Feed Requirements For Maintenance Research Articles

Estimated genetic parameters for mature cow live weights during lactation in a multi-breed dairy cattle population

ABSTRACT Live weight (LWT) is an important trait for dairy production systems as it influences both maintenance feed requirements and beef revenue from culled cows and from offspring surplus to replacements. The breeding goal for the New Zealand dairy industry includes LWT. This study estimated genetic parameters for LWT during lactation from some animals in the New Zealand multi-breed dairy cattle population. A total of 31,922 LWT records from 11,222 lactating dairy cattle born from 1988 to 2015 were used for the analysis. Estimation of (co)variance components used Gibbs sampling from pedigree-based models. The posterior mean heritability estimates using scale weights were consistently high across six lactations and ranged from 0.57 to 0.64. There were high genetic correlations between the scale weights measured during different lactations (>0.95). We further estimated the posterior mean heritability for subjective liveweight scores recorded from first lactation using trained inspectors and the estimate was 0.36, lower than those heritability estimates from scaled weight. Further, the genetic correlations between subjective liveweight score and scale weights at various lactations ranged from 0.91-0.92. It is recommended that only scale weights be used for national genetic evaluation.

The Influence of Residual Feed Intake and Cow Age on Beef Cattle Performance, Supplement Intake, Resource Use, and Grazing Behavior on Winter Mixed-Grass Rangelands.

Simple SummaryFeed efficiency is becoming an important selection tool in the beef cattle industry. Traditionally, feed efficiency of beef cattle has been expressed as the ratio of feed intake to body weight gained; however, selection for high growth rates inevitably increases the maintenance requirements, feed requirements, and intake of cattle, with subsequent higher feed costs. In contrast, net feed efficiency, or residual feed intake (RFI), is defined as the difference between an animal’s actual feed intake and its expected feed requirements for maintenance and growth, with low-RFI animals being more efficient at converting forage intake into kilograms of production than high-RFI animals. This study evaluated the impacts of cow age and RFI on body weight (BW) and body condition score (BCS) change, supplement intake, grazing behavior, and resource use of grazing beef cattle grazing mixed-grass rangelands. Heifer post-weaning RFI had little effect on subsequent performance (BW or BCS), grazing behavior, supplement intake behavior, or resource use. However, cow age significantly influenced subsequent performance, grazing behavior, supplement intake behavior, and resource use. In summary, post-weaning RFI had minimal effects on beef cattle performance, grazing behavior, or resource utilization; however, cow age impacted both grazing behavior and resource use.The objectives of this study were to evaluate the influence of RFI and cow age on the supplement intake and grazing behavior of beef cattle. Average daily supplement intake (kg/cow/d) displayed an RFI × cow age interaction (p < 0.01), with a linear increase in average daily supplement intake with increasing RFI of 3-year-old cows (p < 0.01). Average daily supplement intake (g ∙ kg BW−1 ∙ d−1) displayed an RFI × cow age interaction (p < 0.01), with a quadratic effect on supplement intake of 3-year-old cows (p = 0.01). Cow age displayed a quadratic effect on variation of supplement intake (p < 0.01), where 1-year-old cows had a greater CV of supplement intake than all other cow ages (p < 0.01). Distance traveled displayed a cow age × RFI interaction (p = 0.02), where high-RFI 5-year-old cows traveled further per day than low 5-year-old RFI cows. The probability of grazing site selection was influenced by cow age (p ≤ 0.03). In summary, heifer post-weaning RFI had minimal effects on beef cattle performance, grazing behavior, or resource utilization; however, cow age impacted both grazing behavior and resource use.

Knowledge of improved dairy husbandry practices of farmers of Kauroli, district of eastern Rajasthan

This study was carried out in the randomly selected 20 villages of Hindaun and Todabhim blocks of Karauli District of eastern Rajasthan. The results of the present study revealed that the majority of the farmers (73 %) had partial level of knowledge about overall dairy practices, while 16 per cent farmers had full level of knowledge about overall dairy practices and 11 per cent, who had no level of knowledge about overall dairy practices. The majority of the respondents had partial knowledge about feeding elements, feeding of concentrates and roughage mixture, time of feeding concentrate , feed requirements for maintenance of animals, feed requirements for production purpose, green fodder requirements, extra essential minerals requirement to animals with concentrate and roughage and quantity of minerals required per day per animal, animal breeding programme, improved breeds of bull, artificial insemination, time of next insemination after parturition of animals, pregnancy diagnosis and sources of artificial insemination carried out by artificial insemination centre, vaccination programme to control the diseases vaccination schedule, control of foot and mouth diseases control of hemorrhagic septicemia diseases, control of black quarter diseases and control of anthrax diseases. It was also found that majority of the respondents had partial knowledge about keeping the records of animals, method of determining the age of animals and proper method of milking. It can be concluded that majority of the respondent had partial knowledge about feed practices, breeding practices, disease control practices and general management practices.

