Lactation estrus induction in multi- and primiparous sows in an Australian commercial pork production system.

This study evaluated the effect of full physical boar exposure and split weaning on the incidence of lactation estrus within a large commercial piggery. A total of 299 multiparous (MP; parity 2.5 ± 0.03) and 303 primiparous (PP) sows of Large White × Duroc × Landrace genetics were individually housed in conventional farrowing crates from 1 wk before expected farrowing until weaning on Day 30.7 ± 0.05 postparturition. Before shed entry, sows were allocated randomly within parity to receive either boar exposure (BE; n = 454) or no BE (No BE; n = 149). Sows assigned to receive BE were then allocated to 1 of 2 litter size treatments: litter size unchanged (BE; n = 302) or BE and the litter permanently reduced (split weaned) to 7 piglets (BESPW7; n = 152) on Day 18 of lactation. From Day 18 of lactation until weaning, sows in both BE treatments were taken daily to a detection mating area where they received 15 min of full physical BE and were artificially inseminated at the first observed estrus. Providing sows with BE increased the incidence of lactation estrus, with a further increase observed when litter size was reduced to 7 piglets (16% No BE vs. 62% BE and 75% BESPW7; P < 0.05). Multiparous sows exhibited a greater incidence of lactation estrus than PP sows irrespective of treatment (81 compared to 52%, respectively; P < 0.05). Both MP and PP sows exhibited an increased incidence of lactation estrus when a portion of the litter was removed (MP: 76 vs. 89% and PP: 47 vs. 61%; P < 0.05). Farrowing rates were higher in BE MP sows mated postweaning and all BESPW7 sows mated postweaning when compared to their counterparts mated in lactation (P < 0.05). Percentage live weight loss over the course of lactation was greatest for sows in the No BE compared to the BE and BESPW7 treatments (7.7% ± 0.5 vs. 5.4% ± 0.3 and 4.5% ± 0.4, respectively; P < 0.05). Between Day 17 and weaning, piglets suckling sows in the BESPW7 treatment had a higher average weight gain than piglets suckling sows with a full litter (3.5 ± 0.06 vs. 3.1 ± 0.05 kg; P < 0.05). In conclusion these data suggest that providing MP sows with BE is effective at stimulating a synchronous lactation estrus while PP sows require, in addition to BE, a reduction in suckled litter size to 7 piglets.

Genetic mapping of quantitative trait loci for meat quality and muscle metabolic traits in cattle.

A whole-genome scan was carried out in New Zealand and Australia to detect quantitative trait loci (QTL) for live animal and carcass composition traits and meat quality attributes in cattle. Backcross calves (385 heifers and 398 steers) were generated, with Jersey and Limousin backgrounds. The New Zealand cattle were reared and finished on pasture, whilst Australian cattle were reared on grass and finished on grain for at least 180 days. This paper reports on meat quality traits (tenderness measured as shear force at 4-5 ages on two muscles as well as associated traits of meat colour, pH and cooking loss) and a number of metabolic traits. For meat quality traits, 18 significant QTL (P < 0.05), located in nine linkage groups, were detected on a genome-wise basis, in combined-sire (seven QTL) or within-sire analyses (11 QTL). For metabolic traits, 11 significant QTL (P < 0.05), located in eight linkage groups, were detected on a genome-wise basis, in combined-sire (five QTL) or within-sire analyses (six QTL). BTA2 and BTA3 had QTL for both metabolic traits and meat quality traits. Six significant QTL for meat quality and metabolic traits were found at the proximal end of chromosome 2. BTA2 and BTA29 were the most common chromosomes harbouring QTL for meat quality traits; QTL for improved tenderness were associated with Limousin-derived and Jersey-derived alleles on these two chromosomes, respectively.

Limousin myostatin F94L variant affects semitendinosus tenderness.

Texture parameters (peak force and compression), muscle myofibre diameter, and hydroxyproline were measured in semitendinosus samples from a cattle gene-mapping herd. The data were analysed to determine the relationships between these traits. The traits were also mapped by genetic linkage analysis to identify quantitative trait loci, and hence, candidate genes for these traits. Neither texture parameters were affected by the muscle structural traits of myofibre diameter or collagen content (as measured by hydroxyproline), despite significant variation in these traits between animals. QTL for the texture parameters of peak force and compression, as well as collagen content, were found on cattle chromosome 2 (BTA2) and attributed to the myostatin gene. Within the cattle population used for the QTL mapping, a gene variant of myostatin, F94L, has been previously shown to increase muscle mass, predominantly in the semitendinosus. It was determined herein that the F94L myostatin homozygous animals had more tender meat as measured by both peak force and compression. The variant was also responsible for a reduction in the collagen/elastin content of muscle. The myostatin F94L variant had no effect on muscle myofibre diameter of the semitendinosus, even though the variant causes substantial increases in muscle mass. Consequently, the increase in muscle mass of the variant must be due to myofibre hyperplasia and not hypertrophy. In addition, myostatin effects on tenderness are caused by changes in the extracellular matrix rather than muscle myofibre diameter.

Time course of metabolism of aldrin and dieldrin by suspension cultures.

Time course, up to 100d, of uptake and metabolism of aldrin and dieldrin added at subculture to suspension cultures from Phaseolus vulgaris (French bean) root and shoot, and Solanum tuberosum (potato) tuber comparable, with rapid dieldrin production and delayed appearance of other metabolites. When aldrin and dieldrin not added to Phaseolus cultures until 10 or 20d after subculture usual extent of conversion of aldrin to dieldrin, but reduced production of other metabolites, and growth inhibition negated. Increasing volumes of 2-methoxyethanol had detrimental effect on growth and uptake and metabolism. Dieldrin production maximal during rapid growth phase and probably independent of other conversions.

Consistency of metabolism of aldrin and dieldrin in suspension cultures from Phaseolus vulgaris root.

Reproducibility of metabolism of aldrin and dieldrin in cell suspension cultures from Phaseolus vulgaris (French Bean) root, and effects of variations in hormonal supplementation and light, studied. Aldrin always converted to dieldrin, aldrin-transdihydrodiol, and other unidentified more polar metabolites, but not to dihydrochlordene-dicarboxylic acid. Dieldrin always converted to photodieldrin and more polar metabolites, but not to aldrin-transdihydrodiol. Metabolism reasonably consistent from one subculture to next, basically unaffected by alterations in medium tested, or by presence or absence of light. Variations observed quantitative rather than qualitative supporting validity of use of tissue culture in metabolic studies on xenobiotics. Photodieldrin shown to be a direct product of dieldrin metabolism and not the result of microbial or environmental interference.

Causes and effects of sample loss using a dry capsule injection method for the automated gas chromatographic analysis of pesticide samples.

The automatic capsule sampling system is said to have many advantages for accurate gas chromatographic analysis. One is that the solvent may be removed by evaporation before injection, so that no solvent peak is obtained to interfere with the separation. However, working with aldrin and dieldrin, we have shown that up to 50% of the material can be lost from the capsules by air-drying at normal ambient temperature before injection. These losses occurred only with aldrin and it is suggested that they are connected with its relatively high vapour pressure. Significant amounts of material enter the top third of the capsule which is removed during the sealing process. The losses appear to be due to a combination of adsorption to the capsules, creep-up the capsule walls, co-distillation with the solvent, and direct volatilisation. Silylation of the capsules was quite effective in reducing these losses.