Diet and Genetics Influence Beef Cattle Performance and Meat Quality Characteristics

A comprehensive review of the impact of tropical pasture grazing, nutritional supplementation during feedlot finishing and fat metabolism-related genes on beef cattle performance and meat-eating traits is presented. Grazing beef cattle on low quality tropical forages with less than 5.6% crude protein, 10% soluble starches and 55% digestibility experience liveweight loss. However, backgrounding beef cattle on high quality leguminous forages and feedlot finishing on high-energy diets increase meat flavour, tenderness and juiciness due to improved intramuscular fat deposition and enhanced mono- and polyunsaturated fatty acids. This paper also reviews the roles of stearoyl-CoA desaturase, fatty acid binding protein 4 and fatty acid synthase genes and correlations with meat traits. The review argues that backgrounding of beef cattle on Desmanthus, an environmentally well-adapted and vigorous tropical legume that can persistently survive under harsh tropical and subtropical conditions, has the potential to improve animal performance. It also identifies existing knowledge gaps and research opportunities in nutrition-genetics interactions aimed at a greater understanding of grazing nutrition, feedlot finishing performance, and carcass traits of northern Australian tropical beef cattle to enable red meat industry players to work on marbling, juiciness, tenderness and overall meat-eating characteristics.

Alteration of fasting heat production during fescue toxicosis in Holstein steers

This study was designed to examine alteration of fasting heat production (FHP) during fescue toxicosis. Six ruminally cannulated Holstein steers (BW = 348 ± 13 kg) were BW-matched into pairs and used in a 2 period crossover design experiment. Each period consisted of 2 temperature segments, one each at 22 and 30°C. During each period, 1 steer per pair was ruminally dosed twice daily with 0.5 kg of ground endophyte-infected fescue seed (E+) and the other with ground endophyte-free fescue seed (E-) for 7 d. Steers on E- treatment were pair-fed to E+ steers offered alfalfa cubes at 1.5 × NEm. On d 8 of each segment, steers were moved to individual metabolism stalls fitted with indirect calorimetry head boxes. Ruminal contents were removed, weighed, and subsampled for DM determinations. The reticulorumen was washed and filled with a buffer (NaCl = 96; NaHCO3 = 24; KHCO3 = 30; K2HPO4 = 2; CaCl2 = 1.5; MgCl2 = 1.5 mmol·kg buffer(-1)) that was gassed with a 75% N2 and 25% CO2 mixture before rumen incubation. During buffer incubation, an E+ or E- fescue seed extract was added at 12 h intervals to maintain treatment presentation to the animal. After a 12-h wait, heart rate, O2 consumption, CO2 production, and urinary output were recorded for 16 h. There was no difference (P = 0.931) in DMI/kg(0.75) between endophyte treatments by design; however, intake decreased (P = 0.004) at 30°C. Increased temperature had no effect (P > 0.10) on other measurements and there were no significant interactions (P > 0.11) of temperature and endophyte treatment. Heart rate was unaffected by fescue treatment or environmental temperature. Percent DM of ruminal contents as well as total rumen DM/kg(0.75) was increased (P < 0.0001) in E+ steers. Respiratory quotient was elevated (P = 0.02) in E+ steers. Oxygen consumption decreased (P = 0.04) and CO2 production tended to be reduced (P = 0.07) during E+ treatment. Calculated FHP (kcal/kg BW(0.75)) was also less (P = 0.006) in steers receiving E+ treatment. These data suggest that consumption of endophyte-infected tall fescue by cattle results in a reduction in basal metabolic rate.

Effect of rotation frequency and weaning date on forage measurements and growth performance by cows and calves grazing endophyte-infected tall fescue pastures overseeded with crabgrass and legumes1

A grazing study was initiated in April 2000 and continued through three calving and weaning cycles (ending July 2003) to investigate the effects of rotational grazing management (twice monthly [2M] vs. twice weekly [2W]) and weaning date (mid-April [EARLY] vs. early June [LATE]) on production of fall-calving cow-calf pairs (495 +/- 9.6 kg initial BW) grazing Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.) overseeded with legumes and crabgrass. Secondary objectives of the experiment were to monitor differences in quantity and quality of available forage and to evaluate changes in forage species composition. Pastures were dominated by tall fescue throughout the study, and the proportion of basal cover was greater (P < 0.05) in 2M than in 2W pastures. The percentage of legumes was very low across all treatment combinations, but the percentage of crabgrass continued to increase (P < 0.05) linearly and quadratically across years for both summer and fall sampling periods, regardless of rotation or weaning program. In vitro DM disappearance and mineral concentrations varied minimally because of rotation frequency or weaning date. Rotation frequency did not substantially affect (P = 0.11 to 0.97) cow BW, hay offered, milk production, calving interval, calf birth weight, or actual or adjusted weaning weights; however, 2M cows had 0.3 units higher (P < 0.05) BCS at the time of breeding than 2W cows. Calves weaned late had greater (P < 0.05) actual weaning weight and weighed more (P < 0.05) on the LATE weaning date than on the EARLY weaning date, but 205-d adjusted weaning weights did not differ (P = 0.74) across weaning dates. Therefore, rotation frequency and/or weaning date had little effect on forage species composition or forage quality. In addition, the rapid rotation program offered little advantage with respect to animal performance, and weaning fall-born calves grazing endophyte-infected tall fescue pastures at approximately 189 d of age seemed to be detrimental to calf performance compared with delaying weaning until 243 d of age.