Parity in cow-calf pair: stress response at weaning and growth characteristics of Nellore heifers on pre-and post-weaning

• Ano de defesa: 2023
• Autor(a) principal: Paula, Camila de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa; Zootecnia
• Palavras-chave em Português: Bovinos de leite; Bezerros; Desmame - Efeito fisiológico; Produção Animal
• Link de acesso: https://locus.ufv.br//handle/123456789/31313; https://doi.org/10.47328/ufvbbt.2023.394

The cow's milk yield has been described as a factor that influences the performance of calves in the pre-and post-weaning phases. Furthermore, weaning is known to generate multiple stressors in the calf-cow pair. Nonetheless, little is known whether these responses differ according to parity order. The goal of these three studies was to evaluate whether calving order influences the weaning stress response in the cow-calf pair and the effects of dam's parity in pre- and post-weaning beef heifers: performance, growth, metabolism, hormonal and reproductive characteristics. Thirty pregnant Nellore cows with their respective female Nellore calves were randomly allocated to five paddocks and two cow-calf pairs from each parity group were placed in the paddocks. The main results of the first study, there was an interaction (P < 0.05) between parity and evaluation days regarding cortisol, where on d +7, the higher concentration was observed for multiparous cows. There was an interaction (P < 0.05) between parity and evaluation day for red blood cells (RBC), hematocrit (HCT), and hemoglobin (HB), whereby higher RBC counts on d +4 were observed for multiparous cows. For HCT and HB, on all post-weaning collection days, higher values were observed for multiparous cows. The concentrations of ceruloplasmin, haptoglobin, total proteins, albumin, and the number of white blood cells, neutrophils and lymphocytes varied over the days of collection (P < 0.05). The day of evaluation had an (P < 0.05) effect on all recorded behaviors, except for rumination (P > 0.05). In the second study, the initial body weight (BW), final BW, and average daily gain (ADG) of heifers were similar between parities (P > 0.05), in the pre-weaning phase. In response to weaning stress, BW was not affected by the interaction (P > 0.05), however, it was affected by day (P < 0.05). Only the cortisol concentration of the heifers was influenced by the dam’s parity (P < 0.05), with a higher concentration for heifers born to multiparous than primiparous cows. For most of the physiological measurements, there was variation over the days of collection (P < 0.05), except for haptoglobin concentration (P > 0.05) and neutrophils: lymphocytes ratio (P > 0.05). In the third study, the main results found in the post-weaning were that initial and final BW and ADG of heifers were similar between treatments (P > 0.05). Body measurements were similar between heifers (P > 0.05), except that rump length was greater for heifers from multiparous than primiparous cows (P < 0.05). In the dry season (d 84), the subcutaneous fat thickness of the loin and subcutaneous fat thickness on the rump were higher for heifers from multiparous cows when compared to heifers from secundiparous cows (P < 0.05). At the end of the experiment, all body composition measurements were similar between parities (P > 0.05). In all measurements studied, the metabolic profile of heifers was similar between parities (P > 0.05). Except, on d 84, triglycerides and very-low density lipoprotein were higher for heifers from primiparous than heifers from secundiparous and multiparous cows (P < 0.05). Also, progesterone, leptin, and Insulin-like growth factor 1 concentrations were similar among heifers (P > 0.05). In addition, the dam's parity did not influence reproductive performance (P > 0.05). Nellore cows, regardless of parity, undergo behavioral and physiological changes in abrupt weaning. Parity influences physiological parameters indicating that the magnitude of stress is greater in multiparous cows. In Nellore heifers, there are physiological changes caused by abrupt weaning, but they are slight influenced by the parity of the dams. In addition, in the post-weaning period, maternal parity is a factor that has slight influence on the performance, metabolic, hormonal, and reproductive characteristics of Nellore heifers on pasture. Keywords: Bos indicus. Maternal effects. Physiological changes. Behavior. Growth rate. Puberty.