g), channel catfish × F1 (359 g), and F2 × F2 (359 g; P < 0.05). The channel-blue F1 males were heavier than the F1 females. Individual heterosis had a strong positive effect on growth, whereas individual epistatic recombination loss had a strong negative effect on growth. The channel-blue F1 hybrid and blue catfish had low coefficients of variation, whereas the F2 and F3 hybrids had high coefficients of variation. This gives a high amount of variation for selection, which might be used to select the faster-growing catfish.