384 Metabolizable energy content of feeds: Errors that need attention

Abstract Feedlot performance is predicted reliably from DMI and diet NE. Tabular NE values in turn commonly are calculated from TDN either measured in digestion trials or predicted from nutrient compositions. When estimated from nutrient composition (NRBC, 2016), TDN values for feeds were related imprecisely (R2 = 0.83) to in vivo TDN values (NRC, 2000); deviations ranged from -29% to 162%. Traditionally, DE has been calculated as TDN percentage times 0.044, an assumed calorie content of carbohydrate (4.4 kcal/g). Surprisingly, this value is 5% greater than the heats of combustion of DM from isolated starch, cellulose, and glycogen (4.1788, 4.1810, and 4.1868 kcal/g; Blaxter, 1962; The Energy Metabolism of Ruminants). Being “carbohydrate-equivalent energy,” TDN includes the extra calories from lipid whereas urinary energy (UE) lost during catabolism of digested protein automatically is deducted. When determined calorimetrically, ME equals DE minus both gas energy (GasE) loss and UE. But when DE is being calculated from TDN, UE from digested CP already has been subtracted. Double deduction for UE underestimates ME content of high protein feeds. When DE is calculated from TDN, ME equals DE minus only GasE. Using data assembled by Galyean et al. (2016), multiple regression revealed that GasE was predicted more accurately from dietary NDF and lipid concentrations (GasE, % of DE = 4.87 + 0.131 x NDF - 0.331 x EE; R2 = 0.69) than from diet DE (R2 = 0.27). From this formula, GasE loss as a fraction of DE of feeds ranges from 5 to 15% except for isolated fats than have a negative value; non-additivity across feeds complicates formulation of least cost diets. Correcting discrepancies in calculating ME from TDN should improve reliability of predicting the cost of ME from various feeds and for quantifying feed requirements for maintenance and gain of cattle fed diverse diets.

Prediction of effects of beef selection indexes on greenhouse gas emissions

Genetic improvement in production efficiency traits can also drive reduction in greenhouse gas emissions. This study used international ‘best-practice’ methodology to quantify the improvements in system-wide CO2 equivalent emissions per unit of genetic progress in the Irish Maternal Replacement (MR) and Terminal (T) beef cattle indexes. Effects of each index trait on system gross emissions (GE) and system emissions intensity (EI) were modelled by estimating effects of trait changes on per-animal feed consumption and associated methane production, per-animal meat production and numbers of animals in the system. Trait responses to index selection were predicted from linear regression of individual bull estimated breeding values for each index trait on their MR or T index value, and the resulting regression coefficients were used to calculate trait-wise responses in GE and EI from index selection. Summed over all trait responses, the MR index was predicted to reduce system GE by 0.810 kg CO2e/breeding cow per year per € index and system EI by 0.009 kg CO2e/kg meat per breeding cow per year per € index. These reductions were mainly driven by improvements in cow survival, reduced mature cow maintenance feed requirements, shorter calving interval and reduced offspring mortality. The T index was predicted to reduce system EI by 0.021 kg CO2e/kg meat per breeding cow per year per € index, driven by increased meat production from improvements in carcass weight, conformation and fat. Implications for incorporating an EI reduction index to the current production indexes and long-term projections for national breeding programs are discussed.

Selection for residual feed intake affects appetite and body composition rather than energetic efficiency

