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Impact of Light, Temperature on Gilt Health, Reproduction

The goal of modern commercial swine production is to optimize reproduction while balancing for limitations in labor, costs and animal well-being

The goal of modern commercial swine production is to optimize reproduction while balancing for limitations in labor, costs and animal well-being.

Despite best management practices, unexplained cases of reproductive and health failures occur, such as failure to express estrus, failure to establish or maintain pregnancy, failure to produce large litters and/or failure to maintain normal body measures associated with health and longevity.

It is not clear whether excessive variation in sow breeding and gestation environments contribute to these failures. These environments are designed to provide uniform temperature and lighting for the animals, but there are clear examples where variation in the temperature and lighting occur. This variation is often exacerbated by season, the breeding female's location in the building, and her proximity to equipment, such as lights, fans, heaters and cooling cells.

This study was designed to test whether significant variation in the temperature and lighting of the sow microenvironment is associated with deterioration in animal reproduction and health.

The experiment was performed in multiple replicates throughout the year using three identical rooms with animals housed in individual stalls. Temperature and light intensity were controlled and each room was divided by a black, opaque curtain to create two different lighting sections.

In the study, 126 gilts were randomly assigned by weight to one of three temperature levels — COLD (55°F), thermal neutral or TN (69°F) and HOT (86°F), and lighting intensity at pig level designated as DIM (<50 lux) and BRIGHT (>350 lux).

All gilts were estrous synchronized and on the last day of MATRIX (Intervet) feeding were moved to their respective treatments. Estrus detection and real-time ultrasound were performed daily and artificial insemination (AI) occurred at first standing estrus and 24 hours later. Trans-rectal real-time ultrasound was used to determine follicular development, ovarian abnormalities and the estrus-to-ovulation interval. Blood samples determined if ovarian function and hormone production were affected by treatment.

For measures of well-being, all animals were evaluated weekly for feed intake, body temperature and weight gain during the treatment period. A subset (12 gilts/treatment) was assessed for measures of animal health, including plasma cortisol, neutrophil phagocytosis, lymphocyte proliferation and whole blood differential. Samples were taken for baseline measures two days prior to entry into the treatment rooms and then at -7, 0 (estrus), 7, 14, 21, and 28 days of the experiment. On Day 30 of gestation, all gilts were sacrificed to evaluate ovarian, pregnancy and litter size responses to treatment.

Most measures of reproduction were not significantly affected by the main effects of temperature and lighting or their interaction and included (Table 1): expression of estrus, estrus-to-ovulation interval, progesterone at Day 14 of pregnancy, ovulation rate, fetal weight (12.2 g) and fetal length (45.4 mm).

Duration of estrus was affected by lighting and was longer in BRIGHT (60.6 hours) compared to DIM (55 hours) lighting (Table 1). There were numerical trends for TN and HOT to increase pregnancy rates compared to COLD, and for HOT to have larger litter size compared to TN or COLD.

Weight gain during treatment was affected by temperature. Gilts in COLD gained less weight than animals in TN and HOT (Table 2). Cortisol, a physiological measure of stress, was greater in gilts kept in COLD than those kept in TN or HOT treatments.

Phagocytosis, which measures the ability of neutrophils to engulf and degrade potential disease-causing agents and prevent infection, was not affected by temperature or lighting. Lipopolysaccharide-induced, but not concanavalin A-induced, proliferative response of lymphocytes was greater among gilts kept in BRIGHT (1.55) compared to DIM (1.15) treatments (Table 2). Lymphocyte proliferation is an indicator of the capability to initiate an immune response from T or B cells against invading pathogens, and whole blood differentials show changes in the percentage of white blood cell types.

The percent of neutrophils and the neutrophil:lymphocyte ratio were higher among gilts kept in COLD (27.6%, 0.47) compared to those in TN (23%, 0.36) or HOT (21.8%, 0.33) environments. This shift to a higher number of neutrophils in comparison to lymphocytes in COLD treatment gilts is a result of the higher levels of cortisol in these animals.

The results of this study indicate that the normal variation in temperature and lighting encountered by animals in commercial breeding and gestation facilities do not interact or have little impact on key measures of early reproductive failure. However, for measures of well-being, housing females in COLD showed indicators of stress, and warmer temperatures might improve early measures of reproduction and lower cortisol levels.

Researchers: D. Canaday, A. Visconti, A. DeDecker, B. Yantis, J. Salak-Johnson and R. Knox, University of Illinois at Urbana-Champaign. Contact Canaday by phone at (815) 274-6967 or e-mail

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