Effects of sex, genetic potential, and season on botanical composition of cattle diets under semidesert conditions

• Main Author: Mohammad, Ayed Ghaleb
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1992
• Subjects: Animal sciences; Livestock
• ISBN: 9798208103364

A comparison of diet composition between cows and steers, the association of diet composition with the genetic potential of cows, and the similarity between fecal samples, evacuated rumen samples, and non-evacuated rumen samples were investigated. The study was conducted under semi-desert conditions, using cross-breed cows differing in genetic potential and rumen cannulated steers. The cows represent six genetic groups composed of Hereford, Brangus, Charolais and Simental breeding, varied in milk breeding value, growth breeding value, and total maternal breeding value. The steers are crossbred of Red Angus x Hereford x Angus breeds. Vegetation and animal samples were collected during May-June (Spring), July-August (Summer), October (Fall), in 1989, January (Winter), and July-August (Summer), in 1990. Results showed that cattle diets were highest in grass content during spring, summer, and winter, while forbs comprised the highest proportion of cattle diets during the fall. The major grass species contributing to cattle diets were drop seeds (Sporobolus spp.), black grama (Bouteloua eriopoda), and threeawn species (Aristida spp.). Leatherweed croton (Croton pottsii) was the most important forb species. The importance of these species varied with season. Some differences (P $<$ 0.05) were detected by fecal analysis between cow and steer diet compositions at certain periods. The relative similarity between cow and steer diets varied with season, which may be related to physiological variation or past experience between cows and steers. Therefore, caution should be exercised when steer diets are used to represent cow diets or vice versa. An important association between the proportion of some plant species in cow's diet and the genetic potential of cows was detected during certain seasons, which may indicate differences between cows with low production potential and those with high production potential to adapt for the available forage. Fecal samples, evacuated rumen samples, and non-evacuated rumen samples differed (P $<$ 0.05) in some dietary components. The similarities ranged between 74% and 93% depending on season and techniques compared. Differential digestion and sampling procedure could be possible causes for these variations.