Effects of feeding an immunomodulatory supplement to heat-stressed or actively cooled cows during late gestation on postnatal immunity, health, and growth of calves

Abstract

Heat stress during late gestation negatively affects the physiology, health, and productivity of dairy cows as well as the calves developing in utero. Providing cows with active cooling devices, such as fans and soakers, and supplementing cows with an immunomodulating feed additive, OmniGen-AF (OG; Phibro Animal Health Corporation), improves immune function and milk yield of cows. It is unknown if maternal supplementation of OG combined with active cooling during late gestation might benefit the developing calf as well. Herein we evaluated markers of innate immune function, including immune cell counts, acute phase proteins, and neutrophil function, of calves born to multiparous dams in a 2 × 2 factorial design. Dams were supplemented with OG or a bentonite control (NO) beginning at 60 d before dry off and exposed to heat stress with cooling (CL) or without active cooling (HT) during the dry period (∼46 d). At birth, calves were separated from their dams and fed 6.6 L of their dams' colostrum in 2 meals. Calf body weight and rectal temperature were recorded, and blood samples were collected at birth (before colostrum feeding) and at 10, 28, and 49 d of age. Calves born to either CL dams or OG dams were heavier at birth than calves born to HT or NO dams, respectively. Concentrations of serum amyloid A were higher in the blood of calves born to OG dams relative to NO and for HT calves relative to CL calves. In addition, calves born to cooled OG dams had greater concentrations of plasma haptoglobin than calves born to cooled control dams. Neutrophil function at 10 d of age was enhanced in calves born to cooled OG dams and lymphocyte counts were higher in calves born to OG dams. Together these results suggest that adding OG to maternal feed in combination with active cooling of cows during late gestation is effective in mitigating the negative effects of in utero heat stress on postnatal calf growth and immune competence.

In Utero Heat Stress Alters the Offspring Epigenome

“…Most DEGs in these pathways were upregulated ( BLA-DQB, JCHAIN, DEFB, GRO1, HP ) in the mammary glands of IUHT-H compared to IUCL-H, although a couple were downregulated ( BOLA-DQB , BOLA ). These results are in concordance with immune deficits and elevated acute phase protein production observed among in utero heat stressed cattle 26 , 45 , 78 , but suggest that DNA methylation is not contributing substantially to regulation of immune-related genes in the mammary gland.…”

“…A recent proteomics analysis of the liver of periparturient cows heat stressed during late gestation found evidence of oxidative stress 17 . In the present study, genes contributing to superoxide metabolism, such as NOXO1 , GSTT1 , and SOD2 , were upregulated in the mammary gland of IUHT-H relative to IUCL-H. Higher levels of pro-inflammatory cytokines have been detected in peripheral blood mononuclear cells of heat stressed pregnant cows and in utero heat stressed calves have higher circulating acute phase proteins, whose production is induced by pro-inflammatory cytokines 45 , 46 . Together, these results suggest that altered DNA methylation patterns may contribute to heightened inflammatory responses and oxidative stress among in utero heat stressed cattle.…”

Heat Stress Impacts Immune Status in Cows Across the Life Cycle

“…Whereas, the reduced quality of colostrum collected during summer compared with colostrum collected during other seasons has been reported, the impact of late-gestation heat stress on colostrum IgG concentration has been inconsistent in controlled studies. Some studies have reported decreased IgG (53,54), others have observed no differences in IgG (51,55) or even increased concentrations of IgG (56) in the colostrum of heat stressed dams. Regardless of these conflicting results, Monteiro et al (55) demonstrated that prenatal heat stress alters the calf 's capacity for IgG transfer rather than reducing the quality of the colostrum produced by the dam.…”

“…Prenatal heat stress reduces the overall immune competence of calves during their postnatal life by derailing hematological parameters and cellular immune status from normal. For example, calves born to heat stressed dams, receiving colostrum from their dams, had reduced circulating plasma proteins (51), red blood cell counts, platelets and circulating hemoglobin, lower lymphocyte counts, and increased circulating concentration of acute phase proteins during the pre-weaning period relative to those born to cooled dams receiving colostrum from their dams (56). Peripheral blood mononuclear cells (PBMC) were isolated from in utero heat stressed or cooled calves' blood during the pre-weaning stage and were incubated in vitro with a mitogen.…”

Lying down frequency as a discomfort index in heat stressed Holstein bull calves

“…As these are all parts of complex comfort behaviour, total time spent lying down, the number of lying bouts, and the frequency of lying down are often studied in response to environmental factors in adult cattle 2 , 3 . Although the effect of in utero heat stress exposure on calf activity patterns 4 and on overall well-being 5 , 6 have been recently evaluated during the neonatal period, there is a paucity of information regarding biobehavioral responses to acute heat stress experienced by calves during the pre-weaning period. Commercial automatic data loggers overcome the limitation of time-consuming video-based behavioural observations in calves; 7 however, no research has evaluated lying behaviour in dairy calves during extreme heat stress events.…”