Residual feed intake (RFI) is the difference between an animal’s actual feed intake and that which would be expected based on production. This experiment was to test the hypothesis that part of the variation in RFI may be due to differences in energetic efficiency through changes in heat production, these being in part due to differences in protein metabolism. Following three generations of divergent selection for RFI, eight High and eight Low-RFI heifers were fed at both 105% and 180% of predicted maintenance feed requirements. Between-RFI line and feeding-level differences were assessed for energy intake, protein metabolism, heat production, body composition, energy and nitrogen balance and digestibility. The RFI lines did not differ in protein metabolism or heat production. The High-RFI heifers deposited 51% and 56% more subcutaneous fat at the P8 rump and 12/13th rib sites, respectively, with no difference in eye muscle area gain or average daily weight gain. The greater fat deposition of High-RFI heifers was due to a larger ad libitum feed consumption compared with the Low-RFI heifers. Energy and nitrogen balance did not differ between the RFI lines. The energy transactions indicated no difference in the efficiency of energy use on 105% maintenance, although when fed 180% of maintenance the differences in feed intake suggest variation in appetite as the mechanism contributing to RFI. All of the extra energy consumed by High-RFI heifers above maintenance and deposition of protein was associated with additional energy retained as fat. This study suggests that selection for RFI may not lead to improved efficiency of energy use.

Breed effects and heterosis for productivity traits at first calving of Angus, Holstein Friesian, Jersey and crossbred beef cows

Feed requirements for maintenance contribute a large proportion of the feed requirements of a beef cow so lighter cows may be more efficient producers of weaned calves, provided that such cows do not result in a comparative reduction in calf weaning weight. Beef-cross-dairy cows have increased milk yield compared with straight-bred beef cows and have the potential to wean heavier calves. Crossbred cows may also offer potential increases in production through heterosis. This experiment examined the performance of straight-bred Angus (AA), Holstein Friesian (FF) and Jersey (JJ) cows and of Angus-sired F1 crossbreds with Holstein Friesian (AF), Jersey (AJ) and Holstein Friesian-cross-Jersey (Kiwicross; AK) cows to identify breed and heterosis effects on milk intake and liveweight of calves and liveweight, reproductive performance and fatness of cows in their first lactation. Days to calving and weaning rate from first joining were similar among genotypes, but only 50% of FF cows conceived to second joining, compared with 90–98% for the other genotypes (P &lt; 0.05). Estimated milk intake of calves was least (P &lt; 0.05) for calves born to AA cows, and was generally similar (P &gt; 0.05) among calves born to crossbred cows. There were positive heterosis effects between Angus and Jersey and between Angus and Holstein Friesian on milk intake of the calf. Straight-bred FF cows weaned the heaviest calves (least-squares mean + s.e.: 241 ± 5 kg; P &lt; 0.05). Calves born to AF and AK cows were weaned at similar liveweight (229 ± 3 kg and 226 ± 4 kg, respectively; P &gt; 0.05), and were heavier (P &lt; 0.05) than calves born to JJ and AJ cows, which were similar (208 ± 5 kg and 215 ± 3 kg, respectively; P &gt; 0.05). Calves born to AA cows were lightest at weaning (196 ± 3 kg; P &lt; 0.05). Estimates of heterosis for weaning weight were 11 ± 4 kg (P &lt; 0.01) between Angus and Holstein Friesian, and 14 ± 4 kg (P &lt; 0.001) between Angus and Jersey. Angus-cross-dairy cows offered production advantages over straight-bred AA cows as dam lines in a terminal cross. These advantages were partially due to heterosis.

Comparison between native and ‘synthetic’ sheep breeds for milk production in Sardinia

Genetic improvement of milk production can be achieved through crossbreeding and upgrading of local breeds with imported male lines. To this purpose, at IZCS in the early seventies East Friesian rams were mated with native Sarda (Sa) ewes. Descendants of those crosses, having on average about 50% of East Friesian genes, were classified as belonging to a ‘syntethic’ breed (FS). From 1978 to 1992 more than 5000 FS and Sa lactations were recorded on an experimental farm. A comparison between the native and the ‘synthetic’ genotypes was made with respect to liveweight, reproduction performance, lamb and milk production, and fat and protein yields. Performance results are also discussed in the light of nutrient requirements. FS were heavier than Sa (52 vs. 44 kg liveweight) and showed higher prolificacy and higher lamb production. The milk yield was only slightly different between genotypes: 193.7 vs. 187.7 l for FS and Sa ewes, respectively. Nevertheless, due to the lower liveweight and the related feed requirements for maintenance, Sa ewes were more profitable than FS in terms of gross income per metabolic weight (9.53 vs. 8.66 Euros per kg, respectively).

