Development of a weight-estimation model to use in pregnant criollo-type mares

EnglishThe aims of this study were: 1) to compare the tape weight and associated weight-estimation formula to evaluate weight gain in pregnant mares, and 2) to develop a mathematical model to estimate the weight of pregnant mares using body measurements. Thirty-four criollo-type mares were evaluated every two weeks during the middle and late pregnancy. The mares were weighed on a livestock scale, and we estimated body weight using tape weights and an associated body-weight estimation formula. Also, heart-girth circumference (heartgirth) and abdominal circumference were measured; the latter at the 12th intercostal space (12th ICS) and 18th rib (18th Rib), to use in a mathematical model to estimate the weight of pregnant mares. Observations were divided into three periods of pregnancy: 5th to 7 h month, 7th to 9 h month, and 9th to 11th month. Mares in late pregnancy showed an increase in actual weight and an increase in 12th ICS and 18th Rib measurements. Tape weight and body-weight estimation formula underestimated the weight of pregnant mares. However, the regression model using heart-girth circumference, 12th ICS, and 18th Rib measurements showed high correlation (r2 = 0.87, P Key words: pregnant mares; weight tape; body weight estimation portuguesEste estudo teve como objetivos: 1) comparar a utilizacao dos metodos alternativos fita de pesagem e peso metabolico em eguas gestantes e; 2) desenvolver um modelo matematico para estimar o peso de eguas gestantes, baseado em medidas corporais. Trinta e quatro eguas foram avaliadas quinzenalmente durante o terco medio e final da gestacao. Foi realizada a pesagem em balanca comercial; a mensuracao com a fita de peso para equinos; o calculo do peso metabolico; as medidas de perimetro toracico (Ptorac); a mensuracao abdominal no decimo segundo espaco intercostal (12EI) e na decima oitava costela (18Cost). As observacoes foram divididas em tres periodos gestacionais: Periodo de 5 a 7 meses, Periodo de 7 a 9 meses e Periodo de 9 a 11 meses. As eguas demonstraram incremento no peso na balanca e na mensuracao abdominal no 12EI e 18Cost no terco final da gestacao. A utilizacao da fita de pesagem e o calculo de peso metabolico subestimaram o peso na balanca em eguas gestantes. O modelo de regressao utilizando o Ptorac, 12EI e 18Cost apresentou alta correcao (r2=0,87; P Palavras-chave: gestacao; fita peso; peso estimado