Influence of Cross-fostering on Piglet Growth and Survival
However, it is important to implement cross-fostering correctly. When pigs are cross-fostered after 3-days of age, the disruption of the newly established teat order will likely result in reduced piglet weight gains and increase preweaning mortality. For this reason, it is usually recommended that cross-fostering be complete by 3-days after farrowing.
Further, survey evidence derived from PigCHAMP indicates that preweaning mortality is increased when greater than three piglets are fostered onto a sow. It is apparent that further work is warranted to examine the effects of cross-fostering on piglet performance.
A third sow served as a litter-intact control (I) and no pigs were cross-fostered. Cross-fostering was completed within 12-h of birth. Pigs were weighed again at 3-d and at weaning. Pig performance was assessed on the basis of survival and preweaning growth rate.
Comparisons were made between litter weight designations (H, L and I) and between H and the heavier half of intact litters (I-heavy) and between L and the lighter half of intact litters (I-light).
There was no significant advantage or disadvantage for cross-fostered pigs. Weight gain between days three and weaning was not affected by litter weight. Post-weaning ADG was not affected by litter weight. Patterns of preweaning survival were as expected with the heavier pigs having the least mortality and this was unaffected by cross-fostering. We conclude from these data that the creation of light birth-weight litters does not increase or decrease preweaning survival.
Heavy Light Intact I-heavy I-light Significance
Can We Make Sows Ovulate at the Time of Farrowing?
We injected sows with hCG at various times relative to farrowing and then determined whether sows had ovulated based on blood progesterone concentrations. A value greater than 5 nanograms (ng) of progesterone per mL of serum indicates ovulation. A value between 2 and 5 ng per mL suggests a partial effect and values less than 2 ng per mL indicates ovulation did not occur.
We initially treated 8 sows at 24 hours after farrowing. Based on blood progesterone concentrations 7 days after farrowing, none had ovulated.
We then injected a further 35 sows sooner after farrowing. This meant that if a sow farrowed overnight, she was treated immediately the next morning. If she farrowed during the day, she was treated last thing in the afternoon. Of these sows, 17 (48.6%) ovulated.
In an attempt to determine the best time to administer the hCG, we divided another 26 sows among the following treatments with the following results (Table 1).
These results demonstrate that the sow's ovulatory response to hCG at farrowing is far too unpredictable to be of commercial application.
Roy Kirkwood and George Foxcroft