Effect of divergent selection for yearling growth rate on the maintenance feed requirements of mature Angus cows

The maintenance feed requirements of mature non-pregnant, non-lactating Angus cows from lines divergently selected for yearling growth rate, and from a control line, were determined in two experiments. In 1990, cows from each line were individually fed at 1 of 4 levels for six weeks. High-line (fast growth line) cows were 14% and 23% heavier than Control and Low-line (slow growth) cows, but required no more metabolisable energy (ME) per day to maintain constant liveweight (LW) or constant body energy. In 1992, cows were individually fed to maintain LW for six weeks. High-line cows maintained LWs 7% and 24% heavier than Control and Low-line cows but there was no difference in their average daily ME-intake. In 1990 High-line cows required only 74%, and in 1992 82%, of the ME per kg LW of Low-line cows for maintenance. About one-quarter of this difference might be expected on the basis of the difference in size. In both years, High-line cows were proportionally fatter and contained less protein per kg LW than Low-line cows. Standardising maintenance requirements for the differences in body composition of cows from the three lines removed the remaining observed differences in ME required per kg metabolic LW. On a mesuré les besoins alimentaires d'entretien de vaches adultes Angus non gestantes et non allaitantes venant de lignées sélectionnées de manieère divergente sur la vitesse de croissance des jeunes et d'une lignée témoin à trafvers deux essais. En 1990 les vaches de chaque lignée ont été alimentées individuellement pendant six semaines à l'un des quatre niveaux expérimentaux. Les vaches de la lignée haute (lignée à croissance élevée) étaient 14 et 23% plus lourdes que les vaches de la lignée témoin et de la lignée basse (croissance faible) mais n'ont pas eu besoin d'apports en énergie métabolisable (EM) plus élevés pour maintenir leur poids vif (PV) ou leur énergie corporelle. En 1992, les vaches ont été alimentées individuellement à poids vif constant pendant six semaines. Les vaches de la lignée haute ont maintenu leur poids vif à 7% et 24% au dessus de ceux des vaches des lignées basse et témoin mais il n'y a pas eu de différence dans les quantités d'énergie métabolisable ingérées. Les vaches de la lignée haute n'ont eu besoin, pour leur enteretien, que de 74% en 1991 et 82% en 1992 d'EM par kg de PV par rapport aux vaches de la lignée basse. Un quart environ de cette différence pourrait être attribué à la différence de taille. Pour les deux années, les vaches de la lignée haute ont été proportionellement plus grasses et contenaient moins de protéines par kg de PV que les vaches de la lignée basse. La prise en compte des différences dans la composition corporelle entre les vaches des trois lignées dans la détermination des besoins d'entretien as supprimé les différences observées dans l'EM nécessaire par kg de poids métabolique. In zwei Experimenten wurde der Erhaltungsbedarf von ausgewachsenen, nicht tragenden und nicht laktierenden Angus-Kühen bestimmt, die nach der Wachstumsrate bis zu einem Jahr divergent selektiert worden waren. 1990 wurden von jeder Linie Kühe individuell auf einer von vier Stufen sechs Wochen lang gefüttert. Die Kühe mit dem intensiven Wachstum (HL) waren 14% und 23% schwerer als die der Kontrollinie und die Kühe der Linie mit dem niedrigem Wachstum (LL), aber benötigten nicht mehr metabolische Energie (ME) zur Erhaltung eines konstanten Lebendgewichtes oder eines konstanten Energiegehaltes des gesamten Körpers. 1992 wurden Kühe individuell sech Wochen so gefüttert, daβ sie ihr Lebendgewicht nicht veränderten. Die HL-Kühe hatten um 7% und 24% höhere Lebendgewichte als die Kontroll- und LL-Kühe, aber es gab keine Differenz in der mittleren ta→ glichen ME-Aufnahme. 1990 benötigten die HL-Kühe nur 74% und 1992 82% der ME je kg Lebendgewicht für die Erhaltung im Vergleich zu den LL-Kühen. Nur ein Viertel der Differenz ist auf Grund der unterschiedlichen Körpergewichte zu erwarten. In beiden Jahren waren die HL-Kühe proportional fetter und benötigten weniger Protein je kg Lbenedgewicht als die LL-Kühe. Die Standardisierung des Erhaltungsbedarfes für die Differenzen in der Körperzusammensetzung der Kühe aus den drei Linien beseitigte die restliche beobachtete Differenz in ME, die je kg metabolisches Körpergewicht erforderlich ist.

