Effects of Alfalfa Hay Particle Size and Daily Feeding Frequency on Lamb Performance and Digestibility Traits

Abstract

Seventy-two Najdi three month old male lambs weighing an average of 24 kg body weight were used in this experiment. Animal groups were randomly allotted to one of six dietary-treatment groups in a 3x2 factorial arrangement of three diets (9.5 and 14 mm) particle length pelleted diets and long hay diet, and two feeding frequencies (once or twice daily) , 12 animals per group. The compelete pelleted diets (9.5 and 14 mm) contained 75% concentrate plus 25% chopped alfalfa hay while the long hay diet (fed as mash form) contained 75% concentrate plus 25% unchopped alfalfa hay.The effect of alfalfa particle length and feeding frequency on lamb performances, digestibility traits and carcass characteristics over a period of 100 days were recorded. The results of statistical data analysis showed that there were no effects (P>0.05) of the particles length and long alfalfa hay diet on daily dry matter intake (DMI).Lambs fed the 9.5 mm diet had higher (P<0.05) average daily gain (ADG) and gain efficiency than those fed 14 mm or long hay diets. Although ADG, DMI and feed to gain ratio were not affected (P>0.05) by frequency of feeding,they were numerically lower in lambs fed twice daily as compared with those fed once daily. Digestion coefficients of DM, CP and NFE were not affected by particle length of alfalfa hay in experimental diets. Apparent digestibility percentage of EE, ADF and NDF higher (P<0.05) for long-hay diet versus 9.5 mm diet, whereas no significant differences were noted between 9.5 and 14 mm diets. Although N intake and fecal N excretion did not differ (P>0.05) among the three treatment groups, N retention was higher (P<0.05) in lambs fed 9.5 mm. Apparent total tract digestibilities of DM, CP, EE and ADF were not affected (P>0.05) by feeding the lambs once or twice daily. Neither Fecal, urinary N excretion nor N retention were affected by feeding frequency .There was a significant difference (P<0.05) for apparent total tract digestibility of NDF, as NDF digestibility decreased in lambs fed twice daily in comparison with those fed once daily. ii Reduction of particle length of alfalfa hay to 9.5 or 14 mm increased (P<0.05) total VFA concentration at all post-feeding times as opposed to long hay diet; the differences between 9.5 and 14 mm diets in total VFA concentrations were not significant (P>0.05). Mean molar proportion acetate increased (P<0.05), while mean molar proportion propionate and butyrate decreased (P<0.05), as lambs fed on long hay diet.The differences between 9.5 and 14 mm diets in mean molar proportions of acetate, propionate and butyrate were not significant (P>0.05). The ratio of acetate to propionate tended to increase (P<0.05) when lambs were fed long hay diet. Rumen total VFA concentrations at all post-feeding times were not influenced (P>0.05) by feeding frequency, except at 10 h post-feeding; Rumen VFA concentration value was higher (P<0.05) in lambs fed once daily than those fed twice daily. Acetate molar proportion was less (P<0.05) in lambs fed once daily compared with lambs fed twice daily.Lambs fed on the long hay diet had a flat HN 3-N concentration pattern than those on 9.5 and 14 mm pelleted diets.The pattern in ruminal HN3-N concentration differed between 9.5 and 14 mm diets. Ruminal HN 3-N concentration increased (P<0.05) in group of lambs fed twice a day compared with those fed once a day. There was significant (P<0.05) effect of the particle length on ruminal retention time.Lambs fed on 9.5 and 14 mm pelleted diets had shorter ruminal retention time than those fed on long hay diet. Mean retention time was not affected (P>0.05) by feeding frequency. The hot carcass weight and percentage of separable lean increased significantly (P<0.05) as the particle length of alfalfa hay decreased.Particle length did not affect (P>0.05) dressing percentage and separable fat percent. The hot carcass weight, dressing percentage and separable lean, fat percentage were not affected significantly (P>0.05) by feeding frequency. The in vitro dry mater digestibility of three diets (9.5mm, 14 mm and long alfalfa hay)was significantly affected (P <0.05) by particle sizes. DM digestibility of 9.5mm diets were higher (P <0.05) than 14 mm and long alfalfa hay diets. However no significant differences were noted between 14 mm and long alfalfa hay diets. Invitro measurement there was no significant difference between the feeding frequencies once or twice a day in dry matter digestibility %.