Identifying risk factors of slow growth of pigs from birth to marketing

Abstract Text: Pigs that grow significantly slower (slow-growing pigs) than their contemporaries may experience complication in animal welfare. Identifying risk factors of slow growth can help producers develop management strategies to mitigate this problem. The objective of this study was to evaluate factors associated with slow growth of pigs from birth to marketing. Risk factors evaluated included farrowing location (bedded group pens vs. crates), feeder space allowance during nursery (5 vs. 2 feeder spaces/pen of 8 pigs), dam parity (parity = 1 vs. parity > 1), total litter size born (≤ 14 vs. > 14), gender, weight at birth, weaning (4 wk) and nursery exit (9 wk). Pigs (n = 440) farrowed by 65 sows (parity = 1 to 7) were studied. Pigs were categorized as slow, average, and fast growers based on market weight adjusted to 170 d of age (slow growers < 105 kg, average growers between 105 and 125 kg, and fast growers > 125 kg). The Mixed Procedure of SAS with repeated measures was used to compare the growth performance from birth to marketing among the pig categories. The Logistic Procedures were used to identify risk factors of slow growth. Slow growers accounted for 10%, average growers for 49%, and fast growers for 41% of pigs marketed. On average, slow growers needed an extra 20 d to reach the target market weight of 115 kg compared with fast growers. Pigs that were lighter than the 30^th percentile at birth (≤ 1.36 kg), at weaning (≤ 6.4 kg), and at nursery exit (≤ 20.0 kg) were 4 (odds ratio, Confidence Interval (CI) = 2.0 to 6.6; P < 0.001), 6 (CI = 3.0 to 10.3; P < 0.001), and 18 times (CI = 7.9 to 39.9; P < 0.001), respectively, more likely to become slow growers. Compared with barrows, gilts (odds ratio = 2.2, CI = 1.2 to 4.0; P = 0.01) were more likely to become slow growers. Less feeder space allowance (odds ratio = 1.8, CI = 1.0 to 3.3; P= 0.05) during the nursery period was a risk factor for slow growth. Litter size, dam parity, or farrowing location was not associated with slow growth. These results suggest that light BW before nursery exit, gender, and feeder space allowance during the nursery period are risk factors of slow growth. 

Keywords: pigs, risk factors, slow growth