Effect of divergent selection for weaning weight on liveweight and wool growth responses to feed intake in Merino ewes

During a 6-week experiment, the feed requirements for maintenance of liveweight (LW) by adult Merino ewes were measured in 2 flocks selected over 32 years for divergent weaning weight. Also examined were the net efficiency of LW gain and wool growth in response to change in feed intake, and the ability to digest dietary organic matter. Ewes selected for high weaning weight (W+) were 31% heavier than those selected for low weaning weight (W-) at the start of the experiment. To maintain LW, W+ ewes ate 24% more digestible organic matter (DOM) per day than W- ewes. There were no differences (P&gt;0.2) in the net efficiency of feed use for LW gain. The W+ ewes digested more (P&lt;0.01) dietary organic matter, by 1.8 percentage units, than W- ewes and, consequently, required only 22% more dry feed to maintain their heavier LW. Ewes from the 2 flocks did not differ (P&gt;0.4) in the amount of wool grown, and as W+ ewes were larger, they produced less (P&lt;0.01) wool per kg LW for the same DOM intake.

Feed requirements for maintenance and growth of one-year-old Angus steers selected for either fast or slow yearling growth rate

The efficiency of feed utilisation for maintenance and growth at 1 year of age was examined in 11 steers from each of 2 lines of Angus cattle selected for either fast (high line) or slow (low line) average daily gain to 1 year of age. The steers were established on a range of dietary energy intakes for 2 trials, each of 3 weeks duration. Fasted liveweights (LW) were measured at the start and end of each trial. Body fat was estimated at the end of the first trial. At the start of the experiment the high line steers were heavier (P&lt;0.001) than the low line steers (278 v. 203 kg). The high line steers required more (P&lt;0.001) feed per day [48.0 v. 39.3 MJ metabolisable energy (ME)] to maintain their greater LW but required less (P = 0.05) feed to sustain each kilogram of this LW (0.174 v. 0.192 MJ ME/kg LW) and, so, were more efficient. There was no difference in the efficiency of feed use for gain in LW (0.042 v. 0.040 kg LW/MJ ME.day). However, after adjusting feed intakes for the different mature sizes (A) of the 2 lines, there was no difference in the biological efficiency of feed use for either maintenance (0.369 v. 0.359 MJ ME/kg A0.73) or gain (5.45 v. 4.37 kg LW/MJ ME.kg A0.73). These results suggest that divergent selection for growth rate in this study has produced different-sized animals whose ability to convert feed to gain in LW has not been altered.

BREEDING FOR FEED EFFICIENCY: POULTRY

In egg-type poultry, variation in egg mass, body weight and change in body weight account for about 50–70% of the variation in feed consumed. In meat-type poultry, about 40% of the variation in feed consumption is attributable to variation in change of body weight (gain), and body weight itself. Past selection, primarily for egg numbers and egg size (egg mass) in egg stocks and for gain in meat stocks, has resulted in a correlated improvement in feed efficiency. Heterosis from breed or strain crosses contributes an average of 6% to improvement of feed efficiency in both egg and meat stocks. The success of direct selection for feed efficiency depends upon variation in feed consumption not attributable to economic traits in present poultry selection programs. There is evidence that such variation exists which could be successfully exploited in poultry. In egg stocks, the evidence is mainly from studies of variation within and between strains. In meat stocks, there is evidence from uni-trait selection studies as well as studies of within and between strain variation. The degree to which such selection would be successful in a multi-trait selection program and the economic viability of such success as compared to alternatives needs to be determined. Improvement of feed efficiency is possible by reducing feed requirements for maintenance and activity, by reducing behaviors causing feed wastage, or by reducing body fat to require less feed energy per unit gain. Feed wastage can be reduced by management techniques. Thus, the exploitation of feed-wasting behavior is not presently necessary. The best prospects are those associated with maintenance energy requirements in both egg and meat stocks of poultry, and the reduction of body fat in meat stocks. It is improbable that the opportunities for breeding to improve feed efficiency have been exhausted, much less identified. Key words: Breeding, feed efficiency, poultry, selection

