Evaluation of feeding behavior of ad libitum-fed lactating dairy cows by time-lapse photography revealed 68% of the total feeding activity occurred between the daylight hours of 0600 and 1800. Cows consumed an average of 12.1 meals/day, each 20.9 min in duration. Only 58% of the total defined meal time actually was spent eating, or 253.6 min/cow per day. Estimated meal size and rate of eating, as well as total daily time spent eating, were greater for cows as compared to animals with lower energy demand. Certain feeding characteristics, such as meal frequency and duration, were variable among animals, suggesting that these behaviors may be characteristics of individual cows. Results by time-lapse photography compared well with direct measurement by weigh-cell apparatus.

Plasma glucose, immunoreactive insulin (IRI), and growth hormone (GH) were determined in fasted lean and genetically obese pigs at 1, 3, and 6 mo of age. Rate of glucose clearance and plasma IRI and GH response in provocative stimulation were also measured. Fasting glucose was similar in lean and obese pigs, whereas glucose clearance rate was more rapid in lean pigs. Obese pigs were not hyperinsulinemic but had lower plasma GH than lean pigs. At 1 mo of age, both lean and obese pigs had higher plasma IRI and GH as compared to 3 and 6 mo. Glucose infusion produced increases in plasma IRI at 1, 3, and 6 mo, respectively, with the greatest increases at 6 mo. Plasma IRI peaked at the same level in both pig types at a given age; but due to a more prolonged response in obese pigs, the overall IRI response to glucose infusion was greater in obese pigs. Arginine infusion caused much smaller IRI responses than glucose, but the response of obese pigs was significantly greater than that of lean pigs. Both provocative stimuli caused increases in plasma GH. The GH response to glucose infusion in obese pigs was considerably less than in lean pigs. These observations suggest mild insulin insensitivity and a reduced GH secretory potential in the obese as compared to lean pigs.

Sodium bicarbonate was added to complete mixed rations to evaluate the effect of buffer addition on adaptation to high-energy rations by dairy cows in elderly lactation. Forty-five Holstein cows were assigned to one of three treatment groups: control pre- and postpartum; control prepartum, buffer postpartum; and buffer pre- and postpartum. Rations consisted of 85% chopped grass hay: 15% concentrate prepartum and 60% corn silage:40% concentrate postpartum. On day 4 postpartum, cows were switched abruptly to the postpartum ration for 9 wk. Buffered rations contained .6% sodium bicarbonate prepartum and .7% postpartum. Daily dry matter intake as a percent of body weight for cows fed buffer postpartum (3.51%) was greater than for cows fed no buffer (3.04%) of buffer pre- and postpartum (3.14%). Average production of 4% fat-corrected milk was greater for cows fed buffer postpartum and buffer pre- and postpartum (31.9 kg/day and 31.7 kg/day) than for cows fed no buffer (28.9 kg/day). Milk fat tests were not different. Cows fed the buffered rations lost body weight between wk 1 and 9 as compared to a net gain for cows fed no buffer. Cows fed buffers consumed more dry matter during wk 1 than did cows fed no buffer. Samples of rumen fluid, feces, and serum showed few differences that could be attributed to treatments. Compared to controls, cows fed sodium bicarbonate adapted to rations more rapidly postpartum as indicated by increased feed intake during the first 2 wk and by increased milk production during the first 4 wk of the trial.

Newborn Yorkshire and Ossabaw (feral) pigs were examined under thermoneutral conditions to determine whether survival rate during fasting differs between these breeds and whether any blood-borne factors are associated with improved survival. Newborn pigs were removed from the sow before suckling. Body composition was determined on 10 newborn Ossabaw and 12 newborn Yorkshire pigs. Another group of animals (eight Ossabaw, 12 Yorkshire) was fasted for 72 hr, with blood samples drawn at birth and 12 and 24 hr into fasting. Glucose, free fatty acid (FFA), growth hormone (GH), insulin, thyroxine (T4), triiodothyronine (T3), cortisol and glucagon concentrations were measured in plasma of fasted pigs. Concentrations of carcass lipid, dry matter and ash were higher in newborn Ossabaw pigs than in newborn Yorkshire pigs. Survival through 72 hr of fasting was lower among Yorkshire pigs. Yorkshire and Ossabaw pigs had similar concentrations of metabolites and hormones at birth, with the exceptions of lower plasma GH and higher T3 concentrations in Ossabaw pigs. Higher plasma T3 concentrations would indicate a greater potential for fatty acid oxidation. During fasting, Ossabaw pigs had lower plasma GH and T4 concentrations and higher glucagon and FFA concentrations. Increased survival among newborn Ossabaw pigs may have been due to increased availability of FFA during fasting, and to a greater potential for gluconeogenesis through increased oxidation of fatty acids and higher plasma glucagon concentrations. This would suggest that maternal treatments that would increase storage of fat and(or) increase the capacity for oxidation of fat in utero would improve survival of newborn pigs.

