Post-weaning body weights
The least square mean post-weaning body weights of the 50% LWY crossbred pigs and 75% LWY crossbred pigs at different ages are presented in Table 1. In general, the 75% LWY-25% Desi crossbred pigs recorded heavier body weights at all the ages compared to the 50% LWY-Desi crossbred. The exotic breeds weigh heavier than desi pigs
(Kumaresan et al., 2006). The heavier body weight of 75% LWY crossbreds can be attributed to more of exotic blood compared to 50% LWY crossbreds.
The period of birth had a significant effect on the body weights at 12, 20 and 28 weeks of 50% LWY crossbreds. However, the period of birth did not influence the body weights of 75% LWY crossbreds. The result suggests that improvement in management over the period could influence the performance of 50% LWY crossbreds whereas the managemental practices have no scope in increasing the production performance of 75% crossbreds. The season of birth was found to be significant on post weaning body weights in both the genetic groups. Piglets born in winter season recorded significantly higher body weights, which can be attributed to favorable effect of winter season as the exotic breeds were well acclimatized to the lower temperatures
(Naha et al., 2017).
The litter size at birth significantly influenced the post weaning body weights at all ages studied. The piglets belonging to smaller litter-sized groups recorded higher weights, probably because of increased share of milk and feed to the individual piglet. A highly significant (P<0.01) effect of parity on all post weaning body weights was observed. The second parity piglets had higher post-weaning body weights compared to primipara. Similar observation was made by
Toshimongla et al., (2020). Sex had significant effect (P<0.01) on post-weaning body weights and males were significantly heavier than females. The variation of body weights between different age groups and sexes might be due to the linearly increased body weight with the advancement of age, consequently increasing the metabolic activity and muscular, skeletal and reproductive growth
(Misiura et al., 2021).
Post-weaning average daily weight gains
The least squares mean ADGs of 50% LWY piglets and 75% LWY piglets during post-weaning period are presented in Table 2. The 75% LWY crossbreds showed higher ADGs. Similarly,
Das and Bhowal (2002) observed higher daily weight gains in Hampshire crosses. The period of birth has significant effect on ADG in certain ages in the two genetic groups but didn’t show specific trend. The season has significant effect at 12-16 and 20-24-weeks age in 50% LWY-crossbreds and 12-16 and 24-28 weeks in 75% LWY crossbreds but not during other stages of growth. Interestingly, the summer season showed higher ADGs, except for 12-16 weeks of age in 50% LWY-crossbreds. The higher ADGs in summer season could be attributed to the efficient heat stress managemental practices followed in the sheds
(Hyder et al., 2017). The litter size at birth influenced the ADG at most of the ages. The parity effect was significant in early post weaning age with piglets born in second parity recording higher ADG. Males recorded higher ADG than females in majority of the ages.
Heritability estimates
The heritability estimates for post-weaning body weights in 50% and 75% LWY genetic groups ranged from 0.38 to 0.56 and 0.30 to 0.53, respectively (Table 3). Results are consistent with the estimates reported by earlier research workers
(Ilatsia et al., 2008). Moderate to high heritability estimates obtained for body weights in the present study indicate the existence of adequate genetic variance and offered scope for improvement through selective breeding. Heritability estimates of ADGs in 50% and 75% LWY genetic groups ranged from 0.16 to 0.42 and 0.15 to 0.31, respectively (Table 4), which were well within the range of literature estimates of earlier studies
(Ilatsia et al., 2008 and
Bryan et al., 2019). The heritability of ADG during 12 to 16 weeks age could not be estimated in both the genetic groups because of sampling error. Heritability estimates for ADGs at majority of ages ranged from low to medium, indicating the existence of genetic variance, which could facilitate improvement through selection coupled with optimum managemental conditions.
Correlations
The genetic correlations among post-weaning body weight were mostly positive and ranged from 0.77 (BW24 with BW28) to 0.95 (BW16 with BW24) in 50% LWY and from 0.37 (BW12 with BW28) to 0.94 (BW16 with BW20) in 75% LWY genetic groups. Medium to high genetic correlations were also reported by
Ilatsia et al., (2008). The range of phenotypic correlations in 50% and 75% LWY was 0.46 (BW24 with BW28) to 0.86 (BW24 with BW28) and 0.58 (BW12 with BW28) to 0.89 (BW20 with BW24), respectively (Table 3). The results were in accordance with the findings of Das and Bhowal (2002). The genetic correlations among ADGs ranged from -0.45 (ADG 12-16 with ADG 16-20) to 0.67 (ADG 8-12 with ADG 16-20) in 50% LWY and from -0.63 (ADG 20-24 with ADG 24-28) to 0.66 (ADG 12-16 with ADG 16-20) in 75% LWY. The ranges of phenotypic correlations in 50% and 75% LWY were -0.23 (ADG16 - 20 with ADG 20-24) to 0.13 (ADG 8-12 with ADG 12-16) in 50% LWY and from -0.26 (ADG20 to24 with ADG 24-28) to 0.15 (ADG 16 to20 with ADG 24-28) (Table 4). The phenotypic and genetic correlations of ADGs were low in magnitude and inconsistent in direction. On contrary,
Das and Bhowal (2002) reported a higher phenotypic and genetic correlations among daily body weight gains in Hampshire crossbred pigs. The observed inconsistencies in genetic and phenotypic correlations could be attributed to the variation in the number of records
(Ilatsia et al., 2008).
