The objective of this study was to investigate the relationships among birth weight, birth order, or litter size on growth performance, carcass quality, and eating quality of the ultimate pork product. Data were collected from 98 pig litters and, with the addition of recording birth weight and birth order, farrowing and piglet management were according to normal barn practices. In the nursery and during growout, the pigs received the normal feeding program for the barn and, with the addition of individual tattooing, were marketed as per standard procedure. From 24 litters, selected because they had at least 12 pigs born alive and represented a range of birth weights, 4 piglets were chosen (for a total of 96 piglets) and sent to Agriculture and Agri-Food Canada-Lacombe Research Centre (Lacombe, Alberta, Canada) when they reached 120 kg for extensive meat quality and sensory analysis. Individual BW was measured at birth, on the day of weaning, 5 wk after weaning, at nursery exit, at first pull, and at the time of marketing. Litter sizes were divided into 3 categories: small (3 to 10 piglets), medium (11 to 13 piglets), and large (14 to 19 piglets). There were 4 birth-weight quartiles: 0.80 to 1.20, 1.25 to 1.45, 1.50 to 1.70, and 1.75 to 2.50 kg. Increased litter size resulted in reduced mean birth weight (P < 0.05), but had no effect on within litter variability or carcass quality (P > 0.05) when slaughtered at the same endpoint. Lighter birth-weight pigs had reduced BW at weaning, 5 and 7 wk postweaning, and at first pull and had increased days to market (P < 0.05). Birth weight had limited effects on carcass quality, weight of primal cuts, objective quality, and overall palatability of the meat at the same slaughter weight (P > 0.05). In conclusion, increased litter size resulted in decreased mean birth weight but no change in days to market. Lighter birth-weight pigs took longer to reach market. Despite some differences in histological properties, birth weight had limited effects on carcass composition or final eating quality of the pork when slaughtered at the same BW and large litter size resulted in more pigs weaned and marketed compared with the smaller litters. We concluded that based on the conditions of this study, other than increased days to market, there is no reason based on pig performance or pork quality to slow down the goal of the pork industry to increase sow productivity as a means to increase efficiency.
Understanding how energy is utilized by the pig, and how the pig responds to changes in dietary energy concentration, is essential information in determining the optimal concentration of dietary energy under farm conditions, which are often highly diverse. The objective of these experiments was to determine how changes in dietary DE concentration, achieved through graded changes in diet composition, would affect the performance and carcass composition of growing pigs. In Exp. 1, which was conducted in a research facility, 300 pigs (31.1 +/- 2.6 kg) were assigned to diets containing 3.09, 3.24, 3.34, 3.42, or 3.57 Mcal of DE/kg. Experiment 2, which was conducted at a commercial swine farm, involved 720 pigs (36.8 +/- 5.9 kg) assigned to diets containing 3.12, 3.30, or 3.43 Mcal of DE/kg. Increased DE concentration was attained by using more wheat, soybean meal, and fat and less barley; true ileal lysine was adjusted as DE increased, and minimal AA:lysine ratios were maintained. In Exp. 1, ADG improved linearly as the energy content of the diet increased (P = 0.03). Feed intake decreased (P < 0.001) and feed efficiency and daily caloric intake improved (P = 0.005) with increased DE content. Variability in growth was not affected by treatment. Carcass index and LM thickness were not affected by increasing dietary DE content; backfat thickness, however, was increased (P < 0.001). In Exp. 2, overall ADG was unaffected by dietary energy content, although an improvement in growth was observed until the pigs reached approximately 80 kg of BW. Overall feed intake decreased with increasing energy content (P = 0.01), although this was not observed during the initial 6 wk of the experiment. Carcass index, lean yield, and backfat were not affected by increasing dietary energy content, whereas LM thickness tended to increase (P = 0.08). The value per pig was unaffected by increasing dietary energy content in both experiments, and returns above feed costs were reduced. Increasing the energy density of the diet for growing pigs through incremental changes in dietary composition had a variable impact on overall growth performance and carcass quality. Increasing the dietary DE had no effect on variations in BW at the time of marketing.
An experiment was conducted to determine the effect of ractopamine, energy intake, dietary fat level, and sex on performance and carcass composition in finishing pigs. Three hundred six barrows and gilts were used in a factorial arrangement of treatments replicated over three seasons. Treatments consisted of two ractopamine levels (0 vs 44.7 mg/d), two sexes (barrows and gilts), two levels of fat addition (0 vs 5% added fat), and four energy intake levels (8.3, 8.9, 9.5, and 10.1 Mcal of ME/d for barrows and 7.7, 8.3, 8.9, and 9.5 Mcal of ME/d for gilts). Diets were formulated to maintain an equal lysine (28.5 g/d) intake at each feeding level through cornstarch dilution of the basal (7.7 Mcal of ME/d) diets. Pigs were fed daily based on a standard feed intake curve and prior weekly body weights. At slaughter (104 kg), carcass measurements and TOBEC HA-1 scanner measurements were recorded. Dietary fat addition improved live weight and lean efficiency (grams of carcass lean gain/kilogram of feed, P < .05). Dietary fat addition did not affect growth rate or carcass composition. Increasing energy intake resulted in a linear increase in average daily gain for both barrows and gilts (P < .01). Dietary ractopamine influenced the response of lean tissue accretion, lean tissue accretion efficiency, and fat tissue accretion to energy intake. Pigs with no added ractopamine demonstrated increased lean tissue accretion and improved efficiency and decreased fat tissue accretion with increasing energy intake (up to 9.5 Mcal of ME intake for barrows and 8.9 Mcal of ME intake for gilts). In contrast, pigs with added ractopamine did not respond to increasing energy intake and demonstrated increased fat tissue accretion with increasing energy intake. The response to ractopamine for growth was greatest from d 6 to 22 on test or during the test gain period of 7 to 18 kg. After d 22, the response of ractopamine declined linearly. These results indicate that ractopamine increases growth rapidly at the onset of feeding until a plateau is reached, after which there is a linear decline in growth response.
Student-teacher anxieties are related to demographic variables, experiential variables, and dispositional variables.
The influence of a low and a high level chronic immune system (IS) activation on growth and dietary nutrient needs of pigs was evaluated. All pigs were of a single genetic strain and geographical site of origin, and the low and high IS pigs were created by physically isolating pigs from or continuously exposing pigs to major vectors of environmental antigen transmission. In each IS group, four littermate barrows in each of six litters were allotted at 25 +/- 2 d of age to one of four dietary amino acid regimens (.60, .90, 1.20, or 1.50% dietary lysine. Dietary lysine concentrations were achieved by altering the ratio of corn to soybean meal resulting in lysine being the first-limiting amino acid in each diet. Pigs were individually penned in facilities maintained at 25.6 +/- 2 degrees C and allowed to freely consume feed from 6.2 to 26.5 kg BW. On the basis of the differences in serological antibody titers, lymphocyte CD4+:CD8+ ratios, and serum alpha-1-acylglycoprotein concentrations, low and high levels of IS activation were established and maintained during the study. Minimizing the degree of chronic IS activation resulted in greater feed intakes (P < .09), body weight and protein gains (P < .01), gain:feed ratios (P < .01), and body leanness (protein:lipid, P < .01). The level of IS activation did not influence the partial efficiency of energy utilization for body protein and lipid accretion. To allow their greater capacity for body growth and protein accretion to be expressed, the low IS pigs required greater dietary lysine concentrations and daily lysine intakes than high IS pigs.
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