Abstract
Reproduction is associated to the profitability of beef herds, which affects the level of productivity and is influenced by nutritional level. The objective of this study was to evaluate the effect of protein and energy supplementation, before and after parturition, on reproductive variables of Nellore primiparous cows extensively raised in the Brazilian tropical savannah. Eighty pregnant heifers with parturition estimated for a 45 d period during the dry season were randomly divided into four treatments: Control, received a mineral salt and urea mixture pre and postpartum; PRE, protein-energy mixture from the 210th gestational day until parturition; POS, protein-energy mixture from parturition until 90 d afterwards; PREPOS, protein/energy mixture from the 210th gestational day until the 90th day after parturition. Number of days to complete uterine involution (UI) was 37.0 (Control); 31.3 (PRE); 33.1 (POST) and 25.3 (PREPOST) with differences (P<0.05). Calving Interval (CI) was 370.4 (Control), 369.5 (PRE); 365.9 (POST) and 343.7 (PREPOST) days, with differences (P<0.05). Pregnancy rate (PR) was 64.7%; 76.5%; 65.0%; and 55.0%, respectively, for CONTROL PRE, POS, PREPOS, without difference (p>0.05). In conclusion, energy-protein supplementation of Nellore primiparous cows raised in extensive systems under tropical conditions, before and after parturition, reduces days to uterine involution and calving interval.
Highlights
In Brazil, 80% of commercial herds is compose by Nellore cattle (ACNB, 2019), handled under extensive conditions, with a breeding season during summer or the rainy season, from October until April, with the concentration of the reproductive programs from December until March, and calving season during the dry season, when pastures can poorly provide animal needs
The economic return of nutritional investment for Nellore cattle reared in pasture could be similar between protein-energy and energy supplementation
2.1 Local, animals and treatments The study was performed in a commercial Nellore herd in the Middlewest region of Brazil (Goiás State), Brazilian tropical savannah, Cerrado biome, characterized by the tropical climate Aw (Köppen-Geiger), 17o 47'45" S and 51o 02'07" W, 787 a.s.l. and annual rainfall of 1,587 mm, with well-defined rainy and dry seasons and seasonal forage offer
Summary
In Brazil, 80% of commercial herds is compose by Nellore cattle (ACNB, 2019), handled under extensive conditions, with a breeding season during summer or the rainy season, from October until April, with the concentration of the reproductive programs from December until March, and calving season during the dry season, when pastures can poorly provide animal needs. Nellore is a Zebu cattle from India well adapted to adverse environment, high fertility, and good maternal instinct. One of the Brazilian regions with the highest cattle pasture-based production (about 48.5 million Ha) is located in the tropical savannah, known as Cerrado biome or seasonal forest (Batalha, 2011). Reproduction is associated to the profitability, which affects productivity and depends on nutritional, genetic, sanitary and efficient management factors. The prolonged postpartum anoestrus is the most important cause of low reproductive efficiency and can be affected by the inadequate nutrition during the pre and postpartum period. The economic return of nutritional investment for Nellore cattle reared in pasture could be similar between protein-energy and energy supplementation
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