Location: Livestock Issues ResearchTitle: Maternal heat stress abatement impacts physiology and performance of grazing Bos indicus-influenced beef offspring
|IZQUIERDO, VINICIUS - University Of Florida|
|SILVA, JOAO - University Of Florida|
|RANCHES, JULIANA - Oregon State University|
|SANTOS, GIOVANNA - University Of Florida|
|Carroll, Jeffery - Jeff Carroll|
|BITTAR, JOAO - University Of Florida|
|VENDRAMINI, JOAO - University Of Florida|
|MORIEL, PHILIPE - University Of Florida|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2023
Publication Date: N/A
Interpretive Summary: In dairy cattle, heat stress during late gestation negatively impacts offspring postnatal growth and immune function. The use of artificial shade is a management strategy that alleviates heat stress in environments with high temperatures and humidity. The effects of maternal heat stress and its impacts on offspring performance has not been reported for Bos indicus influenced-beef cattle. Therefore the main objective of this study was to evaluate the impact of maternal heat stress from 86 days prepartum until 47 days postpartum in Bos indicus beef heifers. Heifers had access or not to an artificial shade structure located centrally on their pastures. Data from this study showed that access to artificial shade reduced internal body temperature during the hottest hours of the day, decreased respiration rates, and increased body condition score from calving until the start of the breeding season. Also, calves born from heifers with no access to shade were lighter at birth but heavier at the end of the drylot period. Heifers with access to shade also had lower plasma indicators of inflammatory response and minor positive effects to humoral immune response to vaccination. These data will be of interest to researchers studying the impact of climate change on beef cattle production and to producers looking for ways to improve production and reduce stress in their beef cattle herds.
Technical Abstract: This study evaluated the growth and immune response of beef calves born from Bos indicus-influenced beef heifers provided pre- and post-partum heat abatement on pasture. On day 0 (83 ± 19 d prepartum), 64 Brangus crossbred beef heifers (20 to 22 mo of age) were stratified by body weight (BW; 454 ± 37 kg) and body condition score (BCS; 6.3 ± 0.28; scale 1 to 9), and then randomly allocated into 1 of 16 bahiagrass pastures (1 ha and 4 heifers/pasture). Treatments were randomly assigned to pastures (8 pastures/treatment) and consisted of heifers provided (SH) or not (NSH) access to artificial shade (4.5 m2 of shade area/heifer) from day 0 to 133. Heifers and calves were managed similarly from day 133 until the start of the breeding season (day 203). Calves were weaned at 119 ± 19 d of age (day 203), limit-fed the same drylot diet at 3.5% of BW (DM basis) day 209 to 268 (3 to 4 calves/pen; 8 pens/treatment) and vaccinated against respiratory disease pathogens on days 222 and 236. Heifer intravaginal temperatures from day 35 to 42 were lower (P = 0.03) for NSH vs. SH heifers from 0000 to 0800 h but greater (P = 0.05) for NSH vs. SH heifers from 1100 to 1800 h. Heifer intravaginal temperature from day 126 to 132 did not differ (P = 0.99) between NSH and SH heifers. Heifers assigned to NSH had greater respiration rates from day 20 to 96 (P = 0.0007), greater plasma concentration of cortisol on days 35 (P = 0.07) and 55 (P = 0.02), less plasma concentration of insulin-like growth factor 1 (IGF-1) on day 35 (P = 0.10), 55 and 133 (P = 0.05), and less BCS from day 55 to 203 (P = 0.01) compared to SH heifers. Calves born from NSH heifers had less birth BW (P = 0.05), greater overall plasma haptoglobin concentrations (P = 0.05), greater seroconversion against bovine respiratory syncytial virus on day 222 (P = 0.02), tended to have greater ADG from day 209 to 268 (P = 0.07), and had greater BW on day 268 (P = 0.05) compared to SH offspring. Plasma concentrations of cortisol and serum titers against other respiratory disease pathogens did not differ (P = 0.15) between NSH and SH offspring. Hence, maternal access to artificial shade: (1) lowered prepartum intravaginal temperature and plasma concentrations of cortisol but increased prepartum BCS and plasma concentrations of IGF-1 in grazing Bos indicus-influenced beef heifers; and (2) decreased post-weaning BW gain and had minor negative effects on humoral immune response of their offspring.