HOMEORETSKA REGULACUJA METABOLIČKIH FUNKCIJA KOD KRAVA U PERIPARTALNOM PERIODU

The aim of this paper is to describe complex homeoretic and homeostatic mechanisms in dairy cows during the peripartum period. The endocrine system has a key function in regulating the adaptation of metabolism during the peripartum period. Homeoresis represents the functioning of the endocrine system and metabolism in conditions when the organism must primarily provide certain physiological processes, such as fetal growth or lactation. Then the function of all tissues is adjusted to the new situation. Homeoretic hormones (growth hormone, prolactin, glucocorticosteroids, thyroid hormones, insulin, glucagon and leptin) in dairy cows in the peripartum period play a key role in maintaining high lactation and maintaining cow health.

HEREDITY AND REPEATABILITY OF SIGNS OF DAIRY PRODUCTIVITY OF MARES NOVOALEXANDROVSKY DRAFT BREED

When implementing the same group genetic information, repeatability occurs. With sufficient repeatability, the feature becomes effective and selection for that feature at an early age or under any conditions. In the article considered and analyzed the high lactation of seventeen pairs "mother-daughter" mares Novoaleksandrovsky draft breed. The repeatability factor (rw) was within 0.65... 0.68. The repeatability of the milk yield ranged from 0.04 to 0.69 in mothers; in daughters from 0.02 to 0.66. In mother-daughter pairs by milk yield and lactation: relatively high coefficient of heredity (h2 = 0.74) and high coefficient of repeatability (rw = 0.91). Taking into account the established coefficients of heredity and repeatability, the productivity of stud of the Novoaleksandrovsky draft breed of the studied population is largely due to genetic factors, makes it effective to select animals according to their own productivity.

Effect of feeding supplemental fat or lysine during the postweaning period on the reproductive performance of sows with low or high lactation body weight and fat losses

The effects of feeding supplemental fat or lysine during the postweaning period on breeding and subsequent reproductive performance were determined in two experiments of a 2 × 3 factorial design, using 168 Landrace × Yorkshire first-parity (exp. 1) and 180 Yorkshire second-parity (exp. 2) sows. At the end of lactation, they were divided into two groups: LWL (< 14 kg) and HWL (> 14 kg) based on 3 wk lactation weight loss. The three experimental diets fed during the postweaning period were: (1) control; a 12% gestation diet fed 2 kg d−1 (24.7 MJ DE, 9.4 g lysine d−1); (2) Fat; control diet plus animal fat to provide approximately 50% more daily energy intake (37.0 MJ DE d−1); and (3) Lysine; control diet plus lysine to provide approximately 50% more daily lysine intake (14.4 g d−1). After breeding, all sows were fed the control diet at 2 kg d−1, and they were killed at 30 d of gestation to evaluate their reproductive performance. High weight loss during the lactation period increased the incidence of anestrus and reduced the pregnancy rate in first-parity sows. Feeding supplemental fat was beneficial in increasing the proportion of sows in estrus within 7 d postweaning and the pregnancy rates of first-parity sows with high lactation weight loss. Supplemental fat also had a beneficial effect on ovulation rate, the number of normal embryos, fetal survival and the fetal weights, whereas supplemental lysine improved only fetal weights. Feeding supplemental fat or lysine improved only ovulation rate in second-parity sows with high lactation weight loss. The results indicated that feeding supplemental fat or lysine can improve the postweaning reproductive performance of sows that had high weight and fat losses during lactation. Key words: Sows, estrus, ovulation, embryo survival, fat, lysine

PROPYLENE GLYCOL AND GLYCEROL AS A FEED ADDITIVE FOR LACTATING DAIRY COWS: AN EVALUATION OF BLOOD METABOLITE PARAMETERS

An extensive trial for testing the antiketogenic potency of glycerol and propylene glycol (DL-1,2 propanediol) was conducted with milking Holsteins and Ayrshires over a 2-yr period. Through weekly blood analyses of free fatty acids, glucose, β-hydroxybutyrate, and acetoacetate for an 8-wk period post-partum, it was possible to classify these cows as normal, clinically ketotic, and subclinically ketotic. The results showed that in cows that were not stressed by either high lactation yield or low concentrate intake these chemical additives only slightly depressed blood ketones and free fatty acids below control values. The beneficial properties of these additives became obvious in cows stressed by adverse environmental factors and slightly reduced levels of concentrate intake. In these cows, the addition of propylene glycol to the concentrate ration significantly reduced blood ketones and plasma free fatty acids and increased the concentration of blood glucose. It was concluded that the use of propylene glycol as a feed additive (3 and 6% of the concentrate) should be economically attractive in high-producing dairy herds because it will significantly decrease the incidence of clinical and subclinical ketosis in cows during the immediate postpartum period (4–8 wk) when they are most susceptible to the metabolic disorder.

Lactose in the blood and urine of cows

SummaryLactose could not be detected in the urine of non-lactating cows but was invariably found, though usually in low concentration, in the urine of lactating cows; the highest values were observed with cows of high lactation number. Towards the end of an extended milking interval of 39 h, the lactose concentration in the blood and the excretion of lactose in urine increased markedly, but on milking there was a rapid return to original values. Lactosuria was observed in pregnant cows from about 20 days before parturition, and at parturition there was a temporary, marked increase in the excretion of lactose in urine.

724. Levels of feeding of concentrates for dairy heifers before and after calving

1. Two levels of steaming-up and two levels of concentrates feeding during the first 84 days of lactation have been compared in a 2 x 2 factorial experiment over three winter seasons, using fifty-two Shorthorn and thirty-six Friesian heifers. The levels of steaming up were 2 cwt. and ½ cwt. of concentrates fed over the last 21 and 14 days of pregnancy, respectively. The levels of concentrates during lactation were 5 and 3 lb. per 10 lb. milk per day. Roughages were fed for maintenance. After the 84th day of lactation all animals were given the same treatment for the remainder of the lactation. Milk yield, milk composition and live weight were measured throughout the lactation.2. The treatments were annotated as HH, HL, LH and LL, the first letter indicating level of steaming-up and the second the level of concentrates feeding in the first 12 weeks of lactation.3. Mean milk yields were as follows:4. The LH treatment reqiuird 3 cwt. more concentrates than HL to produce the same amount of milk.5. The response to additioal concentrates on the LH treatment after calving was l lb. additional milk per l lb. additional starch equivalent.6. Butterfat percentages were higher (3·69%) in both groups on low-lactation feeding than in the two groups on high-lactation feeding (3·43%). The HL group (i.e. the group that received high steaming-up and low-lactation feeding) combined high milk yield with a higher butterfat percentage, and at current milk and feedingstuff prices and under the conditions of the trials, this group showed a greater cash return than the groups on the other three treatments.