Feed Requirements for Maintenance and Gain in Crossbred Bulls of Two Types

Growth rate and individual feed consumption of 24 Jersey × Angus (J × A) and 22 Simmental × Angus (S × A) bulls were used to compare requirements for maintenance and gain during the postweaning growth period. The 82% concentrate diet contained 3.4 Meal digestible energy (DE)/kg. Periods I and II were each 84 d long for J × A and 112 d for S × A. Bulls were fed either 1.2, 1.7 or 2.2 times their estimated feed requirement for maintenance during periods I and II and full fed to slaughter during period III. After period I, the bulls from each feed level were further subdivided for the three feed levels for period II. Bulls averaged 242 d of age and weighed 221 and 240 kg at the start of period I for J × A and S × A, respectively. Averaged over periods I and II average daily gains (ADG) were .14, .66 and 1.09 kg/d for 1.2, 1.7 and 2.2 feed levels, respectively, for J × A and .26, .84 and 1.26 kg/d, respectively, for S × A. No compensatory gains were observed among bulls moved from low intakes in period I to higher intakes in period II. Weight (W) and ADG were related (P<.01) to DE, Mcal/d in period I, while W, ADG and the interaction breed-cross (B) × ADG were related (P<.01) to DE in period II. The B × W interaction effects were very small and nonsignificant in both periods. Multiple regression equations for period I were DE = 2.319 + .028 W + 10.773 ADG for J × A and DE = −1.324 + .039 W + 11.270 ADG for S × A. In period II DE = .132 + .039 W + 9.013 ADG for J × A and DE = −.787 + .033 W + 11.588 ADG S × A. Thus, at average W and ADG, DE requirements for J × A and S × A differed in both periods I and II, but maintenance requirements based on W were the same. The J × A required less feed for gain than S × A in both periods I (Pì.10) and II (ì.01).

Gravity as a factor in the animal environment.

Review of current knowledge, research, and research planning on the influence of gravity upon living organisms. Discussed factors affecting the adaptability of animals to increased acceleration fields include age, sex, posture, and body size. Affected functions and aspects reviewed cover growth and mature body size, body composition, maintenance feed requirements, and feed utilization efficiency. It is expected that research involving the exposure of animals to altered gravity states will lead to new biological concepts of very broad importance.

High-moisture silage from mixed pasture herbage as a feed for lactating dairy cows

Abstract Silages made from direct-cut pasture herbage ensiled in stacks (i), bunkers (ii), and by vacuum compression (iii) have been evaluated as sole feedstuffs for milking cows in two series of experiments. Total nitrogen, ammonia-nitrogen, and pH were highest in (i), from which significantly more dry matter (D.M.) was consumed, and more milk of significantly higher fat percentage was produced, than from (ii) or (iii)|but these differences were too small to influence appreciably choice of the method of ensiling. Voluntary intakes of silage D.M. ranged between 2.2 and 3.0% of live weight. Feed requirements for maintenance and lactation have been calculated and are discussed relative to others previously obtained for pasture herbage.

Effect of environment on the maintenance requirements of Merino wethers

Small groups of Merino wethers were maintained at virtually constant liveweight in four "environments" and their maintenance feed requirements estimated from the relationship between their fluctuations in liveweight over 14-day periods and their feed intakes, measured directly or estimated by chromium oxide dilution and faecal nitrogen concentration. When adult wethers of equal size but a varying degree of fatness were fed on fresh pasture herbage in metabolism pens, liveweights of 26, 32, and 46 kg could be maintained on a daily intake of approximately 200, 300, and 420 g digestible organic matter (D.O.M.) respectively. When the metabolism pens were placed outdoors in winter the maintenance requirements rose, the rise appearing to be greatest for the thin sheep. When wethers were allowed to graze for about 1½ , 2½, and 4 hr in abundant pasture, liveweights of 26, 33, and 46 kg were maintained on intakes of approximately 420, 480, and 490 g D.O.M. respectively. When the same wethers were allowed to graze freely and weight was controlled by the scarcity or abundance of the pasturage, the same liveweights were maintained on intakes of about 750, 780, and 560 g D.O.M. respectively. The rise in maintenance requirements on short pasture seems too great to be explained by the increased energy cost of locomotion and grazing. The possibility of an endocrine stimulation of metabolic rate is pointed out.

Efficiency of Feed Utilization in Relation to Body Weight and Egg Production

Titus (1928–29) has estimated that to produce a standard-weight egg, 40 grams of feed were required over and above that needed for maintenance, and in 1934 estimated that not less than 75 per cent of the total feed consumed by laying hens is used for body maintenance (Titus, 1934). Byerly (1941) calculated that the annual feed requirements for maintenance varies from 46.8 pounds for three-pound birds to 81.4 pounds for seven-pound birds and that for each standard-weight egg, 64.4 grams of feed were required over and above that needed for maintenance.Interesting observations were made by Bird and Sinclair (1939) on the energy required for maintenance, egg production, and changes in body weight of females kept in laying cages. A partial correlation coefficient revealed that the amount of ingested feed is positively and significantly correlated with body size, weight of egg material produced, and changes in body weight. They showed .