The shift to group-housing of the breeding herd makes it difficult to manage animals individually. To maximize sow longevity and reproductive performance, gilts must be bred on second heat weighing between 135 and 160 kg. As gilts are typically fed ad libitum (AD), they often exceed targeted breeding weights, leading to structural and other problems resulting in culling at early parities. Thus, utilization of an electronic sow feeder (ESF) enables caretakers to manage animals individually in group-housing situations, by allotting predetermined amounts of feed. The specific objectives of this study were to: 1) to determine the effects of AD or restricted (RS) feeding bases (FB) on growth and sexual development in replacement gilts using an ESF; 2) to determine the growth and reproductive responses to gonadotropins in gilts fed on either AD or RS feeding bases using an ESF; and 3) to ascertain the effects of short-term increases in feed allowances on growth and sexual development in previously feed-restricted gilts using an ESF. Gilts employed in all studies were acclimated to an ESF (ACCUTEAM, Osborne Industries, Osborne, KS) beginning at 150 d of age, during a 10-d training period. Across all experiments, treatments were assigned at 160 d of age. In experiments 1 and 2, gilts received feed on either AD (5.00 kg/d) or RS (2.72 kg/d) bases. In the first study, estrus detection began at 160 d of age. In experiment 2, gilts assigned to receive gonadotropins were treated at 170 d of age, with estrus detection beginning the next d.
Gilts fed on the RS basis were observed to have improved feed conversion efficiency compared to AD-fed gilts in experiments 1 and 2 (both P < 0.01); and flushed gilts in experiment 3 had G: F similar to RS gilts. Average daily gain was not affected by FB in the first and third experiments, however AD-fed gilts gained weight at a faster rate (P = 0.02) than RS gilts in experiment 2. Gilts fed AD consumed their allotments across more meals than those fed RS. Age at puberty onset was not affected by FB in any of the experiments. Further, P.G. 600 did not hasten the onset of puberty, irrespective of FB in experiment 2. In experiment 3, ovulation rate was numerically greatest for flushed gilts, and was significantly greater than RS gilts (P = 0.05). The ovulation rate for flushed gilts was similar to AD gilts. Across all experiments, feed disappearance was observed to decrease as AD-fed gilts approached estrus. In this series of experiments, FB did not alter puberty onset, however ovulation rate was increased when gilts were allocated short-term increases in feed allowances. Further, utilizing an ESF may augment current industry estrus detection methods by monitoring feeding behavior. / Doctor of Philosophy / On commercial swine operations in the U.S. sow removal rates due to death and culling exceed 40% annually. On average, sows are culled at parity 3 or 4, while at least this many parities are required before investment costs are recouped. Gilts are typically fed AD until BW of 135 kg are attained by approximately 200 d of age. Oftentimes, gilts fed on AD basis exceed targeted breeding weights, leading to structural and other problems resulting in culling at early parities. To improve sustainability and competitiveness of pork production systems, the industry must focus on proper gilt management practices to facilitate successful entry into the breeding herd and increase longevity and lifetime performance as sows. A series of 3 experiments were conducted to evaluate different feeding bases on growth and sexual development in gilts. The first experiment evaluated the impact of AD or RS feeding on growth and sexual development in gilts using an ESF. Age at puberty was not different in limit-fed gilts. Limit-fed gilts also grew at a similar rate accompanied with improved feed conversion compared to AD fed gilts. Results from this experiment indicate that gilts can be limit-fed prior during the period around puberty until entering the breeding herd without negative impacts to growth or sexual development. In the second experiment, the same feeding bases were utilized, but within feeding basis groups, gilts either received or did not receive treatment with exogenous gonadotropins. Age at puberty was similar, regardless of feeding basis or gonadotropin treatment. Feed conversion was improved in limit-fed gilts, however daily gain was improved for gilts receiving feed AD. Results from this experiment imply that limit feeding gilts has no negative impacts on sexual development, but daily gain is reduced. In the third experiment, previous feeding bases were used, and a third, nutritional flushing, was also studied, when gilts received AD feed 7 d after first estrus. Flushed gilts had feed conversion like that of limit-fed gilts with daily gain similar to that of AD gilts. Gilts which were flushed had ovulation rates which were similar to gilts receiving feed AD but was greater compared with limit-fed gilts. Results indicate that flush feeding can achieve daily gain similar to ad libitum feeding and feed conversion similar to limit-feeding, while improving ovulation rate compared to limit-feeding. Across all studies, feed disappearance decreased for AD fed gilts as they neared estrus. Overall, using an ESF allows for precise feeding of replacement gilts and allows producers to implement various feeding strategies across multiple animals on an individual basis. Monitoring feed behavior with an ESF may enhance current estrus detection practices.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119288 |
| Date | 04 June 2024 |
| Creators | Niblett, Richard Tyler |
| Contributors | Animal and Poultry Sciences, Estienne, Mark Joseph, Ealy, Alan Dale, Clark-Deener, Sherrie Gayle, Barczewski, Richard Andrew |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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