Feeding behavior of five Holstein steers fed a complete mixed ration was studied by use of individual, electronically controlled feeding behavior units. Both individual meal and daily behavioral parameters were measured. Number of meals, size of each individual meal, time spent eating, and intervals between meals were measured. Eating rates were then calculated. Diurnal feeding patterns were observed with 60.9% of the meals occurring between 0600 and 1800 h. For individual meals, body weight accounted for less than 30% of the variation in meal size. Average meal size was 414.5 g. Respective means for overall meal duration, actual meal duration, overall eating rate, and actual eating rate were 20.3 min, 13.7 min, 23.1 g/min, and 30.0 g/min. Meal size per body weight (g/kg or g/kg.75) was relatively constant during observation. Both increased eating rate and increased meal length were associated with larger meals. However, eating rate tended to plateau while meal length continued to increase with larger meals. Steers consumed 10.01 meals per day while total daily overall meal duration and actual meal duration were 220.9 and 156.4 min.

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Plasma concentrations of GH, insulin, glucose, and FFA were measured in high yielding dairy cows at periods of peak milk production and later during periods of increased feed intake. During each period, five cows were prepared with indwelling jugular catheters, and blood was sampled at 10-min intervals for 24 h, followed by hourly sampling for an additional 24 h. During early lactation (30 days post partum), the plasma GH concentration was elevated (13.2 ng/ml) compared to that in later lactation (90 days post partum; 9.8 ng/ml). This increased GH status was due to a greater magnitude of individual secretory spikes (27.3 vs. 20.2 ng/ml) rather than a difference in the frequency of spikes or in baseline plasma levels of GH. As lactation progressed from 30-90 days post partum, milk yield decreased, feed intake increased, and overall plasma concentration of insulin increased (17.3 vs. 29.3 microU/ml), reflecting both an elevated magnitude of hormone secretory spikes (30.2 vs. 55.2 microU/ml) and an elevated baseline concentration (16.8 vs. 27.3 microU/ml). The short term repeatability of overall mean and total 24-h GH and insulin secretion in lactating cows was demonstrated as well as the uniqueness of individual cow GH secretory patterns. Significant differences were not found in either glucose or FFA concentrations between lactation periods. Increased GH and decreased insulin during early lactation are likely to promote the mobilization of adipose tissue stores needed to supplement dietary energy consumption.

The shortage of available forage during mid−summer is considered a major factor limiting the size of beef cowcalf herds in the Northeast. Consequently, using warmseason perennial range grasses as a supplement to existing cool−season grass forage programs is being considered. Animal feeding trials were conducted to assess the forage quality of ‘NY 1145’ big bluestem (Andropogon gerardi Vitman), and ‘Blackwell’ switchgrass (Panicum virgatum L.) grown in Pennsylvania. Laboratory and animal estimates of digestibility were compared. Warm−season grass hays harvested at early head emergence, 2 weeks later, and at a regrowth stage in fall were fed with protein supplement to growing wether sheep in the first trial. In vivo digestible dry matter (DDM) of the hays ranged from 67 to 74%. Big bluestem and switchgrass DDM decreased 0.50 and 0.36 percentage units/ day, respectively, when harvest was delayed 2 weeks after head emergence, but dry matter intake (DMI) was not affected. Warm−season grass DDM and DMI were equal or superior to those for summer or fall harvested ‘Ky 31’ tall fescue (Festuca arundinacea Schreb.). In the second trial, DDM of big bluestem and switchgrass hays harvested at early head emergence and fed to mature wether sheep without protein supplement ranged from 56 to 69%. Digestible dry matter and DMI for the warm−season grasses were generally lower than those for tall fescue harvested in spring at the same growth stage. In both animal studies, rankings of the grass hays using in vitro dry matter digestibility (IVDMD) and DDM estimates did not differ. The IVDMD technique did underestimate DDM by approximately 17 percentage units. This emphasizes the importance of animal evaluation in supporting laboratory forage quality analyses. Results suggest that big bluestem and switchgrass forage, harvested at early head emergence or later, appear most suitable for animals with lower nutrient requirements, such as beef cows.