A spline polynomial model to describe serum IGF-I concentration from birth to slaughter in calves: effects of weaning age, pre-weaning concentrate feeding and breed

• Published in: Domestic animal endocrinology Vol. 38; no. 3; pp. 157 - 167
• Main Authors: Blanco, M., Casasús, I., Villalba, D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2010; [Amsterdam; New York]: Elsevier Science Pub. Co
• Subjects: Age Factors; analysis; animal age; Animal Nutritional Physiological Phenomena; Animals; Beef calves; beef cattle; blood serum; Breed; breed differences; Breeding; calf feeding; calves; Cattle; cattle breeds; chemical concentration; Diet; early weaning; Eating; Eating - physiology; feed concentrates; feed intake; IGF-1; insulin-like growth factor I; Insulin-Like Growth Factor I - analysis; liveweight gain; Male; mathematical models; Models, Statistical; Parda de Montaña; physiology; Pirenaica; Pre-weaning concentrate feeding; spline curve; Weaning; Weaning age; Weight Gain; Weight Gain - physiology; Pre-weaning concentrate feeding; IGF-1; Beef calves; Breed; Weaning age
• ISSN: 0739-7240; 1879-0054; 1879-0054
• DOI: 10.1016/j.domaniend.2009.09.003

The statistical analysis of hormones sampled throughout the production cycle is complicated because factors such as age and weight at the measuring date interfere. Spline curves constructed from pieces of low-degree, random-effects polynomials could be used for a more accurate analysis of data. Concentration of insulin-like growth factor-1 (IGF-1), weight gain, and concentrate intake of Parda de Montaña (PM) (n = 27) and Pirenaica calves (n = 14) were modeled with a spline model according to age at weaning, pre-weaning concentrate feeding, and breed. At birth, calves were randomly assigned to early weaning (EW) at 90 d or traditional weaning (TW) at 150 d. During lactation, half of PM calves received concentrates (S), whereas the remainder received no concentrates (NS). After weaning, calves received concentrates on an ad libitum basis until they reached a weight of 450 kg. The spline model had better likelihood than a polynomial of 6 degrees or a split-plot model. Serum IGF-1 concentration was greatly affected by age at weaning and pre-weaning concentrate feeding, but not by breed. In NS calves, IGF-1 concentration was greater in EW than in TW calves from 120 to 300 d, irrespective of breed. During lactation, S calves had greater IGF-1 concentration than NS calves. After weaning, EWNS calves reached the IGF-1 concentration of EWS calves after 4 mo on concentrates, whereas TWNS calves attained IGF-1 concentration of TWS calves after only 2 mo, because of their increased concentrate intake relative to TWS calves. Concentration of IGF-1 was positively correlated with the immediate weight gains and intake, but it was not a good predictor of performance in the long term.