Source: Michigan State University Extension, Jerad Jaborek
Newly received feedlot calves undergo numerous stressors that can be brought about by weaning, transportation, and commingling. These stressors can affect digestive and immune function for these calves. This article will focus on the nutritional implications these stressors can have on feed intake of newly received feedlot calves, specifically their protein requirements.
Feed and water deprivation, from abrupt weaning and learning to eat new feedstuffs or due to the time spent during transport, can affect the willingness of newly received feedlot calves to consume feed upon arrival. Feed intake during the first week of arrival in the feedlot can be considerably less than the second week for calves. Therefore, the receiving diet should have a greater nutrient density to compensate for the decreased feed intakes of newly received feedlot calves. The lesser feed intake observed during the first week of feedlot arrival has not been shown to be due to reduced rumen bacteria or digestibility of the consumed feed. Rather, it may be driven by a change in endocrine signaling and blood metabolite concentrations that changed due to the feed and water deprivation.
Researchers from The Ohio State University, Fluharty and Loerch, investigated the effects of different crude protein (CP) percentages and protein sources included in the receiving diet fed for the initial weeks after arrival. In experiment one, average daily gain (ADG) and feed efficiency (G:F) improved linearly with increasing CP concentrations from 12, 14, 16, and up to 18% during the first week after feedlot entry. Dry matter feed intake (DMI) was not different across the different CP concentrations. However, DMI was about 45% less during week one relative to week two, so CP intake ranged from 322 to 580 g/d (0.71 to 1.28 lb./d) during the first week after feedlot entry. Over the course of the six week receiving period, feeding spray-dried blood meal resulted in a greater G:F compared with soybean meal as the protein source in the diet. Rumen undegradable protein sources may be more beneficial when the supply of amino acids is low and DMI is less than 2% of their body weight. This experiment demonstrated that newly received calves weighing 525 pounds benefited from greater concentrations (16 and 18%) of CP during the first week after entering the feedlot.
In experiment two, investigated greater CP concentrations with soybean meal and blood meal each supplying 50% of the CP at 11, 14, 17, 20, 23, or 26% of the diet dry matter. The DMI of calves did not differ across the different CP concentrations, but DMI was 48% less during week one relative to week two. Crude protein intake increased from 265 to 738 g/d (0.58 to 1.63 lb./d), with only the 23 and 26% CP concentrations meeting the protein requirements of 525 lb. calves trying to achieve a 3 lb./d ADG. Not surprisingly, ADG increased linearly with the 23 and 26% CP treatments having the greatest ADG during week one. Interestingly, G:F demonstrated a quadratic response where 17 and 20% CP treatments were greatest during week one and for ADG and G:F across the entire four week receiving period on average. Therefore, the results indicate that about 20% CP resulted in the best feedlot performance during the receiving period.
Experiment three investigated changing dietary CP concentrations after week one and week two when feed intake appeared to be the lowest. Crude protein concentrations were 23% for week one, 17% for week two, and 12.5% for week three. In addition, different feedstuffs were investigated to supply dietary protein, with either soybean meal, blood meal, corn gluten meal, or fish meal used. Feed intake was 40 to 48% less during week one compared with week two. The different protein sources did not result in any significant differences in feedlot performance during the four week receiving period. As long as metabolizable protein requirements are being met, a wide variety of protein sources may be used to meet dietary protein needs of newly received feedlot calves.
It is not uncommon for newly received feedlot calves to have feed intakes 0.5 to 1.5 % of their body weight during the first week. However, providing these stressed calves adequate energy and protein to meet their nutrient needs will improve their ability to increase their feed intake and combat potential illnesses. Providing calves a preconditioning period before feedlot entry can greatly reduce weaning stress, expose and acclimate calves to the feedstuffs used in feedlots, and accumulate energy reserves prior to transport, which will allow for an easier transition into the feedlot for newly received calves.